Modelling the deformation and failure of sheet metal in high-strain rate forming

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The manufacture of lightweight and crash-resistant passenger vehicles increasingly requires the use of difficult-to-form sheet materials. Lightweight materials such as advanced high strength steels, aluminum and magnesium alloys inherently have limited formability when shaped using conventional forming processes. However, high-strain rate forming technologies, such as electromagnetic and electrohydraulic forming have been developed because under specific conditions, sheet materials can achieve at least 100% increase in formability. This enhanced formability offers significant weight reduction opportunities to automotive part designers.******In order to optimize these high-strain rate metal forming processes and render them as cost-effective as possible for industrial implementation, it is necessary to be able to numerically predict their outcome with a high degree of confidence. The applicant's prior research focused on developing computer models that can simulate electrohydraulic forming operations. However, significant work is still required in order to improve the accuracy of the simulations.******This research program aims to improve the existing simulation models in such a way as to more accurately predict the deformation behaviour and the onset of fracture of sheet materials deformed at high-strain rates. It is proposed to conduct a series of mechanical tests on sheet specimens across a range of strain rates from 0.001 to 1000 s-1. The use of high-speed, high-resolution digital cameras during testing will facilitate the acquisition of experimental data that gives insights into material behaviour and help to develop more accurate simulation models. One of the novelties of this work will be to determine the fracture limits of sheet materials at high strain rate.******It is also proposed that specimens be observed at different magnifications under the microscope in order to determine their micro-mechanical deformation and damage behaviour up to the onset of fracture. Again, simulation models will be developed that are able to predict the onset of fracture based on observed micro-mechanisms of deformation and failure. ******This research program will provide advanced training for four highly qualified personnel (two Master's degree students and two PhD students) and will lead to the development of more accurate numerical tools for the simulation of high-strain rate sheet metal forming processes. These models will also be very useful in predicting the crashworthiness of vehicles. This will also help to accelerate the adoption of high-strain rate forming processes into industrial practice and increase the use of lightweight sheet materials in automobiles. Furthermore, as the trainees in this research program are hired by Canadian automotive manufacturers, the expertise they will develop will contribute toward maintaining Canada's competitive edge in advanced manufacturing.