Ultrasonic additive manufacturing (UAM) is a solid state manufacturing process for joining thin metal tapes using principles of ultrasonic metal welding. The process operates at low temperatures, enabling dissimilar material welds without generating harmful intermetallic compounds. In this study, a 9 kW UAM system was used to create joints of Al 1100 and commercially pure titanium. Viable process parameters were identified through pilot weld studies via controlled variation of weld force, amplitude and weld speed. Push-pin delamination tests and shear tests were performed, comparing as-built, heat treated and spark plasma sintering treated samples. Heat treated and spark plasma sintering treated samples yielded mechanical strengths over twice that of as-built samples. Electron backscatter diffraction measurements show that deformation and grain refinement only take place in the aluminium layers. Heat treated samples exhibit a thin intermetallic layer, which is hypothesised as constraining the interface, leading to the improved strength.
Ultrasonic additive manufacturing (UAM) has proven useful in the solid-state, low tempe' rature fab? ication of layered solid metal structures. It is necessary to optimize the various process variables that affect the quality of bonding between layers through investigation of the mechanical .strength of various UAM builds. We investigate the effect of the process parameters tack force, weld force, oscillation amplitude, and weld rate on the ultimate shear strength (USS) and ultimate transverse tensile strength (UTTS) of 3003-H/8 aluminum UAM built samples. A multifactorial experiment was designed and an analysis of variance was performed to obtain an optimal set of process parameters for maximizing mechanical strength for the tested factors. The statistical analyses indicate that a relatively high mechanical strength can be achieved with a process window bounded by a 350 N tack force, 1000 N weld force, 26 nm oscillation amplitude, and about 42 mmis weld rate. Optical analyses of bond characterization did not show a consistent correlation linking linear weld density and bonded area of fractured surfaces to mechanical strength. Therefore, scanning electronmicroscopy (SEM) was conducted on fractured samples showing a good correlation between mechanical strength and area fraction that shows ductile failure.
Ultrasonic additive manufacturing (UAM) is a solid state manufacturing process that combines additive joining of thin metal tapes and subtractive computer numerical control milling operations to generate near-net shape metallic parts. We conducted a design of experiments study with the goal to optimize UAM process parameters for aluminum 6061. Weld force, weld speed, amplitude, and temperature were varied based on a Taguchi L18 experimental design matrix and tested for mechanical strength using a shear test and a comparative push-pin test. Statistical methods including analysis of variance (ANOVA), mean effects plots, and interaction effects plots were conducted to determine optimal process parameters. Results indicate that weld amplitudes of 32.76 lm and weld speeds of 84.6 mm/s yield maximum mechanical strength while temperature and force are statistically insignificant for the parameter levels tested. Annealing of cold-worked foil stock produces a 13% strength increase for UAM samples over homogeneous annealed material.
Purpose Ultrasonic additive manufacturing (UAM) is a fabrication technology based on ultrasonic metal welding. As a solid-state process, temperatures during UAM fabrication reach a fraction of the melting temperatures of the participating metals. UAM parts can become mechanically compliant during fabrication, which negatively influences the ability of the welder to produce consistent welds. This study aims to evaluate the effect of weld power on weld quality throughout a UAM build, and develop a new power-compensation approach to achieve homogeneous weld quality. Design/methodology/approach The study utilizes mechanical push-pin testing as a metric of delamination resistance, as well as focused ion beam and scanning electron microscopy to analyze the interface microstructure of UAM parts. Findings Weld power was found to negatively affect mechanical properties and microstructure. By keeping weld power constant, the delamination energy of UAM coupons was increased 22 per cent along with a consistent grain structure. As a result, to ensure constant properties throughout UAM component construction, maintaining weld power is preferable over the conventional strategy based on amplitude control. Research limitations/implications Further characterization could be conducted to evaluate the power control strategy on other material combinations, though this study strongly suggests that the proposed approach should work regardless of the metals being welded. Practical implications The proposed power control strategy can be implemented by monitoring and controlling the electrical power supplied to the welder. As such, no additional hardware is required, making the approach both useful and straightforward to implement. Originality/value This research paper is the first to recognize and address the negative effect of build compliance on weld power input in UAM. This is also the first paper to correlate measured weld power with the microstructure and mechanical properties of UAM parts.
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