Study On Bending Fatigue Of High Current Pulsed Electron Beam Hardened Gears

The situation of force is very complicated when gear works, so kinds of failures usually appear, such as pitting, peeling, gluing, excessive wear and bending fatigue fracture,while the bending fatigue fracture accounts for a large proportion of all failures. With the development of modern industry,the gears that with light weight but high strength are required. International study on the strength of gear are mainly in aspects of optimization of tooth shape and surface treatment on gear, under certain conditions, while the role of increasing the bending fatigue strength of tooth is limited through the optimization of tooth shape, and traditional surface treatment technologies also face some limitations, so it makes great importance to study the new surface treatment technologies that are applicable on gears.High-current pulsed electron beam (HCPEB) is a new and efficient surface modification technique. With its high energy density and high efficiency, changes of the surface structure are induced and the properties of the surface layer of materials can be improved directly and effectively. This article originates from a part of the project of National Natural Science Foundation of China,"the study on process and property of surface amorphized gears"(No.50775229). The grinded and non-grinded original gears are irradiated by HCPEB, and test of bending fatigue strength of the original gears and irradiated gears is carried out on high-frequency fatigue tester. The study on affect of HCPEB to bending fatigue of gears with different surface conditions is done in order to obtain the gear with longer life. Major works of the paper are as follow:(1) Summary of the main factors that influence the bending fatigue strength of gear.(2) The thermal-mechanical coupling method in finite element analysis software ANSYS is used to analyze the temperature and thermal stress distribution in 40Cr steel irradiated by HCPEB. The residual stress of the surface after repeatedly irradiation is given.(3) The grinded and non-grinded gears that with two kinds of surface condition are treated directly by HCPEB of which the parameters are optimized.(4) The test of bending fatigue strength of gears is carried out on all gears under the condition of constant amplitude load and the bending fatigue strength of grinded and non-grinded original gears is compared with that after irradiation.(5) The test of microhardness, surface roughness and surface residual stress, the observation of the surface and cross section of tooth root, microstructure are carried out to get the reasons for the alteration of bending fatigue properties of gears. The results indicate that bending fatigue strength of non-grinded gears decrease by a certain extent after irradiation by HCPEB, while it increase slightly after irradiation for grinded gears. The conclusion of the paper will play a guiding role in surface modification of gears.