Designing Accelerated Vibration Tests Using Model-Based Equivalent Damage Prediction

The use of vibration testing to complete qualification of critical components is important for a wide variety of industries to understand the life cycles of their products in operational environments. A common problem with testing components to failure is the time and cost associated with mimicking the full life of a part, creating a need for shorter-duration testing that provides comparable life cycle information. The most common methods that accelerate damage tests use Miner’s Rule, an equation that sums damage percentages caused by varying stress amplitudes. The aim of using Miner’s Rule in damage analysis is to find a shorter-duration test cycle that will provide equivalent damage to the part’s real-world environment. This method has demonstrated accuracy under constant amplitude loading but loses reliability under variable amplitude loadings due to its lack of regard toward the loading sequence. Furthermore, translating from a stress-cycle (SN) curve to design amplitudes for testing requires system knowledge. Finally, the entire process of damage equivalence for additively manufactured (AM) parts is minimally explored in current research. This study seeks to improve the quality of test acceleration by utilizing models of the system under test to not only provide a method for faster, more accurate equivalent damage analysis but also to fill a void of a lack of information regarding test compression of AM parts. To do this, AM specimens designed with a failure point under a complex stress history are evaluated. First, parts are vibration tested on a shaker to achieve experimental failure time. Next, the base inputs used for experimentation are modeled in simulation to evaluate theoretical failure time. Finally, test results of the experimental setup and simulated environment were compared to evaluate the accuracy of Miner’s rule in equivalent damage analysis, as well as test accuracy of SN curves for designing tests of AM parts.