Screw assembly and anti-loosening technology

Screw device and anti-loosening technology

Author: admin Origin: Date of this website: 2017-7-5 9:24:41 Popularity:Label:

Craft exchange screw device and anti-loosening technology bookmark0 Aerospace Science and Technology Group 3 Institute 3103 Zhao Yunyi and Li Jinping occupy a large proportion of the process. The process of the device always presents the fruit tightening torque during the New Year.fastenerThe question of the connection parts being effective is, in order to improve the consistency and reliability of screw connections, the actual tightening torque value of screws of different specifications was first calculated and summarized. Secondly, the vibration experiment was used to verify whether the screw tightening torque value could be accurate and justified. Initially, the screw tightening torque selection criteria were summarized so that the process plan staff could choose based on different utilization conditions.

The key to the safety of screw connection is to maintain sufficient surplus preload. When the inertial guide is vibrating, the force of the screw is large enough to eliminate preload, the screw will be damaged by loosening or breaking. In order to prevent the screw connection from taking effect, it is rarely used to prevent the product from repairing and disassembly properties. Rib fastening glue is rarely used to prevent loosening and elastic pads from being loosened. In addition, the rib fastening glue is prevented from loosening, and the adhesive is highly effective and the disassembly moment increases exponentially. The elastic pad is prevented from loosening. The elastic pad is mainly used to improve the fighting form in the support, which allows fluctuations in the number of friction in the support, and has a certain effect on the anti-loosening. The spring washer coaxes its elasticity to cause the back of the ribbed shaft to tighten the back of the ribbed shaft and prevent friction from being loosened, but is usually used for untightened ribbed joints.

2. The engineering calculation method for rib fastening torque is not in the project plan. The tightening torque of ribbon connecting parts is usually calculated according to the type. In addition, the tightening torque coefficient K is the smallest rib, the lifting angle, the friction angle of rib equivalent, the friction coefficient of rib equivalent, and the friction coefficient of rib head is related to the friction coefficient supported by the attached part. No, according to the experimental method designated by GB715.15 for specific working conditions, when the outer and inner part of the connected part are oxidized and smooth, take 0.24. F, the back force of the shaft, that is, the positive preload force of the planned preload force, K tightening torque coefficient; d, the nominal diameter of rib, unit mm; for carbon steel screws, the preload force is: For alloy steel screws, the preload force is: As rib nominal stress intercepting, d2 outer rib outer diameter; d3 rib diameter is calculated "3 H is the original 3-angle height of the rib; di outer rib diameter.

3 The engineering calculation values ​​of rib fastening torque are 9.8, 10.9, 12.9. The numbers before the decimal represent 1\/100 of the tensile weakness of the data. The numbers after the decimal represent the bending limit of the data (approximately, .2). Take 10 times the tensile weakness of the data. For example, the tensile weakness of the screw with a grade of 4.8 is 4x100=400MPa. The bending limit is the tensile weakness of the common functional grade of the screw. See Table 1. The tightening torque of common rib fasteners is shown in Table 2. Sporadic adjustment technology.

Table 1 Tensile weakness and bending limit of common functional grades of screws 2 Common rib fastening 1 Niu Tightening torque engineering calculation results Screw specification National standard Aviation industry standard Functional grade\/data Trademark Rib specificationboltTightening torque\/Nm bolt tightening torque\/Nm 4 Rib fastener selection method. Screw fasteners are relatively loose. The use of rib fasteners to prevent loosening. In addition, epoxy adhesive is relatively large, and it is usually not disassembled after the screw is tightened outside. The epoxy adhesive is usually two-component, and the operation is complicated. Anaerobic adhesive has excellent vibration resistance, adhesion and sealing, and has weak anti-loosening function. Anaerobic adhesive is a single-component adhesive. It is liquid outside the atmosphere. After the atmosphere is suppressed, polymerization reaction occurs and repeated disassembly of rib fasteners is used. This anaerobic adhesive is relatively rare.

Anaerobic glue is usually a series of glues, divided into different trademarks according to the bonding weakness. Whether to select glue liquids with different functions based on different needs such as rib fastening and sealing. Loctite 200 series is rib locking sealant, which is widely used. Its functions are shown in Table 3. Table 3 Loctite 200 series product functions Terry M12 weak low weakness external weakness ultra high weakness ultra high weakness ultra high weakness external weakness low viscosity serial number Rib fastening glue loosening torque increase status 1 Loctite 22213 Percent 2 Loctite 24325 Percent 3 Loctite 26240 Percentage Table 5 Vibration Experiment Prerequisites The purpose frequency of the experimental target\/Hz power spectral density value\/g2Hz-1 total mean square value\/g time\/minX, Y back 20 After using Lotte lock glue, the rib release torque will increase. The loosening torque will increase after using glue is shown in Table 4. Table 4 Use different rib fastener rib release torque to increase the experimental conditions 5.1 Experimental examination of screw fastener tightening torque 5.1 Experimental premises In order to verify the accuracy of the selection criteria for screw tightening torque, a screw fastener vibration experiment was held. The vibration experiment was affirmed, and the experimental premise was shown in Table 5. The purpose of the X back and Z back vibration experiment communicated on the purpose of the screw stress mark, so only the purpose of the X back and the Y back are vibrating.

5.2 The experimental preparation data is 2A12T4. At the same time, in order to ensure the device weakness of the screws, the ribs above M4 are inlaid with wire screw sleeves. The first choice of rib fasteners for experiments is HB and GB screws. In addition, the functional grade of GB screws is 4.8, 5.8. The selection data of HB screws is ML25 sill screws). Each specification has 20 screws, and the rib fastener has no anti-loosening steps, elastic pads are anti-loosening, rib fastening glue is anti-loosening, elastic pads and glue are anti-loosening vibration experiments.

5.3 The experimental process will reinforce the rib fasteners of different specifications according to different experimental premises. After the glue is solidified, the paint is marked in it, and then the vibration experiment is held according to the vibration experiment. After the vibration experiment, check whether the rib marking paint can have signs of damage. At the same time, use a torque screwdriver to approximate the torque wrench to check whether the rib fasteners can appear loose.

The vibration test parts outside the vibration experiment do not reduce the vibration pace, so the vibration experiment premise is even more despicable. Two controls and one monitoring are arranged on the vibration tooling. As shown.

5.4 Experimental judgment After vibration experiment, the X back vibration experiment was released at a maximum ratio of 0.999 and the Y back vibration experiment was released at a maximum ratio of 2.26. It was explained that in the process of vibration experiment, the force experienced by some screws was largely subject to the experimental premise. After the vibration experiment, the mark paint was completely intact. At the same time, the torque screwdriver was used to review the screwdriver according to the defined torque value for no screws. It was confirmed that the tightening torque value of the rib fastener designated in this article was in compliance with the request.

According to years of consumption history, the selection criteria for screw fastener tightening torque is high: the tightening torque value of screw fastener should not exceed the engineering calculation value in Table 2, otherwise, the screw tightening torque will be cut, causing the rib teeth to be cut and tripped, which may cause the screw fastener to be broken.

The tight parts with high weakness are connected, and the screw fasteners with high quality grades are selected. At the same time, the high-weak Lotech locking sealant is selected to prevent loosening, but the product is not easy to disassemble.

- In order to meet the product's maintenance requirements, the screw fastener with a rib nominal diameter of lt; 2.5 is used to prevent loosening of the screw fastener with a rib nominal diameter of lt; 2.5 is used to prevent loosening of the screw fastener with a rib nominal diameter of 2.5.

For tightened external data such as plastic data, it is necessary to lower the tightening torque value of the screw fastener, otherwise the plastic parts will be deformed as the tightening torque is large. The screw selection function grade 4.8 screws are approximately 1\/2 of the engineering calculation value calculated in Table 2. If the tightening torque value of the screw fastener is required, the maximum torque value of the screw fastener that does not crush the plastic parts at the same time should not exceed the maximum torque value given in Table 2. At the same time, in order to ensure that the ribs are not loose, Loctite locking sealant 243 and the elastic pad are used to prevent loosening.

If the screw reinforcement process is used to reinforce, different rib fastening glue will be used to increase the screw loosening torque by different slurry, so the screw tightening torque is high and appropriate to lower the screw tightening torque.

The anti-loosening method of using the elastic cushion is usually used for untightened ribbed pair connections. Therefore, the tightening torque of the elastic cushion is initiated, and the value of the table is shown in 2.

7 Conclusion To prevent the screw from taking effect outside the process of the device, to improve the consistency and reliability of the screw connection, the tightening torque of the screw must be affirmed.

The screw tightening torque value supplied in this article is the engineering calculation value and is derived from the summary of the consumption real-life experience. In addition to consumption, the tightening torque of the ribs needs to be determined in detail based on the different working conditions used by the screws.

6 Screw fastener tightening torque selection criteria