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The analysis of the resultant force of the bolt is known from the structure of the gearbox and the assembly of the drive brake unit. The bolt is only affected by the axial load and the tightening torque. Before the locomotive is not running, the bolt has been subjected to the preload force F0 and the tightening torque. According to the fourth strength theory, the preload force F0 needs to be multiplied by a factor of 1.3; thereafter, the bolt is also subjected to the axial temperature difference during the running of the locomotive. Load Ft (the locomotive is driven out from a station, the temperature difference load increases with the rise of the gearbox temperature, and finally reaches a stable value, which is approached to the next station, which decreases with the decrease of the gearbox temperature, the amplitude is large, the frequency is low) and The axial pulse (determined by the assembly structure) acts as a load Fw (small amplitude, high frequency). After analyzing the load history with the fatigue analysis software nSoft, it can be approximated that the load changes by the cycle, and the error does not exceed 10%. The combined force of the bolt is shown in Figure 1 and 2. K is the relative stiffness coefficient; Agy is the bolt root area. In the case of preload and pulsating load, the stress in the bolt is the fluctuating tensile cyclic stress, not the pulsating tensile cyclic stress, and the range of the stress cycle is changed; using the endurance limit to simplify the safety of the broken line check bolt Coefficient (see Figure 5).
Figure 5 Smooth specimen endurance limit simplified line diagram shown in Figure 5, the smooth limit of the smooth specimen is simplified as the ACB. Because 0 < r < 1, so only the CB segment is used to calculate the safety factor. After the working stress amplitude Ra and the average stress Rm at the dangerous point of the bolt are given, since Rmin = constant, the point I passing through the point I is 45b with the abscissa axis, and the line CB intersects the point F. The stress represented by point F is the endurance limit when the combined influence coefficient is not considered. The bolt safety factor can be defined as the ratio of the maximum working stress of the bolt to the end-of-life limit considering the combined influence coefficient or the stress amplitude of the bolt and the stress amplitude after considering the comprehensive influence coefficient under the same load stress. . According to this definition, we derive the following formula for the safety factor of work: the safety factor of the maximum working stress check of the bolt; na is the safety factor of the bolt stress amplitude; KR is the effective stress concentration factor of the thread; B is Surface processing coefficient; E is the size factor.
The working load is known from the structure of the gear 1 box and the assembly of the driving brake unit. The bolts at the joint between the transmission gear box and the motor are only subjected to the axial vibration load. The bolt is subjected to an axial working load due to lateral vibration acceleration during locomotive operation. The axial working load is; a is the maximum lateral dynamic load coefficient; w is the gearbox mass; g is the gravitational acceleration; Z is the number of bolts. This paper takes the dynamic load factor; (Note: cited from 5 internal combustion, electric locomotive steering frame static strength test method 6TBPT2368). Temperature difference load When the locomotive is running, the increase of oil temperature in the gearbox is related to factors such as motor power, gearbox transmission efficiency, locomotive running speed, oil viscosity, gear reversal and other factors. The situation is complicated. Based on the experimental data (Fig. 3) and considering the design speed of the blue arrow, a temperature rise series is assumed. The oil temperature is assumed to be related to the internal and external convection of the gearbox and the structure and wind speed. There are convective heat transfer, radiation heat transfer and air heat conduction between the bolt and the bolt hole. When the oil temperature is 90e, the bolt temperature field is shown in Figure 4. It can be seen from Fig. 4 that the bolt temperature field is basically a uniform temperature graph 3 time oil temperature curve; the gear is rotating forward; and the gear is reversed. Figure 4 bolt temperature field field. Taking 20e room temperature as the reference temperature, the bolt temperature rise series is. Because the expansion coefficient of aluminum alloy and steel is different, the thermal deformation is inconsistent, the temperature difference load of the bolt is the same; where: the lower corner mark L represents the bolt, and the F represents the connected part. C is the stiffness; t is the temperature rise; L is the assembly length A at room temperature is the expansion coefficient. Calculation of joint stiffness After tightening, the bolt is subjected to the pre-tightening force F0, and is also subjected to the working load Fw during operation. Both the bolt and the connected part are elastic bodies, and the force relationship of each part in the joint is a static problem. The total tension of the bolts is not equal, but equal to the stiffness of the bolts and joints. Calculated according to the formula.
The eye bolt is forged by warm quenching. Surface treatment of lifting ring Screw: CORRUD-DT, this surface treatment is at least 20 times better than ordinary galvanizing treatment in terms of anti-corrosion effect. External thread length ¨ H ¨, the bolt is fixed with other parts, and the bolt with the same quality grade must be selected for replacement.
Eye Bolt,Lifting Eye Bolt,Eye Screw,Stainless Steel Eyebolts
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