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.

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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)

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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.

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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

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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

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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).

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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

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The Solution — Profiled Probes

• Minimum wear — retractable ball

plungers

• Easy to handle with glove —

ergonomic shape

• Easy to open and repair, if necessary

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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

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The Solution — Magnifi

Eddyfi’s cutting-edge

acquisition and analysis

software for graphical display

(C-scan), record keeping, and

reporting.

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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.

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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

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