Simulation And Experimental Study Of Temperature Field In Thread Forming Grinding Of Nickel-based Superalloy

Nickel-based superalloy hollow shaft components are important parts of aero-engines,which are slender shaft parts of tough and difficult-to-machine materials.Due to the complex heat source and the high thermal gradient of the grinding surface in the contact area of thread forming grinding,the external thread of nickel-based superalloy hollow shaft is prone to local burns during the grinding process.In order to solve this problem,this paper studies the temperature field of thread forming grinding of nickel-based superalloys,and establishes a simulation model of the temperature field of thread forming grinding by combining theory and experiment.The simulation model is used to analyze the temperature distribution characteristics and changing laws in the process of thread forming grinding,and discusses the influence of the heat source inclination on the temperature field.The process parameters of thread forming grinding are optimized according to the simulation model,so as to avoid grinding burns and improve the thread grinding efficiency.The main contents of this paper are as follows:(1)The experimental conditions of cylindrical annular groove grinding and thread forming grinding of GH4169 nickel-based superalloy are introduced in detail,including the properties of the experimental materials,the specifications of the specimens,the parameters of the experimental equipment,the types of grinding wheels and dressing methods,and the measurement methods of the grinding process parameters(grinding power,grinding temperature).(2)A model of the heat flux density distribution on the contact surface of wheel and workpiece is established.Firstly,the contact relationship between the forming grinding wheel and the workpiece is analyzed,and the calculation formula of the interference depth and geometric contact arc length between the grinding wheel and the workpiece along the thread profile is deduced.Then,based on the grinding power of the GH4169 nickel-based superalloy annular groove grinding experiment,an empirical formula for the circumferential force per unit width of the grinding wheel is established,and the thread grinding force distribution model was obtained.Then the heat distribution ratio model was used to determine the proportion of heat introduced into the workpiece along the grinding contact area.Finally,a three-dimensional heat flux distribution model on the contact surface of the thread forming grinding is constructed,which provides theoretical support for the subsequent simulation research of the thread forming grinding temperature field.(3)The temperature field simulation model of thread forming grinding based on life and death unit technology was established and verified by experiments.The influence of the heat source inclination on the temperature field is discussed,and the distribution characteristics and changing laws of the temperature field in thread forming grinding are revealed.The results show that the maximum temperature deviation between the simulation and the experiment for the rough grinding,semi-finishing and finishing grinding of thread grinding is around 10%,and the junction of the oblique side of the thread groove and the bottom corner of the arc is the area with the highest grinding temperature,which is more prone to burn.(4)The temperature field simulation model of thread forming grinding was used to predict the variety of the temperature field under different processing parameters.According to the simulation results,the process chain parameters of thread forming grinding were optimized,and the thread forming grinding verification experiments were carried out.Surface integrity was tested and evaluated.The results show that the optimized grinding parameters based on the grinding temperature field simulation model can avoid the burn of thread grinding of nickel-based superalloy and obtain high-quality surface integrity.