Analysis of the damaged end of reducer shaft from analysis and coping strategies

In order to realize the fast firing and thin material production, supporting the speed and driving device of rotary kiln was changed, the increase of rotational speed of rotary kiln to 315 r/ min, the main motor power is 75 kW, speed of 1000 r/ min, a former reducer transmission ratio was changed, the transmission input shaft of the rotary kiln. After the transformation of the assembly sketch.

From 2004 after the transformation, the input shaft has been broken from the F surface two times, resulting in the two stop kiln. From the point of view of the fracture surface of F, the fatigue fracture. So the axial strength analysis and calculation.

2 strength check

211 bending torque diagram

Then, according to the static equilibrium condition, the force of A and C points is calculated, the force diagram is made, and the bending moment diagram and torque diagram of XY and XZ plane are calculated, and the bending moment diagram is calculated according to the third strength theory. The moment diagram of the additional force F 0 is produced due to the coupling manufacture and installation error which results in the circle diameter of the pin of the additional circumferential force coupling.

212 check the shaft fatigue strength

According to the structure size and moment axis diagram, diagram of torque, maximum bending moment section at B, but here the largest diameter; the moment F section is larger, smaller diameter, and the fillet stress concentration caused the F surface for the dangerous section.

Bending moment on the left side of the face in the moment of torsion shearing stresses due to the rotation of the shaft, the bending stress caused by cyclic bending moment; the torque is always some changes, and the one-way transmission torque, so the shear stress for pulsating cyclic stress. The safety factor is not up to the requirements.

3 reason analysis

It can be seen from the calculation results of the strength of the upper shaft

Full coefficient less than allowable safety factor. The shaft shoulder fillet stress is large, in the long-term stress, here gradually formed micro cracks, severe crack tip stress concentration, the crack expands gradually, when the crack gradually extended to a certain length, they may suddenly expand rapidly, the member section seriously weakened, along the last section serious a weakened brittle fracture.

4 treatment measures

(1) the shaft gear left face all flat out, a car with 120 mm * 65 mm hole, and car out of a 60 degree bevel, one end is thick with the diameter of 120 mm K6 120H7 diameter hole shaft is inserted into the welding; (2) the original input shaft bearing diameter with the diameter of 65 mm to 80 mm diameter, bearing from the original 7613 to 7516E. by 7516E and the outer diameter of the 7613 bearing outer diameter of 140 mm, the coupling at the diameter of 60 mm to 70 mm diameter, so as not to expand in the bottom case of reducer bearing increases the shaft diameter; (3) to determine the shoulder fillet. The positioning sleeve on the shaft is removed, and the shaft shoulder positioning bearing is replaced. Bearing transition fillet r = 2, in the absence of assembly requirements, as far as possible to take a large angle, when there is a comprehensive consideration of accessories; (4) the selection of elastic column pin coupling B6 model. To ensure that the motor and reducer input shaft concentric; (5) bearing assembly, positioning correctly. Bearing installation to keep 0.25 ~ 0.4 mm gap, to meet the requirements of shaft thermal expansion.

5 axis after the fatigue strength check

Axis of the F surface after the diameter of 90 mm, according to the above formula to calculate the further calculated to meet the safety requirements of 2.

6 Conclusion

After the repair, the production of rotary kiln is restored in time. And draw two important conclusions: one is the shaft diameter changes lead to stress concentration is the main cause of fatigue fracture, the design must be stress concentration in surface to avoid the high load area; two is in the maintenance to ensure the installation quality, timely inspection and maintenance, to ensure the normal operation of equipment.