Symposium Poster v1

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Transcript of Symposium Poster v1

  1. 1. Investigating the Role of Stress Triaxiality in High Strain Rate Behavior of an AZ31 Magnesium Alloy Brian Chang, Mechanical Engineering Mentor: Dr. Kiran Solanki, Assistant Professor Schools of Mater, Transport, and Energy ResultsTesting Medium notch rolling direction 10-3 s-1 Pure tension rolling direction 103 s-1 Medium notch rolling direction 103 s-1 Figure 1: Schematic of a tensile SHPB Figure 3. A) Schematic of a notched and B) pure tensile specimen A B A B Figure 4. A) SHPB apparatus at Dr. Solankis Lab at ASU B) the striker prior to impact The split Hopkinson pressure bar (Figure 4A) is used to calculate the force and displacement of a specimen during high rate loading. The specimen is threaded between the two bars where, during loading, a striker impacts the end of the incident bar creating a stress wave. For this project, we used three distinct types of specimens a pure tension (Figure 3B) and three notch (Figure 3A) specimens of varying notch diameter (Table 1). High strain rate tensile testing was performed using Bridgeman notch specimens to vary the stress triaxiality and to investigate stress- state effects on the high strain rate behavior of an AZ31 magnesium alloy. Introduction Fig. 5 The SEM images above show the fracture surfaces of the specimens after mechanical testing. (A1-3) The fracture surface of the pure tension specimen shows uniform ductile failure with slight directionality indicative of twinning. (B1) Twinning is more evident in the fracture surface and can be seen in the sigmoidal shape of the stress-strain curve. (B2) Flat areas indicate formation of microcracks likely brought about by twinning. (B3) Pores indicate a degree of ductility. (C1) Directionality indicates twinning. (C2) Dimpled surface indicates ductile failure. A1 B2B1 A3A2 C2C1 B3 Applications This research will result in a greater understanding of the failure properties of components under extreme environment (crash). This will pave the way for further research and improvements of structural components. As a result, it will benefit the environment as well as the general public as fewer emissions will be generated from lighter weight, more fuel efficient vehicles. Small Notch 0.8 mm Medium Notch 1.2 mm Large Notch 2.4 mm 0 200 400 600 800 1000 0 0.05 0.1 0.15 0.2 Force Displacement Medium B Specimens Quasistatic High Strain Rate Pure Tension