Scanning Electron Microscope (SEM) equipped with Energy-dispersive X-ray (EDX) Detector SEM – typical magnification range used : 35 – 10,000X Singapore Test Services Advancing Towards New Frontiers 1
Ductile Fracture Features Singapore Test Services Advancing Towards New Frontiers 2
Brittle Fracture Features Singapore Test Services Advancing Towards New Frontiers 3
Fatigue Failure (Brittle) Features Singapore Test Services Advancing Towards New Frontiers 4
Features of Chloride-induced Stress Corrosion Cracking (CSCC) C o u n t s 5 0 0 0 C 4 0 0 0 3 0 0 0 F e 2 0 0 0 C r 1 0 0 0 O S i F e K C l F e S C a M g A l C d T i C r N a N i 0 2 4 6 8 E n e r g y ( k e V ) Singapore Test Services Advancing Towards New Frontiers 5
EDX Analysis for Identification of Materials Cu-Zn alloy – Brass Wear debris for material identification Fe-C-Cr-Mn alloy – Low Alloy Steel Singapore Test Services Advancing Towards New Frontiers 6
EDX Analysis for Identification of Contaminants Clean, normal surface region Surface with cracks and contamination Cracked, contaminated surface region Singapore Test Services Advancing Towards New Frontiers 7
Quantitative Chemical Composition Analysis Arc-spark Spectroscopy Positive Material Identification Drillings for “Wet’ Analysis Singapore Test Services Advancing Towards New Frontiers 8
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Tensile Testing Singapore Test Services Advancing Towards New Frontiers 11
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Hardness Testing Impact Testing Singapore Test Services Advancing Towards New Frontiers 13
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Metallography Cut-off Machine C UTTING Mounted specimens M OUNTING P OLISHING M ICROSCOPY Automatic Optical Microscope Grinder/Polisher Mag. Range: 50 – 1,000X Singapore Test Services Advancing Towards New Frontiers 16
As-received bolt sample Metallographic Prep. of a Bolt Sample After sectioning longitudinally After mounting, grinding & polishing After etching Singapore Test Services Advancing Towards New Frontiers 17
Optical Microscope Examination of Bolt Sample Threads Crest Root Singapore Test Services Advancing Towards New Frontiers 18
Microindentation Hardness Testing Singapore Test Services Advancing Towards New Frontiers 19
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Brittle versus Ductile Fracture Brittle Ductile Significant deformation Little or no deformation Singapore Test Services Advancing Towards New Frontiers 21
Ductile Fracture – SEM Fractography Singapore Test Services Advancing Towards New Frontiers 22
Ductile Fracture – Microstructural Features Singapore Test Services Advancing Towards New Frontiers 23
Example of a shaft that had Service Loading fractured in a ductile manner based on visual, SEM and Within Limit Exceeded Limit metallographic examinations (2) Failure due to (1) Failure due to non- combination of non-compliant compliant material. material and non-compliant Below spec loading. Use compliant material. Correct both conditions. Tensile Strength (4) Possibility of (3) Failure due to overload. inadequate design. Operate within specified limit; Meets spec Failure history would how about using higher reveal multiple failures – strength material? review design. The four possible failure situations will each require corrective actions or recommendations different from the others. Therefore, it is important to correctly diagnose the cause(s) of failure for the appropriate corrective action to be taken. Singapore Test Services Advancing Towards New Frontiers 24
Summary Do not jump to conclusions. Rather, have a mental workout – 1. apply critical thinking, explore all the possibilities, and form the hypotheses. 2. Perform lab investigation in accordance with established practices. Consult authoritative publications for technical information/data. 3. Do the background information and the findings/evidence from lab investigations support the hypotheses? Singapore Test Services Advancing Towards New Frontiers 25
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