Application of Diffraction in Aerospace

8/4/2019 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

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Application of Diffraction in Aerospace