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Ultrasonic bonding of thin foils has been recently introduced to rapid prototyping of complex-shaped and/or internally structured layered parts. This article provides the mechanical analysis of an elementary ultrasonic spot welding process of a metal foil on a previously deposited substrate. A 2-D, quasi-static/dynamic, elasto-plastic numerical model of the stress/strain field is developed by finite element analysis. Its frictional boundary conditions at the foil/substrate interface are described via a simpler plain stress, static analytical formulation, and identified experimentally by strain measurements on the substrate surface, adjacently to the ultrasonic probe. The calibrated computational simulation is validated in the laboratory and applied in studying the elastic stress concentrations, plastic deformation initiation and propagation patterns, the slippage at the interface surface and the dynamic effects of ultrasonic loading on the bonding process. This mechanical model is suitable for analysis of multi-joint ultrasonic rapid prototyping and its applications in fabrication of multi-material, functional internal structures with embedded components.

A new copper-catalyzed oxysulfenylation reaction of enolates with sodium sulfinates has been disclosed. A series of sulfenylated heterocycles including four- and seven-membered cyclic ether were obtained in mild to good yields. This reaction is proposed to go through a radical process, and the sulfur radical (RS(•)) may be a reactive species.

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A palladium-catalyzed multicomponent reaction (MCR) of propargylic carbonates with isocyanides is reported. Remarkably, the orderly insertion of isocyanides affords two types of valuable N-heterocyclic products (Z)-6-imino-4,6-dihydro-1H-furo[3,4-b]pyrrol-2-amines and (E)-5-iminopyrrolones in high yields. Systematic analysis of the reaction conditions indicates that the selectivity of these N-heterocyclic products can be controlled by ligands and temperature.