During the gear meshing process, the teeth of the driven wheel are in contact with the driving wheel, and the tooth tip is swept toward the root. The root portion tends to bear the maximum alternating bending stress, while the tooth surface of the node line is subjected to the pulsating alternation. Compressive stress. The lower surface hardness of the tooth causes the contact surface fatigue strength of the gear surface to decrease, and the severely worn tooth surface and surface pitting and even the peeling pit are formed under the action of alternating stress. A lower hardness at the root of the tooth will reduce the bending fatigue strength of the gear. In addition, there is inclusions in the place, so under the action of alternating stress, the fatigue cracks sprout and expand at the root.
Discussion of the test results It can be seen from the above test analysis that the fracture of the gear belongs to fatigue fracture, and the fatigue crack originates from the root of the tooth. The root of the tooth is not a martensite structure, the hardness is low, and it is subjected to the maximum alternating stress. When the fatigue strength of the material is insufficient to withstand the load force, the fracture of the fatigue property occurs.
The surface hardness of the tooth is relatively low, which causes the gear surface to form severe wear during the transmission process. Under the contact stress, the tooth surface forms contact fatigue damage. In addition, the gear material has more serious structural defects, casting defects and larger size inclusions, which reduces the fatigue resistance of the material.
Conclusions and suggestions There are inclusions in the gear material and the hardness of the root surface is low. Under the action of alternating stress, the fatigue crack originates at the root of the tooth and finally causes the gear to break. It is recommended to select gear materials and processing technology according to the gear use conditions to ensure sufficient tooth surface hardness and good organization state; comprehensively test the gear running condition to obtain specific data of gear running condition, and provide gear design and processing. in accordance with.
Discussion of the test results It can be seen from the above test analysis that the fracture of the gear belongs to fatigue fracture, and the fatigue crack originates from the root of the tooth. The root of the tooth is not a martensite structure, the hardness is low, and it is subjected to the maximum alternating stress. When the fatigue strength of the material is insufficient to withstand the load force, the fracture of the fatigue property occurs.
The surface hardness of the tooth is relatively low, which causes the gear surface to form severe wear during the transmission process. Under the contact stress, the tooth surface forms contact fatigue damage. In addition, the gear material has more serious structural defects, casting defects and larger size inclusions, which reduces the fatigue resistance of the material.
Conclusions and suggestions There are inclusions in the gear material and the hardness of the root surface is low. Under the action of alternating stress, the fatigue crack originates at the root of the tooth and finally causes the gear to break. It is recommended to select gear materials and processing technology according to the gear use conditions to ensure sufficient tooth surface hardness and good organization state; comprehensively test the gear running condition to obtain specific data of gear running condition, and provide gear design and processing. in accordance with.
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