激光热弹超声的等效电路

Thermoe lastic equivalent circuit of laser ultrsound

本文以热弹理论为基础，提出了一种描述激光热弹超声的等效电路模型，该模型将激光直接照射区同周围的声传播媒质分开考虑，采用三端口网络描述了热一弹能量的直接转换，传播声场的影响则以辐射阻抗的形式出现。由于电路是由单频情况导出，故任意时间响应可通过ＩＦＦＴ算法得到。本文针对三种典型照射区，既圆板、柱和球、建立了绝抽条件下的热弹等效电路，计算了各自的时间响应，结果与格林函数解相符。

On the basis of thermoelasticity theory, an equivalent circuit model of laser-generatedultrasound has been proposed. With this model, lase-heated region is separated from surrounding mediumand described as a three-ported electrical circuit which demonstrates the direct conversion between thermalenergy and elastic energy, while contacting with external transporting medium in the form of radiahonimpedance. As the circuit is derived fron single frequency excitation, arbitrary temporal response can be calculated by means of IFFT algorithm. In this paper, three kinds of typical heated regions are considered inthe case of circular plate, cylinder and sphere. Their laser pulse responses are calculated and diagramedrespeCtively. It is shown that results agree well with previous reports.