Wedge Tensile Test -MTS
Wedge Tensile Test -MTS
(OP)
My Problem: I cannot collect an accurate modulus of elasticity for a round (.357" DIA - 1018 Steel). Using built in MTS TestWorks software to calculate Stress/Strain curves and built in functions to estimate the modulus of elasticity, the numbers that I am reading are Modulus of elasticity = 17.34 GPA(2515 ksi) for 1018 steel. 1018 steel should have a modulus of elasticity that is about 200 GPA.
I have some round tensile test specimens that have been machined to certain ASTM specs that have two flat gripping surfaces. I am using an MTS tensile test machine with hydraulic wedge grip style heads. My first test on the machine I compressed the clamping surface into a pancake and it skewed all of my data. Since the grips are knurled, I clamped the specimen so that there is no plastic deformation; however, the surface has knurl marks. The test is being conducted at .026 in/min (Determined by ASTM).
I have checked all of the functions in the software to make sure there was nothing silly throwing my E value off by a factor of 10. Is there any thing I am doing wrong that I might be doing?
Thanks,
Chris
I have some round tensile test specimens that have been machined to certain ASTM specs that have two flat gripping surfaces. I am using an MTS tensile test machine with hydraulic wedge grip style heads. My first test on the machine I compressed the clamping surface into a pancake and it skewed all of my data. Since the grips are knurled, I clamped the specimen so that there is no plastic deformation; however, the surface has knurl marks. The test is being conducted at .026 in/min (Determined by ASTM).
I have checked all of the functions in the software to make sure there was nothing silly throwing my E value off by a factor of 10. Is there any thing I am doing wrong that I might be doing?
Thanks,
Chris





RE: Wedge Tensile Test -MTS
First things I'd check for is that you're not having any slipping of the specimen with respect to the jaw faces, and that all grips/accessories/etc. are adequately preloaded. You could also try testing some other specimens on this frame (preferably more compliant specimens) to determine if it's application specific or if you have a systemic problem.
RE: Wedge Tensile Test -MTS
RE: Wedge Tensile Test -MTS
This is my 3rd internship; however, this is the first internship that I have worked with materials testing. The specimen is not slipping with respect to the face, because I can see the knurl marks very clearly on the surface. I will work on posting a picture. I will investigate the preload on the hardware, It is in calibration. I am working on trying to get some flat specimens as well to test.
Compositepro,
Extensometer
RE: Wedge Tensile Test -MTS
Have you checked the extensometer calibration against a calibrator (it like a large screw micrometer)? There are many settings to adjust on an extensometer.