Analysis of distortion in the welding of ‘X’ and ‘V’ joints in reduced-scale models of segmented rings using continuous monitoring with laser sensors

Abstract

Distortion in welded components is a permanent change of shape and dimensions from plastic deformations that occur due to thermal stresses developed during the welding process. Due to the high costs to correct the welding distortion, there is great interest from industries to predict, monitor and control these distortions. This paper compares the distortions occurring during welding models of the segmented ring scaled with two types of joints (‘X’ and ‘V’) using the method of monitoring progress of welding distortion with the laser sensors. For continuous monitoring are used laser sensors that are supported on the piece and the beams were projected on a translucent screen placed in front of the same. With the progression of distortion during welding light beams move around the screen in proportion to deformation occurred in the part. The displacements of points of light reflected on the screen are filmed from the opposite side of the bulkhead. The discretization of the film allows to analyze deformations along the welding process and determines the evolution of the distortion in function of time. It was confirmed that the welds performed joints in ‘X’ exhibit distortion values smaller than the joints in ‘V’. The results demonstrate that for the samples used in this experiment at least 60% of the distortion occurred after arc extinction. By experimental testing, it was possible to say that the technique of laser sensors monitoring is viable for use in industry and laboratories of welding, although it is necessary to optimize the data processing obtained by filming, allowing the instantaneous monitoring. The information on the evolution of distortion during welding will be useful to define and monitor more efficiently the best method of control. In addition, it may assist in experimental calibration numerical and computational models, or even to feed back the trajectory of a robot identifying deformations to perform corrections in the welding sequence ensuring also minor distortions.