School of Mechanical, Electrical and Manufacturing Engineering


10 December 2019

Improving sheet steel ductility for automotive fabrication processes

Presented By Dr David Collins, University of Birmingham
  • 2.30 - 3.30 pm
  • Room TW.2.10, Wolfson Building

About this event


The geometric complexity of an automotive component fabricated from a metallic sheet is largely limited by the ductility of the material used. Gains in ductility are possible using so-called non-proportional strain-paths, whereby the material undergoes a prescribed pre-strain prior to further plastic deformation but with a different strain ratio. To elucidate this effect, a combination of high energy synchrotron diffraction and finite element crystal plasticity modelling was used. The diffraction study was performed in-situ, to observe the deformation of automotive-grade sheet ferritic steel along different non-proportional strain-paths. To accurately replicate a real manufacturing process, a bespoke biaxial loading mechanism was designed and built; capable of accessing arbitrary non-proportional strain-paths. By collecting the full Debye-Scherrer diffraction geometry using an area detector, temporally resolved lattice strain distributions were obtained across a wide range of crystal orientations within the plane of the sheet. Texture was also inferred via changes in the measured reflection intensity. The results are providing new and exciting insights into the micromechanical response of complex strain-paths, whilst also informing and calibrating the dislocation hardening rules employed in crystal plasticity models.



David Collins is a Birmingham Fellow and Lecturer in the School of Metallurgy & Materials, University of Birmingham. He joined Birmingham in 2017 having been a Research Fellow at University of Oxford since 2012. Prior to this he completed his PhD at University of Cambridge and MEng at Imperial College London, both in Materials Science. His research interests focus on manufacturing and processing methods related to advanced metal forming technologies with an interest in aerospace and automotive applications. David’s expertise is in physical metallurgy - incorporating the science that underpins metallic material behaviour. This includes deformation mechanics & microstructure/phase evolution, with many of his studies using state-of-the art in-situ synchrotron X-ray and neutron diffraction experimental methods. Along with electron microscopy characterisation and modelling methods, David’s studies target understanding at the crystal level to interpret, manipulate and exploit the material behaviour to improve performance at the component level.


Liguo Zhao

Wolfson School of Mechanical, Electrical and Manufacturing Engineering