STUDY ON 3D ELASTOPLASTIC CONTACT PROBLEM OF TURBOCHARGER COMPRESSOR

Abstract

A locomotive-type turbocharger compressor with 24 blades under combined centrifugal and interference-fit loading is used for the present analysis. The FE parametric quadratic programming (PQP) method which is developed based on the parametric variational principle (PVP) is used for the analysis of the stress distribution of 3-D frictional contact problem of impeller-shaft sleeve-shaft, and then, using the multi-level, multi-branch substructure technique of FE, makes it possible to precisely simulate complicated geometrical shapes of impeller and considerably enhances accuracy in numerical computation. The effects of fit tolerance and rotational speed, the displacement and the contact stress on the interference-fitting surfaces are discussed in detail. The contact stress of both the external and internal surface of shaft sleeve descends linearly with the increase of the rotational speed. At the same rotational speed, the contact stress of the external and internal surface of shaft sleeve decrease with the decrease of the amount of interference. And the contact stress of the internal surface decreases more quickly. To decrease the difficulty of the assembling process and make sure the safety of the working state, the amount of interference between the shaft sleeve and shaft by press-fitting should be controlled strictly to avoid the rapid increase of the contact stress. It is found there is obvious relationship between the mass distribution of impeller and normal relative displacement of contact points of impeller and shaft sleeve within the certain rotational speed. It is proposed that nonuniform initial interference value in the structural design would avoid relative displacement generated and ensure uniformity of the contact stress. The numerical results show the high accuracy and good convergence of the algorithm presented here. It provides an effective approach which achieves more reliable interference-fitted connections and more precise assembly accuracy with lower manufacturing cost in the structural design.