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  • 51.
    Guo, Xiaolei
    et al.
    aFaculty of Material Science and Engineering, Nanjing Forestry University, Nanjing.
    Zhaolong, Zhu
    aFaculty of Material Science and Engineering, Nanjing Forestry University, Nanjing.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Xu, Bao
    aFaculty of Material Science and Engineering, Nanjing Forestry University, Nanjing.
    Pingxiang, Cao
    aFaculty of Material Science and Engineering, Nanjing Forestry University, Nanjing.
    The cutting performance of Al2O3 and Si3N4 ceramic cutting tools in the milling plywood2018In: Advances in Applied Ceramics: Structural, Functional and Bioceramics, ISSN 1743-6753, E-ISSN 1743-6761, Vol. 117, no 1, p. 16-22Article in journal (Refereed)
    Abstract [en]

    This research focuses on the cutting performance of Al2O3 and Si3N4 ceramic cutting tools in upmillingplywood, the results of which are as follows. First, whether the tool material is Al2O3 orSi3N4 ceramic, the cutting forces at low-speed cutting were less than those at high-speedcutting, and the machining quality at low-speed cutting was greater than that at high-speedcutting. Then, whether at low- or high-speed cutting, the cutting forces of Al2O3 cutting toolswere higher than those of Si3N4 cutting tools, and the machining quality of plywood milledby Al2O3 ceramic cutting tools was poorer than that milled by Si3N4 ceramic cutting tools.Finally, Si3N4 ceramic cutting tools were more suitable to machine the wooden productionswith much glue content than Al2O3 ceramic cutting tools for the better machined quality.

  • 52.
    Huang, Liangliang
    et al.
    Nanjing Forestry University, Faculty of Material Science and Engineering, Nanjing.
    Wang, Huiyun
    Nanjing Forestry University, Faculty of Material Science and Engineering, Nanjing.
    Guo, Xiaolei
    Nanjing Forestry University, Faculty of Material Science and Engineering, Nanjing.
    Jiang, Zhihua
    Power Dekor Group Co., Ltd., Danyang, Jiangsu.
    Xing, Feng
    Power Dekor Group Co., Ltd., Danyang, Jiangsu.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Study on continuous cold-pressing technology of engineered wood flooring with EPI adhesive2018In: Wood research, ISSN 1336-4561, Vol. 63, no 2, p. 335-342Article in journal (Refereed)
    Abstract [en]

    The effects of process parameters (adhesive spread, press time, and applied pressure) on the gluing performance of engineered wood flooring bonded with emulsion-polymer-isocyanate (EPI) adhesive were studied. The results showed (shear strength and aging test) that the major factors were adhesive spread and press time. The optimized parameters for best gluing performance of engineered wood flooring were 160 g.m-2, 14 s, and 60 s for adhesive spread, heat time, and press time, respectively, within certain ranges

  • 53.
    Huber, Johannes Albert Josef
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Berg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Assessment of Connections In Cross-Laminated Timberbuildings Regarding Structural Robustness2018Conference paper (Refereed)
    Abstract [en]

    Cross-laminated timber makes timber buildings with an increasing number of storeys achievable. Withmore storeys, structural robustness needs more attention to make a building survive unforeseen events (e.g. accidents,terrorism) and save lives. For steel and concrete buildings, design methods for robustness focus on connection details.The assessment of joints in cross-laminated timber buildings regarding robustness is rather limited in the literature. Theobjective of this paper is to conduct an initial assessment of the connectors after the removal of a wall in a platformcross-laminated timber building. We used the finite element method and the component method for the analysis of acase building. The results indicate that the wall-to-wall and the floor-to-floor connectors may fail at low deflectionlevels leading to high shear loads in the floor panel above the removed wall, which might induce cracking. The removalanalysis was only partially completed, but we identified an indication of the deformation behaviour of the case building.Testing and refined modelling of the connections is needed in the future to verify the results. This study may facilitatefuture investigations regarding robustness of multi-storey cross-laminated timber buildings.

  • 54.
    Huber, Johannes Albert Josef
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Review of Robustness in Timber Buildings2017Conference paper (Refereed)
    Abstract [en]

    Timber buildings today aim for taller and larger dimensions to accommodate increased numbers of occupants.  In tall buildings, more human lives are at risk if large portions of the structure collapse progressively during catastrophic failure events. To safeguard timber structures from disproportionate collapse due to localised failures, the aspect of robustness in particular needs to be considered. In the literature about building structures the term robustness seems to be contemplated in diverse ways. Several possible approaches to define and analyse this property can be found. However, certain consensus as to what characterises a robust structure seems to exist. A review of the concept of robustness for building structures in general and timber structures in specific is presented in this paper. Certain commonly applied terminology and definitions in the context of robustness are analysed. In the literature, risk-based, reliability-based and performance-based concepts for robustness appear to be established. The first two concepts are briefly summarised. The performance-based concept is treated in greater detail to highlight different procedures of deterministic robustness analyses. Common general characteristics of robust buildings which seem to be agreed upon are summarised. Robustness provisions for timber buildings in specific are described and compared to provisions in other building materials such as steel and concrete. The development of alternate load paths during local failure seems to play an essential role in preventing progressive collapse in buildings. The literature about robustness seems to be comprehensive concerning general considerations and concerning structures built in concrete or steel but appears to be rather limited in regards to timber structures. Evaluations of robustness in timber structures seem to be focused on risk-based and reliability-based concepts in literature.

  • 55.
    Huber, Johannes Albert Josef
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Berg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    A Review of Structural Robustness with Focus on Timber Buildings2018In: 40th IABSE Symposium: Tomorrow’s Megastructures, International Association for Bridge and Structural Engineering (IABSE) , 2018, article id S32-17Conference paper (Refereed)
    Abstract [en]

    With an increasing number of storeys, timber buildings require closer attention to structuralrobustness. If a building can survive unforeseen events (e.g. accidents, terrorism), lives can be saved.The literature appears to be rather limited concerning robustness of timber buildings. This paperaims to give a brief review on robustness in general and design guidelines for timber in specific. Theresults indicate that connection design is a key aspect for robustness. Like in seismic design, by usingthe ductile capacity of connectors, the brittleness of timber can be controlled. For light timber-framebuildings, more guidelines exist than for posts and beams and cross-laminated timber, which bothseem to be similar to steel frames and precast concrete respectively regarding robustness.

  • 56.
    Huber, Johannes Albert Josef
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Berg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Finite element analysis of alternative load paths in a platform-framed CLT building2020In: Proceedings of the Institution of Civil Engineers: Structures and buildings, ISSN 0965-0911, E-ISSN 1751-7702Article in journal (Refereed)
    Abstract [en]

    Multi-storey cross-laminated timber (CLT) buildings are a comparatively recent construction type. Knowledge concerning the performance of CLT buildings regarding the prevention of disproportionate collapse after unforeseeable events (e.g. accidents or acts of terrorism) is not as refined as that for concrete and steel buildings. In particular, alternative load paths (ALPs) after the removal of a wall panel in platform-framed variants have not yet been studied in detail. The goal of this work was therefore to study ALPs in CLT buildings. An eight-storey bay of an existing building was evaluated by conducting a non-linear static pushdown analysis in a finite element analysis on three representative storeys. The analyses accounted for single fastener behaviour, timber crushing, friction, brittle failure and large deformations. The force–deformation behaviours elicited under the pushdown analyses were subsequently inserted in a simplified dynamic model to evaluate the transient response of the entire bay. Four ALPs were identified in this case – shear resistance in the floor panels, arching action of the walls, catenary action in the floor panels and hanging action from the roof. The dynamic analysis did not show a collapse, unless the inter-compartment stiffness was significantly reduced. The resistance mechanisms are described in this paper, which may provide information for improved building design.

  • 57.
    Huber, Johannes Albert Josef
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Berg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials. Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Simulation of Alternative Load Paths After a Wall Removal in a Platform-Framed Cross-Laminated Timber Building2019In: CompWood 2019 Book of Abstracts / [ed] Tomas K. Bader, Josef Füssl, Anders Olsson, 2019Conference paper (Refereed)
    Abstract [en]

    An increasing number of multi-storey timber buildings use cross-laminated timber (CLT) for their bearing structure. Platform-framed CLT buildings consist of vertical repetitions of floors resting upon one-storey tall walls, squeezing-in the floor panels between the walls. Tall buildings need to be structurally robust because many lives would be at stake in case of a disproportionate collapse. Robustness is the ability of a system to survive the loss of components. For collapse resistance, it poses the last line of defence, after an unforeseen exposure (e.g. accident, terrorism) has already occurred and after the exposed components could not resist failure. A robust building offers alternative load paths (ALPs) which come into action when a part of the bearing structure has been removed [1].

    Many alternative load path analyses (ALPA) have been conducted for tall concrete and steel buildings using the finite element method (FEM), but for timber, ALPA are still scarce. ALPs depend on the behaviour of the connections after a loss [1]. Studies on timber so far have accounted for connections in a simplified manner by lumping their aggregate behaviour into single points. Our goal is to elicit the ALPs after a wall removal in a platform-framed CLT building, study their development and quantify their capacity, to determine whether they can prevent a collapse.

    We investigated a corner bay of an 8-storey platform-framed CLT building (see Figure 1) and removed a wall at the bottom storey. We studied the ALPs of each storey by pushing down the walls above the gap in a non-linear quasi-static analysis in the FE software Abaqus. We accounted for contact and friction, considered plastic timber crushing, and accounted for brittle cracking in the panels. We modelled single fasteners with connector elements which simulated the elastic, plastic, damage and rupture behaviour. We recorded the force-displacement curves, i.e. pushdown curves, for each storey and used them to conduct a dynamic analysis of the entire bay in a simplified model, as suggested by [2].

    The results show that the structure could engage the following ALPs after a wall removal: I) arching action in the outer floor panels, II) arching action of the walls, III) quasi-catenary action in the floor panels, and IV) hanging action from the roof panels. The ALPs were limited by various parameters, but they sufficed to resist a collapse of the bay. We observed that the inter-storey stiffness influenced the load-sharing among storeys, which affected the structural robustness. In the compressed connections, friction, and not the fasteners, transferred most of the horizontal loads. Future research should test the squeezed-in platform joint experimentally, to quantify its capacity for transverse shear loads. We also advise to assess the inter-storey stiffness to estimate the capacity for load-sharing among storeys.

  • 58.
    Huber, Johannes Albert Josef
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Berg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Structural robustness and timber buildings: a review2019In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 14, no 2, p. 107-128Article in journal (Refereed)
    Abstract [en]

    Timber buildings are increasing in their dimensions. Structural robustness is imperative for all buildings and specifically important for tall buildings. Lives can be saved if disproportionate collapse can be avoided after a catastrophic event (e.g. accident, terrorism). The literature about robustness is comprehensive concerning concrete and steel buildings, but is rather limited regarding timber. This paper reviews robustness in general and robustness of timber buildings in particular. Robustness is an intrinsic structural property, enhancing global tolerance to local failures, regardless of the cause. A deterministic approach to assess robustness is to remove certain load-bearing elements from the structure and compare the consequences to given limits. Design methods for robustness may be direct by assessing effects of local failure, or indirect by following guidelines. For robust timber buildings, the connections are the key aspects. Usually, metal connectors may provide the required joint ductility. For robust light timber-frame construction, rim beams may be designed. For timber posts and beams and cross laminated timber, guidance regarding robustness is scarce, but in some aspects they seem to be similar to steel frames and precast concrete. Future research should assess the capacity of connections, and evaluate the adequacy of seismic connectors for robust timber buildings.

  • 59.
    Huber, Johannes Albert Josef
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Berg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Structural Robustness of Timber Buildings2018Conference paper (Refereed)
    Abstract [en]

    The number of storeys in timber buildings are increasing. With more storeys, structural robustness needsmore attention, to make a building survive unforeseen events (e.g. accidents, terrorism) and save lives. The state of theart regarding robustness of concrete and steel buildings seems to be rather refined, but for timber buildings, theliterature appears to be quite limited. This study aims to review the design methods for robustness of timber buildings.First, the terminology and definitions are introduced. Then, the state of the art for design methods for robustness ingeneral are presented. Finally, the design methods for timber buildings are discussed and compared to those from otherbuilding materials. The results indicate that the guidelines for light timber-frame buildings are more refined than thosefor post and beam and cross-laminated timber buildings. Regarding robustness, the latter two construction types exhibitcertain similarities to steel frames and precast concrete buildings respectively. For timber, ductile connections can beused to avoid brittle timber failure after local damages, which resembles the approach of seismic design. Future researchin robustness should focus on the connection details in multi-storey timber buildings.

  • 60.
    Kováciková, Janka
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ivankova, Olga
    Slovak University of Technology in Bratislava.
    Berg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Finite element analysis of timber beams with flaws2016In: ECCOMAS Congress 2016: Proceedings of the 7th European Congress on Computational Methods in Applied Sciences and Engineering / [ed] M. Papadrakakis; V. Papadopoulos; G. Stefanou; V. Plevris, Athens: National Technical University of Athens , 2016, Vol. 4, p. 8606-8611Conference paper (Refereed)
    Abstract [en]

    The work was focused on modelling of cracks and simulations of their propagationin timber beams. The aim was to find out the influence of flaws on load-carrying capacity. Inbeam design and beam inspection, it is necessary to determine the load-carrying capacity of abeam with flaws. There is not much information in literature about the influence of flaws onbending and shear strength of timber beams. Standards for fracture mechanics design approachfor timber structures are not easily available.The results from simulations of loaded timber beams with flaws are discussed in this paper.Two different types of timber beams were analysed. First type was a sawn timber beam andfor that four different models were analysed: first model was a beam without flaw; secondmodel was a beam with a straight central flaw; next was a beam with an oblique crack andfourth beam had a round hole in the middle of the span. Second type of beam was a gluedlaminated timber beam (glulam). For this type, five different models were analysed. First fourvariants were the same as for the solid timber beam and the fifth variant had an initial crackalong a glue line. We analysed these types of flaws, since they are the most common flaws inwood.Simulations were conducted in ABAQUS. Material properties of wood used in the modelswere retrieved from standards; C24 for solid timber and GL24c for glulam timber beams.Dimensions of beams were the same for all variants and beams were considered simply supported.For an analysis of crack propagation, linear elastic fracture mechanics was considered.Modelling fracture was conducted using the extended finite element method (XFEM).The energy approach was used for the analysis of crack propagation. Comparing results forsolid and glulam beams with and without cracks gave us an overview how different flaws influenceload-carrying capacity of the beams and under which loading failure occurs. Simulatingtimber beams is more complicated compering to steel or plastic. By understanding how tosimulate flaws in wood material it is possible to obtain reliable results with finite elementanalysis

  • 61. Lhate, Imacio
    et al.
    Cristovao, Luis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sitoe, Rui
    Cutting forces for wood of lesser used species from Mozambique2011In: Proceedings of the 20th International Wood Machining Seminar, Skellefteå, 2011, p. 444-451Conference paper (Refereed)
  • 62.
    Lhate, Inacio
    et al.
    Eduardo Mondlane University.
    Cristovao, Luis
    Eduardo Mondlane University.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Machining properties of lesser used wood species from Mozambique2017In: Wood research, ISSN 1336-4561, Vol. 62, no 4, p. 635-644Article in journal (Refereed)
    Abstract [en]

    The present study was aiming at measuring cutting forces for wood of lesser used species from Mozambique such as Acacia nigrescens Oliv (namuno), Pericopsis angolensis Meeweven (muanga), Pseudolachnostylis maprounaefolia Pax (ntholo) and Sterculia appendiculata K. Schum (metil). Another aim was to use an expeditious method to compare performance of the species when cut. A machinability index calculated using Digraph and Matrix Methods was used for ranking the performance of the species when cut. Two different cutting tools 20o and 30o rake angle were used. Main cutting force in 90°-90° and 90°-0°cutting directions were measured by piezoelectric gauge. The results of the experiments showed that cutting forces followed normal trends to increase with density and decrease with increasing rake angle. The ratio between wood density and cutting forces in cutting directions 90°-90° and 90°-0° were 7 s2m-4 and 17.3 s2m-4, respectively. The most difficult species to be machined was Namuno, whereas the easiest species to be machined was Metil.

  • 63.
    Li, Rongrong
    et al.
    Nanjing Forestry University, College of Material Science and Engineering.
    Cao, Pingxiang
    Nanjing Forestry University, College of Material Science and Engineering.
    Guo, Xiaolei
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Futang, Ji
    Nanjing Forestry University, College of Material Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wang, Xiaodong (Alice)
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    A Novel Sawing Method for Small-Diameter Log2015In: Wood research, ISSN 1336-4561, Vol. 60, no 2, p. 293-300Article in journal (Refereed)
    Abstract [en]

    The commercial feasibility of sawmilling mainly depends on the expected productionyield. At the same time, the choice of sawing method is one of primary factors affecting yield.Therefore, choosing a reasonable sawing method is also necessary in small-diameter logs sawingprocess. In this study, a novel sawing method was proposed, and a comparison was made betweenthe volume yield for the most common sawing method in China, and the yield produced by anovel sawing method. This study shows that hexagon sawing give higher yield than the othersawing methods. The mean yield for the whole diameter range is: 82.7 % for hexagon sawing,53.3 % for live sawing, 56.7 % for hexagon sawing, 63.2 % for hexagon sawing.

  • 64.
    Li, Rongrong
    et al.
    Nanjing Forestry University, College of Furnitures & Industrial Design, Nanjing.
    Cao, Pingxiang
    Nanjing Forestry University, College of Material Science & Engineering, Nanjing.
    Xu, Wei
    Nanjing Forestry University, College of Furnitures & Industrial Design, Nanjing.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wang, Alice
    Department of Wood and Forest Sciences, Laval University.
    Experimental and Numerical Study of Moisture-induced Stress Formation in Hexagonal Glulam Using X-ray Computed Tomography and Finite-element Analysis2018In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 13, no 4, p. 7395-7403Article in journal (Refereed)
    Abstract [en]

    Hexagonal glue-laminated timber with large cross-sections, made from small diameter logs, was studied. Effects of relative humidity variations on the moisture-induced stresses were investigated to evaluate how the prediction model compared to a real outcome. The test samples were exposed to an environment with relative humidity variations from 80% to 30%. The moisture content inside the samples was measured via X-ray computed tomography scanning. A moisture transport and a hygromechanical finite element simulation model was used for the prediction of moisture content and resulting stress distribution. The results from both the test and simulation showed that the moisture content in the edge angles of the samples dropped rapidly due to a large moisture diffusion rate. The moisture gradient was generated via a different moisture transfer rate at the inner and external parts of the samples. The maximum stress perpendicular to the grain in the simulation was 8 MPa and was located at the surface near the corners. This stress peak caused cracking according to the model, which was also seen in the test samples. The results for the measured moisture content agreed with the simulated results and this indicated that the moisture transfer model was adequate for simulation.

  • 65.
    Li, Rongrong
    et al.
    College of Furnishings and Industrial Design, Nanjing Forestry University, Nanjing, China.
    Cao, Pingxiang
    Faculty of Material Science and Engineering, Nanjing Forestry University, Nanjing, China.
    Zhang, Shuangbao
    Department of Material Science and Technology, Beijing Forestry University, Beijing, China.
    Xu, Wei
    College of Furnishings and Industrial Design, Nanjing Forestry University, Nanjing, China.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Guo, Xiaolei
    Faculty of Material Science and Engineering, Nanjing Forestry University, Nanjing, China.
    Prediction of cutting force during gypsum fiber composite milling process using response surface methodology2017In: Wood and Fiber Science, ISSN 0735-6161, Vol. 49, no 4, p. 453-460Article in journal (Refereed)
    Abstract [en]

    Gypsum fiber composite (GFC) is a kind of building material widely used in interior decoration. Milling is the most commonly used machining process for GFC. Cutting force as an important cutting characteristic parameter has significant influence on the quality of machined surface, power consumption, and tools wear. The tangential force (Fx) and normal force (Fy) were measured and analyzed to find out the effects of milling parameters on these cutting forces. Milling parameters considered were spindle speed, feed rate, and depth of cut. The response surface methodology (RSM) was selected to develop mathematical models and optimize milling parameters. The results showed that with the increase of feed rate and depth of cut, the Fx and Fy increased. But the cutting forces decreased with the increase of spindle speed. The optimization results indicated that high spindle speed, low feed rate, and small depth of cut are preferable for milling of GFC to obtain the best result.

  • 66.
    Li, Rongrong
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Nanjing Forestry University.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Guo, Xiaolei
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Nanjing Forestry University.
    Cao, Pingxiang
    Nanjing Forestry University.
    Wang, Jie
    Nanjing Forestry University.
    Chen, Qingqing
    Nanjing Forestry University.
    Xue, Hong
    Nanjing Forestry University.
    Pressure, Feed Rate, and Abrasive Mass Flow Rate Influence on Surface Roughness for Recombinant Bamboo Abrasive Water Jet Cutting2015In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, no 2, p. 1998-2008Article in journal (Refereed)
    Abstract [en]

    The effects of pressure, feed rate, and abrasive mass flow rate on surface roughness were investigated during abrasive water cutting of recombinant bamboo. Two different thicknesses (10 mm and 15 mm) of recombinant bamboo were cut in the longitudinal and transversal directions by abrasive water jet. All experiments were arranged using response surface methodology. The parameter Ra was selected to represent the surface roughness. The value of Ra increased with an increase in feed rate and abrasive mass flow rate, but decreased with an increase in pressure. The surface roughness was lower when cutting the fiber longitudinally than when cutting transversally.

  • 67.
    Li, Rongrong
    et al.
    Nanjing Forestry University.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Guo, Xiaolei
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Nanjing Forestry University.
    Ding, Jianwen
    Nanjing Forestry University.
    Cao, Pingxiang
    Nanjing Forestry University.
    Effect of Pressure, Feed Rate, and Abrasive Mass Flow Rate on Water Jet Cutting Efficiency When Cutting Recombinant Bamboo2015In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, no 1, p. 499-509Article in journal (Refereed)
    Abstract [en]

    Recombinant bamboo with a thickness of 15 mm was drilled on a CNC machine. The process parameters considered were spindle speed, feed rate, and diameter of the drill, and the response parameters were thrust force and torque. Mathematical models were developed to establish the relationship between the process parameters and the response parameters. The results showed that the main influence on thrust force came from spindle speed and feed rate. High spindle speed with low feed rate was a combination that minimized the thrust force. The process parameters that have a major effect on torque are the diameter of the drill and the spindle speed.

  • 68.
    Li, Rongrong
    et al.
    Nanjing Forestry University.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wang, Jie
    Nanjing Forestry University.
    Guo, Xiaolei
    Nanjing Forestry University.
    Cao, Pingxiang
    Nanjing Forestry University.
    Testing and Modeling of Thrust Force and Torque in Drilling Recombinant Bamboo2014In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 9, no 4, p. 7326-7335Article in journal (Refereed)
  • 69.
    Li, Rongrong
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Guo, Xiaolei
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Marklund, Birger
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cao, Pingxiang
    Faculty of Material Science and Engineering. Nanjing Forestry University.
    Investigation of Glueline Shear Strength of Pine Wood Bonded with PVAc by Response Surface Methodology2015In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, no 3, p. 3831-3838Article in journal (Refereed)
  • 70.
    Li, Rongrong
    et al.
    Nanjing Forestry University, College of Furnitures & Industrial Design, Nanjing.
    Xu, Wei
    Nanjing Forestry University, College of Furnitures & Industrial Design, Nanjing.
    Lu, Fang
    Nanjing Forestry University, College of Furnitures & Industrial Design, Nanjing.
    Cao, Pingxiang
    Nanjing Forestry University, College of Material Science & Engineering, Nanjing.
    Guo, Xiaolei
    Nanjing Forestry University, Faculty of Material Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Non-standard test method for glue line shear strength2017In: Wood research, ISSN 1336-4561, Vol. 62, no 5, p. 825-830Article in journal (Refereed)
    Abstract [en]

    The relevant standards for glueline shear strength testing were summarized and analyzed in this paper. Depending on these existing test standards, the resulting stress in glueline is not pure shear stress, but a combination of shear and normal stresses. In order to overcome this deficiency, a symmetrical structure was proposed for making samples. Some comparative testing was accomplished by using these symmetrical samples, the results showed that the normal stress could be avoided during testing. These results were also confirmed by finite element method (FEM), the simulation results showed that the shear stress in glueline was uniform

  • 71. Lundgren, Nils
    et al.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Flodin, Jens
    Choosing green sawing dimensions for Norway spruce from stochastic simulations2011In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 57, no 2, p. 94-99Article in journal (Refereed)
    Abstract [en]

    The high accuracy of log positioning and the stability of saw blades in breakdown machinery in modern sawmills have reduced the need to add margins for sawing variations. Oversize green sawing dimensions are still needed, but mainly to allow for drying shrinkage. This has put a new focus on better adapting green sawing dimensions to the shrinkage behavior of wood. In this study, a method for optimization of green sawing dimensions using stochastic simulation is presented. Normal distributions were generated for planed dry dimensions, kerf width, and target moisture content. The minimum share of boards exceeding the specified dry dimensions was decided, and deformations in boards from all positions in the cross section in a number of logs were simulated. The simulated shrinkage allowance from stochastic simulations was compared to experimental results from an industry test and to finite element results based on material data for Norway spruce. The results showed that the green width of the sawn boards should increase when the number of boards in the center yield increases. The green thickness of boards should be thinner for center boards and outer boards than for inner boards

  • 72.
    Marklund, Birger
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Influence of Tool Geometry on Self-feeding when Sawing Frozen Wood2017In: / [ed] Zbiec M & Orlowski K, 2017, p. 75-83Conference paper (Refereed)
    Abstract [en]

    Sawing during the cold winter period is a problem for sawmills operating in the northern parts of the world and is becoming an increasingly important economic factor. One common effect of processing frozen timber is poor barking leading to increased tool wear and decreased pulp-chip quality, which implies lower chip value. Other common effects in the conversion steps of a sawmill are sawdust attached to the surface of the sawn timber (sawdust gluing), knot rupture, tool breakdown, and self-feeding, i.e. the sawblade feeds the wood to be sawn more or less independent of the feeding equipment. This study deals with the self-feeding phenomenon and how this problem can be reduced by adapting tool parameters to the properties of the frozen wood material. The results show that the amount of sapwood in the sawn timber has a great influence on the amount of self-feeding and that the effect can be reduced by adapting the rake angle of the tool to the conditions of frozen timber. A bevel at the edges of the cutting teeth reduced self-feeding forces, but increased main cutting forces.

  • 73. Pambou Nziengui, C.F
    et al.
    Turesson, Jonas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Odounga, B
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Moutou Pitti, R
    Dérermination des principales caractéristiques physiques et mécaniques du sapin blanc du massif central et de l'okoumé du Gabon.2018Conference paper (Refereed)
    Abstract [en]

    The following study, shows on the basis of a series of tests carried out on samples of White fir species of the central massif and okume of Gabon, a database of the different physical and mechanical properties of these species. The tests are carried out indoors at room temperature, on specimens sized according to the French standard [AFN 06]. These specimens, whose physical properties are previously determined, are loaded in 4-point static bending on an electrostatic press. Then, using standardized calculation methods, a determination of the main mechanical parameters of these species is made. The results of the various comparative analyzes carried out show that there are no significant differences  between the parameters highlighted in this study for these different species despite the  difference between their growth areas.

  • 74.
    Pousette, Anna
    et al.
    SP Trä.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Shear resistance of glulam beams with cracks2012Conference paper (Refereed)
  • 75.
    Rudak, Pavel
    et al.
    Belarusian State Technological University.
    Barcik, Stefan
    Technological University in Zvolen.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Rudak, Oksana
    Belarusian State Technological University.
    Kuis, Dmitry
    Belarusian State Technological University.
    Vanko, Marek
    Belarusian State Technological University.
    Corrosive-Mechanical Wearing of Samples from High-Speed Steel with Vacuum-Plasma Coatings in the Condensate Environment of Wood Pyrolysis Products2017Conference paper (Refereed)
  • 76.
    Rudak, Pavel
    et al.
    Belarusian State Technological University.
    Barcik, Stefan
    Technical University in Zvolen.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Rudak, Oksana
    Belarusian State Technological University, Department of Technology and Design of Wooden Articles, Forestry and Wood Technology Faculty.
    Vanco, Marek
    Technology University in Zvolen, Depertment of Environmental and Forestry Machinery, Faculty of Environmental and Manufacturing Technology.
    Stefkova, Jaroslava
    Technology University in Zvolen, Institute of Foreign Languages.
    Motion of chips when leaving the cutting zone during chipboard plane milling2017In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 13, no 1, p. 646-661Article in journal (Refereed)
    Abstract [en]

    Mathematical equations were established and the following regularities of the plane milling process of wood materials were analyzed: the effect of the cutting edge inclination angle on the chip exit angle, influence of the cutting edge inclination angle on the speed of chip movement along the blade and exit speed of the chips from the cutting zone, the dependence of the chip exit angle on the friction coefficients of the chips on the processed material surface and along the blade surface (the friction coefficients were determined from the results of the experimental measurements), and influence of the mill rotation frequency on the chip exit angle. The milling of the chipboards with various mill designs was performed at different cutting conditions (diameter = 7 mm to 24 mm, number of cutting elements = 1 to 3, cutting edge inclination angle = -5° to 20°, frequency of the mill rotation = 3000 min-1 to 24000 min-1, feed per tooth = 0.1 mm to 1.5 mm). The process of chip exit from the cutting zone was photographed, and the chip exit angles were measured. A comparison of the values of the chip exit angles obtained from the experiments with those from the calculations based on the developed mathematical equations showed a high convergence.

  • 77.
    Schajer, Gary
    et al.
    Department of Mechanical Engineering, University of British Columbia, Vancouver.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Practical measurement of circular saw vibration mode shapes2012In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 7, no 3, p. 162-166Article in journal (Refereed)
    Abstract [en]

    Natural frequency measurement provides a convenient quantitative method for monitoring the tensioning state of a circular saw. However, it can often be difficult to interpret the measurements because the corresponding vibration mode shapes are not explicitly known, especially when adjacent natural frequencies are close together. A mode shape identification method is presented. It involves using two vibration sensors, one fixed and one orbiting the sawblade circumference. The performance of a simple prototype measurement device using this technique is described. The device could successfully identify the nodal diameter and nodal circle numbers of the major sawblade vibration modes.

  • 78.
    Turesson, Jonas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Berg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Impact of board width on in-plane shear stiffness of cross-laminated timber2019In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 196, article id 109249Article in journal (Refereed)
    Abstract [en]

    Board width-to-thickness ratios in non-edge-glued cross laminated timber (CLT) panels influence the in-plane shear stiffness of the panel. The objective is to show the impact of board width-to-thickness ratios for 3- and 5-layer CLT panels. Shear stiffnesses were calculated using finite element analysis and are shown as reduction factors relative to the shear stiffnesses of edge-glued CLT panels. Board width-to-thickness ratios were independently varied for outer and inner layers. Results show that the reduction factor lies in the interval of 0.6 to 0.9 for most width-to-thickness ratios. Results show also that using boards with low width-to-thickness ratios give low reduction factors. The calculated result differed by 2.9% compared to existing experimental data.

  • 79.
    Turesson, Jonas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Björnfot, Anders
    Department of Manufacturing and Civil Engineering, Faculty of EngineeringNorwegian University of Science and TechnologyGjøvikNorway.
    Berg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Tomasi, Roberto
    Faculty of Science and Technology, Division of Buildings, Architecture, and Environmental EngineeringNorwegian University of Life SciencesÅsNorway.
    Picture frame and diagonal compression testing of cross-laminated timber2019In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 52, no 4, article id 66Article in journal (Refereed)
    Abstract [en]

    Currently, no appropriate standard exists that describes how to determine the in-plane shear stiffness for cross-laminated timber (CLT) panels, meaning that, there is a lack of appropriate and reliable test methods. In this paper, two gross shear test methods are evaluated: a picture frame test and a diagonal compression test, which are intended to measure the shear stiffness of a whole CLT panel. This evaluation aimed to compare the shear modulus, the amount of compression/tension in the diagonal directions of the panels and the deformations of both sides of the panels. The picture frame test and diagonal compression test provides a bi- and uniaxial pre-stress, respectively. A total of 30 non-edge glued CLT panels were tested, 17 3-layer and 13 5-layer panels. The shear modulus for the 3- and 5-layer non-edge-glued panels were measured as 418 and 466 MPa, respectively, in the picture frame test. In the diagonal compression test, the shear modulus was measured to substantially higher values of 530 and 626 MPa for the 3- and 5-layer panels, respectively. In the picture frame test, panels were equally stretched along one of the diagonals as they were compressed along the other diagonal, which was not the case for panels in the diagonal compression test. The test results also showed that measuring only one side incurs a risk of over- or under-estimating the in-plane shear modulus. Compared with results from the literature, the picture frame test seems to be a more reliable test method than the diagonal compression test.

  • 80.
    Turesson, Jonas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Dosmaev, Dmitry
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Strengthening of Cross-Laminated Timber by adding aluminium plates2019Conference paper (Refereed)
    Abstract [en]

    Wood is commonly judged as orthotropic with three material directions: longitudinal, radial and tangential. Shear stressand strain can occur in different directions on surfaces with different directions and shear stiffness is commonlydescribed by three shear moduli. Of those, the weakest shear modulus is called the rolling shear modulus.Cross laminated timber (CLT) is a rather recent and innovative engineered wood product with properties that can be improved and which still requires research. The benefits of using wood in buildings and construction are far from beingmaximized. During recent years, timber has been used for constructing higher buildings. It has been seen that previous small and acceptable movements of the building are magnified, which can create discomfort for the occupants. In these cases, the problem is the low in-plane shear stiffness of the CLT panel. One way to increase the in-plane shear stiffness is to build CLT mixed with other materials, with high modulus of shear, and by that increase the in-plane shear stiffness of the CLT panel. A practical test and finite element analysis (FEA) of the shear modulus was performed on 3-layer samples reinforced with aluminium plates. The panels were built by three layer of wooden lamellas and the aluminium plate was added between the first and second and/or second and third layer of boards. Two different thicknesses of the aluminium plate were used, 1 mm and 1.5 mm. Also, panels without aluminium plates were used as reference. Diagonal compression test was performed on the CLT panels, where the modulus of shear could be calculated. The diagonal compression method was performed based on experience from Andreolli. The panels containing aluminium plates had a higher shear modulus than panels without aluminium plates. This was concluded in both the practical testing and FEA.

  • 81.
    Turesson, Jonas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Impact of laminate directions on inplane shear stiffness of crosslaminated timber2016In: Annual Meeting of the Northern European Network for Wood Science and Engineering WSE,: a key factor on the transition to Bioeconomy, 2016Conference paper (Refereed)
    Abstract [en]

    Twenty-three finite element models of cross-laminated timber (CLT) with different laminate directions were studied. Simulations with quadratic orthotropic linear elastic finite elements were conducted. One goal was to compare in-plane shear stiffnesses for CLT blocks made up from Norway Spruce (Picea abies) boards. 3- and 5-layer CLT were studied with board sizes 25x150x1200 mm. Bloc sizes were 75x1200x1200 and 125x1200x1200 mm for 3-layer and 5-layer blocs, respectively. The first and last layers laminate directions were assumed to be in direction 0. The second and fourth layers laminate directions for 5-layer models were assumed equal and were 5, 10, 15, 30, 45, 60, 75 and 90. The middle layer was in direction 0 or 90. For 3-layer models the middle layers laminate directions were 5, 10, 15, 30, 45, 60, 75 and 90. No edge gluing was assumed and thus all side edges were allowed to separate or overlap. Glued contact surfaces were assumed to be perfectly glued with rigid glue. The results for 5-layer models showed that all models with angled second and fourth layers were stiffer than the models with 90 layers. Stiffnesses for models with angled second and fourth layers were higher when the middle layer laminate direction was 90 compared to 0. The stiffest 5-layer model was the one with laminate directions 0/45/90/45/0. This stiffness was 1.5 times the shear stiffness of a reference block with 1-layer and solid timber shear stiffness. The stiffest 3-layer model was the one with laminate directions 0/30/0. This stiffness was 0.99 times the shear stiffness of the reference bloc.

  • 82.
    Turesson, Jonas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Berg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Comparison of Cross- and Stress-Laminated Timber Bridge Decks2017Conference paper (Refereed)
    Abstract [en]

    Simply supported bridge decks made of cross-laminated timber (CLT) and stress-laminated timber (SLT) are compared. The decks have a constant axle load and varying span and thickness. CLT in the form of a plate is built up from an uneven number of layers of boards with crosswise varying fibre directions. SLT is built up from glulam beams with the same fibre direction placed side by side to form a plate. Both CLT and SLT have homogenised mechanical and physical properties and can be produced as large elements. This study was conducted by comparing results from finite element simulations of bridge decks made up from SLT and CLT for various bridge spans. The ratio of timber volume needed to fulfil deflection limits for CLT and SLT increased as the bridge span increased. The ratio was 1.3 for 24 m span and width 3.2 m. The transverse displacement curve was flatter for CLT compared to SLT. Longitudinal displacement curves were similar for CLT and SLT.

  • 83.
    Wei, Hong
    et al.
    Nanjing Forestry University, Faculty of Material Science and Engineering.
    Guo, Xiaolei
    Nanjing Forestry University, Faculty of Material Science and Engineering.
    Zhu, Zhaolong
    Nanjing Forestry University, Faculty of Material Science and Engineering.
    Cao, Pingxiang
    Nanjing Forestry University, Faculty of Material Science and Engineering.
    Wang, Baojing
    Nanjing Forestry University, Faculty of Material Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Analysis of Cutting Performance in High Density Fiberboard Milling by Ceramic Cutting Tools2018In: Wood research, ISSN 1336-4561, Vol. 63, no 3, p. 455-466Article in journal (Refereed)
    Abstract [en]

    In order to study the cutting performance of TiC reinforced Al2O3 ceramic cutting tools in milling high density fiberboard, the effects of cutting parameter on the cutting forces, tool wear and cutting quality were investigated. Under the condition of same average chip thickness, feed per tooth and geometry angles, firstly, the change rate of maximum cutting forces were higher than that of average cutting forces at two different cutting speeds, and the cutting forces at high speed cutting was less than that at low speed cutting. Secondly, the flank wear at high speed cutting was more pronounced than that at low speed cutting, whose abnormal wear were pull-out of grain, cracking, chipping and flanking. Thirdly, the machining quality at high speed cutting was better than that at low speed cutting. Fourthly, the tendencies of cutting forces, tool wear and surface roughness relative to cutting length were similar, but the change rates were different, especially at the initial stage. Finally, high speed cuttingare plausible to use in HDF processing, which not only improves machining quality, but also promotes production efficiency.

  • 84.
    Zhaolong, Zhu
    et al.
    College of Material Science and Engineering, Nanjing Forestry University, Nanjing.
    Buck, Dietrich
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Marklund, Birger
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Guo, Xiaolei
    College of Material Science and Engineering, Nanjing Forestry University, Nanjing.
    Cao, Pingxiang
    College of Material Science and Engineering, Nanjing Forestry University, Nanjing.
    Zhu, Nanfeng
    College of Material Science and Engineering, Nanjing Forestry University, Nanjing.
    Cutting forces and chip formation revisited based on orthogonal cutting of Scots pine2018In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 73, no 2, p. 131-138Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to understandbetter the cutting forces and chip formation of Scots pine(Pinus sylvestris L.) with different moisture contents (MCs)and machined in different cutting directions. To thatend, an orthogonal cutting experiment was designed,in which Scots pine was intermittently machined usinga tungsten carbide tool to produce chips. The cuttingforces were measured and the chip shapes were quantitativelydescribed. Four conclusions can be drawn: (1)with increasing MC, the average cutting forces initiallydecreased and then stabilized, while the angle betweenthe direction of the main and the resultant force continuouslydecreased. (2) The average cutting forces in the 90°–0° cutting direction were lower than the same forces inthe 90°–90° cutting direction. (3) During machining, thedynamic cutting forces fluctuated less in the 90°–0° case.However, the dynamic feeding forces showed a decreasingtrend in both the 90°–0° and the 90°–90° cases. (4) Theprocess applied produced granule chips and flow chips,while less curly flow chips with a higher radius of curvaturewere more easily produced from samples with highMCs in the 90°–0° cutting direction.

  • 85.
    Zhaolong, Zhu
    et al.
    College of Materials Science and Engineering, Nanjing Forestry University, Nanjing.
    Buck, Dietrich
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Guo, Xiaolei
    College of Materials Science and Engineering, Nanjing Forestry University.
    Pingxiang, Cao
    College of Materials Science and Engineering, Nanjing Forestry University.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Machinability of stone-plastic materials during diamond planing2019In: Applied Sciences: APPS, ISSN 1454-5101, E-ISSN 1454-5101, Vol. 9, no 7, article id 1373Article in journal (Refereed)
    Abstract [en]

    This paper investigated the machinability of a stone–plastic composite (SPC) via orthogonal cutting with diamond cutters. The objective was to determine the effect of cutting depth on its machinability, including cutting forces, heat, chip formation, and cutting quality. Increased cutting depth promoted an increase in both frictional and normal forces, and also had a strong influence on the change in normal force. The cutting temperatures of chips and tool edges showed an increasing trend as cutting depth increased. However, the cutting heat was primarily absorbed by chips, with the balance accumulating in the cutting edge. During chip formation, the highest von Mises strain was mainly found in SPC ahead of the cutting edge, and the SPC to be removed partially passed its elastic limit, eventually forming chips with different shapes. Furthermore, the average surface roughness and the mean peak-to-valley height of machined surfaces all positively correlated to an increase in cutting depth. Finally, with an increase in cutting depth, the chip shape changed from tubular, to ribbon, to arc, to segmental, and finally, to helical chips. This evolution in chip shape reduced the fluctuation in cutting force, improving cutting stability and cutting quality.

  • 86.
    Zhu, Z.
    et al.
    College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, China.
    Cao, P.
    College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, China.
    Guo, X.
    College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, China.
    Qiu, X.
    College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, China.
    Xie, S.
    College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, China.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cutting performance of cemented carbide cutting tool in turning high‐density fiberboard2018In: Materialwissenschaft und Werkstofftechnik, ISSN 0933-5137, E-ISSN 1521-4052, Vol. 49, no 12, p. 1476-1484Article in journal (Refereed)
    Abstract [en]

    In order to provide a scientific and reliable guidance for wood processing industry, the effects of cutting parameters on cutting forces, cutting temperature and tool wear were studied when turning high‐density fiberboard by use of cemented‐carbide cutting tools. The results showed that cutting forces (normal force and radial force) and cutting temperature are not affected by the cutting parameters in the same way: cutting forces decrease with increasing spindle speed, whereas cutting temperature increase with an increase of the spindle speed. However, there is a positive relation for cutting forces and temperature, to the feed per turn when cutting. The wear of the cemented‐carbide cutting tool is shown by two mechanisms: Mainly adhesive wear but also abrasive wear, showed by loss of carbide‐grains and by cracking and chipping, respectively. This study also indicated that higher‐speed cutting is beneficial for wood‐processing; evident by reduced energy for cutting and higher efficiency in production.

  • 87.
    Zhu, Zhaolong
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Nanjing Forestry University, Coll Mat Sci & Engn, Nanjing, Jiangsu, China.
    Buck, Dietrich
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Guo, Xiaolei
    Nanjing Forestry University, Coll Mat Sci & Engn, Nanjing, Jiangsu, China.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cao, Pingxiang
    Nanjing Forestry University, Coll Mat Sci & Engn, Nanjing, Jiangsu, China.
    Effect of Cutting Speed on Machinability of Stone–Plastic Composite Material2019In: Science of Advanced Materials, ISSN 1947-2935, E-ISSN 1947-2943, Vol. 11, no 6, p. 884-892Article in journal (Refereed)
    Abstract [en]

    This research examined the orthogonal cutting of stone–plastic composite with diamond cutting tools. The objective was to quantify features relating to machinability, including cutting forces, cutting heat, chip formation, and machining quality with respect to cutting speed. The conclusions are as follows. An increased cutting speed promotes a decrease in the resulting force, causes cutting temperature to increase, makes the cutting processes more stable, and reduces the surface roughness. Chip-breaking length increases with an increase in cutting speed, and chip morphology changes from particle, to curve, to helical, and finally, to flow chips. Overall, a higher cutting speed is more suitable for machining stone–plastic composite materials: it not only increases the stability of cutting process, but also improves the final product of stone–plastic composite by promoting production of a smoother surface.

  • 88.
    Zhu, Zhaolong
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, Jiangsu, China.
    Buck, Dietrich
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Guo, Xiaolei
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, Jiangsu, China.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cao, Pingxiang
    College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, Jiangsu, China.
    Performance of stone-plastic composites with different mix ratios during orthogonal cutting2019In: Materials Express, ISSN 2158-5849, Vol. 9, no 7, p. 749-756Article in journal (Refereed)
    Abstract [en]

    The present study aimed to increase understanding of the machinability of stone-plastic materials with different mix ratios subjected to diamond planing. To that end, orthogonal cutting was carried out. Different stone-plastic materials were machined by diamond cutting tools to produce chips. Based on the results, four conclusions are drawn: (1) Among stone-plastic materials with decreasing polyvinyl chloride content ratio, the maximum cutting forces and fluctuation of dynamic forces show decreasing trends, and cutting stability increases. (2) The temperature of chips is slightly higher than that of tool edges; the cutting heat generated during machining is mainly absorbed by the chips of removed material and, to a lesser extent, stored in the tool edge. The type of stone-plastic material has a great effect on the changes in the temperatures of chip and tool edge. (3) With a decrease in polyvinyl chloride content, the chip shapes evolve from crack, to arc, and eventually to elemental chips. (4) The cutting quality of the machined surface improves with a decrease in the polyvinyl chloride content ratio of the stone-plastic materials.

  • 89.
    Zhu, Zhaolong
    et al.
    College of Material Science and Engineering, Nanjing Forestry University, Nanjing, Jiangsu, China.
    Buck, Dietrich
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Guo, Xiaolei
    College of Material Science and Engineering, Nanjing Forestry University, Nanjing, Jiangsu, China.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Pingxiang, Cao
    College of Material Science and Engineering, Nanjing Forestry University, Nanjing, Jiangsu, China.
    Wu, Zhenzeng
    Department of Material Engineering, Fujian Agriculture and Forestry University, Fujian, China.
    Machinability investigation in turning of high density fiberboard2018In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 13, no 9, p. 1-13, article id e0203838Article in journal (Refereed)
    Abstract [en]

    A series of experiments were conducted to assess the machinability of high density fiberboardusing cemented carbide cutting tools. The objective of this work was to investigate theinfluence of two cutting parameters, spindle speed and feed per turn, on cutting forces, chipformation and cutting quality. The results are as follows: cutting forces and chip-breakinglength decrease with increasing spindle speed and decreasing feed per turn. In contrast,surface roughness increases with decrease of spindle speed and increase in feed perturn. Chips were divided into four categories based on their shape: dust, particle, splinter,and semicontinuous chips. Chip-breaking length had a similar tendency to the varianceof cutting forces with respect to average roughness and mean peak-to-valley height: anincrease in the variance of cutting forces resulted in increased average roughness andmean peak-to-valley height. Thus, high cutting speed and low feed rate are parameters suitablefor high-quality HDF processing and will improve not only machining quality, but productionefficiency.

  • 90.
    Zhu, Zhaolong
    et al.
    Nanjing Forestry University.
    Guo, Xiaolei
    Nanjing Forestry University.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cao, Pingxiang
    Nanjing Forestry University.
    Na, Bin
    Nanjing Forestry University.
    Zhu, Nanfeng
    Nanjing Forestry University.
    The Effects of Cutting Parameters and Tool Geometry on Cutting Forces and Tool Wear in Milling High-density Fiberboard with Ceramic Tools2017In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 91, no 9-12, p. 4033-4041Article in journal (Refereed)
    Abstract [en]

    In this paper, the effects of cutting parametersand tool geometry on cutting forces and tool wear whenup-milling high-density fiberboard with alumina ceramiccutting tools were investigated. Under the condition ofthe same feed per tooth, average chip thickness, andclearance angle, the results shown are as follows: first,the tangential forces Ft and normal forces Fr at lowspeedcutting were higher than those at high-speed cutting,but increased slowly with the increase of cuttinglength and rake angle decrease. Second, increased cuttingspeed and decreased rake angle had a great effecton rake face wear. Third, the wear patterns of tool wearwere rake wear and flank wear, which included pull-outof grain, flaking, and chipping. The wear mechanismswere adhesive wear and abrasive wear. Finally, at lowspeedcutting, the cutting tools with bigger rake anglecan be selected to reduce the energy consumption ofmachine tools. The tools with smaller rake angle canbe used for high-speed cutting to improve tool lifeand productivity of processing.

  • 91.
    Zhu, Zhaolong
    et al.
    Nanjing Forestry University, Faculty of Material Science and Engineering.
    Guo, Xiaolei
    Nanjing Forestry University, Faculty of Material Science and Engineering.
    Na, Bin
    Nanjing Forestry University, Faculty of Material Science and Engineering.
    Liang, Xingyu
    Nanjing Forestry University, Faculty of Material Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ji, Futang
    Shanghai Vohringer Wood Product Co., Ltd.
    Research on cutting performance of ceramic cutting tools in milling high density fiberboard2017In: Wood research, ISSN 1336-4561, Vol. 62, no 1, p. 125-138Article in journal (Refereed)
    Abstract [en]

    The effect of cutting parameters and tool parameters on cutting forces and tool wear wereinvestigated in high density fiberboard (HDF) peripheral up-milling using toughened ceramiccutting tools. The results showed that whether at low speed cutting or high speed cutting, thetangential forces Ft and normal forces Fr increased slowly with the increase of cutting length. Thetangential forces Ft and normal forces Fr at low speed cutting were higher than that at high speedcutting. The tangential forces Ft and normal forces Fr decreased with the decrease of wedge anglein the same rake angle. Then, the effect of high cutting speed on the flank wear was greater thanthat at low cutting speed. The bigger wedge angle tools led to the serious flank wear. The mainwear pattern in milling HDF consisted of pull-out of the grain, flaking, chipping and cracking,the main wear mechanism were adhesive and abrasive wear

  • 92.
    Öhman, Micael
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grubii, Victor
    Remoistering of the wood before planing: a method for improved quality2015In: Proceedings of the 22nd International Wood Machining Seminar / [ed] Roger Hernández; Claudia B. Cáceres, Quebec city, Kanada: Universite Laval , 2015, p. 245-251, article id 5Conference paper (Refereed)
    Abstract [en]

    It is beneficial if the machining of wooden products is done at a moisture content equal to the climate the product is meant to be used in. For indoor products in central heated houses such moisture content is about 5-10%. For planing this is often a too low moisture content showing an increased risk of poor surface quality due to severe torn grain. Contrary to this too high moisture content will result in a fuzzy grain surface and problems with swelling and shrinkage of the product. The roughness of a machined wooden surface is affected by a number of different parameters like cutting tool geometry, machine settings and wood structure. The latter is the hardest to control since the surface quality is a result of the local combination of density, grain direction and moisture content. The larger the variation in wood features the more difficult it is to find a combination of tools and machine settings that will give a high surface quality.This study showed that by wetting the surface before machining, in this case planing, the average surface quality could be increased. No time dependences could be shown, wetting short before planing did show as good improvements as wetting treatment for 30 minutes or more.The study was based on a total of 120 test surfaces of Scots pine (Pinus silvestris L.). In order to maximize the variation in grain angle and density variations the test surfaces contained both clear wood as well as green knots.

  • 93.
    Öhman, Micael
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grubii, Victor
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Moistening of the wood surface before planing for improved surface quality2016In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 11, no 3, p. 156-163Article in journal (Refereed)
    Abstract [en]

    The roughness of a machined wooden surface is affected by a number of factors such as cutting tool geometry, machine settings and wood structure. The influence of wood structure on wood surface quality is difficult to control since the surface roughness is dependent on the local combination of density, grain direction and moisture content (MC). The greater the variation in wood features, the more difficult it is to find a combination of tools and machine settings that will give a high surface quality. The purpose was to study the impact of a surface wetting treatment before planing in order to reduce torn grain in the wood surface near knots in sawn timber of low MC. The study was based on a total of 120 specimens of Scots pine (Pinus sylvestris L.). To maximize the variation in grain orientation and density, the specimens contained both clear wood and knots. The results showed that when the surface was moistened before planing, chipped and torn grain in areas of deviating grain close to knots decreased. The response to wetting was rapid, wetting less than 30 s before planing gave as good an improvement as treatment time of 30 min or more.

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