2,229 research outputs found

    Full Scale Proton Beam Impact Testing of new CERN Collimators and Validation of a Numerical Approach for Future Operation

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    New collimators are being produced at CERN in the framework of a large particle accelerator upgrade project to protect beam lines against stray particles. Their movable jaws hold low density absorbers with tight geometric requirements, while being able to withstand direct proton beam impacts. Such events induce considerable thermo-mechanical loads, leading to complex structural responses, which make the numerical analysis challenging. Hence, an experiment has been developed to validate the jaw design under representative conditions and to acquire online results to enhance the numerical models. Two jaws have been impacted by high-intensity proton beams in a dedicated facility at CERN and have recreated the worst possible scenario in future operation. The analysis of online results coupled to post-irradiation examinations have demonstrated that the jaw response remains in the elastic domain. However, they have also highlighted how sensitive the jaw geometry is to its mounting support inside the collimator. Proton beam impacts, as well as handling activities, may alter the jaw flatness tolerance value by ±\pm 70 μ{\mu}m, whereas the flatness tolerance requirement is 200 μ{\mu}m. In spite of having validated the jaw design for this application, the study points out numerical limitations caused by the difficulties in describing complex geometries and boundary conditions with such unprecedented requirements.Comment: 22 pages, 17 figures, Prepared for submission to JINS

    Design of a reusable kinetic energy absorber for an astronaut safety tether to be used during extravehicular activities on the Space Station

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    The goal of this project is to design a reusable safety device for a waist tether which will absorb the kinetic energy of an astronaut drifting away from the Space Station. The safety device must limit the tension of the tether line in order to prevent damage to the astronaut's space suit or to the structure of the spacecraft. The tether currently used on shuttle missions must be replaced after the safety feature has been developed. A reusable tether for the Space Station would eliminate the need for replacement tethers, conserving space and mass. This report presents background information, scope and limitations, methods of research and development, alternative designs, a final design solution and its evaluation, and recommendations for further work

    Index to NASA Tech Briefs, January - June 1966

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    Index to NASA technological innovations for January-June 196

    Effects of Expected Service Life Exposures on the Functional Properties and Impact Performance of an American Football Helmet Outer Shell Material

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    The purpose of this dissertation is to gain a greater scientific understanding of the changes in functional material properties and impact performance of an American football helmet outer shell material under expected service life exposures. The research goals are to (i) quantify chemical, physical, thermal, and mechanical degradation of an American football outer shell material under expected environmental conditions and (ii) develop a linear drop test impact protocol to employ expected on-field impact conditions to American football helmet components and a plaque-foam (i.e., shell-liner) surrogate. Overall, a step-wise progression of analysis was demonstrated to concurrently quantify and understand changes in material properties at the molecular, microscopic, and macroscopic levels. Changes across chemical, physical, thermal, and mechanical properties were evaluated following laboratory exposures to 480 hours of accelerated weathering, increasing intensities of n-Butyl acetate solvent, and 12 repetitive linear plaque-foam impacts. In Chapter II, an instrumented drop test setup was substantiated to investigate linear impact attenuation performance. In Chapter III, laboratory exposure to UV light, oxygen, moisture, and elevated temperatures induced molecular degradative bi-products and physical aging up to ~1% into the plaque thickness which led to altered aesthetic properties, chemi-crystallization, and an increased resistance to surface indentation and tensile deformation. In Chapter IV, solvent-induced plasticization, crystallization, and stress-cracking of up to ~3% into the plaque thickness led to an increase in surface porosity which scattered light and decreased tensile properties. In Chapter V, impact exposure induced rubber-toughener (RT) cavitation that generated voids via delamination at the RT-matrix interface at which led to rings of stress-whitening, strain-induced crystallization, increased butadiene RT density, and shifts surface modulus and tensile properties. This dissertation preliminarily substantiated (i) a drop test setup attempting to accurately replicate on-field impact conditions to investigate linear impact attenuation performance, and (ii) polymer techniques and protocols that could elucidate the rates and degrees of material degradation

    Index to nasa tech briefs, issue number 2

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    Annotated bibliography on technological innovations in NASA space program

    Design and optimization of Metallic Foam Shell protective device against flying ballast impact damage in railway axles

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    Abstract Ballast impacts can initiate surface defects that cause abrupt failure of the axle and derailment of the railway vehicle. According to the Federal Railroad Administration the axle and bearing failure costs around 89 million dollars and causes 46 derailments in the US per year (2005–2010). In this study, the authors have suggested a novel protective mechanism (Metallic Foam Shell – MFS) by using a lightweight sandwich panel. At the first step, a preliminary study is conducted, followed up by the numerical simulations to determine the applicable materials. At the next step, experimental tests were performed to assess the efficiency of the suggested device against flying ballast impacts. An extended non-destructive (NDT) evaluation has been performed in order to find the most suitable technique for damage detection of the proposed device when on-service. The studied cases were GFRP and Aluminium sandwich panels, having an aluminium foam core with different densities and thicknesses. The results showed that the MFS can absorb up to 90% of the initial impact energy and significantly decrease the chance of rebounding impact to the other components. Moreover, the results were also analysed in order to propose the most reliable NDT method for this specific application

    Bioinspired design of a landing system with soft shock absorbers for autonomous aerial robots

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    © 2018 Wiley Periodicals Inc. One of the main challenges for autonomous aerial robots is to land safely on a target position on varied surface structures in real-world applications. Most of current aerial robots (especially multirotors) use only rigid landing gears, which limit the adaptability to environments and can cause damage to the sensitive cameras and other electronics onboard. This paper presents a bioinpsired landing system for autonomous aerial robots, built on the inspire–abstract–implement design paradigm and an additive manufacturing process for soft thermoplastic materials. This novel landing system consists of 3D printable Sarrus shock absorbers and soft landing pads which are integrated with an one-degree-of-freedom actuation mechanism. Both designs of the Sarrus shock absorber and the soft landing pad are analyzed via finite element analysis, and are characterized with dynamic mechanical measurements. The landing system with 3D printed soft components is characterized by completing landing tests on flat, convex, and concave steel structures and grassy field in a total of 60 times at different speeds between 1 and 2 m/s. The adaptability and shock absorption capacity of the proposed landing system is then evaluated and benchmarked against rigid legs. It reveals that the system is able to adapt to varied surface structures and reduce impact force by 540N at maximum. The bioinspired landing strategy presented in this paper opens a promising avenue in Aerial Biorobotics, where a cross-disciplinary approach in vehicle control and navigation is combined with soft technologies, enabled with adaptive morphology

    Shock absorbing reception surfaces for collecting fruit during the mechanical harvesting of citrus

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    Damage to fresh citrus caused by impact of fruits onto collecting surfaces has restricted the adoption of mechanical harvesting. Two different experiments were carried out: investigating free-falling citrus and investigating the shock absorbing capacity of various surfaces. In free-falling experiment damage to mandarin, orange and lemon was studied. Three collecting surfaces were studied: a concrete floor, an elevated canvas provided with a frame and wheels, and a concrete floor covered with a shock absorbing canvases. Three dropping heights were used. In the shock absorbing experiment, an electronic sphere and a triaxial accelerometer were used to measure the shock capacity of seven receiving surfaces: earth, earth covered with a shock absorbing canvas, earth covered with weeds, earth covered with a mulch and an elevated canvas provided with a frame and wheels. The elevated canvases had a higher shock absorbing capacity compared to the other surfaces (260 m s−2 maximum acceleration compared with 1753 m s−2 to 2772 m s−2). Weeds, mulch and the shock absorbing canvases showed significantly higher shock absorbing capacity than the bare earth. Also, the shock absorbing canvas covering the concrete floor reduce impact and fruit damage (1866 m s−2 maximum acceleration compared to 2477 m s−2). Citrus damage susceptibility during harvest depended on variety. Weeds, mulch and shock absorbing canvases were shown to reduce impact when they cover earth during the mechanical harvesting of citrus. Elevated canvases could be used as collection systems for the mechanical harvesting of fresh citrus.This study was funded by the Ministerio de Ciencia e Innovacion (research project RTA2009-00118-C02-02) and FEDER. The authors are most grateful to the following collaborators: Maria del Mar Lopez Quevedo, Montano Perez, Juan Jose Pena and Angel Perez.Ortiz Sánchez, MC.; Blasco, J.; Balasch Parisi, S.; Torregrosa Mira, A. (2011). Shock absorbing reception surfaces for collecting fruit during the mechanical harvesting of citrus. Biosystems Engineering. 110(1):2-9. https://doi.org/10.1016/j.biosystemseng.2011.05.006S29110

    High energy shock absorber and structural overload devices final report, jul. 1964 - may 1965

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    High energy shock absorber and structural overload devic

    Modeling Large Deformation and Failure of Expanded Polystyrene Crushable Foam Using LS-DYNA

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    In the initial phase of the research work, quasistatic compression tests were conducted on the expanded polystyrene (EPS) crushable foam for material characterisation at low strain rates (8.3×10-3~8.3×10-2 s−1) to obtain the stress strain curves. The resulting stress strain curves are compared well with the ones found in the literature. Numerical analysis of compression tests was carried out to validate them against experimental results. Additionally gravity-driven drop tests were carried out using a long rod projectile with semispherical end that penetrated into the EPS foam block. Long rod projectile drop tests were simulated in LS-DYNA by using suggested parameter enhancements that were able to compute the material damage and failure response precisely. The material parameters adjustment for successful modelling has been reported
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