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Gears have been around for a long time. They are used to multiply force and change the rotation axis, and they are found everywhere —from heavy machinery to precision instruments. For safety and life-cycle considerations, mission-critical gears must regularlybe inspected for surface-breaking cracks.
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Detecting Surface Cracking in Gears to Extend Their Useful LivesApplication Note
Introduction
Gears have been around for a long
time. They are used to multiply force
and change the rotation axis, and
they are found everywhere — from
heavy machinery to precision
instruments.
For safety and life-cycle
considerations, mission-critical
gears must regularly be inspected
for surface-breaking cracks.
2 © Eddyfi 2014
The Challenge
Gear teeth are prone to surface
cracking because of the constant
torque they are submitted to.
These cracks are typically found in:• Addendum
• Dedendum
• Fillet
Other possible flaws include
macropitting and corrosion in cast and
forged gears.3 © Eddyfi 2014
The Challenge
Depending on the size and type of gears, operators look for
surface-breaking cracks using any combination of:• Magnetic particle testing (MT)
• Dye-penetrant testing (PT)
• Ultrasonic testing (UT)
4 © Eddyfi 2014
The Challenge
MT and PT
• Time consuming
• Can easily miss small defects
• Only offer crude reporting/record-keeping capabilities
• Require pre-inspection and post-inspection clean-ups
At best, these two testing methods can help detect the
existence of flaws, but they only offer rudimentary length
information.
5 © Eddyfi 2014
The Challenge
UT
• Can be faster than MT and PT
• Better record-keeping capabilities than MT and PT
• Somewhat blind to surface-breaking cracks because of
intrinsic near-surface “dead zone”
• Requires pre-inspection and post-inspection clean-ups
because it needs close contact and the use of couplant
6 © Eddyfi 2014
The Solution
Compact ECA probes designed for gear teeth profiles, that
are rugged and easy to handle, and that are capable of
faster inspections, as well as full record-keeping capabilities.
Three-part solution:• Ectane™ test instrument
• Profiled and adjustable ECA surface probes
• Magnifi ® acquisition and analysis software
7 © Eddyfi 2014
The Solution — Ectane
Eddyfi’s workhorse test instrument. • Can be configured for almost any type of inspection technique, including
ECT and eddy current array (ECA).
8 © Eddyfi 2014
The Solution — Probes
• Shapes and sizes of gear tooth profiles vary greatly
• Gear tooth profile shapes usually require custom profiles
or adjustable solutions
• Such solutions minimize lift-off and increase probe
sensitivity
• Similar ECA technology in custom profile probes and
adjustable probes
9 © Eddyfi 2014
The Solution — Profiled Probes
• Minimum wear — retractable ball
plungers
• Easy to handle with glove —
ergonomic shape
• Easy to open and repair, if necessary
10 © Eddyfi 2014
The Solution — Adjustable Probes
• Designed to adjust to complex geometries
• Easy to handle
• Perfect for one-pass examinations of: • Gear teeth
• Pinions
• Other smooth, curved surfaces
11 © Eddyfi 2014
The Solution — Magnifi
Eddyfi’s cutting-edge
acquisition and analysis
software for graphical display
(C-scan), record keeping, and
reporting.
12 © Eddyfi 2014
Actual scan data
Magnifi produces 2D and 3D C-scans:• Color patterns to detect and size the length and depth of surface-breaking
cracks with ease.
Its high-performance acquisition and analysis capabilities
make computerized record-keeping and reporting possible.
ASTM Standard
Eddy current array (ECA) technology is instrumental to
ASTM E2905. This standard, recognized by world leaders in
the industry, takes full advantage of ECA and demonstrates
how beneficial this technology is in terms of productivity.
Cleaning is easier than ever and is part of the ASTM E2905.
A 10 m ring gear and pinion set can now be cleaned in less
than an hour. And there is no need to wipe the gear teeth
down after the cleaning, saving numerous person hours.
13 © Eddyfi 2014
The Benefits
Our gear inspection solutions offer several advantages over
other solutions on the market:• Faster inspections
• Higher sensitivity to surface-breaking cracks
• Easier interpretation with C-scan imaging
• Only pre-inspection clean-up necessary — save several person hours
• Easier manipulation
• Complete, computerized data recording and archiving capabilities
Whether you need to inspect small or giant gears, Eddyfi will
always deliver a solution adapted to your application.14 © Eddyfi 2014