For most solids, it lies between 0.25 and 0.35. Theoretically, the value of ‘σ’ should be less than 0.5. ‘σ’ being a ratio of two types of strains, has no unit and is dimensionless. Σ = lateral strain/longitudinal strain = (∆D/D)/(∆L/L)

The Poisson’s ratio ‘σ’ of the material of the wire is If the length increases by ‘∆L’ and the diameter decreases by delta ‘∆D’, then It is a constant for the material of the body.Īs shown in Figure #1, a wire of original length ‘L’ and diameter ‘D’ is subjected to equal and opposite forces ‘F’, ‘F’, along its length. The ratio of the lateral strain to the longitudinal strain is known as the Poisson’s ratio. The fractional change in the direction along which the forces have been applied is called the longitudinal strain, while the fractional change in a perpendicular direction is called the lateral strain. At the same time, it also contracts along the perpendicular directions. When two equal and opposite forces are applied to a body along a certain direction, the body elongates along that direction. When strain is small, the ratio of the normal stress to the volume strain is called the bulk modulus of the material of the body. When strain is small, the ratio of the longitudinal stress to the corresponding longitudinal strain is called the Young’s modulus of the material of the body. Its value is equal to the ratio of stress to strain and corresponds to the initial slope of the stress-strain curve. The modulus of elasticity is a measure of the elastic deformation of a metal when stressed in tension or compression within the proportional limit. Modulus of Elasticity in Tension and Compression The stiffness of a metal is measured by the moduli of elasticity in tension, compression, and shear, by Poisson’s ratio, and by the bulk modulus of elasticity. The remedy is to increase the cross-section of the beam. The strength will be increased, but if the load is the same, the beam will still sag about the same amount. If a steel beam sags too much under load, nothing will be gained by changing to a stronger alloy steel. Peculiarly enough, the stiffness of a metal is varied very little by alloying with other elements. Since the deflections produced in many products by operating loads may affect the workability of the components, the stiffness of the material is often a limiting design factor. The resistance of a metal to elastic deformation is called its stiffness of metal.

Orcaflex contact stiffness values