Transcript Course Name

Manufacturing Processes Lab I, MET 1321
Inspection and Testing Welds
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Learning Objectives
Describe the difference between a welding flaw and a
welding defect.
List the most common types of nondestructive and
destructive testing done on welds.
Perform several basic types of tests on welds to
evaluate weld quality.
Describe the methods used to prepare samples for
bend tests.
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Reasons for inspecting welds
Most welds have flaws in them
A flaw is a part of a weld that is not perfect.
Some flaws are so small they can be found only under a
microscope.
Other ones are easily seen, which include porosity and large
cracks.
A defect is a flaw that makes a a weld unusable for the job
it is intended to perform (eg. Cracks when welding on a
gas pipeline)
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Inspecting welds
Welds must be inspected to detect flaws. Then, the flaws must
be evaluated to decide if they are acceptable or if they are
defects.
Most welding is done to requirements of a code or specification.
The code or specification determines how large a flaw can be
before it becomes a defect.
A visual inspection is useful to determine the size of a
weld, to check for undercut, overlap, and other
surface flaws, and to check travel speed, arc length,
and depth of penetration.
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Weld tests
Nondestructive
NON-destructive
Examinations (NDE),
does not damage the
weld or the base metal.
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Weld
tests
Destructive
Destructive test results
in at least some damage
to the weld.
Nondestructive
Examinations (NDE)
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Nondestructive Examinations (NDE)
Liquid penetrant inspections,
Magnetic particle inspections,
Ultrasonic inspections,
X-ray inspections,
Eddy current inspections and
Air pressure/water pressure leak tests.
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Liquid penetrant inspections
In a liquid penetrant inspection, a dye is applied to the weld. After
a few minutes, the dye is cleaned from the weld and a developer
is applied. Any dye trapped in a flaw is developed, revealing the
location of the flaw.
Liquid penetrant inspections are useful for
detecting surface flaws, but cannot detect flaws
inside the weld!
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Magnetic particle inspections
To examine a part using magnetic particle inspection, the surface
must first be cleaned. Then, fine magnetic particles are applied
to the surface. Then a strong magnetic field is applied. The fine
magnetic particles are drawn toward any flaw at the surface or
very near the surface of the part.
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Ultrasonic inspections
Ultrasonic inspection can be
used on all metals and can
locate internal flaws.
Sound waves are sent into the
part being inspected.
The waves travel to the far
side of the metal and bounce
back.
Any flaws within the weld are
indicated on an oscilloscope.
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
X-ray inspections
In an X-ray inspection, film is placed on one side of the part to be
inspected.
X rays pass through the part and expose the film.
After the film is developed, any flaw or defect in the weld can be
observed.
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Eddy current inspections
Eddy current inspection detects porosity, cracks, slag inclusions, and lack
of fusion at or near the surface of a weld by including eddy currents in
the part and monitoring changes in current flow on an oscilloscope.
Eddy currents are AC currents, usually of high
frequency, which can be induced to flow in any
metallic section, their flow pattern being disturbed
by the presence of cracks or other discontinuities.
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Air pressure leak tests
Air-pressure or water pressure leak tests are often used to inspect
pipes or tanks that are to contain gases or liquids under pressure.
In an air-pressure leak test, a soapy solution is applied to the
pipe surface at each weld. When the pipe is under air
pressure, flaw will cause bubbles to form.
When water pressure is used, water will spray out from the
pipe where there is a leak.
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Destructive Examinations (DE)
Tensile test,
Bend test,
Fillet test,
Hardness test,
Impact test,
Peel test (for spot welds),
Tensile shear test (for spot welds),
Pressure test.
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Tensile test
A tensile test is a destructive test in which a tensile
(stretching or pulling) load is applied to a prepared
sample until the sample breaks.
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Tensile Strength and Ductility
Tensile strength=
Maximum force applied by machine
Cross-sectional area of sample
F
o
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Ductility
Ductility=
Distance between
points after test –
distance before test
distance before test
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
x 100
Example
A 2 inch welded plate is ½” (12.7 m) thick. The reduced section is 1 ½” (38
mm) wide. A maximum force of 48000 pounds (213500 Newtons) is
required to break the sample. The distance between the two points after
breaking is 2 ½” (63.5 mm). Find the tensile strength and ductility of this
sample.
Tensile strength=
Maximum force applied by machine
=
Cross-sectional area of sample
48000
½x1½
= 64000 psi
= 442 MPa
Ductility=
Distance between
points after test –
distance before test
distance before test
x 100=
(2 ½” -2”)
2”
x 100= 25%
The same value in metric
system.
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Bend test
Specimen is positioned between two supports, and a load is applied at
its center.
Bend tests are used to evaluate the quality and ductility of a completed
weld.
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Bend test
In a guided bend test, the size or radius of the bend is controlled.
Click on image to see the video clip
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Bend test
In a free bend test, the sample is placed into a large, strong vise and
struck with a hammer until it bends to a 90˚ angle. It is then
hammered in the opposite direction to a 90˚ angle. This back and
forth bending continues until the weld sample breaks.
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Fillet test
In a fillet test, force is applied to the welded
joint until it breaks or until the vertical piece
is bent flat against the horizontal piece.
The weld should break along its centerline.
A weld that breaks
along the toe may
indicate a lack of
fusion.
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Hardness test
Hardness tests are used to measure a material’s resistance to scratching
and indentation.
To determine the hardness of a metal, an indenter is pressed into the
metal by a known force. The depth of indentation indicates the hardness of
the metal.
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Other destructive tests
Impact resistance test
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
Other destructive tests
Peel test (for spot welds)
Tensile shear test (for spot welds)
Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri
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Manufacturing Processes Lab 1 (MET 1321)
Dr Simin Nasseri