Reasons and Prevention of Axle Break of Agricultural Vehicles
In the process of use, agricultural vehicles sometimes break half axle phenomenon, forced to stop and replace, serious vehicles turning injuries. To address this issue, talk about the reasons and prevention methods of broken axles.
First, the analysis of the causes of semi-shaft fracture
Axle shafts are mainly fatigue fractures. In motion, due to the combined effect of the torsion moment and the bending moment, a half-axis fracture occurs after a certain period of time under the action of the alternating stress. Fatigue fracture is caused by three kinds of interactions: cyclic stress, tensile stress and plastic strain force. The cyclic stress causes cracks, and the tensile stress causes cracks to expand. When the cracks are subjected to alternating stress over time, the material of the half shaft reaches a certain limit, and then the instantaneous fracture is the broken shaft. In actual production and use, the reasons for the breakdown of axles of agricultural vehicles are relatively complex, seldom due to unilateral effects, and are often the result of several factors working together. Therefore, the reasons for the following aspects are also taken into account when the half shaft is broken:
1, broken shaft caused by material defects. Due to defects in the material, the defect is divided into two kinds, internal defects and external defects. Both defects can reduce the strength of the material and act as a notch, where the crack source is generated and the crack propagates, resulting in the final broken shaft. Material defects such as shrinkage, loosening, overheating, overheating, and unreasonable flow line divisions all have an important influence on the initiation and propagation of cracks. If there is a material defect on the surface of the semi-axis, cracks will occur at the material defect under the cyclic load, which will eventually lead to fatigue fracture. If the direction of crack propagation is parallel to the banded structure or streamline, they will accelerate the fatigue fracture.
2. Broken shaft caused by improper design. Some of them are due to lack of design. The smaller semi-axle design on individual models is smaller in the size of the stepped arc, which tends to cause greater stress concentration. In long-term use, it often fails to reach the service life limit. .
3, broken shaft caused by improper processing. In actual machining of semi-shaft parts, due to improper machining methods or accidental damage, such as lathe machining, grinding machine machining, etc., and poor surface roughness, it is easy to cause broken shafts.
4, the semi-axis taper and hub taper does not match or wheel swing, etc., but also easily lead to broken shaft.
5, broken shaft caused by improper use and maintenance. The axles work under conditions of high speed and high pressure and road inequality. They have not been regularly repaired and inspected in accordance with the instruction manual. If the axle is overloaded for a long time, the stop washer fails, and the maintenance is improper, the rim runs in swinging motion. Oil, due to thermal expansion can also cause thermal fatigue off the shaft.
Second, preventive measures
1, the design and manufacturing unit requirements. Outsourced shaft materials are required to be inspected strictly in accordance with the inspection standards for purchased materials, and wastes cannot be imported into the production line. When designing the structure, the design department should avoid and reduce the stress concentration as much as possible. The diameter of the shaft section of the stepped shaft should not be too different. The fillet of the transition section should be as large as possible. If necessary, the excess section structure can be used. A stepped shaft section is provided so as to ease the change of section of the semi-axle. In production and processing, in the range of the local additional stress of the half shaft, the sharp corner transition of the cross section should be avoided, and the roughness of the surface should be increased beyond the level of 1.6-3.2.
2, the user's request. The load must be balanced. Do not unilaterally load or overload. It is also easy to produce broken half shafts. Maintain the vehicle well, check the axles according to the instructions in the instruction manual, and find out and deal with it in time to ensure the normal operation of the axles. When purchasing the axles, we must first select the regular manufacturers, because the regular manufacturers and processing equipment, processing technology, heat treatment process is more advanced, to ensure the quality of the axle. When purchased, the taper of the axle should match the taper of the hub.
First, the analysis of the causes of semi-shaft fracture
Axle shafts are mainly fatigue fractures. In motion, due to the combined effect of the torsion moment and the bending moment, a half-axis fracture occurs after a certain period of time under the action of the alternating stress. Fatigue fracture is caused by three kinds of interactions: cyclic stress, tensile stress and plastic strain force. The cyclic stress causes cracks, and the tensile stress causes cracks to expand. When the cracks are subjected to alternating stress over time, the material of the half shaft reaches a certain limit, and then the instantaneous fracture is the broken shaft. In actual production and use, the reasons for the breakdown of axles of agricultural vehicles are relatively complex, seldom due to unilateral effects, and are often the result of several factors working together. Therefore, the reasons for the following aspects are also taken into account when the half shaft is broken:
1, broken shaft caused by material defects. Due to defects in the material, the defect is divided into two kinds, internal defects and external defects. Both defects can reduce the strength of the material and act as a notch, where the crack source is generated and the crack propagates, resulting in the final broken shaft. Material defects such as shrinkage, loosening, overheating, overheating, and unreasonable flow line divisions all have an important influence on the initiation and propagation of cracks. If there is a material defect on the surface of the semi-axis, cracks will occur at the material defect under the cyclic load, which will eventually lead to fatigue fracture. If the direction of crack propagation is parallel to the banded structure or streamline, they will accelerate the fatigue fracture.
2. Broken shaft caused by improper design. Some of them are due to lack of design. The smaller semi-axle design on individual models is smaller in the size of the stepped arc, which tends to cause greater stress concentration. In long-term use, it often fails to reach the service life limit. .
3, broken shaft caused by improper processing. In actual machining of semi-shaft parts, due to improper machining methods or accidental damage, such as lathe machining, grinding machine machining, etc., and poor surface roughness, it is easy to cause broken shafts.
4, the semi-axis taper and hub taper does not match or wheel swing, etc., but also easily lead to broken shaft.
5, broken shaft caused by improper use and maintenance. The axles work under conditions of high speed and high pressure and road inequality. They have not been regularly repaired and inspected in accordance with the instruction manual. If the axle is overloaded for a long time, the stop washer fails, and the maintenance is improper, the rim runs in swinging motion. Oil, due to thermal expansion can also cause thermal fatigue off the shaft.
Second, preventive measures
1, the design and manufacturing unit requirements. Outsourced shaft materials are required to be inspected strictly in accordance with the inspection standards for purchased materials, and wastes cannot be imported into the production line. When designing the structure, the design department should avoid and reduce the stress concentration as much as possible. The diameter of the shaft section of the stepped shaft should not be too different. The fillet of the transition section should be as large as possible. If necessary, the excess section structure can be used. A stepped shaft section is provided so as to ease the change of section of the semi-axle. In production and processing, in the range of the local additional stress of the half shaft, the sharp corner transition of the cross section should be avoided, and the roughness of the surface should be increased beyond the level of 1.6-3.2.
2, the user's request. The load must be balanced. Do not unilaterally load or overload. It is also easy to produce broken half shafts. Maintain the vehicle well, check the axles according to the instructions in the instruction manual, and find out and deal with it in time to ensure the normal operation of the axles. When purchasing the axles, we must first select the regular manufacturers, because the regular manufacturers and processing equipment, processing technology, heat treatment process is more advanced, to ensure the quality of the axle. When purchased, the taper of the axle should match the taper of the hub.
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