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Title: Relationship between the metallurgical properties and crash performance of automotive structures
Author: Beynon, N. D.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2005
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Work was undertaken to establish whether microstructural changes during high-speed deformation could explain the inferior crash performance of mild steel compared to carbon-manganese grades, which in turn are deemed inferior to dual phase steel grades. This thesis correlates the relationship between the mechanical properties of commercial sheet steel and crashworthiness of steel structures. In order to deliver the correlation a research project was undertaken that included quasi-static tensile testing and dynamic tensile testing, following by a study of box section testing using quasi-static crush testing and dynamic axial impact testing. The results of the present study identified that the dual phase steel grades with the lowest volume fraction of additional non-martensitic second phase constituents, displayed an increase in energy absorbed, as strain rate increases, that appears to be linear up to and including 100s-1 strain rate. Finally, this study involved the production of dual phase microstructures in low carbon strip steels, via a modified steel-processing route, with the subsequent determination of the dynamic properties of the strip steels. Two dual phase commercial trial grades with compositions 0.094%C-0.155%Si-1.48%Mn-0.96%V and 0.096%C-0.13%Si-1.15%Mn-0.096%V respectively, were studied. The results showed that the yield/proof strength and tensile strength increased with increasing volume fraction of martensite and increasing strain rate. Steels with a predominantly ferrite-martensite microstructure showed improved performance, in terms of the strain rate sensitivity and work hardening properties up to strain levels of 10% compared with microstructures with additional non-equilibrium constituents, characterised mainly as bainite.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Eng.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available