Hi,
I am tensile testing a titanium wire (grade 5) of 0.5 mm in diameter to find out it's Young's modulus. We don't have specific grips to test wires available, so I glued the wire in between two rectangular aluminium plates and gripped those plates in between standard wedge grips.
I get tensile strength around 1000 MPa, which seams reasonable but the Young's modulus is very low, around 30 GPa. Before I get back to the manufacturer, I'd like to ask your opinion about what might be wrong here.
The wire is sandwiched in between two Al plates, but the contact is not perfect. The glue hold the wire in place so it breaks somewhere in the middle and not close to the grips which is a good sign. Could it be that this method of gripping causes some misalignment of the specimen and I am not really testing for the Young's modulus?
Could you suggest any improvements in my set-up?
Thanks!
Sure this glue affects your results you may search for a grib suitable for your samples or producing another samples with dimensions suits your gribs or you can go for compression you can find young's modulus from it.
Dear Agnieszka
To find the Young's modulus of a metallic material, the tensile testing machine must be equipped with a special setup and you can not find the Young's modulus by the stress-strain curve.
Possibly you faced a problem of definition of the module on movement of captures(grips) , known for high-modular fibers. Judging by the text you had no extensometer. At measurement of the module on captures, deformation consists of deformation of a sample and deformation of a glues in captures(grips) and therefore deformation of a sample seems more, and the module less. I recommend to increase base to 300 - 400 mm, or to use the extensometer. As option - ultrasound.
Dear Agnieszka
I suggest you use the dynamic mechanical analysis (DMA) tests to find the Young Modulus.
Many thanks everyone for your contributions. Looks like this method is not even 'good enough', so I will send the samples to an external lab that owns proper grips or might go down the DMA route.
Dear Agnieszka,
When testing metallic materials there is always a problem in how the specimen is arrested or gripped to analyse the Young Modulus. Here, there is some different influences, like the specimen is not totally restrained or the own deformability of the machine. So, there is a general recommendation in these cases and it consists of using and extensometer fitted to the specimen or using and strain gauge glued also to the specimen. In this way, you will be sure of the deformability of the specimen and you will know the Young Modulus.
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