Mechanical
Testing
Mechanical Testing of welded joints may be carried out for the
Following reasons
• Welding Procedure approval
• Welder Approval
• Production Quality Approval
Welding consumables manufacturers will carry out all weld met
tests for each consumable type
Parent Material is normally subjected to extensive testing prier t
Its acceptance
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Mechanical Testing
In mechanical Testing representative test samples produced und
similar conditions to the in service components are normally us
and comparison is made
The main purpose of mechanical Testing is to asses the
properties
of welded Joints
The most frequently used mechanical
tests are
Tensile
Bend
Nick Break
Fracture
Impact
Hardness
Macroscopic / Microscopic
CTOD 3 2
Tensile Test
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Tensile Test
In tensile test stress is applied in opposite direction to
pull the
two ends apart
Tensile test is used to asses the following
• Yield point of the specimen
• The ultimate tensile strength
• Ductility of the specimen, expressed as % elongation
The different types of tensile test are
• Transverse tensile test
• All weld tensile test
• Cruciform Test
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Tensile Test
The reduction in the cross sectional area indicates the ductile fra
Steel specimen which do not exhibit any necking usually rejected
U.T.S = Maximum Load Applied / least cross sectional area
% elongation( strain ) = Increase of gauge length x 100 / original le
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Bend Test
The bend test is carried out to determine the soundness of the
weld zone
The commonly applied bend test is the transverse bend test
There are three ways to perform this type of bend test
• The root bend test
• Face bend test
• Side bend test
The specimen width of bend test is usually at least 1.5 times
the thickness and the weld reinforcement is usually dressed flush
On both sides
The specimen are usually bent through 90o,120o , 135o and , 180o
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Bend Test
The diameter of the Firmer is typically four times the specimen thickness
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Impact Test
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Impact Test
Impact test is performed to
Asses notch toughness by
measuring the energy absorbed
During the impact
Two main impact tests are
• Charpy v-notch
• Izod Test
• Both tests use a swinging Pendulum
• The pendulum hits the notched Specimen positioned in the
Machine
• The specimen immediately fractures in the notch
• More energy is absorbed by tougher specimen during the
fracture 3 9
Hardness Test
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Harness Test
This test is used to know the hardness gradient across the
weld zone and parent material for comparison purpose
Hardness of the weld and HAZ will give an indication of the
Weldability of the material
Hardness also gives the idea about the correct selection of
welding Parameters
Two common hardness tests are
• Vickers Pyramid Hardness Test
• Brinnell Hardness Test
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Hardness Test
Vickers Hardness Test:
The test uses small pyramid shaped diamond indenter
with an angle of 136o
A force is applied to press the indenter into the surface
for
10-15 seconds
The force applied is variable from 1-120 kg
The diamond indenter leaves a pin tip sized square
indentation on the surface
The size of this indentation is the indication of hardness
of the specimen 3 12
Hardness Test
Brinell Hardness Test
The test is carried out by forcing the hardened 10 mm dia
steel ball into the surface of the specimen
The force used is 500,1500,or 3000 kg for 15 seconds
An in built microscope with a calibrated lens is used to
Measure the width of indentation.
The size of this indentation is the indication of hardness of
the specimen
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Nick Break Test
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Nick break test
Nick break test is used to evaluate the presence of
weld defects across the fractured surface
Two nicks are cut each on either side of the of the weld
The test specimen are broken by bending or striking with hamm
This causes the weld to fracture along the weakest setion
The fractured faces are then examined visualy
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Fillet Weld Fracture Test
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Fillet Weld Fracture Test
• To evaluate the presence of weld defects across the
fractured
surface
• A saw cut is made along the center line of the weld face on
a fillet
weld
• The specimen is broken by hammer strikes
•
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CTOD
• This test is to determine metals resistance to initiate the crack
from any notch
• A notch is cut in the specimen, The specimen is subjected to
high
speed cyclic load to induce a crack at the root of the notch
• Then study three point bending force is applied to open this
crack
• A clip gauge is fixed to the mouth of the notch to accurately
measure
the rate of crack opening 3 18
