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Jonsén, P., Svanberg, A., Ramirez, G., Casellas, D., Hernández, R., Marth, S., . . . Oldenburg, M. (2019). A Novel Method for Modelling of Cold Cutting of Microstructurally Tailored Hot Formed Components. In: Mats Oldenburg, Jens Hardell, Daniel Casellas (Ed.), CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, 2019: . Paper presented at CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, Luleå, Sweden, June 2nd to 5th 2019 (pp. 645-652). , 7
Open this publication in new window or tab >>A Novel Method for Modelling of Cold Cutting of Microstructurally Tailored Hot Formed Components
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2019 (English)In: CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, 2019 / [ed] Mats Oldenburg, Jens Hardell, Daniel Casellas, 2019, Vol. 7, p. 645-652Conference paper, Published paper (Refereed)
Abstract [en]

In the last decade, hot metal forming of advanced high strength steel (AHSS) have improved passenger safety and open possibilities for lightweight design. Hot metal forming can be applied to locally tailor the microstructure of components and gradual vary mechanical properties to improve crash resistance behaviour and optimized weight for e.g. safety related parts. Sometimes post punching or trimming must be done on hardened parts. Such conditions induce damage and fractures in the trimmed edge. Another issue is that high pressures are required in cutting operations due to the high yield stress of press hardened parts, which accelerate wear and produce premature fracture in tools. Optimizing cutting operations to minimize damage and wear are essentials and numerical simulations of cutting operations can be of good assistance. One of the main challenges in the numerical modelling consists of numerically be able to treat the extremely large deformation occurring in the cutting zone. A second challenge is to find suitable failure models. In this work, the punching process of soft and hard microstructures obtained by press hardening is experimentally studied, but also modelled with a combination of smoothed particle Galerkin (SPG) method and finite element method (FEM). Laboratory punching tests with different clearance values were carried out using sheets of different fracture strengths. All experimental cases are numerically modelled. Validation is conducted by comparing numerical results with experimental measurements of punch force and displacement. In addition, morphology of the final cutting edges from both real and virtual are compared. Numerical results show good agreement against experimental measurements. Furthermore, the combined method gives robust-ness and stability as it can handle large deformations efficiently.

National Category
Applied Mechanics
Identifiers
urn:nbn:se:ltu:diva-75748 (URN)
Conference
CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, Luleå, Sweden, June 2nd to 5th 2019
Available from: 2019-08-29 Created: 2019-08-29 Last updated: 2019-08-29
Frómenta, D., Parareda, S., Lara, A., Casellas, D., Pujante, J., Jonsén, P., . . . Oldenburg, M. (2019). Fracture Toughness Evaluation of Thick Press Hardened 22MnB5 Sheets for High Crash Performance Applications in Trucks. In: Mats Oldenburg, Jens Hardell, Daniel Casellas (Ed.), CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, 2019: . Paper presented at CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, Luleå, Sweden, June 2nd to 5th 2019 (pp. 113-121).
Open this publication in new window or tab >>Fracture Toughness Evaluation of Thick Press Hardened 22MnB5 Sheets for High Crash Performance Applications in Trucks
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2019 (English)In: CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, 2019 / [ed] Mats Oldenburg, Jens Hardell, Daniel Casellas, 2019, p. 113-121Conference paper, Published paper (Refereed)
National Category
Applied Mechanics
Identifiers
urn:nbn:se:ltu:diva-75751 (URN)
Conference
CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, Luleå, Sweden, June 2nd to 5th 2019
Available from: 2019-08-29 Created: 2019-08-29 Last updated: 2019-08-29
Ramanenka, D., Gustafsson, G. & Jonsén, P. (2019). Influence of heating and cooling rate on the stress state of the brick lining in a rotary kiln using finite element simulations. Engineering Failure Analysis, 105, 98-109
Open this publication in new window or tab >>Influence of heating and cooling rate on the stress state of the brick lining in a rotary kiln using finite element simulations
2019 (English)In: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 105, p. 98-109Article in journal (Refereed) Published
Abstract [en]

Rotary kilns for iron-ore pellets production are highly dependent on a well-functioned refractory brick lining. To improve the long-term capability of the lining, in-situ observations of the bricks' performance are desired, however, the harsh environment inside the rotary kiln makes it difficult or nearly impossible to study the lining during operation. By using numerical simulations as a tool, some of the problems encountered by the brick lining can be studied without limitation of the extreme conditions.

In this work, stress state of the lining was studied under the influence of different heating and cooling rates, and different brick compaction cases. A finite element model was created for conducting the numerical simulations. The numerical model was calibrated for transient heat transfer. Temperature dependent material properties of the bricks and casing were used as input. The heating and cooling was controlled by temperature prescription on the boundary of the brick lining, while brick lining compaction by defining relative position of the bricks in axial and radial directions.

The conducted numerical simulations showed that considerable tensile stress may appear in a large area of the brick during initial heating stage. The large tensile area corresponds well with the typical circumferential cracks experienced by the bricks. It was demonstrated that the compressive stresses counteract the development of tensile stresses. However, the compressive stresses may become very large in the initial stage of heating. The positive effect of lower heating rate was considerable on the tensile stresses, while influence on the compressive stresses was almost unnoticed. The hypothetical cooling rates showed that very high tensile stresses may occur on the surface of the bricks, potentially leading to surface spalling. Furthermore, it was demonstrated that axial compaction is highly important on the stress development in the lining, which, may not always be followed in practice. As a general conclusion, it is recommended to always achieve a tight compaction of the brick lining and to take measures for lowering the heating and cooling rates.

The conducted work exemplifies behaviour of the brick lining for realistic heat transfer and material properties. The insight into the behaviour gives possibilities to make adjustments and directed investments for lowering risk of brick lining failure.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
High temperature, Stress state, Refractory brick lining, Rotary kiln, Finite element method
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-68375 (URN)10.1016/j.engfailanal.2019.06.031 (DOI)
Note

Validerad;2019;Nivå 2;2019-07-08 (johcin)

Available from: 2018-04-16 Created: 2018-04-16 Last updated: 2019-07-08Bibliographically approved
Golling, S., Frometa, D., Casellas, D. & Jonsén, P. (2019). Influence of microstructure on the fracture toughness of hot stamped boron steel. Materials Science & Engineering: A, 743, 529-539
Open this publication in new window or tab >>Influence of microstructure on the fracture toughness of hot stamped boron steel
2019 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 743, p. 529-539Article in journal (Refereed) Published
Abstract [en]

The automotive industry's desire for weight reduction while maintaining crashworthiness demands development of materials and material properties within the economic framework of consumers. The industrial process of hot stamping provides a technique to utilize steel in an efficient way. In hot stamping, microstructural characteristics of a steel blank are influenced by controlling the cooling rate. Hot stamping has become a prevalent method for lightweight solutions in car bodies without sacrificing passenger safety. The process of hot stamping applies sequential forming and quenching in a single production step. During the cooling of the blank, various microstructures can be formed depending on the cooling rate or holding temperature. Special tooling allows the application of different cooling rates within the same blank. Thus, the microstructure and mechanical properties can be influenced in designated areas of a blank.

Fracture toughness properties of sheet metal are necessary to better understand fracture initiation and crack propagation during crash loading as well as improve crashworthiness predictions. This paper focus on fracture toughness of low-alloyed boron steel sheet common in the automotive industry. A heat treatment process is used to form different microstructures, predominately consisting of one single phase or mixed microstructures with two distinct phases. The fracture toughness of the present microstructures is evaluated using the Essential Work of Fracture methodology. Results are discussed in terms of the different microstructures obtained and the consequent part performance.

Results show a strong connection between microstructure and fracture toughness. The bainitic grade shows favorable fracture toughness while a mixed microstructure of bainite and martensite shows a very brittle fracture behavior. A post heat treatment in the form of paint bake curing shows a negligible effect on fracture toughness of martensite.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Fracture toughness, Essential work of fracture, Heat treatment, 22MnB5, Hot stamping
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-71682 (URN)10.1016/j.msea.2018.11.080 (DOI)000456891500060 ()2-s2.0-85057313484 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-01-31 (johcin) 

Available from: 2018-11-20 Created: 2018-11-20 Last updated: 2019-09-13Bibliographically approved
Hammarberg, S., Kajberg, J. & Jonsén, P. (2019). Modeling of Ultra High Strength Steel Sandwiches with Lightweight Cores. In: Mats Oldenburg, Jens Hardell, Daniel Casellas (Ed.), CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel: . Paper presented at CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, Luleå, Sweden, June 2nd to 5th 2019 (pp. 313-320).
Open this publication in new window or tab >>Modeling of Ultra High Strength Steel Sandwiches with Lightweight Cores
2019 (English)In: CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel / [ed] Mats Oldenburg, Jens Hardell, Daniel Casellas, 2019, p. 313-320Conference paper, Published paper (Refereed)
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-75752 (URN)
Conference
CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, Luleå, Sweden, June 2nd to 5th 2019
Available from: 2019-08-29 Created: 2019-08-29 Last updated: 2019-08-29
Rodriguez Prieto, J. M., Carbonell, J. & Jonsén, P. (2019). Numerical Methods for the Modelling of Chip Formation. Archives of Computational Methods in Engineering
Open this publication in new window or tab >>Numerical Methods for the Modelling of Chip Formation
2019 (English)In: Archives of Computational Methods in Engineering, ISSN 1134-3060, E-ISSN 1886-1784Article in journal (Refereed) Epub ahead of print
Abstract [en]

The modeling of metal cutting has proved to be particularly complex due to the diversity of physical phenomena involved, including thermo-mechanical coupling, contact/friction and material failure. During the last few decades, there has been significant progress in the development of numerical methods for modeling machining operations. Furthermore, the most relevant techniques have been implemented in the relevant commercial codes creating tools for the engineers working in the design of processes and cutting devices. This paper presents a review on the numerical modeling methods and techniques used for the simulation of machining processes. The main purpose is to identify the strengths and weaknesses of each method and strategy developed up-to-now. Moreover the review covers the classical Finite Element Method covering mesh-less methods, particle-based methods and different possibilities of Eulerian and Lagrangian approaches.

Place, publisher, year, edition, pages
Springer, 2019
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-72672 (URN)10.1007/s11831-018-09313-9 (DOI)
Available from: 2019-01-24 Created: 2019-01-24 Last updated: 2019-01-24
Jonsén, P., Hammarberg, S., Pålsson, B. & Lindkvist, G. (2019). Preliminary validation of a new way to model physical interactions between pulp, charge and mill structure in tumbling mills. Minerals Engineering, 130, 76-84
Open this publication in new window or tab >>Preliminary validation of a new way to model physical interactions between pulp, charge and mill structure in tumbling mills
2019 (English)In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 130, p. 76-84Article in journal (Refereed) Published
Abstract [en]

Modelling of wet grinding in tumbling mills is an interesting challenge. A key factor is that the pulp fluid and its simultaneous interactions with both the charge and the mill structure have to be handled in a computationally efficient way. In this work, the pulp fluid is modelled with a Lagrange based method based on the particle finite element method (PFEM) that gives the opportunity to model free surface flow. This method gives robustness and stability to the fluid model and is efficient as it gives possibility to use larger time steps. The PFEM solver can be coupled to other solvers as in this case both the finite element method (FEM) solver for the mill structure and the DEM solver for the ball charge. The combined PFEM-DEM-FEM model presented here can predict charge motion and responses from the mill structure, as well as the pulp liquid flow and pressure. All cases presented here are numerically modelled and validated against experimentally measured driving torque signatures from an instrumented small-scale batch ball mill equipped with a torque meter and charge movements captured from high-speed video. Numerical results are in good agreement with experimental torque measurements and the PFEM solver also improves on efficiency and robustness for solving charge movements in wet tumbling mill systems.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Grinding, Modelling, Simulation, Validation
National Category
Applied Mechanics Metallurgy and Metallic Materials
Research subject
Solid Mechanics; Mineral Processing
Identifiers
urn:nbn:se:ltu:diva-71226 (URN)10.1016/j.mineng.2018.10.013 (DOI)000452937000010 ()2-s2.0-85054850385 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-10-16 (svasva)

Available from: 2018-10-16 Created: 2018-10-16 Last updated: 2019-02-01Bibliographically approved
Larsson, S., Pålsson, B., Parian, M. & Jonsén, P. (2019). Preliminary validation of a stirred media mill model. In: : . Paper presented at Conference in Minerals Engineering 2019.
Open this publication in new window or tab >>Preliminary validation of a stirred media mill model
2019 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Wet fine grinding is an important process in the minerals industry. Modelling of wet grinding in stirred media mills is challenging since it requires the simultaneous modelling of grinding media consisting of a huge number of small grinding bodies, moving internal stirrer, and the pulp fluid. All of them in interaction with each other. In the present study, wet grinding in a stirred media mill is studied using coupled incompressible computational fluid dynamics (ICFD) and discrete element method (DEM) and finite element method (FEM) simulations. The DEM is used to model the grinding media, and the pulp fluid flow is modelled using the ICFD. Moreover, the FEM is used to model the structure of the mill body and is in combination with DEM used to estimate the wear rate in the system. The present implementation of the coupled ICFD-DEM-FEM preserves the robustness and efficiency of both methods, and it gives the possibility to use large time steps for the fluid with very low computation times.

National Category
Applied Mechanics Metallurgy and Metallic Materials
Research subject
Solid Mechanics; Mineral Processing
Identifiers
urn:nbn:se:ltu:diva-72951 (URN)
Conference
Conference in Minerals Engineering 2019
Available from: 2019-02-19 Created: 2019-02-19 Last updated: 2019-02-22
Neikter, M., Forsberg, F., Pederson, R., Antti, M.-L., Åkerfeldt, P., Larsson, S., . . . Puyoo, G. (2018). Defect characterization of electron beam melted Ti-6Al-4V and Alloy 718 with X-ray microtomography. Aeronautics and Aerospace Open Access Journal, 2(3), 139-145
Open this publication in new window or tab >>Defect characterization of electron beam melted Ti-6Al-4V and Alloy 718 with X-ray microtomography
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2018 (English)In: Aeronautics and Aerospace Open Access Journal, ISSN 2576-4500, Vol. 2, no 3, p. 139-145Article in journal (Refereed) Published
Abstract [en]

Electron beam melting (EBM) is emerging as a promising manufacturing process where metallic components are manufactured from three-dimensional (3D) computer aided design models by melting layers onto layers. There are several advantages with this manufacturing process such as near net shaping, reduced lead times and the possibility to decrease weight by topology optimization, aspects that are of interest for the aerospace industry. In this work two alloys, Ti-6Al-4V and Alloy 718, widely used within the aerospace industry were investigated with X-ray microtomography (XMT), to characterize defects such as lack of fusion (LOF) and inclusions. It was furthermore possible to view the macrostructure with XMT, which was compared to macrostructure images obtained by light optical microscopy (LOM). XMT proved to be a useful tool for defect characterization and both LOF and un-melted powder could be found in the two investigated samples. In the EBM built Ti-6Al-4V sample high density inclusions, believed to be composed of tungsten, were found. One of the high-density inclusions was found to be hollow, which indicate that the inclusion stems from the powder manufacturing process and not related with the EBM process. By performing defect analyses with the XMT software it was also possible to quantify the amount of LOF and un-melted powder in vol%. From the XMT-data meshes were produced so that finite element method (FEM) simulations could be performed. From these FEM simulations the significant impact of defects on the material properties was evident, as the defects led to high stress concentrations. It could moreover, with FEM, be shown that the as-built surface roughness of EBM material is of importance as high surface roughness led to increased stress concentrations.

Place, publisher, year, edition, pages
MedCrave Group, 2018
Keywords
X-ray tomography, Ti-6Al-4V, Alloy 718, defects and electron beam melting
National Category
Metallurgy and Metallic Materials Other Materials Engineering Fluid Mechanics and Acoustics Applied Mechanics
Research subject
Engineering Materials; Solid Mechanics; Experimental Mechanics
Identifiers
urn:nbn:se:ltu:diva-68924 (URN)10.15406/aaoaj.2018.02.00044 (DOI)
Available from: 2018-05-28 Created: 2018-05-28 Last updated: 2018-11-08Bibliographically approved
Larsson, S., Gustafsson, G., Jonsén, P. & Häggblad, H.-Å. (2018). DEM-CFD Simulation of the Effect of Air on Powder Flow During Die Filling. In: : . Paper presented at 13th World Congress in Computational Mechanics.
Open this publication in new window or tab >>DEM-CFD Simulation of the Effect of Air on Powder Flow During Die Filling
2018 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

In the field of powder metallurgy (PM), complex components with complicated shapes can be manufactured. One important step in the PM process is the powder pressing process, where powder is consolidated during a forming operation into a desired shape, normally by applying pressure. During powder pressing, the mechanical properties of powder materials change dramatically. PM manufacturers tend to produce components with shapes of increasing complexity, requiring improved pressing equipment and methods. The most crucial aspect is to control the powder flow during die filling and the final powder density distribution after the filling stage, which has been shown to affect the strength of the final component significantly [1].

To investigate the non-homogeneity of the density of PM components, experimental studies combined with numerical simulations of the die filling stage are exploited.

This work covers the numerical modelling and simulation of die filling. The discrete element method (DEM) [2] was used to model the powder, and computational fluid dynamics (CFD) to model the air. To study the effect of air on powder flow, the DEM was coupled to the CFD using a two-way coupling approach. Experimental measurements with digital speckle photography (DSP) from a previous study [3] were used for comparison with the numerical simulations.

The comparison of the DSP measurements and the numerical simulations showed similar macroscopic flow characteristics. Thus, the adequacy of the proposed DEM-CFD model has been demonstrated in a metal powder die filling operation. The DEM-CFD method has been shown to be an effective method for the numerical simulation of the interaction between powder and air.

 

References

[1]   Zenger, D. & Cai, H. (1997). Handbook of the Common Cracks in Green P/M Compacts. Metal Powder Industries Federation, MPIF. Worcester, USA.

[2]   Cundall, P. A., & Strack, O. D. (1979). A discrete numerical model for granular assemblies. geotechnique, 29(1), 47-65.

[3]   Larsson, S., Gustafsson, G., Jonsén, P. & Häggblad, H.-Å. (2016). Study of Powder Filling Using Experimental and Numerical Methods.  In: World PM2016 Congress & Exhibition, Hamburg, October 9-13, 2016.

National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-71547 (URN)
Conference
13th World Congress in Computational Mechanics
Available from: 2018-11-12 Created: 2018-11-12 Last updated: 2018-11-27
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-0910-7990

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