A Study on Strain Figures Observable in Mild Steel Arc-Weld Joints (Report I)

Abstract

Luders' lines -appearing in the weld due to thermal stress when a spot deposit or bead is laid by metallic arc welding on an area of the polished surface of a mild steel plate have been observed by a simplified apparatus for Schlieren's method and the slip plane in the section has been determined by etching with Fry's etchant.
With reference to strain figures observable in welds carried out on areas with distribution of residual stresses already known or in welds on the surface of a steel strip placed preliminarily under constant load, the author. has attempted to advance a general theory explaining the causes of development of various patterns of strain figures, namely : systems, appearing in the case of a spot deposit, of Type I concentric circles, radial lines, or spirals; systems, arising in beads, of Type II concentric circles radial lines or spirals appearing at starting and finishing ends, and of beardlike lines clustered in series or perpendicular lines acroses the bead, which are formed in straight welds