三次元有限要素法による傾斜ねじナットの弾塑性解析

西山修二　清水功史　右田博章^*　片岡光正^*
　　　　　　　　　　

　ボルト締結体は維持やメンテナンスに高いコストを必要とせず、また操作が簡単なために、機械構造物に広く使用されている。しかしながら、動的な荷重のために引き起こされるねじの弛みは、いまだに解決されていない。我々はゆるみ止め性能が期待される新しいタイプの傾斜ねじナットを開発した。本報では、傾斜ねじナットのゆるみ止めのメカニズムについて三次元有限要素法を適用して解析的に明らかにした。解析結果からＪＩＳ標準ナットより弛み止め性能が優れていることが明らかとなった。

　Bolted joints are widely used in mechanical structures since the disassembly for maintenance is easy without high cost. However, vibration induced loosing due to dynamic loading has been unsolved subject for a long time. We have developed a new type of nut named 'Screw Inclined nut (SIN)', which realizes anti-loosening performance without complicated tightening process and tool. In this study, we have investigated the mechanisms of bolted joint with SIN, and tightening behavor are analyzed by mean of three-dimensional finite element method. Results are compared with the experimental results for SIN. Good qualitative agreement is observed between analytical results and experiments with respect to tightening force, tightening torque and stress, We found some new aspects and superior points for bolted-joint with SIN than that ofstandard nuts. It is found that tightening torque of SIN is higher than that of standard. It is also found that the anti-loosening performance can be realized by the thread contact force at the slit region and angular facing on bearing surface. Moreover, it is concluded that SIN involves sufficient strength in practical use.