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Residual stresses reduce life time of welded joints and change the welded structure formation. Residual stress is stresses that remain in the body some specific operation like welding and is available when body is not under external loads. Different methods are available for residual stress relieved in any welded samples. In this research, samples A, B and C have been prepared and welded. Stress of Samples A and B have been relieved using heat treatment method and ultrasonic method, respectively. Also, no operation has been taken on the sample c. for different amount of residual stress of each sample, hole drilling method used and amount of residual stress in welding heat affected area of each sample determined. Results show that residual stress in ultrasonic method is for less than heat treatment method. To validate the results the x-ray diffraction method was also used and results of this method show that sample with ultrasonic stress, stress reliving had no peek in 2Ө angles, but for sample with heat treatment stress reliving had a peek in 137° that shows some residual stress.

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In recent years, measurement of residual stress by ultrasonic method is developing because of nondestructive nature, portable equipment and being cheap and fast. In this research, the Capability of ultrasonic method by using longitudinal critically refracted or Lcr wave in measurement of longitudinal welding residual stress has been scrutinized. For this purpose, two plates of aluminum alloy series 5000 were joined by TIG welding method. Measurement of longitudinal residual stress by ultrasonic method was done in closeness of surface via 5 MHz transducers based on acoustoelasticity theory. In order to create Lcr wave and transmit it into specimen, an ultrasonic wedge was made based on Snell’s law. Also a triaxial table was used to control the wedge movement and keep the pressure on it fixed. In order to calculate residual stress and increase in accuracy, acoustoelastic constant for each three welding zones, including weld metal, HAZ and base metal was obtained separately from uniaxle tension test. In order to validate ultrasonic method results, measured longitudinal residual stress by x-ray diffraction method in 5 points on the specimen surface was used. Finally after comparing the results of two used methods with each other, good agreement was seen which indicates the good ability of ultrasonic method in measurement of longitudinal residual stress.