* Point B is called the elastic limit point. Point A is called limit of proportionality. * Upto point A, Hooke's Law is obeyed and stress is proportional to strain. The stress-strain curve diagram for a ductile material like mild steel is shown in figure below. Showing thereby that there is no initial stress of strain in the specimen. The stress-strain diagram is shown in figure. The strength of a material enables it to resist fracture under load.
Where, P = Standard load, D = Diameter of steel ball Brinell hardness test is used to check hardness. Hardness is the ability of a material to resist indentation or surface abrasion. Toughness is the property of a material which enable it to absorb energy without fracture. A malleable material possess a high degree of plasticity, but not necessarily great strength. Malleability is a property of a material which permits the material to be extended in all directions without rapture. A material is said to be brittle when it cannot be drawn out by tension to smaller section. The characteristic of the material by which it undergoes inelastic strains beyond those at elastic limit is known as plasticity.ĭuctility: Ducitility is the characteristic which permits a material to be drawn out longitudinally to a reducd section, under the action of a tensile force (large deformation).īrittleness: Brittleness implies lack of ductility.
A material in plastic state is permanently deformed by the application of load and it has no tendency to recover. Plasticity: Plasticity is the converse of elasticity. Some properties of materials which judge the strength of materials are given below:Įlasticity: Elasticity is the property by virtue of which a material is deformed under the load and is enabled to return to it original dimension when the load is removed. N = 1 elastic solid For most metals, 0.1< n < 0.5
The stress-strain diagram is shown in the figure. The volume of the specimen is assumed to be constant during plastic deformation. Where σ and ε is the engineering stress and engineering strain respectively. The volume of the solid is not changed by shear strain.īulk Strain True Stress and True StrainThe true stress is defined as the ratio of the load to the cross section area at any instant. Shear strain Note 1: The angle is radians, not degrees.