Papers by Author: Xue Jun Chen

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Authors: Hai Wen Wang, Xue Jun Chen
Abstract: The interfacial stresses of a segmented Cr coating by the hybrid technique of laser pre-quenching steel substrate plus post-deposition have been investigated. The discrete laser quenched zones (LQZs) were modeled as multiple inclusions, each of which is embedded with a prescribed uniform eigenstrain. Based on the failure criterion of the adhesion strength, the interfacial stresses are considered to be responsible for interfacial debonding. The interfacial stresses were evaluated by using the finite element (FE) method. Dimensional analysis was utilized to identify the scaling variables affecting the stresses. The dependence of a range of dimensionless variables of interest on the interfacial stresses has been assessed through a detailed parametric study.
Authors: Ban Quan Yang, Xue Jun Chen, Wei Hai Sun, Hong Qian Chen, Jing Wen Pan, Ying Chen
Abstract: The fracture behavior of a brittle thin film on an elastic substrate under residual stress and uniaxial tensile loading is investigated. It is assumed that the residual stress in the thin film is not large enough to cause the thin film to fracture. Using a mechanical model presented in this work, the analytical solutions for the distribution laws of the tensile stress developed in the thin film, the shear stress developed along the interface and the relationship between the crack density of the thin film and the applied strain of the substrate can be obtained. The results presented in this work can provide a new analytic solution to the interfacial shear stress for characterizing the interfacial shear strength of the thin film/substrate system when the uniaxial tensile test is adopted to evaluate the mechanical properties of the thin film/substrate system.
Authors: Ban Quan Yang, Guang Nan Chen, Xue Jun Chen, Wei Hai Sun, Hong Qian Chen, Jing Wen Pan, Ying Chen
Abstract: The interfacial cracking behaviors of a chromium (Cr) coating/laser pre-quenched steel substrate system and a Cr coating/original steel substrate system under thermal fatigue loading were investigated in this work. The experiment results show that the Cr coating on the pre-quenched substrate surface exhibited a higher resistance of interfacial cracking than that of the Cr coating on the original substrate surface under the same loading condition. This indicates the technology of laser pre-quenching of steel substrate surface prior to plating the Cr coating can improve the interfacial adhesion properties between the coating and substrate.
Authors: Ban Quan Yang, Guang Nan Chen, Xue Jun Chen
Abstract: The initial micro-crack density of a chromium coating/steel substrate with and without laser pre-quenching treatment was investigated in this work. It was found the micro-crack density of Cr coating on the pre-quenched substrate surface was much lower than that of the Cr coating on the original substrate surface. Based on the results presented in this work and in the literature, the find presented in this work indicates the lower crack density of the chromium coating on the pre-quenched substrate may improve the mechanical properties of this material system, and it may be an important mechanism responsible for the prolonged lives of workpieces in practice.
Authors: Xue Jun Chen, Qi Liu
Abstract: In this paper, the finite element simulation of laser drilling process has been carried out for the nickel alloy DD6. Both the transient temperature field and thermal stress field were computed via the commercial software package ANSYS. Based on the method of dimensional analysis, the dependence of various non-dimensional parameters on both fields was specified and demonstrated in graphical forms.
Authors: Xue Jun Chen, Guang Nan Chen
Abstract: In this paper, the thermal shock induced cracking behavior of a segmented coating on the outer surface of a hollow cylinder has been investigated. The driving force for the propagation of multiple segmentation crack, represented by the Thermal Stress Intensity Factor (TSIF), was determined by combination of the principle of superposition and the finite element method. The maximum TSIF has been shown to occur neither at the beginning nor at the steady state of thermal transients, but at an intermediate instant. As the spacing between multiple segmentation cracks decreases, the magnitude of TSIF first plateaus, and then decreases sharply. This quantitative mechanistic result rationalizes the experimental observations that a segmented coating can exhibit much higher thermal shock resistance than an intact counterpart, if only the segmentation crack spacing is narrow enough. Some other parameters affecting TSIF, such as segmentation crack depth and convection severity, were also discussed.
Authors: Ban Quan Yang, Guang Nan Chen, Xue Jun Chen
Abstract: Adhesion of a coating on its substrate is a crucial parameter determining performance and reliability of coating-substrate system. In this work, the uniaxial tensile and cross-sectional indentation tests are used to investigate the adhesion between the brittle Cr coating and the ductile steel substrate. The uniaxial tensile test results show the maximum shear flow stress level of the ductile steel substrate can only serve as a lower bound estimate on the ultimate shear strength of the interface. The cross-sectional indentation test results show the interfacial decohesion does not occur prior to the cracking of the brittle Cr coating.
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