Papers by Author: Jun Liu

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Authors: Yong Shou Liu, Jun Liu, An Qiang Wang, Zhu Feng Yue
Abstract: In this paper, an amendment method for stress and strain of double-curved laminated composite is proposed and studied. According to finite element analysis results of the same model with two different mesh size (coarse mesh size 120mm× 300mm and refined mesh size 30mm× 30mm ), stress and strain have been amended with modified formula in user material subroutine (UMAT) subprogram so that the corrected results of model with coarse mesh is similar to the results of model with refined mesh. Using this method, with coarse mesh, a satisfied accuracy results still can be obtained without refining mesh. It’s efficient for design and analysis of complex structures.
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Authors: Yong Shou Liu, Jun Liu, Xiao Jun Shao, Zhu Feng Yue
Abstract: The fatigue testing of the specimen with a central open hole was carried out to investigate the influence of the surface roughness on the fatigue lifetime. Fracture morphology investigations were used by scanning electron microscope. The reliability analysis of the specimen was carried out by detail fatigue rating. The results revealed that the less the roughness is, the longer the fatigue life of open hole and the higher the value of DFR (Detail Fatigue Rating) is. Under the same technological conditions, the effect of corner crack on fatigue life of open holes is greater than the effect of internal crack. So, the effect of a decrease of roughness on the fatigue life of an open hole is similar to a change of crack type from a corner crack to an internal crack.
757
Authors: Xiao Jun Shao, Jun Liu, Yong Shou Liu, Zhu Feng Yue
Abstract: A 2D cylindrical plate model has been established to study the distribution of residual stress of cold expansion hole under different interference values. In addition, the effects of material models on residual stress fields are considered also. Experiments are carried out to measure the residual stress of cold expansion hole and verify simulation results. FEM results show, with interference values increasing, the higher residual radial and circumferential stresses are obtained. At same interference value, the residual stress of Hardening Material( HM ) model is much larger than that of Elastic Perfectly Plastic Material( EPPM ) model.
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Authors: Xiao Jun Shao, Jun Liu, Yong Shou Liu, Zhu Feng Yue
Abstract: A 2D rectangular plate model has been established to study the residual stress fields of cold expansion hole. Experiments were carried out to measure the residual stress of cold expansion hole and verify simulation results. The FEM results show, with interference values developing, the maximum values of circumferential residual compressive/tensile stress increase and higher positive stress values are obtained at the boundary of the rectangular plate. However, higher positive stresses at the boundary of plate are harmful to the capacity of fatigue resistance, the determinations of best interference value to a certain wide plate were proposed. Finally, the effect of the plate width on the residual stress distribution was analyzed.
745
Authors: Jun Liu, Yu Long Li, Fei Xu
Abstract: This paper is focused on the development of an effective numerical method to simulate bird-impact aircraft windshield events. A new Smooth Particle Hydrodynamics (SPH) which has been incorporated as a solver option into the explicit finite element program PAM-CRASH was used to model the bird. The deformation between the numerical results and the experimental results is in good agreement. Simulation results of a bird-impact process indicated that the SPH bird model is more suitable to model the break-up of the bird into particles. Failure of the windshield in the experiment was simulated, and the good agreement between the numerical and experiment indicates that the failure model established in the present paper is reasonable. Finally, the energy changes of the bird and the windshield were calculated.
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