MECHANICAL PROPERTIESOF MATERIALS

Engineering Materials

THE MECHANICAL PROPERTIES OF A MATERIAL DESCRIBE HOW IT WILL REACT TO PHYSICAL FORCES.

DENSITY, DUCTILITY, MALLEABILITY, STRENGTH, ELASTICITY, HARDNESS AND TOUGHNESS/BRITTLENESS ARE MECHANICALPROPERTIES USED AS MEASURES OF HOW MATERIALS BEHAVE.

DENSITYThe density, or more precisely,

the volumetric mass density, of a substance is its mass per unit volume. For a pure substance the density has the same numerical value as its mass concentration.

To simplify comparisons of density across different systems of units, it is sometimes replaced by the dimensionless quantity "relative density" or "specific gravity", i.e. the ratio of the density of the material to that of a standard material, usually water. Thus a relative density less than one means that the substance floats in water.

Osmium and iridium are the densest known elements at standard conditions for temperature and pressure but certain chemical compounds may be denser.

The density of a material varies with temperature and pressure. This variation is typically small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object and thus increases its density. Increasing the temperature of a substance (with a few exceptions) decreases its density by increasing its volume

DUCTILITYIs the property that

enables a material to stretch, bend, or twist without cracking or breaking. This property makes it possible for a material to be drawn out into a thin wire.

Platinum is the most ductile material known.

MALLEABILITYIs the property that enables a

material to deform by compressive forces without developing defects. A malleable material is one that can be stamped, hammered, forged, pressed, or rolled into thin sheets.

Most Malleable Material: GOLD

STRENGTHStrength is the property that

enables a metal to resist deformation under load.

ELASTICITYIs the ability of a material to return to its original shape after the load is removed. Theoretically, the elastic limit of a material is the limit to which a material can be loaded and still recover its original shape after the load is removed.

HARDNESSIs the property of a material to resist indentation and scratching. Because there are several methods of measuring hardness.

Hardest on Earth: DIAMOND

TOUGHNESSIs the property that enables

a material to withstand shock and to be deformed without rupturing. Toughness may be considered as a combination of strength and plasticity.

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