Analysis of The Reasons For The Fracture of Gear Shaft

- Oct 30, 2020-


How much do you know about the hard-tooth surface reducer? When using it, I will briefly introduce the reason for its gear shaft fractures:

1. In terms of material selection for the gear shaft of the hardened surface reducer, for the shaft that mainly transmits power, select high hard and better quenched and tempered steel according to the transmitted torque and the corresponding journal size. However, it can be known from the metal graphic analysis that the material of the pinion shaft has a loose structure and super inclusions. As a result, the impact toughness is reduced, and under the action of high variable load, the crack propagates rapidly, leading to fracture.

 

2. In terms of structural design, there is almost no transition fillet at the shaft shoulder after surfacing repair, causing serious stress concentration and fatigue cracks under bending stress, which is the main reason for shaft fracture.

 

3. In terms of heat treatment, prior to the surfacing repair, preheating treatment is not performed as required, and there is a difference in the structure around the welding area. This difference exists in a narrow area and will produce high internal stress. Due to the effect of this internal stress, Cracks occurred immediately after the phase transformation, which eventually led to fractures. After the shaft was repaired by surfacing, proper heat treatment was not taken. The welding residual stress was relatively large, which reduced the shaft's alternating stress resistance. Once it encountered vibration, cracks were easily generated. , Resulting in breakage.

4. In terms of processing technology, it has been tested that the machining deviation at the journal of <160 is large, which makes the shaft and the inner ring of the bearing relatively loose, causing the shaft and the inner ring of the bearing to rotate relative to each other, that is, running the inner ring, which causes the inner ring of the bearing to be on the shaft. Sliding causes shaft wear, which is another major factor leading to shaft wear and fracture.

5. In terms of bearing load, it can be seen from the force analysis of the gear shaft that the gear bearing is subjected to relatively large bending moments and torques. The bending moment generates normal stress on the shaft and torque generates shear stress. These stresses are constantly changing during the operation of the shaft and are symmetrical. Cyclic alternating stress and additional dynamic load at the same time, once encountered vibration, overload, sudden start and braking and multiple heavy load impact, the shaft is prone to cracks and breaks.

After understanding the reasons for the fracture of the gear shaft of the hardened gear reducer, I believe it will provide you with greater help in the future use, which is also more conducive to our use.