Factors Affecting Elasticity – Physics

Effect of stress

• It is known that the action of large constant stress or the repeated number of cycles of stresses acting on a body decreases the elasticity of the body gradually.
• Taking these into account, the working stress on an engineering piece is kept far below its ultimate tensile strength.

Effect of temperature

• Normally the elasticity decreases with the increase of temperature.
• A carbon filament which is highly elastic at normal temperature becomes plastic when it is at high temperature.
• Lead is not a very good elastic material. But at low temperature it becomes a very good elastic material. Inwar is a special alloy used for making pendulums and elasticity is not affected when there is change in temperature.

Effect of impurities

• The elastic property of a material gets altered due to the addition of impurities.
• The addition of small amount of carbon in the molten iron, the elasticity of iron is increased largely. But if carbon content is more than 1%, then strength of iron decreases. But if the carbon content is more than 1%, then the strength of iron decreases.
• Similarly, the addition of potassium in gold increases the elastic properties of gold.

Effect of annealing

• A grain consists of many small interlocking crystals. The various heat treatment processes are adopted to get the desired physical and mechanical properties through the changes in micro constituents of the material.
• Annealing (heating and then slow cooling) is one of them, which is adopted to increase the softness and ductility in the materials. But it decreases the elastic properties of the materials by decreasing the tensile strength and the yield point of the materials. This is due to the formation of large crystal grains.

Effect of heat treatment and metal processing

• Hammering and rolling are the metal processing techniques to make thin plates and sheets. These break up the grains into smaller units or fine grains resulting in an increase of elastic properties.
• So, metals with fine grains are stronger than the metals with large (or) coarse grains. However for high temperature applications, we are using materials with large grains because they posses high creep resistance.

Effect of crystalline nature

For a given metal, the modulus of elasticity is more when it is in a single crystal form. In the polycrystalline state, its modulus of elasticity is comparatively small. However for the most of the engineering uses, we use polycrystalline form of metals due to its increased mechanical properties like ductility, malleability etc.