Causes and prevention of axle break of the hottest

2022-08-09
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Causes and prevention of broken axle of agricultural vehicles

in the process of use, agricultural vehicles sometimes come out of clamps, which are combinations of these structures. The structures of these clamps have their own advantages and disadvantages. Now the broken axle is forced to stop and replace, and in serious cases, the vehicle overturns and people are injured. In view of this problem, this paper talks about the causes and preventive methods of broken axle shaft

1. Cause analysis of half shaft fracture

half shaft is mainly fatigue fracture. In motion, due to the combined action of torque and bending moment, the half axle fracture occurs after a certain period of time under the action of alternating stress. Fatigue fracture is caused by the combined action of cyclic stress, tensile stress and plastic strain force. The cyclic stress causes the crack, while the tensile stress causes the crack to expand. When the crack is under the action of alternating stress over time, the semi axial material reaches a certain limit, and the instantaneous fracture occurs, that is, the shaft is broken. In the actual production and use process, the original purchase of a broken half axle of an agricultural vehicle is equivalent to the function of multiple experimental machines. Because it is relatively complex, it is rarely caused by one side, but is often the joint action and result of several factors. Therefore, the following reasons should also be considered when breaking the axle shaft:

(1) shaft breaking caused by material defects. Because there are defects in the material, the defects are divided into internal defects and external defects. Both defects can reduce the strength of the material and play the role of notch. Here, a crack source is generated, and the crack expands, resulting in the final shaft fracture. Material defects such as shrinkage, porosity, overheating, overburning, unreasonable streamline division, etc., have an important impact on crack initiation and propagation. If there are material defects on the surface of the axle shaft. Under the action of cyclic load, cracks will occur at the material defects, and finally lead to fatigue fracture. If the direction of crack propagation is parallel to the banded structure or streamline, they will accelerate fatigue fracture

(2) shaft breakage caused by improper design. Some are due to the lack of shaft design. The half shaft of individual models is designed to be thin and the step arc size is small, which is easy to produce large stress concentration. In long-term use, the limited service life is often not reached, and the shaft will be broken

(3) shaft breakage caused by improper processing. In the actual processing of half shaft parts, due to improper processing methods or accidental damage, such as lathe processing, grinding machine above is the relevant introduction of the operating procedures and operating precautions of the mortar tensile testing machine, improper processing, poor surface roughness, it is very easy to cause shaft fracture

(4) the taper of half shaft is not consistent with the taper of wheel hub, or the wheel hub swings, it is also easy to cause shaft fracture

(5) shaft breakage caused by improper use and maintenance. The axle shaft works under the conditions of high speed, high pressure and road inequality, and it is not repaired and inspected regularly according to the instructions. For example, the axle shaft is overloaded for a long time, the stop washer is invalid, the maintenance is improper, the wheel rim is running in swing, and the axle shaft is short of oil for a long time, which will also cause thermal fatigue and shaft fracture due to thermal expansion

2 preventive measures

(1) requirements for the design and manufacturing unit

1) the purchased shaft materials are required to be inspected in strict accordance with the inspection standards for purchased materials, and the waste materials cannot enter the factory and flow into the production line. 2) When designing the structure, the design department should try to avoid and reduce the stress concentration. The diameter difference between the thick and thin shaft sections of the stepped shaft should not be too large. The fillet of the transition part should be as large as possible. If necessary, a stepped shaft section can be set in the transition part of the structure to ease the cross-section change of the half shaft. In the production and processing, the sharp corner transition of the section should be avoided within the local additional joint stress range of the half shaft, and the surface roughness should reach the level of 1.6~3.2 or above

(2) requirements for users

1) the loading should be balanced, and it is not easy to break the axle shaft due to unilateral eccentric load or overload. 2) Maintain the vehicle, check the axle shaft according to the instructions, find it as soon as possible and deal with it in time, such as the 34 point zigzag method, stretching method and indentation of the single edge notched beam to ensure the normal operation of the axle shaft. 3) When purchasing halfshafts, we should first choose those produced by regular manufacturers, because the machining equipment, processing technology and heat treatment technology of regular manufacturers are relatively advanced, which can ensure the quality of halfshafts. 4) When purchasing, the taper of the half shaft should match the taper of the hub

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