冰在低温下的单轴压缩力学行为和破坏机制

In adverse weather conditions,hailstone impact is a serious threat to the integrity of aircraft structures.The U.S.ASTM-F320-1994 standard has provided a detailed method for simulating the impact of hailstone on aircraft by throwing ice balls.Therefore,the mechanical properties of ice under low temperature,high strain rate and their coupling effect have received widespread attention.In the present study,by using an Instron 5848 material testing machine and a split Hopkinson pressure bar (SHPB) with cooling chambers,a series of uniaxial compression tests were carried out to explore the mechanical behaviors and failure mechanism of polycrystalline ice at the temperatures of -10 ℃,-20 ℃ and -30 ℃,and at the strain rates in the range of 10^-4 s^-1 to 10² s^-1.Based on the waveform shaper technology,the stress equilibrium and an approximately constant strain rate in the ice samples were achieved during the dynamic loading process.Meanwhile,the reliability and effectiveness of the experimental results were examined carefully.The experimental results show as follows.The compressive strength of ice is highly sensitive to both temperature and strain rate.In particular,the compressive strength of ice increases with the increase in strain rate and the decrease in temperature.Moreover,there exists a linear relationship between the compressive strength and the logarithm of strain rate.In addition,we found that the increase of strain rate enhances the strengthening effect of the compressive strength due to the decrease in temperature.Within the studied strain rate and temperature scope,the ice mainly has three types of failure modes,namely expansion,longitudinal splitting and holistic crushing.It has been found through analysis that the change in the failure mode of ice is probably due to two reasons:the inner stress release rate during microcrack nucleation and propagation,and the variation of the hydrogen bond strength.