Young's Modulus

Definition - What does Young's Modulus mean?

Young's modulus is defined as the ratio of stress below the proportional limit to the corresponding strain. It is a measure of the rigidity or stiffness of a material. In terms of the stress-strain curve, Young's modulus is the slope of the stress-strain curve in the range of linear proportionality of stress to strain.

The greater the modulus, the stiffer the material; in other words, the elastic strain resulting from the application of a given stress is smaller. The modulus is an important design parameter used to compute elastic deflections.

Young's modulus is also known as elastic modulus.

Corrosionpedia explains Young's Modulus

When corrosion due to oxidation in an acidic environment takes place on a metal surface, the metal tends to lose its stiffness and its Young's modulus or modulus of elasticity decreases, which makes it prone to higher rates of failure, as there is a mismatch of stress and strain application on the surface of the material.

Young's modulus is a material property that describes a materials' stiffness and is therefore one of the most important properties of solid materials. It is the ratio of stress to strain when deformation is totally elastic. Stress is defined as force per unit area and strain is defined as elongation or contraction per unit length. This modulus may be thought of as a material’s resistance to elastic deformation. A stiffer material has a higher elastic modulus. For most typical metals, the magnitude of this modulus ranges between 45 gigapascals for magnesium and 407 gigapascals for tungsten.

There are three types of moduli:

  • Elastic Modulus (Young's Modulus): The ratio of longitudinal stress to strain
  • Shear Modulus: The ratio of tangential force per unit area to the angular deformation of the body
  • Bulk Modulus: The ratio of stress to the fractional decrease in the volume of the body

The stress-strain curve is used to measure elastic modulus and shear modulus. The parameters used to describe the stress-strain curve of a material are tensile strength (ultimate strength), yield strength (or yield point), percent elongation and reduction of area. A material that has a higher elastic modulus is said to be stiffer than one with a lower elastic modulus. Modulus of elasticity has the same dimension as stress because it results from dividing the stress by the strain.

Values of the elastic modulus for ceramic materials are about the same as for metals; for polymers they are lower. These differences are a direct consequence of the different types of atomic bonding in the three material types. Furthermore, with increasing temperature, the modulus of elasticity diminishes.

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