What are the basic tools required to conduct a visual inspection?
- Light
- Magnifying glass
- Mirror
Flashlights may have flexible extensions for illuminating inaccessible areas.
What is the maximum length available for fiberoptic borescopes?
Four feet
This allows inspection without disassembly.
What is a video borescope used for?
Inspecting inaccessible locations
It records images using a tiny light-sensitive CCD chip and transmits them to a video monitor.
What are the characteristics of a good weld?
- Even ripples tapering off smoothly
- Free of gas pockets, porosity, and inclusions
- No burn marks or overheating
- No oxide formation more than 1/2 inch from the weld
- Uniform in width
Penetration is the most important characteristic of a good weld.
What is penetration in welding?
Depth of fusion in a weld
It depends on material thickness, filler rod size, and welding technique.
What are signs of poor welds?
- Cracks from rapid cooling
- Irregular edges and variation in depth (cold weld)
- Pitting along edges and long, pointed ripples (excessive heat)
- Too much acetylene causing bumps and craters
Defective welds must be removed and rewelded.
What is liquid penetrant inspection used for?
Locating cracks, porosity, or surface faults
It is suitable for ferrous and nonferrous metals and nonporous plastics.
What principle does dye penetrant inspection rely on?
Capillary attraction
The penetrant is drawn into faults that extend to the surface.
What are the two types of dyes used in liquid penetrant inspection?
- Colored
- Fluorescent
Fluorescent dyes show up as green lines under ultraviolet light, while colored dyes show up as red lines against white developer.
What is dwell time in liquid penetrant inspection?
Time required for the penetrant to cure
It varies based on the size and shape of the discontinuities.
What is the purpose of a dry developer in liquid penetrant inspection?
Acts as a blotter to draw the penetrant out of surface faults
It is typically a loose powder material.
What is a wet developer in liquid penetrant inspection?
A white powder mixed with water applied after rinsing off the surface penetrant
It is used similarly to dry developer.
What is the most common nondestructive inspection method for iron or iron alloys?
Magnetic particle inspection
It involves magnetizing the part and using magnetic particles to detect discontinuities.
What happens to the magnetic domains in a material when subjected to a strong magnetic field?
They align and the part becomes magnetized
This creates north and south poles and lines of flux.
What is the importance of magnetic orientation in magnetic particle inspection?
Ensures lines of flux are perpendicular to the fault
This maximizes disruption detection in the magnetic field.
What is the difference between residual magnetism and continuous magnetism?
- Continuous magnetism: magnetizing force applied during testing
- Residual magnetism: tested after removing magnetizing force
Continuous magnetization is more sensitive for locating subsurface discontinuities.
What do fatigue cracks look like?
Sharp, clear patterns, often jagged and changing direction
They indicate failure in progress and are found in stressed parts.
What are heat-treat cracks characterized by?
Smooth outline, less clear than fatigue cracks
They may show heavy patterns on thin sections.
What is the purpose of demagnetization before returning a part to service?
To prevent detrimental effects on operation
This is accomplished through AC or DC demagnetization.
What does nondestructive testing (NDT) entail?
Inspection without disassembly or destruction of a part
It verifies the integrity of materials and components.
