Academic literature on the topic 'Plates (Engineering) Cracking Mathematical models'
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Journal articles on the topic "Plates (Engineering) Cracking Mathematical models"
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GIORGI, C. "Mathematical models of thin thermoviscoelastic plates." Quarterly Journal of Mechanics and Applied Mathematics 53, no. 3 (September 1, 2000): 363–74. http://dx.doi.org/10.1093/qjmam/53.3.363.
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Karpiuk, Vasyl, Yuliia Somina, Fedir Karpiuk, and Irina Karpiuk. "Peculiar aspects of cracking in prestressed reinforced concrete T-beams." Acta Polytechnica 61, no. 5 (October 31, 2021): 633–43. http://dx.doi.org/10.14311/ap.2021.61.0633.
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In order to study the cracking of prestressed reinforced concrete T-shaped beam structures, the authors planned and carried out a full-scale experiment with five variable factors. The following factors were chosen as variable factors: the relative span of the shear, the ratio of the table overhang width to the thickness of the beam rib, the ratio of the table overhang thickness to the working height of the beam section, the coefficient of transverse reinforcement, the level of prestressing in the working reinforcement. The article describes the cracking process and the destruction of test beams. It was found that the loading level of an opening of inclined cracks is 53% larger than the loading level of a normal crack opening. Mathematical models of bending moments and transverse forces of cracking were built using the “COMPEX” software. Also, the mathematical models of the crack opening width and the projection length of a dangerous inclined crack were obtained. These models are based on the experimental data. Analysing the obtained models, the complex influence of variable factors on the main parameters of crack formation and crack resistance was established. In particular, it was found that the prestress level in the working reinforcement has the greatest effect on the bending moment of cracking. In this case, the value of the shear force of cracking significantly depends on both the prestressing level in the reinforcement and the relative span of the shear. On the basis of the experimental data, the empirical expression is obtained for determining the projection of a dangerous inclined crack for prestressed reinforced concrete T-shaped beams. The resulting equation can be used to calculate a shear reinforcement.
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Prysiazhnyi, Andrii H., Volodymyr V. Kukhar, Vadym Hornostai, Ekaterina Kudinova, Maryna Korenko, and Oleksandr S. Anishchenko. "Mathematical Models for Forecasting of 10Mn2VNb Steel Heavy Plates Mechanical Properties." Materials Science Forum 1045 (September 6, 2021): 237–45. http://dx.doi.org/10.4028/www.scientific.net/msf.1045.237.
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The problem urgency for determining the optimal rolling and heat treatment schedules for providing the required indices of heavy plates physical and mechanical properties is shown. The use of statistical mathematical models for solving this problem is substantiated and the methodology for their design is described. Statistical mathematical models were designed using the mathematical statistics methods and Data Mining tools to determine the yield strength, ultimate tensile strength and percent elongation for 10Mn2VNb steel plates rolled under 3600 heavy plate mill conditions. Software for the numerical implementation of these statistical mathematical models has been developed. Applied software has been developed for the numerical implementation of the statistical mathematical models for predicting the heavy plate’s mechanical properties, and high calculation accuracy has been confirmed with the ones help: 95.82% for the yield strength, 96.78% for the ultimate tensile strength, and 91.48% for the percent elongation. The regularities of the influence for finish rolling factual temperature in the finishing stand of 3600 heavy plate mill and the plate thickness on 10Mn2VNb pipe steel physical and mechanical properties were identified by processing the database and using the designed software.
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Changjun, Cheng, and Yang Xiao. "The mathematical models and generalized variational principles of nonlinear analysis for perforated thin plates." Applied Mathematics and Mechanics 17, no. 2 (February 1996): 109–18. http://dx.doi.org/10.1007/bf00122305.
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Cole, I. S., and D. A. Paterson. "Mathematical models of dependence of surface temperatures of exposed metal plates on environmental parameters." Corrosion Engineering, Science and Technology 41, no. 1 (March 2006): 67–76. http://dx.doi.org/10.1179/174327806x94045.
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Krysko, A. V., J. Awrejcewicz, K. S. Bodyagina, M. V. Zhigalov, and V. A. Krysko. "Mathematical modeling of physically nonlinear 3D beams and plates made of multimodulus materials." Acta Mechanica 232, no. 9 (June 26, 2021): 3441–69. http://dx.doi.org/10.1007/s00707-021-03010-8.
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AbstractIn this work, mathematical models of physically nonlinear plates and beams made from multimodulus materials are constructed. Our considerations are based on the 3D deformation theory of plasticity, the von Mises plasticity criterion and the method of variable parameters of the theory of elasticity developed by Birger. The proposed theory and computational algorithm enable for solving problems of three types of boundary conditions, edge conditions and arbitrary lateral load distribution. The problem is solved by the finite element method (FEM), and its convergence and the reliability of the results are investigated. Based on numerical experiments, the influence of multimodulus characteristics of the material of the beam and the plate on their stress–strain states under the action of transverse loads is illustrated and discussed.
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Krysko, A. V., J. Awrejcewicz, K. S. Bodyagina, and V. A. Krysko. "Mathematical modeling of planar physically nonlinear inhomogeneous plates with rectangular cuts in the three-dimensional formulation." Acta Mechanica 232, no. 12 (November 16, 2021): 4933–50. http://dx.doi.org/10.1007/s00707-021-03096-0.
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AbstractMathematical models of planar physically nonlinear inhomogeneous plates with rectangular cuts are constructed based on the three-dimensional (3D) theory of elasticity, the Mises plasticity criterion, and Birger’s method of variable parameters. The theory is developed for arbitrary deformation diagrams, boundary conditions, transverse loads, and material inhomogeneities. Additionally, inhomogeneities in the form of holes of any size and shape are considered. The finite element method is employed to solve the problem, and the convergence of this method is examined. Finally, based on numerical experiments, the influence of various inhomogeneities in the plates on their stress–strain states under the action of static mechanical loads is presented and discussed. Results show that these imbalances existing with the plate’s structure lead to increased plastic deformation.
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Liu, Nian, Nansheng Qiu, Zhenming Li, Chuan Cai, Xinjie Shan, Ting Gao, and Yuanjie Wang. "Significance and evolution characteristics of the isobutane/n-butane ratio of natural gas." Energy Exploration & Exploitation 38, no. 2 (October 15, 2019): 494–518. http://dx.doi.org/10.1177/0144598719880648.
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In previous studies, two conflicting conclusions existed, which were: (a) the isobutane/n-butane ratio of natural gas increases with the increasing maturity (Ro) of source rocks and (b) decreases with the increasing Ro. In this paper, the correlations between the isobutane/n-butane ratios, dryness of natural gases, and the Ro values of source rocks of 77 gas samples from Cretaceous and Tertiary in Kuqa Depression, Tarim Basin, Triassic Xujiahe Formation in central Sichuan Basin, Carboniferous–Permian in Sulige and Yulin gas field, Ordos Basin, China, and 80 shale gas samples from Mississippian Barnett Shale in the Fort Worth Basin, the United States are analyzed to reveal the evolution of the isobutane/n-butane ratios, then mathematical models of the isobutane/n-butane ratios and Ro are attempted to be established. Results show that the isobutane/n-butane ratio initially increases and then decreases with increasing Ro, both coal-derived gas and oil-type gas. Diverse types of kerogens may be responsible for the different corresponding Ro values when the isobutane/n-butane ratios of gases reach their maximum values. The initial increase in the isobutane/n-butane ratios with increasing Ro is the reason that isobutane is mainly generated at a higher rate by carbonium ion reaction of α-olefins with protons during kerogen primary cracking at lower maturity, whereas free radical reactions to form n-butane relatively quickly during oil cracking at higher maturity and isobutane cracked at a higher rate during the wet gas cracking stage may result in the terminal decreases in the isobutane/n-butane ratios. Besides, mathematical models of the isobutane/n-butane ratios of different types of natural gas and maturity are established. Therefore, the maturity of gas source rock can be obtained quickly based on the models using the isobutane/n-butane ratio combined with other component information (such as dryness, wetness, etc.), which is of great significance to the characterization of natural gas maturity and gas source rock correlation.
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Nguyen, N. T., D. J. Oehlers, and M. A. Bradford. "Models for the Flexural Peeling of Angle Plates Adhesively Bonded to R-C Beams." Advances in Structural Engineering 1, no. 4 (October 1998): 287–300. http://dx.doi.org/10.1177/136943329800100405.
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The strength and stiffness of existing reinforced concrete beams may be enhanced by adhesively bonding angle section members to the soffit/side edges of reinforced concrete (RC) beams. This retrofitting is extremely important in improving the seismic performance of under reinforced RC beams which may suffer ductility problems in earthquakes, or whose strength has deteriorated due to unfavourable environmental factors. This paper develops generic mathematical models for simulating the debonding of angle plates glued to the edges of RC beams as a result of flexural peeling. It is shown that to achieve an accurate model the derivations are quite complex, but the experimental calibration renders the presentation of the model in a simple format. The models have been validated with experimental results.
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Verdério Júnior, S. A., V. L. Scalon, S. R. Oliveira, P. C. Mioralli, and E. Avallone. "DIMENSIONLESS PHYSICAL-MATHEMATICAL MODELING OF TURBULENT NATURAL CONVECTION." Revista de Engenharia Térmica 20, no. 3 (October 10, 2021): 37. http://dx.doi.org/10.5380/reterm.v20i3.83269.
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Natural convection heat transfer is present in the most diverse applications of Thermal Engineering, such as in electronic equipment, transmission lines, cooling coils, biological systems, etc. The correct physical-mathematical modeling of this phenomenon is crucial in the applied understanding of its fundamentals and the design of thermal systems and related technologies. Dimensionless analyses can be applied in the study of flows to reduce geometric and experimental dependence and facilitate the modeling process and understanding of the main influence physical parameters; besides being used in creating models and prototypes. This work presents a methodology for dimensionless physical-mathematical modeling of natural convection turbulent flows over isothermal plates, located in an “infinite” open environment. A consolidated dimensionless physical-mathematical model was defined for the studied problem situation. The physical influence of the dimensionless numbers of Grashof, Prandtl, and Turbulent Prandtl was demonstrated. The use of the Theory of Dimensional Analysis and Similarity and its application as a tool and numerical device in the process of building and simplifying CFD simulations were discussed.
Dissertations / Theses on the topic "Plates (Engineering) Cracking Mathematical models"
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Akileh, Aiman R. "Elastic-plastic analysis of axisymmetrically loaded isotropic circular and annular plates undergoing large deflections." PDXScholar, 1986. https://pdxscholar.library.pdx.edu/open_access_etds/3559.
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The concept of load analogy is used in the elastic and elastic-plastic analysis of isotropic circular and annular plates undergoing moderately large deflection. The effects of the nonlinear terms of lateral displacement and the plastic strains are considered as additional fictitious lateral loads, edge moments, and in-plane forces acting on the plate. The solution of an elastic or elastic-plastic Von Karman type plate is hence reduced to a set of two equivalent elastic plate problems with small displacements, namely, a plane problem in elasticity and a linear elastic plate bending problem. The method of finite element is employed to solve the plane stress problem. The large deflection solutions are then obtained by utilizing the solutions of the linear bending problems through an iterative numerical scheme. The flow theory of plasticity incorporating a Von Mises layer yield criterion and the Prandtl-Reuss associated flow rule for strain hardening materials is employed in this approach.
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Young, Andrew J. "Active control of vibration in stiffened structures." Title page, contents and abstract only, 1995. http://hdl.handle.net/2440/37722.
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Active control of vibration in structures has been investigated by an increasing number of researchers in recent years. There has been a great deal of theoretical work and some experiment examining the use of point forces for vibration control, and more recently, the use of thin piezoelectric crystals laminated to the surfaces of structures. However, control by point forces is impractical, requiring large reaction masses, and the forces generated by laminated piezoelectric crystals are not sufficient to control vibration in large and heavy structures. The control of flexural vibrations in stiffened structures using piezoceramic stack actuators placed between stiffener flanges and the structure is examined theoretically and experimentally in this thesis. Used in this way, piezoceramic actuators are capable of developing much higher forces than laminated piezoelectric crystals, and no reaction mass is required. This thesis aims to show the feasibility of active vibration control using piezoceramic actuators and angle stiffeners in a variety of fundamental structures. The work is divided into three parts. In the first, the simple case of a single actuator used to control vibration in a beam is examined. In the second, vibration in stiffened plates is controlled using multiple actuators, and in the third, the control of vibration in a ring-stiffened cylinder is investigated. In each section, the classical equations of motion are used to develop theoretical models describing the vibration of the structures with and without active vibration control. The effects of the angle stiffener(s) are included in the analysis. The models are used to establish the quantitative effects of variation in frequency, the location of control source(s) and the location of the error sensor(s) on the achievable attenuation and the control forces required for optimal control. Comparison is also made between the results for the cases with multiple control sources driven by the same signal and with multiple independently driven control sources. Both finite and semi-finite structures are examined to enable comparison between the results for travelling waves and standing waves in each of the three structure types. This thesis attempts to provide physical explanations for all the observed variations in achievable attenuation and control force(s) with varied frequency, control source location and error sensor location. The analysis of the simpler cases aids in interpreting the results for the more complicated cases. Experimental results are given to demonstrate the accuracy of the theoretical models in each section. Trials are performed on a stiffened beam with a single control source and a single error sensor, a stiffened plate with three control sources and a line of error sensors and a ring-stiffened cylinder with six control sources and a ring of error sensors. The experimental results are compared with theory for each structure for the two cases with and without active vibration control.Thesis (Ph.D.)--Mechanical Engineering, 1995.
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Liu, Bing 1975. "FE analysis of plastic buckling of plates with initial imperfections and simulation of experiments." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100251.
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The general problem of plastic buckling of flat metal plates is a fundamental area of investigation in mechanics not only because of its intrinsic importance in the design of engineering structures, but also because it still has not been settled in a satisfying manner. Which theory of plasticity is the correct one to predict the buckling loads in the plastic range is a long-argued problem.This thesis presents finite element analyses of plastic buckling and postbuckling behaviour of columns and plates, taking into account the presence of initial out-of-plane imperfections. The FE programs constructed by the author for this purpose are used to analyze the imperfection growth of such columns and plates under axial loading and simply supported edge conditions. The material behaviour is modeled according to both the incremental and the deformation theories of strain-hardening plasticity. The programs combine both the geometric and material nonlinearities to trace the load-deflection behaviours of these structures in prebuckling (up to the maximum load) as well as postbuckling ranges. The results of the analyses for plates show the extreme sensitivity of the incremental theory, and the relative insensitivity of the deformation theory, to the initial imperfections.
The programs are used to simulate the plastic buckling experiments on Aluminum tubes, taking into account their measured imperfections. The imperfection growth analyses demonstrate that the maximum load predictions of the incremental theory are quite close to those recorded in the experiments.
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Robbins, Donald H. "Hierarchical modeling of laminated composite plates using variable kinematic finite elements and mesh superposition." Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/40117.
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CHAKRABARTI, SEKHAR KUMAR. "INELASTIC BUCKLING OF GUSSET PLATES." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184188.
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The strength and behavior of gusset plates in buckling is evaluated herein based on data from the experimental investigations conducted by other researchers and the analytical work presented herein. A set of design guidelines has been recommended through the review of the current practice. Representative single and double brace gusset plates normally adopted for connections with compressive bracing/diagonal members in braced frames and trusses, were modeled and analyzed using linear and nonlinear finite element methods to determine the buckling loads. The buckling analysis data along with the test data indicated the occurrence of inelastic buckling of the gusset plates. Current design practice and a set of formulas for determination of gusset plate thickness have been reviewed. A set of guidelines has been recommended for the design and evaluating gusset plate buckling loads.
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Abel, Mary Sue M. "Four-bolt extended unstiffened moment end-plate connections." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-11242009-020221/.
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Montgomery, Darcy Thomas. "Milling of flexible structures." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29689.
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Current manufacturing research aims at increasing productivity by optimal selection of process parameters. This is accomplished by understanding the fundamental physics of individual manufacturing processes.
In this thesis, peripheral milling of very flexible cantilevered plates is studied. The static and dynamic deflections of the plate under periodic milling forces are modelled. A new dynamic cutting force model is developed which considers five discrete zones of relative motion between the tool and the workpiece. The kinematics of both milling and vibratory motions are modelled, which is an original research contribution in this area. It is shown that the penetration of the tool into the workpiece during vibratory cutting has a strong influence on the damping and stiffness characteristics of the milling process.
A structural model of a discontinuous cantilevered plate is determined using the finite element method. A reduced order structural model at the tool-workpiece contact zone is implemented for discrete time response analysis of the plate under cutting force excitations during milling. The closed loop dynamic behaviour of the system is modelled and taken into account in the analysis. Simulations of plate machining are compared with experimental results. A model of the surface finish generation mechanism is deduced from the analysis and experimental results.
Applications of this research include peripheral milling of integral jet engine impellers, computer disk drives and other flexible mechanical components.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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張啓軍 and Qijun Zhang. "The Galerkin Element Method and power flow in acoustic-structural problems with damped sandwich plates." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31239742.
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Nugroho, Widijanto Satyo. "Waves generated by a load moving on an ice sheet over water." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ32720.pdf.
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Yu, Wenbin. "Variational asymptotic modeling of composite dimensionally reducible structures." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/12225.
Full textBooks on the topic "Plates (Engineering) Cracking Mathematical models"
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Michel, Salaun, ed. Mathematical analysis of thin plate models. Paris: Springer, 1996.
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Louis, Lions Jacques, ed. Modelling analysis and control of thin plates. Paris: Masson, 1988.
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1932-, Gilbert Robert P., and Hackl K, eds. Asymptotic theories for plates and shells. Harlow, Essex, England: Longman Scientific & Technical, 1995.
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1945-, Reddy J. N., ed. Mechanics of laminated composite plates and shells: Theory and analysis. 2nd ed. Boca Raton: CRC Press, 2004.
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The theory of piezoelectric shells and plates. Boca Raton: CRC Press, 1994.
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Hofstetter, Günter, and Günther Meschke. Numerical modeling of concrete cracking. Wien: Springer, 2011.
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Szabo, B. A. Hierarchic plate and shell models based on p-extension. St. Louis, MO: Center for Computational Mechanics, Washington University, 1987.
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Vibration analysis of plates by the superposition method. Singapore: World Scientific, 1999.
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A mathematical analysis of bending of plates with transverse shear deformation. Harlow, Essex, England: Longman Scientific & Technical, 1990.
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Blaauwendraad, J. Plates and FEM: Surprises and Pitfalls. Dordrecht: Springer Science+Business Media B.V., 2010.
Find full textConference papers on the topic "Plates (Engineering) Cracking Mathematical models"
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Al-Rifaie, Wail, and Waleed K. Ahmed. "An Experimental Investigation on the Shear Strength of Ferrocement Reinforced With Hexagonal Mesh." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-50213.
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Ferrocement is characterized by fine diameter mesh reinforcement, and size of mesh opening, and the surface area per unit volume of mortar may be as much as ten times that in conventional reinforced concrete. The behavior of ferrocement is characterized by volume fraction of the fibers Vfx and Vfy in x and y directions and the specific surfaces of the mesh SLx and SLy. An experimental investigation on the shear strength of ferrocement plate reinforced with hexagonal mesh is carried out. Ferrocement square plate specimens were cast and tested. A total of 24 simply supported square plates (500×500mm) having mortar with cement/ sand proportions 1: 2 and 1: 3 by weight have been cast and tested under ‘patch’ load varying the number of mesh layers, the plate thickness, the size of the mesh opening and the arrangement and orientation of the mesh. Woven hexagonal mesh has been used. All plate specimens have been tested with their edges simply supported over a span of 450mm in two directions. During tests, central patch loads of size 100×100mm at the center of each plate specimens were applied to the models through a universal testing machine of 250 ton capacity. Having located the specimens within its support, series of patch load increments were then applied to the plate up to failure loads. The plate behavior has been presented in the form of the first cracking load Pcr and the ultimate load Pu which is the total patch load at failure. It was observed that the first cracking load is influenced by the ultimate mortar strength and not much affected by volume content of reinforcement. The slope of the curves at collapse indicates that the load carrying capacity is highly influenced by the steel volume content and the tensile strength of the mesh reinforcement while the contribution of mortar is negligible. The failure loads in the plates with closely spaced wires were higher as compared to the plates with widely spaced wires. There is an increase in the value of failure load Pu for the plate specimens with orthogonally oriented mesh layers as compared to the specimens with twin layers. An important conclusions regarding the plate behavior are drawn and expression to estimate the first cracking load is proposed. A comparison of the first cracking load values with those obtained using the proposed expression. It is seen that the proposed expression gives a reasonable estimate of the first cracking load.
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Senjanović, Ivo, Nikola Vladimir, Dae-Seung Cho, and Tae-Muk Choi. "Vibration Analysis of Thick Plates: Analytical and Numerical Approaches." In ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-23273.
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In this paper an examination of methods for vibration analysis of moderately thick rectangular plates has been presented. First, the state-of-the art in thick plate vibration theories and analysis methods is described and it is followed with basic equations of the original Mindlin theory, which represents a starting point for the development of all other mathematical models. Then, the problem of analytical solving of equilibrium equations is considered based on the modified Mindlin theory of thick plate vibrations, which has been published in the literature recently. Further, energy methods that can be applied to arbitrary boundary conditions are discussed and outline of the assumed mode method is presented. Finally, in the context of numerical methods a new quadrilateral finite element, based on the above mentioned advanced thick plate theory, is included. It should be emphasized that it doesn’t suffers of shear locking problem associated with finite elements, due to natural relation among bending and shear polynomials, and moreover, it gives very accurate results. Application of the presented methods is illustrated by several numerical examples which include natural vibration analyses of rectangular plates with various thicknesses and different combinations of boundary conditions (simply supported, clamped, free and elastically restrained). Comparisons of natural frequencies and mode shapes with results available in the relevant literature and with those obtained by the commercial finite element software are also provided.
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Yamamoto, Yoshihito, Soichiro Okazaki, Hikaru Nakamura, Masuhiro Beppu, and Taiki Shibata. "Crack Propagation and Local Failure Simulation of Reinforced Concrete Subjected to Projectile Impact Using RBSM." In ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/omae2016-54969.
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In this paper, numerical simulations of reinforced mortar beams subjected to projectile impact are conducted by using the proposed 3-D Rigid-Body-Spring Model (RBSM) in order to investigate mechanisms of crack propagation and scabbing mode of concrete members under high-velocity impact. The RBSM is one of the discrete-type numerical methods, which represents a continuum material as an assemblage of rigid particle interconnected by springs. The RBSM have advantages in modeling localized and oriented phenomena, such as cracking, its propagation, frictional slip and so on, in concrete structures. The authors have already developed constitutive models for the 3D RBSM with random geometry generated Voronoi diagram in order to quantitatively evaluate the mechanical responses of concrete including softening and localization fractures, and have shown that the model can simulate cracking and various failure modes of reinforced concrete structures. In the target tests, projectile velocity is set 200m/s. The reinforced mortar beams with or without the shear reinforcing steel plates were used to investigate the effects of shear reinforcement on the crack propagation and the local failure modes. By comparing the numerical results with the test results, it is confirmed that the proposed model can reproduce well the crack propagation and the local failure behaviors. In addition, effects of the reinforcing plates on the stress wave and the crack propagation behaviors are discussed from the observation of the numerical simulation results. As a result, it was found that scabbing of reinforced mortar beams subjected to high velocity impact which is in the range of the tests is caused by mainly shear deformation of a beam.
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Allen, D. H., and C. R. Searcy. "Prediction of Damage Evolution in Laminated Composites Subjected to Impact Loading." In ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-1183.
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Abstract Many structural components undergo significant structural damage when they are subjected to ballistic impact. Because this damage can lead to failure of monolithic components to perform their intended missions, composite structures have recently been developed to better withstand impact. The intent of these new types of composites is to provide tougher, yet lighter structures that will withstand significantly larger ballistic impact energies than do traditional monolithic structures. Although these new composite structures do indeed appear to provide increased toughness, they also undergo much more complicated damage mechanisms, so that it has become difficult to accurately predict the limits of usefulness of structures made with these materials. It is evident that in order to develop design tools that can be used to assess the performance characteristics of these composite components, it is necessary to develop models that can accurately predict the evolution of damage of various types during actual impact events. This paper outlines a methodology based in continuum mechanics and utilizing advanced damage, fracture, and computational mechanics to obtain accurate predictions of damage evolution in laminated composite structures during ballistic impact. The evolution of damage is accounted for by the use of a cohesive zone model capable of predicting matrix, fiber, and interply cracking in ductile polymers. This model has been implemented to a global three dimensional finite element computer code for the purpose of predicting the evolution of damage during impact. The resulting algorithm is utilized herein to predict the types of damage events experimentally observed in laminated composite plates subjected to impact, and comparisons are made to two experimental results obtained by the author and coworkers.
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Park, Chang J., and Deborah A. Kaminski. "Contact Area and Thermal Contact Resistance in an Ideal Bolted Joint: Part 1 — Study of Contact Area." In ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-1218.
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Abstract The contact area at the interface of a bolted joint was investigated analytically, experimentally and numerically. Consideration was restricted to an ideal two-plate model for which the interface was perfectly flat. The two plates made circular contact under uniform axisymmetric normal loading. These investigations included the effect of important system parameters such as plate thickness, material properties and loading radius. In the analytical study, a two-plate model with an infinite radius, which had no center (bolt) hole, was mathematically analyzed. The normal stress distribution at the interface was used to predict the contact radius. Two alternative assumptions were considered: 1) continuous contact (no separation) at the interface, 2) discontinuous contact (separation beyond the contact region) at the interface. The continuous model was solved by a Hankel transform and the discontinuous model by a Hankel transform and singular integral formulation. In the experimental study, a visualization technique using monochromatic light was carried out with a bolted joint which consisted of a transparent polycarbonate plate and a metal plate so that direct calibration of the contact radius was possible. All the test plates had mirror-like surface finishes. In the numerical study, the finite element method was applied to two different two-plate models: one without a hole and the other with a hole. The results showed that the discontinuous model produced much closer agreement with the two-plate model with a hole than the continuous model, which produced a large discrepancy. The results also show that the effect of the bolt hole appeared to be insignificant. The physical behavior of the contact radius of a bolted joint can be well explained from the mathematical equation of the discontinuous model. The contact radii obtained from Part 1 were implemented in the study of the thermal contact resistance described in the companion paper.
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Akyuzlu, Kazim M., and David Coote. "Prediction of Ablation Rates From Solid Surfaces Exposed to High Temperature Gas Flow." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-65417.
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A mathematical model and a solution algorithm is developed to study the physics of high temperature heat transfer and material ablation and identify the problems associated with the flow of hydrogen gas at very high temperatures and velocities through pipes and various components of Nuclear Thermal Rocket (NTR) motors. Ablation and melting can be experienced when the inner solid surface of the cooling channels and the diverging-converging nozzle of a Nuclear Thermal Rocket (NTR) motor is exposed to hydrogen gas flow at temperatures around 2500 degrees Kelvin and pressures around 3.4 MPa. In the experiments conducted on typical NTR motors developed in 1960s, degradation of the cooling channel material (cracking in the nuclear fuel element cladding) and in some instances melting of the core was observed. This paper presents the results of a preliminary study based on two types of physics based mathematical models that were developed to simulate the thermal-hydrodynamic conditions that lead to ablation of the solid surface of a stainless steel pipe exposed to high temperature hydrogen gas near sonic velocities. One of the proposed models is one-dimensional and assumes the gas flow to be unsteady, compressible and viscous. An in-house computer code was developed to solve the conservations equations of this model using a second-order accurate finite-difference technique. The second model assumes the flow to be three-dimensional, unsteady, compressible and viscous. A commercial CFD code (Fluent) was used to solve the later model equations. Both models assume the thermodynamic and transport properties of the hydrogen gas to be temperature dependent. In the solution algorithm developed for this study, the unsteady temperature of the pipe is determined from the heat equation for the solid. The solid-gas interface temperature is determined from an energy balance at the interface which includes heat transfer from or to the interface by conduction, convection, radiation, and ablation. Two different ablation models are proposed to determine the heat loss from the solid surface due to the ablation of the solid material. Both of them are physics based. Various numerical simulations were carried out using both models to predict the temperature distribution in the solid and in the gas flow, and then predict the ablation rates at a typical NTR motor hydrogen gas temperature and pressure. Solid mass loss rate per foot of a pipe was also calculated from these predictions. The results are presented for fully developed turbulent flow conditions in a sample SS pipe with a 6 inch diameter.
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Gonchikar, Ugrasen, Holalu Venkatadasu Ravindra, Prathik Jain Sudhir, Umeshgowda Bettahally Mahadevegowda, and Shankarnarayan Maskibail Suresh. "Estimation and Comparison of Welding Responses Using MRA, GMDH and ANN Technique of Al6061 and Al7075 Material in FSW." In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-11168.
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Abstract Friction Stir Welding (FSW) is a solid state welding which uses non-consumable steel rod to weld two materials. Friction stir welding is an emerging process which is based on frictional heat generated through contact between a non-consumable rotating tool and work piece. Friction stir welding technique possesses several advantages over other conventional types of welding due to the fact that process is carried out in solid state. Removal of melting helps in minimizing porosity and eliminates oxide inclusion. In this study, we focus on the optimization of the process parameters in friction stir welding of two different aluminium alloys (6061, 7075) using Taguchi method of experimental design. Al 6061 and Al 7075 are the two different alloys of aluminium. Among these Al 7075 has mechanical properties nearly double than that of Al 6061, but Al 6061 is used more extensively than Al 7075 because of its low cost. Al 6061 and Al 7075 being alloys of aluminium varies in the composition of alloying elements used in their manufacturing. Al 6061 has magnesium and silicon as its major alloying elements whereas Al 7075 has zinc as its primary alloying element. Al 6061 comes with medium to high strength, exhibit good toughness and surface finish, excellent resistance to corrosion at environmental conditions and another important property is its good weldability. Al 7075 being stronger than Al 6061 lacks in its resistance to corrosion and has poor weldability. Al 6061 is readily weldable but Al 7075 is not, because it is prone to micro-cracking during welding. This study also describes the relation between process parameters and their response of friction stir weld on ultimate tensile strength and hardness of composite materials using mathematical models. The process parameters considered are rotational speed, welding speed and number of passes. Different methodologies are used to develop the models to predict the responses and mechanical properties such as ultimate tensile strength and hardness. The objective of Multiple Regression Analysis (MRA) is to construct a model that explains as much as possible, the variability in a dependent variable, using several independent variables. Group Method of data Handling Technique (GMDH) is a family of inductive algorithms for computer-based mathematical modelling of multi-parametric datasets that features fully automatic structural and parametric optimization of models. GMDH is used in such fields as data mining, knowledge discovery, prediction, complex systems modelling, optimization and pattern recognition. As the machining process is non-linear and time dependent, it is difficult for the traditional identification methods to provide an accurate model. Compared to traditional computing methods, the Artificial Neural Network’s (ANN) are robust and global. Estimation and comparison of machining responses were carried out by MRA, GMDH and ANN.
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Fagley, John, Wenbin Gu, and Lee Whitehead. "Thermal Modeling of a PEM Fuel Cell." In ASME 2004 2nd International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2004. http://dx.doi.org/10.1115/fuelcell2004-2464.
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Mathematical modeling of fuel cells can take place at many different levels of detail, from simplified spreadsheet representations to detailed CFD (computational fluid dynamics) models. All of these levels are utilized within General Motors Corporation Fuel Cell Activities. This paper describes the development and application of a model used for analysis of the thermal aspects of a PEM fuel cell. The model domain is a single cell in a fuel cell stack, which is broken into between ten and two hundred control volumes. Each control volume includes eleven lumps; one each for anode, cathode and coolant streams, three for diffusion media/membrane electrode assembly (DM/MEA), four for the cathode portion of the bipolar plate, and four for the anode portion of the bipolar plate. The resulting simulation has the following features; (1) Unlike most CFD representations which typically contain hundreds of thousands or even millions of elements, the model described here does not solve the equations of motion to determine velocity profiles in the anode, cathode or coolant channels. Rather, the flow rates in the anode and cathode flow fields are specified by the user. Typically, uniform flow profiles are assumed, although maldistributed flows may be specified as well. (2) By using between ten and two hundred control volumes, the model can represent the spatial variations of RH (relative humidity) and temperature, (3) The relatively low computational overhead of the modeling approach described here (as compared to a more detailed CFD approach) facilitates dynamic simulation of the cell, i.e. transient thermal response of the system can be simulated, (4) Heat effects simulated include heat released by electrochemical reaction, convection from the fluid streams to the solid lumps (DM/MEA, cathode and anode plates), and conduction in the bipolar plates. This paper also describes some of the ways the model has been used to analyze thermal aspects of fuel cell operations; (1) Sensitivity of the temperature difference between the DM/MEA and coolant plate thermal conductivity and contact resistance, and (2) Impact of coolant flow field (cross-flow and co-flow) on cathode RH. Other potential applications of this type of model are also outlined, including modeling of the cell during transient operation, and start-up.
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John, Carolyn J., Consuelo E. Guzman-Leong, Thomas C. Esselman, and Sam L. Harvey. "Methods to Define Failure Probability for Power Plant Heat Exchangers." In ASME 2017 Power Conference Joint With ICOPE-17 collocated with the ASME 2017 11th International Conference on Energy Sustainability, the ASME 2017 15th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2017 Nuclear Forum. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/power-icope2017-3367.
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In response to the technical challenges faced by aging plant systems and components at nuclear power plants (NPP), the Electric Power Research Institute (EPRI) has a product entitled Integrated Life Cycle Management (ILCM). The ILCM software is a quantitative tool that supports capital asset and component replacement decision-making at NPPs. ILCM is comprised of models that predict the probability of failure (PoF) over time for various high-value components such as steam generators, turbines, generators, etc. The PoF models allow the user to schedule replacements at the optimum time, thereby reducing unplanned equipment shutdowns and costs. This paper describes a mathematical model that was developed for critical heat exchangers in a power plant. The heat exchanger model calculates the probability of the tubes, shell, or internals failing individually, and then accumulates the failures across the heat exchanger sub-components. The dominant degradation mechanisms addressed by the model include stress corrosion cracking, wear, microbiologically influenced corrosion, flow accelerated corrosion, and particle-induced erosion. The heat exchanger model combines physics-based algorithms and operating experience distributions to predict the cumulative PoF over time. The model is applicable to shell and tube heat exchangers and air-to-water heat exchangers. Many different types of fluids including open cycle fresh water, closed cycle fresh water, sea water, brackish water, air, closed cooling water, steam, oil, primary water, and condensate are included. Examples of PoF over time plots are also provided for different fluid types and operating conditions.