Experimental Research on the Surface Quality of Milling Contour Bevel Gears

Contour bevel gears have the advantages of high coincidence,low noise and large bearing capacity,which are widely used in automobile manufacturing,shipbuilding and construction machinery.However,when the surface quality is poor,the effective contact area between the gear mating surfaces decreases,affecting the stability of the fit and thus the transmission accuracy,so it is of great significance to optimize the surface quality of the contour bevel gear.This paper firstly analyzes the formation process of machined surface roughness of contour bevel gears on the basis of generating machining method,and dry milling experiments of contour bevel gears are conducted to analyze the effects of cutting speed and feed rate on the machined surface roughness and surface topography of the workpiece.Then,the surface defects on the machined surface of the workpiece are studied by SEM,and the causes of the surface defects are analyzed by EDS.After that,XRD is used to compare the microscopic grains of the machined surface and the substrate material for diffraction peak analysis,and the effect of cutting parameters on the microhardness of the workpiece machined surface is investigated by work hardening experiment.The research results are of great significance for improving the machining accuracy of contour bevel gears,reducing friction losses and improving transmission efficiency.

Characterization of machined surface quality and near-surface microstructure of a high speed thrust angular contact ball bearing

Bearings are one of the most important components in modern industry.Rolling contact fatigue(RCF)initiating from surface and subsurface is the major failure mode.In this paper,a typical high speed thrust angular contact ball bearing was selected,and the machined surface quality and near-surface microstructure of the race-way and rolling ball were systematically characterized by using of a probe surface profiler,white light interferometer,optical microscopy(OM),scanning electron microscopy(SEM),electron backscatter diffraction(EBSD)and transmission electron microscopy(TEM)combined with focused ion beam(FIB).Two kinds of precursor,probably resulting in pitting or spalling during the following rolling contact,were detected.One is the defects on the surface of either the race-way or the rolling ball,such as heavy machining marks,scratches and slag-hole.The other is nano-crystalline layer due to machining,in the outermost layer around the surface of race-way.The results may well lay foundation for our further research on RCF with the real part of such typical rolling bearings.

Status of research on non-conventional technology assisted single-point diamond turning

With the increasing use of difficult-to-machine materials in aerospace applications,machining requirements are becoming ever more rigorous.However,traditional single-point diamond turning(SPDT)can cause surface damage and tool wear.Thus,it is difficult for SPDT to meet the processing requirements,and it has significant limitations.Research indicates that supplementing SPDT with unconventional techniques can,importantly,solve problems due to the high cutting forces and poor surface quality for difficult-to-machine materials.This paper first introduces SPDT and reviews research into unconventional techniques for use with SPDT.The machining mechanism is discussed,and the main advantages and disadvantages of various methods are investigated.Second,hybrid SPDT is briefly described,which encompasses ultrasonic-vibration magnetic-field SPDT,ultrasonic-vibration laser SPDT,and ultrasonic-vibration cold-plasma SPDT.Compared with the traditional SPDT method,hybrid SPDT produces a better optical surface quality.The current status of research into unconventional techniques to supplement SPDT is then summarized.Finally,future development trends and the application prospects of unconventional assisted SPDT are discussed.

Research on feed-pulse collaborative control method in micro-electrical discharge machining

Reducing the short-circuit rate and increasing the effective discharge rate are important targets for improving the servo control effect of micro-electrical discharge machining(micro-EDM),as these two indicators are closely related to the machining efficiency and quality.In this study,a feed-pulse collaborative control(FPCC)method is proposed for micro-EDM based on two dimensions(space and time).In the spatial dimension,a feed control strategy with a discharge holding process is adopted.Meanwhile,in the time dimension,a forward-looking pulse control strategy is adopted,in which the pulse interval is adjusted based on a sequence analysis of feed commands and discharge states.Process experiments are carried out to determine the key parameters used in this method,including the discharge holding threshold and pulse interval adjustment value(T_(off_(adj))).The feed smoothness and discharge sufficiency analyses of the experimental results show that compared to the traditional double threshold average voltage method,the FPCC method reduces the number of long-distance retreats by 64%and improves the effective discharge time by 40%.