Q: What rule can be used to determine the direction of the magnetic field when using electrical current?
A: The right-hand rule.
Q: What accessory is used to verify magnetic field direction and strength during MPI?
A: Quantitative Quality Indicators (QQIs).
Q: What does a Quantitative Quality Indicator (QQI) show when placed on a part during magnetic particle inspection?
A: Artificial defects or indications that become visible if the magnetic field strength is sufficient.
Q: What is the function of a pie gauge in magnetic particle inspection?
A: To verify magnetic field direction and strength.
Q: What units are used by magnetic field indicators to measure field strength?
A: Gauss or Tesla.
Q: Why is demagnetization important after magnetic particle inspection?
A: Because remnant magnetic fields can adversely affect the function of parts like aircraft components and moving gears
Q: What is the difference between circular and longitudinal magnetic fields in MPI?
A: Circular fields wrap around the part and are produced by direct current passing through the part; longitudinal fields run along the length of the part, produced by solenoids, yokes, or coils.
Q: What magnetizing method uses current carrying prods?
A: Circular magnetization with direct contact method.
Q: What L/D (length to diameter) ratio is generally required when using coil magnetization methods?
A: Between 2 and 15.
Q: What should be done if a part exceeds the maximum L/D ratio for coil magnetization?
A: Inspect the part in sections not exceeding 26 cm (18 inches) on either side of the coil.
Q: What problems can high current cause during magnetic particle inspection?
A: Burning, arcing, excessive background fluorescence, and particle adhesion that can mask defects.
Q: What cleaning methods are commonly used to prepare parts for MPI?
A: Detergent/aqueous cleaning, solvent cleaning, steam cleaning, ultrasonic cleaning, mechanical cleaning, vapor degreasing.
Q: What effect can coatings like chrome plating have on MPI?
A: They can mask discontinuities and affect magnetic field application, potentially causing missed or false indications
Q: What factors should an MPI inspector consider when choosing methods and techniques?
A: Part geometry, expected discontinuities, sensitivity required, and economic considerations.
