The mechanical properties of polymers, particularly as a function of temperature and strain rate, are key for implementation of these materials in design. In this paper, the compressive response of low density polyethylene (LDPE) was investigated across a range of strain rates and temperatures. The mechanical response was found to be temperature and strain rate dependent, showing an increase in stress with increasing strain rate or decreasing temperature. A single linear dependence was observed for flow stress on temperature and log strain rate over the full range of conditions investigated. The temperature and strain rate data were mapped using the method developed by Siviour et al. based on time-temperature superposition using a single mapping parameter indicating that there are no phase transitions over the rates and temperatures investigated. Taylor impact experiments were conducted showing a double deformation zone and yield strength measurements in agreement with compression experiments.

No abstract

5083 aluminum alloy is a light-weight and strain-hardened material used in high strain-rate applications such as those experienced under shock loading. Symmetric real-time (in situ) and end-state (ex situ recovery) plate impact shock experiments were conducted to study the spall response and the effects of microstructure on the spall properties of both 5083-H321 and 5083-ECAE ? 30 % cold-rolled (CR) aluminum alloys shock loaded to approximately 1.46 GPa (*0.2 km/s) and 2.96 GPa (*0.4 km/s). The results show that mechanically processing the 5083-H321 aluminum by Equal Channel Angular Extrusion (ECAE), followed by subsequent CR significantly increases the Hugoniot Elastic Limit (HEL) by 78 %. However, this significant increase in HEL was at the expense of spall strength. The spall strength of the 5083-ECAE ? 30 % CR aluminum dropped by 37 and 23 % when compared to their 5083-H321 aluminum counterpart at shock stresses of approximately 1.46 and 2.96 GPa respectively. This reduction in spall strength is attributed to the cracking and re-alignment of the manganese (Mn)-iron (Fe) rich second phase intermetallic particles during mechanical processing (i.e., ECAE and subsequent CR), which are consequently favorable to spallation.

No abstract

Abstract. The effects of microstructure on the spall properties of two magnesium alloys fabricated via Equal-Channel Angular Extrusion (ECAE) and Spinning Water Atomization Process (SWAP) were investigated. The Hugoniot Elastic Limit (HEL) for both AZ31B-4E and AMX602 magnesium alloys were found to be approximately 0.181±0.003 GPa and 0.187±0.012 GPa, respectively. The spall strengths extracted from the free surface velocity profiles were found to decrease by approximately 4% for AZ31B-4E between 1.7 GPa to 4.6 GPa shock stress. Although this reduction in spall strength may lie within the experimental error, the microstructure of the post-shocked magnesium alloy show that manganese intermetallic inclusions in the AZ31B-4E magnesium were perhaps responsible for the reduction in spall strength as a function of shock stress. On the contrary, the spall strength for AMX602 was found to be random for the same shock stress range studied. This random behavior of the AMX602 was likely due to the incomplete sintering during mechanical processing. The fracture surfaces of both materials were dominated by nanovoids and the AMX602 fracture surface was found to be striated. A more in-depth study is needed to better understand the spall behavior of both materials.