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Recently, a number of research projects have been focused on an emerging additive manufacturing process, termed ultrasonic consolidation (UC). The purpose of this paper is to present an analytical energy model aimed at investigating the effects of process parameters on bond formation in UC.

In the model, two factors are defined, energy input to the workpiece within a single cycle of ultrasonic vibration (E₀) and total energy input to the workpiece (E_t), to evaluate to the magnitude of transmitted energy into the workpiece during UC.

It is found that linear weld density, E₀ and E_t are affected by process parameters in similar manners.

The current model is developed based on several simplifying assumptions, and energy dissipation and bond degradation during UC are not considered in the model.

The current model gives a useful understanding of the effects of process parameter on the bond formation in UC from an energy point of view.

Ultrasonic consolidation (UC) is a novel additive manufacturing process developed for fabrication of metallic parts from foils. While the process has been well demonstrated for part fabrication in Al alloy 3003, some of the potential strengths of the process have not been fully explored. One of them is its suitability for fabrication of parts in multi‐materials. This work aims to examine this aspect.

Multi‐material UC experiments were conducted using Al alloy 3003 foils as the bulk part material together with a number of engineering materials (foils of Al‐Cu alloy 2024, Ni‐base alloy Inconel 600^® AISI 347 stainless steel, and others). Deposit microstructures were studied to evaluate bonding between various materials.

It was found that most of the materials investigated can be successfully bonded to alloy Al 3003 and vice versa. SiC fibers and stainless wire meshes were successfully embedded in an Al 3003 matrix. The results suggest that the UC process is quite suitable for fabrication of multi‐material structures, including fiber‐reinforced metal matrix composites.

This work systematically examines the multi‐material capability of the UC process. The findings of this work lay a strong foundation for a wider and more efficient commercial utilization of the process.

This paper aims to comprehensively review ultrasonic additive manufacturing (UAM) process history, technology advancements, application areas and research areas. UAM, a hybrid 3D metal printing technology, uses ultrasonic energy to produce metallurgical bonds between layers of metal foils near room temperature. No melting occurs in the process – it is a solid-state 3D metal printing technology.

The paper is formatted chronologically to help readers better distinguish advancements and changes in the UAM process through the years. Contributions and advancements are summarized by academic or research institution following this chronological format.

This paper summarizes key physics of the process, characterization methods, mechanical properties, past and active research areas, process limitations and application areas.

This paper reviews the UAM process for the first time.

The increasing interest in engineering structures made from multiple materials has led to corresponding interest in technologies, which can fabricate multi‐material parts. The purpose of this paper is to further explore of the multi‐material fabrication capabilities of ultrasonic consolidation (UC).

Various combinations of materials including titanium, silver, tantalum, aluminum, molybdenum, stainless steel, nickel, copper, and MetPreg^® were ultrasonically consolidated. Some of the materials were found to be effective as an intermediate layer between difficult to join materials. Elemental boron particles were added in situ between selected materials to modify the bonding characteristics. Microstructures of deposits were studied to evaluate bond quality.

Results show evidence of good bonding between many combinations of materials, thus illustrating increasing potential for multi‐material fabrication using UC.

Multi‐material fabrication capabilities using UC and other additive manufacturing processes is a critical step towards the realization of engineering designs which make use of functional material combinations and optimization.

The purpose of this paper is to investigate the effectiveness of locking or staking of fasteners with epoxy material systems to prevent loss of preload in aerospace environments.

A quantitative experimental method is adopted to evaluate epoxy material systems for staking of fastener assemblies subjected to varying dynamic and thermal loads. A statistical design of experiments is employed to probe specific design parameters.

Results show that epoxy application can provide satisfactory fastener locking under a variety of service conditions. It is found that: Epon 828 epoxy provides superior fastener locking compared to 3M Scotch‐Weld Epoxy 2216; epoxy application around screw threads is more effective than application around screw head; and abrading the plate surfaces with 180 grit SiC paper is not an effective or useful surface preparation technique.

The paper is limited to two commercial epoxy material systems and does not consider important qualitative considerations for industrial use such as cure time and viscosity.

This and future paper may form the basis of new standards for epoxy staking in the global aerospace industry.

This paper is believed to be one of the very few original experimental studies of fastener staking available in the open literature.

The purpose of this paper is to focus on the changing dynamics of the ultrasonic consolidation (UC) process due to changes in substrate geometry. Past research points to a limiting height to width ranging from 0.7 to 1.2 on build features.

Resonances of a build feature due to a change in geometry are examined and then a simple non‐linear dynamic model of the UC process is constructed that examines how the geometry change may influence the overall dynamics of the process. This simple model is used to provide estimates of how substrate geometry affects the differential motion at the bonding interface and the amount of energy emitted by friction change due to build height. The trends of changes in natural frequency, differential motion, and frictional energy are compared to experimental limits on build height.

The paper shows that, at the nominal build, dimensions of the feature the excitation caused by the UC approach two resonances in the feature. In addition trends in regions of changes of differential motion, force of friction, and frictional energy follow the experimental limit on build height.

This paper explores several aspects of the UC process not currently found in the current literature: examining the modal properties of build features, and a lumped parameter dynamic model to account for the changes in of the substrate geometry.

The primary objective of this investigation is to optimize the constricted arc tungsten inert gas (CA-TIG) welding parameters specifically welding current (WC), arc constriction current (ACC), ACC frequency (ACCF) and CA traverse speed to maximize the tensile properties of thin Inconel 718 sheets (2 mm thick) using a statistical technique of response surface methodology and desirability function for gas turbine engine applications.

The four factor – five level central composite design (4 × 5 – CCD) matrix pertaining to the minimum number of experiments was chosen in this investigation for designing the experimental matrix. The techniques of numerical and graphical optimization were used to find the optimal conditions of CA-TIG welding parameters.

The thin sheets of Inconel 718 (2 mm thick) can be welded successfully using CA-TIG welding process without any defects. The joints welded using optimized conditions of CA-TIG welding parameters showed maximum of 99.20%, 94.45% and 73.5% of base metal tensile strength, yield strength and elongation.

The joints made using optimized CA-TIG welding parameters disclosed 99.20% joint efficiency which is comparatively 20%–30% superior than conventional TIG welding process and comparable to costly electron beam welding and laser beam welding processes. The parametric mathematical equations were designed to predict the tensile properties of Inconel 718 joints accurately with a confidence level of 95% and less than 4.5% error. The mathematical relationships were also developed to predict the tensile properties of joints from the grain size (secondary dendritic arm spacing-SDAS) of fusion zone microstructure.

The purpose of this paper is to examine the formation of surface damage associated with the ultrasonic consolidation (UC) of single ply 150 μm thick 3003‐H18 foil to a 3003‐18 build plate and the relationship between the development of this damage state with the linear weld density (LWD) achieved during consolidation.

The influence of the consolidation control variables on the area fraction of the sonotrode induced top foil surface damage is established through application of a full factorial three‐level design‐of‐experiment methodology, the control variables limits being fixed by the capability of the UC system.

Detailed analysis of the foil top surface structure after consolidation reveals the presence of two characteristic, damaged and undamaged, regions. The former corresponded to plastically deformed areas, these being formed as a result of interaction of the foil top surface with the sonotrode, while the latter corresponded to the original foil surface. Sonotrode normal load, vibrational amplitude and its rotational velocity are found to have an interdependent affect on the development of the sonotrode‐induced top surface damage. Top surface damage initiates upon impression of the sonotrode into the foil surface followed by the commencement of oscillatory and forward rotational motion of the sonotrode. Finally, evidence is presented that the degree of sonotrode induced top surface damage bears a direct relationship with the linear ultrasonic weld density developed at the foil‐build plate interface, increasing top surface damage being associated with increased LWD.

A linear relationship between the degree of bonding at the foil‐build plate interface and the plastically deformed area on the foil top surface is established, this correlation demonstrating that bond formation between foils during UC depends on effective frictional conditions at the sonotrode‐foil interface.

The purpose of this paper is to provide a systematic analysis about the effects of additive manufacturing (AM) technology adoption on supply chain management (SCM) processes and SCM components in an engineer-to-order environment.

Based on two explorative case studies from the hearing systems industry, the impact of AM technology adoption on SCM processes and SCM components is investigated. General systems theory and the contingency approach serve as theoretical underpinning.

Not only the internal processes and management activities, e.g. in manufacturing and order fulfillment, of producers are affected by a changeover to AM, but also the SCM processes and components relating to the supply and demand side of a firm’s supply chain. Endogenous and AM technology-related factors are contingency factors that help to explain differing effects of AM technology adoption on SCM processes and SCM components.

It is proposed that AM’s ability to economically build custom products provides the potential to alleviate the common dilemma between product variety and scale economies.

Manufacturing firms are encouraged to consider the potential effects of AM on SCM processes and SCM components when deciding whether to adopt AM technologies in the production of industrial parts.

The research adds to the widely unexplored effects that AM technology usage in customized parts production has on SCM processes and components. Moreover, the general lack of case studies analyzing the implications of AM technology adoption from a supply chain perspective is addressed. The resulting propositions may serve as a starting point for further research on the impact of AM in engineer-to-order supply chains.

Ultrasonic additive manufacturing (UAM) is a rapid prototyping process through which multiple thin layers of material are sequentially ultrasonically welded together to form a finished part. While previous research into the peak temperatures experienced during UAM have been documented, a thorough examination of the heating and cooling curves has not been conducted to date.

For this study, UAM weldments made from aluminum 3003‐H18 tapes with embedded Type‐K thermocouples were examined. Finite element modeling was used to compare the theoretical thermal diffusion rates during heating to the observed heating patterns. A model was used to calculate the effective thermal diffusivity of the UAM build on cooling based on the observed cooling curves and curve fitting analysis.

Embedded thermocouple data revealed simultaneous temperature increases throughout all interfaces of the UAM build directly beneath the sonotrode. Modeling of the heating curves revealed a delay of at least 0.5 seconds should have existed if heating of lower interfaces was a result of thermal diffusion alone. As this is not the case, it was concluded that ultrasonic energy is absorbed and converted to heat at every interface beneath the sonotrode. The calculated thermal diffusivity of the build on cooling was less than 1 percent of the reported values of bulk aluminum, suggesting that voids and oxides along interfaces throughout the build may be inhibiting thermal diffusion through thermal contact resistance across the interface.

This work systematically analyzed the thermal profiles that develop during the UAM process. The simultaneous heating phenomenon presented here has not been documented by other research programs. The findings presented here will enable future researchers to develop more accurate models of the UAM process, potentially leading to improved UAM bond quality.