Mechanics of Materials: Axial Loads

Force and Load

Tension

• A type of axial load that causes a material to stretch or elongate
• Results in an increase in length and a decrease in cross-sectional area
• Examples: pulling a rope, stretching a spring

Compression

• A type of axial load that causes a material to compress or shorten
• Results in a decrease in length and an increase in cross-sectional area
• Examples: compressing a spring, squeezing a rubber ball

Bending

• A type of transverse load that causes a material to deform by bending
• Results in a change in shape, but not length
• Examples: bending a beam, flexing a tree branch

Moments

• A measure of the turning effect of a force around a pivot or fulcrum
• Calculated by multiplying the force by the distance from the pivot to the line of action of the force
• Units: Nm (newton-meters) or ft-lbs (foot-pounds)

Shear Force

• A type of transverse load that causes a material to deform by sliding or rotating
• Results in a change in shape, but not length
• Examples: cutting with scissors, torsion on a shaft

Reactions

• Forces that occur in response to an applied load or force
• Equal in magnitude, but opposite in direction to the applied force
• Examples: the upward force of a table on an object, the normal force of a surface on an object

Axial Loads

• Tension causes a material to stretch or elongate, resulting in an increase in length and a decrease in cross-sectional area.
• Examples of tension include pulling a rope and stretching a spring.

Axial Loads

• Compression causes a material to compress or shorten, resulting in a decrease in length and an increase in cross-sectional area.
• Examples of compression include compressing a spring and squeezing a rubber ball.

Transverse Loads

• Bending causes a material to deform by bending, resulting in a change in shape, but not length.
• Examples of bending include bending a beam and flexing a tree branch.

Moments

• A moment is a measure of the turning effect of a force around a pivot or fulcrum.
• Moments are calculated by multiplying the force by the distance from the pivot to the line of action of the force.
• Units of measurement for moments include Nm (newton-meters) and ft-lbs (foot-pounds).

Shear Force

• Shear force causes a material to deform by sliding or rotating.
• Shear force results in a change in shape, but not length.
• Examples of shear force include cutting with scissors and torsion on a shaft.

Reactions

• Reactions are forces that occur in response to an applied load or force.
• Reactions are equal in magnitude, but opposite in direction to the applied force.
• Examples of reactions include the upward force of a table on an object and the normal force of a surface on an object.