光学元件亚表层裂纹成核临界条件研究

基于压痕实验和连续刚度测量法得到了熔石英材料硬度和弹性模量随压入深度的变化曲线, 系统分析了材料由延性到脆性转变的过程, 确定了熔石英晶体在静态/准静态印压和动态刻划时产生裂纹的临界载荷和临界深度。渐变载荷刻划实验结果表明, 划痕过程诱发的裂纹对法向载荷有很强的依赖性, 载荷较小时材料去除方式为延性域去除。随着法向载荷的增加, 首先产生垂直于试件表面的中位裂纹和平行于试件表面方向扩展的侧向裂纹, 而在试件表面上并没有产生明显的特征。载荷进一步增加后, 侧向裂纹扩展并形成了明亮区域, 最终诱发了沿垂直于或近似垂直于压头运动方向扩展的径向裂纹, 实现了材料的脆性去除。

Critical condition of subsurface crack formation for optics

Based on indentation experiments and continuous stiffness method, the relationship curves between indentation depth and hardness/elastic modulus were obtained for fused silica optics. The process of ductile to brittle transition was systematically analyzed, and the critical loads and critical depths were determined in static/quasi-static indentation or dynamic scratch process. The results of gradient load scratch experiments show that the crack induced by scratch process has a strong dependence on the normal load, and the material removal is ductile removal with a small load. With the increase of normal load, the median cracks perpendicular to the specimen surface and lateral cracks parallel to specimen surface are produced, while no obvious features are observed on specimen surface. Lateral cracks are extended and the bright regions are formed, eventually the radial cracks are induced, whose propagation directions are perpendicular or approximately perpendicular to indenter movement direction, so brittle material removal is achieved.