| Since the beginning of mass production of G70 in 1997 in Xi'an Rolling Stock Works, there has been report on weld crack on bolster web now and then. MOR has conducted ring-line running experiment on various railway freight cars with 21t axle weight in the experimental base of CARS (China Academy of Railway Sciences). The result shows some cracks appearing on vertical weld connecting web plate of body bolster and draft sill as well as the part between web plate of body bolster and top cover plate. Having analyzed the development of the cracks, XRSW confirmed the cracks' resulting from fatigue. Ring test report shows us that transverse movement is a kind of coupling vibration by the frequency and original wave. In addition, the vibrating frequency and phase of A end and B end is almost the same that indicates the vibrating form is mainly transverse sway. This tells us that there is another vibration coupled with tank body which has close frequency. As the railway freight car develops towards heavy-load, Aiming at completely solving the problem, the paper has made special research on exterior factors for the forming of crack from the aspect of force bearing.In our previous design, for sampling, structure strength on rail cars is determined by static calculations. Even dynamic load is considered, the result is still calculated by static stress multiplied by dynamic coefficient. Though static calculations and static test are contented the special standard, but, in fact there are some cracks. According to the cause of cracks, alternation load plays a role as exopathic factor for the fatigue cracks. But the liquid swashing load is main reason of tank-car's alternation load. So, in designing of construction, excepting traditions' loads, it is content the fact to take the liquid swashing load.Adopting the principle of hydrodynamics, applying the research results of being, I have calculated that the inherent frequency of liquid transverse swashing in full load G70K is 5.1805, 8.8006 and 11.9639. The Min. frequency is close to horizontalvibration frequency of 3.75(G79K6283954) and 4.0~4.9(G70H6450103), showing that liquid & solid coupling vibration is much possible to happen;the liquid swashing load affects the loads on tank body and web plate on the body bolster under normal operation and the load resulted from liquid swashing keeps changing with time. Adapting with model of G70K tank body, comparing the result of finite element calculation (Software: Ansys) with stress analyses without considering load resulted from liquid transverse swashing, the paper has drawn a conclusion: As a result, we can regard liquid swashing load as one of the alternation loads which have resulted the cracks on web plate on body bolster.By above analysis, propose improvement to the structure of web plate on bodybolster through three means------enhancing the strength of web plate.;alternate thebend-resisting simulation through improving the shape of bolster side web;We can also changing the form of the technical holes on web plate to reduce the stress concentration around them. The occurrence of crack on tank body can also be avoided by improving manufacture technique, reducing welding flaws, lessening crack sources. |
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