A time domain approach to deal with fatigue effects due to pavement roughness on commercial vehicle structures was presented in this work. A versatile computational code was formulated to estimate the vehicle lifetime and to determine, alternatively, the respective reliability index. Structural weight optimization for a specified vehicle lifetime with a prescribed reliability index was also included. In order to get a good computational performance, it would be necessary to consider an ergodic process, where a unique sample is representative of the complete process. However, preliminary tests have shown significant variations in the lifetime among the different samples, due to the sensibility associated with fatigue analysis and due to the cycles counting process with the rainflow method. Therefore, it seems necessary to work with many samples sacrificing the computational performance. Looking for a good approximation of the results with respect to the real situation, a correct representation of the different pavement characteristics and vehicle velocity levels (including the time spent by each of these velocity levels) is necessary. Determination of the vehicle lifetime, the reliability index and the optimal weight is strongly dependent on specifications with respect to the form of the vehicle that has been used. In fatigue problems, where a high variability of parameters and results may be found, reliability analysis has a very important role to play. In the computational code, based on the algorithms described previously, the reliability index may be determined using MCSIAS or, alternatively, FORM. However, the most important aspect is the definition of the random variables and their respective distribution probability function. A closed solution for the reliability index, using FORM, was used in this work, improving the computational performance. Farkas' algorithm, used to optimize the structural weight, has shown to be a very robust method, but too many iterations were necessary to obtain the desired convergence. The fact that the reliability index may be used as a constraint in the optimization process emphasizes the importance of the computational code as an auxiliary tool for vehicle structural analysis and design.
Fatigue lifetime estimation of commercial vehicles
Schätzung der Ermüdungslebendauer von Nutzfahrzeugen
Journal of Sound and Vibration ; 291 , 1/2 ; 169-191
2006
23 Seiten, 7 Bilder, 3 Tabellen, 24 Quellen
Article (Journal)
English
Fatigue lifetime estimation of commercial vehicles
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