Study On Residual Stress Testing By Ultrasonic

Residual stress do greatly effect on security of components occurred interior and exterior of material and now many methods has been used to detect residual stress. As an advanced technology, the technique used ultrasonic to test residual stress has developed quickly recently by reason of its unique advantage. Based on acousto-elasticity, this technique can detect interior and exterior stress of components. On the other hand, it can also use to test applied stress. Testing velocity mainly on detect stress, counter is used to work as the core during signal processing. In order to analyze and control signal high precise and avoid error occurred by distance in processing, an ultrasonic critically-angle refractometry (UCRfr) technique is used to test velocity. Additionally, two collateral tunnels process signal respectively. Only by counter velocity transmitted inside components will be got. If we hold the distance unchanged between the emitting transducer and receiving transducer, the acousto-elasticity equation can be used without measuring the distance. Emitting longitudinal critically refracted (Lcr) wave, this technology is called settled-distance refractometry technique that is practicability to detect the interior stress produced in different depth with different frequency ultrasonic transducer. According to 1 MHz or high frequency ultrasonic transducer, it is difficult to control well by SCM. The device used complicated programmed logic device (CPLD) to produce the driver control signal control transducer more precise than those by the traditional single chip control circuit. With a high frequency oscillator, the high frequency counter which is availability to count precise will be got. With RS-232C criterion interface, testing stress device communicate with PC which process and control signal more. Finally, an economy and applied ultrasonic stress device is designed based on experiment and theories.