What are the Standards for Speed Verification?
In March, 2011, the ASTM E 2658 Standard Practices for Verification of Speed for Material Testing Machines
Do I Need to Verify Speed?
Some test methods define the testing speed and the speed accuracy requirements, and some do not. While the particular testing speed chosen is not always a critical parameter, it is often important and is always good testing practice to ensure that the speed is constant, stable, and repeatable. These reasons alone cause many users to request speed verifications of their testing machines. Other applications, where it is known or suspected that the material or component under test is strain-rate or speed sensitive, are more obvious candidates for requiring speed verification. Some examples include composites, carbon-fiber composites, ceramics, and liquid crystal polymers. If you are required to report test speed with your results, or if you are concerned with the consistency of results between machines or over time, good practice indicates that the machine's speed be verified. There are some applications where none of the above is a concern. For these, speed verification is probably not worth doing.
What Does Speed Verification Tell Me?
- Standard Verification: The standard speed verification measures the average speed between two positions. The crosshead or actuator is allowed a short time to accelerate to the set speed, then an accurate displacement reading and time reading are taken. A second set of displacement and time data points are taken after a specified travel or time (typically 2 to 4 inches or 30 seconds). These parameters are used to ensure a high level of accuracy in the speed measurement. This verification will tell you, under no load conditions, how closely matched your actual speed is to your set speed. You will also determine repeatability, since each speed is run three separate times. The initial velocity profile of the crosshead, minute fluctuations of speed during distance traveled, or speed accuracy under loading conditions will not be characterized.
- Advanced Verifications: For more demanding or critical applications, it can be useful to characterize the machine's performance at the initiation of the test and while applying forces similar to the actual test forces.
- Minimum Speed: none (extra charge may apply for speeds less than 1 mm/min)
- Maximum Speed: 1250 mm/min
- Displacement Accuracy of the Verification Standard: 5 - 10 microns, depending on the device
- Time Accuracy of the Verification Clock: 10 ms
- Accuracy of the Speed Measurement: 0.5% of reading
- Verification to Higher Accuracy or Higher Speeds: consult factory
- Speed Under Load: consult factory
How Can I Improve the Management of My Lab's Calibration Program?
Instron can make life easier for you.
- We will store all relevant information about your equipment and site in our database. That allows us to keep track of recalibration dates (specified by you), so we can call ahead of time to schedule convenient and timely recalibrations.
- When the verification is complete, the Instron engineer can print the certificate and data report on-site before leaving.
- The data and certificate are electronically backed up in a secure database at the Instron factory and can be retrieved, if necessary.
- Instron's highly trained calibration engineers know your equipment. They can identify potential problems early, perform preventive maintenance, and understand proper use and handling of your equipment.