This presentation is for mechanical engineering/ civil engineering students to help them understand the different type of destructive mechanical testing of materials. The tensile testing, hardness, impact test procedures are explained in detail.

1. MATERIAL TESTING
DESTRUCTIVE/
MECHANICAL TESTS
JJ TECHNICAL SOLUTIONS
(www.mechieprojects.com)

2. CONTENTS
• INTRODUCTION
• TENSILE TESTING
• HARDNESS TESTING
• IMPACT TESTING
• CREEP AND FATIGUE TESTING

3. Why materials testing is required ?
• To test mechanical properties like UTS, YS, % elongation etc.
which is used as a design input.
• Make informed choices in using raw materials.
• To check properties of material after heat treatment.
• To check material property after welding/ brazing etc.
• Ensure batch and production quality
• As part of maintenance and to prevent failure in usage
Factor of Safety is the ratio comparing the actual stress on a material and the safe useable stress.

4. Two types of material testing!!!
• Destructive Testing/Mechanical Tests –
• The material may be physically tested to destruction or indentation.
• To measure the strength, hardness, toughness, etc.
• Example: Tensile testing, Impact testing, Hardness Testing etc.
• Non-Destructive Tests (NDT)
• Samples or finished articles are tested before being used and as
routine maintenance checks.
• Example: Radiography, Dye Penetration tests etc.

5. Tensile Testing
• Is done on a Universal Testing Machine (UTM)
• Uses a load cell and an extensiometer to apply measured force
to an test specimen and %age elongation respectively .
• The load v/s elongation is then plotted and studied
• Variables such as strain, stress, elasticity, tensile strength,
ductility and shear strength are measured and computed.
• Test specimens can be round or flat.
• Standard for Tensile testing: ASTM A370
(Standard: ASTM A370; ASTM B557; ASTM E8; Shore: ISO6892-1; EN2002-1)

6.  STRENGTH
 DUCTILITY
 ELASTICITY
 STIFFNESS
 MALLEABILTY
 MODULUS of TOUGHNESS
 MODULUS of RESILIENCE Tensile Test Equipment – UTM

7. 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.

8. HYDRAULIC UNIVERSAL TESTING MACHINE
• A universal testing machine (UTM), also known as a universal tester, materials testing machine or materials test frame,
is used to test the tensile stress and compressive strength of materials . It is named after the fact that it can perform many
standard tensile and compression tests on materials, components, and structures.

9.  Round Specimens: Forgings, Plates (t>20) etc
 Flat specimens: Sheets (t<20), rubber, ceramics etc.
 Standard specimen sizes available in ASTM A370/ IS 1608 standard
 Major Test variables:
Specimen size
Strain rate- Different for metals, rubbers, ceramics etc

10. Specimen Nomenclature
 Tensile testing at room temperature
 Tensile testing at elevated temperature
 Tensile testing
 Fasteners
 Forgings
 Plates/ Sheets
 Tubes/ bars
 Polymers/ rubber etc

11. Tensile Test Results
 Cup and cone fracture signifies a ductile material
 A shear fracture indicates a brittle material
Brittle Ductile Very
Ductile
(Ductile)

12. Glass
(Brittle)
Ductile
M.S. -Ductile
Aluminium
Rubber
High Carbon Steel

13. Youngs Modulus (E)

14. Proof Stress for Load – Extension graph
Proof Stress for Stress – Strain graph
Proof Stress
 Sometimes the stress strain graph doesn’t
has a distinctive Yield Point
 For such material yield point is defined
using load corresponding to 0.1% or
0.2% proof stress
 The stress that causes a % increase in
gauge length.
 It can be found by drawing a line parallel
to the straight part of the graph.
 A value can be taken from the vertical
axis.

15. HARDNESS TESTING
(Standard: Brinell:ASTM E10; Rockwell: ASTM E18; Vickers: ASTME384; Shore: ASTM E2240)
Hardness is the ability to withstand indentation or scratches
Hardness measurement is also used to check response to heat
treatment of a particular materials
Types of Hardness Measurement
 Scratch Hardness: Uses Mohs Scale
 Indentation Hardness
 Brinell/Rockwell/ Vickers: For Metals
 Shore: Rubber, Polymers
 Rebound Hardness: Uses Scleroscope

16. Hardness Testing Machine
• The indenter is
pressed into the
metal
• Softer materials
leave a deeper
indentation

17. Brinell Hardness Test (BHN)
• Uses spherical shaped indentor.
• Cannot be used for thin materials.
Used for large components
• Ball may deform on very hard
materials. Used on softer material
• Surface area of indentation is
measured.
Spherical indenter is shot with desired load
force at the target
The diameter of the indentation caused is
recorded
The diameter of the indentation tells about
the Brinell Hardness Number (BHN)

18. Rockwell Hardness Tests (HRC)
• Gives direct reading.
• Rockwell B (ball) used for soft
materials.
• Rockwell C (cone) uses diamond
cone for hard materials.
• Flexible, quick and easy to use.
• Used on forgings, castings etc. BHN = HRC × 10 (approximately)

19. Vickers Hardness Test (HV)
• Measures Small Samples
• Uses square shaped pyramid
indenter.
• Accurate results.
• Measures length of diagonal on
indentation.
• Usually used on very hard
materials and for surface hardness
measurement

20. Impact Tests
• Impact test determines material toughness.
• Measure an objects ability to resist high-rate loading
• The impact strength of a material in the presence of a flaw
or notch and fast loading conditions is determined.
• The amount of energy absorbed by a material before
fracture, is determined.
• Impact test:
• Charpy Impact Test
• Izod Impact Test
(Standard: ASTM A370/ ASTM E23/EN 100045-1/ ISO 148)

21. Impact Tests
Types of Notch Specimens
Impact Test –Equipment
Izod v/s Charpy Tests
• Charpy Test
• Izod Test
• Types of Notch specimens
• V notch
• U notch
• Keyhole notch

22. Izod Impact Test
• Strikes from a height at =167 Joules.
• Test specimen is held vertically.
• Notch faces striker.
• Strikes form higher position with 300 Joules.
• Test specimen is held horizontally.
• Notch faces away from striker.
Charpy Impact Test
Izod v/s Charpy

23. Creep
 The elongation of a material due to
constant high load at constant higher
temperature is called creep.
 Problems with creep increase when the
materials are subject to high
temperature or the materials themselves
have low melting points such as lead.
Creep can cause materials to fail at a
stress well below there tensile strength.
 During Creep testing, the tensile
specimen is subjected to sufficiently
high load and temperature, to produce a
time-dependent inelastic strain
 The strain in the specimen varies with
time .
 For an appropriate constant stress and
elevated temperature, a strain-time plot
( creep curve is plotted
(Standard: ASTM 1983/ BIS 1987/ ISO 1987)
Creep Curve
Creep Test Methodology

24. Fatigue
 Fatigue is due to the repeated loading
and unloading.
 When a material is subjected to a
force acting in different directions at
different times it can cause cracking.
In time this causes the material to fail
at a load that is much less than its
tensile strength, this is fatigue failure.
Vibration for example is a serious
cause of fatigue failure.
 Fatigue can be prevented with good
design practice.
1. A smooth surface finish reduces the
chance of surface cracking.
2. Sharp corners should be avoided.
3. Corrosion should be avoided as this
can cause fatigue cracks.
(Standard: ASTM D7791/ ASTMF218/ ISO/TC 164)

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26. This is purely an academic work and has no financial or other
interest.
The authors are acknowledge the various reference sources and
are grateful to all the people and firms who’s sources have been
used
The results achieved in this should be independently verified.