The Investigations Of High Speed Grinding Mechanisms On AISI 1045 Steel Components With Narrow Deep Groove Structure

Components,with a depth-to-width ratio over 2 and a width no more than 4 mm,are widely applied in the small and mini type vane pump rotors.For traditional grinding process,the burn damage in localized zone,pure stability of the grinding wheel and the low yield for workpieces are the critical troubles in the grinding process,which restrict its application to some extent.Especially for plastic materials with the narrow-deep-groove structures,it is difficult for form grinding to meet a high surface quality requirement due to the disadvantages such as the large ductility of the material,grinding wheel blind,and the secondary scratch on the ground surface by the grain et al.It would be possible for it to present an opportunity to with the development of the high speed grinding technology because of a thicker depth of cut,a smaller grinding force on the single abrasive,a higher removal rate for material in the high speed grinding process.By using it,the accumulation of the rough and finish machining can be realized in one grinding process and the high quality of the ground surface will be obtained.The high speed grinding process is a suitable method for machining the parts with the narrow-deep-groove structures.To achieve grinding the plastic material with a high efficiency,the mechanisms of the action on the workpiece by a single CBN grain have been studied systematically in the paper.The loading model has been established.And the characteristics of the single grain grinding mechanism have been analyzed in various negative rake angles.The friction and wear behaviors of the ground surface with different initial roughness values have been studied for investigating the wear resistance using a pin on disc equipment.Then the plastic deform in the subsurface have been studied under the worn surfaces.The distribution of the residual stress in the ground surface has been disclosed with the experiment results.The main achievements and the innovation ideas in the paper are as following:(1)The grinding mechanisms of the single abrasiveAccording to the contact process between the grain and workpiece,the CBN grain has been simplified as a cone.The grain tip geometry shape has been simplified as a sphere,as well as the cone is available for grain body.Based on the model established,the equations of the tangential force and normal force in the grinding process have been deduced by using the grinding mechanisms.The grinding force ratio has been deduced in different part of the simplified model.And the characteristics of the grinding force have been analyzed in various geometry parameters of the simplified model.(2)The mechanism of the material removalFor plastic materials such as AISI 1045 steel,the constitutive behavior has been analyzed.The coefficients in Johnson-Cook constitutive relations of one dimensional stress have been revised with the trial results and the tensile results coming from experiments.By using the ALE algorithm of finite element,the processes of the thermal elastic-plastic couples between the single grain and the work material in high speed grinding process have been simulated with the Deform software.The plastic fracture energy of the AISI 1045 steel has been calculated according to the tensile stress results.Combining the crack criteria of Cockroft-Latham,the threshold of separation criterion between the chip and material has been determined.The process of material removal in the grinding process have been presented clearly in the chip deform simulation.(3)The grinding experiment with a single grainThe single grain grinding wheel with a diameter of 400 mm has been employed in the process of grinding AISI 1045 steel at various grinding parameters.The grinding force has been monitored with a 3D measuring cell.The temperature distribution has been detected with an infra-red thermograph.The chip formation has been observed to study the chip deformation in grinding process.The experimental results indicate that negative rake angle induce two type of chip geometry which are the curly shape chip and spiral shape chip.Grinding force has a strong sensibility when the grinding speed is changing.The experiment results and the simulation results have fine agreements,which can provide a foundation to be used in the production.(4)The optimization of the grinding parameterCreep grinding process had been conducted with an electroplating CBN grinding wheel at the high grinding speed.The depth of cut,feed rate and the grinding speed were investigated to obtain the perfect ground surface by using orthogonal experiments.The results show that larger depth of cut,creep grinding feed rate and high grinding speed can realize the low roughness value on the ground surface.Critical influence on the roughness value is the parameter of the grinding speed.And the depth of cut has little effect to the roughness value on the ground surface.Rational impact to the roughness is the parameter of changing the feed rate.(5)The investigation of wear resistance on the ground surfaceAISI 1045 steel narrow-deep-groove trial works have been machined in various grinding parameters.The surface roughness and surface topography have been detected.The pin on disc tests has been conducted to study the friction and wear behaviors of the ground surface with the different initial roughness values.The feed rate influence on roughness values and the surface texture have been investigated.And the time dependence of friction coefficient,initial-stable transition time has been explored.Base on the friction and wear behavior results,the plastic deformation in the subsurface have been studied.(6)The study of the residual stress in the ground surfaceBase on the micro grinding force model,the dynamic model for secondary cutting has been established in the high speed grinding process.The grinding feed rate influence on the ground surface has been analyzed with the detailed formulas.And the distributions of the residual stress in the subsurface have been disclosed.The results show that the residual stress along the feed direction is larger than that of one along the depth of cut direction.In the feed direction,the force acting on the surface by the single grain is the direct duplication,so the residual stress is increased.On the contrary,the force direction is the inverted repeats.Then the residual stress is weakened.