Experimental Procedures

1. Measure and record the length of each side, the angle between each side, and the orientation angle for each square.

   

   Digital and Dial Calipers

   Vernier Caliper

    

2. Sandwich both ends of the specimen between the specimen shields as the sample is loaded into the universal testing machine.

3. Remove the slack, and measure the distance between the crossheads.
    
4. Elongate the sample, at 1.5 to 2.0 inches/min, until the distance between the crossheads has increased approximately 1.5 to 2.0 inches.  This will ensure a sufficiently large size change in the squares once the load has been removed.

   

5. Remove the sample from the testing machine.  Be careful not to touch the printed squares, as the ink will now be broken and easily wiped off.
    
6. Remeasure the lengths and angles, excluding the orientation angle for each square.
    
7. Calculate the average normal and shear strain experienced by each square.
    
8. Use the strain values to calculate the principle-axis angle of rotation, the principal strains, and the maximum shear strain, thereby determining the direction and magnitude of the applied strain field.