Material characterisation for forming technology

In addition to a structured approach to technical problems in general, this tutorial is intended to introduce participants with the topic of determining material parameters as input variables for the numerical simulation of forming processes in particular.

In the present era, numerical simulations are frequently employed in the design of forming processes. The quality of the simulation results is significantly influenced by the mechanical and tribological parameters which are imported into the simulation programs as input variables. This tutorial will present an overview of the current state of the art in the characterisation of mechanical material and tribological contact behaviour. The tutorial will address the determination of isotropic and kinematic hardening laws, isotropic and anisotropic yield criteria, stress and strain-based forming limits and the frictional behaviour between material and workpiece. Additionally, selected test methods will be demonstrated and analysed. At the final session of the tutorial, each participant will present one of the most important test methods for characterisation in a 10-minute presentation to the tutorial participants.

• Components of a material model for forming simulation
• Modelling and required characterisation of:

• Isotropic and kinematic hardening laws
• Isotropic and anisotropic yield criteria
• Forming limit curve
• Strain based failure criteria
• Friction model according to Coulomb, friction factor model and combined friction models

• Practical exercise:

• to obtain flow curves from force-displacement data of uniaxial tensile tests and initial dimension data of tensile test specimen
• to parameterise isotropic hardening laws
• to parameterise the material constants for anisotropic yield criteria according to the approach of Hill48
• to obtain forming limit curves from the optical measurement of the strain field using the Aramis software from Carl Zeiss GOM Metrology GmbH