Effect of Ultrasonic Impact Treatment (UIT) on Fatigue Strength of Welded Joints

Abstract

Abstract. Ultrasonic impact treatment(UIT) is a remarkable post-weld treatment, which reduce not only in external stress concentration, but also in residual stress in a welded joints. Internal and surface stresses were investigated on UIT treated welded joints by neutron and X-ray diffraction method. This paper discuses the effect of internal and surface residual stress and surface stress concentration after UIT on fatigue resistance by the comparison of fatigue experiments to predictions calculated with the results of the experimental investigations.

Fatigue crack initiation assessment of welded joints accounting for residual stress

“…For the first series, the material used in the welded joints is SM490 steel with a yield stress of 352 MPa. 47 Figure 1 shows the dimensions of the joints. The following welding parameters were provided by Han et al 46 : current 220 A, voltage 23 V, and gas flow rate 18 l/min.…”

“…47 After UIT process, the stress distribution had been completely changed, and significant compressive residual stress layers of about 2-3 mm depth were generated. 47 After UIT process, the stress distribution had been completely changed, and significant compressive residual stress layers of about 2-3 mm depth were generated.…”

“…47 In the tests, only total fatigue lives including both phases were recorded. 47 In the tests, only total fatigue lives including both phases were recorded.…”

“…The comparison is shown in Figure 12. In addition to the test results obtained by Suzuki et al, 47 extra test results 66 of similar UIT nonload-carrying cruciform joints under the stress ratio of 0.1 are also added. FAT140 with a slope of m = 5 is recommended in guidelines 65 for the cases of the high-frequency mechanical impact improved nonload-carrying joints.…”

Residual Stress Distribution and Mechanical Properties of TA15/BTi-6431S Titanium Alloy Welding Joints by Ultrasonic Impact Treatment

“…Many methods have been used to reduce the residual stress of welding parts, which are classified into heat treatment and mechanical methods. Compared with the traditional methods, ultrasonic impact treatment (UIT) can not only introduce compressive stress, but has advantages of easy operation, high working efficiency and low energy consumption [5][6][7]. TA15 titanium alloy (Ti-6.5Al-2Zr-1Mo-1V) is a kind of near-α titanium alloy with excellent thermal stability and welding performance and widely used in the welding parts of aerospace, engines and military industries [8].…”