Analysis of Factors Affecting Installation Quality of Interference Fitted High Lock Bolts

Analysis of Factors Affecting the Installation Quality of Interference and High-locking Bolts by Zhang Yanzhao, Zhang Yanzhao, Cao Zeng, Qiu Jianping, Zheng Pengyu (School of Mechanical and Electrical Engineering, Northwestern Polytechnical University, Xi'an 710072, China). Stress wave mounting is a new method of interference fit fastener mounting that makes it easier to install large interference fasteners. In this paper, the installation of the interference matching high lock bolt in the manufacture of a certain type of aircraft is adopted, and 63. When the switch is closed, the power supply charges the capacitor bank, and then the electronic discharge switch is closed, at this moment (at the microsecond level), A short duration current pulse reaches the primary coil, creating a strong magnetic field in the primary coil, inducing current in the secondary coil, and establishing a corresponding strong magnetic field in the secondary coil. The repulsive force of an instantaneously excited electromagnetic field will generate a stress wave in the regulator, and the stress wave will propagate forward to reach the fastener, causing axial and radial deformation of the fastener rod, causing the fastener rod portion to radially shrink. ''Thinning', under the impact of stress waves, the fasteners overcome the interference fit of the installation resistance - including the interference contact resistance and frictional resistance to complete the installation. 8. Due to the shrinkage of the fastener rods "thinning" The installation resistance is reduced during the installation process, and thus, a fastener with a large interference amount can be installed.

Analysis of the stress wave installation process can be seen that the factors affecting the installation quality are high lock bolts, interference and sandwich materials. For bolts, the geometric size and surface quality have a great influence on the installation quality. In this paper, combined with the actual installation of the product, the main reason is that even in the case of interference of only 0.43%, the interference of the 2024 aluminum alloy with the stress wave installation will still extrude the material, and for the same interlayer thickness, the same bolt diameter, the interference amount is 0.8% of the 7075 aluminum alloy will not extrude the material after installation, as shown. The test results for 7050 were as shown and the material was not extruded. In view of this situation, we compared the mechanical properties of each material. As shown in Table 1, we found that 2024 is less than 7075 in hardness, yield strength and tensile strength, which is inferior to the strength of titanium alloy used in high lock bolts. Too big. At present, the materials used in aircraft manufacturing mainly include aluminum alloys and composite materials. The main grades of the aluminum alloys used are 7075, 7050 and 2024. In the actual production process, the aircraft structure is generally fixed on the assembly frame, and the openness and maneuverability are limited, so generally only the mobile stress wave installation equipment can be used. Conventional bolting is generally done with a single gun, and the structure is fixed through the frame. in. Surface lubrication conditions have an impact on installation quality and mounting force during fastener installation. For ease of comparison, the effects of different lubricants on mounting force were investigated.

The experiment conducted a comparative test on commonly used lubricants such as molybdenum disulfide, 201 ointment and lard. For comparison, the experiment uses the same pin, hole diameter, interference amount and the same mounting force. Different lubricants are used to measure the depth at which the pin is driven, and the difference between different lubricants is analyzed. The results are shown in Table 4. Table 4 Three kinds of lubricant pin penetration depth statistics Interference amount / % voltage / V lubricant extension amount / mm Mosulfurized molybdenum lard According to Table 4, the fastener rod diameter, interlayer thickness, Under the condition that the interference amount and the installation voltage are the same, the molybdenum disulfide has the best lubricating effect, and the protruding amount of the pin can reach 22.01 mm, followed by the 201 oil protruding amount is 18.51 mm, and the lard is only 16.27 mm. Bolts with better lubrication require only a small installation voltage for installation. The smaller mounting voltage results in less mounting force, and the smaller mounting force also reduces structural distortion during installation.

3 Conclusion High-lock bolt thread and polished rod rounding have a great influence on the installation quality. The high-locking bolt with small rounded corners of thread and polished rod can easily damage the hole wall structure during installation and affect the installation quality.

The lubrication quality of different bolt surfaces is different, and the bolts with good lubrication quality on the surface of the bolts need less installation force. Smaller mounting forces can reduce the deformation of the structure during installation.

For the installation of titanium alloy high-lock bolts, sandwich materials such as 2024 aluminum alloy which have a large difference in strength from titanium alloys are not suitable for interference fit with large interference quantities.

The use of double guns on both sides of the same loading and installation of high-lock bolts can effectively solve the local deformation problem of the structure, and can realize the stress wave installation of the fastener with large rod diameter and large interference amount, and the installation force is small.

Edited by China Academy of Aeronautical Science and Technology. Aircraft Structure Anti-Fatigue-Fracture Strengthening Process Manual. Beijing: Aviation Industry Press, 1993 Deng Jianghua, Li Chunfeng and so on. Electromagnetic riveting sample quality analysis. Plastic Engineering Gao Bin, Cao Enhanced. Interference with the installation of fasteners. Aviation Manufacturing Technology, Cao Qiang, Liu Hong. Electromagnetic riveting technology. Journal of Plastic Engineering, 2007, 1): Tao Hua, Yan Gong, Sheng Xi. The stress wave mounts an interference fit fastener. Northwestern Polytechnical University of Aeronautics. Low-voltage electromagnetic riveting equipment manual Z.2000,12

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