Device for detecting residual stress close to surfaces of metal materials

The invention relates to a device for detecting residual stress close to surfaces of metal materials. The device stimulates a critical-refraction longitudinal wave and calculates a stress value according to an acoustic elasticity theory. According to the invention, by reducing contact area between a wedge and a part to be measured, the affect of plate surface distortion to a measurement result can be effectively eliminated; the affect caused by temperature difference can be eliminated by temperature compensation; and therefore, the system is adaptable to tests in more terrible field environments. The system is higher in integration degree, small and exquisite in appearance and convenient to carry.