Effect of pre-corrosion on the fatigue fracture behavior of ER8 wheel steel

The salt spray pre-corrosion test was carried on the fatigue specimens of ER8 wheel steel, and then fatigue experiment with a stress ratio (R) of 0.1 was conducted. The fractures were characterized by field emission scanning electron microscopy. The results show that pre-corrosion significantly reduces the fatigue limit of the rim material, the main crack-induced fracture mechanism occurs under pre-corrosion conditions for 6 h at a lower stress, and the fracture mechanism of multi-crack interactions occurs at a higher stress after pre-corrosion for 48 h. For pre-corrosion fatigue test, cracks originate from pitting pits. Then, multiple fatigue crack nucleations expand from different orientations in the transgranular fracture mode, forming cleavage facets.

Stress analysis of a functionally graded magneto-electro-elastic strip with multiple moving cracks

This paper investigates the linear steady state problem of several moving cracks in a functionally graded magneto-electro-elastic strip subjected to anti-plane mechanical and in-plane electric and magnetic loading. For simplicity, it is assumed that the properties of the strip vary continuously according to exponential functions along the thickness of the functionally graded piezoelectric piezomagnetic (FGPP) layer. By combining the dislocation method and integral transform technique, an exact solution in closed form to this problem is obtained. Electro-magneto-mechanical loads are applied on the crack surfaces, which are assumed to be magneto-electrically impermeable. Numerical examples are presented to show the interesting mechanical and electromagnetic coupling phenomena induced by multi-crack interactions. Finally, the effects of crack velocity, material constants, and geometric parameters upon the field intensity factors are studied. The results are useful for the design of the magneto-electro-elastic structures.

Deterministic and Probabilistic Investigation on Multiple Crack Interactions in a Semi-Infinite Domain

The investigation of multiple crack interactions in fracture mechanics is important to predict the safety and reliability of structures. This study aims to investigate the interactions of multiple parallel cracks in a semi-infinite domain in both deterministic and probabilistic ways by using an automated finite element modeling procedure and the Monte Carlo simulation. The stress intensity factor is considered as an indicator of failure and accurately evaluated by using the domain integral technique. The variation of the stress intensity factor according to the position, the length, and the number of cracks is demonstrated. In a probabilistic investigation, the effects of the number of cracks, the random distribution of the crack lengths, and the crack interactions to the failure probability are studied for a semi-infinite domain. The stress redistribution among multiple cracks, the effect of unevenly distributed crack lengths, and the combined effect of crack length uncertainties and a crack shielding effect have been examined.