Strain and stress are the two relative factors that affect the mechanics of the substance. The first is associated with the force as imparted upon the product and the second is the deformation as occurs due to the force as given in the substance. Both aspects are relative to each other. The relation between these two factors of cause and effect determines the endurance of the substance and its functionality. These factors are responsible for the alteration in the mechanics of the products.

Formula of strain 

Stress is the factor that is associated with the force that is applied to a product that determines the mechanics of the product. 

𝜎 = F/A ; 𝜎 = stress ( N/m2) , F= force , A = the cross-sectional area. This is the formula of stress. 

Strain is the deformation that occurs due to the force as received by the substance. 

𝜀 = L-L0 / L0 ; 𝜀 = strain , L = change in length , L0 = original length. This is the strain formula.

Shear strain and other types of strain

The strain is classified into various sections

• Normal strain: It is the change in the form of the substance, which is associated with the ratio of change in the length of the body in comparison to its previous length..
• Shear strain: This strain refers to the angular alteration of the product because of the force received.
• Volumetric strain: Volumetric strain is associated with the alteration in the volume of the substance. This type of strain is also called a bulk strain because it involves the entirety of the volume of the substance. 

Different types of stress

The stress can further be classified into various sections, 

• First being the normal stress in this case the force is applied parallel on the surface of the substance, 
• The second is the shear stress, which is rather imparted parallelly on the product. 
• The third is the longitudinal stress in which the substance alters in length. This type of stress is further classified into two categories, tensile stress in which the length of the substance is altered abiding by Newton’s third law of motion. The second is the compressive stress in which the length of the product is shortened. Shearing stress is the force applied tangentially upon a substance.

Relation between strain and stress

The relation between strain and stress is observed through the stress-strain diagram. Most of the materials exhibit a distinct relation between stress and strain. This strain and stress relationship is defined by Hooke’s law. This point of the ratio between the strain and stress is called the proportional limit. The slope of the curve is referred to as the modulus of elasticity of young’s modulus. The modulus of elasticity is responsible for the measurement of the rigidity of the substance. In case of elasticity limit the deformity that has occurred due to the applied stress is reversed when the force is removed and thus the strain is altered. It is at the yield point that the strain increases at a faster rate as compared to the stress and the material undergoes a permanent alteration. It is at the ultimate stress point that the substance breaks down completely after enduring the maximum amount of stress. This determines the endurance and the load factor of the substance. The breaking point denotes the point where the material breaks down completely after enduring the maximum amount of stress. The aforementioned aspects determine the relationship between the strain and stress upon a substance and the resultant change in its mechanics.

Conclusion

It is the relationship between strain and stress that determines the functionality of the product, and its resultant mechanics. The stress as applied upon a substance in association causes the deformity that is the strain as received by the substance,which is resembled, by the deformity.Mathematically these two aspects are calculated in ratios and the stress-strain graph.The stress-strain graph ascertains the relation between these two correlative factors of cause and effect.The stress and strain of particular as imparted upon a particular product alters its functionality and mechanical and thus the mechanical properties of the stress and strain are studied to narrow down the technicality of the aspects of the study.