XFEM Analyses Using Two-Dimensional Quadrilateral Elements Enriched with Only the Heaviside Step Function

In the framework of the extended finite element method, a two-dimensional four-node quadrilateral element enriched with only the Heaviside step function is formulated for stationary and propagating crack analyses. In the proposed method, two types of signed distance functions are used to implicitly express crack geometry, and finite elements, which interact with the crack, are appropriately partitioned according to the level set values and are then integrated numerically for derivation of the stiffness matrix and internal force vectors. The proposed method was verified by evaluating stress intensity factors, performing crack propagation analyses and comparing the obtained results with reference solutions.

Micro-Crack Analyses of Chromium Steel JIS-SCr 420 for Helical Gear Transmission

This research aims to investigate micro-crack on a failed for helical gear transmission which was to adjust the engine to increased horsepower. The helical gears made are from chromium steel JIS-SCr 420. The spectrophotometer test machine was used to detect chemical composition, Mechanical properties were evaluated by Vickers hardness and microstructural analysis with an optical microscope, which the crack of the surface layer and energy dispersive spectroscopy using a scanning electron microscope. The results showed that the fracture characteristic of the helical gear’s surface was expected to beach marks and break away. It can be seen that the mixing failure area of oxide inclusion with carbide surrounding before the liquid state of material will be solidified which caused the failure cause of this helical gear. The summary analysis results can be accorded with the assumption of this research and which help prolong service life of the component.