激光脉冲激发的超声脉冲波形的理论研究

The Study of Theory of Ultrasound Pulse Waveform Produced by Laser Pulse

在激光热弹产生超声的研究中 ,对于产生超声的激光脉冲波形 ,大都是采取简化处理了的矩形脉冲或三角形脉冲 ,这样的处理虽然在计算上较易得出结论 ,但它与真实的高斯激光脉冲有较大的差别 .为此笔者采用更接近于实际激光脉冲波形的梯形脉冲模型 ,应用热传导方程和Navier- stokes方程对半无限大介质中所激发的超声脉冲特性进行了计算研究 ,结果得出了比矩形脉冲更具普遍性的结果 。

Study on the laser thermoelastically generated ultrasound, The shape of laser pulse is generally assumed a rectangular pulse or cosine pulse, However the assumed pulse forms not exactly represent the real experinental laser pulse, which is always a Gaussian pulsed forn. Because they can be calculated simply. Therefore a new shape trapezoid pulse is presented in this paper, and the stress of laser thermoelastically generated ultrasound in solid medium is calculated by using the heat conduction and Navier stokes equations, It is shown that trapezoid pulse has more generality and the results is good in agree ment with the experiments.