Study On Surface Integrity Of Tungsten Alloy Processed By Ultrasonic Elliptical Vibration Cutting

Tungsten alloy is extremely attractive for industrial and aerospace applications owing to its excellent material properties,including high density,strength,and good ductility,formability,corrosion resistance,thermal stability.As high-quality processing surface is critical to the service performance of alloy parts,the tungsten alloy parts with nanometer-level surface roughness are required in nuclear industries and precision physics experiments.In the process of conventional cutting tungsten alloy,problems such as surface roughness deterioration,chip adhesion,and high cutting resistance are unavoidable,limiting potential applications of tungsten alloy.Therefore conventional cutting has been unable to meet the requirements for high-quality processing tungsten alloy.Ultrasonic elliptical vibration cutting(UEVC)is a new machining technology that can not only effectively reduce the cutting force and temperature,but also significantly improve the surface quality of the workpiece,the durability of the tool,and the stability of the processing system.Therefore,the surface integrity of tungsten alloy processed by UEVC were studied in detail in this paper.The main research contents are as follows.(1)Based on the Hopkinson compression bar test,the dynamic mechanical properties of tungsten alloy with different strain rates and temperature conditions were analyzed.The study found that tungsten alloy is a material that is sensitive to strain rate and temperature.Strain rate strengthening effect and temperature softening effect were shown under the conditions of high strain rate and temperature loading,and the microstructural alterations of the corresponding sample became severer with the increase of strain rate and temperature,which provides a theoretical basis for the subsequent explanation of the evolution mechanism of the microstructure,dislocation density and surface hardness of the tungsten alloy surface layer processed by ultrasonic elliptical cutting.(2)In order to study the formation mechanism of the surface morphology and the effects of ultrasonic elliptical vibration on the cutting surface topography and roughness,ultrasonic elliptical vibration cutting tungsten alloy experiments were conducted based on single factor experiments by comparing with conventional cutting and different process parameters.The results showed that the surface roughness using ultrasonic elliptical vibration cutting was increased with the depth of cut and feed rate increasing.Compared with conventional cutting,ultrasonic elliptical vibration cutting could effectively suppress the generation of scaly spines and furrows,reduce the surface roughness and improve the surface quality.(3)Based on a variety of material characterization techniques,the effect of process parameters on the surface layer microstructure,dislocation density,surface hardness and residual stress of tungsten alloy processed by ultrasonic elliptical vibration cutting was systematically studied.The results showed that the surface dislocation density,hardness and residual stress of the workpiece processed by ultrasonic elliptical vibration cutting were all increased with the depth of cut and feed rate increasing and the workpiece will experience large strain and high strain rate,which would lead to a certain degree of plastic deformation and grain refinement.Compared with conventional cutting,the dislocation density,surface hardening and residual compressive stress of the workpiece processed by ultrasonic elliptical vibration cutting were higher.In addition,the workpiece generated less subsurface damage.