SAE 2014 World Congress & Exhibition

Technical Session Schedule

Tuesday, April 8

Chat with the Experts: Integration of High Strength and High Ductility Metals for Light Weight Automotive Applications
(Session Code: MCHAT)

Room 330 A/B  4:00 p.m.

The ability to create structural materials of high yield strength and yet high ductility has been a dream for materials scientists for a long time. The study of the mechanical behavior of the surface nanostructured materials using SMAT (Surface Mechanical Attrition Treatment) shows significant enhancements in mechanical properties of the nanostructured surface layer in different materials. We summarize our recent works on the advanced metallic nanomaterials with exceptional dual mechanical properties using multiscale metallurgical structure-driven design combined with advanced mechanical simulation. The effect of surface nanostructures on the mechanical behavior and on the failure mechanism of metallic material shows the possibility to develop a new strength gradient composite. The results show three key mechanisms for the enhancement and the extraordinary properties of layered and nanostructured metallic stainless steel sheet. The computational models and experimental results successfully provide valuable information about the nanomaterials properties as a function nanostructure configuration (nanograins and nanotwins). The processing of nanomaterials using mechanical processing and heat treatment have been studied at nanoscale and atomic scale. With a detailed knowledge of the processing using high speed camera, we were able to accurately estimate the strain rate at different depths by analytical modeling and to study the correlation between the resulting microstructures and the strain/strain rate history of the material. The material studies using nanomechanics based experimental investigations (nanoindentation and nano-pillar tests) can reveal the effects of the atomic structure and nanostructure gradient on the mechanical behaviors. The failure mechanisms studies at nano-, micro- and macroscopic scale can provide efficient ways to enhance the ductility of materials using the general approach of non localization. The potential applications for automotive industry will be shown. The delay fracture of nanostructural TWIP steels and associated technological challenges will be addressed and we will show the possible technical solutions. We will also present two design examples for the integration advanced nanosteels for the crash box and roof. Finally other potential materials such as nanostructured Mg alloys and advanced design solution with lattice structure will be introduced.

Presenters - Jian Lu, City Univ. of Hong Kong