| Sintered metal porous materials appeared at the beginning of the 20 th century.Because of their excellent light weight,permeability,capillary properties and high strength of metal materials,sintered metal porous materials are a kind of new materials with special properties which have been developed rapidly in recent years.However,due to the high hardness and difficult machining of stainless steel materials,the existing sintered stainless steel porous materials are mainly made of spherical metal powder prepared by chemical reduction method.It is difficult to maintain high porosity and ensure high strength of materials,which limits its application and development to a certain extent.Elliptical vibration cutting(EVC)is a new machining method for ferrous metals and brittle materials,which can be used to produce micron scale chip particles.Therefore,based on the research of chip particles produced in the process of elliptical vibration turning,a new type of sintered stainless steel porous material preparation technology with large void ratio and high strength is proposed in this paper.Firstly,based on the dynamic modeling and stiffness calculation of flexible mechanism,a high-precision two-dimensional elliptical vibration cutting system driven by piezoelectric stack and dynamically monitored and compensated by displacement sensor is developed,including the overall design of the device and the size design and calculation of flexible hinge.The finite element software is used to simulate and analyze the device model,and the test system is built to test the static stiffness,natural frequency,step response,sinusoidal response and elliptic trajectory synthesis performance of the device,so as to ensure that the XII performance of the device can meet the needs of cutting experiments.Secondly,the mathematical model of elliptical vibration trajectory of input signal to the tool tip is established,the preparation conditions of micro chip particles are analyzed,and the thickness formula of chip particles in different planes is deduced,so as to obtain the reasonable selection range of cutting parameters.The designed elliptical vibration mechanism is installed on a precision CNC machine tool to cut the end face of austenitic stainless steel bar to obtain micron sized austenitic stainless steel micro chip particles with rich microstructure.The effects of main cutting parameters such as vibration frequency,nominal cutting depth,feed rate and spindle speed on the surface morphology of micro chip particles were investigated through a number of comparative experiments.A set of optimal cutting parameters were obtained for machining micro chip particles which can be used for sintering stainless steel porous materials.Finally,a set of pressing die was designed and manufactured,and the prepared micro chip particles were pressed into the forming compacts under the press.The obtained compacts were sintered in the vacuum environment by the step heating method.The microstructure of the surface of the micro chip particles is conducive to the formation of the sintering neck and small pores between the particles during the sintering process,so that a new type of micro chip particles sintered stainless steel porous material(MCP-SSSPM)with the characteristics of large porosity and high strength can be obtained.Different experiments were designed to test the porosity,compressive strength and machinability of the prepared MCP-SSSPM samples.The results show that the porosity of the porous material reaches 36%,while the compressive strength reaches 82 MPa.At the same time,it also has good machinability.The machined surface is not easy to fracture,and the tool wear is low.These characteristics are conducive to its application in light load mechanical transmission such as gear transmission,and improve the vibration damping and lubrication performance of mechanical structure. |
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