Experiment 2

A: Metals B: PolymersEng. Rihab K. Hamza

Theory• To study the behavior of materials when they are

subjected to loads is to perform the tensile test in laboratory.

• The mechanical behavior is essential for safe design of all types of structures

• Each material exhibits different mechanical properties. For example, metals show higher strength than polymers. However, polymers tend to be more ductile.

• In this experiment, tensile testing is conducted for;1. A metal either Aluminum or Plain Carbon Steel2. A Polymer either PMMA or Polyethylene.

Eng. Rihab K. Hamza

Objectives• Conduct the tensile test • Plot the Stress-strain Diagrams for the tested materials.• Determine the various Mechanical Properties of each material.

Which include:1. Modulus of elasticity or Young’s modulus (E),2. Yield strength (σy),3. Ultimate strength (σu),4. Fracture stress (σf )5. Ductility based on elongation and area, 6. Modulus of resilience (Ur) and7. Modulus of toughness (Ut).

Then ,• Describe the specimen profile at each step in the test for each material.• Describe the fracture pattern of each material.• Compare the obtained properties with the corresponding reported data in

your text book.• Compare between the mechanical behaviors of the tested materials

Eng. Rihab K. Hamza

Procedure

Measurements

Testing

Data AnalysisEng. Rihab K. Hamza

Measurements• To perform the tension test, a specimen of the

material is made into a “standard” shape and size according to ASTM standards.

(a) Metallic samples (b) polymeric samples.

Eng. Rihab K. Hamza

Measurements• The following dimensions should be measured

3 times and take the average• These dimensions are:1. Diameter (do) for the Metal2. Width (Wo) and thickness (to) for the polymer3. Gauge length (Lo)

Eng. Rihab K. Hamza

• Metal

• Polymer

SampleAverage diameterdo (mm)

Average AreaAo (mm2)

Average Gauge Length

Lo (mm)

Carbon Steel

Aluminum

SampleAverage width

w (mm)Average

thicknesst (mm)

Average AreaAo (mm2)

Average Gauge Length

Lo (mm)

PMMA

Polyethylene

Eng. Rihab K. Hamza

Stress – Strain Testing

Eng. Rihab K. Hamza

Stress – Strain Curve

Eng. Rihab K. Hamza

Engineering Stress and Strain

Eng. Rihab K. Hamza

Yield Strength, σy• Stress at which noticeable plastic deformation has occurred.

σy = yield strength

Eng. Rihab K. Hamza

Tensile Strength, TS• Maximum stress on engineering stress-strain curve.

Eng. Rihab K. Hamza

Ductility• Plastic tensile strain at failure:

Eng. Rihab K. Hamza

Resilience, Ur

Eng. Rihab K. Hamza

Toughness

Eng. Rihab K. Hamza