Success through Failure with Accelerated Stress Testing
Breaking Your Product Can be Good for Design
08 June 2021
When you're dealing with new materials, environments, or requirements, how do you get valid information? Testing the way you traditionally have can give you questionable information. Using a properly designed accelerated test to assess failure points can help you identify non-intuitive failures that would normally require months or years in the field to identify. By doing this earlier in the development process you can save time and potentially avoid significant issues.
Having the right information to make good decisions can ultimately keep a product from failing validation testing and can provide more useful information throughout the design and production process. The key is highly focused information that doesn't come from conventional, statistics-based tests but through accelerated stress testing (AST) that provide specific failure mode information that can drive design change, improve warranty periods and extend life spans.
Each step of the development process requires decisions to be made: Can the design concept be brought to market successfully? Does the design meet engineering, customer, and industry objectives? Does the production process produce the design? Testing is all about providing information to make decisions. The right test not only produces the key information but produces the information at the right time.
Conventional tests determine the fail/pass point for a group of samples when subjected to a single stress point and need to be repeated for each different state of stress. They give statistical data and are necessary to demonstrate compliance with customer requirements and industry regulations. However, they don't necessarily identify weaknesses in materials, designs, construction, or end-products. Accelerated stress testing determines failure modes for a small group of samples when subjected to different levels of multiple, simultaneously applied stress sources. AST can be a valuable tool in product development and exceeds statistical verification for requirements and regulations.
There are several methods for running AST on products:
- Highly Accelerated Life Test (HALT): HALT is sometimes used as a generic name for accelerated testing to failure. It is structured to provide context to failure modes relative to operational and destruct limits of a product. During the HALT process, a product is subject to increasing levels of stress specifically related to the operation of a product. Structured to provide context to the failure modes relative to the operational and destruct limits of a product, HALT looks not only at what will fail and what cases the failure, but also how the failure ranks against specific specifications.
- A Failure Mode Verification Test (FMVT) reveals inherent design weaknesses by determining multiple failure modes and root causes. It measures both the "time to" and "number of" failures to measure opportunities for improvement or maturity relative to the technological limit. FMVT is intended to provide context to the failure modes relative to the maturity of the design or in comparison to similar designs. It examines what will fail, what will cause the failure, and how the failure ranks against other failures.
- Key Life Test (KLT)/Full System Life Test (FSLT): KLT/FLST determines a product's reliability for a given combination of stresses on a full system. These tests evaluate product changes and ensure a product's reliability. By putting objects through simulated real-life conditions, these tests determine if a product can meet a determined minimum life.
- Accelerated Reliability Test/Accelerated Life Testing: Several sets of parts are tested at stress levels much higher than expected until enough data is collected to fit a math model to the stress, time to failure and probability of failure space for a given failure mode. These tests ultimately determine the expected minimum life of a product.
AST provides a list of observed failure modes for a given product, and this information can be used in redesign efforts or for general product information and expectations. To determine which test is best suited for your needs it is important to consider: information goals, key data needed to move a project forward, and the information that would allow validations of assumptions that decisions are made on, both for business and engineering. Knowing this will determine the best test and next steps.
Find out more about the benefits of AST, including case studies and insights on test set-up and equipment, in our webinar recording.
Global Director of Engineering
Alex Porter is the Director of Global Engineering for Intertek and has been with the company since 1992. He has been developing accelerated testing methods for mechanical components and systems since 1996 and holds three patents related to accelerated testing equipment and authored more than 40 articles and technical papers on accelerated testing. Porter is the author of the book "Accelerated Testing and Validation" (Elsevier, 2004) and teaches a class for SAE based on the book. He is a member of SAE, holds a B.S. in Aircraft Engineering, an M.S. in Mechanical Engineering, and is a Professional Engineer in the State of Michigan.