AAE552 - NDE FINAL EXAM REVIEW | 2025/2026
UPDATE | 92 ACTUAL QUESTIONS AND ANSWERS |
RATED 100% CORRECT!!
What is meant by 'probability of detection'? Answer - (1) NDE is inherently
probabilistic. Even with consistent detection methods, human operators are
inconsistent.
(2) i) Myth: Passing NDE inspection guarantees no flaws.
ii) Fact: All materials contain flaws (Mordfin's 1st axiom), and many are below
detection capability.
(3) Largest flaw missed is much more important than smallest flaw detected.
Reasons for Type I Errors (good part rejected):
- False indications
- Poor cleaning/preparation
- Wrong test applied
- Human factors
- Prior knowledge (expecting to find something)
Reasons for Type II Errors (bad part accepted):
- Wrong test applied (not sensitive to defect of interest)
- Correct test applied incorrectly
- Human factors
- Prior knowledge (ignoring non-hotspots)
,What is a 90/95 crack and why is this metric important? Answer - (1) 90/95
crack is a statistical term that quantifies uncertainty:
i) A crack (a*) can be detected 90% of the time with 95% confidence
(2) Imagine 100 tests performed on multiple specimens with know flaws, this
yields:
i) Each test may have a crack of Xmm that is detected 90% of the time, where
Xmm is different (ie. 4mm on one test, 3.5mm on another)
ii) Observing all tests provides the 95% confidence; ie. for each of the 100 tests
we have different crack lengths detected 90% of the time.
iii) If 95 of those 100 tests have a 90% crack length that is < 6mm, then 6mm =
90/95 crack length:
a) A crack length that can be detected 90% of the time with 95% confidence
iii)
What is a proof test , when may it be useful, ad what information can it
provide? Answer - (1) Process of over-loading a structure or component.
i) IF failure (fracture) does not occur it is known that any cracks must be below
critical size.
ii) If failure does occur a critically-sized crack must have been present.
(2) Example:
i) Material designed to support 7MPa is then proof loaded to 10MPa.
ii) At 10MPa, if a 10mm crack exists, the component will fracture.
iii) If no fracture, cracks are smaller than 10mm.
What are the tools commonly used for visual inspection? Answer - (1) For
visual inspection:
i) Human eye, mirror, magnifying devices, certain light waves (ie. certain light in
visible spectrum like green light).
,ii) Borescopes, fiber-optic cameras, charge-coupled devices.
(2) For defect evaluation:
i) Linear measurements: vernier caliber and micrometer.
ii) Diameter gauges (circular measurements), fillet and radius gauges.
iii) Welds: palmgren gauges
What are the desirable properties of a liquid penetrant? Answer - (1) Needs to
wet surface and be able to enter crack via capillary action.
i) Wetting: ability to spread over surface
a) If adhesion forces (liquid to solid) > cohesive forces (liquid to liquid), liquid
will wet
ii) Capillary action: liquid can enter crack without air of external agents
(pressure/gravity)
iii) NOTE: Viscosity is not in expression for capillary action. Viscosity only
influences the time for capillary action to take place, not the magnitude.
Describe the steps for a liquid-penetrant test. Answer - (1) Clean surface
(2) Apply liquid penetrant
(3) Allow penetration into discontinuities (dwell-time)
(4) Remove excess penetrant
(5) Apply developer
(6) Developer draws liquid out from cracks (bloom)
(7) Locate/interpret discontinuities
(8) Clean surface of residual developer/penetrant
(9) (Image of 6 steps)
What is the purpose of a developer? Answer - (1) Acts as a blotter to draw out
trapped penetrant from flaws
, (2) Spreads penetrant over surface, increasing visibility
(3) Provides high-contrast background to increase visibility
i) Fluorescent: Blue-Black
ii) Red-Dye: White
(4) Forms of developers: DWWN - Don't Wade in Water Nude
i) Form A: Dry Powder
a) Part exposed to cloud of developer. Part must be thoroughly dried before
application.
b) Insufficient contrast for use with non-fluorescent (type II penetrants)
ii) Form B: Water Soluble
a) Used with both fluorescent and non-fluorescent. Applied as dry powder
concentrate, mixed with water.
iii) Form C: Water Suspendable
a) Used in type I and type II (fluorescent and non-fluoro)
b) Supplied as dry concentrate, dispersed in water
iv) Form D: Non Aqueous Solvent Suspendable
a) Used for both types. Sold in ready-to-use form
What is the difference between penetrant types? Answer - (1) Penetrant types:
i) Type I (Fluorescent):
a) Level 1/2: Ultralow sensitivity
b) Level 1/2/3/4 --> Low/Medium/High/Ultrahigh Sensitivity
c) Higher sensitivity --> detects smaller cracks
ii) Type II (Non-fluorescent):
a) Have approximately Level I sensitivity
UPDATE | 92 ACTUAL QUESTIONS AND ANSWERS |
RATED 100% CORRECT!!
What is meant by 'probability of detection'? Answer - (1) NDE is inherently
probabilistic. Even with consistent detection methods, human operators are
inconsistent.
(2) i) Myth: Passing NDE inspection guarantees no flaws.
ii) Fact: All materials contain flaws (Mordfin's 1st axiom), and many are below
detection capability.
(3) Largest flaw missed is much more important than smallest flaw detected.
Reasons for Type I Errors (good part rejected):
- False indications
- Poor cleaning/preparation
- Wrong test applied
- Human factors
- Prior knowledge (expecting to find something)
Reasons for Type II Errors (bad part accepted):
- Wrong test applied (not sensitive to defect of interest)
- Correct test applied incorrectly
- Human factors
- Prior knowledge (ignoring non-hotspots)
,What is a 90/95 crack and why is this metric important? Answer - (1) 90/95
crack is a statistical term that quantifies uncertainty:
i) A crack (a*) can be detected 90% of the time with 95% confidence
(2) Imagine 100 tests performed on multiple specimens with know flaws, this
yields:
i) Each test may have a crack of Xmm that is detected 90% of the time, where
Xmm is different (ie. 4mm on one test, 3.5mm on another)
ii) Observing all tests provides the 95% confidence; ie. for each of the 100 tests
we have different crack lengths detected 90% of the time.
iii) If 95 of those 100 tests have a 90% crack length that is < 6mm, then 6mm =
90/95 crack length:
a) A crack length that can be detected 90% of the time with 95% confidence
iii)
What is a proof test , when may it be useful, ad what information can it
provide? Answer - (1) Process of over-loading a structure or component.
i) IF failure (fracture) does not occur it is known that any cracks must be below
critical size.
ii) If failure does occur a critically-sized crack must have been present.
(2) Example:
i) Material designed to support 7MPa is then proof loaded to 10MPa.
ii) At 10MPa, if a 10mm crack exists, the component will fracture.
iii) If no fracture, cracks are smaller than 10mm.
What are the tools commonly used for visual inspection? Answer - (1) For
visual inspection:
i) Human eye, mirror, magnifying devices, certain light waves (ie. certain light in
visible spectrum like green light).
,ii) Borescopes, fiber-optic cameras, charge-coupled devices.
(2) For defect evaluation:
i) Linear measurements: vernier caliber and micrometer.
ii) Diameter gauges (circular measurements), fillet and radius gauges.
iii) Welds: palmgren gauges
What are the desirable properties of a liquid penetrant? Answer - (1) Needs to
wet surface and be able to enter crack via capillary action.
i) Wetting: ability to spread over surface
a) If adhesion forces (liquid to solid) > cohesive forces (liquid to liquid), liquid
will wet
ii) Capillary action: liquid can enter crack without air of external agents
(pressure/gravity)
iii) NOTE: Viscosity is not in expression for capillary action. Viscosity only
influences the time for capillary action to take place, not the magnitude.
Describe the steps for a liquid-penetrant test. Answer - (1) Clean surface
(2) Apply liquid penetrant
(3) Allow penetration into discontinuities (dwell-time)
(4) Remove excess penetrant
(5) Apply developer
(6) Developer draws liquid out from cracks (bloom)
(7) Locate/interpret discontinuities
(8) Clean surface of residual developer/penetrant
(9) (Image of 6 steps)
What is the purpose of a developer? Answer - (1) Acts as a blotter to draw out
trapped penetrant from flaws
, (2) Spreads penetrant over surface, increasing visibility
(3) Provides high-contrast background to increase visibility
i) Fluorescent: Blue-Black
ii) Red-Dye: White
(4) Forms of developers: DWWN - Don't Wade in Water Nude
i) Form A: Dry Powder
a) Part exposed to cloud of developer. Part must be thoroughly dried before
application.
b) Insufficient contrast for use with non-fluorescent (type II penetrants)
ii) Form B: Water Soluble
a) Used with both fluorescent and non-fluorescent. Applied as dry powder
concentrate, mixed with water.
iii) Form C: Water Suspendable
a) Used in type I and type II (fluorescent and non-fluoro)
b) Supplied as dry concentrate, dispersed in water
iv) Form D: Non Aqueous Solvent Suspendable
a) Used for both types. Sold in ready-to-use form
What is the difference between penetrant types? Answer - (1) Penetrant types:
i) Type I (Fluorescent):
a) Level 1/2: Ultralow sensitivity
b) Level 1/2/3/4 --> Low/Medium/High/Ultrahigh Sensitivity
c) Higher sensitivity --> detects smaller cracks
ii) Type II (Non-fluorescent):
a) Have approximately Level I sensitivity
