02_MM-242L Tensile Testing basics for materials

1. EXPERIMENT
NO.1
TENSILE TESTING OF METALLIC MATERIALS

2. introduction
 Mechanical testing provides the link between the
mechanical properties and performance of
material.
 A large range of mechanical tests has been
evolved to characterize the different mechanical
responses of the engineering materials
 To predict the performance as realistically as
possible
 To select and design of engineering components
 The tensile test is the most widely used test of this
category.

3. The tension test
 The tensile test can be used to obtain several
mechanical properties of materials that are
important in design using INSTRON tensile testing
machine.
 A specimen is deformed, usually to fracture, with
a gradually increasing tensile load that is applied
uniaxially along the long axis of a specimen.
 As a result of tensile testing, we get a stress-strain
curve from where we obtain useful information to
determine the mechanical behavior of the
specimen.

4. Sample specs.
 A standard “Dogbone” sample having circular or rectangular
cross-sectional area with specific dimensions is used for tensile
testing.
 Why dog-bone sample?

5. parameters
 Yield Strength
 Ultimate Tensile strength
 Fracture stress
 Ductility
 %age reduction in Area
 % age Elongation.
 Elastic & Proportional Limit
 Elastic Modulus
 Toughness & Resilience

6. Important definitions
 Yield Strength σy
 The level of stress from where plastic deformation begins (maybe
determined by 0.002 strain offset)
 Ultimate Tensile Strength σUTS
 Maximum stress that can be sustained by a structure in tension
 Fracture Strength σF
 The level of stress at which fracture or break down of material takes place
 Elastic Modulus
 Ratio of Engineering stress over Engineering stain under uniaxial tensile
loading
 E= σ/ ε.

7. Important definitions
 Yielding
 The phenomenon of elastic-plastic transition is called yielding
 Proportional Limit
 The region of stress-strain curve where Hooke’s law is obeyed.
 Ductility
 It is a measure of the degree of plastic deformation that has been
sustained at fracture.
 %Elongation
 %E= (Lf-L0)/L0 × 100
 %Area Reduction:
 %R= (A0-Af)/A0 × 100

8. Modes Of Deformation
 Linear Elastic Deformation
 Non-Linear Elastic Deformation

9. Modes Of Deformation
 Plastic Deformation

10. Ductile vs. Brittle
materials

11. LAB ACTIVITY
 Demonstration of tension test on different
materials
 Collection and analysis of the data
 Comparison of different parameters
 Lab report submission