A. Bandyopadhyay, R.K. Panda, T.F. McNulty, F. Mohammadi, S.C. Danforth and A. Safari
Reviews the inherent advantages, i.e. design flexibility and processing, of manufacturing piezoelectric ceramics and composites with numerous architectures via rapid prototyping…
Abstract
Reviews the inherent advantages, i.e. design flexibility and processing, of manufacturing piezoelectric ceramics and composites with numerous architectures via rapid prototyping techniques. Reports on processing in which piezoelectric ceramics and composites with novel and conventional designs were fabricated using rapid prototyping techniques. Fused deposition of ceramics, fused deposition modeling, and Sanders prototyping techniques were used to fabricate lead‐zirconate‐titanate ceramics and ceramic/polymer composites via, first, direct fabrication and, second, indirect fabrication using either lost mold or soft tooling techniques.
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T.F. McNulty, F. Mohammadi, A. Bandyopadhyay, D.J. Shanefield, S.C. Danforth and A. Safari
A new family of thermoplastic binders has been developed for usage in fused deposition of ceramics (FDC). Mixtures were formulated consisting of a base binder, tackifier, wax, and…
Abstract
A new family of thermoplastic binders has been developed for usage in fused deposition of ceramics (FDC). Mixtures were formulated consisting of a base binder, tackifier, wax, and plasticizer. The resultant formulation was chosen based on mechanical, rheological, and thermal property requirements. A formulation consisting of 100 parts base binder (by weight), along with 20 parts tackifier, 15 parts wax, and five parts plasticizer exhibited an optimized compromise of mechanical, rheological, and thermal properties. This formulation was compounded with 55 vol. per cent lead zirconate titanate (PZT) powder, and extruded into filaments with a diameter of 1.75mm and a length of approximately 50 (+/‐10) cm. The resulting filaments were used to fabricate functional piezoelectric ceramic devices via FDC. The binder development process is described, along with the associated mechanical, rheological, and thermal property data.
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Jose F. Rodriguez, James P. Thomas and John E. Renaud
Fused‐deposition (FD) is a robotically controlled “fiber” extrusion process that produces a new class of materials with a variety of controllable mesostructural features related…
Abstract
Fused‐deposition (FD) is a robotically controlled “fiber” extrusion process that produces a new class of materials with a variety of controllable mesostructural features related to fiber layout and the presence of voids. Mesostructural features of importance to the stiffness and strength of unidirectionally extruded materials were characterized as a function of the processing variables. Samples were made using the Stratasys FDM1600 Modeler with the P400 acrylonitrile‐butadiene‐styrene plastic. Results showed that the void geometry/density and the extent of bonding between contiguous fibers depended strongly on the fiber gap and extrusion flow rate. Settings for minimum void and maximum fiber‐to‐fiber bonding were determined. Void and bond length densities in the plane transverse to the fiber extrusion direction varied from 4 to 16 per cent and 39 to 73 per cent respectively. The results quantify the important mesostructural features as a function of the FD process variables and are expected to find use with other FD materials.
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Mauricio E. Pilleux, Ahmad Safari, Mehdi Allahverdi, Youren Chen, Yicheng Lu and Mohsen A. Jafari
Three‐dimensional photonic bandgap (PBG) structures using alumina (Al2O3) as the high permittivity material were modeled and then the structures were fabricated by Fused…
Abstract
Three‐dimensional photonic bandgap (PBG) structures using alumina (Al2O3) as the high permittivity material were modeled and then the structures were fabricated by Fused Deposition of Multi‐materials (FDMM) technology. A finite element method and a real‐time electromagnetic wave propagation software were used to simulate and design the layered PBG structures for applications in the microwave frequency range. The modeling predicted a 3‐D photonic bandgap in the 16.5–23.5 GHz range. FDMM provides a computer‐controlled process to generate 3‐D structures, allowing high fabrication flexibility and efficiency. Electromagnetic measurements displayed the presence of a bandgap between 17.1–23.3 GHz, showing a good agreement with the predicted values. These PBG structures are potential candidates for applications in advanced communication systems.
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Anna Bellini, Lauren Shor and Selcuk I. Guceri
To shift from rapid prototyping (RP) to agile fabrication by broadening the material selection, e.g. using ceramics, hence improving the properties (e.g. mechanical properties) of…
Abstract
Purpose
To shift from rapid prototyping (RP) to agile fabrication by broadening the material selection, e.g. using ceramics, hence improving the properties (e.g. mechanical properties) of fused deposition modeling (FDM) products.
Design/methodology/approach
This paper presents the development of a novel extrusion system, based on the FDM technology. The new set‐up, consisting of a mini‐extruder mounted on a high‐precision positioning system, is fed with bulk material in granulated form, instead that with the more common filament.
Findings
Previous research showed that the applications of new materials with specific characteristics in a commercial FDM system are limited by the use of intermediate precursors, i.e. a filament. The new design described in this paper overcomes the problem thanks to the new feeding system.
Research limitations/implications
The work presented in this paper is only the starting point for further development. The new system design was tested and encouraging improvements of the final product were achieved. However, several parameters, e.g. size of the feeding granules, still need to be optimized.
Practical implications
This configuration opens up opportunities for the use of wider range of materials, making the FDM to become a viable alternative manufacturing process for specialty products.
Originality/value
The mini‐extruder deposition system developed in this study exploits the advantages of the RP technologies: ability to shorten the product design and development time; suitability for automation; and ability to build many geometrically complex shapes. Hence, applying the described technology, it will be possible to manufacture customer‐driven product with important cost and time (from design to final product) savings.
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M.A. Jafari, W. Han, F. Mohammadi, A. Safari, S.C. Danforth and N. Langrana
In this article we present the system that we have developed at Rutgers University for the solid freeform fabrication of multiple ceramic actuators and sensors. With solid free…
Abstract
In this article we present the system that we have developed at Rutgers University for the solid freeform fabrication of multiple ceramic actuators and sensors. With solid free form fabrication, a part is built layer by layer, with each layer composed of roads of material forming the boundary and the interior of the layer. With our system, up to four different types of materials can be deposited in a given layer with any geometry. This system is intended for fabrication of functional parts; therefore the accuracy and precision of the fabrication process are of extreme importance.
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N. Venkataraman, S. Rangarajan, M.J. Matthewson, B. Harper, A. Safari, S.C. Danforth, G. Wu, N. Langrana, S. Guceri and A. Yardimci
Fused deposition of ceramics (FDC) is a solid freeform fabrication technique based on extrusion of highly loaded polymer systems. The process utilizes particle loaded…
Abstract
Fused deposition of ceramics (FDC) is a solid freeform fabrication technique based on extrusion of highly loaded polymer systems. The process utilizes particle loaded thermoplastic binder feedstock in the form of a filament. The filament acts as both the piston driving the extrusion and also the feedstock being deposited. Filaments can fail during FDC via buckling, when the extrusion pressure needed is higher than the critical buckling load that the filament can support. Compressive elastic modulus determines the load carrying ability of the filament and the viscosity determines the resistance to extrusion (or extrusion pressure). A methodology for characterizing the compressive mechanical properties of FDC filament feedstocks has been developed. It was found that feedstock materials with a ratio (E/ηa) greater than a critical value (3×105 to 5×105 s‐1) do not buckle during FDC while those with a ratio less than this range buckle.
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Abstract
Purpose
Conventional machining methods for fabricating piezoelectric components such as ultrasound transducer arrays are time-consuming and limited to relatively simple geometries. The purpose of this paper is to develop an additive manufacturing process based on the projection-based stereolithography process for the fabrication of functional piezoelectric devices including ultrasound transducers.
Design/methodology/approach
To overcome the challenges in fabricating viscous and low-photosensitive piezocomposite slurry, the authors developed a projection-based stereolithography process by integrating slurry tape-casting and a sliding motion design. Both green-part fabrication and post-processing processes were studied. A prototype system based on the new manufacturing process was developed for the fabrication of green-parts with complex shapes and small features. The challenges in the sintering process to achieve desired functionality were also discussed.
Findings
The presented additive manufacturing process can achieve relatively dense piezoelectric components (approximately 95 per cent). The related property testing results, including X-ray diffraction, scanning electron microscope, dielectric and ferroelectric properties as well as pulse-echo testing, show that the fabricated piezo-components have good potentials to be used in ultrasound transducers and other sensors/actuators.
Originality/value
A novel bottom-up projection system integrated with tape casting is presented to address the challenges in the piezo-composite fabrication, including small curing depth and viscous ceramic slurry recoating. Compared with other additive manufacturing processes, this method can achieve a thin recoating layer (as small as 10 μm) of piezo-composite slurry and can fabricate green parts using slurries with significantly higher solid loadings. After post processing, the fabricated piezoelectric components become dense and functional.
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James E. McNulty and Aigbe Akhigbe
Directors help determine the strategic direction of a corporation and are responsible for ensuring the institution has a good system of internal control. Banking institutions…
Abstract
Directors help determine the strategic direction of a corporation and are responsible for ensuring the institution has a good system of internal control. Banking institutions without a strategic direction emphasizing sound lending practices that promote the long-run financial health and viability of the institution will be sued more frequently than peer institutions. Institutions that do not have a good system of internal control will also be sued more frequently. Hence, legal expense is a bank corporate governance measure. We compare the performance of bank legal expense and a widely cited corporate governance index in a regression framework to determine which better predicts bank performance. The regressions indicate legal expense is a much better predictor, hence a better measure of bank corporate governance. Regulators should require legal expense reporting and rank institutions by the ratio of legal expense to assets to help identify institutions with weak governance. Seven case studies illustrate the role of legal expense in corporate governance.
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I build on a strong foundation of prior studies about expatriate compensation in general to provide an overview of changes in expatriate compensation, from home- to host-based…
Abstract
Purpose
I build on a strong foundation of prior studies about expatriate compensation in general to provide an overview of changes in expatriate compensation, from home- to host-based approaches, during the past 10 years.
Methodology/approach
Underpinned by findings from academic and practitioner literature, I review and integrate studies of expatriate compensation and global talent management to outline the challenges and opportunities home- and host-based compensation approaches present to MNEs.
Findings
Home-based compensation is becoming an outdated and overly expensive model that is often ineffective in moving MNEs’ global competitive advantage to where it needs to be, leaving host-based approaches as the only alternative. But the use of host-based “cheaper” compensation approaches can also lead to unintended outcomes for MNEs in terms of unforeseen opportunity costs (such as the loss of critical talent) arising from shortsighted compensation decisions.
Practical implications
I argue that expatriate compensation works best when it is not based on an employees’ home-country status but instead on the role that he or she performs locally. I suggest a host-based compensation approach — global compensation — that is based on the worth of the position rather than where the individual has come from. Such an approach is more equitable because it is performance-based thereby eliminating overpaying and perceived unfairness. It is much simpler to administer than home-based compensation because it represents an extension of most MNEs already existing domestic (home country) pay-for-performance model.
Originality/value
Despite more than 10 years of new compensation practices being implemented and reported by global mobility practitioners, very little has been studied or written by scholars about some of the recent changes in expatriate compensation over the past decade. The chapter addresses this gap in academic literature.