Modeling of Cross Work Hardening and Apparent Normality Loss after Biaxial–Shear Loading Path Change

The specific loading-path change during sheet metal forming may lead to some abnormal deformation phenomena. Two-stage orthogonal loading paths without elastic unloading have revealed a phenomenon of apparent loss of normality, further modeled in the literature by non-normality theories. In this paper, a particular orthogonal strain-path change is investigated using the Teodosiu–Hu hardening rule within an associated plasticity framework. The results indicate that cross work-hardening has a significant contribution to the apparent loss of normality and subsequent asymmetric yield surface evolution. Detailed contributions of the model’s ingredients and features are clarified. The developed material model is intended for sheet metal forming simulation applications.

FORMING PROCESS SIMULATION OF BIMETALLIC BILLET BY EXTRUSION FOR REW METHOD

The bimetallic joining elements were designed for lap joints of thin metallic (Fe-Fe, Fe-Al) as well as metallic – nonmetallic (Fe-PMMA, Al-PMMA) sheets by Resistance Element Welding (REW). The Cu tubes with an outer diameter of 4 mm, wall thickness of 0.5 mm, and a length of 11 mm filled with a solder Sn60Pb40 were used for the bimetallic joining elements producing. The required shape of joining elements is obtained by cold forming. Simulation by ANSYS software was chosen for the optimization of the forming process and geometry of functional parts of the forming tool allowing to use only one extrusion forming operation. The simulation results are stresses, strains, and modification of cross-section geometry of elements for the three proposed forming modes. The geometry of functional parts of the forming tool was compared with the results of cross-section macroanalysis of joining elements.

Characterisation of the plane anisotropy and its effect on interstitial free steel thin sheet metal forming simulation

The main purpose of this paper is to study the orthotropic plastic behaviour of the cold-rolled interstitial free steel HC260Y when it is submitted to various loading directions under monotonic tests. The experimental database included tensile tests carried out on specimens (in the as-received condition and after undergoing an annealing heat treatment) cut in different orientations according to the rolling direction. A model was proposed, depending on a plasticity criterion, a hardening law and an evolution law, which takes into account the anisotropy of the material. To validate the proposed identification strategy, a comparison with the experimental results of the planar tension tests, carried out on specimens cut parallel to the rolling direction, was considered. The obtained results allowed the prediction of the behaviour of this material when it is subjected to other solicitations whether simple or compound.

Study on the Iterative Compensation Method for Continuous Varying Curvature Free Bending

The parts formed by the bending process not only have high precision of appearance dimension but also have good performance. In recent years, enterprises have put forward higher requirements for the forming process and product quality. Therefore, a new method for iterative compensation of bending springback with certain generality is proposed for continuous curvature bending. The purpose of this study is to take curvature as an iterative parameter and make the shape size reach the expected value through the finite compensation. On the basis of establishing this iterative compensation mechanism, the convergence of curvature iteration in the general free bending process is proved. The reliability of the proposed iterative compensation method in the bending process engineering application is verified by combining simulation with experiment. The two materials of 304 stainless steel and ST12 cold rolled steel were studied, and the two-dimensional plane stress-strain model Abaqus cantilever beam was established by using finite element software. The bending forming simulation was carried out based on the above iterative compensation mechanism. Finally, through the bending experiments of four models, the feasibility of the iterative compensation mechanism of curvature in the continuous curvature plane bending process is verified, and different models are selected to clarify that the method has the characteristics of generality, that is, it will greatly improve the flexibility of the bending process in industrial applications without the limitation of material types and mechanical models.

OPTIMIZATION OF THE FORMING PROCESS OF GUTTER END CAP USING THE FINITE ELEMENT METHOD

The contribution deals with the optimization of the forming process with the use of FE analysis. The impact of the planar anisotropy and friction coefficient on the drawing process was evaluated in the numerical simulation. Optimization of metal blank size and shape with the use of metal forming simulation was also performed. Studied material was galvanized drawing quality steel which is used for the production of the rain gutter end cap. Effects of planar anisotropy and friction coefficient on the quality of steel stamping were evaluated with the use of FE simulation. The effect of anisotropy was also experimentally tested. The aim of this work was to determine the correct steel blank size and shape and to evaluate the effects of planar anisotropy on the thickness variation and wall wrinkling.

BENDING SIMULATION OF PRE-GELLED COMPOSITES USING AN EXPLICIT COSSERAT CONTINUUM MODEL

Forming simulation of uncured pre-preg can be made more efficient with the use of dedicated finite elements tailored for soft, layered media. These elements are based on the Cosserat continuum theory that introduces a rotational degree of freedom at each node within standard solid elements. In this study, a Cosserat element is developed within a 2D non-linear explicit finite element framework that uses the Carrera Unified Formulation for its spatial discretization. Two benchmark case studies involving bending deformations are presented as the verification of the developed model. It is demonstrated that similar accuracy of predictions can be achieved with much coarser meshes of Cosserat elements than the equivalent classical finite element models consisting of multi-layer stacks of solid elements.

The Dahl’s Model for the Inelastic Bending Behavior of Textile Composite Preforms. Analysis of its Influence in Draping Simulation

Most of the numerical simulations of dry textile reinforcements forming are based on a macroscopic approach and continuous material models whose behavior is assumed to be elastic (linear or nonlinear). On the one hand, the experience shows that under loading/unloading stresses, residual inelastic deformations are observed. On the other hand, among the deformations that a woven reinforcement undergoes during forming, in most cases, only bending is subject to loading/unloading stresses. The first objective of this work is to highlight the inelastic bending behavior of textile reinforcements during a forming process and to find the possible origins of inelasticity. The second objective is to find the cases generating bending loading/unloading during forming as well as to study the influence of the bending inelasticity on forming simulation. For this purpose, the inelastic bending behavior was characterized by three-point bending tests. Then, the Dahl friction model was adapted to bending to describe the inelastic behavior. Finally, this model was implemented in a finite element code based on shell elements allowing the study of the influence of taking into account the inelastic behavior in bending on the numerical simulation of forming.

Topology Optimization and Lightweight Design of Stamping Dies for Forming Automobile Panels

The accurate prediction of deformation and stress distribution on the stamping die components is critical to guarantee structure reliability and lightweight design. This work aims to propose a new method based on numerical simulation for predicting die structural behaviors and reducing total weight. The sheet metal forming simulation was firstly conducted to obtain the accurate forming contact force during stamping process. The linear static structural analysis with different load cases was then performed to investigate the deformation and stress distribution on die structure. Topology optimization was employed to realize lightweight design while ensuring structural safety. Redesign process for die structures was conducted according to both manufacturing techniques and initial optimized results to guarantee the manufacturability of new structures. The proposed methodology has several advantages of decreasing model scale, precluding intricate contact condition settings as well as time-saving. A long beam stamping die used for forming automobile panels was selected to validate the proposed methodology, and around 18% weight reduction was achieved.