failure analysis: christmas lights. case description & hypotheses fracture of the bent brass...
Post on 29-Dec-2015
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Failure Analysis:Christmas Lights
Case Description & Hypotheses
• Fracture of the bent brass contact piece in various light bulb sockets
• The unbent contact never failed
• Brass composition from EDS:– Copper – 70%– Zinc – 30%
• Possible causes:– Overload– Fatigue– Corrosion
Visual Examination
Contact removed by force
Contact easily removedOriginal failed contact
Corroded Contact
Metallography(Longitudinal Sections)
Section of original broken part at fracture surface
Close-up of crack
Slip lines on unfractured
sample at bend
Slip lines on original
fractured sample
Fractography
Fracture surface of original failed contact
(600x)
Fracture surface of brass exemplar broken with overload (600x)
Conclusion• Stress Corrosion
Cracking (SCC)– Stress: bend– Corrosive
environment: Sulfur and Chlorine
• Solutions:- Coating/Electroplating- Socket design change- Annealing
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