A study on ultrasonic energy assisted metal processing : its correeltion with microstructure and properties, and its application to additive manufacturing.

Additive manufacturing or 3d printing is the process of constructing a 3-dimensional object layer-by-layer. This additive approach to manufacturing has enabled fabrication of complex components directly from a computer model (or a CAD model). The process has now matured from its earlier version of being a rapid prototyping tool to a technology that can fabricate service-ready components. Development of low-cost polymer additive manufacturing printers enabled by open source Fused Deposition Modeling (FDM) printers and printers of other technologies like SLA and binder jetting has made polymer additive manufacturing accessible and affordable. But the metal additive manufacturing technologies are still expensive in terms of initial system cost and operating costs. With this motivation, this dissertation aims to develop and study a novel metal additive manufacturing approach called Acoustoplastic Metal Direct-Write (AMD) that promises to make metal additive manufacturing accessible and affordable. The process is a voxel based additive manufacturing approach which uses ultrasonic energy to manipulate and deposit material. This dissertation demonstrates that the process can fabricate near-net shape metal components in ambient conditions. This dissertation investigates two key phenomenon that govern the process. The first phenomenon investigated is ultrasonic/acoustic softening. It is the reduction in yield stress of the metals when being deformed under simultaneous application of ultrasonic energy. A detailed analysis of the stress and microstructure evolution during ultrasonic assisted deformation has been presented in this dissertation. Crystal plasticity model modified on the basis of microstructure analysis has been developed to predict the stress evolution. The 2nd phenomenon investigated is ultrasonic energy assisted diffusion that enables the bonding of voxels during the AMD process. High resolution Transmission Electron Microscopy (HRTEM) and Energy Dispersive Spectroscopy (EDS) analysis has been used to quantify this phenomenon and also distinguish the process mechanics from other foil or sheet based ultrasonic joining processes

Improving Linear Weld Density in Ultrasonically Consolidated Parts

Ultrasonic consolidation is a novel additive manufacturing process with immense potential for fabrication of complex shaped three-dimensional metallic objects from metal foils. The proportion of bonded area to unbonded area along the layer interface, termed linear weld density (LWD), is perhaps the most important quality attribute of ultrasonically consolidated parts. Part mechanical properties largely depend on LWD and a high level of LWD must be ensured in parts intended for load-bearing structural applications. It is therefore necessary to understand what factors influence LWD or defect formation and devise methods to enhance bond formation during ultrasonic consolidation. The current work examines these issues and proposes strategies to ensure near 100% LWD in ultrasonically consolidated aluminum alloy 3003 parts. The work elucidates the effects of various process parameters on LWD and a qualitative understanding of the effects of process parameters on bond formation during ultrasonic consolidation is presented. The beneficial effects of using elevated substrate temperatures and its implications on overall manufacturing flexibility are discussed. A preliminary understanding of defect morphologies and defect formation is presented, based on which a method (involving surface machining) for minimizing defect incidence during ultrasonic consolidation is proposed and demonstrated. Finally, trade-offs between part quality and build time are discussed.Mechanical Engineerin

Performance of Stainless Steel AlSi 304 Wire Reinforced Metal Matrix Composites Made Using Ultrasonic Additive Manufacturing in Bending

Ultrasonic additive manufacturing (UAM) is a solid-state additive and subtractive manufacturing process that utilizes ultrasonic energy to produce layered metallic parts. The process is easily extended to create advanced multi-material structures, e.g., metal matrix composites, functionally graded metallic components, and shape memory alloys. This research utilizes a three point bending test to compare the elastic modulus in metal matrix composites (MMC’s) specimens consisting of stainless steel wire reinforcements with an aluminum matrix to unreinforced test specimens; both specimens are produced by UAM. In the MMC the volume fraction of wire is relatively low, 0.77%, yet yields an average increase in modulus of 8.9%.Mechanical Engineerin

Rapid manufacturing- state of the art, analysis and future perspectives

Layer based manufacturing system often referred to as Rapid Prototyping (RP) have been in existence for 22 years, in the past 5 years Rapid Manufacturing (RM) has emerged from these RP systems to produce functional and structural customer focused end use components and products. This keynote paper will review the current range of technologies for metallic systems, it will also evaluate the operating principles, features, potential and limitations of current commercially available systems. Rapid Manufacture is increasingly being used for high value difficult to manufacture components with a new set of design rules required to fully exploit the RM systems inherent characteristics. A case studies approach will be used to show the benefits and pitfalls this new design freedom can provide designers

A Review of Layer Based Manufacturing Processes for Metals

The metal layered manufacturing processes have provided industries with a fast method to build functional parts directly from CAD models. This paper compares current metal layered manufacturing technologies from including powder based metal deposition, selective laser sinstering (SLS), wire feed deposition etc. The characteristics of each process, including its industrial applications, advantages/disadvantages, costs etc are discussed. In addition, the comparison between each process in terms of build rate, suitable metal etc. is presented in this paper.Mechanical Engineerin

Effect of Metallic Waste Addition on the Physical and Mechanical Properties of Cement-Based Mortars

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. This is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).This paper investigates the influence of the type and amount of recycled metallic waste on the physical and mechanical properties of cement-based mortars. The physical and mechanical properties of cement mortars, containing four different amounts of metallic waste (ranged 4 to 16% by cement weight), were evaluated by measuring the bulk density, total porosity, flexural and compressive resistance, and dynamic elastic modulus by ultrasonic tests. All the properties were measured on test specimens under two curing ages: 7 and 28 days. Additionally, the morphological properties and elemental composition of the cement and metallic waste were evaluated by using Scanning Electron Microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), and X-ray fluorescence (XRF). Main results showed that the addition of metallic waste reduced the bulk density and increased the porosity of the cement-based mortars. Furthermore, it was observed that flexural and compressive strength proportionally increased with the metallic waste addition. Likewise, it was proven that elastic modulus, obtained by compressive and ultrasonic tests, increases with the metallic waste amount. Finally, based on a probability analysis, it was confirmed that the addition of metallic waste did not present a significant effect on the mechanical performance of the cement-based mortars.Peer reviewedFinal Published versio

Fundamental Understanding of Bond Formation During Solid State Welding of Dissimilar Metals

Dissimilar metal welds are used in a wide range of applications to effect light weighting and for corrosion resistance. While fusion welding techniques are limited in their ability to fabricate dissimilar metal welds, solid state welding techniques are limited in their ability to fabricate complex geometries with dissimilar metal combinations. Hence alternative techniques need to be explored to fabricate complex geometries with dissimilar metals welds in the solid state. Ultrasonic additive manufacturing in a solid state additive manufacturing process that combines ultrasonic welding with mechanized tape layering to fabricate dissimilar metal welds in the solid state. Though extensive feasibility studies have been performed to fabricate dissimilar metal welds using ultrasonic additive manufacturing, the fundamental mechanisms related to the bond formation mechanism are not fully understood. In this work multi scale characterization using scanning electron microscopy, electron backscatter diffraction, nano indentation and atom probe tomography was performed to rationalize the mechanism of bond formation in dissimilar metal welds. The fundamental questions that needed to be answered were Is possible for a solid state bond to form with extensive plastic deformation occurring only on one metal in a dissimilar metal combination The effect of plastic deformation on the oxide layer at the interface of dissimilar metal welds. To answer the above questions various dissimilar metal combinations (Steel-Ta) BCC-BCC, (Al-Ti) FCC-HCP, (Al-Steel) FCC-BCC were fabricated using ultrasonic additive manufacturing and characterized using the above-mentioned techniques. Bonded regions were characterized to study the role of plastic deformation by analyzing the micro texture developed at the interface. The general conclusion is the presence of a strong shear texture in the softer metal while the harder metal did not show any evidence of change in texture. To understand the effect of plastic deformation on the oxide dispersion atom probe tomography analysis was performed and the results indicate the possibility of oxide breakdown resulting in oxygen super saturation in the lattice. The bond formation is hypothesized to occur as a result of plastic deformation localized in the softer metal alone

Structurally Embedded Electrical Systems Using Ultrasonic Consolidation (UC)

Current research has demonstrated the use of Ultrasonic Consolidation (UC) to embed several USB-based sensors into aluminum, and is working toward embedding suites of sensors, heaters and other devices, connected via USB hubs, which can be monitored and controlled using an embedded USB capable processor. Additionally, the research has shown that electronics can be embedded at room temperature, but with some inter-layer delamination between the ultrasonically bonded aluminum layers. Embedding sensors and electronics at 300o F to overcome the delamination issues resulted in optimal bonding, and the sensors used thus far have functioned normally. Future investigation will explore other UC parameter combinations to ascertain the quality of embedding at lower temperatures.Mechanical Engineerin

Test and Evaluation of Ultrasonic Additive Manufacturing (UAM) for a Large Aircraft Maintenance Shelter (LAMS) Baseplate

Additive manufacturing is an exciting new manufacturing technology that could have application to Air Force Civil Engineer (CE) operations. This research replicates a Large Area Maintenance Shelter (LAMS) baseplate design for ultrasonic additive manufacturing (UAM). Due to production problems the test section was not built as designed. Instead, a smaller block of material was submitted for evaluation. After the UAM build, ultrasonic inspection was conducted to identify anomalies in the test piece. The results of this proof of concept study indicate that UAM is not yet ready for CE expeditionary applications requiring a high degree of mechanical strength. The machine failed to build a baseplate of the same dimensions as would be required for use in the field. Further, the test specimen produced using UAM had a substantial number of anomalies throughout the entire y-axis of orientation. As the technology continues to improve, UAM may produce welds of sufficient strength to support expeditionary structural applications