Mikael Schill - Academia.edu (original) (raw)

Papers by Mikael Schill

Linköping Electronic Conference Proceedings

Simulation Modelling Practice and Theory

Simulation of sheet metal forming is one of the major applications of LS-DYNA. Today, a majority ... more Simulation of sheet metal forming is one of the major applications of LS-DYNA. Today, a majority of the forming industry is using Finite Element models to design the stamping dies in order to preve ...

Simulation of the welding process in LS-DYNA has been continuously improving the recent years. Th... more Simulation of the welding process in LS-DYNA has been continuously improving the recent years. The functionality in terms of solvers, materials, heat source and preprocessing GUI have been continuously expanded. One of the issues that remains to be solved is the sometimes quite long simulation times. The solution time of a welding simulation depends largely on the length and speed of the weld. This is especially true in Additive Manufacturing (AM) applications where the length of the weld can be very long. To remedy this problem, a dumping methodology is presented. The methodology still uses a thermo-mechanical approach, but the weld energy is dumped in the complete weld rather than applied incrementally. This paper presents the methodology in detail together with examples and comparisons in both welding and AM applications.

Ultra-high strength steel (UHSS) has become a common material in the automotive industry during t... more Ultra-high strength steel (UHSS) has become a common material in the automotive industry during the last decades. The technique of press hardening allows modifying and tailoring the material proper ...

Demanding needs on the production of advanced parts made of nickel-base superalloys are continuou... more Demanding needs on the production of advanced parts made of nickel-base superalloys are continuously increasing to meet the requirements of current environmental laws. The use of lightweight compon ...

Even though welding is a well-established production process in manufacturing industries and it h... more Even though welding is a well-established production process in manufacturing industries and it has a significant influence on the finished geometry as well as on the material properties of the processed part, it is still often neglected in the virtual process chain. In this contribution novel developments for the heat transfer solver in LS-DYNA ® are presented, which are designed to close this gap in the virtual process chain. In order to ensure a seamless data transition between stages without complex procedures, all new developments are applicable to solid and shell discretized geometries. First of all, the new keyword *BOUNDARY_THERMAL_WELD_TRAJECTORY is presented that provides an easy and flexible input structure for a heat source moving along a prescribed and, possibly, geometrically complex path for thermo-mechanically coupled and thermal only simulations. Due to high temperatures, temperature gradients and temperature rates present in welding applications, phase transformati...

A Complete and Rapid Simulation Method for Virtual Try-out of Stamping Dies Considering Elastic D... more A Complete and Rapid Simulation Method for Virtual Try-out of Stamping Dies Considering Elastic Deformations

Distortions and residual stresses developed during additive manufacturing (AM) might be so severe... more Distortions and residual stresses developed during additive manufacturing (AM) might be so severe that the design does not meet tolerance requirements or even cracks and fail. Predictions of such distortions and residual stresses by finite element analysis are therefore preferable performed early during the design development in order to reduce such problems. One approach for this kind of analysis is to apply techniques from welding simulations letting the Goldak heat source move over each layer of the material. However, this is computationally most costly and one might also argue how well this actually represent the AM process. We suggest to simplify this boundary condition to instead apply the heat layer-by-layer. We mean that this will represent the AM process as well as an approach of using the Goldak heat source and it is much more computational efficient than applying Goldaks heat source. The model is simply obtained by slicing the geometry in several layers using an in-house ...

$Research paper thumbnail of Predictionof damage and fracture during forming simulations in Alloy 718$

International Journal of Material Forming, 2021

The demands associated with the production of advanced parts made of nickel-base superalloys are ... more The demands associated with the production of advanced parts made of nickel-base superalloys are continuously increasing to meet the requirements of current environmental laws. The use of lightweight components in load-carrying aero-engine structures has the potential to significantly reduce fuel consumption and greenhouse gas emissions. Furthermore, the competitiveness of the aero-engine industry can benefit from reduced production costs and shorter development times while minimizing costly try-outs and increasing the efficiency of engines. The manufacturing process of aero-engine parts in superalloys at temperatures close to 950 °C produces reduced stamping force, residual stresses, and springback compared to traditional forming procedures occurring at room temperature. In this work, a hot forming procedure of a double-curved component in alloy 718 is studied. The mechanical properties of the material are determined between 20 and 1000 °C. The presence and nature of serrations in ...

The International Journal of Advanced Manufacturing Technology, 2020

The finite element method (FEM) has considerably contributed to the development of advanced manuf... more The finite element method (FEM) has considerably contributed to the development of advanced manufacturing methods for metal structures. The prediction of the final shape of a component is of great interest to the manufacturing industry. The level of demand may increase due to multistage processes. Therefore, including all steps of the manufacturing chain in the simulations is a key to being successful. This has been done for a long time in the stamping industry, which involves sequences of forming, trimming, and springback. However, more complex manufacturing procedures that include assembling of formed parts with forgings and castings via welding have been modelled with simplifications, resulting in a reduced prediction accuracy. In the present study, a double-curved part manufactured from alloy 718 is formed at 20 °C and laser-welded using the bead-on-plate procedure. The coupling of different manufacturing analyses, including cold forming, trimming, result mapping, welding, cooli...

$Research paper thumbnail of Damage and fracture during sheet-metal forming of alloy 718$