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The osteoporosis model of mouse tibia was established based on castration, and the effect of osteoporosis on the mechanical properties of tibia was investigated. The two-dimensional sections of mouse tibia were obtained by Micro-CT. The three-dimensional digital model of mouse tibia was obtained by reconstruction technology, and trabecular bone shape and density were analyzed. The effect of osteoporosis on the mechanical properties of tibia was explored by testing and finite element simulation. The results showed that osteoporosis could damage the trabecular structure and decrease the mechanical properties of tibia. Compared with healthy tibia, the maximum load, bending stiffness and elastic modulus of tibia decreased by 20%, 30% and 25%, respectively, and the simulation results were in good agreement with the experiment. This study provides an important basis for the clinical diagnosis and treatment of osteoporosis.

For the planet transmission device whose sun gear shaft is connected with tooth coupling,floating displacement of the sun gear directly determines tilt angle compensating of the tooth coupling,However,because of the sun gear ’s floating displacement multiply affects by comprehensive errors of planetary gear train parts,Its real value is difficult to calculate and measure accurately. This paper proposed a method,which is based on the dynamics analysis principle,to solve the sun gear’s floating displacement. It applies the means of equivalent meshing error to consider the manufacture and installation error of planetary gear train key components,a dynamic model of planetary gear train has been built,and according to the geometric relations between drum shaped spline and sun gear shaft,the tooth profile of drum gear has been modified to reduce the misalignment of the two connecting shafts. Finally,the experiment of certain planetary-gear transmission demonstrates that theoretical model is correct and possesses significant value of engineering applications.

In theoretically,all teeth of spline pair transmitted the same load. In practice,due to manufacturing and mounting errors,not all teeth transmit the same load and as a result,the overloading condition may occur. Based on finite element method,the distribution of contact pressure and load among teeth of involute spline pair with the conditions of angular misalignment,parallel misalignment and those two combined misalignment are investigated. The results have certain guiding significance and engineering application value in guiding involute spline pair manufacturing and assembly.