Load History Analysis Of Root Stress And Calculation Of Friction Coefficient Between Teeth

With the development of high precision, high strength, high reliability, lownoise, long life and so on, the impact of friction to the gear transmissioncharacteristic and the bearing capacity is becoming more and more concern. Theresearch related to tooth surface friction has significant meaning to explore themechanism of gear fatigue, wear and crack failure. Taking the spur gear as theresearch object, the influence of friction on the root stress was analyzed in this paperand surface friction coefficient was calculated. The main contents of this paperinclude:(1) Gear tooth profile calculation and finite element modeling. Combined thegear meshing theory with gear generating machining method, the tooth profile curveequations were deduced. The geometry coordinates of key geometry points wereextracted by programming and then it was imported into finite element softwareusing parametric programming. The precision geometry model and finite elementmodel were established via union modeling.(2) Load history analysis of root stress including friction and multi-toothmeshing. The load distribution between teeth was obtained by analyzing the gearmesh stiffness, which provide load curve for the calculation of tooth root stress loadhistory. The tooth root stress along the meshing position changing and the wholetooth surface stress distribution of tooth surface contact stress and deformation in ameshing period was achieved with uniformly distributed load. Taking the drivinggear as a research object and considering the friction between tooth and loaddistribution in multi-tooth meshing, load history of tooth root bending stress wasresearched. The region of engagement was divided into upper and lower regions byreference circle. The calculation equations of tooth root bending stress in differentmeshing areas were derived.(3) Wireless dynamic test for root stress. The tooth root stress dynamic testsystem was developed depend on the LabVIEW integrated platform, which was usedto measure root strain and rotation speed torque. The results of the test were smoothprocessing by using the time domain average method. The main interference s in thetest process were effectively eliminated. The root strain curve reflect the alternatingphenomenon of single and double tooth engagement, meshing impact and theinfluences from adjacent meshing teeth. The deviation of the maximum root stress between test and calculation is smaller.(4) The reverse calculation of tooth surface friction factor. By analyzing theinfluence of friction on the tooth root bending stress, the positive and i nverseproblem models for the reverse calculation of tooth surface friction factor wereestablished. Using Latin hypercube method to design the experiments, thecalculation sample points were established. The stress value of each sample pointwas calculated by the FEM. The agent models of gear and objective function wereestablished by the sample points and the corresponding root bending stress of it. Thefriction factor of meshing position was calculated via the genetic algorithm. Thechange rule of friction factor in a meshing period can be obtained through thereverse calculation of friction factor in different meshing positions.