压剪复合冲击下氧化铝陶瓷的剪切响应实验研究

Experimental study on shear response of alumina under combined compression and shear loading

通过对92. 93%氧化铝陶瓷进行倾斜板碰撞实验,研究了多晶陶瓷材料在压剪复合冲击下的非弹性变形响应和剪切波传播规律。压剪复合冲击实验由 57mm开槽气体炮驱动铜飞片对陶瓷靶板加载,通过试件内埋植的电磁速度计来测量内部质点速度历程。将纵向粒子速度从感应电动势曲线中分离后得到横向粒子速度历程,发现在压剪复合冲击下由于材料剪切刚度的降低而引起的剪切波衰减。冲击软回收试件的扫描电子显微镜(SEM)观察表明,冲击载荷低于屈服强度时,多晶氧化铝陶瓷中存在沿晶界、气孔的微裂纹成核与扩展,在高于屈服强度的冲击加载下进一步产生了穿晶微裂纹,微裂纹系统导致了材料在卸载后的显著的体积膨胀。

The pressure-shear plate impact experiments and impact recovery experiments have been performed on 92.93% alumina using 57 mm-diameter compressed-gas gun. And the inelastic behavior and shear wave propagation have been probed in polycrystalline ceramics under combined compression and shear loading. The compressed-gas gun drove the copper flyer to impact the oblique target parallelly, and the particle velocity is traced by embedded electromagnetic velocity gauge. The lateral particle velocities show an attenuation of shear waves with the decrease of material shear rigidity, which were decoupled from the histories of electromotive force induced by electromagnetic velocity gauges moving in magnetic field. Then SEM analysis of recovered samples shows the transit of intergranular microcracks to transgranular microcracks with increasing shock loading. Microcracks nucleate and expand along crystal boundaries and pores under loading of pressure-shear impact below the material yield threshold, and go further to transgranular microcracks with the loading above the yield threshold. The microcracks result in a remarkable dilation of alumina samples when unloaded.