Understanding Stress and Strain Curves

What does the initial straight-line portion (OA) of the stress-strain curve represent?

• Plastic deformation

• Elastic deformation

• Ultimate tensile strength

• Breaking point

According to Hooke’s Law, which equation correctly relates stress and strain in the elastic region?

At which point on the curve does permanent (plastic) deformation begin?

• Point O

• Point A

• Point B (Yield point)

• Point D (Breaking point)

What is the significance of the area under the entire stress-strain curve up to the breaking point?

• Young’s modulus

• Material toughness

• Ultimate tensile strength

• Proof stress

Which point on the curve corresponds to the ultimate tensile strength (UTS)?

• Point A

• Point C

• Point D

• Point O

If a material is loaded up to the elastic limit and then unloaded, what will happen?

• It will break

• It will return to its original length

• It will remain permanently deformed

• It will become tougher

What does the breaking point (E) on the stress-strain curve indicate?

• The material’s yield strength

• The maximum stress the material can withstand

• The point where the material fractures

• The start of plastic deformation

Which of the following best describes proof stress?

• The stress at which a material breaks

• The stress required to produce a specified amount of permanent deformation (usually 0.2%)

• The maximum stress a material can withstand

• The stress at the elastic limit

What is the unit of stress in the metric system?

• Newtons (N)

• Pascals (Pa)

• Joules (J)

• Metres (m)

If a material has a high Young’s modulus, what does this indicate about the material?

• It is very ductile

• It is very stiff

• It is very tough

• It is very brittle