Vibration and Random-Fatigue Qualification of Printed Photopolymer Components: Spectral Loading, Fixtures and Damage Accumulation

Random vibration cannot be qualified by quoting an overall acceleration alone. A power spectral density distributes energy across frequency, and the response depends on resonances, damping, boundary conditions, fixture dynamics, preload, temperature and the evolving stiffness of the printed material. Printed photopolymers add orientation, surface state, cure history, ageing and viscoelastic frequency dependence. Consequently, two tests with the same root-mean-square acceleration can produce different stresses and damage.

This review defines a non-compensatory framework for vibration and random-fatigue qualification of printed photopolymer components. It separates input control from local response, requires low-level modal surveys before and after exposure, treats fixture and control strategy as parts of the experiment, and distinguishes resonance shift, crack initiation, functional interruption and final fracture. Spectral fatigue estimates may support test design, but they require validated stress transfer, an applicable fatigue model and a declared treatment of mean stress, bandwidth and non-Gaussian response. Miner summation is an assumption, not a material law. Direct fatigue evidence for printed photopolymers exists for selected material-jetting systems, while comprehensive random-vibration datasets remain limited. The defensible result is therefore a configuration-specific qualification, not a universal PSD or fatigue-life transfer rule.

Keywords: printed photopolymer; random vibration; power spectral density; resonance; fatigue; fixture; damping; spectral moments; qualification