stressArticle Free Pass stress, in physical sciences and
engineering, force per unit area within materials that arises
from externally applied forces, uneven heating, or permanent
deformation and that permits an accurate description and
prediction of elastic, plastic, and fluid behaviour. A stress is
expressed as a quotient of a force divided by an area. There are
many kinds of stress. Normal stress arises from forces that are
perpendicular to a cross-sectional area of the material, whereas
shear stress arises from forces that are parallel to, and lie
in, the plane of the cross-sectional area. If a bar having a
cross-sectional area of 4 square inches (26 square cm) is pulled
lengthwise by a force of 40,000 pounds (180,000 newtons) at each
end, the normal stress within the bar is equal to 40,000 pounds
divided by 4 square inches, or 10,000 pounds per square inch
(psi; 7,000 newtons per square cm). This specific normal stress
that results from tension is called tensile stress. If the two
forces are reversed, so