M. Vaz

A computational approach to blanking processes

Abstract The present work presents a general framework for numerical simulation of blanking processes using finite elements. Blanking consists of a metal forming operation characterised by complete material separation. Experimental observations show that the shear process occurs in three stages: contact engaging, penetration/plastic deformation and rupture. In the first and second stages, large plastic deformation takes place, being primarily affected by punch displacement and clearance between punch and die. In the third stage, catastrophic failure occurs, leading to a complete material separation. A numerical approach to the problem requires a comprehensive finite element modelling due to the diversity of physical phenomena involved, such as large plastic deformation, material failure and coupled heat transfer. Furthermore, use of error estimation and re-meshing procedures is highly recommended due to element distortion, caused by lager deformation. This work discusses some of the issues involved in blanking modelling and analyses the influence of the clearance in stress distribution prior to material separation.

A Study on the Coupled Thermal and Damage Effects in Deforming Solids

Mechanical degradation and ductile failure in metal forming operations can be successfully modelled using fully coupled damage models. In addition, it has been largely reported in the literature that temperature variations affect material behaviour, especially thermal softening. This paper presents a numerical discussion of the coupled effects between ductile damage and temperature evolution based on the simulation of tensile tests of notched specimens.

Thermo-Mechanical Coupled Problems at Finite Strains

This paper discusses some thermodynamic aspects in association with a large strain/large displacement elastic-plastic formulation aiming at application to metal forming problems. The mechanical solution adopts the multiplicative decomposition of the gradient of deformation into elastic, plastic and thermal components. The approach is illustrated by analysing the thermal effects in the plastic deformation of low-carbon steel specimens subject to tensile loading.

Flux Evaluation in Anisotropic Heat Conduction Using the Modified Local Green’s Function Method (MLGFM): Comparative Studies

The Modified Local Green’s Function Method (MLGFM) is an integral method which uses appropriately chosen Green’s function projections obtained numerically with the aid of auxiliary finite element problems. Its applicability includes those cases for which a fundamental solution does not exist or is very cumbersome. The MLGFM was studied intensely in the 90´s with promising results, especially for tractions and heat fluxes at the boundaries. The present contribution compares this method for heat flux evaluation in anisotropic media with finite volumes and finite elements. The latter approximates heat fluxes using a superconvergent patch recovery scheme, whereas the former computes flux quantities directly at nodes. The numerical example uses linear elements and includes non-homogeneous temperature and flux boundary conditions.