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7/29/2019 5. Mechanical Testing
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TWICSWIP 3.1
WIS 5WELDING INSPECTION
DESTRUCTIVE TESTS
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Destructive tests
Involve the destruction of a welded unit or
selected specimens cut out from the weld
Destructive tests include:tensile test
bend test
impact test
hardness test
metallographic examination
creep test, etc.
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Tensile test
Objective:
measuring the overall strength of the weld jointInformations to be supplied on the test report:material type
specimen type
specimen size
(see QW-462.1)
UTS
location of finalrupture
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Bending test
Objectives:check if lack of fusion type of defects are present
assessing ductility of the weld jointInformations to be supplied on the test report:
material type
specimen type and
orientation (see QW-462.2;3)
bend radius/angle
test result (pass/fail)
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Bending test
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Charpy V-notch impact test
Objectives:measuring impact strength in differentweld joint area
assessing resistance toward brittle fractureInformations to be supplied on the test report:material type
notch type
specimen size
test temperature
notch location
impact strength value
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Charpy V-notch impact test specimen
55 mm
==
2 mm
10 mm
10 mm
45
R 0,25 mm
Specimen dimensions acc. ASTM E23
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Charpy impact test Pendulum (striker)
Specimen
Anvil (support)
Charpy V-notch impact test
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h2
h1
Charpy V-notch impact test
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To define the type of failure, we can alsomeasure:
amount of crystalinity
Charpy V-notch impact test
lateral expansion
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Charpy V-notch impact test
Testing temperature
Joulesabsorbed
DuctileFracture
47 Joules
28 Joules
TransitionZone
Transition Temperature Range
Mn < 1.6 % increases
toughness in steels*
BrittleFracture
Three specimens are normallytested at each temperature.
-40 -30 -20 -10 0 +10 +20 +30 + 40
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Hardness
Definition - is the resistance of amaterial against penetration
Hardness tests: Brinell
Vickers
Rockwell
It is measured by indentation by apenetrator under a constant load
Between UTS and hardness is a directcorrelation
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Hardness test
Objectives:measuring hardness in different areas of aweld joint
assessing resistance toward brittle fracture,
cold cracking and corrosion sensitivity in H2S
Informations to be supplied on the test report:material type
location of indentation
type of hardness test and load applied on theindenter
hardness value
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Weld joint hardness test
Vickers hardness tests:
d = (d1+ d2)/2d2
d1
indentation body is a square based diamondpyramid (136 included angle)
the average diagonal (d) of the impression
is converted to a hardness number from atable
it is measured in HV5, HV10 or HV025
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Vickers hardness test
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Metallographic examination
Macro examination Micro examination
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Metallographic examination
Objectives:detecting weld defects (macro)
measuring grain size (micro)
detecting brittle structures, precipitates, etc
assessing resistance toward brittle fracture,cold cracking and corrosion sensitivity
Informations to be supplied on the test report:material type
etching solution
magnification
grain size
location of examined area
weld imperfections(macro)
phase, constituents,
precipitates (micro)
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Hydrostatic test
Is a test for leakage under pressureVessel configuration:
the test should be done after any stress
relief components that will not stand the pressure
test (e.g. flexible pipes, diaphragms) mustbe removed
the ambient temperature MUST be above0C (preferably 1520C)
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Hydrostatic test procedure
blank off all openings with solid flanges use correct nuts and bolts, NOT G clamps
two pressure gauges on independenttapping points should be used
for safety purposes bleed all the air out
pumping should be done slowly (nodynamic pressure stresses)
test pressure - see relevant standards (PD5500, ASME VIII). Usually 150% designpressure
hold the pressure for minimum 30 minutes
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Hydrostatic test - what to look for
leaks (check particularly around seamsand nozzle welds!)
dry off any condensation with a
compressed air-line watch the gauges for pressure drop
check for distortion of flange faces, etc