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CTIS # 29950

Prepared By John Yurtin

Updated 2-9-2005

Connection Systems Training

Vibration & Fretting CorrosionVibrationVibration

Delphi Confidential2

Having a good technical understanding of the expectations and performance of connections can help you properly apply them within the vehicle. Vibration performance should be clearly understood since it is one of the more significant issues in vehicle performance.

This training help you understand vibration issues and how they apply to customer applications.

Excellence

Performance Goal: Do it right the first time, every time

Method: Innovation and continuous improvement

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Agenda

Most Important Comment Terminology Vibration Testing Fretting Corrosion Field Observations Lab Variation Lab Testing Factors In Vibration Issues Summary Wish List

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The vibration performance of a connector in a specific vehicle application may not be the same as its performance tested to a specification in the laboratory!

The following factors of application are of greater significance than the design of the terminal / connector system:

– Wire harness design and routing

– Connector and harness attachment methods

– Harness coverings and wire types

– Harness bundle size

– Connector lock mechanisms

– Damping effects of seals

The standard specifications are excellent for comparison, but really do not represent actual in vehicle performance!

Very Important!

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“ The best connection can fail in an application if improperly applied, and the worst connection can perform fine in an application if properly applied –

John Yurtin”

Very Important!

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Terminology

Peak Force (g’s)

Frequency Range (Hz)

Displacement

Direction of Motion (Random or Sinusoidal)

Peak Acceleration

Peak Velocity

PSD (Power Spectral Density) (g2/Hz)

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Specifications generally have a very specific “setup”.

Test Setups

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Numerous vibration profiles exist for testing connectors:– ESA 710

– USCAR

– GMI 12590

– ISO

– etc.

Some reasonable, some not

Each claims to be “The One”

Vibration tests have not been shown to correlate to field performance

A new test combines vibration with other environmental tests to correlate to “field” performance (called Field Correlated Life Test or FCLT)

FCLT test now specified by Delphi, Ford, and USCAR as an alternative connector validation test

Vibration Testing

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Inducing fretting corrosion inside connectors appears to be a black art

Common practice is to measure field vibration, then increase severity in the lab to shorten the test

These severe laboratory vibration schedules induce failures not seen in the field

– Severe wear

– Broken wires & early termination of test

Mild test schedules may not produce fretting in a poor design

Vibration Testing

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Lack of agreement among OEM’s causes suppliers to test to numerous vibration schedules

Industry agreement is urgently needed

Vibration specifications in progress:– GMW 3191

– USCAR PF-1

– ISO TC22//SC3/WG6

30 or more other standards organizations exist with similar interests

Tendency is for authors to guess at what the spec. should be. After it’s published, no one questions it.

Vibration Testing

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Are most connector troubles caused

by vibration?

Severe Vibration can cause harmful wear of contact interfaces

Mild vibration can cause fretting corrosion

Thermal changes can cause movement and fretting

Steps in the development of fretting corrosion on a tin‑plated terminal interface

Fretting Corrosion

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What about Plating and Lubricants? Gold Plating will result in improved performance

Gold to Tin is not recommended by Delphi and other industry experts. (AMP clearly does not recommend tin to gold interfaces!) (http://www.amp.com/products/technology/metrology.stm)

Lubricants can reduce the effect of fretting

Thermal changes can cause movement and fretting

Fretting Corrosion

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This is fretting corrosion!

Fretting Corrosion

Delphi ConfidentialSensor terminal after GMI12590

Fretting corrosion can be caused by micro-movement from temperature changes as well as from mechanical vibration.

Fretting Corrosion

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Symptoms of connections with fretting corrosion

– Problem disappears after connector is bumped

– Changing the device (sensor, computer, etc.) makes the problem go away temporarily

– Problem appears when the weather changes

Field Observations

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Other common troublemakers with similar symptoms– Fretting corrosion from thermal cycling

– High resistance crimps

– Damaged terminals

– Corrosion

– Cut Wires

– Contaminants in contact area (flux, oil, etc)

Fretting corrosion from vibration is not the cause of most connector problems

Field Observations

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Fretting corrosion found on a small percentage of field returns

Terminals with high contact force can still be functional when fretting debris is present

No relationship seen between mileage and degree of vibration-induced fretting wear

Worst looking fretting corrosion from actual vehicles looks milder than fretting corrosion from most lab vibration tests

Field Observations

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If a little vibration is good,

is a lot of vibration better?

Lab Variation

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LAB VIBRATION – ACCELERATED TESTS

Acceleration techniques for structural components do not apply to electrical contacts (unless different material data is used)

Typical Fatigue Life Curve For Metal

Fatigue Cycles

Str

ess

leve

l

Lab Variation

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Laboratory Fretting/Vibration Studies

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Lab Vibration Tests

Typical Fretting Pattern - Tin Plated Cu

Fretting Cycles

Co

nta

ct

Re

sis

tan

ce

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Lab Vibration

Most fretting degradation from vibration can be seen quickly (within minutes)

Additional vibration time can wear away the terminal substrate, but resistance may not increase

Some lab vibration test profiles cause cables to fracture and cause terminals to be ground into dust. Samples from field returns do not show the same failure modes

USCAR engine profile appears to match field performance better than most profiles

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Lab Vibration – Resistance Monitoring

Connections with fretting wear can have extremely unstable resistance

– Any movement of samples can “heal” the connections

Intermittency detection is helpful, but does not always detect fretting issues

Continuous voltage drop monitoring is useful, but “self-healing” will occur for high resistance connections

Continuous dry-circuit resistance monitoring is useful, but difficult

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Lab Vibration Fixtures

Fixture design is a major test variable

– Distance to nearest clamp

– Cable size or cable bundle size

– Slack in cable

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Summary

“Accelerated” vibration tests may not be realistic

Longer vibration tests may not be any better than short-duration tests

End-of-test measurements may not be useful, once samples have been moved

Fixturing has a strong effect on vibration test results

Some vibration tests have different failure modes than field samples

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Wish List For Vibration Testing

Documented relationship between existing lab profiles and field vibration performance

Documentation of acceleration factors used for vibration tests

More standardization of vibration profiles

Better methods for resistance monitoring

Standardization of fixturing methods