Application of Diffraction in Aerospace
Transcript of Application of Diffraction in Aerospace
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APPLICATION OF DIFFRACTION IN
AEROSPACE
Presentation by:-
Condra Krishnakant & Viraj Bhist
(B.Tech Aerospace)
Roll No. 8 & 27
SAP ID:- 500017287 & 500016368
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RESIDUAL STRESS
The residual risk is the risk or danger of anaction or an event, a method or a (technical)process that, although being abreast with
science, still conceives these dangers, even
if all theoretically possible safety measures
would be applied (scientifically conceivable
measures).
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The Importance of CharacterizingResidual Stress
DistortionSCC (Stress corrosion cracking)
HIC (Hydrogen Initiated Cracking)
Crack initiation
Crack propagation
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Benefits of Measuring & Monitoring ResidualStress: Validate numerical models, shorten design cycle, utilize full materialcapability. Optimize production/process parameters, eliminate abusivemachining, reduce production costs. Extend component or structure life. Validate repair area restoration to original specification. Substantiate supplier quality. Improve product quality. Improved safety, reduce warranty/liability issues. Reduce or eliminate catastrophic failures (examples: landing gears,burst disks due to LCF). Better predictions of replacement part requirements. Enhance existing NDE technologies.
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DIFFRACTION
When light falls on obstacles or small
apertures whose size is comparable with the
wavelength of light ,there is a departure from
straight line propagation,the light bends
round the corners of the obstacles or
apertures and enters in the geometrical
shadow. This bending of light is called
diffraction.
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X RAY DIFFRACTION
X-ray scattering techniques are a family ofnon-destructive analytical techniques which
reveal information about
the crystallographic structure, chemicalcomposition, and physical properties of materialsand thin films. These techniques are based on
observing the scattered density of an X-
ray beam hitting a sample as a function ofincident and scattered angle, polarization, andwavelength or energy
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Advantages of the X-ray Diffraction Method Measures Total Stress = (Residual + Applied) stress Quantitative data can be obtained from real parts.
Nondestructive - Re-measure the same locations over
time to track changes.
Fast measurements can be obtained in seconds. Field proven: can be used inline at depot or on actual
structure.
Highest spatial resolution for surface stress gradients and
surface discontinuities
Can be used to measure gradients normal to the surface -
partially destructive
Only method that accurately measures surface and near
surface residual sresses.
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Surface Bending - Stress Mapping
Compressivestresses shown in
blue
Tensile stresses
shown in red
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COMPRESSIVE STRESS
Compressive stress is
the stress on materials that leads to asmaller volume.
By compressive stress the material is
under compression. Compressive stressto bars, columns, etc. leads to shortening.
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TENSILE STRESS
The maximum stress that a material can
withstand while being stretched or pulledbefore necking, which is when the
specimen's cross section starts to
significantly contract. Tensile strength is the
opposite of compressive stress and the
values can be quite different.
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How X-ray Diffraction works. Soft x-rays
constructively
interfere with the
crystals in the
material The diffraction
coneangle varies with
change in d tostrain as per
Braggs Law:=2d sin
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Technique Limitations Works on crystalline materials
only.
Requires Line of Sight access to
measurement surface.
Galvanizing or paint, if present,
must be locally removed.
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Application in aerospace
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C-141 Frame
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Residual Stress
Map of
998 FrameRed regions
have tensile
stresses and
could be
more
susceptible to
SCC.
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C-141 Frame
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C-141 Fuselage Frame FS 998
Measuring residual stress inside mainlanding gear trunnion 6 I.D.A typical display of Proto mappingresidual stresses on internal surfaceof MLG trunnion.
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The great obstacle to progress is
not ignorance, but the illusion of
knowledge.
-Daniel Boorstin (1915-2004)
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Biblography
Michael Brauss
President
Proto Mfg. Ltd. Oldcastle, ON Canada
Proto Mfg. Inc. Ypsilanti, MI USA
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THANKYOU