ADVANCED MATERIALS & PROCESSES | OCTOBER 2025 22 of a single-family home in Minnesota, causing $85,000 in damages. The bathroom had been modified as part of a remodeling project completed approximately two years prior to the leak. The project was managed by a general contractor who had hired a plumbing company (the installer) to complete a tub-to-shower conversion as part of the job. The leak that caused the damages emanated from a fitting that connected a hot water pipe to a mixing valve for the subject shower (Fig. 1). The crux of the product-liability claim may be summarized as follows: The homeowner (plaintiff) believes their house flooded due to a product failure that should not have happened. The manufacturer of the fitting (defendant and third-party plaintiff) said the product would not have failed had it been used in a proper environment and installed correctly—and will sue any party related to the allegedly improper installation. The general contractor (defendant) asserted that they simply hired a plumbing sub- contractor to do the job and had nothing to do with the poor outcome. Finally, the installer (defendant) said they selected a product marketed for the application and that they installed it properly, noting that there was nothing remarkable about this installation. STRESS CORROSION CRACKING During the ensuing engineering investigation, a through-wall crack was discovered in the fitting. The failure mechanism for the crack was stress corrosion cracking. The following physical features provided evidence of SCC as the fracture mechanism: A throughwall, brittle crack (Fig. 2); secondary cracks at the interior surface of the fitting (Fig. 3); fracture progression from the fitting interior toward the fitting exterior (Fig. 4); microscopically faceted fracture features (Fig. 5); and a transgranular, branched crack morph- ology (Figs. 3 and 5). The SCC failure mechanism requires three prerequisite factors, and the relative magnitude of each factor affects the propensity for a failure to occur[3]: Fig. 2 — Through-wall crack in fitting as viewed at the exterior surface (left) and the interior surface (right). Fig. 3 — Secondary cracks as viewed at the fitting interior surface by SEM (top two images) and in a prepared metallographic section using light microscopy (bottom two images). Fig. 4 — Fracture surface for through-wall crack in as-opened condition (upper left) and after cleaning (upper right). Bottom images show SEM-REF images accentuating directional markings on fracture surface. Annotated arrows indicate local directions of crack progression.
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