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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
Delphi Confidential3
Agenda
Most Important Comment Terminology Vibration Testing Fretting Corrosion Field Observations Lab Variation Lab Testing Factors In Vibration Issues Summary Wish List
Delphi Confidential4
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!
Delphi Confidential5
“ 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!
Delphi Confidential6
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)
Delphi Confidential8
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
Delphi Confidential9
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
Delphi Confidential10
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
Delphi Confidential
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
Delphi Confidential12
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
Delphi ConfidentialSensor terminal after GMI12590
Fretting corrosion can be caused by micro-movement from temperature changes as well as from mechanical vibration.
Fretting Corrosion
Delphi Confidential
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
Delphi Confidential
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
Delphi Confidential
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
Delphi Confidential
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
Delphi Confidential
Lab Vibration Tests
Typical Fretting Pattern - Tin Plated Cu
Fretting Cycles
Co
nta
ct
Re
sis
tan
ce
Delphi Confidential
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
Delphi Confidential
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
Delphi Confidential
Lab Vibration Fixtures
Fixture design is a major test variable
– Distance to nearest clamp
– Cable size or cable bundle size
– Slack in cable
Delphi Confidential
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
Delphi Confidential
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
Recommended