12. Accumulated Lifetimes in Single-Axis Vibration Testing

Vibration qualification testing verifies and quantifies a system’s longevity in its proposed service environments. Service environments a system could encounter can impart many ranges of excitation in all directions; however, multi-axis excitation testing capabilities for simulating realistic environments are rare and costly. Therefore, multiple, single-axis vibration tests are commonly used to qualify a system and its components to a lifetime of service environments. Quantifying the equivalent amount of time a component has been tested can be difficult when limited to single-axis tests. Further complications arise due to the fact that real-world service conditions are often measured at a system level without instrumentation on each component. In addition, many mechanical systems include joints and contact surfaces that, if altered, can significantly change the component’s vibration characteristics. This makes replicating the boundary conditions of each component difficult. Therefore, another crucial part of single-axis vibration testing is determining boundary conditions to replicate best the real-world environment onto each component. This paper aims to analyze the effects on lifetime estimates using single-axis vibration testing of components under variations in boundary conditions, testing strategies, control locations, and other configuration options. Methods such as power spectral density (PSD), fatigue damage spectrum (FDS), and Miner’s Rule, with quantities such as fatigue cycles, peak response, and RMS response are used to evaluate boundary conditions, study the response of the components, and determine the severity of various test strategies as it pertains to the overall lifetime of the system.