Study On Stress Nondestructive Testing For Members Of Steel Structure Based On Ultrasonic Method

The internal-initial stress of in-service steel structure members is an important indicator of steel structure safety evaluation. Traditional stress detection methods, such as resistance strain gauges, X-ray method, magneto-elastic method, can not meet the requirements of the internal stress, the initial stress and non-destructive testing of in-service steel structure members. In response to this problem, the present paper puts forward a new method to detect internal-initial stress of in-service steel structure members by using ultrasonic stress measurement method in view of the application of ultrasonic stress measurement method in welding and railway areas. The main contents of this paper include following three aspects:Theoretical formula suitable to steel structure members based on ultrasonic stress measurement method was derived. The present paper derived formula suitable to steel structure members stress measurement on the basis of sound elasticity theory and chose the critically refracted longitudinal wave as stress testing wave. As steel members exposed to outdoor, impact of temperature can not be neglected during measurement. The expression of stress-sonic time formulas in both considering temperature changing and not were given.Detection system suitable to steel structure members based on ultrasonic stress measurement method was built. The present paper established detection system on the basis of theoretical formula derivation and characteristics of critically refracted longitudinal wave. Hardware system was built by making clear parameters each instrument needs to meet and combination method of scattered instruments. Software system was built by compling of modules such as signal de-noising, moment capture of pulse advent, stress-the sound of jet lag factor calibration, steel structure stress solution modules. On the basis of hardware and software building, the process of stress mearemengt in this system was given.Stress for members of steel structures was detected and validated based on ultrasonic method. In the present paper, stress in steel structure members was detected on the self-built system and the results were validated by using resistance strain gauge mensurement method. The results showed that ultrasonic stress measurement method was reliable. Through the analysis of the experiment processos which may cause errors, the present paper gave the issues that need attention during the experiment. Finally, in view of the importance of stress- sound lag factor, the present paper researched influences factors such as the probe position and sound path. As can be seen from the experimental and analytical results, the present paper realized the goal of detecting internal-initial stress for members of in-service steel structure based on ultrasonic stress measurement method and this method is accurate in test and easy to operate.