﻿ Material properties - Engineer Student

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# Material Properties

Different metals have different properties, so if you are in the design stage of a project it is important to spend some time researching the limits and properties of materials and compare them to your requirements before you make your choices. Why spend a fortune on a pricey material when a cheaper alternative will do just as well for what you require?
Here is a basic break down of properties associated with metals and what they mean.

## Tensile Strength

Tensile strength is the ability to withstand tensile forces. The object below is withstanding the combined tensile force of 4kN.

## Ductility

Ductility is the ability to shape without cracking. For example if you wish to form a 90° bend into a thin steel bar it would have to be quite ductile to avoid it splitting and cracking along the bend. Heating the area to be bent can temporarily increase the ductility.

## Density

Density is defined as the ratio of an objects mass to its volume. What makes one material less or more dense than another is down to how tightly packed the atoms are which make up that material, more atoms packed within a set area the more dense the material will be. An example of a low density metal would be Aluminium. An example of a high denisty metal would be Tungsten.

## Hardness

Hardness is the ability to withstand indentation. There are a number of scales and systems used to measure the hardness of a material, for example Vickers, Brinell and Rockwell.

## Brittleness

Something that is brittle is likely to shatter, crack, or split when struck with a certain force. For example glass is usually considered to be brittle.

## Toughness

The resistance to fracture when stressed, this is different to tensile strength as the stress applied to find the tensile strength is just tension where toughness can be found by seeing how much energy the material can absorb before rupturing.

## Malleability

Malleability is the ability of a material to be deformed without shattering or breaking, an example of a malleable material is Lead.

## Yield Strength

The yield strength is defined as the stress at which a predetermined amount of permanent deformation occurs.

## Young's Modulus of Elasticity

Is defined as the ratio of the uni-axial stress over the uni-axial strain, for example a metal rod is being held at each end and is being pulled with forces of X at each of these ends, the rod is likely to stretch under these stresses and it’s the rods ability to return to its original shape once the forces are released which is measured as its modulus of elasticity. Strain is defined in mechanics terms as change in length divided by the original length.

## Shear Modulus

Shear modulus describes a material's response to shearing strains, this is when the material is under a force parallel to one of its faces, again this modulus is concerning the materials ability to return to its original shape.