Dry surface of each beam to attach angle brackets and label. Use epoxy to glue angle brackets to the top center of bottom face, approximately 10 1/2 inches from the ends. The top face is the finished, rough surface. Mark this location before gluing.
Mark the beams 1 1/2 inches from the ends and 3 inches from the bottom/top on the rough and smooth bottom/top surfaces. These markings will be used for the deflection frame.
Mark the beams 1 1/2 inches, 7 1/2 inches, and 13 1/2 inches from the end.
Load the sample into the 20-kip testing frame. Use a loading head with two rollers spaced 6 inches apart. Attach the pin and rollers from the bottom of the base plate with bolts.
Attach the deflection frame by screwing it into the points marked on the beam with the LVDT holder just under the angle bracket.
Set up the load controller. Connect the controller to the load cell and LVDT. Test the load.
Record data from tests including load at breaking, distance between edges on which the sample is supported, average sample breadth, and average specimen depth. Convert the breaking load to pounds and all the other measures to inches.
Multiply the breaking load by three and by the distance between edges on which the sample is supported.
Multiply two by the average sample breadth and the square of the average sample depth.
Divide the first number by the second number. The result is the value of the modulus of rupture in pounds per square inch.