Submitted by: Asif Ahmed TonmoyID: 131-23-3505 ; Sec: D (L3T1)

Assignment topic: Stress-Strain Curve

Submitted to: Lecturer

Daffodil International University

Mousumi Rahman Hashi

For Example

What Is Stress?• A tension or

compression stress created in a structural member by the application of a lengthwise load.

• stress is defined as the force per unit area of a material.

• i.e. stress = force / cross sectional area

What Is Strain?• Increase (or decrease) in

length resulting from a stress acting parallel to the longitudinal axis of the specimen.

• strain is defined as extension per unit length.

• Strain = extension / original length

Stress-Strain Curve for Textile Fibre

Typical regions that can be observed in a stress-strain curve are:

• Elastic region,

• Yielding,

• Strain Hardening,

• Necking and Failure

Stress-Strain Curve for Textile Fibre

Elastic Behavior

• If the specimen returns to its original length when the load acting on it is removed, it is said to response elastically

Yielding

• A slight increase in stress above the elastic limit will result in permanent deformation. This behavior is called yielding

• The stress that causes yielding is called yield stress sy.

• The deformation that occurs is called plastic deformation

Strain Hardening

• When yielding has ended, a further load can be applied to the specimen, resulting in a cure that rises continuously but becomes flatter until it reaches a maximum stress referred to as ultimate stress, su.

• The rise in the curve is called Strain Hardening

Necking & Fracture• After the ultimate

stress, the cross-sectional area begins to decrease in a localized region of the specimen, instead of over its entire length. The load (and stress) keeps dropping until the specimen reaches the fracture point.