In this paper, the ultrasonic fatigue machine which works at frequency of 20kHz is utilized to conduct the ultrasonic fatigue tests on a high strength welding structural steel with symmetric cycle stress R=-1 at room temperature. Two typical specimen geometries are tested: smooth specimen and notch specimen. The fatigue tests of smooth specimen are also carried out on the electromagnetic resonance equipment at conventional frequency. A comparison is made between the fatigue test results at the ultrasonic and conventional frequency.
In this paper, the fatigue property of ultra-high strength mould steel is investigated. The fatigue specimen is designed particularly due to the ultra-high strength. Fatigue tests are conduced using ultrasonic and conventional fatigue testing machines respectively. The same geometry and size of the ultrasonic fatigue specimens and conventional fatigue specimens are adopted to overcome the size effects. The test results are compared to investigate the frequency effect.
This study provides an engineering application of a continuum damage model to analyze the ductile tearing of axial surface cracks in X80 pipelines. Compact tension experiments were conducted to examine the behavior of large crack extension of X80 pipeline steel. The test results were used to verify the optimized parameter set of the proposed damage model. In the numerical model, progressive damage was restricted within a predetermined fracture process zone (FPZ). The material’s damage behavior in FPZ was described in terms of the Gurson–Tvergaard-Needleman (GTN) micro-mechanical damage model. The measured load versus load line displacement curve of CT specimens was numerically predicted using the damage model developed. T* integral was calculated to determine the limiting crack size in X80 pipelines. The damage model was then used to analyze the axial subcritical crack extension. It can help Leak-Before-Break (LBB) assessment.
Ultrasonic fatigue testing was conducted for 3000 MPa-class mould steel to investigate the fatigue behavior. The fatigue specimen is designed particularly due to the ultra-high strength. Ultrasonic fatigue tests are conduced using two types of specimen sizes and the test results are compared to investigate the size effect on the fatigue property.
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