The same signed cards as the trainer above, in one list to read or print.
- Relevant, nonrelevant, false: what separates them?
- Cause. Relevant: leakage field from a real discontinuity. Nonrelevant: real leakage, but from a design or permeability feature (thread root, keyway, section change, joint). False: no leakage field at all; particles held by residue, roughness, lint or drainage.Topic: relevant, nonrelevant and false indications
- Suspected false indication: first check?
- Clean the area and reprocess the same way. Gone: likely residue, drainage or lint. Returns: leakage, or surface texture that holds particles. If it returns, change the field direction before deciding.Topic: false indications, verification by reprocessing
- Settling test vs water-break test: what does each show?
- Settling test: particle concentration, and any contamination layer. Water-break test: whether a water-based bath wets the part in an unbroken film.Topic: bath checks, settling test and water-break test
- Electromagnetic vs permanent-magnet yoke: key contrast?
- An electromagnetic yoke can be switched off before lifting. A permanent magnet cannot, so lifting can disturb indications and it draws loose steel. Its strength is also fixed.Topic: portable yokes
- Duty cycle 10% with 3 s shots: minimum start-to-start time?
- Duty cycle = on-time / total cycle. 3 s / 0.10 = 30 s per cycle. Exercise numbers; real ratings come from the maker's data plate.Topic: power pack duty cycle
- Inherent, processing, service: where does each arise?
- Inherent: from solidification and primary forming (pipe, porosity, inclusions). Processing: from forming, welding, heat treatment, finishing (laps, quench and grinding cracks). Service: in use (fatigue, stress corrosion).Topic: inherent, processing and service discontinuities
- Retentivity vs coercive force?
- Retentivity: how much magnetism stays when the field is removed. Coercive force: the reverse field needed to bring it back to zero. High values of both make a part harder to demagnetize.Topic: hysteresis loop terms
- Circular vs longitudinal field: which flaws does each find?
- Each field finds discontinuities that cross it. Circular (current through the part) finds flaws along the length. Longitudinal (coil or yoke) finds flaws across the part.Topic: circular and longitudinal fields
- Why can a discontinuity create a magnetic leakage field?
- A discontinuity changes the magnetic path. Part of the flux can take an air path near the surface and attract particles. Leakage does not require the surrounding steel to be saturated.Topic: reluctance and the leakage field
- AC, half-wave DC, three-phase full-wave DC: rank field depth and particle mobility.
- Depth: AC shallowest, half-wave DC deeper, three-phase full-wave DC deepest. Mobility runs the other way: AC best, half-wave DC very good with dry powder, three-phase full-wave DC lowest.Topic: current types, field depth and particle mobility
- Head shot, central conductor, coil: which flaws does each show?
- Head shot and central conductor give circular fields, so they show flaws running along the part's axis. A coil gives a longitudinal field, so it shows flaws running across the part. Pick the setup whose flux crosses the expected crack.Topic: matching field direction to flaw direction
- Soft shaft versus hardened pin: which is harder to demagnetize, and why?
- The hardened pin. Its coercive force is higher, so a stronger reversing field is needed to bring its flux to zero. The setting that cleared the soft shaft may leave a field in the pin.Topic: coercive force and demagnetizing effort