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This study investigated material flow behaviour in similar aluminium alloy and magnesium alloy sheet lap welds produced by friction stir spot welding. The material flows around the tool pin and shoulder were visualised through the tracer material technique, and schematic illustrations were made to clarify the induced material flow direction and intensity. The material flow observations described that the pin part provided the outward spinning motion of the material, while the shoulder part generated a centrifugal effect at the edge for downward flow/hooking. Induced material flow intensity suggested that dominant flow patterns near the shoulder edge were observed for the similar Al welds, whereas high intensity outward spinning flows at the pin periphery for the similar Mg welds. As a result, the material flow under the pin and shoulder of the tool explained that the morphology of the failure mode was highly dependent on the tool geometry and the alloy material adopted.

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BackgroundThe WHO surgical safety checklist (SSC) is known to prevent postoperative complications; however, strategies for effective implementation are unclear. In addition to cultural and organizational barriers faced by high-income countries, resource-constrained settings face scarcity of durable and consumable goods. We used the SSC to better understand barriers to improvement at a trauma hospital in Battambang, Cambodia.MethodsWe introduced the SSC and trained data collectors to observe surgical staff performing the checklist. Members of the research team observed cases and data collection. After 3 months, we modified the data collection tool to focus on infection prevention and elicit more accurate responses.ResultsOver 16 months we recorded data on 695 operations (304 cases using the first tool and 391 cases with the modified tool). The first tool identified five items as being in high compliance, which were then excluded from further assessment. Two items—instrument sterility confirmation and sponge counting—were identified as being misinterpreted by the data collectors’ tool. These items were reworded to capture objective assessment of task completion. Confirmation of instrument sterility was initially never performed but rectified to >95% compliance; sponge counting and prophylactic antibiotic administration were consistently underperformed.ConclusionsStaff complied with communication elements of the SSC and quickly adopted process improvements. The wording of our data collection tool affected interpretation of compliance with standards. Material resources are not the primary barrier to checklist implementation in this setting, and future work should focus on clarification of protocols and objective confirmation of tasks.

Friction stir spot welding (FSSW), a solid state welding process, can join materials that are difficult to joint by fusion welding processes. In this study, similar FSSW of lightweight alloy sheets, such as aluminium and magnesium alloys, was performed using tools without thread. The histories of vertical plunge load applied to lapped sheets and the temperature distribution around the stirred surface of the upper positioned sheet during friction stirring were examined. Friction stir spot welding characteristics were discussed regarding the lap shear failure load and fractographic observations after tensile shear tests. A retracted tool produced the highest lap shear failure load for similar aluminium welds, while a pin tool produced the highest lap shear failure load for similar magnesium welds. The failure mode that brought a combination of shear and pullout fracture produced the highest lap shear failure load, which was closely related to the geometry of the tool that developed the enlarged fracture path.

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