关键词: 高强度螺栓；发动机铝合金缸体；螺纹啮合长度；拧紧试验；内螺纹

Abstract: In the connection application of high strength bolts with aluminum alloy cylinder block, the connection boundary characters such as avoiding the screw loose of aluminum cylinder block, the choice of coarse or fine thread, and the manufacturing method of internal thread, need be fully considered. Based on the M10×1.5 coarse thread and M10×1.25 fine thread bolts with strength grade 10.9, minimum effective engagement lengths are calculated for both applications, using method of VDI 2230. By using tensile test, it is verified that both bolts have no screw loose, when being loaded the maximum tensile strength, under the condition of minimum effective engagement length. At the same time, 50 times of over-yield tightening tests are carried out on aluminum alloy parts with tapping internal threads and extrusion internal threads respectively, and the state of both screw threads is compared after testing. Results show that no screw loose can be realized for both coarse and fine thread, if the minimum engagement length follows the recommended calculation method. Moreover, extrusion internal threads have better performance than tapping internal threads.The testing results provide a reference for boundary condition selection and top down design of connection for high-strength bolt and aluminum alloy.

Key words: High strength bolt; Aluminum alloy cylinder blocks; Engagement length of thread; Tightening test; Internal thread