Research Of Gear Bending Fatigue Strength And Gear Fatigue Crack Propagation

This paper studied the big modulus gear rack that used for the Three Gorges Dam ship lift,which lack of relevant standards and data.In order to break the limitations of big modulus gear and rack design standards,In this paper mainly study on the Three Gorges ship lift modulus 62.7mm big modulus rack material 35 CrNiMo bending fatigue strength and crack propagation,included the following.First of all, this paper carried out the experimental study of gear bending fatigue strength.Single tooth loading method and group test method test program, and the resulting data were fitted processing.Finally get the gear bending fatigue stress limit values, as well as the relationship between stress and the cycle life that is the P-S-N curve.Secondly based on the fracture mechanics theory,focuses on the remaining life after small cracks appear.With the help of Franc3 D and finite element software,get the stress intensity factor and other relevant parameters,forecast next crack in accordance with the parameters obtained by the simulation.And the next generation of crack extension, loop iterations until it breaks.Thirdly make a macroscopic observation of bending fating fracture analysis,Then analyzed the samples with scanning electron microscope.Focuses on its crack source, in order to find the cause of the fracture type gear reasons.Provide the basis prevention for generating the crack.Finally, this paper based on fractal theory of crack propagation path dimension calculation to find the relationship between the crack propagation path between dimension.Firstly, use camera to capture crack image, and then using Matlab software to process image, the image were processed RGB format for binary image.Use box-counting method to calculate the dimension,then get the correspond fractal dimension.