Brittle Coating Methods

BY

DEEPAK. ROTTI

Introduction: Naturally occurring brittle patterns.

Coating externally.

Nature and implications.

Advantages of brittle coating method are:

It provides nearly the whole field data for both magnitude

and direction of principal stresses.

It does not require a model and be applied to prototype of

the required component.

The data obtained can be converted to stresses in a simple

fashion and complex mathematical analysis is not required.

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Types of brittle coatings: Resign based coating (stress coat): 1/3rd zinc resin ate + 2/3rd.

carbon + di-butylphthalate.

Thickness 0.1-0.15mm ; sensitivity 0.003-0.003m ; temp 600c.

Ceramic based coating (all temp): Finely ground ceramic

particles suspended in a solvent + drying + heated up to 5400c.

Thickness 0.1-0.15mm ; sensitivity 0.002-0.002m ; temp

3700c.

Tens.Lac Brittle Lacquer: high sensitivity, non-flammable,

odorless, and of low toxicity brittle lacquer.

Thickness 0.075mm ; sensitivity 500u cm/cm ; temp 1000c.

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Steps followed for brittle

coating:

Select the type of coating material.

Clean the surface of the specimen under consideration.

Provide an undercoat to provide better reflective characters.

Application of base coat and allowed to dry for 24 hours.

Testing of specimen.

Detection and Analysis of crack patterns.

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Cracks formed : 5

6. References:

Experimental stress analysis by ‘James dally and

William riley’.

Fracture modes in brittle coatings with large

interlayer modulus mismatch by Sataporn

Wuttiphan.

Principle of stress coat in brittle coating by ‘Herzl

Chai and Brian Lawn’.

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Thank you........xyz

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esa

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