High Strain Rate Dynamic Deformation of ADI

Engineering materials used in numerous applications, particularly in automotive crash loading and military ballistic purposes have to meet new demands, one of which is the resistance to dynamic loading. As the phenomena associated with such interaction is rather complex, non-static types of tests are applied to evaluate and compare between different potential materials. In this Work, different grades of ADI were produced under different austenitizing and austempering conditions different ausferrite morphologies. The effect of alloying elements such as Cu and Mo on the initial microstructure of the ductile iron was also studied. The initial amount of retained austenite was subjected to different dynamic strain rates. The hardness and strain induced martensitic transformation as a function of the microstructure and strain rate were evaluated. Extensive use of XRD and SEM was made to evaluate the high strain rate properties of the investigated grades.

Implementation of a Constitutive Model for the Mechanical Behavior of TWIP Steels and Validation Simulations

High manganese content TWinning Induced Plasticity (TWIP) steels are promising for the production of lightweight components due to their high strength combined with extreme ductility, see [1]. This paper deals with the implementation of a constitutive model for the macroscopic deformation behavior of TWIP steels under mechanical loading with the aim of simulating metal forming processes and representing the behavior of TWIP-steel components – for example under crash loading - with the Finite Element code LS-DYNA®and refers to our recently published papers: [2],[4],[5]. Within the present paper we focus on the implementation of the model formulated in [2] and its extension to stress dependent twinning effects.

Crashworthiness Optimization for a Two-Layered Front Rail Considering Front Oblique Impact

This paper is concerned with the crashworthiness design of the front rail on a vehicle chassis frame structure considering uncertain crash directions. The front rail, as a typical thin-walled structure, is sensitive to the loading direction for crashworthiness requirements. Multi-step multi-domain optimization method was applied to obtain a new single-layered front rail (SFR) which has better adaptability to crash loading directions. To further improve the front rail crashworthiness, a two-layered front rail (TFR) is proposed. Response surface method is conducted to pursue the optimal thickness pair of the two-layered front rail. Numerical simulations are carried out with Altair/Hypermesh and LS-DYNA to compare the crashworthiness performances of the standard rectangle front rail, SFR and TFR. The results show that TFR keeps the same adaptability of loading directions as SFR meanwhile it can absorb more crash energy during front angle impacts.