Nonlinear Characteristic Analysis of a Coil Spring Isolator in a State of Perfect Compression

This study analyzed the nonlinear dynamic behavior of a cylindrical coil spring under full compression. While previous research has primarily focused on the linear characteristics of springs, this study considers the nonlinear response arising from interwire friction and contact. To achieve this, the Rayleigh energy method is applied to theoretically derive the dynamic characteristics of a spring-mass system, and the results are validated through experimental analysis. The experiments include stiffness measurement using a universal testing machine and dynamic response analysis employing a laser Doppler vibrometer and accelerometers. Time-frequency analysis is conducted under single and multiple impact conditions using short-time and fast Fourier transform to quantitatively evaluate the dynamic behavior of the spring. The findings of this study are expected to contribute to the design of spring-based isolators in defense applications and the evaluation of operational characteristics in extreme environments.