The doctoral thesis presents an analysis of air spring design factors to determine their influence on air spring fatigue life. Some of the analysed design factors relate to the air spring itself (cord angle, diameter difference), while the other design factors relate to the design of the undercarriage (lever length, eccentricity, lever eccentricity, inclination). Using Taguchi methods, six design parameters and three interactions between the selected parameters were analysed. Life spans of air springs loaded with ±50mm displacement amplitude were used as the Taguchi analysis qualitative criteria. To determine life span, S-N curves from previous investigations and stress amplitudes calculated with FEM were used. The finite element model was validated with three experiments where air spring diameter and pressure were measured during one load cycle. The differences between the measured and calculated quantities were relatively small, therefore the finite element model was used to calculate stress amplitudes required for the calculation of life spans.
The analysis of variance presented here has shown that the diameter difference and lever eccentricity have significant influence on air springs life span. Interaction analysis has shown significant interaction between the diameter difference and cord angle, while other interactions haven’t shown a significant influence on the life span. Both parameters relating to the air spring itself have a significant influence on the air spring’s life span. The diameter difference has a direct influence, while the cord angle has indirect influence due to interaction between the diameter difference and the cord angle. Among design parameters relating to the design of the undercarriage, only lever eccentricity has a significant influence on an air spring’s life span.
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