Experimental Study On Surface Quality Of Extrusion Cutting For High-speed And Heavy-load Brake Disc

High-speed and heavy-load disc brake is widely used in large-scale machinery,such as large megawatt wind turbine,high-speed train and heavy-load truck.It plays an important role as the key friction couple of disc brake.Present problems such as poor fatigue resistance,serious surface wear,insufficient surface friction usually lead to too long braking distance in the working process of brake disc with traditional processing technology.It couldn’t meet the service requirements of brake disc under high-speed and heavy-load condition.In order to solve the above problems,this study uses the extrusion cutting method to carry out the cutting experiment on the surface of the workpiece,and analyzes the influence of the extrusion cutting on the surface quality of the brake disc.Specific research contents are as follows:(1)According to meet the requirements of high-speed and heavy-load brake disc with good fatigue resistance,sufficient friction and high contact strength,a method of cutting brake disc surface by extrusion cutting technology is proposed to obtain high-quality contact surface based on the principle of extrusion cutting.Q345B as a common material of brake disc is selected as the experiment material.Then sharpen high speed steel cutters with different angles.Three indexes of surface roughness,residual stress and work hardening are selected to design the single factor experiment scheme and the orthogonal experiment scheme considering the five factors of cutting speed,cutting edge radius,cutting depth,rake angle and back angle of the tool,in order to prepare for the analysis of the following experimental data.(2)The effects of cutting speed,cutting edge radius,cutting depth,rake angle and back angle of the tool on cutting force and cutting heat in the cutting process are firstly analyzed based on single factor experiment data,aiming at the characteristics that extrusion cutting process can increase the extrusion effect while cutting the surface,thus the relationship between cutting parameter and roughness,residual stress and work hardening is established by analyzing the influence of cutting force and heat on surface quality.Then we successfully obtain the influence law of cutting parameters on surface quality.It is found that the extrusion cutting makes the machined surface produce greater residual compressive stress and hardening through the analysis of the rule,meanwhile,the surface roughness has been greatly improved,which meets the requirements of the surface quality of brake disc.(3)The surface roughness is analyzed by the definite purposed character of signal-to-noise ratio analysis based on the orthogonal experiment data according to the requirements of the surface quality of the brake disc.The residual compressive stress and microhardness are analyzed by the larger-the-better character of signal-to-noise ratio analysis,and the influence degree of cutting parameters on roughness,residual stress and microhardness is analyzed by variance analysis.The best combination of parameters under single target is obtained based on above.The multi-objective optimization of process parameters is transformed into the single-objective optimization of process parameters by means of grey relational degree analysis.The optimal combination of parameters is obtained under the comprehensive consideration of surface roughness,residual stress and microhardness.Meanwhile,the optimization results are verified by experiments which explain that the surface quality of workpiece has been significantly improved.In summary,this study mainly starts from revealing the principle of extrusion cutting technology for high-speed and heavy-load brake discs,and analyses the influence of cutting parameters on surface quality by single factor experiments,and optimizes the process parameters by orthogonal experiments.It has important guiding significance for processing high quality brake disc surface in the future.