Characteristic Analysis Of Superhard CBN Abrasive Tool And Study On Residual Stress Of High Speed Cylindrical Grinding

With the progress of the world's scientific and technological,the manufacturing has developed from traditional forming manufacturing to high-quality surface integrity manufacturing and anti-fatigue manufacturing.Grinding is a kind of precision / ultraprecision machining process,which requires the process not only meet the requirements in shape and position,but also achieve high surface integrity and long fatigue life of the workpiece.The high-speed / ultra-high-speed grinding process,which has broken through the limitations of traditional grinding,has become an important milestone in the grinding field and has played an important role in the efficient processing of high-quality parts.Abrasive tools,the main performers of the grinding industry,has a direct impact on the workpiece.The super hard abrasive CBN(Cubic Boron Nitride)has linked the surface integrity manufacturing to high-speed grinding processes.The tools has many types and their characteristics are different,so it is especially important to explore the characteristics of different CBN abrasive tools.In addition,residual stress,as an key parameter evaluation indexes of the surface integrity,which has a decisive effect on the fatigue life of the workpiece.Therefore,it is significant to study the effect of high-speed grinding technology on the residual stress.In this thesis,the sample of CBN abrasives is used as the research object.The characteristics of ceramics,resin bond,and different granularity are compared and analyzed.The specific implementation method is to test the wear resistance,flexural strength,Rockwell hardness of the sample through experiments.And the morphology of samples are used to measure the performance.So that the performance of different abrasive samples with different bond is compared laterally under the same granularity,and the performance of different abrasive samples with different granularity is compared under the same bond.Then,a ceramic bonding agent CBN grinding wheel was used to perform high-speed cylindrical grinding tests on 18CrNiMo7-6 carburized hardened steel,and the process parameters such as wheel speed,workpiece speed,feed rate,and the granularity are investigated the influence of the residual stress distribution on the sample and the reasons for the formation of the law was analyzed.Research indicated:1)The effective use of automatic grinding machines and the concept of MWR(Material Wear Rate)can better measure the wear resistance of abrasives;under the same granularity,the wear resistance and flexural strength of ceramic bond abrasives are lower than resin Bond abrasives.In addition to the granularity of 230/270#,the ceramic bond abrasives of 120/140# and W20 are also lower than the resin bond abrasives on the Rockwell hardness.In terms of wear resistance,the MWR of ceramic and resin bond abrasive tools increased with the increase of the granularity,showing better consistency and regularity;in terms of Rockwell hardness and flexural strength,for resin bond abrasives,both of which have a certain correlation,both decreased with increasing granularity,while ceramic bond abrasives,the 230/270# abrasives are special,with the highest Rockwell hardness and flexural strength,Respectively 80.33 HRB and 6.61 MPa.2)The high-speed grinding process can introduce compressive stress on the surface of the workpiece.The stress on the surface increases slightly with the increase of wheel speed.The effects of workpiece speed and feed rate are not monotonic.The stress distributions in the X and Y directions are basically the same,while the one in the Y direction is slightly larger than that in the X direction.The feed rate has a great influence on the stress distribution,with the thickness of the influenced layer reaching 100 ? 150 ?m,and the tensile stress appearing.Followed is the effect of the wheel speed.When the speed is 60 m/s,"a tower-shape" distribution is obvious.The workpiece speed has no influence rule.The granularity of 230/270# has a great influence on the stress distribution,the influence layer is about 80 ? 100 ?m,and the granularity of 120/140# and W20 on the distribution is close.The auxiliary fixture effectively improves the accuracy of the residual stress,and the detection efficiency is more than doubled.