EXPERIMENTAL INVESTIGATION ON LONGITUDINAL RESIDUAL STRESS DISTRIBUTION OF CIRCULAR STEEL TUBE SECTIONS

In order to study on the longitudinal residual stress distribution induced by the processing method of circular tubes, an experimental program including five groups of fifteen different strengths and processing methods specimens of cross-sectional specification such as F325. 8 was conducted, in which the blind-hole method was employed. Based on large quantities of original test data, the residual stress distribution and the magnitudes of these different specimens were obtained, and the effects of submerged arc weld, high frequency weld and hot roll were analyzed. It was indicated that the effects of submerged arc weld on the longitudinal residual stress was stronger than high frequency weld, the residual stress distribution of high strength steel welded tubes was flatter than the ones of ordinary steel tubes, and the maximum value of longitudinal residual tensile stress almost reached the yield stress on welded zone about 40 mm distance from the center line. In addition, the longitudinal residual compressive stress of ordinary strength steel tubes was 0.35 sigma y, while the test value of Q690 high-strength steel tubes was 0.21 sigma y. Compared with the peak values of longitudinal residual stress on middle cross-sections, those of the welding starting and end cross-sections were smaller. Unlike welding way, the maximum of longitudinal residual stress was same on the inner and outer surfaces of hot-rolled seamless steel tubes, which was about 0.15 sigma y, but its sign was opposite.