1. Failure Analysis: Christmas Lights

2. 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

3. Visual Examination Contact removed by force Contact easily removed Original failed contact Corroded Contact

4. 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

5. Fractography Fracture surface of original failed contact (600x) Fracture surface of brass exemplar broken with overload (600x)

6. Conclusion Stress Corrosion Cracking (SCC) –Stress: bend –Corrosive environment: Sulfur and Chlorine Solutions: - Coating/Electroplating -Socket design change -Annealing