Durability assessment of suspension coil spring considering the multifractality of road excitations

•Road excitation signals possess obvious multifractal properties.•Road multifractality is determined by road surface irregularities.•Fatigue life is predictable from road multifractality.•Three types of strain-life models are used to determine fatigue life.•All linear models gave good prediction of fatigue life with R2 above 0.8. This study presents the characterisation of multifractality of road excitation time series under different road conditions for prediction of the durability of a suspension coil spring. Road excitation acceleration signals and strain signals were acquired from the suspension system of a vehicle travelling under different road conditions. Multifractal analysis revealed a higher tendency to multifractality in road excitations with more surface irregularities. With the fatigue lives predicted by different strain-life models (Coffin-Manson, Morrow, and Smith-Watson-Topper), fatigue life prediction linear models based on road multifractality were established. It was found that the Morrow-based linear model gave the most accurate estimation of fatigue life, with the highest R2 of 0.8762. In conclusion, the models for the prediction of coil springs’ fatigue life based on road multifractality provide an accurate and faster alternative for durability assessment of coil springs. This can significantly facilitate the design process of coil springs to meet industry requirements.