Research On Contact Fatigue Strength Of Gear And The Effects Of Defects On Strength

At present, with the mechanical industry constantly move forward, the performance of the drive gear, such as reliability, stability, life span, weight and strength are put out new and higher requirements. So all sorts of new material, new technology are widely applied to the gear design and processing.35 CrNiMo steel surface induction hardening gear as the important gear of three gorges ship lift transmission system, in order to guarantee the working performance of the new material gear, have to make the necessary theoretical analysis and experimental research. In this paper, the main research content:(1) Contact fatigue strength test of 35 CrNiMo steel surface induction hardening gear was finished in a closed power flow fatigue test machine. This paper mainly discussed the test condition, test method and test process, etc. Based on normal fatigue pitting failure of gear under the experiment, this paper discusses the causes of gear pitting, failure criterion and test method. This paper briefly introduces the problems existing in the testing process, and proposed the corresponding solution.(2) Based on the theory of probability and mathematical statistics theory, combining with the characteristics of the service life of gear and with the help of Labview graphical programming software, making the gear test data processing system.The system integrated the probability distribution hypothesis test(Inspection and K- S probability paper), curve fitting module and limit stress calculation module,ets. Realize the automation of the test data processing function and interface display function.(3) Gear contact fatigue data obtained by experiment had been analysed, based on the characteristics of the contact fatigue life of gear, the life of each stress level had been assumed to be logarithmic normal distribution. The rationality of the distribution hypothesis had been examined by using labview data processing system, and the experimental data had been fitted by least square, obtained the P-S-N curve of gear material. When circulation base that N0 was 3×106、1×107�'� 5×107, the straight lines were generated respectively to calculate the fatigue limit stress value under different reliability,so that reference data of gear strength design of 35 CrNiMo could be provided.(4) This paper briefly introduced the finite element theory and contact problem, To lay the theory foundation. for the finite element analysis of gear contact problem. On the basis of the actual gear parameters, generated parametric modeling with the Pro/E software. Then analysed the contact stress distribution of the tooth face with finite element analysis software of ABAQUS, comparing the results of limit element analysis with Hertz formula calculation results to prove the accuracy of the finite element analysis results(5) Generated spherical shape defects of the different size in the same place(position of dividing circle) of teeth, and set up defects of the same size on the addendum, dedendum and dividing circle position based on the software of Pro/E, with the help of ABAQUS finite element analysis software to study the effect of defects on gear contact fatigue strength.