Quality assurance for high-frequency mechanical impact (HFMI) treatment of welds using handheld 3D laser scanning technology

Abstract

The idea of using 3D point clouds obtained with the aid of a handheld 3D laser scanner for the quality assurance of high-frequency mechanical impact (HFMI) treatment is proposed and demonstrated in this paper. The effectiveness of impact treatments for extending the fatigue lives of welded structures has been demonstrated in numerous studies. Guidelines for the proper execution of impact treatments have been developed. A lack of suitable quality assurance (QA) procedures for accepting or rejecting the treatment after completion has been previously identified. In contrast with the existing QA procedures, which are based mainly on controlling inputs and visual inspection, a technology-based, quantitative methodology is developed in this paper. Five welded specimens were subjected to impact treatment at various levels to simulate under-, proper, and over-treatment. A handheld 3D laser scanner was then used to facilitate a point cloud-based method to determine the geometric parameters of the treated weld toe groove, which were then measured manually. The results show that the proposed methodology is successful in identifying the different treatment levels. This approach has a number of advantages over the existing QA methods, including the following: providing quantitative measures, ease of use, and archive-ability.

Testing and fracture mechanics analysis of strength effects on the fatigue behavior of HFMI-treated welds

“…In both studies, the treatment was performed until visual evidence of the weld toe was removed and an indent was achieved and could be measured with a welder's undercut gauge. Clearly though, there would be a benefit to further developing rapid, accurate, and less subjective means for measuring the indent depth while the treatment is in progress, such as 3D laser scanning [7].…”

“…The potential of these treatments for fatigue retrofitting of existing structures and mechanical components or weight reduction in new fatigue critical components is considerable. Various studies have been undertaken to quantify the resulting fatigue life increase and investigate the significance of scale effects [1], the treatment effectiveness for high-strength steels [2][3][4], the treatment effectiveness under variable amplitude loading [5], and the effects of treatment quality control [6,7]. Estimation of the HFMI treatment benefit has been limited to comparison using nominal stress S-N curves [8] and local stress approaches [9].…”

Modeling and Calibration of the Galvanometric Laser Scanning Three-Dimensional Measurement System

“…In recent years, the laser scanning systems have been widely applied in many industrial applications, such as medical imaging [1], quality assurance [2], machine vision [3,4] and reverse engineering [5,6]. The fast acquisition speed, the high accuracy, the good stability and the low cost make it one of the most promising techniques to obtain the geometric surface information.…”

Effect of high frequency mechanical impact treatment on fatigue strength of welded 1300 MPa yield strength steel

“…The depth, width and radius of the HFMI treated region are therefore important geometrical parameters which affect the fatigue strength. The compressive residual stresses and increased surface hardness in the treated region have also been claimed to improve the fatigue strength [9,26,27].…”