An approach to local finite element mesh refinement is studied for three dimensional elastic contact problems.The study shows that because of different acting loads the boundary conditions of the refinement model in contact problems are different in calculation at flexible matrices and contact stresses.On the basis of the approach

an effective method is provided for the calculation of the contact stresses of spur and helical gears during the whole engagement period.According to the position of contact lines in the action plane

the present method establishes the FE models of gears by a 3 D automatic mesh generation program.The load share ratios of gears and load distributions along the contact lines during the whole engagement period are then simultanuously calculated by using the coordinate systems of gear profile and the corresponding matrices of coordinate transformation.Furthermore

the local FE mesh refinement models of gears on a specific contact line are established and the detailed contact stress distributions of the contact line are evaluated with the use of finite element mathematical programming technique.In this case

the calculations of contact stresses on different contact lines of gears during the whole engagement period can be conveniently carried out.The contact stresses on different contact lines of a pair of aeronautical helical gears acted by dynamic and static loads of the gear system are calculated.The calculated results show

the present method and the corresponding microcomputer programs are fast and reliable in calculation as compared with those by Aeronautical Standard of China HB/Z84

2 84.