Definition of Mechanical
Mechanical properties of steel are defined as the reaction of the
material to certain types of external forces. Mechanical properties
The maximum force that a material can withstand before fracturing.
Also called Ultimate Strength. This is usually reported in terms
of force per unit of area: lbs. per square inch or newtons per millimeter
The force that a material can withstand before permanent deformation
occurs. Also reported as force per unit of area.
The ability of a material to deform without fracturing. Generally reported
as elongation and reduction of area in a cross section that has been
Tensile, Yield, and Ductility of steel are determined by performing
a Tension Test in which a standard sample of the material is subjected
to a pulling force that increases gradually until the material deforms,
stretches, and fractures.
The resistance of the material to penetration. Not to be confused with
hardenability, which is a measure of the ability of a certain steel
to respond to heat treatment. Hardness is measured by applying a
standard force to the surface of the steel through a small, hardened
ball point, and then measuring the diameter of the resulting impression.
Hardness usually is reported as a value on one of two industry standard
scales, Brinell or Rockwell. Brinell hardness is usually more accurate
for measuring hardness of plate products.
The ability of a material to withstand a high velocity impact. Impact
strength is measured by subjecting a standard notched sample to a
swinging weight. As it is often important to know how the steel will
perform in colder environments, this test is often done at sub-zero
temperatures. Known as a notch test or Charpy test, the testing requires
three standard samples of a defined grain orientation. The results
are reported as foot-lbs or joules, showing the average of the three
specimens and the lowest value of the three, at the testing temperature.
Physical properties of steel pertain to the physics of the material,
such as density, electrical conductivity, and coefficient of thermal
expansion. The term “physical properties” is often used
erroneously to refer to mechanical properties.