金属材料中激光产生Lamb波的数值模拟

材料表面吸收激光辐照的能量后，产生瞬态温度场进而引起材料表面层的热膨胀，产生超声波．从超声波沿不同方向传播的特性出发，根据激光作用源的特征，建立了热弹性有限元模型，研究了激光和材料相互作用的瞬态过程，包括瞬态温度场和瞬态应力场及其分布．数值模拟结果表明：瞬态温度分布等效于体力源，其中轴向应力将产生纵波，径向应力将产生横波，激光作用在薄金属材料中激发出Lamb波．

Thermal and mechanical finite element modeling of laser-generated ultrasound in metals

Laser pulse incident on a material generates the transient temperature field. As repaid and localized thermal expansion occurs, energy is released in the form of propagating ultrasound in all directions. A finite element model for the laser-generated ultrasound is presented, which entails a numerical formulation for the transient responses in terms of the characteristics of the source that originated the waves in the thermoelastic regime. Numerical results show that temperature distribution is equivalent to the body force source, namely, vertical forces towards the specimen along the laser input source and horizontal forces outward. It also shows that when the receiver is near the acoustic source, the waves are reverberated at the upper and lower boundaries with a following low-frequency trail. When the distance increases to much larger than the thickness of specimen, typical Lamb waves are formed.