From Atoms to Autos - A new Design Paradigm Using Microstructure-Property Modeling Part 1: Monotonic Loading Conditions

Abstract

A multiscale analysis was performed to develop a macroscale microstructure-mechanical property model that includes several types of microstructural inclusions found in an A356-T6 cast aluminum alloy for use in automotive chassis component design. This microstructureproperty model can be used for finite element analysis in which the deformation history, temperature dependence, and strain rate dependence vary. To capture the history effects from the boundary conditions and load histories, the microstructural defects and progression of damage from these defects and microstructural features such as casting porosity, silicon particles, and intermetallics must be reflected in the model. Internal state variables are used in the material model to reflect void/crack nucleation, void growth, and void coalescence from the casting microstructural features under different temperatures, strain rates, and deformation paths. Furthermore, internal state variables are used to reflect the dislocation density evolution that affects the work hardening rate and thus stress state under different temperatures and strain rates. In order to determine the pertinent effects of the microstructural features, several different length scale analyses were performed. Once the pertinent microstructural features were determined and included in the microstructure-mechanical property model, tests were performed on a control arm to validate its precision. Very encouraging results were demonstrated when using the model for optimizing structural components in a predictive fashion. EXECUTIVE SUMMARYIn designing a structural component, a failure analysis will typically include a finite element analysis and microstructural evalutation. Sometimes the microstructural evalution will quantify the inclusion content (source of damage in a component) in a prioritized fashion differently than the finite element analysis. Let us consider the hypothetical situation exemplified in Figure 1.Here we have an automotive control arm that shows that has undergone certain boundary conditions in a finite element analysis. The finite element analysis revealed that the highest Mises stress occurred at point D. For the different regions of interest, microstructural analysis using optical imaging revealed the largest defect occurred at point B. Both camps would argue about the location of final failure. However, in our hypothetical example, both are wrong, because the final failure state is both a function of the initial inclusion state and boundary conditions. As such, point A failed first. The key is the development of the microstructureproperty model that can be included in a finite element analysis, which includes the inclusion content (or the sources of damage progression). IIIn order to accomplish such a task, a multiscale analysis was performed with a focus on a macroscale microstructure-mechanical property model that includes several types of microstructural inclusions found in an A356-T6 cast aluminum alloy for use in automotive chassis component design. This...

A design-centered approach in developing Al-Si-based light-weight alloys with enhanced fatigue life and strength

“…[2][3][4] demonstrates that the incubation fatigue life is inversely related to the second-phase hard particle size when the amplitude of applied stress is lower than macroscopic yielding. Experimental results [1] also show that the larger the dendrite cell size the lower the fatigue life. On the other hand, the studies in Ref.…”

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“…The experimental results [1][2][3][4] reveal that both the size of dendrite cells and segregated silicon particles have strong effects on the alloy's mechanical behavior. It is found that fatigue cracking usually commences along the boundary between large silicon particles and alloy matrix.…”

Finite Element Analysis of Self-Pierce Riveting in Magnesium Alloys Sheets

“…C 17 Constant term in R s (T) equation which describes the isotropic static recovery (units=1/(MPa sec))…”

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