LEVEL Ⅲ STUDY GUIDE 및 Q&A 기출문제




Q1-2. Bar magnets exhibit which of the following characteristics ?




A. Normally, bar magnets have two poles.

B. Flux lines within the bar magnet are oriented in a circular configuration.

C. There is little or no external magnetic field exhibited by a bar magnet.

D. The magnetic field is totally external.




Q1-7. Surrounding an electromagnet, the magnetic field is strongest :




A. immediately after the current ceases to flow.

B. while the magnetizing current is flowing.

C. at the time the magnetic particles are applied.

D. just prior to current reversal.






Fig. 1

Q1-13. The coercive force of the magnetic material whose hysteresis loop is shown in Fig. 1 is given by :



A. the value of flux density(B) at point d.

B. the value of flux density(B) at point e.

C. the product of B and H at point f.

D. the negative value of H at point c.

E. the area enclosed within the hysteresis loop.




Q1-14. When the magnetizing force is reduced the associated values of B follow the curve a to b in Fig.1 the field o to b is called the :


A. remanent flux.

B. saturation point.

C. hysteresis.

D. characteristic permeability.

E. initial permeability.




Q2-3. What is the recommended amperage range per inch of diameter generally used for circular magnetization of parts, using a DC source?




A. 500-700

B. 800-1000

C. 1200-1400

D. Max. available to insure total magnetization




Q2-5. The lines of flux or force in a circularly magnetized ferromagnetic bar :




A. are aligned through the piece from the south to the north pole.

B. are aligned through the piece from the north to the south pole.

C. leave the south pole and enter the north pole.

D. are contained within and around the part.




Q2-6. In which magnetizing method is the current passed directly through the part, thereby setting up a magnetic field at right angles to the current flow?




A. Longitudinal magnetization

B. Coil magnetization

C. Central conductor magnetization

D. All of the above

E. None of the above




Q2-7. Which of the following is false concerning a magnetic field in and around a hollow conductor as compared to that of a solid conductor of the same outside diameter when both are of the same magnetic material, and when the applied current is the same ?




A. The field immediately outside the outer surface of the hollow conductor is greater.

B. The field gradient inside the hollow conductor is steeper.

C. The fields outside the conductors are the same.

D. The fields are the same at the center.




Q2-8. The field in a section of ferromagnetic pipe being magnetized by means of a central conductor is strongest at the :




A. ends of the pipe.

B. outer surface of the pipe.

C. inside surface of the pipe.

D. middle of the pipe wall.




Q2-9. In magnetizing a 1.5 inch outside diameter tube with a 0.125 inch wall thickness using direct conduction and direct current at 1500 amps, what is the field strength at the internal diameter ?




A. Zero

B. The same as at the outside diameter

C. Fifty percent of the theoretical field strength

D. None of the above




Q2-10. A cylindrical part is to be tested using circular magnetization. The part has three different diameters along its length. A rule of thumb for current values for each diameter provides three current levels. Which of the derived current values should be applied first ?




A. The highest value.

B. The median value.

C. The lowest value.

D. It does not matter which is applied first.




Q3-2. Which of the following is the type of magnetic field that can be induced in parts using permanent magnet yokes?




A. Circular

B. Vector

C. Direct

D. Longitudinal













Q3-19. An advantage of magnetic rubber is that :


A. it can be used on non-ferromagnetic materials.

B. it can be stripped off the surface and examined using magnification.

C. it is a very rapid test method.

D. the materials used are less expensive than dry powder.




Q3-23. The sensitivity of magnetic particle testing is greatest when the discontinuity is :




A. parallel to the direction of the magnetic flux lines.

B. perpendicular to the flow of the magnetizing current.

C. perpendicular to the direction of the magnetic flux.

D. perpendicular to the line between prods.




Q3-27. The magnetic particles are noticed to bunch in some fillet areas and stand on end on the edge of a part being magnetized. These observations indicate that the :




A. particle concentration is too low.

B. flux density is excessive.

C. flux has the improper orientation.

D. flux density is too low.

E. magnetizing current should be changed from AC to DC.




Q3-28. Flux density is a measure of the number of magnetic flux lines perpendicular to a unit area of cross-section. If a discontinuity is in the plane of the unit area, the largest magnetic particle indication will be formed when the discontinuity is :


A. 45° to the flux lines.

B. parallel to the flux lines.

C. 90° to the flux lines.

D. 135° to the flux lines.

E. at an angle not specified in the answers above.




Q3-34. A torsion bar suspension spring failed. Investigation showed that the failure

initiated from a burn on the surface. A possible reason could be that :




A. the current was too high in direct circular magnetization.

B. the probe coil that was used burned the surface.

C. prods were used to detect fatigue.

D. none of the above.







Q3-52. If available, the best method f




A. vapor degreasing.

B. washing with a solvent.

C. wiping the surface with a clean cloth.

D. washing with a strong alkali.




Q4-4. The test used to check the strength or concentration of the wet method

inspection is called the :



A. hardness test.

B. sensitivity test.

C. settling test.

D. hydrometer test.




Q5-11. The glass filter used with mercury vapor UV lights provides peak transmission

nearest which of the following wavelengths ?




A. 2560Å B. 3560Å C. 3650Å D. 5550Å E. None of the above.

D. 200 foot - candles.




Q5-15. Which of the following should be considered before using prods ?




A. Is the metal heat treated to a high strength condition ?

B. Would a burn mar the finish ?

C. Are the prod tips clean and bright ?

D. All of the above should be considered.




Q5-19. The high pressure mercury vapor lamp in the black light is expensive and must

be operated properly to extend its life. The light should be turned off :




A. whenever not in use.

B. after each shot.

C. at the end of the shift.

D. as seldom as practical.
















Q5-20. The magnetizing current ammeter should be calibrated by what type of

instrumentation ?




A. A field strength meter.

B. None. Installed ammeters can be considered to be accurate unless damaged by

overload or accident.

C. A calibrated ammeter and master shunt placed between the machine's current

contacts.

D. A calibrated galvanometer and bridge circuit connected across the installed

ammeter.




Q6-23. The cope side of a casting showed a hazy group of indications in about a

three-inch area. What was the probable cause of the indication ?




A. Porosity

B. Shrinkage

C. Both A and B could produce such indications

D. Such indications are always nonrelevant on the cope side of castings




Q6-26. A group of indications, some sharp and some broad and hazy, were found on an area of a small-forging. Demagnetization and reinspection eliminated these indications. What was the probable cause ?




A. Forging lap

B. Magnetic writing

C. Change in permeability

D. A subsurface variation




Q&A level I




31. Which residual field is most difficult to demagnetize?




a. longitudinal b. circular c. vector d, binodal



















level II

6. Why are large soft contact areas such as lead or copper braid used for surfaces or headstocks?




a. to increase the contact area and reduce the possibility of burnning the part

b. because of their low melting points

c. because they help heat metal, thus facilitating magnetic induction

d. to increase the contact area and flux density




9. If an overall pattern(sometimes circular lines) appears on the test surfaces, how should the inspector reprocess the test piece?




a. retest at a higher amperage

b. demagnetize

c. retest at lower amperage

d. both a and b




17. Which of the following casting defects is caused by nonuinform cooling resulting in stresses which rupture the surface of the metal?




a. shrink

b. hot tears

c. porosity

d. dross




20. When adding concentrate on any wet magnetic particle suspension liquid, it is common practice to :




a. add powder directly to the suspension liquid

b. make a small, slurry-like test mixture of the powder

c. do both of the above

d. do neither of the above




27. The accumulation of particles at a site on the part surface, collected at and held to the site by the magnetic leakage field, is called :




a. a discontinuity

b. a defect

c. an indication

d. magnetic writing




44. When the most complete demagnetization available is desired and demagnetization is to be accomplished by placing the part in a coil energized with AC of progressively decreasing amperage, the following orientation of long axis of the part is most desirable:




a. East-West

b. North-South

c. South-West

d. North-East




47. The unit of measure of one line of flux per square centimeter of area is one :




a. oestered b. ohm c, gauss d, ampere




level III




6. Subjecting a part to a magnetic field that is constantly reversing in polarity and gradually diminishing in strength accomplishes which of the following ?




a. the part becomes magnetized

b. the part becomes demagnetized

c. the strength of the retained magnetic field increases

d. deep-lying defects are located




17. When the external magnetizing force has been removed, some of the magnetic domains remain preferentially oriented. The additional force required to return them to their original random orientation is commonly referred to as :




a. DC electric current force

b. coercive force

c. residual field force

d. applied field force




20. Which of the demagnetization methods listed below is most effective?




a. DC with reversing and step-down control

b. Variable voltage AC with step-down control

c. half-wave rectified AC

d. full-wave rectified










30. Factors that must be considered when interpreting an indication are :




a. the direction of the magnetic field

b. the strength of the leakage field at the indication

c. the orientation and shape of the indication

d. all of the above




34. When using DC, an indication is detected. What is the next logical step to determine if the indication results from a surface or subsurface condition ?




a. reinspect using the surge method

b. demagnetize and apply powder

c. reinspect at higher amperage

d. reinspect using AC




47. Banding is a common term used to describe :




a. field strength relative to the poles of a permanent magnet

b. a method of mounting cylindrical objects on a bench system

c. the appearance of powder patterns at laminations found in heavy plate material

d. powder patterns created by using excess amperage