Fatigue strength analysis of bolster based on fini

Fatigue strength analysis of bolster based on finite element method (2)

2.4 improvement measures

the weakest part of bolster fatigue is at the sand leakage hole on the lower surface, where the damage is the most serious and the stress is large. It needs to be improved to extend the service life of bolster. The stress state and fatigue strength at the sand leakage hole on the lower surface are improved by the following methods:

(1) increase the radius of the fillet at the sand leakage hole on the lower surface, so as to reduce the stress concentration factor and reduce the degree of stress concentration

(2) improve the surface roughness at the sand leakage hole on the lower surface to reduce the fatigue strength

(3) increase the thickness of the part at the sand leakage hole on the lower surface, so as to improve the fatigue strength

(4) change the boundary conditions and load conditions of the bolster by optimizing the coordination with other components

(5) through work hardening or heat treatment, residual compressive stress is generated at the sand leakage hole on the lower surface, and the introduction of residual compressive stress will improve the fatigue strength

3 life estimation of bolster

Table 2 lists the recorded mileage of the loaded and unloaded vehicle load spectrum of 90.7 t gondola in the American maruyan locomotive standard. According to the load spectrum in the fatigue design standard of maruyan freight car in the United States, the S., V curves of b+ grade cast steel under different fatigue strength coefficients are taken as the basic S., V curves, combined with the fatigue weak parts of the bolster calculated by finite element analysis, and finally the fatigue life of the bolster is estimated by miner's linear cumulative damage theory

it can be seen from table 1 that the weakest fatigue part of the bolster is at the sand leakage hole on the lower surface, and this part is the most seriously damaged. As long as this part meets the fatigue life requirements, the whole bolster will meet the life requirements. Before unpacking, first check whether there is any life requirements outside the box. Therefore, the life of this part represents the fatigue life of the whole bolster

Table 3 and figure 5 show the fatigue life of bolster under different fatigue reduction factors

note: the fatigue reduction factor kf=1.5 ~ 2.0 represents the normal quality level of castings, and the casting defects at this level are the most common defect forms

it can be seen from table 3 that when the fatigue reduction coefficient is 2.0, the fatigue life of the bolster is 2.28 million km, which represents the normal quality level of the bolster. Therefore, the fatigue life of our bolster is 2.28 million km. When the running mileage ratio of empty vehicle to loaded vehicle specified in the specification is 0.95, the service life of the bolster under the condition of loaded vehicle is 15.2 years

it can be seen from Figure 5 that the fatigue reduction coefficient is inversely proportional to the service life. When the fatigue reduction coefficient is small, the service life of the bolster must not be expired. With K_ The fatigue life of bolster decreases gradually with the increase of. When kf=1.5 ~ 2.0, the fatigue life of the bolster decreases sharply with the decrease of K; When the fatigue reduction coefficient is greater than 2.0, the fatigue life of the bolster gradually slows down with the continuous increase of K. 4 conclusion

the fatigue strength evaluation of the bolster provides technical support for promoting the healthy and rapid development of the rare earth industry and its industrial chain in Fujian Province. The results show that under the condition of normal casting quality, the cumulative fatigue damage of each part of the bolster is less than 1, that is, the fatigue strength of the bolster meets the requirements of the design specifications

according to the load spectrum in the pill weir standard, under the corresponding fatigue reduction coefficient, the life of the weakest fatigue part of the bolster (the sand leakage hole on the lower surface) is evaluated by using miner's linear cumulative damage rule, and its life is 76 ~ 2.28 million km. If the heavy vehicle runs 150000 km per year, the fatigue life here is 5.2 ~ 15.2 years

the fatigue life of the bolster pushes the piston away due to the action of oil pressure, and gradually decreases with the reduction of fatigue reduction coefficient