74 research outputs found

    Surgical Applications of Compliant Mechanisms:A Review

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    Current surgical devices are mostly rigid and are made of stiff materials, even though their predominant use is on soft and wet tissues. With the emergence of compliant mechanisms (CMs), surgical tools can be designed to be flexible and made using soft materials. CMs offer many advantages such as monolithic fabrication, high precision, no wear, no friction, and no need for lubrication. It is therefore beneficial to consolidate the developments in this field and point to challenges ahead. With this objective, in this article, we review the application of CMs to surgical interventions. The scope of the review covers five aspects that are important in the development of surgical devices: (i) conceptual design and synthesis, (ii) analysis, (iii) materials, (iv) maim facturing, and (v) actuation. Furthermore, the surgical applications of CMs are assessed by classification into five major groups, namely, (i) grasping and cutting, (ii) reachability and steerability, (iii) transmission, (iv) sensing, and (v) implants and deployable devices. The scope and prospects of surgical devices using CMs are also discussed

    Rolling contact orthopaedic joint design

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    Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references.Arthroplasty, the practice of rebuilding diseased biological joints using engineering materials, is often used to treat severe arthritis of the knee and hip. Prosthetic joints have been created in a "biomimetic" manner to reconstruct the shape of the biological joint. We are at a disadvantage, however, in that metals and polymers used to replace bone and articular cartilage often wear out too soon, leading to significant morbidity. This thesis explores the use of kinetic-mimicry, instead of bio-mimicry, to design prosthetic rolling contact joints, including knee braces, limb prosthetics, and joint prostheses, with the intent of reducing morbidity and complications associated with joint/tissue failure. A deterministic approach to joint design is taken to elucidating six functional requirements for a prosthetic tibiofemoral joint based on anatomical observations of human knee kinetics and kinematics. Current prostheses have a high slide/roll ratio, resulting in unnecessary wear. A rolling contact joint, however, has a negligible slide/roll ratio; rolling contact prostheses would therefore be more efficient. A well-established four-bar linkage knee model, in a sagittal plane that encapsulates with the knee's flexion/extension degree of freedom, is used to link human anatomy to the shape of rolling cam surfaces. The first embodiment of the design is a flexure coupling-based joint for knee braces. Failure mode analysis, followed by cyclic failure testing, has shown that the prototype joint is extremely robust and withstood half a million cycles during the first round of tests. Lubrication in the joint is also considered: micro- and nano-textured porous coatings are investigated for their potential to support the formation of favorable lubrication regimes. Hydrodynamic lubrication is optimal, as two surfaces are separated by a fluid gap, thus mitigating wear. Preliminary results have shown that shear stress is reduced by more than 60% when a coating is combined with a shear thinning lubricant like synovial fluid. These coatings could be incorporated into existing joint prostheses to help mitigate wear in current technology. This thesis seeks to describe improvements to the design of prosthetic joints, both existing and future, with the intent of increasing the overall quality of care delivered to the patient.by Alexander Henry Slocum, Jr.Ph.D

    Additive manufacturing and joints: Design and methods

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    The industrialization of the Additive Manufacturing (AM) processes is enabling the use of AM components as final product in several applications. These processes are particularly relevant for manufacturing components with optimized custom-tailored geometries. However, to fully exploit the potentiality of AM, the development of knowledge aimed to produce dedicated design methods is needed. Indeed, even if AM enables the manufacturing of new kinds of structures, e.g. 3D lattice structures, it introduces process-specific design input and limitations that needs design methods different to from the ones for subtractive manufacturing. Design for AM (DfAM) is a design methodology that aims to take advantage of new buildable geometries but taking into account also AM processed materials anisotropy and 3D printing constraints. Recent literature focused on the assembly of AM components and on the AM components joining to a main structure. The conclusion was that adhesive bonding is a promising joining process, especially considering its improved stress distribution compared to fastening, but at the time of writing a method that combines DfAM and adhesive bonding knowledge is not available. The work presented in this thesis focused on developing knowledge on design for AM and bonded joints. First step was evaluating testing methods for AM and producing data on materials properties. Secondly, the early works on tailoring approaches for AM joints, published recently in scientific literature, were analyzed. Then AM dedicated designs, modifications and testing methods were proposed both for the adherends (in the thickness and on the surfaces) and the joints. Specifically, an innovative joint design concept was introduced, i.e. using the 3D printing parameters as bonded joint design factors. Eventually, feasibility of performing joints using multi-material AM with conductive polymer to embed heating elements was assessed. The 3D printed through the thickness circuits is a cutting-edge approach to enable new solutions for joints structural monitoring and self-healing

    Design for additive manufacturing: Trends, opportunities, considerations, and constraints

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    The past few decades have seen substantial growth in Additive Manufacturing (AM) technologies. However, this growth has mainly been process-driven. The evolution of engineering design to take advantage of the possibilities afforded by AM and to manage the constraints associated with the technology has lagged behind. This paper presents the major opportunities, constraints, and economic considerations for Design for Additive Manufacturing. It explores issues related to design and redesign for direct and indirect AM production. It also highlights key industrial applications, outlines future challenges, and identifies promising directions for research and the exploitation of AM's full potential in industry

    Druckaktuierte zelluläre Strukturen

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    The herein presented investigations address the implementation of a holistic design process for Pressure-Actuated Cellular Structures (PACS) and include their realization and characterization. Similar to the motion of nastic plants, the actuation principle of these biologically inspired shape-variable structures bases on the controlled expansion of pressurized volumes. The advantages of fluidic actuation are combined with an adaptive single-curved structure that deforms continuously and with controllable stiffness between predefined states of shape. Benfits from the utilization of such a structure are expected within the fields of aeronautical, automobile, power and civil engineering. The identification of open issues, the development and the validation of design methods, as well as the evaluation of the performance of the concept of PACS are realized in consideration of the global system. A holistic solution for the design of PACS is successfully implemented and allows for the profound investigation on an experimental basis. The foundation for the evaluation and utilization of such shape-variable structures is thus laid.Die nachfolgenden Untersuchungen befassen sich mit der Entwicklung eines ganzheitlichen Entwurfsprozesses für Druckaktuierte Zelluläre Strukturen (PACS, engl.: Pressure-Actuated Cellular Structures), sowie deren Realisierung und Charakterisierung. Ähnlich dem Vorbild nastischer Pflanzen, basiert das Antriebsprinzip dieser biologisch inspirierten formvariablen Strukturen auf der Ausdehnung druckbeaufschlagter Volumina. Die Vorzüge fluidischer Aktuierung lassen sich dabei auf eine einfach gekrümmte Struktur übertragen, welche sich stufenlos und mit kontrollierbarer Steifigkeit zwischen spezifizierbaren Formzuständen deformieren lässt. Potentiale aus der Nutzung einer solchen Struktur ergeben sich unter anderem für die Bereiche Luftfahrt, Automobil- und Energietechnik sowie Bauwesen. Die Identifikation offener Problemfelder, die Entwicklung und Validierung von Entwurfsmethoden, sowie die Bewertung der Leistungsfähigkeit des Konzeptes der PACS erfolgen in dieser Arbeit über eine ganzheitliche Systembetrachtung. Das Konzept der PACS kann durch den Aufbau eines ganzheitlichen Entwurfsprozesses erstmals fundiert und auf experimenteller Basis untersucht werden. Die Grundlagen zur Bewertung und Nutzung solcher formvariabler Strukturen sind damit geschaffen

    Design for additive manufacturing: trends, opportunities, considerations, and constraints

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    © 2016 CIRP. The past few decades have seen substantial growth in Additive Manufacturing (AM) technologies. However, this growth has mainly been process-driven. The evolution of engineering design to take advantage of the possibilities afforded by AM and to manage the constraints associated with the technology has lagged behind. This paper presents the major opportunities, constraints, and economic considerations for Design for Additive Manufacturing. It explores issues related to design and redesign for direct and indirect AM production. It also highlights key industrial applications, outlines future challenges, and identifies promising directions for research and the exploitation of AM's full potential in industry

    Proceedings of the 40th Aerospace Mechanisms Symposium

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    The Aerospace Mechanisms Symposium (AMS) provides a unique forum for those active in the design, production and use of aerospace mechanisms. A major focus is the reporting of problems and solutions associated with the development and flight certification of new mechanisms. Organized by the Mechanisms Education Association, responsibility for hosting the AMS is shared by the National Aeronautics and Space Administration and Lockheed Martin Space Systems Company (LMSSC). Now in its 40th symposium, the AMS continues to be well attended, attracting participants from both the U.S. and abroad. The 40th AMS, hosted by the Kennedy Space Center (KSC) in Cocoa Beach, Florida, was held May 12, 13 and 14, 2010. During these three days, 38 papers were presented. Topics included gimbals and positioning mechanisms, CubeSats, actuators, Mars rovers, and Space Station mechanisms. Hardware displays during the supplier exhibit gave attendees an opportunity to meet with developers of current and future mechanism components. The use of trade names of manufacturers in this publication does not constitute an official endorsement of such products or manufacturers, either expressed or implied, by the National Aeronautics and Space Administratio

    41st Aerospace Mechanisms Symposium

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    The proceedings of the 41st Aerospace Mechanisms Symposium are reported. JPL hosted the conference, which was held in Pasadena Hilton, Pasadena, California on May 16-18, 2012. Lockheed Martin Space Systems cosponsored the symposium. Technology areas covered include gimbals and positioning mechanisms, components such as hinges and motors, CubeSats, tribology, and Mars Science Laboratory mechanisms

    44th Aerospace Mechanisms Symposium

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    The Aerospace Mechanisms Symposium (AMS) provides a unique forum for those active in the design, production and use of aerospace mechanisms. A major focus is the reporting of problems and solutions associated with the development and flight certification of new mechanisms
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