中文摘要：

利用垂直入射的偏振横波换能器,首先研究了偏振方向与铝合金棒材挤压方向成不同角度的超声横波速度的差异,然后对不同应力下与应力方向成不同角度偏振的超声横波速度的变化进行了研究.试验结果表明：在无应力时,平行于挤压方向偏振的横波和垂直于挤压方向偏振的横波的速度差异不大,棒材的各向异性对不同方向偏振横波速度的影响不明显.当施加应力后,平行于应力方向偏振的横波传播时间升高,垂直于应力方向偏振的横波传播时间降低;在剔除材料弹性变形所带来的声传播距离变化的影响后发现,平行于应力方向偏振的横波声速降低,垂直于应力方向偏振的横波声速升高;与偏振方向平行的应力对横波速度的影响大于与偏振方向垂直的应力对声速的影响.

英文摘要：

The difference in velocities of ultrasonic shear waves at different angles between polarization direction and the direction of ex- trusion of aluminum alloy bar was first investigated by using a normal incidence polarized shear wave transducer, then the change of ve- locity of the ultrasonic shear wave polarizing at different angles with respect to the stress orientation under different applied stresses was studied. The experimental results indicate that there is a little difference of velocity of shear wave polarizing between parallel and per- pendicular to the direction of extrusion in unstressed state, and anisotropy of the bar has little effect on the velocity of the polarized shear wave in different directions. When the specimen is submitted to an increasing axial loading, the time of flight of shear wave polar- izing parallel to the direction of stress increases, the travelling time of shear wave polarizing perpendicular to the direction of stress de- creases ; after eliminating the influence of change of the propagation length of the ultrasonic wave brought by the elastic deformation of material, the results find that velocity of shear wave polarizing parallel to stress orientation decreases, velocity of shear wave polarizing perpendicular to stress orientation increases ; the effect of stress which is parallel to polarization direction on velocity of the shear wave is more than that of stress which is normal to polarization direction on ultrasound velocity. This experiment provides a non-destructive method for the measurement of the plane stress field within material, which can non-destructively evaluate internal stress of material.