基于激光表面波技术的硬脆材料加工表面/亚表面损伤检测理论与方法研究

Hard-brittle materials are widely used in the aerospace, defense and other high-tech fields by its unique mechanical properties, mechanical physical properties. The quantitative detection of its damage in surface layer produced by the machining process, especially, the sub-surface damage, is taken as an distinctive and challenging subject in the surface integrity of the research area. In this project, according to typical structural characteristics of hard-brittle materials, propagation mechanism of Surface Acoustic Wave (SAW) in the layer of surface/subsurface damage will be researched, based on Elasticity, Fracture Mechanics and Acoustic Wave Propagating Theory; innovatively propose a converse algorithm solving mesoscopic strength feature in its layer according to acoustic dispersion propagation mechanism, establish a theoretical model for the calculation the physical and mechanical properties of the machining surface and subsurface layer, and proposed a complex frequency SAW method on detecting damages in the surface layer; by improving the design of differential confocal structures and the double-parallel beam SAW technology detector platform, to achieve the quantitative detection of surface layer properties of typical hard-brittle material specimen; and study the reliability of the measurement results of the detection system by comparison with results of Nano-indentation test. Therefore, this work has an important theoretical and practical significance for providing a persuasive criterion for quantitative detection of damage properties of the machining surface layer of hard-brittle materials, effectively improving the reliability, controllability and safety of hard-brittle materials workpiece in its serving process.

硬脆材料以其独特的机械性能、力学物理性能在航空航天、国防等高新技术领域广泛应用。其加工过程产生的表面层损伤特别是亚表面损伤的定量检测是表面完整性研究领域独特且有挑战性的课题。本课题拟根据典型硬脆材料结构特性，基于弹性力学、断裂力学及弹性波传播理论，研究表面波在其材料表面/亚表面损伤介质层传播机制；创新提出超声色散传播特征逆向求解介质细观强度特性算法，建立反映硬脆材料加工表面损伤层状态的机械特性、物理及力学特性的理论计算模型，提出利用复合频率SAW检测材料表面层损伤的方法；通过改进设计搭建基于差分共焦结构和双并行光束技术的激光声表面波检测平台，实现典型硬脆材料试件表面层性能的无损定量检测，并与纳米压痕仪进行对比测试，研究该检测系统测量结果的可靠性。本研究将为硬脆材料加工表面层损伤特性的定量检测提供可靠手段，对提高其零件在使用过程中的可靠性、可控性和安全性有着重要的理论意义和工程应用。

本项研究以弹性波传播理论、声表面波色散理论、弹性力学、损伤力学、光学干涉等理论为基础，结合有限元分析及实验分析方法，研究了使用激光声表面波技术来检测硬脆材料加工表面/亚表面损伤特性。具体研究内容包括：围绕激光表面波在硬脆材料表面层介质中传播机制及声表面波在非均匀介质中的色散现象，提出了硬脆材料加工表面损伤分层模型，形成了声表面波在不同性质材料中的传播及色散理论，并建立相应的程序算法，为材料加工表面层机械特性的逆向求解提供了匹配依据；根据激光声表面波的激发原理，应用有限元仿真研究复频声表面波的激发及传播机制，并探讨了各项参数对声表面波信号的影响，为实验平台的搭建和仪器选择提供了重要依据；设计并搭建基于差分共焦结构和双并行光束技术的正交偏振差分干涉声表面波非接触式检测平台和基于压电技术的接触式声表面波双检测平台，自主完成关键部件的设计与组装，并对实验系统的性能进行检测标定。将双检测系统用于材料表面/亚表面加工损伤状态检测，提出了使用杨氏模量变化量对其综合评价与表征，并通过离子注入法、纳米压痕法及不同材料加工表面试件对比实验，验证了该检测系统用于定量检测硬脆材料表面/亚表面因加工导致损伤程度的可行性。该项研究提出了检测硬脆材料加工表面质量的新方法，并形成相对完善的检测理论及实验系统，在精密和超精密加工技术领域具有重要的实用价值和广泛的应用前景。