NDT of Materials

NDT of materials (Nondestructive Testing of Materials)

Prepared by/Mohammed abd el- ghani 1st I.E.D.

Prepared for/Dr/ Masoud Ibrahim

Fayoum UniversityFaculty Of Engineering

Department Of Industrial Engineering

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1 .Definition:

→Nondestructive testing (NDT)→ Nondestructive examination (NDE) → Nondestructive inspection (NDI)

►Is testing that does not destroy the test object, To detect different defects such as cracking and corrosion

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2 .The need for NDT: many industrial components need regular nondestructive tests to detect damage that may be difficult or expensive to find by everyday methods. For example:

→Aircraft skins need regular checking to detect cracks.→ Pressure vessels may develop cracks in welds.→ Underground pipelines are subject to corrosion and stress corosion cracking.→ And in a lot of industrial and structure applications.

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3 .Applications: AutomotiveEngine parts, Frame.Aviation /

AerospaceAirframes , Spaceframes , Propellers ,

Reciprocating Engines, Gas Turbine Engines , Rocketry.

ConstructionStructures , Bridges.ManufacturingMachine parts, Castings and Forgings. Industrial plantsPressure vessels ,Storage

tanks ,Welds ,Boilers ,Heat exchangers ,Turbine bores ,In-plant Piping.

MiscellaneousPipelines , Railways , Tubular NDT, for Tubing material, Corrosion Under Insulation (CUI) ,Amusement park rides, Submarines and other Naval warships.

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4 .Methods and techniques:

1 .Visual Testing.2. Dye penetrant inspection.3. Magnetic Particle Inspection.4. Ultrasonic testing.5. Radiographic (X-ray) testing.

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1 .Visual Testing:

Most widely used. Typical tools for VT consist of: →Magnifying glasses. → Flashlights.

→ Tape measures or calipers.

Experience of the inspector is important.

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2 .Dye penetrant inspection:

►Principles:

→adequate penetration time has been allowed.→ the excess penetrant is removed.→ a developer is applied. → the developer helps to draw penetrant out of the flaw.

→ a visible indication becomes visible to the inspector.

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►Materials:

►Visible penetrants are typically red in color, and represent the lowest sensitivity.

►Fluorescent penetrants contain two or more dyes that fluoresce when excited by ultraviolet (UV-A) radiation (also known as black light)It is performed in a darkened environment.It is more sensitive to small defects

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►Inspection Steps:

1 .Pre-cleaning.2 .Application of Penetrant.

3 .Excess Penetrant Removal 4 .Application of Developer.

5 .Inspection 6 .Post Cleaning

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1 .Section of material with a surface-breaking crack that is not visible to the naked eye.

2. Penetrant is applied to the surface.

3. Excess penetrant is removed.

4. Developer is applied, rendering the crack visible

►Inspection Steps: “Cont”.

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►Features:

1 (The flaws are more visible, because: a- The defect indication has a high visual contrast. b- The developer draws the penetrant out of the flaw.

2 (Limited training is required for the operator .3 (Low testing costs.

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3 .Magnetic Particle Inspection:

It is to generate magnetic flux in the article to be examined with the flux lines running along the surface the flux lines approach a discontinuity they will stray

out into the air at the mouth of the crack.

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►Inspection Steps:

1 .Component pre-cleaning.2 .Introduction of magnetic field.

3 .Application of magnetic media.4 .Interpretation of magnetic particle

indications.

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►Inspection Steps: “Cont”.

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→Introduction of the Magnetic Field:

1.Using a permanent magnet or an electromagnet that contacts the test piece

2.Flowing an electrical current through the specimen

3.Flowing an electrical current through a coil of wire around the part or through a central conductor running near the part.

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►Advantages of Magnetic Particle Inspection:

1 .Can detect both surface and near sub-surface defects

2. Considered low cost compared to many other NDT methods

3. Is a very portable inspection method especially when used with battery powered equipment

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►Limitations of Magnetic Particle Inspection:

1.Cannot inspect non-ferrous materials such as aluminum, magnesium or most stainless steels.2. Inspection of large parts may require use of equipment with special power requirements.3.Some parts may require removal of coating or plating to achieve desired inspection sensitivity.4.Post cleaning, and post demagnetization is often necessary.

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4 .Ultrasonic testing:►How it works?

→In ultrasonic testing, an ultrasound transducer connected to a diagnostic machine is passed over the object being inspected.→The transducer is typically separated from the test object by a couplant (such as oil) or by water, as in immersion

testing.

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Ultrasonic testing: “Cont”.

►There are two methods of receiving the ultrasound waveform:1. reflection mode→the transducer performs both the sending and the receiving of the pulsed waves as the "sound" is reflected back to the device.

2 .Attenuation mode→a transmitter sends ultrasound through one surface, and a separate receiver detects the amount that has reached it on another surface after traveling through the medium.

►The diagnostic machine displays these results in the form of a signal with an amplitude representing the intensity of the reflection and the distance, representing the arrival time of the reflection

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►Advantages:

1 .High penetrating power, which allows the detection of flaws deep in the part.

2 .High sensitivity, permitting the detection of extremely small flaws.

3 .Greater accuracy than other nondestructive methods in determining the depth of internal flaws.

4 .Capable of portable or highly automated operation

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►Disadvantages:

1 .Parts that are rough, irregular in shape, very small or thin, or not homogeneous are difficult to inspect.

2 .Inspected items must be water resistant, when using water based couplants that do not contain rust inhibitors.

3 .Manual operation requires careful attention by experienced technicians.

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5 .Radiographic (X-ray) testing:

Is a nondestructive testing (NDT) method of inspecting materials for hidden flaws by using the ability of short wavelength electromagnetic radiation (high energy photons) to penetrate various materials.

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►Inspection:

→Before commencing a radiographic examination, it is always advisable to examine the component with one's own eyes, to eliminate any possible external defects.

→If the surface of a weld is too irregular, it may be desirable to grind it to obtain a smooth finish.

→The beam of radiation must be directed to the middle of the section under examination.

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►Inspection: “Cont”.

→The specimen to be inspected is placed between the source of radiation and the detecting device.

→usually the film in a light tight holder or cassette, and the radiation is allowed to penetrate the part for the required length of time to be adequately recorded.

Eng/Mohammed Abd El-Ghani 25

Eng/MA