螺距对引信内腔封口螺纹连接强度的影响

Influence of Screw Pitch to Joint Strength of Fuze Inner Cavity Sealing Thread

针对引信内腔封口连接螺纹强度设计特别是螺距优选问题,对机械设计理论中螺纹应力的计算公式进行推导,提出了考虑到引信连接螺纹端头倒角、允许崩落长度和允许止量规适当进入等情形时引信内腔封口螺纹连接强度的计算方法。该方法在分析螺纹牙所受应力时仅需考虑与螺纹直径、螺距和连接长度相关的应力系数,使得计算过程简洁方便,计算结果准确可靠。结果表明:螺距对螺纹强度影响较为敏感,在不考虑螺纹制造误差和连接长度一定且有限的情况下,尽可能选用较小螺距有助于提高强度。螺纹强度校核时仅需考虑弯曲强度和剪切强度而不必校核挤压强度。就螺纹牙所受应力而言,螺纹牙所受剪切应力接近弯曲应力的一半。由于传统引信螺纹零件强度校核时未考虑弯曲强度,也未考虑螺纹牙受力不均、引信通用制造规范允许有螺纹牙崩落和止量规适当旋入等情形,致使螺纹连接强度计算结果过于冒进。

In the view of the strength design and especially pitch optimization of fuze inner cavity sealing connection thread,the stress calculation formulas of thread that appeared in the mechanical design theory was derived.Considered the end chamfering,allowed caving length and check gauge appropriate to enter,a new computing method was proposed.The stress counting process could much convenient and the more reliable results would achieved than before by using this method.Results showed that the strength of thread are greatly affected by pitch,when screw manufacturing error was ignored and connect length was limited,it is helpful to increase the thread strength by choosing little pitch as far as possible.It is unnecessary to check compression strength when strength checking,just bending strength and shear strength should be considered,it was found that the shear strength is close to half of the bending strength for crew tooth.Due to the bending strength,uneven loading factor of screw tooth,allowed caving length and check gauge appropriate to enter that stated in the general manufacturing specifications for fuze was not considered,the calculation results was too aggressive.