Purpose
Ultrasonic additive manufacturing (UAM) is a solid-state joining technology used for three-dimensional printing of metal foilstock. The electrical power input to the ultrasonic welder is a key driver of part quality in UAM, but under the same process parameters, it can vary widely for different build geometries and material combinations because of mechanical compliance in the system. This study aims to model the relationship between UAM weld power and system compliance considering the workpiece (geometry and materials) and the fixture on which the build is fabricated.
Design/methodology/approach
Linear elastic finite element modeling and experimental modal analysis are used to characterize the system’s mechanical compliance, and linear system dynamics theory is used to understand the relationship between weld power and compliance. In-situ measurements of the weld power are presented for various build stiffnesses to compare model predictions with experiments.
Findings
Weld power in UAM is found to be largely determined by the mechanical compliance of the build and insensitive to foil material strength.
Originality/value
This is the first research paper to develop a predictive model relating UAM weld power and the mechanical compliance of the build over a range of foil combinations. This model is used to develop a tool to determine the process settings required to achieve a consistent weld power in builds with different stiffnesses.
Ultrasonic additive manufacturing (UAM) has garnered significant interest in the aerospace and automotive industries for its structural lightweighting and multi-material joining capabilities. This paper details the investigation on the effect of process variables on the resultant microstructure of the built-up part using UAM for aluminum 6061. The degree of recrystallization is quantified, and an energy metric, defined using the Read–Shockley relationship, is used to build an energy map of the welded part. The total energy stored in the resultant weld interface microstructure is quantified as a fraction of the input and is found to be about 0.1%. The width, average grain size, and percentage of High Angle Grain Boundaries (% HAGB) were used to compare microstructures of builds prepared using different processing conditions. Welding subsequent weld layers was not found to affect the previous welded layers. The effect of vibration amplitude and travel speed on the as-built microstructure were investigated, and the width of the interface was found to more than double when the weld amplitude is increased from the threshold value for joining (23 μm) and then stabilize at higher weld amplitudes. A better understanding of the effect of processing parameters on as-welded microstructures will assist parameter selection for UAM.
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