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

摘要： 高强度螺栓在发动机铝合金缸体应用时，应充分考虑避免铝制缸体内螺纹脱扣，粗、 细牙螺纹的选择，以及内螺纹加工方式等联接边界条件。选取 M10×1.5 粗牙和 M10×1.25 细牙的 10.9 级螺栓，基于标准 VDI 2230 分别计算得到有效最小啮合长度。通过拉伸试验， 验证两种螺栓在计算的有效最小长度啮合工况下，加载到最大抗拉强度时，两种螺纹均未发 生脱扣情况。同时对带有普通攻丝内螺纹和挤压成形内螺纹的铝件分别进行 50 次螺栓过屈服 拧紧测试，并对试验后两者内螺纹的状态进行了对比。结果表明，不论是粗牙螺纹还是细牙 螺纹，只要按照推荐的计算方法确定螺纹啮合长度，均可实现螺纹不脱扣；且挤压成形内螺 纹相对切削加工内螺纹具有更好的承载性能。试验结论为高强度螺栓与铝合金连接的边界条 件选定及正向设计提供了一定参考。

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