1、扭矩法

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。

The torque method is a method of tightening control in the elastic zone using the linear relationship between torque and preload. This method only controls a certain tightening torque during tightening, so it is a general and conventional tightening method because it is easy to operate. However, due to the fact that about 90% of the tightening torque acts on the consumption of thread friction and bearing surface friction, and only about 10% actually acts on the axial preload. The dispersion of the initial preload varies with the degree of control of factors such as friction during the tightening process. Therefore, this tightening method has a large dispersion, which is suitable for the fastening of a part, but not for the connection of important and critical parts.

2、轉角法

2. Corner method

轉角法就是在擰緊時將螺栓于螺母相對轉動一個角度,稱之為緊固轉角,把一個確定的緊固轉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。根據緊固轉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 rotation angle method is a method of controlling the initial preload by rotating the bolt relative to the nut by an angle, known as the tightening angle, using a determined tightening angle as an indicator. This tightening method can be used in both elastic and plastic regions. According to the relationship between tightening angle and preload, when the slope of the Q-F curve changes sharply, the dispersion of preload will also increase with the setting error of tightening angle. Therefore, when the rigidity of the connected parts and bolts is high, it is unfavorable for fastening in the elastic zone; When tightening the plastic zone, the dispersion of the initial preload mainly depends on the yield point of the bolt, while the impact of the angle error on it is not significant. Therefore, this tightening method has the advantage of maximizing the strength of the bolt (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,則需要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 can cause plastic deformation of the rod and threaded rod of the bolt when tightening in the plastic zone. Therefore, its applicability should be considered for occasions where the bolt has poor plasticity and the bolt is repeatedly used. In addition, when excessive preload may cause damage to the connected parts, it is necessary to specify the upper limit values of the yield point and tensile strength of the bolts.

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。

The torque slope method is a method of controlling the initial preload using the change in the torque slope value in the Q-F curve as an indicator. This tightening method usually takes the yield tightening axial force of the bolt as the target value for controlling the initial preload. This tightening method is generally used when the dispersion of the initial preload of the bolt is required to be small and the bolt strength can be utilized to the maximum extent. However, due to the fact that the control of the initial preload by this tightening method is basically the same as the rotation angle method in the plastic zone, it is necessary to strictly control the yield point of the bolt. Compared to the angle method in the plastic zone, this tightening method has fewer problems with the plasticity of bolts, such as repeated use, and has certain advantages. However, fastening tools are relatively complex and expensive.