This Grant Opportunity for Academic Liaison with Industry (GOALI) provides funding for the development and validation of a novel computational tool for modeling high-rate deformation and failure of magnesium alloys. A multi-scale approach will be used for describing the effects of grain level deformation mechanisms on damage and failure at a structural level. The framework that will be used is that of polycrystalline plasticity and non-linear homogenization. Focus will be on the improved modeling of the plastic properties specific to magnesium alloys, namely tension-compression asymmetry associated to twinning, anisotropy, and its evolution with increasing strain rate. In partnership with General Motors, a multi-scale experimental verification and validation of the new theory for both quasi-static and dynamic regimes will be conducted by performing material characterization, fracture tests, and crush tests over a range of loadings and strain rates, as well as gathering micro-structural information at key stages of the fracture process.
If successful, the results of this research will address important strategic needs of the US automotive industry for increased use of lightweight materials such as magnesium alloys in body structures. Environmental benefits are also anticipated through increased fuel-efficiency associated with the reduction in weight of the transportation vehicles. The application of the models will allow the designer to assess the behavior of a given alloy during the finite element analysis phase of the design process. Furthermore, it will allow numerical testing of the performance of components in crash situations both in terms of energy absorption and ability to retain structural integrity, with direct impact on the safety, quality, and environmental friendliness of the cars of the future.
We identified the key material characteristics that will allow for the use of magnesium in some structural automotive components and not in others, with direct impact on the safety, quality, and environmental friendliness of the cars of the future. Furthermore, the research provides guidelines for design of new materials (i.e. more suitable than existing Mg alloys) for automotive applications. Broader Impacts: Societal: The research conducted has allowed to uncover that commercially available Mg alloys should not be used for certain automotive applications due to their limited ability to absorb energy. Specifically, the model developed as part of this research predicts that in axial crushing Mg alloys display unusual buckling, and as such should not be used for structural parts that may experience impact loadings. Educational: Three graduate students have been involved in the research and are first author or co-authors of eight archival papers. One of the graduate students has completed his PhD dissertation that was defended in May 2014. He has also worked with the industrial partner during research visits and a summer internship with GM. A graduate course, in the area of computational plasticity, based on the research from the new advanced materials investigated as part of this grant was taught through long-distance outreach program at Univ of Florida and thus made available to engineers engaged in research in the state of Florida. Intellectual Merit: Major findings from this work include enabling further understanding of ductile damage in Mg; development of a new model for damage; with applications to crashworthiness and impact behavior.
