The Mechanics of the Generation and Propagation of Thermoelastically Generated Lamb Waves in Plates and Panels

将进行实验/数值研究，以了解热弹性产生的兰姆波的产生和传播的基本力学，这是利用这些波对晶圆片、板和面板进行无损评估所必需的。由于兰姆波在板的平面上传播并影响整个厚度，因此它们对于确定表面裂纹、分层和材料性能的局部变化等缺陷的程度和严重程度是非常好的。用短持续时间光纤引导激光脉冲照射薄板表面的小区域，产生宽带瞬态兰姆波。由此产生的热冲击产生一个波，然后由光纤干涉仪检测。数据分析将在频率域中进行，因为缺陷在波上留下的印记是最明显的。数值和实验方法将结合起来，研究这些波的产生和传播所涉及的基本参数，以及它们受缺陷影响的方式。由此产生的知识将用于设计有效的方法，以产生具有理想特性的波，并优化整个系统，以识别和表征质量控制和安全保证的缺陷。

An experimental/numeric study will be carried out for acquiring the understanding of the basic mechanics of the generation and propagation of thermoelastically generated Lamb waves that is needed to exploit these waves for nondestructive evaluation of wafers, plates and panels. Since Lamb waves propagate in the plane of a plate and affect the whole thickness, they are excellent for determining the extent and severity of defects such as surface cracks, delaminations and local changes in material properties. Broadband transient Lamb waves will be generated by irradiating a small area on the surface of a plate with a short duration fiber guided laser pulse. The resultant thermal shock generates a wave which is then sensed by a fiber-optic interferometer. Data analysis will be in the frequency domain where the imprints that defects leave on the wave are most clearly evident. The numeric and experimental methods will be combined to study the basic parameters involved in the generation and propagation of these waves and in the ways in which they are influenced by defects. The resultant knowledge will be used to design efficient means for generating waves with desirable characteristics and to optimize the overall system for identifying and characterizing defects both for quality control and safety assurance.