Failure Analysis of Large Components Using Rising Step Load and Residual Stress Analyses

"Every failure could be stopped the next time". While it's common to focus on one cause, the reality is that most failures are influenced by several different variables. Metallurgical failure analysis is often combined with other assessments like stress testing and finite element analysis to more accurately confirm and understand why the failed part or system did not perform as expected. As the severity of failure occurs, the need for more detailed and quantitive testing increases. Often a full-scale or partial-scale model is built at substantial expense to evaluate failures believed to be from common mechanisms like hydrogen embrittlement or stress corrosion. If smaller-scale samples can be economically tested with good correlation, then many more failures could be quantitatively understood.

The rising step load method has been successfully used for analyzing failures due to many different common failures modes, including stress corrosion cracking and SSCC, hydrogen embrittlement, fatigue cracking, and corrosion fatigue. By varying environmental conditions such as temperature, chemistry, pH, and applied potential, many different failure modes can occur. Two very powerful methods to accurately understand how those conditions affect a specific failure are residual stress analysis and the rising step load method. These methods can be used to assess large components accurately and using similar environmental conditions. The use of RSL and stress analysis will be discussed in light of numerous large components and systems.