Fatigue Life and Stress Retro Estimation of 30CrMnSiA in Laboratory Environment

The fatigue life and fatigue stress of 30CrMnSiA material are studied by fracture retro estimation under experimental conditions. With the help of Scanning electron microscopy (SEM), fatigue crack can be observed. By Paris law, the fatigue life and fatigue stress of 30CrMnSiA material can be estimated by fatigue striation under the experimental environment. The method is simple and feasible, and the relative error is lower.

Fatigue Mechanism of Domestic 316LN Stainless Steel in Simulated AP1000 First-Loop Water Environment

Fatigue fracture surfaces and crack morphologies of 316LN stainless steel that test in a simulated AP1000 first-loop water and air environment were investigated by SEM, LSCM and EBSD. The results showed that, the fatigue crack initiated at persistent slip band, impurities and grain boundary, and then propagated in a trans-granular manner with typical fatigue striations. Characteristics of corrosion fatigue, such as brittle fatigue striation, rhomboid corrosion product and the trace of corrosions were found on the fracture surface of first-loop water environment specimen. The strain on first-loop water environment specimen is unevenly distributed surrounding the crack, and the gradient is not obvious, while that on air environment ones is evenly distributed , and the distribution gradient is associated with the distance of crack from . The fatigue crack propagation was accelerated in the first-loop water environment, and the EAC mechanism is most likely to be HIC.

The Fracture Failure Analysis of Shaft for Light Hydrocarbon Pump

The failure shaft for light hydrocarbon pump was analyzed through metallographica test. The fracture appearance was examined through 3-D stereoscopic digital camera and the scanning electron microscope (SEM). The results showed that the chemical composition of the shaft was fit to the requirement of structural steel. There was sulfide inclusion distributed among the white stripe phases. The figure of phases was striation, and the direction of striation was along the direction of the axis that was the machining direction when the shaft was fabricated. The fatigue fracture was the facture characteristic because there was fatigue striation on the fracture surface. The sulfide inclusion and segregation was the main reason of the fracture.

Fatigue Properties for Sinter-Hardened Fe-Ni-Mo-Cu Materials

Fe-4Ni-0.5Mo-1Cu powder was selected as raw material, pressed and sinter-hardened at 1135°C for 30 min with rapid cooling. The density varies in the range of 7.24-7.29 g/cm3. Its fatigue properties have been tested in axial loading of alternating tensile/compressive stress at R=-1 with a servo-pulse pump. The fatigue endurance limit was measured to be 260 MPa. The microstructure showed more homogeneous bainite and martensite. Neither Ni nor Mo rich areas were detected. Fractography displayed the fatigue cracks initiated from the pore areas near the surface. A nontypical ductile fatigue striation was found. More dimples occurred on fracture surface due to the plastic deformation, which can prohibit cracking propagation and improve its fatigue properties.