Stress-Based S–N Base Function with Shear Modulus for Fatigue Assessment on Industrial Isolators

Background It is impossible to generate all of the S–N curves for antivibration design and applications under a wide range of rubber compounds in industry. It saves substantial costs if an S–N curve can be calculated from a known stress-based S–N base function. Objective To predict fatigue life of antivibration isolators based on an existing stress-based S–N curve of a known material. Methods The cylinder dumbbell specimens subjected to 30 fatigue cases with different R ratios were used to generate a stress-based S–N base function with the shear modulus using the effective tensile stress criterion. The function was then applied to the ring specimens in 90 fatigue cases, followed by the industrial product MDS (Multidirectional Snubbing) mounts. Results Correlations were found between the critical locations and the maximum values of the effective tensile stress in all fatigue cases. All predicted points were within a scatter band of 0.9 in the cylinder dumbbell specimens. When the function was used, approximately 87.8% of the points (79 of 90) fell within the scatter band of 2.0 in the ring specimens and the crack initiation would occur at approximately 86 kcycles against observed severe damage at 400 kcycles in the MDS mounts. Conclusions This approach seems effective, and the application can save significant cost in industry by eliminating substantial fatigue tests. The S–N base function obtained can be useful for engineering design and applications where no fatigue data are available.