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*Unit 1part-II

*INTRODUCTION TO NDT-CONTINUED…

*By:Zoha NasirAssistant professorJIT, Barabanki

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*QUALITY

It Is Degree Of Satisfaction.It shows the capability of a material to perform

desired operationQuality control charts are used in maintaining the

quality of material.

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*Defects

It is defined as any departure or discontinuity in structure from specified requirements.

It reduces the service life of the part.

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*Some common defects.

CracksSurface defects:1.undercut 2.oxidation 3.Incomplete penetrationBlow holesPorositySlagsIncomplete fusion

05/03/2023 Jahangirabad institute of technology 5*Visual Inspection

Visual inspection can be enhanced by looking at the suspect area with a bright light, a magnifying glass, and a mirror (when required).

Some defects might be so obvious that further inspection methods are not required.

The lack of visible defects does not necessarily mean further inspection is unnecessary.

Some defects may lie beneath the surface or may be so small that the human eye, even with the assistance of a magnifying glass, cannot detect them.

05/03/2023 Jahangirabad institute of technology 6*Borescope

Inspection by use of a borescope is essentially a visual inspection. A borescope is a device that enables the inspector to see inside

areas that could not otherwise be inspected without disassembly. An example of an area that can be inspected with a borescope is

the inside of a reciprocating engine cylinder. The borescope can be inserted into an open spark plug hole to

detect damaged pistons, cylinder walls, or valves. Another example would be the hot section of a turbine engine to

which access could be gained through the hole of a removed igniter or removed access plugs specifically installed for inspection purposes.

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Borescopes are available in two basic configurations.The simpler of the two is a rigid type of small diameter

telescope with a tiny mirror at the end that enables the user to see around corners.

The other type uses fiber optics that enables greater flexibility. Many borescopes provide images that can be displayed on a

computer or video monitor for better interpretation of what is being viewed and to record images for future reference.

Most borescopes also include a light to illuminate the area being viewed.

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*Accoustic Emmision Testing.

Acoustic emission is an NDI technique that involves the placing of acoustic emission sensors at various locations on an aircraft structure and then applying a load or stress.

The materials emit sound and stress waves that take the form of ultrasonic pulses. Cracks and areas of corrosion in the stressed airframe structure emit sound waves which are registered by the sensors.

These acoustic emission bursts can be used to locate flaws and to evaluate their rate of growth as a function of applied stress.

Acoustic emission testing has an advantage over other NDI methods in that it can detect and locate all of the activated flaws in a structure in one test.

Because of the complexity of aircraft structures, application of acoustic emission testing to aircraft has required a new level of sophistication in testing technique and data interpretation.

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* Applications

VI technique is used to detect:Corrosion and erosion in metals.Weld which have discontinuity on the surface.Cracks.Fractures.Leakages.Misalignment of parts etc.