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- 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