Materials & Proccesses

Eddy Currents may also be used in repair of aluminum aircraft damage by fire or excessive heat

*NOTE*

Give a brief description of a dye penetrant inspection

- A penetrating liquid, (dye) is applied to a part, seeping into any open defects - The penetrant is allowed to dwell then excess penetrant is carefully removed -Developer is applied to the surface to draw out the dye from any open defects -The part is inspected and results interpreted

List a few basic principals of eddy currents

-A magnetic field is induced -This in turn induces a voltage of opposite polarity in the coil andopposes the flow of current -If the coil is placed so that themagnetic field passes througha conductor (specimen) eddycurrents are formed -A crack or discontinuity disrupts the eddy currents giving an indication

Give 2 preparation steps for Magnetic Particle Inspection? What platings interfere with and magnetic particle inspections? What may prevent indications or inclusions?

1) -Clean surface thoroughly removed all grease oil and dirt - plug all small opening, oil holes, and internal passages 2) Plating such as cadmium, copper, tin and zinc 3) Chromium and nickle

This inspection uses electromagnetic analysis, is composed of free electrons under the influence of an induced electromagnetic field which are made to drift through metal? And is used to inspect?

1) Eddy Current Inspection 2) Jet Turbine shafts, vanes, wing skins, wheels, bolt holes, spark plug bores, forcracks, heat or frame damage

What are 3 major steps in the x-ray process

1) Exposure to radiation including preparation 2) Processing of film 3) Interpretation of the radiograph

What two conditions may create accumulations of penetrant that are sometimes confused with true surface discontinuities

1) First condition involves indications caused by poor washing 2) False indications may also be created where parts press fit to each other

What 2 types of equipment are used in a magnetic particle inspection?

1) Fixed(non-portable) General Purpose Unit & Portable General Purpose Unit

What are the three basic functions performed by the eddy current instrument

1) Generating 2) Receiving 3) Displaying

Magnetic Particle Inspection: 1) What does it detect & what is it good for detecting? 2) What is applied after magnetizing 3) What disturbs the magnetic lines of force and causes particles to form a patterns

1) Invisible cracks and defects in ferromagnetic materials 2) Detecting defects on or near the surface 3) Ferromagnetic particles ( may be liquid or dry powder) 4) Discontinuity

List some major limitations of the penetrant inspections

1) It can only detect those discontinuities that are open to the surface 2) some roughness or porosity can limit the use of penetrant liquids 3) such surfaces can produce excessive background indications and interfere with the inspections

What is the main disadvantage of the penetrant inspection? The visibility of the penetrating material is increased by the addition of 1 of 2 types of dye, which are?

1) Must be open to the surface in order to let the penetrant get into the defect 2) Visible or fluorescent dyes

Name the 3 basic ultrasonic inspection methods

1) Pulse echo 2) Through transmission 3) Resonance

What are the two basic ultrasonic inspections

1) Pulse echo inspections 2) through transmission inspection

After a Magnetic Particle Inspection, what must be removed? This is to prevent what?

1) Residual Magnetism 2) Demagnetizing is to prevent magnetizing parts from attracting filings, grindings, chips or steel particles resulting from operational wear - A convenient procedure is subjecting the part to a magnetizing force that is continually reversing in direction and gradually reversing in strength

What are the principal distinguishing features of indications?

1) Shape 2) Buildup 3) Width 4) Sharpness of the outline These characteristics are more valuable in distinguishing between types of discontinuities than in determining their severity

List 5 types of stress

1) Tension 2) Compression 3) Torsion 4) Bending 5) Shear

Briefly list the steps for performing a penetrant inspection

1) Thoroughly cleaning of the metal surface 2) Applying penetrant 3) removing penetrant with a removed emulsifier or cleaner 4) drying the part 5) applying the developed 6) Inspecting and interpreting results

Name a few factors that effect the type of inspection to use.

1) Type of materials being used 2) Type of defect being looked for 3) The maintenance manual and or other directives

With this inspection it is possible to locate defects in all types or materials. List two basic methods for this inspections and describe

1) Ultrasonic Inspection 2) Immersion Testing - the part under examination and the search unit are totally immersed in a liquid couplant, which may be water or any other suitable fluid Contact Method - part under examination and the search unit are coupled with a viscous material liquid or paste which wets both the face of the search unit and material under examination

What two type of dye penetrant kits are there? What else do they contain

1) Visible and fluorescent 2) Dye Penetrant, Dye remover emulsifier, developer, and black light assembly

Penetrant Inspection will detect such defects as? These defects may be caused by?

1) cracks or porosity 2) Fatigue cracks, shrinkage cracks, shrinkage porosity, cold shuts, grinding and head treat cracks, seams, forging, laps and bursts - also indicate a lack of bond between joined metals

Excessively high flux densities may form? Excessively low?

1) non-relevant indications 2) may not show all discontinuities

List five things that Eddy Currents inspections are used for

1) well suited for detection of service induced cracks 2) greatest application for inspecting small localized areas 3) used to inspect surface cracks 4) sub-surface cracks 5) detect the loss of metal as a result of corrosion

Various types of indicating mediums are available for a magnetic particle inspection, they may be divided into 2 general materials which are? What are the colors for each procedure? And for acceptable operation, an indicating medium must be?

1) wet and dry 2) Red and Black for wet, Red black and grey for dry 3) High Permeability - ensures a minimum of magnetic energy will be required to attract & Low retentivity - mobility of magnetic particles

The nomenclature of steels

A numerical index sponsored by the SAE (society of automotive engineers) and the AISI (American iron and steel institute)

What type of light is used with a fluorescent penetrant inspection?

Black Ultraviolet Light

This is a device that enables the inspector to see inside areas that could not otherwise be inspected without disassembly

Borescope

Allows little bending or deformation apt to break or crack without change Cast iron, cast aluminum and very hard steel

Brittle Metal

This type of magnetization will locate defects running parallel to the axis of the part

Circular Magnetization

To located a defect in a part it is essential for the magnetic lines of force to pass approximately perpendicular to the defect. Therefore necessary to induce magnetic flux in more than 1 direction. This requires 2 separate magnetization operations.

Circular and longitudinal magnetization

Is the property which enables a metal to carry heat or electricity

Conductivity

In this inspection METHOD, the part is magnetized and the indicating medium is applied while the magnetizing force is maintained - Provides greater sensitivity than the residual procedure, particularly in locating subsurface discontinuities

Continuous Inspection Method

Weight of a unit volume of a metal

Density of a metal

What form of natural action occurs during the developer application that makes defects more visible

Developer acts like a blotter to assist the natural capillary action, bleed out of penetrant

This is defined as an interruption in the normal physical structure or configuration of a part such as a forging lap, seam, inclusion, porosity and the like

Discontinuity

This inspection involves the intersection of magnetic fields and circulatory currents, is composed of free electrons under the influence of an induced electromagnetic field which are made to drift through metal. Can also detect the harness of a material.

Eddy Current Inspection

What types of metals are used in the aircraft

Ferrous metals, iron, steel and steel alloys

Magnetic Particles can be non-fluorescent or fluorescent, which is preferred?

Fluorescent because of their high sensitivity

Name the properties of metals

Hardness Strength Density Malleability Ductility

Name some properties of metals

Hardness, strength, density, malleability, ductility, elasticity, toughness, brittleness, fusibility, conductivity, thermal expansion

Any process that involves controlled heating and cooling of metals to develop certain characteristics is called?

Heat Treatment

Longitudinal Magnetization

Is produced by placing a part in a solenoid excited by electric current, a magnetic field is produced in a direction parallel to the long axis of the part

Circular Magnetization

Is the induction of a magnetic field consisting of concentric circles of force about and within the part which is achieved by passing electric current through the part

The basic purpose of a penetrant inspection?

Is used on non-porous metal and non metal components to find material discontinuities that are open to the surface and may not be evident to a normal visual inspections

Name a few areas in which the eddy current inspection is used

Jet engine turbine shafts and vanes, wing skins, wheels, bold holes, and spark plug bores for cracks, heat of frame damage.

Detects defects open to the surface in nonporous materials such as: Aluminum, Magnesium, Brass, Copper, Cast iron Stainless steel, Titanium

Liquid Penetrant Inspection

This is a non destructive test for defects open to the surface made of any non porous material. used on such metals such as aluminum magnesium brass copper cast iron stainless steel and titanium - may also be used on ceramics plastics molded rubber and glass

Liquid penetrant inspections

This is a method of detecting invisible cracks and other defects in ferromagnetic materials such as iron and steel, and is NOT applicable to non magnetic materials

Magnetic Particle Inspection

If removal of excess penetrant involves water or other cleaning liquids; how can drying time be decreased?

Ovens or Ventilation Systems

To find a defect line of force, flux should pass ____ to the defect

Perpendicular

What are two conditions that can cause accumulations of penetrant and confusion with true defects

Poor Washing Press fit parts

In this inspection method, flaws are detected by measuring the amplitude of signals reflected and the time required for these signals to travel between specific surfaces and the discontinuity

Pulse Echo

These type of inspection techniques are used to locate defect or flaws in airframe structures or engines with litter or no dis-assembly, requires extensive training

Radio-graphic Inspections

This PROCEDURE involves the magnetization of parts and application of the indicating medium after the magnetizing force has been removed - Relies on residual or permanent magnetism - More practical than the continuous procedure - Only used with steels that have been heat treated

Residual Inspection Procedure

Used principally for thickness measurements when the two sides of the material being tested are smooth and parallel and the backside is inaccessible

Resonance

Service induced cracks in aircraft structures are generally caused by what?

Service induced cracks in aircraft structures are generally caused by fatigue or stress corrosion

What methods can be used to apply penetrant

Spraying, brushing, or completely submerging part in container of penetrant

What is the important property of a metal

Strength

Define malleability

The ability of a material to be stretched or shaped, do not crack when they are formed this way, gold and lead have high degrees of malleability

What is the objective of a NDT

The objective of an NDI or NDT, is to determine the airworthiness of a component without damaging it

This inspection uses two transducers, one to generate the pulse and another place on the opposite surface to receive it. IT is less sensitive to small defects than a pulse-echo method

Through Transmission

What does flux mean?

To find a defect line(s) of force