C— flaws on or near the surface.
Magnetic particle inspection is used to detect flaws in ferromagnetic material on or near the surface. These flaws form north and south magnetic poles when the part is magnetized. Iron oxide suspended in a f luid pumped over the part is attracted to and held by the magnetism and it outlines the flaw.
C— Ferrous and nonferrous metals and nonporous plastics.
Liquid penetrant inspection methods may be used to detect faults that extend to the surface on both ferrous and nonferrous metals and nonporous plastics.
C— Ultrasonic inspection.
Ultrasonic inspection uses high-frequency sound waves to detect faults in a material. It can be used on a wide variety of materials such as ferrous and nonferrous metals, plastics and ceramics. It can detect subsurface as well as surface defects.
8221-1.
Which of the following defects are not acceptable for metal lines?
A— Scratches or nicks on the inside of a bend less than 10% of wall thickness.
B— Dents in straight section that are 10% of tube diameter.
C— Dents in straight section that are 20% of tube diameter.
C— Dents in straight section that are 20% of tube diameter.
Scratches or nicks less than 10% of the wall thickness of the tube are repairable if they are not in the heel of the bend, as are dents that are 10% of tube diameter. A dent of more than 20% of the tube diameter is not acceptable.
A— Eddy current inspection.
Eddy current inspection requires relatively little preparation of the part being inspected. It induces a magnetic field into the part which causes eddy currents to flow. Variations in the magnitude of the eddy currents affect this magnetic field, and when it is analyzed electronically, it gives information regarding such structural characteristics as flaws, discontinuities, thickness, and alloy or heat-treated condition of the material. Eddy current inspection is used to locate defects both on the surface and below the surface.
C— Continuous.
The continuous method of magnetic particle inspection is used for most aircraft parts because it provides the strongest magnetic field to attract the oxide from the fluid. In the continuous method of magnetic particle inspection, the part is either placed between the heads of the magnetizing machine or held inside the solenoid (coil). Magnetizing current flows while the fluid is pumped over the part. In the residual method of magnetic particle inspection, used for some smaller parts, the parts are magnetized and the magnetizing current is shut off. Only residual magnetism is left in the part to attract the oxide.
B— Material thickness and density and the type of defect to be detected.
The factors of radiographic exposure are so interdependent that it is necessary to consider all factors for any particular radiographic exposure. These factors include, but are not limited to, the following:
1. Material thickness and density.
2. Shape and size of the object.
3. Type of defect to be detected.
4. Characteristics of X-ray machine used.
5. Exposure distance.
6. Exposure angle.
7. Film characteristics.
8. Type of intensifying screen, if used.
A— high permeability and low retentivity.
The testing medium used to indicate the presence of a fault in magnetic particle inspection is a finely ground iron oxide that has a high permeability and low retentivity, and is nontoxic. It is usually suspended in a light oil such as kerosine.
C— It may be used with steels which have been heat treated for stressed applications.
In the residual method of magnetic particle inspection, the part is magnetized and removed from the magnetic field before the oxide-carrying fluid is pumped over it. Steel that has a high retentivity (retains its magnetism after the magnetizing force has been removed) can be inspected by the residual method. Steel that has been heat-treated for stressed applications has a high retentivity and it can be inspected by the residual method.
B— Metallic ring test.
After a bonded honeycomb repair has been made using the potted-compound repair technique, the soundness of the repair can be tested by using the metallic ring test. The repaired surface is tested by tapping it with the edge of a coin. If the repair is sound, the tapping will produce a metallic ringing sound. If there is any void in the material, the tapping will produce a dull, thudding sound.
B— Wet and dry process materials.
The magnetic medium used for magnetic particle inspection can be applied either as a dry oxide powder dusted over the surface or (as is more commonly done) suspended in a light oil such as kerosine and pumped over the surface.
The iron oxide used as the indicating medium is often treated with a fluorescent dye that causes it to glow with a green light when an ultraviolet light (black light) is shone on it.
C— Iron alloys.
In order for a part to be inspected by the magnetic particle method, it must be magnetizable. The only magnetizable metals listed are iron alloys.
B— slowly moving the part out of an AC magnetic field of sufficient strength.
A steel part is magnetized by holding it in a strong, steady magnetic field that aligns all of the magnetic domains in the material.
It is demagnetized by placing it in an AC magnetic field that continually reverses its polarity. This causes the domains to continually reverse their direction. As the domains are reversing, the part is slowly moved from the field so the domains remain in a disoriented state when the demagnetizing force is removed.
A— 45°.
Longitudinal magnetization produces a magnetic field that extends lengthwise in the material. It is used to detect faults that extend across the part, perpendicular to the lines of magnetic flux.
Circular magnetization produces a magnetic field that extends across the material. It can detect faults that are oriented along the length of the part.
Either type of magnetization can detect a fault that runs at 45° to the length of the part.
A— Dye penetrant inspection and eddy current inspection.
Dye penetrant, eddy current, ultrasonic, and visual inspections may be used on aluminum forgings and castings. Magnetic particle inspection can only be used on ferrous metals, and the metallic ring inspection is used to check for delamination in bonded composite structural materials.
B— a longer-than-normal penetrating time.
The amount of penetrant that can enter a small crack is determined by both the length of time the penetrant is allowed to remain on the surface and the temperature of the part.
When looking for very small cracks, the part can be heated (but not enough to cause the penetrant to evaporate from the surface), and the penetrant can be allowed to stay on the surface for a longer than normal time before it is washed off.
8233-1.
Which of the following is a main determinant of the dwell time to use when conducting a dye or fluorescent penetrant inspection?
A— The size and shape of the discontinuities being looked for.
B— The size and shape of the part being inspected.
C— The type and/or density of the part material.
A— The size and shape of the discontinuities being looked for.
The dwell time (the time the penetrant is allowed to remain on the surface) is determined by the size and shape of the discontinuity being looked for.
A— reveal all possible defects.
Since longitudinal magnetization detects faults that lie across a part, and circular magnetization detects faults that lie parallel to its length, a complete inspection that will show up all possible defects requires that the part be magnetized twice, longitudinally and circularly, and given two separate inspections.
A— a large disruption in the magnetic field.
In order to locate a defect in a part by the magnetic particle inspection method, it is essential that the magnetic lines of force pass approximately perpendicular to the defect. This causes the maximum disruption of the magnetic field and forms magnetic poles which attract the indicating medium across the defect.
C— was not thoroughly washed before the developer was applied.
After the penetrant has been on the surface of a part for the correct dwell time, the surface must be thoroughly washed to remove all traces of the penetrant. When the surface is clean and dry, the developer is sprayed or dusted on. Any penetrant left on the surface or in the pores of the material will stain the developer and faults will not show up as sharp and clear marks.
(1) An aircraft part may be demagnetized by subjecting it to a magnetizing force from alternating current that is gradually reduced in strength.
(2) An aircraft part may be demagnetized by subjecting it to a magnetizing force from direct current that is alternately reversed in direction and gradually reduced in strength.
Regarding the above statements,
A— both 1 and 2 are true.
B— only 1 is true.
C— only 2 is true.
A— both 1 and 2 are true.
Statement 1 is true. A part is demagnetized by placing it in an AC magnetic field whose strength is gradually reduced while it continually reverses its polarity. This leaves the domains in a disoriented state when the demagnetizing force is removed.
Statement 2 is also true. A DC magnetic field whose direction is continually reversed and the strength is gradually reduced may be used to demagnetize an aircraft part that has been inspected by the magnetic particle inspection method.
C— parallel lines
Inclusions are impurities trapped inside a piece of metal when it was cast.
When the part is inspected by magnetic particle inspection, the inclusion does not show up as a clearly defined fault but the indication is fuzzy.
Rather than sharply defined poles, there are several sets of poles that cause the oxide to form in a series of parallel lines.
A— a volatile petroleum-base solvent.
It is important when performing a dye penetrant inspection that the surface of the part be as clean as possible.
Volatile petroleum-based solvents such as Stoddard solvent and naphtha are widely used for cleaning parts to be inspected.
C— The discontinuity is found in a highly stressed area of the part.
Fatigue cracks usually show up in areas that have been subjected to high concentrations of stresses. They are likely to form where the cross-sectional area of the part changes sharply.