Research Of Residual Stress Measurement In Plane Stress Field Based On LCR Wave

Welding residual stress is one of the important parameters in evaluating thereliability of welding structures. Thus it will be of vital significance if the weldingresidual stress can be measured accurately, for the designing and physicalpoperties of the structures, and the life span, too. Compared with other methods ofwelding residual stress measurement, ultrasonic method has great potential inapplication because it is convenient, nondestructive, and of high efficiency.Since the LCR wave is very sensitive to stress changes, it has been the vitalwave used in the stress measuring. However, the LCR measurments performedbefore ignored the influences produced by the stress perpendicular to the directionof propagation of ultrasonic, therefore they resulted in erros. To realize accuratemeasurement of stress, this paper takes the influences produced by the stessperpendicular to the direction of propagation of ultrasonic into consideration, andputs forward2-dimension Acoustoelastic equations and a ‘3directions alternatingwith45degree of arc’ gauge method in the welding residual stress field, thus thestress and direction can be aware by solving the Acoustoelastic equation.Furthermore, a laboratory system was set up to gauge residual stress. Theprobe mounting clamp was designed specially for this measurement, and themeasurement accuracy has been improved. The acoustoelasticity coefficientK₁,K₂have been calibrated for aluminum alloy7N01. After that, the residualstress in a7N01aluminum alloy welding structure was measured, and the resultshave been verified by static stress field combined with blind hole method. Theverification results showed that the measurement results from this system wereaccurate and reliable. Reasons for errors have been analysed as well.The measurement supporting software strategy has been produced usingLabview. It can realize real-time operation. Also, the measurement data can bereasonablly dealt with, and the results can be real-time input and output, whichmakes the whole gauge process rapid and convenient.A stability model test isdone to find the reasonable valve value,and it is found that the measurement datahas the highest stability when the vavle value is zero.The plane stress field of the chassis of bullet train is gauged, and the resultshave been analysed, which made reference and guidance for the application inengineering of this gauge system.