![<?echo $_SERVER['SERVER_NAME'];?>](/template/twentyseventeen/skin/images/header.jpg)
Excessive pre-tightening of the pre-tightening force can result in static damage to the threaded coupling parts, slippage of the coupling, separation or loosening of the fastener. Too small a preload will cause bolt fatigue damage and increase equipment quality and cost.
According to the theoretical analysis, in addition to the pre-tightening force Qp and the working tension F, the total pulling force of the bolt is also affected by factors such as the bolt stiffness Cp and the stiffness Cm of the coupled member. Therefore, we should start by analyzing the relationship between the force and deformation of the bolt connection and find out the total tension of the bolt.
It can be seen that the abscissa in the figure represents deformation and the ordinate represents force. The bolt tensile deformation is measured from the origin of the coordinate to the right; the compression deformation of the joint is measured from the origin of the coordinate to the left. It can be seen that when the joint is subjected to the working load F, the total tensile force of the bolt is Wp, and the corresponding total elongation is δL + ΔδF; the compressive force of the coupled member is equal to the residual preload force Fp, and the corresponding total compression is Δδ'F= Δf - ΔδF.
The bolt-receiving force deformation diagram is visible. The total tension Wp of the bolt is equal to the sum of the residual pre-tightening force Fp and the working tension F, ie: Wp=Fp+F(1) in order to ensure the tightness of the joint, so as to prevent the joint after the receiving. A gap is created between them, so that Fp ≥ 0. The recommended Fp is: Fp = (1.5 ~ 1.8) F for the connection with tight requirements; Fp = (0.2 ~ 0.6) F for the normal connection, when the working load is stable; Fp = when the working load is unstable (0.6 to 1.0) F.
From the geometric relationship, we can deduce the formula for calculating the preload: Qp=Fp+ΔF=Fp+FCFCL+CF(2) where CF is the stiffness of the gasket and CL is the stiffness of the bolt. The pre-tightening force of the bolt is controlled to ensure that the screw joint can overcome various static or dynamic external forces received by the joint. The tightening requirement of the design of the screw joint is to produce a certain pre-tightening force on the part. There are many tightening control methods to achieve this pre-tightening force, such as a simple wrench tightening manual method, a torque method, a torque angle method, a yield limit control method, and a bolt pre-elongation method. Among these methods, we focus on two methods of controlling the preload by tightening torque and controlling the preload by bolt elongation.
Best Window Locks,Casement Window Lock,Window Security Locks,Casement Window Handle Lock
SANHUI HARDWARE COMPANY LTD. , https://www.sanhui-1.com