ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2025 25 that high dynamic stresses induced fatigue in the fuse pin[9]. This was considered the primary physical cause of failure of both fuse pins. Contributing physical causes were the fuse pin design and manufacture, leading to local stress concentrations due to the machining grooves, and OEM-determined non-classical crankshaft bending[9]. The probable root cause was inadequate knowledge of dynamic loads on the Boeing 747 engine pylons by assuming the loads TABLE 2 — INVASIVE FORENSIC METALLURGY IN ARCHAEOLOGY AND AEROSPACE Procedures Archaeology Aerospace Fractography after careful cleaning • Rarely done; often difficult due to fracture surface corrosion attack • Minimum sample size • Optical, including color photography • SEM to 2000‒5000× with conductive coating if necessary • Essential if component fractured or cracks can be opened up • Entire fracture surface if possible, or segments • Optical, including color photography • SEM with conductive coating if necessary • Quantitative if possible, notably fatigue fracture surfaces Metallography • Small samples; unetched and etched • OM color photographs, SEM with conductive coating if necessary • Alloy and any associated corrosion microstructures; SEM/EDS spot images and dot-map scans • Convenient sample sizes; unetched and etched • OM color photographs, SEM with conductive coating if necessary (adherent and diagnostic corrosion) • Alloy microstructures; possible SEM/EDS spot images and dot-map scans Chemical analyses • SEM/EDS semi-quantitative alloy composition analyses for main and minor elements • More accurate methods for trace elements and isotopes, e.g., an ICP type • XRD powdered corrosion products • SEM/EDS semi-quantitative alloy composition analyses for main and minor elements • Possible SEM/WDS quantitative alloy composition analyses to include trace elements • More accurate methods if needed, e.g., an ICP type Mechanical testing • Microhardness on metallographic samples • Hardness (steels); tensile, fracture toughness, fatigue, creep (if relevant and possible) Data analysis and reporting • Causes of any damages • Historical cultural aspects • CHM recommendations • Physical causes of damages and failures • Engineering culture-based root causes • Recommendations to operators and OEMs Key: CHM = cultural heritage management (restorations, if any and allowed, and conservation); EDS = energy dispersive x-ray spectroscopy; ICP = inductively coupled plasma (covering several methods/types); OEM = original equipment manufacturer; OM = optical microscopy; WDS = wavelength dispersive x-ray spectroscopy; XRD = x-ray diffraction. to be similar to those for the earlier Boeing 707 pylons[8,9]. This now-forbidden practice is called “grandfathering.” Remedial actions by the OEM included new design fuse pins, two extra connections between mid-spar pylon fittings, and increased sizes of these fittings[8,9]. INVASIVE: LIA PROVENANCING CHINESE BRONZES Lead isotope analysis (LIA) is a special chemical analysis category for provenancing ancient metallic artifacts, notably bronzes and silver alloys, and their smelting sites and mining ores[10,11]. However, LIA is subject to much interpretative discussion beyond the scope of the present article. The current situation, which in context implicitly includes the metallic artifacts, has been summarized by Pollard et al.[12]: “...when focused on a specific region and carried out in combination with a detailed holistic view of the
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