DETECTION AND ANALYSIS ON RESIDUAL STRESS DISTRIBUTION INDUCED BY THE PROCESSING METHOD OF CIRCULAR TUBES

To study the longitudinal residual stress distribution induced by the processing method of circular tubes, an experimental program including five groups of fifteen φ325×8 specimens of different strength and processing methods were 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. The effects of submerged arc welds, high frequency welds and hot rolling were analyzed. It was indicated that the effect of submerged arc welds on the longitudinal residual stress was stronger than that of high frequency welds. The high strength steel welded tubes was flatter than those of ordinary steel tubes, and the maximum value of longitudinal residual stress almost reached the yield stress in the welded zone about 40 mm distance from the center line. The longitudinal residual stress of ordinary strength steel tubes was 0.35σ_y, while the test values of Q690 high-strength steel tubes was 0.21σ_y. Compared with the peak longitudinal residual stress on the middle sections, the peak longitudinal residual stress on the starting and end sections were smaller. Different from welded circular tubes, the maximal longitudinal residual stresses on the inner and outer surfaces of hot-rolled seamless steel tubes were the same in absolute value, which were about 0.15σ_y, but their signs were opposite.