Using finite element and ultrasonic method to evaluate welding longitudinal residual stress through the thickness in austenitic stainless steel plates

Abstract

a b s t r a c tThis paper uses a 3D thermo-mechanical finite element analysis to evaluate welding residual stresses in austenitic stainless steel plates of AISI 304L. The finite element model has been verified by the hole drilling method. The validated finite element (FE) model is then compared with the ultrasonic stress measurement based on acoustoelasticity. This technique uses longitudinal critically refracted (L CR ) waves that travel parallel to the surface within an effective depth. The residual stresses through the thickness of plates are evaluated by four different series (1 MHz, 2 MHz, 4 MHz and 5 MHz) of transducers. By combining FE and L CR method (known as FEL CR method) a 3D distribution of residual stress for the entire of the welded plate is presented. To find the acoustoelastic constant of the heat affected zone (HAZ), a metallographic investigation is done to reproduce HAZ microstructure in a tensile test sample. It has been shown that the residual stresses through the thickness of stainless steel plates can be evaluated by FEL CR method.

Experimental Techniques to Investigate Residual Stress in Joints

“…The ultrasonic techniques are based on variations in the velocity of ultrasonic waves, which can be related to the residual stress state through the elastic constants of the material [34,44]. Like the magnetic methods, the ultrasonic techniques are sensitive to all three kinds of residual stress, but are not able to distinguish between them.…”

“…Different types of wave can be employed but the commonly used technique is the longitudinal critically refracted (Lcr) wave method [4]. The Lcr wave is an acoustical wave that is excited when the angle of incidence is slightly smaller than the first critical angle, which is calculated from the Snell's law [44,68,69]. It is a bulk longitudinal wave, traveling just below the surface of the specimen.…”

“…HDM was used to validate the results of the ultrasonic technique in investigations on FSW joints of 5086 plates [42], AISI 304 pipes [43] and plates [44]. The example in Figure 4 shows the good correspondence between ultrasonic and HDM residual stress evaluation.…”

“…So, a lot of research work was done for the evaluation of residual stress in different kinds of welding processes and materials [30,31,[40][41][42][43][44][45] with the final target to find the correct welding parameters and post processing conditions to minimize the residual stress. Some of these works use HDM as validation of nondestructive techniques such as ultrasonic [41][42][43][44][45][46], XRD [30] and neutron diffraction [31]. Pappalettere et al [47][48][49][50][51][52] applied an electronic speckle pattern interferometry (ESPI) method to avoid the use of conventional rosette strain gauges.…”

Evaluation of hoop residual stress variations in the thickness of dissimilar welded pipes by using the LCR ultrasonic waves

“…2a the wave propagates parallel to the load and V 11 represents the velocity of the particles in the same direction (longitudinal wave), meanwhile V 12 and V 13 represents the velocity in a perpendicular plane (shear waves).…”