Material Properties I

 Tensile Test:

Tensile test determines the strength of the material when subjected to a simple stretching operation. Typically, standard dimension test samples are pulled slowly at a uniform rate in a testing machine while the strain is defined as :

Engineering Strain = Change in Length / Original Length

The engineering stress is defined as:

Engineering Stress = Applied Force / Original Area 

Slide 1 shows the stress-strain diagram of a ductile material where the linear portion of the graph indicates elastic deformation.

Slide 1-Stress -Strain Diagram

Slide 2-Fracture of a Flat Tensile Test Specimen

 

Modulus of Elasticity: The initial slope of the curve, related directly to the strength of the atomic bonds. This modulus indictes the stiffness of the material. (Modulus Elasticity is also known as Young's Modulus)

Modulus of Elasticity = E = Change in Stress/ Change in Strain

Tensile Strength: The maximum stress applied to the specimen. Tensile strength is also known as Ultimate Strength. (The highest point on the stress-strain diagram)

Slide 3- Modulus of Elasticity

Slide 4-Tensile Strength

 

Ductility: The total elongation of the specimen due to plastic deformation, neglecting the elastic stretching.

Toughness: The total area under the curve, which indicates the energy absorbed by the specimen in the process of breaking.

Slide 5-Ductility

Slide 6-Toughness

 Extensometer: The instrument that measures the elongation of a material while applying tension.

Slide 7-Tensile Test Machine

Slide 8-Extensometer

 

Slide 9-Measurement of Elongation

Slide 10-Comparison of Breaks

 

 

Back to Table of Contents

Last updated: August 31, 2000

By: Serdar Z. Elgun