How does a structure deform when subjected to an axial load? We can easily visualize this by drawing a square grid on a flexible sheet of material as shown below on the left. When a uniaxial tensile load is applied to the sheet of material, the square grid deforms as shown below on the right. What can we conclude from this deformation?

First of all, the deformation is uniform, indicating that the strain, and thus stress, distributions are also uniform. Second, the lengths of the sides of the squares change, but there are no changes in angle. Thus the deformation is a result of only normal strains, and not shear strains. Thus, axial loading creats a state of uniform normal stress and strain. In the below video, we will use these observations in order to determine the force-displacement relationship for an axial loaded member.