Overview of recent advances of process analysis and quality control in resistance spot welding

Deep learning assisted vision inspection of resistance spot welds

Corrosion mechanism of reinforced bars inside concrete and relevant monitoring or detection apparatus: A review

Corrosion monitoring of reinforcement is of great importance in evaluating the durability performance of concrete structures, especially under harsh environments. This paper presents a creative approach that combine using innovative electromagnetic monitoring apparatus (EMMA) and digital image correlation (DIC) technique in order to monitor the reinforcement corrosion inside concrete. The new-type electromagnetic sensor is capable of evaluating the corrosion degree of reinforced bars in concrete, meanwhile, DIC technique is always used to detect the tiny corrosion-triggered deformation on concrete surface. The result shows that joint use of these two techniques can monitor the entire process from corrosion initiation to further corrosion-induced strain variation on the surface of concrete. Besides, concrete beam with higher vertical load level leads to greater bending movement, which will accelerate the corrosion behavior and limit the horizontal strain. Moreover, the characteristics of DIC technique and strain gauges are compared respectively.

Coupled application of innovative electromagnetic sensors and digital image correlation technique to monitor corrosion process of reinforced bars in concrete

This paper introduces an innovative Nondestructive testing (NDT) approach by using dynamic magneto-optical imaging (MOI) system to diagnose weld defects. MOI mechanism was explained by Faraday magneto-optical effect and magnetic domain theory. Two Q235 specimen MOI experiments based on excitation of permanent magnet and alternating electromagnet (alternating current driven electromagnet) were performed, thus the feasibility of MOI system for weld defects detection was verified and the relation between alternating magnetic field (AMF) and dynamic MO images was discussed as well. In this research, AMF of welded high-strength steel (HSS) weldment was excited by an alternating electromagnet, and dynamic MO images of HSS seam were acquired for weldment NDT. Finally, a pattern recognition method including three steps was proposed. Dynamic MO images were fused periodically and the features of fused images were extracted by principal component analysis. A classifier based on error back propagation (BP) neural network was established to identify these weld features. It proved that typical weld features such as incomplete penetration, sag, crack and no defect can be classified by the proposed method with an accuracy of 93.5%.

Weldment Nondestructive Testing Using Magneto-optical Imaging Induced by Alternating Magnetic Field

Resistance spot welding technologies are widely used in industry. A highly reliable monitoring method is needed to effectively weld and create a robust structure. We developed a combined technique using magnetic flux penetration and an eddy current test (ECT). The magnetic measuring system consists of a pair of magnetic probes having an induction coil and detection coil, a lock-in amplifier, a current source, and a personal computer. The magnetic flux penetration through both surfaces at the weld was measured at low frequency. The ECT was performed at each surface with multiple frequencies. The magnetic flux penetration method showed good correlation with the destructive shear test because of the change in permeability due to the formation of the nugget. The ECT method reflected the depth profile of the nugget and was effective for determining a defective product.

Daichi Harada

Papers

Magnetic Nondestructive Test for Resistance Spot Welds Using Magnetic Flux Penetration and Eddy Current Methods

Investigation of the structure and tribological properties of laser-irradiated hydrogenated amorphous carbon films