The numerical simulation of the Y-type three-roller two stands cold rolling stainless steel/carbon steel double metal composite seamless steel tube process was conducted through the finite element analysis of the elastic-plastic by applying the MSC.MARC software. Based on the numerical simulation, the character of stress and strain distribution parameters during the Y-type three-roller two stands cold rolling were obtained by the finite element analysis, and acquired the section pass deformation figure. The distribution of the axial stress, circle stress and radial stress were drawn below the Y-type mill along the circle. The mechanism of the tube cold rolling process and the effect of the forming steel tube both the diameter and wall thickness accuracy were explained according to the stress distribution. The results of the research can be applied to the design of the technical parameters in the forming process.

Cartilage with complex structure is a porous viscoelastic material. The direction of arrangement of collagen fibers in different layer regions directly affects the mechanical properties of the cartilage layer region. It is very important to use the method of numerical simulation for studying cartilage damage and repair through experimental measurements of cartilage mechanical parameters of the different layers. Because of the relatively small size of the cartilage, it is very difficult to measure mechanical parameters of cartilages by tensile test. The paper for main problems in the tensile test of cartilages, first by porcine articular cartilage compression testing, measuring the displacement of cartilage areas of different layers, according to the characteristics of the displacement determines the size of areas of different layers of cartilage, and then designed the cartilage and substrate stretching models. Model includes two forms of direct bonding and embedding bonding to simulate stretching process of different layers of the cartilage area in numerical way, displacement fields and stress-strain fields of stretching cartilage in different layer regions are derived. The numerical results show that using the way of embedded bonding can make stress of articular well-distributed without stress concentration, so it is a good way of bonding methods. Paper of the research work laid the foundation for measuring mechanical parameters of cartilage by stretch experiment.

Objective To understand the stresses distribution and process of damage evolution of both matrix and fiber in the defect cartilage under load of compression. The numerical results may provide a reference to both of the design for cartilage alternatives and clinical repair of defect cartilage. Methods The thickness of different layers of cartilage was obtained by a kind of experiment, in which the displacement in different layers zone cartilage under the compression load was obtained by the digital correlation technique. The multi-layer cartilage model with fiber and defect was established by the multi-physics analysis software ANSYS, with the different layers of the cartilage refer to the experimental results. According to the strength condition, the cartilage damage evolution process was simulated by the method of modifying the stiffness of the elements. The influence of the different defect depth to the damage evolution of cartilage was considered in parameter study. Result The simulation results have shown that the stress distribution in matrix was related to the cartilage defect depth. The minimum stress was distributed in the deep areas and below the damage area, stress concentration was located in the both sides of the defect area in the cartilage matrix, and the damaged area developed gradually from surface to deep, the maximum stress located at both sides of defect area. The stress distribution of cartilage fibers related with their location, the compressive stresses are mainly distributed in the middle and deep area, which are greater than those of undamaged. Conclusion In the process of damage evolution, the damaged area gradually developed from the surface to the deep. In the case of defect value of 60%, the maximum equivalent stresses in matrix will be increased in the process of damage evolution; in the case of defect value of 5%, the maximum axial stresses in fibers will be increased in the process of damage evolution.