Papers by Keyword: Plastic Zone

Abstract: A mode I, centre crack, in ductile steel plate of finite dimensions is modeled in ANSYS software. Non-linear stress-strain data of steel are used. Plane strain case is adopted. A suitable value of far field tensile stress (pressure) is chosen such that EPFM condition prevails at the crack tip. Process and plastic zones are obtained at the crack tip. Desired values are noted. Areas of high stress and high strain are identified. Validation of void nucleation taking place ahead of crack tip and not exactly at the crack tip and coalescence of voids happening at the crack tip are confirmed from the results. Plots between the distance of desired location from the crack tip and load line stresses and strains are drawn. The plots are in accordance with the expectations.

Abstract: An approach to the development of the full-scale specimens for an experimental method to determine the residual stresses in the circular grooves of body parts is described. The selection of the specimen shape is based on the fulfillment of the geometric and force similarity conditions. The form of a surveillance specimen and loading conditions are proposed, during which all the equally-spaced points of the specimen experience an equal stress-strain state. This approach enables to correctly determine the residual stress levels for various methods of the part machining by cutting.

Abstract: Mathematical modeling of plastic deformations in rolling consists in a consequent combination of the general energetic relationship in plasticity and the variation inequality expressed the principle of minimum of entire deformation energy. A real deformation state in a plastic zone beneath rolls and corresponding kinematic and dynamics conditions on the contact surface are considered as a limited one for the consequent approximate deformation states and are found out by the method of approximated approach. Any realization of this method on personal computers requires a rational construction of a kinematic-possible velocity field in the spatial domain on plastic flow. Using the ordinary propositions and a new assumptions the authors have constructed a simple kinematic-possible velocity field in the plastic zone beneath rolls. On the base of the consequent approach in which the general energetic relationship and the variation inequality are interrelated the authors have been able to find out the geometric, kinematic and dynamics characteristics of plastic deformation’s states in metal rolling.

Abstract: Plasticity zone at crack tip of aluminum alloy with fcc structure is investigated in order to analyze the effect of crystal orientation to the plasticity distribution on crack tip, as well as the effect to CTOD and J-integral, which is implemented using finite element code in Abaqus with a rate dependent crystal plasticity theory. The results show that the crack tip plasticity, stresses and CTOD are significantly affected by grain orientations. When the grains have single textures, Cube and S orientations have a strong ability to against crack propagation. However, when the grains combine textures, the increasing of misorientation enhances the resistance for crack growth. And when the tilt angle is higher, the crack deflection is promoted to reduce the crack propagation rate.

Abstract: Plastic zone around a fatigue crack in AISI 304 stainless steel was studied experimentally using nanoindentation and numerically by the finite element analysis. Results obtained from one experimental observation of crack propagating under constant amplitude loading showed that nanohardness can be correlated to strain hardening caused by the cyclic deformation in the vicinity of the crack. However, for the material chosen for this study, exact plastic zone shape is hard to evaluate due to the scattering of experimental results.

Abstract: The work presents the results of the analysis of fatigue crack growth in flat steel samples for different strain conditions on crack tip in the sample. Growth of fatigue crack in the samples was studied in conditions of a plane strain state, plane stress state and in the transitory zone between those states. Test results showed a clear influence of these conditions on the fatigue crack growth rate. The paper also includes the test results of effectiveness of retardation of fatigue crack growth after single overload cycles used in different strain conditions.

Abstract: The Haokou power station is located in the south of Wu Long in chongqing, which is a medium-sized hydropower project given priority to electricity. The Dam located in south bank of Wujiang river downstream of Furong river has the catchment area of 7400 km², total capacity of 94.12 million m³, installed capacity of 125 MW power . After the excavation of the main building, trailing edge to form 30 m high rock slope is tangential. Slope rock mass is given priority to with weakly weathered shale, mudstone, shallow accumulation horizon, thickness is about 0.5 m to 6.0 m. In analysis of slope stability, the FLAC 3d and the strength subtraction method was used. Considering of gravity, the shore web of pressure, water pressure and reinforcement bolt load combination, the stress response, displacement response, plastic zone as well as the safety factor of slope was analyzed. The calculation results show that the slope is stable.

Abstract: By theoretical calculations, numerical simulation and field monitoring methods to analyze the stress distribution and the extent of damage of coal pillar determine a reasonable size is about 10m, can improve the recovery rate of coal resources, and to ensure the roadway stability. 10m pillar coal resources compared with the previous 20m pillar recovery increased by about 5.5%, and created tremendous economic benefits of the mine.

Abstract: At present, there is a lot of research for slope stability, the inherent reason of slope instability is geotechnical material will get plastic deformation under load. In this paper, Mohr- Coulomb yield condition is transformed strain expressed to stress expressed.Based on this, analysis the effects that geotechnical material parameters internal friction angle ,cohesion c and Poisson's ratio to Mohr- Coulomb yield condition and the development of soil plastic zone.In addition, using the strength reduction FEM simulating the change of plastic zone distribution caused by change of the geotechnical materials parameters .The results show that the internal friction angle , cohesion c are reducted, the plastic zone expand;Increasing the Poisson’s ratio , narrowing the slope’s plastic zone;Plastic zone’s different distribution is caused by different material parameters affect the yield surface.

Abstract: To research the deformation regularity of large section loess tunnel in construction procession with different construction methods, 3D Numerical Simulation is applied and the large-section loess tunnel of highway is taken as an example. Comparing deformation regularity of surrounding rock in three types of construction method conditions, the research results show that:The CRD method takes precedence in the condition of the convergence of surrounding rock is large. The both sides heading method takes precedence in the condition of ground surface settlement is large.