Study on Effect of UIT on Welded Residual Stress of Innovative Doubly-Welded Rib-to-Deck Joint in Orthotropic Steel Decks

Compared with traditional singly-welded rib-to-deck joint(SRJ), there exists a greater number of welds and more complicated welded residual stress(WRS) distribution in innovative doubly-welded rib-to-deck joint(DRJ), and it is of great significance in further promotion and application of DRJ to develop applicable post-treatment measures for adjusting WRS in DRJ. In order to study the effect of ultrasonic impact treatment(UIT) on WRS of DRJ, the welding process of DRJ was simulated by thermal-stress sequence analysis to obtain the distribution of temperature fields and stress fields; then the obtained WRS was imported into the finite element model of UIT as its initial analysis state by stress-strain initialization techniques; finally, the UIT process was simulated based on the dynamic explicit analysis, and the numerical oscillations of the dynamic explicit analysis were reduced by mass proportional damping technique.
To demonstrate the reasonability of the multi-step sequential analysis finite element model, it was validated from the following aspects:the analyzed melting zone shape was compared with the real weld morphology to validate the correctness of the analyzed temperature fields; the analyzed longitudinal and transverse WRS was compared with the test data to validate the correctness of the analyzed stress fields; the analyzed impact pit and impact residual stress were respectively compared with the real impact pit and the test data to validate the correctness of UIT simulation. On basis of fully validating the correctness of the finite element model, study on the effect of UIT on WRS in DRJ was executed and the residual stress around the weld was analyzed under different impact times and velocities.
The study showed that:the multi-step sequential analysis finite element model could accurately simulate the effect of UIT on WRS in DRJ; the residual tensile stress around the weld toe of DRJ was transformed into residual compressive stress due to UIT, and the decreased stress amplitude was 427.2 MPa; the residual compressive stress existed from the bottom surface of the deck to a certain depth, and the maximum of the residual compressive stress appeared on the subsurface of the deck; the residual compressive stress amplitude and impact affected depth around the weld toe of DRJ gradually increased as the impact times of ultrasonic impact pin increased; when the impact velocity of ultrasonic impact pin increased, the depth of the peak value of residual compressive stress increased gradually, and the depth was up to 0.8 mm when the impact velocity was 7 m/s.