Assembly and Operation of Axial Testing Machine

Owned by Ankitha Kishorchandra (Deactivated)
Last updated: Dec 16, 2021
4 min read

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

  • The frame needs to be stable, so it can be fixed on a table using a c-clamp or held within the jaws of a vice. The vice is a better option because the c-clamp only fixes the bottom of the frame to the table and allows it to rotate.

  • Place the First plate between two brackets on the edge of the frame.

  • Use the T-Slot fasteners to secure the brackets to the frame.

  • Use M5 bolts and nuts to fix the Plate to the bracket.

  • Place the Middle plate between two brackets placed right after the end of the First plate’s brackets, and repeat the same procedure.

  • Place the End plate on the other end of the frame, between two brackets, and repeat the procedure.

Step 2: Insert the Hex bolt and coupling nut

  • Insert the Hex Bolt into the First plate such that its inner face coincides with the outer face of the plate. The other end of the bolt should pass through the slot on the Middle plate.

  • Now insert the coupling nut from the opposite side of the Middle plate, until it meets the Hex bolt.

  • Tighten the bolt until the face of the coupling nut lines up with the inner face of the Middle plate. Make sure that the head of the bolt still coincides with the outer face of the First Plate.

Step 3: Add the Wire

  • Measure out a length of wire, free of kinks, long enough to run the length of the space between the U-Plate and the End Plate, and then some more to account for securing the wire to the pins. For safety, first insert the wire through some plastic piping that is as long as the distance between the End Plate and the end of the Middle Coupling nut. For visibility purposes, the photos on this wiki don’t have the plastic piping.

  • Tie one end of the end around the small hole on the side of the U-Plate welded to the Coupling nut. Wrap the remaining wire twice around the pin, and make sure the wire is not slack anywhere.

  • The wire should now run over the top of the pin and pass through the slot on the U-Plate. Take the other end of the wire, pass it through the slot on the End Plate, wrap it twice around the pin on its U-Plate, and then tie the remaining wire around the hole on the side.

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

  • 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.

Distance moved by the wire

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].