Fundamental study to establish the principle of acoustoelastic residual stress measurements using off-axis waves

在已有的大多数声弹性测量中，波的传播方向取为垂直于试件表面或平行于试件表面，而离轴波沿试件表面倾斜传播的声弹性应用，除了少数工作外，很少有人研究。理论上，采用摄动法(一般近似)分析了离轴波速与传播方向(θ，φ)的关系，并假定基于多晶模型的织构各向异性简化，将结果整理成扩展表达式(多晶近似)。在实验中，以钢板为试件，钢楔主要用于发射和接收离轴波。通过更换楔形板(楔形角θ=20°、30°、40°、50°)和旋转换能器方向(φ=15°~195°)来改变传播方向，测量离轴反射波在每个传播方向上的传播时间T(θ，φ)。由这些实验结果证实，用一般近似可以较好地解释离轴纵波的速度各向异性。然而，用多晶近似也很难定量地解释相同的速度各向异性。

In most of acoustoelastic measurements so far made, the propagation direction of waves has been taken normal or parallel to specimen surfaces, and the acoustoelastic use of off-axis waves propagating obliquely against it has been hardly investigated except in few works. Tins study is concerned with the formulation of the acoustoelastic law for off-axis waves.Theoretically, the dependence of the off-axis wave velocity on the propagation direction(θ, φ) is analyzed by the perturbation method (general approximation), and , assuming the texture anisotropy simplified based on the polycrystalline model, the result is arranged in expanded expressions (polycrystalline approximation).In the experiment, a steel plate is taken as the specimen, and steel wedges are mainly used for transmitting and receiving off-axis waves. The propagation direction is changed by replacing wedges (wedge angle θ = 20° , 30°, 40°, 50°), and rotating the transducer direction (φ = 15° 〜 195° ), and the propagation time T(θ, φ) of off-axis reflected waves is measured in each propagation direction. From these experimental results, it is confirmed that the velocity anisotropy of longitudinal off-axis waves is explained relatively well by the general approximation. However, it is also shown difficult to explain the same velocity anisotropy quantitatively by the polycrystalline approximation.