International Journal of Material Forming

The fundamental mechanical formulation is recalled for simulation of metal forming processes. The basic principles of 3-dimensional finite element discretization and of time integration are summarized. Several important numerical developments for efficient computation of large plastic deformation are briefly described. Various fields of applications to real processes are reviewed. Illustrative examples are mentioned to show the utilization of the commercial computer code Forge3 in industry, as a very flexible tool to design metal forming sequences.

The grain refinement technology is important in improving the metallic material properties without the requirement of additional alloy elements. Previously, we developed an efficient method for producing ultrafine-grained steel strips using a combination of cutting and heat treatment. However, the effect of cutting on recrystallization was not apparent. The objective of this study is to investigate the effects of metal cutting on static recrystallization and outline its advantages in grain refinement using numerical simulations based on the crystal plasticity theory. Simulation results show that shear deformation in metal cutting activates more slip systems than plane strain compression via rolling, even when considering the same equivalent plastic strain. The geometrically necessary dislocations are assumed to accumulate in the crystal because many slip systems are activated in shear deformation and improve grain refinement via static recrystallization in the subsequent heat treatment. This result indicates that the deformation type plays an important role in the recrystallization process. Thus, cutting is more efficient than rolling for the production of ultrafine-grained steel.

Selective Laser Sintering (SLS) is a manufacturing method which has existed since the 1990s. It was initially limited to manufacturing prototypes as it does not require any other tooling than the laser sintering machine to manufacture the part. For several years now, the use of this process has extended to manufacturing of real parts. This article presents an analysis carried out to better understand the advantages and drawbacks of SLS for Rapid Manufacturing. The influence of the various parameters linked with the manufacturing process on the final quality of parts was assessed. We then assisted industrial partners in using this manufacturing method for their own production. The aspects studied are: product design, its qualification and finally support in industrialisation.

Nowadays, manufacturers of clips have to face dimensional problems of their products which are heat treated. By using the numerical approach, companies want to understand reasons of these deformations. Thanks to the modeling of the shaping operation, we obtain the shape and residual stresses of the clip ready for heat treatment. After to have identify thermomecanic parameters used by FORGE2005®TTT on a specific test bench called TABOO, we study the quenching and heating operations. We can so notice that geometrical evolutions are mainly due to residual stresses of bending.

The EMF process is a deformation process at high speed, which involves coupled electromagnetic, mechanical and thermal problems. Due to the complexity of these couplings, the simulation of the process via FEM is a not a straightforward question. Nowadays the few commercial softwares that are able to simulate the multiphysics problem show certain limitations. That is why we propose a new simulation approach that solves the above mentioned limitations while maintaining a good correlation with the experimental results. The first part of the paper will describe our new approach based on the softwares Maxwell 3D® and Pam-Stamp2G®, and compare its results with the ones obtained with an automatic coupling of two commercial softwares (SysMagna® and Pam-Stamp2G®). The second part of the paper will show the comparison between the results of the new approach and the experimental ones, and the benefits of it for an industrial use.

This paper presents an analysis of an advanced squeeze casting process suitable for the manufacturing of high performance industrial components more quickly and cheaply. After short description of the process some produced components are considered. The components, in A356 and A380 alloys, have been T6 heat treated and their soundness has been certified by non destructive tests. Standard samples for impact test, as well as for fracture rupture strength have been machined directly from the previous components. After the execution of the tests the fracture surface of samples has been observed by SEM in order to analyze details and to evaluate the influence of the process and of the alloy on the fracture behaviour. On polished transverse sections of samples the microstructure of the alloy has been observed, highlighting the presence of very small and uniformly distributed intermetallic particles in a mainly globular shaped microstructure as expression of the attained semi-solid conditions during the process.

Previous results, obtained using the load-scanning technique, indicate that the amount of plastic deformation of the contact surface contributes to a change in the global friction coefficient. This technique allows describing the friction from a local analysis method, since the normal and tangential contact forces to the sliding direction can be measured simultaneously, independently and precisely. It also allows maintaining a constant contact surface geometry [1]. In this paper the load-scanning results are analysed using the finite element method (FEM), which allows a local analysis to advance their understanding. The numerical study is performed applying the Amontons-Coulomb friction model in the simulation of local contact conditions, in order to determine the normal load value that dictates the transition between elastic and elastoplastic contact. The numerical model considers the contact between a rigid sphere and a deformable body. The study focuses on the influence of elastoplastic mechanical properties of the deformable body, namely, the hardening coefficient and the Poisson ratio, in the normal load corresponding to the onset of plastic strain.

Meshless methods, that appeared in the early nineties, constitute nowadays an appealing method for the simulation of forming processes. In this review we revisit the basic ingredients of the most common of such methods, by analyzing their theoretical foundations, applicability and limitations, and give some examples of performance to show the wide variety of situations in which they can be employed.

This study deals with the calibration of Bauschinger effect on DP980 and TRIP1180 sheet metals with three cyclic material tests: tension/compression, shear/reverse shear, and bending/reverse bending. An in-plane simple shear jig, in which the grip bolts are evenly positioned surrounding a specimen to prevent the specimen from slipping, is developed for shear/reverse shear test. A new concept of electronic bending/reverse bending tester, which operates on brushless DC motor and can be speed-controlled, is designed for bending/reverse bending tests. In the newly devised bending/reverse bending test, the gaps between specimen and grip make the specimen deform like pure bending with only four points touching. The material parameters of Yoshida-Uemori (YU) model are determined from tension/compression, shear/reverse shear, and bending/reverse bending tests. The calibrated material properties for the Bauschinger effect are verified with the application for U-draw bending test. The springback prediction results based on the three loading/reverse loading tests are comparatively evaluated with various blank holding forces.