Under axial loading, which force causes a member to lengthen?

Under axial loading, which force causes a member to lengthen?

• A. Compression
• B. Tension
• C. Shear
• D. Torsion

Answer: (B)

In axial loading, the way the ends are loaded determines how the length changes. When the member is in tension, the ends are pulled apart, so the material stretches and becomes longer. The amount of elongation depends on the force, the original length, the cross-sectional area, and the material’s stiffness (Young’s modulus). A simple expression is delta L = F L / (A E), which shows positive elongation for tension. Compression does the opposite, pushing ends together and shortening the member. Shear causes sliding between material layers and changes shape without a true increase in length along the axis. Torsion twists the member around its axis and also doesn’t produce lengthening along the axis. So the force that makes the member lengthen is tension.

In axial loading, the way the ends are loaded determines how the length changes. When the member is in tension, the ends are pulled apart, so the material stretches and becomes longer. The amount of elongation depends on the force, the original length, the cross-sectional area, and the material’s stiffness (Young’s modulus). A simple expression is delta L = F L / (A E), which shows positive elongation for tension.

Compression does the opposite, pushing ends together and shortening the member. Shear causes sliding between material layers and changes shape without a true increase in length along the axis. Torsion twists the member around its axis and also doesn’t produce lengthening along the axis. So the force that makes the member lengthen is tension.