Static Versus Dynamic Testing
What are the differences between static and dynamic testing as far as strain gage testing is concerned? In a static test the operator is able to read the value displayed on their instrument and then write that value down without it changing. Anything else is considered a dynamic test, where either the load or test specimen is moving or being acted upon.
In other words, if there is relative motion in either the test article or the loading sequence acting upon it, we have a dynamic environment. If we load the structure, take a reading, increase the load, and repeat, we are conducting a repeated static test.
In general terms, static tests are often conducted at the component level in incremental steps to determine structural integrity, or to validate FEA models. It's common to take the specimen to its load limits in order to correctly determine a safety factor. Static testing is considered safer to conduct when product performance is unknown, and can be used for preliminary testing.
Dynamic tests, on the other hand, are usually functional, fatigue, or life cycle tests of an entire assembly under anticipated operating conditions. These are often conducted outside of the laboratory environment in real-world conditions.
In most situations, the type of testing doesn’t influence the choice of strain gage or adhesive. It will, however, affect the type of environmental protection chosen, as well as the method of lead wire attachment and strain relief. Furthermore, it will have a significant impact on hardware requirements.
Most strain indicators and data acquisition systems can easily capture the signal from a static test. But when things are in motion there are a lot more factors to consider—such as the scanning rate, number of active channels, and any possible filtering, just to name a few.
For more information on selecting specific instruments to suit your application, please visit our website at www.micro-measurements.com.