Th Lession Mechanical Properties of Mate

MECHANICAL PROPERTIES OF
MATERIALS

Objectives
On completion of this section, students will be able
to:
•
understand the classification of engineering
materials based on mechanical properties.
•
gain skill on mechanical properties of metals
•
understand the fracture mechanism of metals

Stress Strain Curve

Force
Stress =
Area

Unit stress

• A stress upon a structure at a certain place,
expressed in units of force per unit of crosssectional area, as in pounds per square inch.

• Strain =

Elongation
Originallength

Direct Strain
• Strain is defined as "deformation of a solid due to
stress"

Shear Strain
• Shear strain is the ratio of deformation to original
dimensions. In the case of shear strain, it is the
amount of deformation perpendicular to a given
line rather than parallel to it.
• In engineering, shear strain is defined as the
tangent of the angle, and is equal to the length of
deformation at its maximum divided by the

perpendicular length in the plane of force
application, which sometimes makes it easier to
calculate. Strains measure how much a given
deformation differs locally from a rigid-body
deformation.

Stress-Strain Curve