Case study on the influence of kinematic hardening within a parameter-free and non-invasive form finding approach

Philipp Landkammer,Paul Steinmann

doi:10.1051/matecconf/20168011007

Abstract

Inverse form finding – as a type of shape optimization – aims in determining the optimal preform design of a workpiece for a specific forming process, whereby the desired target geometry is known. Recently, a novel parameter-free and heuristic approach was developed to tackle this nonlinear optimization problem. Benchmark tests already delivered promising results. As a particular note-worthy feature of the approach, a coupling to an arbitrary finite element software is feasible in a non-invasive fashion. The aim of this contribution is to investigate the effect of kinematic hardening and cyclic loading on the convergence behavior of the algorithm.

Highlights

Introduction and related worksWithin the metal forming industry, trial-and-error methods of earlier days have since long been replaced by simulative predictions and simulation based optimization strategies
Thereby, the main issue of optimization, besides the inverse problem of parameter identification, is the determination of an optimal tool and workpiece design, see Chenot et al [2]. The latter constitutes the investigated type of optimization in this contribution and is frequently denoted as inverse form finding. It aims in determining the optimal preform design of a workpiece for a specific forming process, whereby the desired target shape is known a priori
In the context of sheet and bulk metal forming, or forging respectively, several concepts have been developed since decades to solve this non-linear optimization problem

Summary

Introduction and related works

Within the metal forming industry, trial-and-error methods of earlier days have since long been replaced by simulative predictions and simulation based optimization strategies. Thereby, the main issue of optimization, besides the inverse problem of parameter identification, is the determination of an optimal tool and workpiece design, see Chenot et al [2] The latter constitutes the investigated type of optimization in this contribution and is frequently denoted as inverse form finding. Since path-dependency is occurring in plasticity, a similar iterative procedure of all shape optimization approaches can be recognized It consists of updating the geometry of the material space, before re-starting a new simulation and comparing again the forming results of the spatial space to the desired target shape. The main goal of this contribution is to evaluate, whether a sophisticated hardening model or cyclic loading with reverse strain path changes affect the convergence behavior This is realized by a case study with computational examples.

Functional principle of the iterative update procedure

Example

The material model of DP600 steel with isotropic and kinematic hardening

Simulation

Optimization

Conclusion