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An arc sensor for reciprocating wire feed gas metal arc welding was developed to detect the torch height and track weld joints. The welding voltage waveform was adopted for the characteristic signal because the welding current remains almost constant with a change in the contact tip-to-workpiece distance. During reciprocating wire feed gas metal arc welding, the voltage waveform changes in an inherently complicated but periodic manner. After recognizing the voltage waveform pattern, the voltage characteristic for each phase was analyzed for arc sensing, and it was revealed that the short-circuit and cycle voltage characteristics were good estimators for torch height sensing. The dynamic arc sensing characteristics for reciprocating wire feed gas metal arc welding were investigated and found to be similar to those of a conventional constant voltage welding system. The seam tracking capability was evaluated by using the voltage integration difference method with transverse torch weaving. The voltage integration difference showed a linear relationship with the offset distance, and the reliability of the joint tracking sensor could be increased by using the moving average algorithm. [ABSTRACT FROM AUTHOR]

A wider interface bead width is required for laser overlap welding by increasing the strength of the base material (BM) because the strength difference between the weld metal (WM) and the BM decreases. An insufficient interface bead width leads to interface fracturing rather than to the fracture of the BM and heat-affected zone (HAZ) during a tensile–shear test. An analytic model was developed to predict the tensile–shear fracture location without destructive testing. The model estimated the hardness of the WM and HAZ by using information such as the chemical composition and tensile strength of the BM provided by the steel makers. The strength of the weldments was calculated from the estimated hardness. The developed model considered overlap weldments with similar and dissimilar material combinations of various steel grades from 590 to 1500 MPa. The critical interface bead width for avoiding interface fracturing was suggested with an accuracy higher than 90%. Under all the experimental conditions, a bead width that was only 5% larger than the calculated value could prevent the fracture of the interface. [ABSTRACT FROM AUTHOR]