Abstract
The current method of estimating the fatigue life of railway structures is to calculating the equivalent stress amplitude based on the measured stress data. However, the random of the measured data is not considered. In this paper, a new method was established to compute the equivalent stress amplitude to evaluate the fatigue damage based on the measurable randomness, since the equivalent stress is the key parameter for assessment of structure fatigue life and load derivation. The equivalent stress amplitude of a high-speed train welded bogie frame was found to obey normal distribution under uniform operation route that verified by on-track dynamic stress data, and the proposed model is, in effect, an improved version of the mathematical model used to calculate the equivalent stress amplitude. The data of a long-term, on-track dynamic stress test program was analyzed to find that the normal distribution parameters of equivalent stress amplitude values differ across different operation route. Thus, the fatigue damage of the high-speed train welded bogie frame can be evaluated by the proposed method if the running schedule of the train is known a priori. The results also showed that the equivalent stress amplitude of the region connected to the power system is more random than in other regions of the bogie frame.
Highlights
Safety is the most important property of a passenger railway vehicle
The equivalent stress amplitude is in normal distribution N(σ, s2), so the whole service life fatigue damage of the bogie frame can be calculated as following formula under the “3σ Principle”: D=
5 Conclusions Studies have shown that high-speed train bogie frame fatigue damage contains randomness though in the same operation route
Summary
Safety is the most important property of a passenger railway vehicle. The fatigue strength of a vehicle loading structure has a substantial impact on its safety, and must be comprehensively assured. A series of fatigue strength analysis methods for welded railway vehicle structures have been introduced to date [1], including fatigue assessment for constant amplitude loading by the endurance limit, evaluation of fatigue test programs by cumulative damage, and evaluation of simulated multiple body systems by cumulative damage. These methods are commonly applied in the railway industry [2,3,4,5,6]. Most published research are not determined based on actual, on-track test programs of the structure in question
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