Page 83 - CITS - WCS - Mechanical

WORKSHOP SCIENCE - CITS

EXERCISE 7 : Stress & Strain

Concepts of stress & Strain: Modulus of elasticity, Stress- strain curve. Hook’s law, different module of
elasticity like Young’s modulus, modulus of rigidity, bulk modulus and their relations.

Poisson’s ratio: Stress is the force exerted per unit area and strain is the physical change that results in response
to that force.
Stress is the ratio of force over area (S = R/A, where S is the stress, R is the internal resisting force and A is the
cross-sectional area). Strain is the ratio of change in length to the original length, when a given body is subjected
to some external force (Strain= change in length ÷the original length).
There are three types of stress: compression, tension, and shear. Stress can cause strain, if it is sufficient to
overcome the strength of the object that is under stress. Strain is a change in shape or size resulting from applied
forces (deformation).
SI unit of stress is N/m2or Pa, s s expected by the units, stress is given by dividing the force by the area of its
generation, and since this area (“A”) is either sectional or axial, the basic stress formula is “σ = F/A “.
Hooke’s law states that the strain of the material is proportion to the applied stress within the elastic limit of that
material. When the elastic materials are stretched, the atoms and molecules deform until stress is applied, and
when the stress is removed, they return to their initial state.

Modulus of elasticity
Modulus of Elasticity, also known as Elastic Modulus or simply Modulus, is the measurement of a material’s
elasticity. Elastic modulus quantifies a material’s resistance to non-permanent, or elastic, deformation. The
Elastic Modulus is the measure of the stiffness of a material. Elastic modules, also known as Young’s modulus,
is a fundamental property of materials that measures theirs stiffness or resistance or elastic deformation under
stress. This property is essential in engineering and materials science, as it determines a material’s ability to
support loads and maintain its shape.

70