PSI - Issue 57

Andrew Halfpenny et al. / Procedia Structural Integrity 57 (2024) 718–730

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Andrew Halfpenny / Structural Integrity Procedia 00 (2023) 000–000

Fig. 7. Statistical comparison between sources of uncertainty

Due to the extent of variability and uncertainty in the physical fatigue process, a direct comparison between simu lated and measured fatigue lives is problematic. A solution was proposed based on stochastic analysis using the Monte Carlo method to simulate variability and uncertainty. Research into Reduced Order Models showed that existing methods based on linear static superposition o ff er significant e ffi ciency savings in the Monte Carlo calculation by avoiding the need for repeatedly running expensive FE simulation. Research into Design Of Experiments highlighted three methods that were suitable for di ff erent design tasks. In the case of Design for Reliability, where the 50 th to 99 th percentile results are required, a method based on Latin Hypercube sampling was preferred. In the case of safety and extreme event modelling, methods based on Factorial sampling or Response Surface models were preferred. Research into statistical reliability analysis concluded that a priori assumptions on the life curve could significantly reduce the number of Monte Carlo simulations. The log-normal and Weibull distributions were found to o ff er excellent correlation with the variability and uncertainties associated with fatigue life. Weibull parameter estimation techniques based on Rank Regression methods were recommended for characterising test data with relatively few data points, and Maximum Likelihood techniques were preferable for characterising simulation test data. A case study showed how statistical reliability results from test and simulation could be compared directly in order to verify the simulation model to a specified confidence level. Further examples on the use of properly verified simulation models were proposed. Def Stan 00-35, 2021: Environmental handbook for defence materiel, part 3: Environmental test methods. UK Ministry of Defence. Halfpenny, A., 1999. A frequency domain approach for fatigue life estimation from finite element analysis, in: Key Engineering Materials. Trans Tech Publ, pp. 401–410. Halfpenny, A., Bonato, M., Chabod, A., Czapski, P., Aldred, J., Munson, K., 2019. Probabilistic fatigue and reliability simulation, in: NAFEMS World Congress 2019, 17-20 June, Quebec City, Canada. Halfpenny, A., Heyes, P., Kim, S.H., 2007. Statistically representative psd spectra for vibration induced fatigue analysis and testing, in: NAFEMS World Congress 2007. NAFEMS; NAFEMS. Halfpenny, A., Pompetzki, M., 2011. Proving ground optimization and damage correlation with customer usage. SAE Technical Paper 2011-01 0484. Halfpenny, A., Thumati, B., 2021. Accelerating fatigue qualification tests, in: Annual Symposium on Reliability and Maintainability (RAMS) 2021. Halfpenny, A., Walton, T., 2010. New techniques for vibration qualification of vibrating equipment on aircraft, in: Aircraft Airworthiness & Sustainment Conference, 2010. Hinton, E., 1992. Introduction to non-linear finite element analysis. NAFEMS. IEC62660-2, 2018. IEC 62660-2: Secondary lithium-ion cells for the propulsion of electric road vehicles - part 2: Reliability and abuse testing. International Electrotechnical Commission (IEC). ISO 19453-6, 2020. ISO 19453-6: Road vehicles — environmental conditions and testing for electrical and electronic equipment for drive system of electric propulsion vehicles — part 6: Traction battery packs and systems. International Organization for Standardization (ISO). References