Key Engineering Materials Vols. 611-612

Abstract: The paper investigates the computational efficiency of explicit and implicit integrationschemes for hyperelastic-plastic combined hardening plasticity and examines the influence on thesimulated springback in sheet metal forming. The finite strain combined hardening model discussedhere is integrated by means of the exponential map algorithm in order to fulfil plastic incompressibility.The focus is on different possibilities of evaluating the exponential tensor functions of thematerial model. One option is to use the spectral decomposition to evaluate the exponential tensorfunctions in closed form. Alternatively, the latter functions can be determined by Taylor series expansion.We examine the potential of an explicit formulation of elastoplasticity with combined hardeningwith respect to accuracy and efficiency. The material model equations have been implemented as usermaterial subroutines UMAT and VUMAT for use in the commercial solvers ABAQUS/Standard andABAQUS/Explicit, respectively, where the finite element simulation of draw bending is simulatedboth in implicit and explicit manner.

Abstract: Simulation tools have been effectively employed in many applications for numerically investigate on the development of efficient production processes aiming to materials quality enhancement. Such studies allow drastically reduction of the number of experimental tests and consequently of the development costs and further of the time-to-market. In this framework, the present paper focuses on the study of filling rate and of the solidification times of Titanium alloys. Starting from some acquired experimental data, considering appropriate boundary conditions and properly setting of the external parameters (flow-rate, liquid temperature, etc.), the study targets optimizing the processing cycle and reducing the presence of defects in casting. The cast tree used for the research is a symmetric one, including two samples used for Charpy impact tests and two samples for tensile tests. The considered commercial software provides a complete finite element solution and has been employed facilitating to prevent casting defects. During the simulations, the process parameters and the alloy properties have been explicitly taken into account. Information about how the parameters should be modified to achieve the optimal conditions close to a defects-free castings was achieved. A good correlation, in terms of microstructural analysis, between the simulation data and the experimentally obtained results was obtained, confirming the reliability of the model.