Glossary of eddy current inspection
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- what are some of the advantages of Eddy current?
- fast, automated, no harm to part, no post cleaning, equip is light and portable, sensitive to small surface cracks, wide range of applications.
- Disadvantages of eddy current?
- applicable only to metal, Electrical and magnetic interference may cause problems, requires highly trainded personnel, and affected by numerous variables.
- What is the movement of electric charge?
- Current flow (electrons)
- An electric field drives?
- Free electrons
- Within a wire electrons collide with the atoms making up the conductor, what does this collision do?
- slows them down and caused energy loss through heat.
- the collision of elctrons and atoms also limits whats?
- Current flow
- What type of material losses large amounts of energy to heat?
- High resistivity materials.
- What type of material produces little heat?
- Low resistivity materials.
- What is the opposite of resistivity?
- Low conductivity equals?
- High resisistivity.
- low resistivity has?
- High conductivity.
- What is defined as magnetic field?
- When a traveling electron has a force act upon it in a sidways manner.
- Like an electric current a magnetic field can do what?
- exer a force on electrons producing current flow.
- in order for current to flow either the magnetic field or the conductor must?
- Move past each other.
- When a magnet is moved past a conductor what two thing happen?
- current is induced
An the current that is induced creates a secondary magnetic field.
- What is lenz's law?
- States that when a magnet and a conduct move past each other current flow is induced and a secondary magnetic field is created.
- The magnetic field around a straight wire is week unless?
- Alot of current is pushed through it.
- By forming a wire into a coil what is the result?
- It produces a stronger magnetic field with far less current.
- As current builds from 0-max what happens?
- lines of induction are geerated and move from the coil
- At max current the max number of lines of induction exist where?
- At the max distance from the coil.
- A coil resting on a surface of an electrical conductive material induce current flow where>
- Directly below the coil and weaker current ouside the coil dia.
- the total opposition to current flow ina coil?
- opposes current flow by causing impedance of the wire
- What is reactance?
- p[ses chamges in current flow by causing energy to ve strored in the field around the wire.
- What are actually the two types of reactance?
- inductive, and compasititve.
- What is resistance?
- When isolated from reactance is the ratio of and applied voltage to current flowing through a circuit.
- When coltage is applied the current?
- Startes and stops at exactly the same time as the voltage.
The voltage and current are said to be in phase.
- =Whgen isolated from resistance is the opposition to the flow of AC current caused by?
- Inductance in a circuit current lage 90 Degrees.
- Eddy current testing is accomplished by?
- oberving changes in impedance of a coil of wire.
- Meter insutruments messure the changes in?
- resistance and reactance in neddle movement/
- A measure of ease with which electrons can flow through a material?
- Conductivity also the opposite of resistivity.
- Conductivity is based on what?
- IACS copper.
- Distribution and intensity of eddy currents in nonmagnetic parts are affected by?
- magnitude of eddy currents imediatly below the surface is dependent on the?
- Conductivity of the part
- High conductivity equals?
- Strong eddy currents
- penetrating levels are stronger in?
- Poor conductive materials.
- Eddy current can be used to sort parts of different?
- the ease in which a part may be magnetized?
- in ferromagnetic materials permeablilty rather than conductivity is the principle factor in determining what?
- eddy current response.
- ferromagnetic materials gretly increase the flux density of?
- eddy current coils field
- As the magnetic field of the coil comes in contact with the test part what happens?
- current flow is induced.
- the closer the coil is to the part the stronger what will be?
- The stronger the eddy currents.
- the futher away from the part the weaker the eddy current field will be provieded what happens?
- The magnetic field is still in contact with the part
This change in coupling is refered to as lift off.
- the term describling the degree of magnetic coupling for both the inside ddiameter coil and ousided diameter of a part.
- fill factor
- A fill factor of what gives a reasonably sensitivity and clearance?
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