Straight Down The Middle! Alignment Of Universal Testers
Tensile testing is a commonly-used method for determining material properties. To achieve this accurately the universal test machine must be calibrated. For example, the load cell can be compared to a calibration reference.
In addition the upper and lower grips of the machine must be parallel and axial. If they are not, any tensile test performed will have increased uncertainty in the results, leading to non-linear data, inaccurate material property measurement and premature failure.
This test is generally performed using a precision-machined test piece with strain gauges mounted in locations specified by the relevant standard. This can take the form of a cylindrical sample with 4 gauges around the circumference (0, 90, 180,270°) in up to 3 axial locations for up to 12 gauges.
The strain gauges have to be precisely positioned which can be a significant challenge in itself. What is just as important is that all of the gauges are identical. Typical gauges have uncertainties in the 0.5-1% range, but Micro-Measurements Advanced Sensors Technology effectively eliminates this issue. The unique manufacturing and adjustment process ensures each gauge is virtually identical.
With Advanced Sensors Technology strain gauges used in the load cell, alignment specimen and on the tensile test samples, the entire measurement chain has reduced uncertainty. This leads to increased confidence in the test results through the entire measurement process.
In this iNotes video, Bruno Belanger, president of Bcomtesting, Inc. shows how composite samples are set up using strain gages (gauges) for testing according to ASTM D3039. Actual data is then recorded.