悬挂靶板在高速弹丸冲击下的运动

为研究航天器外挂设备受到微流星或空间碎片的高速撞击后产生的运动规律和物理现象，通过将航天器外挂设备（太阳能帆板或天线等）模拟为简单悬挂板，得到悬挂板扬角与撞击速度、弹丸直径、材料屈服强度及悬挂板厚度之间的关系曲线。结果表明在特定条件下悬挂板并沿着弹丸运动方向上扬而是朝反方向做上扬运动，悬挂板朝弹丸运动方向的上扬角是有限的，相反其反向扬角在特定条件下无限制增长。     

Dynamic mechanical behavior and microstructural evolution of the Al-6Mg alloy subjected to three treatment conditions

The mechanical properties of Al-6Mg alloy with three treatment states (H112, O and cold-extruded states) were investigated at room and high temperatures using an INSTRON machine and a Split Hopkinson Pressure Bar (SHPB). Stress-strain curves of the alloy with different processes were obtained at a quasi-static strain rate of 5×10-4 s-1and dynamic strain rates of 1 400-4 200 s-1, respectively. The results suggest that, at room temperature, the three processed Al-6Mg alloys are all low sensitive to strain rate. The O state Al-6Mg alloy (Al-6Mg-O) exhibits the most ductility, while the cold-extruded Al-6Mg alloy (Al-6Mg-C) displays the highest strength. At elevated temperatures, the yield stresses and the differences in yield stress of the three processed alloys all decrease with increasing temperature under the quasi-static strain rate of 5×10-4 s-1. Based on test results, modified Johnson-Cook (JC) constitutive models for the three processed Al-6Mg alloys were developed. The microstructures before and after deformation were examined by electron backscattered diffraction (EBSD) and further dynamic recrystallization (DRX) at the strain rate of 3 300 s-1 was discussed.     

橡胶夹布膜片损伤声发射信号的小波识别

橡胶夹布膜片在安装过程中,因材料性能和安装因素,都会导致膜片的内部损伤,包括内部纤维的断裂、橡胶的剪切破坏。利用刀片在钢板上的摩擦来模拟密封过程中的部件摩擦,用刀片划割橡胶膜片导致膜片纤维断裂和膜片剪切破坏来模拟在膜片安装过程中橡胶膜片的损伤。通过声发射检测获得了两种情况下的声发射典型信号,并利用小波变换,对信号进行了时频域分析。结果表明这两种情况下的声发射信号在特定的连续小波变换下,在频率分布、能量分布、持续时间等方面具有明显的不同特征,可以利用这些特征对含纤维橡胶膜片在安装和使用过程中的损伤模式进行识别。     

超高速撞击丝网防护屏弹丸形状效应数值模拟研究

采用数值仿真方法研究不同形状弹丸撞击连续型防护屏和丝网防护屏后形成的碎片云特性。研究表明：相同面密度的多层丝网防护屏防护效果优于连续型防护屏;对于连续型防护屏,锥体撞击部位对后板毁伤的影响大于锥体长径比对后板毁伤的影响,而对于丝网防护屏影响规律则相反;研究长固锥锥尖撞击2种防护屏后碎片云动量密度,撞击连续型防护屏后,弹丸碎片云动量密度分布具有对称性,较之丝网防护屏分布更为集中,且动量密度峰值大于撞击丝网防护屏后弹丸碎片云动量密度峰值。     

基于Taylor实验及理论分析的泡沫铝动态冲击特性研究

泡沫铝是一种优异的结构材料,有着广泛的应用前景,研究其冲击动力学性能具有重要的理论意义及工程应用价值。Taylor冲击实验主要利用圆柱弹体撞击刚性墙来获取弹体材料的动态响应数据,是一种重要的动态实验手段,在实体金属领域较为成熟。由于泡沫铝自身的可压缩性,经典Taylor理论无法适用,在一定假设基础上基于实验数据建立了针对泡沫铝动态冲击响应的Taylor分析模型,并验证了模型的有效性。实验结果表明：Taylor冲击后,泡沫铝子弹变形段平均密度随撞击速度的增加而增加,且当撞击速度大于110m/s时,其增长趋于平缓;泡沫铝子弹剩余长度随撞击速度的增加而减小,且近似呈线性关系。