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  • 901.
    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.

  • 902.
    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.

  • 903.
    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.

  • 904.
    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

  • 905.
    Öhman, Micael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Correspondences between manually estimated compression wood in Norway spruce and the warp of the sawn timber1999In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 57, no 5, p. 391-396Article in journal (Refereed)
    Abstract [en]

    Compression wood is regarded as a serious defect which affects the warp and machinability of sawn timber. To handle these problems, different regulations have been developed regarding grading of sawlogs and of sawn timber. This study is an attempt to clarify the relation between the amount of visible compression wood in Norway spruce (Picea abies L.) and the warping of the sawn timber in terms of bow, spring and twist as well as further deformation after ripping of the dried products. The amount of compression wood was defined and measured on logs according to the methods of the Swedish Timber Measurement Council (Regulations for measuring of round wood) and on the sawn timber according to the Nordic Timber. The impact of two different drying schedules was also investigated. The study shows that visible compression wood in both the butt end of the log and within the sawn timber was a rather poor indicator of the warp of the dried sawn timber. In no comparison did the correlation coefficient, r, exceed 0.3. In contrast to this, the correlation between the amount of compression wood and the warp of secondary products was fair, r = 0.79. This means that it should be possible to identify sawn timber less suitable for secondary processing by the amount of compression wood. The corresponding correlation between compression wood in the butt end of the log and the warp of the secondary products was r = 0.46. No significant differences could be shown in the degree of warp, as related to compression wood, between sawn timber or secondary products, dried at a wet-bulb temperature of 55 °C/117 h, LT-schedule, and a dry-bulb temperature of 110 °C/24 h, HT-schedule, respectively.

  • 906.
    Öhman, Micael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grade prediction of Pinus sylvestris logs with the aid of a radiograph image log1998In: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 13, p. 83-89Article in journal (Refereed)
  • 907.
    Öhman, Micael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Methods for avoiding the negative effects of compression wood2001Report (Other academic)
    Abstract [en]

    This is a study of how the selection of raw material and sawing methods affects the magnitude of bow, spring and twist as well as the yield of accepted wall studs when graded with respect to straightness. The focus was on the relation between compression wood in butt logs of Norway spruce (Picea abies (L.) Karst) and the straightness of wall studs, in order to improve the sawmills ability to satisfy the customer demands by straighter sawn products. The following aspects of compression wood in the production process were examined:

  • 908.
    Öhman, Micael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Modelling compression wood in sawn timber of Scot pine and Norway spruce1999In: Connection between silviculture and wood quality through modelling approaches and simulation softwares: third workshop : La Londe-Les-Maures, France, 1999 : proceedings / [ed] Gérard Nepveu, Nancy: INRA Editions, 1999Conference paper (Refereed)
  • 909.
    Öhman, Micael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Plank grade indicators in radiograph images of Scots pine logs1999In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 57, no 5, p. 359-363Article in journal (Refereed)
    Abstract [en]

    It is possible today to detect the internal structure of a log by using X-ray scanning technology. By visual inspection of a longitudinal radiograph image (LRI) of a log, it is possible to manually predict the coming grade of the centre planks. The objective of this study was to identify the features of Scots pine logs visible in the LRI's that were of importance in a manual grading process. The identification of useful features was determined by a survey among respondents connected to the wood and sawmill industry. The test logs originate from the Swedish stem bank and the evaluation of the results was based on the statistical method of partial least square regression (PLS). This study shows that useful indicators of the true grade of the centre planks were the knots and knot-related features as well as the butt swell and the heart wood fraction of the log.

  • 910.
    Öhman, Micael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Prediction of the properties of sawn timber by visual inspection of sawlogs1998Licentiate thesis, comprehensive summary (Other academic)
  • 911.
    Öhman, Micael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The measurement of compression wood and other wood features and the prediction of their impact on wood products2001Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wood is a complex and highly variable biological material formed to give the tree best possible conditions for sustaining life. Thus every piece of wood is possessed of unique qualities. The great challenge in the process of manufacturing wood products has always been to select pieces of wood with properties that fulfil requirements for the product. The importance of selecting the right piece of wood will increase along with demands from customers for products with specific properties, such as moisture content, warp, strength, biological and aesthetic features. In order to supply customers with the products they request, a considerably improved selection of the raw material is needed. The earlier an accurate selection can be done, the better. To improve this selection or pregrading process, knowledge of the relationships between different features and different aspects of quality, as well as methods for measuring external and internal features, must be developed. The main objective of this work was to contribute to improved predictability of the quality of dried sawn products using the features both of logs and of sawn green products as input. This work was divided into two parts: Part one focused on the possibility of learning how to predict the quality grades of centre planks by manually inspecting longitudinal radiograph images (LRI) that depict the density variation within a log. In a survey respondents were interviewed regarding their interpretations of the density related features visible in the LRIs of Scots pine logs (Pinus silvestris L). The purpose was to be able to use these interpretations in predicting the final quality of planks sawn from the logs. The LRIs were reconstructed with the aid of an X-ray CT scanner. Part two focused on the relationship between compression wood (CW) in foremost butt logs of Norway spruce (Picea abies (L.) Karst) and the warp of the sawn products, on how to detect CW and on how to predict warp. The logs used in the study were chosen among logs delivered to and sawn at commercial sawmills located in the northern part of Sweden in order to assure that conditions in the study match those extant in commercial sawmills. The most important findings in this thesis are: Longitudinal radiograph images of the density variation within a log can be a powerful aid in manual grading of logs with respect to the quality of the resulting sawn products. The shape of the sawn, but not dried, centre planks is an indicator of both the amount and distribution of compression wood. Basing the cutting of planks on their shapes while still green can considerably increase the total length of acceptably straight dried products. This improvement is achieved through the elimination of compression wood.

  • 912.
    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.

  • 913.
    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.

  • 914.
    Öhman, Micael
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Nyström, Jan
    Measurement of green plank shape for prediction and elimination of compression wood2002In: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 17, no 4, p. 377-384Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to predict the amount and the distribution of compression wood (CW) within a Norway spruce [Picea abies (L.) Karst.] plank based on green plank curvature. The findings indicated a possibility of predicting the longitudinal distribution of CW from the green plank curvature. Areas free from CW showed a typical concave shape in relation to the centre of the log, while CW was present when a convex shape was shown. The larger the magnitude of convex curvature, the higher the concentrations of CW that could be found, and a larger fraction of dried planks was rejected due to excessive warp. This study also determined what information can be used to eliminate areas of high concentrations of CW by cutting and how cutting affects the grading results with respect to warp. Over 50% of the plank length showing a high concentration of CW (> 30% of the cross-cut volume) was successfully cut off. Cutting strategies based on predicted CW concentrations resulted in a 10-40% increase in accepted plank length.

  • 915.
    Öhman, Micael
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Nyström, Jan
    Modelling distribution and amount of compression wood by the shape of the green bow within planks of Norway spruce2003In: IWSS 5: Proceedings / Fifth International conference om image processing and scanning of wood, March 23 to 26, 2003, Bad Waltersdorf, Austria, Europe, Joanneum research , 2003, p. 13-24Conference paper (Other academic)
16171819 901 - 915 of 915
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