A Review of Non-Destructive Testing (NDT) Techniques for Defect Detection: Application to Fusion Welding and Future Wire Arc Additive Manufacturing Processes

Abstract

In Wire and Arc Additive Manufacturing (WAAM) and fusion welding, various defects such as porosity, cracks, deformation and lack of fusion can occur during the fabrication process. These have a strong impact on the mechanical properties and can also lead to failure of the manufactured parts during service. These defects can be recognized using non-destructive testing (NDT) methods so that the examined workpiece is not harmed. This paper provides a comprehensive overview of various NDT techniques for WAAM and fusion welding, including laser-ultrasonic, acoustic emission with an airborne optical microphone, optical emission spectroscopy, laser-induced breakdown spectroscopy, laser opto-ultrasonic dual detection, thermography and also in-process defect detection via weld current monitoring with an oscilloscope. In addition, the novel research conducted, its operating principle and the equipment required to perform these techniques are presented. The minimum defect size that can be identified via NDT methods has been obtained from previous academic research or from tests carried out by companies. The use of these techniques in WAAM and fusion welding applications makes it possible to detect defects and to take a step towards the production of high-quality final components.

Non-Destructive Detection of Real Defects in Polymer Composites by Ultrasonic Testing and Recurrence Analysis

“…Changes in the electric current and magnetic field are the basis for the assessment of the defect [ 6 ]. The disadvantage of magnetic methods is the detection of defects greater than 1 mm [ 8 ]. These are good methods for assessing the depth of defects due to the possibility of penetration of a few mm into the material [ 7 ].…”

“…The advantage of this type of test is that it is completely non-destructive. Ultrasonic testing allows the detection of defects over 0.5 mm [ 8 ]. Preparation of the sample for testing does not require costly preparation, and the test can only take place from one side.…”

Numerical Study and Optimal Design of the Butterfly Coil EMAT for Signal Amplitude Enhancement

“…Non−destructive testing (NDT) is an inspection method that does not damage the physical structure and material properties of the test specimen [1]. It is widely used for industry and structural health monitoring, such as evaluating the quality of continuously cast high carbon billets, and inspection of railway tracks, tank floors, oil and gas pipelines, and large metal plates.…”

Metal Surface Defect Detection Method Based on TE01 Mode Microwave

“…In terms of metal surface defect detection, eddy current detection technology is sensitive to nearsurface defects in conductive materials, and the signal-to-noise ratio of eddy current coils is low at low frequencies [6][7][8]. Laser inspection has the advantage of non-contact, all-view inspection [9,10]. The image processing method has a good detection effect on surface crack detection [11,12], and it has higher requirements for the image acquisition method and image quality.…”