In order to enhance the performance and design efficiency of military engine system

dynamic features of combined structure of military engine main parts are researched. Sub-structure mode integration method based on test results was adopted. 3-D solid models of four elements

block

crankshaft

cylinder-head and crankcase

were built separately and then assembled into combined structure model. Virtual materials were introduced to simulate the stiffness and damping features of the joint surfaces between the four elements

for those features are difficult to be obtained either theoretically or experimentally. Properties of the virtual materials were gradually modified to make FEM modes results of combined structure consistent with the experimental ones. This proves the rationality of the virtual material method and the feasibility of dynamic features for combined structure

paving the way for further research of the engine′s dynamic simulation.