Order of Elongation in Mild Steel before Fracture

Mild steel is a commonly used construction material known for its high strength, ductility, and ability to undergo plastic deformation before fracture. Elongation refers to the increase in length of a material when subjected to tensile stress. It is typically expressed as a percentage of the original length of the specimen. In the case of mild steel, the order of elongation before fracture is 1%.

Explanation:
To understand the order of elongation in mild steel before fracture, let's break down the process step by step.

1. Tensile Testing:
The elongation of a material is determined through a tensile test, which is a standard laboratory procedure. In this test, a specimen of mild steel is subjected to an increasing tensile load until it fractures. During this process, various mechanical properties of the material are measured, including yield strength, ultimate tensile strength, and elongation.

2. Elastic Deformation:
Initially, when a tensile load is applied to the mild steel specimen, it undergoes elastic deformation. In this stage, the material stretches proportionally to the applied stress. The elongation is directly proportional to the applied load and follows Hooke's law, which states that the deformation is linearly related to the stress.

3. Plastic Deformation:
As the load increases, the mild steel specimen reaches its yield point. At this point, the material transitions from elastic deformation to plastic deformation. Plastic deformation refers to the permanent change in shape or size of a material without returning to its original state after the load is removed.

4. Necking:
During plastic deformation, the mild steel specimen undergoes necking, which is a localized reduction in cross-sectional area. This necking occurs due to non-uniform distribution of stress along the specimen. The necked region undergoes higher elongation compared to the rest of the specimen.

5. Ultimate Tensile Strength:
As the load increases, the elongation of the mild steel specimen continues until it reaches its ultimate tensile strength (UTS). The UTS is the maximum stress that the material can withstand before fracture occurs. At this point, the elongation reaches its maximum value.

6. Fracture:
After the elongation reaches its maximum value, the mild steel specimen fractures. Fracture can occur either in a ductile or brittle manner, depending on the specific conditions and characteristics of the material. However, mild steel is known for its ductility, which means it undergoes significant plastic deformation before fracturing.

Conclusion:
In the case of mild steel, the order of elongation before fracture is 1%. This means that the specimen can undergo plastic deformation and elongate up to 1% of its original length before it fractures. The ability of mild steel to undergo such elongation makes it a suitable material for various structural applications where ductility is required.