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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.

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.

3D printing is believed to be driving the third industrial revolution. However, a scientometric visualizing of 3D printing research and an exploration its hotspots and emerging trends are lacking. This study aims to promote the theory development of 3D printing, help researchers to determine the research direction and provide a reference for enterprises and government to plan the development of 3D printing industry by a comprehensive understanding of the hotspots and trends of 3D printing.

Based on the theory of scientometrics, 2,769 literatures on the 3D printing theme were found in the Web of Science Core Collection’ Science Citation Index Expanded (SCI-EXPANDED) index between 1995-2016. These were analyzed to explore the research hotspots and emerging trends of 3D printing with the software CiteSpaceIII.

Hotspots had appeared first in 1993, grew rapidly from 2005 and peaked in 2013; hotspots in the “medical field” appeared earliest and have remained extremely active; hotspots have evolved from “drug”, “printer”, “rapid prototyping” and “3D printing” in the 1990s, through “laser-induced consolidation”, “scaffolds”, “sintering” and “metal matrix composites” in the 2000s, to the current hotspots of “stereolithography”, “laser additive manufacturing”, “medical images”; “3D bioprinting”, “titanium”, “Cstem cell” and “chemical reaction” were the emerging hotspots in recent years; “Commercial operation” and “fusion with emerging technology such as big data” may create future hotspots.

It is hard to avoid the possibility of missing important research results on 3D printing. The relevant records could be missing if the query phrases for topic search do not appear in records. Besides, to improve the quality of data, this study selected articles and reviews as the research objects, which may also omit some records.

First, this is the first paper visualizing the hotspots and emerging trends of 3D printing using scientometric tools. Second, not only “burst reference” and “burst keywords” but also “cluster” and “landmark article” are selected as the evaluation factors to judge the hotspots and trends of a domain comprehensively. Third, overall perspective of hotspots and trends of 3D printing is put forward for the first time.

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.

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.

The purpose of this paper is to explore the effect of different parameter configurations of oscillation amplitude, welding speed, and normal force at 478 K (400°F) on the linear welding density of stainless steel 316L annealed utrasonically consolidated (UC) samples, and present an optimum parameter set based upon maximum linear welding density criteria.

The paper describes the application of analysis of variance to different experimental designs in order to compare factor effects and obtain the optimum linear welding density parameter set for the ultrasonic consolidation of stainless steel 316L annealed samples.

This work includes experimental results at assessing the explained variation due to factor effects on linear welding density, the statistical significance of these factors, and the combination of UC process parameters that maximizes linear welding density in stainless steel 316L annealed samples.

The paper presents results obtained with a specific UC system, a standard sample configuration, and relatively constant frictional conditions.

This work is a first step towards a reproducible UC of stainless steel 316L foils with high linear welding density.

The purpose of this paper is to identify the key parameters that control the bonding formation of foils by the ultrasonic consolidation (UC) process and to build the correlations among process operating conditions and key control parameters through the concept of “process map”.

The concept of “process map” is proposed based on the diffusion bonding mechanism for the UC process, and numerical simulations have been applied to the UC process to predict peak temperature and plastic strain at the contact interface by considering a wide range of process operating conditions.

This map reveals that the formation of bonding among foils by the UC process requires a good match between temperature and plastic deformation at the contact interface. This limits the process operating window to a narrow region in the strain – temperature coordinate system.

This work has identified the underlying mechanism for bonding formation and the key control parameters of the UC process. The concept of “process map” for the UC process was developed, which allows the process optimization through two critical process control parameters of temperature and plastic strain at the contact interface instead of five operating conditions.

This study aims to outline the current challenges in ultrasonic additive manufacturing (AM). AM has revolutionized manufacturing and offers possible solutions when conventional techniques reach technological boundaries. Ultrasonic additive manufacturing (UAM) uses mechanical vibrations to join similar or dissimilar metals in three-dimensional assemblies. This hybrid fabrication method got attention due to minimum scrap and near-net-shape products.

This paper reviews significant UAM areas in process parameters such as pressure force, amplitude, weld speed and temperature. These process parameters used in different studies by researchers are compared and presented in tabular form. UAM process improvements and understanding of microstructures have been reported. This review paper also enlightens current challenges in the UAM process, process improvement methods such as heat treatment methods, foil-to-foil overlap and sonotrode surface roughness to increase the bond quality of welded parts.

Results showed that UAM could solve various problems and produce net shape products. It is concluded that process parameters such as pressure, weld speed, amplitude and temperature greatly influence weld quality by UAM. Post-weld heat treatment methods have been recommended to optimize the mechanical strength of ultrasonically welded joints process parameters. It has been found that the tension force is vital for the deformation of the pre-machined structures and for the elongation of the foil during UAM bonding. It is recommended to critically investigate the mechanical properties of welded parts with standard test procedures.

This study compiles relevant research and findings in UAM. The recent progress in UAM is presented in terms of material type, process parameters and process improvement, along with key findings of the particular investigation. The original contribution of this paper is to identify the research gaps in the process parameters of ultrasonic consolidation.

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.

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.

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.

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.

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.

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.

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.