Material testing is important in big industry, where manufacturers must be able to trust the properties of the raw materials they’re using. The rest of us generally take a supplier’s word for it that they’re giving us what we’ve paid for. However, you could always take on material testing yourself with the Universal Tensile Testing Machine from [Xieshi Zhang].
Unlike a six-figure industrial machine, this build is much more affordable, costing on the order of $300 to build. It uses an Arduino to read a tensile strain gauge, and is capable of applying up to a kilonewton of force. To achieve this, it uses a NEMA 17 stepper motor driving a lead screw to apply tensile strain or compression to the specimen under test. The test fixture is assembled from 3D-printed components, and built on top of a piece of aluminium extrusion.
Fundamentally, it’s a smaller version of a machine most engineering undergraduates will see in a materials lab experiment. It could be highly useful for anyone wanting to experiment with 3D printed structures; it would be more than capable of testing various filaments and infill types for their tensile and compression performance. Video after the break.
Looks like the micro version of the big beastie we used in TSM240 (something something and materials). Would be great to get these into some high school stem labs.
So is it plotting youngs modulus?
For a linear material, at least, Young’s modulus is a number (Pa or psi) which is the slope of the linear portion of a stress versus strain graph. If the machine records the extension of the specimen versus the applied load, and the dimensions of the specimen are known, the Young’s modulus can be calculated. Strain = deltaL/L, stress = F/A, where: deltaL is the extension of the specimen, L is the un-stressed length of the specimen, F is the load force, A is the cross-sectional area of the specimen. Then, Young’s modulus = E = stress/strain, the slope of the stres-strain curve’s (initial) linear portion.
A giant version of this can be found at Kirkaldy’s testing works (https://www.testingworks.org.uk/) which is well worth a visit. Under the motto ‘Facts not Opinions’, Kirkaldy was an early player in the field of standardized materials testing.