Relevant bibliographies by topics / Telescopic failure

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  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers

Academic literature on the topic 'Telescopic failure'

Author: Grafiati
Published: 4 June 2021
Last updated: 1 February 2022

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Journal articles on the topic "Telescopic failure"

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Xu, Ge Ning, Guang Heng Gao, and Zeng Cai Guo. "Analysis on Nonlinear Buckling Failure Influence Factors of Telescopic Boom System Based on Arc-Length and FEM Method." Applied Mechanics and Materials 532 (February 2014): 291–96. http://dx.doi.org/10.4028/www.scientific.net/amm.532.291.

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Telescopic jib is the key load-bearing component for both truck crane and all-terrain crane,seriously affect hoisting capacity of crane. Different stress feature or structural feature produce different affects on the hoisting capacity of telescopic jib. In order to study the mechanism and levels of different factors,multiple telescopic jib models with different factors are built based on nonlinear finite element method. Adopting Arc-length method to analysis structural nonlinear deformation in the whole course,the impact degree for hoisting performance of material yield strength, load eccentricity, lap length of telescopic jib and the support position of lifting hydraulic cylinder are acquired respectively. The results shows: A finite element method combined with arc-length method can be used to analysis the buckling problem of nonlinear deformation of telescopic jib. All the above four factors have affect on the hoisting performance of telescopic jib, but the levels are different. By analyzing change law of impact factors, corresponding measure are adopted in practical deign to reduce its impact and to strengthen the capacity of resisting local buckling of the telescopic jib.
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Hadianfard, M. J., and M. A. Hadianfard. "Structural Failure of a Telescopic Shiploader during Installation." Journal of Failure Analysis and Prevention 7, no. 4 (August 7, 2007): 282–91. http://dx.doi.org/10.1007/s11668-007-9049-x.

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Yao, Jia, Xiaoming Qiu, Zhenping Zhou, Yuqin Fu, Fei Xing, and Erfei Zhao. "Buckling failure analysis of all-terrain crane telescopic boom section." Engineering Failure Analysis 57 (November 2015): 105–17. http://dx.doi.org/10.1016/j.engfailanal.2015.07.038.

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Kahan, Michael E., Nathan R. Angerett, and Jill C. Flanagan. "Intraoperative Hardware Failure of the Fassier–Duval Rescue System in a Pediatric Patient with Osteogenesis Imperfecta." Case Reports in Pediatrics 2021 (May 25, 2021): 1–5. http://dx.doi.org/10.1155/2021/9982289.

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The use of telescopic intramedullary rods for the treatment of lower extremity deformity in children with osteogenesis imperfecta has been well described. The reinforcement of these weakened weightbearing bones with intramedullary devices leads to improvements in mobility that progress into adulthood. Although the current telescopic intramedullary rod systems are an upgrade from earlier systems, they are still associated with high rates of reoperation and complication. We describe a unique complication encountered during a revision which involved the male retriever system for the Fassier–Duval rod (FDR) (Pega Medical, Quebec, CA) experienced intraoperatively. To our knowledge, this mechanism of failure has not been previously described in the literature.
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Prakash, Jatin, Sumit Kumar Gupta, and PK Kankar. "An analytical approach to evaluate the maximum load carrying capacity for pin-mounted telescopic hydraulic cylinder." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 234, no. 19 (April 11, 2020): 3919–34. http://dx.doi.org/10.1177/0954406220916524.

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The hydraulic cylinder is an actuating mechanical maneuver used to transfer the power from one station to another. For industrial purposes, various types of cylinders are employed as per the requirement. Telescopic hydraulic cylinder, also known as the two-stage hydraulic cylinder is one of the widely used hydraulic cylinders in the industry. The closed center length of a telescopic cylinder is 20% to 40% of the open center length depending on the number of stages. The safe operation of such telescopic hydraulic cylinder is highly essential. One of the prominent failures includes the buckling failure of the hydraulic cylinder. Once the system fails, the operating parameters change abruptly and thus the proper working gets affected. In literature, there is no significant standard that governs the buckling load determination of two-stage hydraulic cylinder. Existing technical standard ISO/TS 13725 : 2016 approach is only prescribed for the single-stage cylinder. In this manuscript, the emphasis is kept upon the determination of the buckling load for the two-stage pin-mounted telescopic hydraulic cylinder. The buckling governing equation has been derived to obtain the buckling load using an analytical approach. Additionally, the stress condition of cylinder barrels of different stages has been discussed per thick cylinder theory. The finite element analysis has been performed for various dimensions of the hydraulic cylinder. The results obtained from analytical results show close vicinity with the finite element results.
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Yao, Jia, Fei Xing, Yuqin Fu, Xiaoming Qiu, Zhenping Zhou, and Jianhong Hou. "Failure analysis of torsional buckling of all-terrain crane telescopic boom section." Engineering Failure Analysis 73 (March 2017): 72–84. http://dx.doi.org/10.1016/j.engfailanal.2016.12.006.

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Xu, Ge Ning, and Kai Hao. "Research on Weld Defects Simulation and Performance Assessment of Solid-Web Type Telescopic Jib." Applied Mechanics and Materials 687-691 (November 2014): 236–42. http://dx.doi.org/10.4028/www.scientific.net/amm.687-691.236.

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To research the failure mode of solid-web type telescopic jib typical weld, extract and quantify failure characteristics, obtain failure regularity of jib performance and solve the problem that welds do not be established by conventional finite element analysis. The weld strength is replaced by the maximum stress of the corresponding section, which may cause the simulation results low and distortion, and cannot simulate weld defects. A new modeling method is used by this article, which establishes and simplifies the weld physical shape, simulate and analyze weld strength. The Life and Death element technology which is based on the ANSYS software is used to simulate weld defects. The weld strength that is obtained by conventional analysis simulation is 110MPa, after processing, stress of weld model without defects is 395MPa, the theoretical value be calculated is 437MPa, stress of weld model with defect 1, 2, 3 respectively is 586MPa, 402MPa and 475MPa. Through comparing the simulation value and the theoretical value and the comparison between the simulation values, the simplified model that is proved is reasonable, the technical route which is used to simulate weld defect by Life and death element technology is feasible. It can be used to predict failure critical value under typical working condition, assess whether the weld failure. The working condition of jib can be simulated, and the main factors can be retrospect.
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Cox, India, Louay Al Mouazzen, Sabri Bleibleh, Radu Moldovan, Fiona Bintcliffe, C. Edward Bache, and Simon Thomas. "Combined two-centre experience of single-entry telescopic rods identifies characteristic modes of failure." Bone & Joint Journal 102-B, no. 8 (August 2020): 1048–55. http://dx.doi.org/10.1302/0301-620x.102b8.bjj-2020-0131.r1.

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Aims The Fassier Duval (FD) rod is a third-generation telescopic implant for children with osteogenesis imperfecta (OI). Threaded fixation enables proximal insertion without opening the knee or ankle joint. We have reviewed our combined two-centre experience with this implant. Methods In total, 34 children with a mean age of five years (1 to 14) with severe OI have undergone rodding of 72 lower limb long bones (27 tibial, 45 femoral) for recurrent fractures with progressive deformity despite optimized bone health and bisphosphonate therapy. Data were collected prospectively, with 1.5 to 11 years follow-up. Results A total of 24 patients (33%) required exchange of implants (14 femora and ten tibiae) including 11 rods bending with refracture. Four (5%) required reoperation with implant retention. Loss of proximal fixation in the femur and distal fixation in the tibia were common. Four patients developed coxa vara requiring surgical correction. In total, 13 patients experienced further fractures without rod bending; eight required implant revision. There was one deep infection. The five-year survival rate, with rod revision as the endpoint, was 63% (95% confidence interval (CI) 44% to 77%) for femoral rods, with a mean age at implantation of 4.8 years (1.3 to 14.8), and 64% (95% CI 36% to 82%) for tibial rods, with a mean age at implantation of 5.2 years (2.0 to 13.8). Conclusion FD rods are easier to implant but do not improve on the revision rates reported for second generation T-piece rods. Proximal femoral fixation is problematic in younger children with a partially ossified greater trochanter. Distal tibial fixation typically fails after two years. Future generation implants should address proximal femoral and distal tibial fixation to avoid the majority of complications in this series. Cite this article: Bone Joint J 2020;102-B(8):1048–1055.
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Buelvas Castro, Edgardo Manuel, Fabio Andres Bermejo Altamar, and Ricardo Andrés Mendoza Quiroga. "Failure analysis and repair of the telescopic beam belonging to the spreader of a reach stacker for port operations." Scientia et Technica 25, no. 1 (March 30, 2020): 30–36. http://dx.doi.org/10.22517/23447214.23471.

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Reach stackers land equipment operating in ports of the Colombian Caribbean, are subject to several critical working conditions such as; corrosive environment, excess working hours, overload and lack of predictive maintenance. This work focuses on the failure analysis and the elaboration of the welding repair procedure of the telescopic beam belonging to the spreader of a Reach stacker that operates in a Colombian Caribbean seaport. Initially the fault zone was characterized; by mean a metallographic analysis and a hardness profile to identify the type of structural steel of which the beam is composed, obtaining an A514 grade C of 110KSI of tensile strength and 34HRC of hardness. The equipment manufacturer was verified and the established by the laboratory tests was corroborated. After identifying the material, the fracture area was analyzed where patterns of beach markings were found, typical of a fatigue failure which extended from the circumference of separating pins to the surface of the beam. The inclusion of the separators in the initial design generates stress concentrators in the welding of the pins which increases the fatigue zone combined with the excess load with which the equipment works. This fact could be verified with a technical bulletin published by the manufacturer brand "Taylor" where it indicates this type of failure for the telescopic beam of the Reach stackers. Successively, an FCAW type welding repair procedure is developed in accordance with AWS code D1.1, where the electrode to be used, the cords to be applied, the preheating, and the speeds and conditions recommended for filling the materials are selected cracks. Finally it could be concluded that the fault was generated by fatigue and overload in the welding of the telescopic beam separator pins and its repair will be carried out according to a welding procedure of the AWS code D1.1. The analysis of these types of cases will allow the company to take actions to minimize the new occurrence of the failure such as periodic reviews in that area after the work hours recommended by the manufacturer and the awareness of the equipment operators with the handling of loads on the dock.
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Lu, Feng Yi, Wei Zhu, Ge Ning Xu, and Ru Gang Yang. "The Life Evaluation to Determine Remanufacturing Access Period of Telescopic Boom for Mobile Crane." Applied Mechanics and Materials 551 (May 2014): 182–88. http://dx.doi.org/10.4028/www.scientific.net/amm.551.182.

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In order to determine the remanufacturing access period of telescopic boom for mobile crane, it is needed to study one of its main failure forms—fatigue damage to predict remaining fatigue life which is regarded as parameter to remanufacture and foundation to make comprehensive evaluation. First of all, in certain period, the numbers of work cycles corresponding to different lifting loads for different rated lifting capacity of telescopic boom are collected, so that a set of data can be got as learning sample, then editing a neural network program and training it by entering the learning sample obtain the appropriate neural network weights, finally through inputting rated lifting capacity and lifting loads of telescopic boom needed life evaluation to the neural network program, the numbers of work cycles are obtained. Building on the principle of Miner fatigue damage accumulation and combining with the Paris-Eadogan equation, the formula of remaining fatigue life is deduced, and finally the graph of remaining fatigue life corresponding to different initial crack is drew. The results show that the initial crack effect on the remaining fatigue life largely and crack of 0.4mm should be tracked and monitored as a starting point, so remanufacturing the boom at an appropriate time ensures safe and reliable operation of mobile crane.
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Dissertations / Theses on the topic "Telescopic failure"

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Peled, Alva. "Cement Penetrability Characteristics in Textile Cement Systems." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1244044138771-75495.

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Cement penetrability is a key factor in multifilament cement composites. However, the modes of action and the concepts vary because of brittle and ductile fibers. In the case of brittle fibers such as glass, high penetrability of cement products in between the bundle filaments can lead to brittle composite behavior, and therefore addition in ductility is required. In order to have efficient bundle action and high bonding, fillers can be introduced in between the glass filaments, keeping the telescopic mode of failure but at the same time improving the bond and stress transfer within the filaments of the bundle, even at late ages, resulting in a ductile and high strength composite. On the other hand, ductile fibers such as polypropylene (PP), which also developing low bonding with the cement matrix, result in ductile cement composite but with relatively low strength. Therefore, in this case good penetrability of the cement in between the filaments of the bundle is essential in order to maximize the reinforcing efficiency of the bundle by improving bond. The penetrability of the matrix into a fabric structure and especially in between the bundle filaments made up the fabric is a result of fiber- matrix compatibility, which depends on: level of opening and spaces between the filaments, bundle surface properties including wetting and chemical affinity to the cement matrix, matrix viscosity, processing of the composite, and the nature of the fabric junctions and the resulting tightening effects of the bundle, i.e., influenced by the fabric structure itself.
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Ahmed, Arman U. "Failure criteria for tearing of telescoping wrinkles." Phd thesis, 2011. http://hdl.handle.net/10048/1715.

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An ever increasing demand to exploit oil and natural gas reserves has significantly increased extraction activities even in the remotest regions of the Arctic and sub-Arctic regions of the Canadian North. Steel pipelines are the most efficient mode for transporting and distributing these resources. These pipelines, particularly buried in cold region, often subjected to extreme geo-environmental conditions, where significant inelastic deformation may occur resulting in localized wrinkles. Under continued deformation, there is a possibility of excessive cross-sectional deformation at wrinkle locations, eventually leading to fracture or damage in the pipe wall jeopardizing pipeline safety and integrity . Prior research indicated that occurrence of fracture in pipe wrinkle is rare under monotonic load-deformation process. However, a recent field fracture was observed within the wrinkle location of an energy pipeline. Similar failure mode was observed in a laboratory specimen at the University of Alberta. Both field and laboratory observations had indicated that the final failure was a “tearing” failure at the fold of the telescopic wrinkles resulting from monotonic application of axial load not aligned with pipe axis. This research program was designed to study this specific failure mode and to develop design tool for pipeline engineers. This research started with examining the failed field and test specimens. A preliminary investigation was carried out using nonlinear finite element (FE) model to simulate test and field behaviour. Numerical results have indicated that even under monotonic loading, significant strain reversals could occur at the wrinkle fold . Presence of these strain reversals was proposed as the preliminary failure criterion responsible for this unique failure mechanism. In next phase, a full-scale ‘pipe-wrinkling’ test program was carried out concurrent to this research to better understand the loading condition responsible for this type of failure. Results of this test program have shown the presence of tearing fracture or rupture in the pipe walls of several of test specimens. A series of FE analyses was then carried out to predict and verify the behaviour of these test specimens. After successful simulation of the test behaviour, further numerical analyses were carried out using tension coupon model developed herein to simulate the material behaviour using the material test data and hence to formulate the limiting conditions in terms of critical strain responsible for the tearing failure. Based on these numerical results, a double criterion  ‘Strain Reversal’ and ‘Critical Equivalent Plastic Strain Limit’, were proposed to predict tearing fracture of wrinkled pipe under monotonic loading. Results of these numerical analyses have demonstrated that the proposed criteria predict this failure mode with reasonable accuracy. In the final phase of this research, a parametric study was carried out to consider the effect of different parameters on failure modes of wrinkled pipe. Results of this parametric study describe the range of parameters under which the tearing mechanism can/may exhibit.
Structural Engineering
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Books on the topic "Telescopic failure"

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United States. National Aeronautics and Space Administration., ed. The Hubble Space Telescope optical systems failure report. [Washington, D.C.?]: National Aeronautics and Space Administration, 1990.

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Vigdor, Steven E. The Dark Side. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198814825.003.0006.

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Chapter 6 deals with the remaining mysteries in cosmology—dark matter, dark energy, and inflationary expansion—and the experiments aimed at solving them. It reviews the evidence for dark matter, and experiments to detect the microscopic particles proposed as its constituents: weakly interacting massive particles and invisible axions. Contrasts are drawn between the failure to understand the scale of dark energy theoretically and the ambitious new survey telescopes, such as the Large Synoptic Survey Telescope (or LSST), that aim to constrain its equation of state. The theoretical concepts and possible experimental signatures of cosmic inflation are described. Searches for possible imprints from primordial inflation-induced gravitational waves on the polarization of the cosmic microwave background (CMB polarization) are discussed in the context of the pioneering first detection by the Laser Interferometer Gravitational-Wave Observatory (or LIGO) of gravitational waves from distant black-hole mergers. Philosophical questions regarding the falsifiability of inflation are raised.
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Compendium of fracture mechanics problems. [Marshall Space Flight Center, Ala.]: National Aeronautics and Space Administration, George C. Marshall Space Flight Center, 1990.

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Book chapters on the topic "Telescopic failure"

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Hoffman, E., J. Boyle, and E. Rogers. "REAL knowledge and the James Webb Space Telescope: success and failure coexisting in NASA a aDisclaimer: This material is based upon work supported with resources and the use of facilities at the National Aeronautics and Space Administration (NASA), Office of the Chief Knowledge Officer and is available as open source information and may be used by external individuals and organizations with proper author citation." In Successes and Failures of Knowledge Management, 35–58. Elsevier, 2016. http://dx.doi.org/10.1016/b978-0-12-805187-0.00003-6.

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Conference papers on the topic "Telescopic failure"

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Miao, Yang, and Shaoping Wang. "Failure diagnosis of hydraulic lifting system based on multistage telescopic cylinder." In 2011 International Conference on Fluid Power and Mechatronics (FPM). IEEE, 2011. http://dx.doi.org/10.1109/fpm.2011.6045876.

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Söffker, Dirk. "Elastic Robot Arms With Variable Length: Part I — A Systematic Nonlinear Modeling Approach." In ASME 1995 Design Engineering Technical Conferences collocated with the ASME 1995 15th International Computers in Engineering Conference and the ASME 1995 9th Annual Engineering Database Symposium. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/detc1995-0252.

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Abstract In this paper modeling of a geometric nonlinear beam and the corresponding matrix representation of the model of 3rd order is considered. Especially in the case of lightweight robots for space applications undergoing large reference motion, the nonlinear dynamic behaviour of the beam should be modeled as exact as possible. Here coupling effects betweeen the elastic variables due to the geometric nonlinear beam kinematic are important. ‘Stiffning effects’ and parametrically excited effects between longitudinal and bending vibrations e.g., should also be considered. Starting with the nonlinear beam kinematics, all equations up to terms of second order are considered. Using the principal of virtual work, nonlinear equations are given, which are discretized by Hermite polynomials in the next step. Considering also terms of second order in the elastic variables, a special technique handling this equations in the usual structural dynamics matrix representation is developed to preserve the couplings of higher order in contrast to the usual linearization. Additionally, the length-variability is considered. So the clearness and effectiveness of matrix methods is combined with beam theory of 3rd. order, this means quadratic terms for the elastic variables axe considered building up state-dependend matrices. The importance of the effects of those couplings axe shown by two simulation examples of a planar and a spatial lightweight, very flexible telescopic robot arm for space operations. It can be shown clearly, that beside the known stiffning effects due to nominal axial loads, effects of higher order may weaken the structure up to failure of the structure.
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Lang, Donogh W., James Real, and Michael Lane. "Recent Developments in Drilling Riser Disconnect and Recoil Analysis for Deepwater Applications." In ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-79427.

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With exploration and development of hydrocarbon resources moving into ever deeper waters, there is significantly increased demand for drilling vessels capable of drilling in water depths of up to 10,000 ft and beyond. One of the main challenges associated with drilling in these water depths is control of the recoil behavior of the drilling riser after an emergency disconnect. This is required from time to time in the event of loss of the vessel’s station-keeping capability, either in extreme weather or through a failure of the dynamic positioning system. In these scenarios, the riser must be quickly disconnected below the Lower Marine Riser Package (LMRP) to avoid damage to the riser or well structure. Once disconnected, the LMRP should lift sufficiently clear of the Blow-Out Preventer (BOP) to avoid subsequent contact between the LMRP and the BOP, while at the same time the upward movement of the riser must be arrested in time to prevent collapse of the telescopic joint (which could cause impact loads on the drillfloor) or compression in the tensioning lines. These conflicting requirements become more severe in deepwater, where the ratio between the wet weight and inertia of the riser is reduced. This highlights the requirement for an accurate recoil analysis capability in order to determine the optimum riser stack-up and operability limits for deepwater operations. This paper describes the development of a disconnect and recoil analysis software tool that for the first time has been integrated with a 3D finite element (FE) structural model of the drilling riser system. The tool incorporates a detailed model of the riser tensioning system, including the ability to model the behavior of each tensioning cylinder independently and the ability to model the behavior of the anti-recoil control system. The tool also incorporates an advanced fluid flow model, implemented by means of a finite volume numerical model, that models the flow of drilling mud out of the riser immediately after disconnect. The details of the tensioner system and fluid flow models are discussed, along with the approach taken to integrate these into the existing FE structural analysis code. A number of case studies are presented to illustrate the application of the tool to deepwater riser recoil analysis and to examine the effect of key parameters (including vessel offset) on the recoil behavior of the riser system.
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Cheng, Jingquan, Antonio Rodriguez, Nicolas Emerson, and Arthur Symmes. "Study of simple CFRP-metal joint failure." In SPIE Astronomical Telescopes + Instrumentation, edited by Eli Atad-Ettedgui and Dietrich Lemke. SPIE, 2008. http://dx.doi.org/10.1117/12.786667.

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Hill, R. J., E. Malumuth, R. Foltz, R. A. Kimble, A. Waczynski, N. Boehm, Y. Wen, E. Kan, and N. R. Collins. "Reciprocity failure in 1.7 μm cut-off HgCdTe detectors." In SPIE Astronomical Telescopes + Instrumentation, edited by Andrew D. Holland and David A. Dorn. SPIE, 2010. http://dx.doi.org/10.1117/12.857218.

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Walraven, Jeremy A., Edward I. Cole, Danelle M. Tanner, Seethambal S. Mani, Ernest J. Garcia, and Marc A. Polosky. "Failure Analysis of Polysilicon Micromirror Arrays." In ISTFA 2002. ASM International, 2002. http://dx.doi.org/10.31399/asm.cp.istfa2002p0283.

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Abstract Surface micromachined micromirror technologies are being employed for various commercial and government applications. One application of micromirror technologies in the commercial sector can be found in Digital Light Projection (DLP™) systems used for theater and home entertainment centers. DLP™ systems developed by Texas Instruments uses DMD™ technology (Digital Mirror Device), an array of micromirrors, to project light onto a screen [1]. This technology is also used by Infocus™ projection systems and widescreen tabletop televisions [2]. Here, the micromirrors act as individual pixels, reflecting light onto the screen with high ¡§digital¡¨ resolution. The most recent application of surface micromachined micromirror technology is optical switching [3], which uses micromirrors to switch optical signals from fiber to fiber for lightwave telecommunications [4]. Companies such as Lucent have fabricated entire optical micromirror switching systems based on their Microstar™ technology [5]. For government applications, surface micromachined micromirror arrays have been developed for potential use in a spectrometer system planned for NASA's Next Generation Space Telescope (NGST) [6]. Various processing technologies are used to fabricate surface micromachined micromirrors. The micromirror arrays developed by TI and Lucent [1,4] uses metal for their structural and reflective components. Micromirrors fabricated at Sandia National Laboratories use the SUMMiT™ (Sandia's Ultra-planar MEMS Multi-level Technology) process with metal deposited on the surface of mechanical polysilicon components to reflect light. Optical micromirror arrays designed and fabricated at Sandia for potential use in the NGST have undergone reliability testing and failure analysis. This paper will discuss the failure modes found in these micromirrors after reliability testing. Suggestions and corrective actions for improvements in device performance will also be discussed.
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Schubnell, M., T. Biesiadzinski, W. Lorenzon, R. Newman, and G. Tarlé. "Investigating reciprocity failure in 1.7-micron cut-off HgCdTe detectors." In SPIE Astronomical Telescopes + Instrumentation, edited by Andrew D. Holland and David A. Dorn. SPIE, 2010. http://dx.doi.org/10.1117/12.857459.

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Radovan, Matthew V., and Gerald F. Cabak. "Buckling failure of the automated planet finder spectrometer determinate spaceframe." In SPIE Astronomical Telescopes + Instrumentation, edited by Ian S. McLean, Suzanne K. Ramsay, and Hideki Takami. SPIE, 2012. http://dx.doi.org/10.1117/12.926619.

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Fallorina, Salvador, Helen Boussalis, Charles Liu, Khosrow Rad, Jane Dong, Dani Nasser, and Paul Thienphrapa. "A Generic Pipelined Task Scheduling Algorithm for Fault-Tolerant Decentralized Control of a Segmented Telescope Testbed." In ASME 2004 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/detc2004-57701.

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Control of complex structures requires high computational power to achieve real-time performance. Through decentralized techniques, a complex structure can be controlled by multiple lower-order local controllers, leading to reduced computational complexities. Furthermore, a decentralized approach can both simplify the development of parallel controllers and facilitate fault-tolerant designs. In our research, multiple digital signal processors are employed in a NASA-sponsored segmented telescope testbed to increase the throughput of control tasks. Although increased performance is realized when subsystems are statically mapped to specific processors for control, inefficiency arises if the number of subsystems M is not an integer multiple of the number of processors P (M > P) because (M mod P) processors are necessarily controlling more subsystems than others. Optimality is sacrificed because processors with lighter loads wait for processors with heavier loads. Furthermore this mechanism does not lend itself favorably towards fault tolerance because the failure of a single processor will result in the failure of its subsystem. This paper describes the design and implementation of a pipelined task mapping approach for the decentralized control of a segmented reflector telescope testbed. In our pipelined processing implementation only four of the six subsystems are processed in any given control cycle; the two unprocessed subsystems in each cycle propagate about the system in a round-robin fashion, so processors are never idle. Fault tolerance is facilitated because processors are no longer tied to specific subsystems. Instead, control computations are distributed dynamically such that the pipeline flow structure is maintained. The implementation of a watchdog technology is presented for detecting the possible processor failures. Experimental results are shown comparing the performance of the pipelined and straightforward approaches. The throughput of the system has also been estimated on a system with a larger number of processors. Such estimation shows the linearity of speedup achieved by using the pipelined approach.
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Diezel, Alexandre, Germain Venero, Victor Gomes, Leandro Muniz, Rafael Fachini, and Hugues Corrignan. "Drilling Riser Disconnection Challenges in Ultra-Deep Water." In ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/omae2018-77115.

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With the extension of the offshore drilling operations to water depths of 10,000 ft and beyond, the technical challenges involved also increased considerably. In this context, the management of the riser integrity through the application of computational simulations is capital to a safe and successful operation — particularly in harsh environments. One of the main challenges associated with keeping the system under safe limits is the recoil behavior in case of a disconnection from the well. The risk that an emergency disconnect procedure can take place during the campaign is imminent, either due to failure of the dynamic positioning system or due to extreme weather in such environments. Recent work [1] in the field of drilling riser dynamic analysis has shown that the recoil behavior of the riser after a disconnection from the bottom can be one of the main drivers of the level of top tension applied. Tension fluctuations can be very large as the vessel heaves, especially in ultra-deep waters where the average level of top tension is already very high. In order to be successful, a safe disconnection must ensure that the applied top tension is sufficient for the Lower Marine Riser Package (LMRP) to lift over the Blow-Out Preventer (BOP) with no risk of interference between the two. This tension should also not exceed a range in which the riser will not buckle due to its own recoil, that the telescopic joint will not collapse and transfer undesirable loads onto the drilling rig or that the tensioning lines will not compress. A good representation of such behavior in computational simulations is therefore very relevant to planning of the drilling campaign. A case study is presented herein, in which a recoil analysis was performed for a water depth of 11,483ft (3,500m). Numerical simulations using a finite element based methodology are applied for solving the transient problem of the riser disconnection in the time domain using a regular wave approach. A detailed hydro-pneumatic tensioning system model is incorporated to properly capture the effect of the anti-recoil valve closure and tension variations relevant during the disconnection. A reduction of conservativism is applied for the regular wave approach, where the maximum vessel heave likely to happen in every 50 waves is applied instead of the usual maximum in 1000 waves approach. ISO/TR 13624-2 [4] states that using the most probable maximum heave in 1000 waves is considered very conservative, as the event of the disconnection takes place in a very short period of time. The challenges inherent to such an extreme site are presented and conclusions are drawn on the influence of the overall level of top tension in the recoil behavior.
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