Experimental Investigate On The Ultrasonic Turning Process And Surface Machining Quality Of Cemented Carbides

Cemented carbide becomes the indispensable structural material in aerospace field,national defense and military industries,and instruments and apparatus domain due to the high strength,better abrasion resistance and other superior mechanical performance.However,the brittle characteristic and lower fracture toughness lead to greater cutting force and high cutting temperature during machining,and it is also more likely to provoke residual tension on the machined surface.It is the fundamental problems that restrict the technology development of precision machining of difficult-to-cut material with efficiency.This dissertation studies two-dimensional ultrasonic assisted turning of cemented carbide,and aims for the characteristics of kinematics,cutting force,cutting temperature,surface roughness and residual stress during the processing.The research details are as follows:1.The research studies the processing mechanism of two-dimensional ultrasonic assisted turning.The motion trajectory model,cutting force model and cutting temperature model are established.On the basis of formation mechanism,the analytical model of residual stress is achieved by loading and releasing stress.2.On the basis of thermal-mechanical coupling,this research establishes the Finite Element Model(FEM)of ultrasonic assisted turning of cemented carbide.The cutting force,cutting temperature and residual stress are simulated by Abaqus.The simulation analyzes the influence rule of the tool's geometrical parameters and the characterization parameter of ultrasonic vibration on cutting force,cutting temperature and residual stress,and the result shows that ultrasonic turning enhances the residual compressive stress effectively on the workpiece surface and the maximum residual compressive stress inside,in the meanwhile,the depth of compressive stress layer is increased as well.3.The two-dimensional ultrasonic vibration system is developed based on acoustic theory,and then set up the experimental installation.By experimental method,the difference between conventional and ultrasonic turning is analyzed,and it also reveals the impacts of technological parameters and ultrasonic amplitude for cutting force and temperature.In consideration of factors interaction,both orthogonal and single-factor experiments are used to study the degree of influence of cutting parameters on cutting conditions,on cutting force,temperature and residual stress.4.Based on genetic algorithm,this paper establishes the forecast model of surface roughness and residual stress of ultrasonic assisted turning,and verifies the availability by experiments.Concerning both surface roughness and processing residual stress,this research optimizes the cutting parameters by taking the maximum residual compressive stress and surface roughness as target variable and bound variable respectively.The optimized parameters under different surface roughness constraint value are obtained.