1. Forging new generations of engineers
Tensile Testing
Principles of EngineeringTM
Lesson 6.5 – Material Testing
Forging new generations of engineers
Project Lead The Way, Inc.
Copyright 2007

2. Tensile Testing
The following MATERIAL PROPERTIES can be evaluated / determined by TENSILE TESTING:
STRENGTH
DUCTILITY
ELASTICITY
STIFFNESS

3. Material Properties
STRENGTH - the greatest stress that the material can withstand prior to failure.
DUCTILITY - a material property that allows it to undergo considerable plastic deformation under a load before failure.
ELASTICITY - a material property that allows it to retain its original dimensions after removal of a deforming load.
STIFFNESS - a material property that allows a material to withstand high stress without great strain.

4. The Tensile Tester
A machine which applies a tensile force (a force applied in opposite directions) to the specimen, and then measures that force and also the elongation:
This machine usually uses a hydraulic cylinder to create the force. The applied force is determined by system pressure, which can be accurately measured.

5. = 0.6N/mm2 x 1962.25mm2 =1177.35 N The Tensile Tester
Applied Force is hydraulic pressure times the area of the cylinder’s piston.
F = PRESSURE x AREA
= 0.6N/mm2 x mm2
= N

6. Tensile Tester
Data Acquisition Unit

10. Stress - Strain Curve

11. THE SAMPLE
Area of measured test

12. This establishes the original length.
Marking the sample:
A precision punch with two points exactly 2.000” apart is used to mark the sample in the tested region.
This establishes the original length.

13. This device, called an EXTENSOMETER, measures the distance between the two prongs very precisely while the test is in progress.

14. Before
After

15. A Stainless Steel sample is loaded in the tester.

18. Terms
Necking: The localized decrease in diameter in a specimen near the rupture point.
Elastic Deformation Region: The area of a stress - strain curve where the specimen will deform under load, yet return to its original shape when the load is removed.
Plastic Deformation: Deformation that occurs once the object has been stressed past its elastic limit. The deformation is no longer reversible.

19. Tensile Testing
Principles of EngineeringTM
Lesson 6.5 – Material Testing
Necking
“Necking” occurs as the sample leaves the elastic deformation region and begins to deform plastically.
Project Lead The Way, Inc.
Copyright 2007

21. The classic cup & cone shape of a fairly ductile tensile fracture is visible here.

22. Upon completion of the test, the sample is reassembled and final measurements for total elongation and minimum diameter are made using a vernier caliper.

25. For maximum precision, the points of the vernier caliper must be placed exactly at the center of the marks made by the punch prior to the test.

26. Compare the material properties of these three metal samples.
All three failed under tension

27. PLASTIC DEFORMATION REGION
ELASTIC DEFORMATION REGION

28. The point of departure from the elastic deformation region is known as the “yield point.”
In the elastic region, the slope of this line is the material’s Modulus of Elasticity.

29. Stress - Strain Plot