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Assembly
SAFETY PROTOCOL
ASTM E8 and ASTM A370 give a general technical standard for Tensile Testing. ASTM A931 gives a techncial standard for steel wire strands, and can be referred to while performing the experiment on a steel wire. It is important to operate the mechanism in a safe way. While performing the experiment, safety glasses need to be worn. The wire needs to be inserted into a piece of small plastic piping to prevent the wire from hurting anyone when it snaps.
Step 1: Assemble the rectangular metal plates on the frame
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Make sure the wire is as taut as possible. This will help it to go into tension a lot quicker.
Step 4: Stretch the Wire
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Using a Torque wrench set at the appropriate Torque, tighten the bolt. This rotary motion of the bolt is transferred into a linear motion which pulls the wire towards the First Plate.
The wire breaks after a certain point. Measure the length that the coupling nut moves, and this can help to calculate the strain of the wire.
Look closely at the wire where it broke. You should see some necking, which is a type of failure where there is a large localized decrease in area of the part due to tensile loading the part. Here, the wire should have some material in the middle with surface area smaller than that of the actual wire. This bit of material is what tries to resist the load while the material around it tears/breaks, and is the last connective “tissue” that the wire has right before it breaks into two.
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The Solidworks Model for this version of the Axial Testing Machine can be found on GrabCAD.
Next Versions
A prototype of a newer version of the axial machine that includes keyless drill chucks as clamping devices for the wire has already been made.
A load cell needs to be added to measure the torque acting on the bolt, and a vernier caliper needs to be installed to accurately measure the distance that the wire is stretched. This needs to be physically added to the prototype, as the CAD models are already completed.
References
[1] “The Online Materials Information Resource,” MatWeb. [Online]. Available: http://www.matweb.com/search/datasheet.aspx?matguid=29709d152e1142f5b05db70440d62c2a&n=1&ckck=1 . [Accessed: 12-Nov-2021].
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