U-bolt is one of the widely used parts in automobile suspension system. Its main function is to fix the leaf spring on the shaft or balance shaft. In order to realize the combination between the leaf springs and prevent the longitudinal and lateral movement of the leaf springs, it provides a guarantee for the leaf springs to obtain an effective pre-tightening force. Therefore, this part plays an important role in the suspension assembly.
After the vehicle completes the assembly of the cab components and other components, the torque of the U-bolt will be attenuated to a certain extent, and after the vehicle is tested on the road, the torque will be further attenuated, so the dynamic and static torque of the front and rear U-bolts Quality control is particularly important.
People who often come into contact with U-shaped bolts may know this. High-strength bolts are mainly used in some outdoor projects, such as wind power generation or active machinery, with relatively high tensile strength. Ordinary bolts can be used for some small machines, such as turbines, and it depends mainly on the application environment and operation mode.
1. From the perspective of raw materials
High-strength bolts are made of high-strength materials. The screws, nuts and washers of high-strength bolts are made of high-strength steel. Commonly used are 45 steel, 40 boron steel and 20 manganese titanium boron steel. Ordinary bolts are usually made of Q235 steel. .
2. From the perspective of intensity level
High-strength bolts are more and more widely used. Two strength levels are usually used, 8.8s and 10.9s, most of which are 10.9. The strength level of ordinary bolts is lower, usually 4.4, 4.8, 5.6 and 8.8 level.
3. From the perspective of force characteristics
High-strength bolts apply pretension and transfer external force through friction. Ordinary bolt connections rely on bolt shear resistance and hole wall pressure to transfer shear force. The pre-tightening force generated when the nut is tightened is very small, and its effect can be ignored. High-strength bolts not only have high material strength, but also have a wide range of applications on bolts. The pre-tightening force produces squeezing force between the connecting parts, so there will be great friction in the direction perpendicular to the screw direction. , And the pretension, anti-slip coefficient and steel type directly affect the bearing capacity of high-strength bolts.
4. From the perspective of use
High-strength bolts are usually used for the bolt connection of the main components of the building structure. Ordinary bolts can be reused, but high-strength bolts cannot be reused. High-strength bolts are usually used for long-term connection. High-strength bolts are pre-stressed bolts. The friction type uses a torque wrench to apply the specified prestress. The pressure-bearing type is screwed off the plum head. The ordinary bolts have poor shear resistance and can be used in secondary structural parts. Ordinary bolts only need to be tightened.
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