Fatigue Load Testing
A fatigue load test is the cyclic application of force onto a part or assembly under various load, frequency, and environmental conditions to understand the lifespan of the part. This can be helpful during the development of a new part for it to be approved for use, or in periodic QA checks of production parts. Fatigue load testing often ends when the part cracks, cannot meet the performance requirements, or completely breaks. One of the main goals of fatigue testing is the development of an S-N curve to be able to statistically predict the performance of a part under various stress levels.
Oftentimes during a product development cycle a DFMEA, or design failure modes and effects analysis will be performed to try to predict how a part will fail and what the effects will be, and for mechanical systems an ultimate test can be the main method of validating those analyses. An FEA might accurately tell you where the highest stress concentration will be, but it may not be able to accurately predict the lifespan of the part since it cannot account for all the manufacturing tolerances or other effects of the manufacturing process that can affect fatigue life. The best method of determining failure modes and effects is to conduct an accelerated test that most closely replicates the conditions that the component or assembly will experience during years of use.
If you are not sure what sort of performance you need out of your component it can be helpful to run a series of competitor components at the same time and under the same conditions. The fatigue life of the competitor components can be a benchmark to determine if your product will be competitive in the market.0
You can also benchmark your own product if you are going to change to a new manufacturing process, or would like to compare various suppliers. Because even small and imperceptible changes in a part can have a significant effect on fatigue life it can be important to run a series of tests to reduce the risk of premature failures by testing a statistically significant number of parts and comparing the distribution of results of different batches.
Clark Custom Designed Testing
Clark Testing specializes in designing custom test setups based on our customer’s needs. We have the capability to design control systems to apply multiple loads based on custom load profiles while recording data on any number of channels needed. Our design engineers can work with your CAD model and our FEA software to design frames and fixtures for your testing to ensure that the test can be conducted under circumstances that are as close to field conditions as possible.
Clark Fatigue Load Testing Capabilities
- Vertical and horizontal load frames with 55,000 lb, 100,000lb and 1,000,000+ lb capabilities
- Data acquisition on dozens of channels at rates up to the mhz range
- Strain gage application and data recording
- Displacement or elongation measurement
- Servohydraulic controlled actuators to apply loads
Clark Test Report
Clark’s test reports adhere to the quality requirements of ISO 17025:2017 and will include.
- An overview and summary of the testing performed
- A detailed list of the setup and NIST-traceable instruments that were used
- The test method used
- Test results; including load vs time, data tables, comments and observations from the test
- Photographs of the test setup and the parts for failure analysis
Fatigue load testing often has certain common results that are recorded, such as.
- Load vs time
- Maximum cycles
- Strain measurement with strain gauges
- Stress vs number of cycles, also called an S-N curve