A key functional aspect of assembled camshafts is the joining strength between the shaft tube and the cam lobe, which is depended on the assembly or joining method. The assembly process by knurling joining and torque deformation of assembled camshaft were numerically studied and the key influencing factors on the press fit load and joining strength were analyzed. The experiments including to the press fit and torque strength of lobe/tube joining were carried out.The results show that the torque strength of the cam lobe/shaft joining can availably increase by matching cam and tube materials, choosing appropriate knurling form, enlarging magnitude of interference and extending knurling width. The numerical results agree well with the experiments and are significant in the design and manufacture of assembled camshaft.

The fracture surface of con-rod is difficult to be quantitatively described due to its indented macro morphology. Thus, the range of fracture surface defect dimension has no uniform standard. In order to solve this question, 3D software about the digital fracture surface reconstruction was developed by combining the fracture splitting technology of con-rod with reverse engineering, which realized the reproduction of its morphology and completed the real area calculation of the surface. The results show that the fracture surface area processed by fracture splitting is 13.1% larger than that of the plane processed by machining. It represents that the defect dimension range of fracture surface is improved compared to empirical value without reducing the bearing capacity and usability.

Fracture line offset is the main defect in connecting rod fracture splitting processing, which seriously affects the using performance of connecting rod. In order to control this defect more effectively, the basic reason why this defect occurs was researched according to the theory of fracture mechanics, and the method of numerical simulation was used in this paper. The results show that when the applied load is nonparallel to the axis of a connecting rod, the first principle stress on the theoretical fracture surface is not perpendicular to the theoretical fracture line and the stress distribution is asymmetric on both sides of notches, which leads the type of fracture to turn into mixed mode I-II from mode I. As a result, the defect of fracture line offset occurs. Furthermore, the main factors leading to skew load were analyzed in actual production, and some effective measures were proposed to avoid the occurrence of this defect. This is significant in controlling the quality of connecting rod fracture splitting.