How to effectively tighten the torsion shear bolt? There are three typical tightening methods, which are torque method, angle method and torque slope method. 1. Torque method

扭矩法就是利用扭矩與預緊力的線性關系在彈性區(qū)進行緊固控制的一種方法。該方法在擰緊時,只對一個確定的緊固扭矩進行控制,因此,因為該方法操作簡便,是一種一般常規(guī)的擰緊方法。但是,由于緊固扭矩的90%左右作用于螺紋摩擦和支承面摩擦的消耗,真正作用在軸向預緊力方面僅10%左右,初始預緊力的離散度是隨著擰緊過程中摩擦等因素的控制程度而變化的,因而該擰緊方法的離散度較大,適合一零件的緊固,不適合重要的、關鍵的零件的連接。

Torque method is a method of tightening control in elastic region by using the linear relationship between torque and preload. When tightening, this method only controls a certain tightening torque. Therefore, it is a general and conventional tightening method because it is easy to operate. However, about 90% of the tightening torque acts on the consumption of thread friction and bearing surface friction, and the actual effect is only about 10% of the axial pre tightening force. The dispersion of the initial pre tightening force changes with the control degree of friction and other factors in the tightening process. Therefore, this tightening method has a large dispersion, which is suitable for the fastening of a part, and is not suitable for the connection of important and key parts.

2、轉(zhuǎn)角法

2. Corner method

轉(zhuǎn)角法就是在擰緊時將螺栓于螺母相對轉(zhuǎn)動一個角度,稱之為緊固轉(zhuǎn)角,把一個確定的緊固轉(zhuǎn)角作為指標來對初始預緊力進行控制的一種方法。該擰緊方法可在彈性區(qū)和塑性區(qū)使用。根據(jù)緊固轉(zhuǎn)角和預緊力的關系可知,Q-F曲線斜率急劇變化時,隨著緊固轉(zhuǎn)角的設定誤差,預緊力的離散度也會變大。因此,在被連接件和螺栓的剛性較高的場合,對彈性區(qū)的緊固是不利的;對塑性區(qū)的緊固時,初始預緊力的離散度主要取決于螺栓的屈服點,而轉(zhuǎn)角誤差對其影響不大,故該緊固方法具有可限度地利用螺栓強度的優(yōu)點(即可獲得較高的預緊力)。

The angle method is to rotate the bolt to the nut by an angle, which is called tightening angle. A certain tightening angle is used as an index to control the initial pre tightening force. The tightening method can be used in elastic and plastic regions. According to the relationship between tightening angle and preload, when the slope of q-f curve changes sharply, the dispersion of preload will increase with the setting error of tightening angle. Therefore, when the rigidity of the connected parts and bolts is high, it is disadvantageous to the fastening in the elastic zone; when tightening in the plastic zone, the dispersion of the initial pre tightening force mainly depends on the yield point of the bolt, and the angular error has little effect on it. Therefore, the tightening method has the advantage of making full use of the bolt strength (i.e. obtaining a higher preload).

應該注意的是該擰緊方法在塑性區(qū)擰緊時會使螺栓的桿部以及螺紋桿部發(fā)生塑性變形,因此,對螺栓塑性差的以及螺栓反復使用的場合應考慮其適用性。另外,對預緊力過大,會造成被連接件受損的情況時,則必須對螺栓的屈服點及抗拉強度的上限值進行規(guī)定。

It should be noted that this tightening method will cause plastic deformation of the bolt rod and the threaded rod when tightening in the plastic zone. Therefore, the applicability of this method should be considered when the bolt has poor plasticity and is used repeatedly. In addition, the upper limit of yield point and tensile strength of bolts must be specified when the pre tightening force is too large, which will cause damage to the connected parts.

3、扭矩斜率法

3. Torque slope method

扭矩斜率法是以Q-F曲線中的扭矩斜率值的變化作為指標對初始預緊力進行控制的一種方法。該擰緊方法通常把螺栓的屈服緊固軸力作為控制初始預緊力的目標值。該擰緊方法一般在螺栓初始預緊力離散度要求較小并且可限度地利用螺栓強度的情況下使用。但是由于該擰緊方法對初始預緊力的控制與塑性區(qū)的轉(zhuǎn)角法基本相同,所以,需要對螺栓的屈服點進行嚴格的控制。該擰緊方法與塑性區(qū)的轉(zhuǎn)角法相比,螺栓的塑性即反復使用等方面出現(xiàn)的問題較少,有一定的優(yōu)勢,但是,緊固工具比較復雜,也比較昂貴。

Torque slope method is a method to control the initial preload with the change of torque slope value in q-f curve as an index. In this method, the yield tightening axial force of bolt is usually taken as the target value to control the initial preload. This tightening method is generally used when the discrete degree of bolt initial pre tightening force is small and the bolt strength can be used to a limited extent. However, because the control of the initial pre tightening force by this tightening method is basically the same as that of the rotation angle method in the plastic zone, the yield point of the bolt should be strictly controlled. Compared with the rotation angle method in plastic zone, this tightening method has less problems in the plasticity of bolts, i.e. repeated use, and has certain advantages. However, the tightening tools are more complex and expensive.