Question

(a) Describe the events that take place when a specimen undergoes a tension test. Sketch a plausible (engineering) stress-strain curve, and identify all significant regions and points between them. Assume that loading continues up to fracture

Answer 1

• The specimen elongates linearly in response to the load to its proportionality limit.
• The specimen undergoes non- elastic deformation to its yield point.
• when stretched beyond its yield point, it deforms plastically until it reaches a maximum stress limit called the Ultimate tensile strength.
• If loaded beyond this, the material begins necking until fracture.

Step-by-step explanation:

The stress strain curve for a ductile material is shown in the attachment below.

A-B: There is a linear relationship between extension produced to load added. Point B is called the proportionality limit.

B-C: There a non linear extension of a material produced by the material in response to the applied load. Point C is called the Yield point. Beyond this, the material does not return to its original dimensions when the load is removed.

C-D. The material extends to a maximum point D, called the Ultimate tensile stress. Beyond this necking occurs.

D-E. Necking begins until the material finally fractures at point E.

Regions: A-C : Eleastic region

Regions: C-E : Plastic region

Regions: D-E : Necking region