| 1. |
- Jonsén, Pär, 1971-, et al.
(författare)
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A Novel Method for Modelling of Cold Cutting of Microstructurally Tailored Hot Formed Components
- 2019
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Ingår i: Hot sheet metal forming of high-performance steel. - : Wissenschaftliche Scripten. ; , s. 645-652
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 2. |
- Jonsén, Pär, et al.
(författare)
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Charge and structure behaviour in a tumbling mill
- 2010
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Ingår i: The Fifth International Conference on Discrete Element Methods. - London : Research Publishing Services. - 9780955117985 ; , s. 490-495
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Konferensbidrag (refereegranskat)abstract
- The grinding process in tumbling mills is complex and to include all phenomena that occur in a single numerical model is today not possi-ble. This paper presents the results of a study in which the deflection of a lifter bar in a pilot ball mill is measured by an embedded strain gauge sensor and compared to deflections predicted from finite ele-ment (FE) simulations. The flexible rubber lifter and the lining in a tumbling mill are modelled with the finite element method (FEM) and the grinding medium modelled with the distinct element method (DEM). The deflection profile obtained from DEM-FE simulation shows a reasonably good correspondence to pilot mill measurements. The approach presented here is a contribution to the validation of DEM-FE simulations and an introduction to the description of a bend-able rubber lifter implemented in a DEM-FEM mill model. It opens up the possibility to predict contact forces for varying mill dimensions and liner combinations. FEM is especially valuable in this case, since there are readily available libraries with material models. This is a fol-low-up work to previous preliminary result from a mono-size ball charge interaction study
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| 3. |
- Jonsén, Pär, et al.
(författare)
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Development of physically based tumbling mill models
- 2014
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Ingår i: Proceedings of XXIII International Mineral Processing Congress. - Santiago : IMPC. - 9789569393150
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Konferensbidrag (refereegranskat)abstract
- Numerical modelling of grinding in tumbling mills is traditionally done with the discrete element method (DEM). The grinding balls are then represented by DEM particles and the mill structure is considered rigid. To include more physical phenomena several numerical methods can be combined. One important improvement is to include the mill structure response, using the finite element method (FEM). The interaction between charge and lining can then be studied in detail. The pulp can also be included using a particle-based continuum method e.g. smoothed particle method (SPH). The strength of SPH lies in modelling of free surface flows and very large deformations and it is suited to model simultaneous fluid and granular flow. Still, the coarse particles (grinding balls) in the charge are suitable to be model using DEM. Each of these methods has their strength and weaknesses, but combined they can successfully mimic the main features of the charge movement. With these numerical tools the complex interaction between the different components of the grinding process; pulp, charge, lining and the mechanical behaviour of the mill, can be studied together. This work will present novel numerical approaches to model, simulate and validate charge behaviour in tumbling mills. These numerical models give possibilities to better understand the physical and mechanical behaviour of particulate material systems during grinding in a tumbling mill. This is important in order to develop and optimise future high-capacity grinding circuits and save energy.
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| 4. |
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| 5. |
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| 6. |
- Jonsén, Pär, et al.
(författare)
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Novel simulation methods for mill charges
- 2011
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Ingår i: Conference in minerals engineering. - Luleå : Luleå tekniska universitet. - 9789174392203
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 7. |
- Jonsén, Pär, et al.
(författare)
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Prediction of mill structure behaviour in a tumbling mill
- 2010
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Ingår i: Conference in Minerals Engineering. - Luleå : Luleå tekniska universitet. - 9789174390971 ; , s. 85-98
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Computational demands and the lack of detailed experimental verification have limited the value of Distinct Element Method (DEM) modelling approaches in mill simulation studies. This paper presents the results of a study in which the deflection of a lifter bar in a pilot ball mill is measured by an embedded strain gauge sensor and compared to deflections predicted from finite element (FE) simulations. The flexible rubber lifter and the lining in a tumbling mill are modelled with the finite element method (FEM) and the grinding medium modelled with DEM. The deflection profile obtained from DEM-FE simulation shows a reasonably good correspondence to pilot mill measurements. To study the charge impact on the mill structure two different charges are used in the simulations. The approach presented here is a contribution to the validation of DEM-FE simulations and an introduction to the description of a bendable rubber lifter implemented in a DEM-FEM mill model. It opens up the possibility to predict contact forces for varying mill dimensions and liner combinations. FEM is especially valuable in this case, since there are readily available libraries with material models. This is a follow-up work to previous preliminary result from a mono-size ball charge interaction study.
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| 8. |
- Jonsén, Pär, et al.
(författare)
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Prediction of mill structure behaviour in a tumbling mill
- 2011
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Ingår i: Minerals Engineering. - : Elsevier BV. - 0892-6875 .- 1872-9444. ; 24:3-4, s. 236-244
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Tidskriftsartikel (refereegranskat)abstract
- Computational demands and the lack of detailed experimental verification have limited the value of distinct element method (DEM) modelling approaches in mill simulation studies. This paper presents the results of a study in which the deflection of a lifter bar in a pilot ball mill is measured by an embedded strain gauge sensor and compared to deflections predicted from finite element (FE) simulations. The flexible rubber lifter and the lining in a tumbling mill are modelled with the finite element method (FEM) and the grinding medium is modelled with DEM. The deflection profile obtained from DEM-FE simulation shows a reasonably good correspondence to pilot mill measurements. To study the charge impact on the mill structure two different charges are used in the simulations. The approach is a contribution to the validation of DEM-FE simulations and an introduction to the description of a bendable rubber lifter implemented in a DEM-FEM mill model. It opens up the possibility to predict contact forces for varying mill dimensions and liner combinations. FEM is especially valuable in this case, since there are readily available libraries with material models.
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| 9. |
- Jonsén, Pär, et al.
(författare)
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Simulation of charge and structure behaviour in a tumbling mill
- 2011
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Ingår i: 8th European LD-DYNA Users Conference May 23-24, 2011, Strasbourg.
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Konferensbidrag (refereegranskat)abstract
- For a long time discrete element methods (DEM) has been used as simulation tools to gain insight into particulate flow processes. The mechanical behaviour in tumbling mills is complex. To include all phenomena that occur in a single numerical model is today not possible. A common approach is to model milling charges using the DEM assuming a rigid mill structure. To close the gap between reality and numerical models in milling, more physically realistic methods have to be used. In this work, the finite element method (FEM) and the smoothed particle hydrodynamic (SPH) method are used together to model a ball mill charge in a tumbling mill. The mesh free formulation and the adaptive nature of the SPH method result in a method that handles extremely large deformations and thereby suits for modelling of grinding charges. The flexible rubber lifter and the lining are modelled with the finite element method. The mill structure consists of rubber lifter and liners and a mantel made of solid steel. For the elastic behaviour of the rubber, a Blatz-Ko hyper-elastic model is used. The supplier of the lining provided experimental data for the rubber. The deflection profile of the lifters obtained from SPH-FEM simulation shows a reasonably good correspondence to pilot mill measurements as measured by an embedded strain gauge sensor. This computational model makes it possible to predict charge pressure and shear stresses within the charge. It is also possible to predict contact forces for varying mill dimensions and liner combinations.
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| 10. |
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