INSPECTION OF CASTINGS

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INSPECTION OF CASTINGS

• SEVERAL METHODS
• VISUAL
• OPTICAL
• - FOR SURFACE DEFECTS
• SUBSURFACE AND INTERNAL DEFECTS THROUGH NDTs
  DTs
• PRESSURE TIGHTNESS OF VALVES BY SEALING THE
  OPENING AND PRESSURISING WITH WATER

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CASTING DEFECTS

• SURFACE
• METALLIC PROJECTION (4)
• DEFECTIVE SURFACE (11)
• CHANGE IN DIMENSION- WARP
• INCOMPLETE CASTING
• MISRUN, RUNOUT
• CAVITY-
• BLOWHOLES, SHRINKAGE
• PINHOLES
• DISCONTINUITY
• HOT CRACK
• COLD SHUT, COLD CRACK

• SUBSURFACE
• SUBSURFACE CAVITY
• INCLUSIONS
• DISCONTINUITY

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NDTs

• Methods of testing
• Destructive-
• Non destructive-
• Radiagraphic
• Ultrasonic

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• Non Destructive Testing
• with Ultrasonics
• for flaw Detection in Castings,
• Weldments, Rails, Forged Components etc.

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ULTRASONIC TESTING
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Why Ultrasonics ?

• Flaw detection in metals and nonmetals
• Flaw measurement in very thick materials
• Internal and surface flaws can be detected
• Inspection costs are relatively low.
• Rapid testing capabilities and portability.

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Ultrasonic waves are simply vibrational waves
having a frequency higher than the hearing range
of the normal human ear, which is typically
considered to be 20,000 cycles per second (Hz).
The upper end of the range is not well defined.
Frequencies higher than 10 GHz have been
generated. However, most practical ultrasonic
flaw detection is accomplished with frequencies
from 200 kHz to 20 MHz, with 50 MHz used in
material property investigations. Ultrasonic
energy can be used in materials and structures
for flaw detection and material property
determinations.
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• Ultrasonic waves are mechanical waves (in
  contrast to, for example, light or x-rays, which
  are electromagnetic waves) that consist of
  oscillations or vibrations of the atomic or
  molecular particles of a substance about the
  equilibrium positions of these particles.
  Ultrasonic waves behave essentially the same as
  audible sound waves. They can propagate in an
  elastic medium, which can be solid, liquid, or
  gaseous, but not in a vacuum.

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In solids, the particles can (a) oscillate along
the direction of sound propagation as
longitudinal waves, or (b) the oscillations can
be perpendicular to the direction of sound waves
as transverse waves.   At surfaces and
interfaces, various types of elliptical or
complex vibrations of the particles occur.
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THEORY OF TESTING
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MACHINE SPECIFICATIONS

• Make
• Weight
• Calibration range upto 9999 mm.
• Choice of Frequency range
• Provision for adjusting gain.
• Documentation possibility via printer
• Limitation.

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Probe
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SCANNING TECHNIQUES

• Pulse Echo method
• Straight beam method
• Angle beam method

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PULSE ECHO METHOD
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Inspection of

• Gas porosity
• Slag Entrapment
• Cracks

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With the exception of single gas pores all the
defects listed are usually well detectable by
ultrasonics.     Ultrasonic flaw detection has
long been the preferred method for nondestructive
testing , mainly in welding applications.   This
safe, accurate and simple technique has pushed
ultrasonics to the forefront of inspection
technology.
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The proper scanning area for the weld First
calculate the location of the sound beam in the
test material.   Using the refracted angle, beam
index point and material thickness, the V-path
and skip distance of the sound beam is found.  
Then identify the transducer locations on the
surface of the material corresponding to the
crown, sidewall, and root of the weld.
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Inspectionof Rails
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• New trend
• Ultrasonic Simulation - UTSIM
• UTSIM is a user interface integrating a CAD model
  representing a part under inspection and an
  ultrasound beam model.

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Ultrasonic sizing of small flaws with the
distance-amplitude-correction (dac) curve