正弦脉冲激光热弹激发超声应力脉冲特性研究

Characteristic Study of Sinusoid Pulse Laser Thermoelastically Generated Ultrasound Stress Pulse

应用一维热传导方程和纳维叶-斯托克斯(Navier-Stokes)方程,采用简化的正弦脉冲波形模型对激光激发产生的超声应力脉冲进行理论研究,分别得出弱吸收试样表面是钳紧或自由情况下应力脉冲的表达式。结果表明表面钳紧时应力脉冲是单极性的,自由时是双极性的,应力脉冲宽度远大于激光脉冲宽度,应力脉冲极值的幅度随着厚度的增加而逐渐减小,更加接近真实的斜高斯(skew-Gaussian)激光脉冲,且更具有普遍性。

Applying one-dimension heat exchange equation and Navier-Stokes equation, ultrasound stress pulse generated by laser is studied by using simplification sinusoid pulse model. Expressions of stress pulse are attained, which sample is feebleness absorbability and its surface is freedom or tightening. The results show that stress pulse of tightening surface is monopolar and freedom surface is ambipolar, the breadth of stress pulse is much bigger than laser pulse＇. Increasing thickness of sample, extremum of stress pulse decreases. Also it is much more closed to true skew-Gaussian laser pulse and universality.