Improving HALT Testing and Quantification with FDS Analysis

Highly accelerated life testing (HALT) identifies potential failure modes and operating limits in a brief timeframe. Generally, engineers control the vibration portion of a HALT test using overall acceleration (gRMS) as the sole metric. gRMS is a broad-spectrum intensity measurement that allows engineers to make decisions with a simplified version of their product’s response. A more comprehensive and accurate metric that considers relative fatigue is needed to improve confidence when setting HALT test durations and determining when to remove a test item from the table or stop the test. This paper presents an approach that improves the quantification of the vibration portion of a HALT test using fatigue damage spectrum (FDS) analysis. The FDS allows engineers to analyze the vibratory environment from a HALT machine and compare it to a desired accrued fatigue level. Applications of the new approach include 1) analyzing variations in relative fatigue due to a change in mass, position on the HALT table, or orientation, and 2) comparing the accrued fatigue for multiple samples while monitoring critical components and known or suspected failure locations. This paper provides example applications that support the proposed method over the standard gRMS metric.