Question 1

What does the slope of the linear stress–strain curve represent?

Accepted Answer

In the linear elastic region, the slope represents Young's modulus. Young's modulus is longitudinal stress divided by longitudinal strain, so a steeper initial curve indicates a stiffer material.

Question 2

Why is B called both the elastic limit and the yield point?

Accepted Answer

B marks the end of completely recoverable elastic deformation. If the specimen is unloaded after passing B, it does not return to its original length because permanent plastic deformation has begun.

Question 3

What happens at C and D on a ductile stress–strain curve?

Accepted Answer

C is the ultimate tensile strength point, where stress reaches its maximum. Beyond C a ductile metal develops necking, stress falls, and the specimen finally fractures at D.

Question 4

How does a brittle material differ from a ductile material?

Accepted Answer

A ductile material undergoes a large plastic strain before fracture and can develop necking. A brittle material such as glass has little or no plastic deformation and fractures soon after its elastic range.

Question 5

What happens when a plastically deformed wire is unloaded?

Accepted Answer

The unloading path does not follow the original straight line back to O. It reaches the strain axis at a positive permanent strain, showing that the original shape and length are not fully recovered.

Stress–Strain Curve Lab — Watch a Wire Go from Elastic to Fracture

About this lab

Practice