| Micro grinding of material surface micro structure in the process of machining deformation force thermal phase transformation and has great effect on residual stress and micro grinding surface and the surface residual stress is not only affect the stability of the workpiece geometry size,and affect the artifacts of the static strength and fatigue corrosion resistance and service life of the micro cutting depth and feed and workpiece material of grinding grain size in the same order of magnitude,the evolution of micro grinding surface performance closely related to the parts material microstructure,residual stress of metal damage micro cracks and fracture mechanics behavior can be found in the microstructure evolution of materialsOf analysis from micro-scale crystal effect on the material constitutive relation,thus creating the constitutive model and the relationship with macroeconomic performance,so as to solve the prediction and control the residual stress distribution and the size of the problem of material micro structure on flow stress and the influence of material removal in the process of material performance,including considering material dislocation density and grain size of the grain direction on the material flow stress analytical model of the study,however,grain direction of the flow stress,especially the study of the effect of residual stress and its analytical model,is still blank Based on micro grinding force in the process of thermal load and phase transformation relations as the breakthrough point,from the perspective of processing mechanism of deep understanding of the effects of important parameters on the grinding process,to the effect of grain orientation on micro grinding process and phase change and heat load and the influence of the complex relationship between residual stress research,from the perspective of control surface integrity,is proposed to consider the quality objectives of the fine grinding process optimization criterion,perfect for fine grinding process and its quality control method and theoretical basis.The main research results and innovations of this paper are as follows:(1)Establishment of Taylor factor model in micro-grinding.Based on the mechanism of metal micro-plastic deformation and the relationship between grain orientation and Schmidt factor in tensile test,a quantitative model of the influence of grain orientation on flow stress of single crystal material in micro-grinding,namely Taylor factor model,was proposed.By calculating the Taylor factor,the workpiece coordinate system was established to determine the grain orientation of the workpiece on the given surface and the crystal orientation of the given direction.Then,the crystal orientation of the grinding surface and the grinding direction was determined.Finally,the five slip systems that are most easily activated under load were determined.Based on the theoretical model of single crystal material Taylor factor,the volume distribution of polycrystalline material grain orientation is expressed by orientation density function.Based on phase analysis,the Taylor factor model of multiphase materials is obtained by calculating the volume fraction of the phase.(2)Establishment of analytical model of grinding force considering grain orientation.Based on the microstructure enhancement model,an analytical model of Vickers hardness and flow stress considering grain orientation is proposed.Based on the single particle grinding force model,considering the effect of flow stress on chip forming force and sliding friction force,the influence of grain orientation on the single particle grinding force is proposed.Then,based on the dynamic grinding particle density model of grinding wheel morphology,a grinding force model considering grain orientation was proposed.(3)Establishment of grinding temperature analytical model considering grain orientation.Based on the tangential force model and the contact arc length model,the total grinding heat was calculated.The heat entering the workpiece is obtained by calculating the chip specific grinding energy and the heat distribution ratio between workpiece and cutter.Then Peclet value and contact Angle were calculated to determine the heat flow distribution model of grinding surface and the temperature distribution in the workpiece was obtained through the quadratic Bessel function,so as to establish an analytical model of grinding temperature considering process parameters and grain orientation.(4)Build a phase transition model considering the influence of grain orientation.Based on the analysis of phase change crystallography,the influence model of grain orientation on phase change is proposed.Based on the experimental linear regression analysis,a phase transition model considering temperature,strain rate,temperature rise rate and grain orientation was obtained.Based on greenwoodjohnson(GJ)model,the strain generated by phase transition is calculated,and then a flow stress model considering phase transition strain is constructed.On this basis,the interaction mechanism between force,heat and phase transition is formed,so as to improve the prediction model of grinding force and heat in the micro-grinding process.(5)Residual stress model comprehensively considering the coupling effect of "force-thermal-phase transition".The hertz-rolling contact model was used to calculate the stress distribution caused by mechanical and thermal loads,and an analytical model of grain orientation to plastic modulus was constructed.McDowell hybrid algorithm was used to predict the distribution of residual stress after loading and releasing,considering the following hardening of materials and using the thermoelastoplastic increment model.The above research is based on mechanism analysis and an analytical model is established to deeply analyze the physical relationship between the independent variable and the controlled quantity in the micro-grinding process,so as to realize the reverse control optimization project and provide a reliable and effective guarantee for precision machining... |
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