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Littérature scientifique sur le sujet « Structural stability Mathematical models »

Auteur : Grafiati

Publié le 4 juin 2021

Mis à jour le 30 janvier 2023

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Articles de revues sur le sujet "Structural stability Mathematical models"

Kostrobij, P. P., et I. A. Ryzha. « Stability of carbon monoxide oxidation process on gold nanoparticles ». Mathematical Modeling and Computing 8, n^o 1 (2020) : 116–24. http://dx.doi.org/10.23939/mmc2021.01.116.

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The stability conditions for mathematical models of carbon monoxide oxidation on the surface of gold nanoparticles are investigated. The cases of reaction mechanisms of one-step and step-by-step transformation of reagents are consecutively considered. Using the stability analysis by Lyapunov method, it is shown that models which take into account the possibility of structural changes of the catalyst surface can predict the occurrence of oscillatory mode in the system as a result of Hopf instability.

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Smirnov, Sergey N. « Realistic Models of Financial Market and Structural Stability ». Journal of Mathematics 2021 (21 juin 2021) : 1–8. http://dx.doi.org/10.1155/2021/6651324.

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The main aim of this article is to show the role of structural stability in financial modelling; that is, a specific “no-arbitrage” property is unaffected by small perturbations of the model’s dynamics. We prove that under the structural stability assumption, given a convex compact-valued multifunction, there exists a stochastic transition kernel with supports coinciding with this multifunction and one that is strong Feller in the strict sense. We also demonstrate preservation of structural stability for sufficiently small deviations of transition kernels for different probability metrics.

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DUCROT, ARNAUD. « STRUCTURAL STABILITY OF COMBUSTION MODELS WITH COMPLEX CHEMISTRY ». Mathematical Models and Methods in Applied Sciences 16, n^o 06 (juin 2006) : 793–817. http://dx.doi.org/10.1142/s0218202506001352.

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This work is devoted to the study of semi-linear elliptic systems in unbounded cylinders with linear dependence of the components of the nonlinearity vector. We reduce the study of such a problem with non-Fredholm operator to the study of a perturbation of some reaction-diffusion operator which satisfies the Fredholm property. Then sufficient conditions that ensure the structural stability of particular solutions are given. These conditions are applied to derive some existence results for some combustion model with complex chemistry and for some KPP like system.

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Kulik, Anatoliy, Konstantin Dergachov, Sergey Pasichnik et Sergey Yashyn. « Motions models of a two-wheeled experimental sample ». RADIOELECTRONIC AND COMPUTER SYSTEMS, n^o 1 (27 février 2021) : 40–49. http://dx.doi.org/10.32620/reks.2021.1.03.

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The subject of study is the physical processes of translational and angular motion of a two-wheeled experimental sample. The goal is to develop physical, mathematical, and graphic models of the translational and angular motions of a two-wheeled experimental sample as an object of automatic control. The objectives: to form physical models of a two-wheeled experimental sample; to develop a nonlinear mathematical description of the processes of translational and angular sample`s motions using the Lagrange approach; to obtain a linearized mathematical sample`s description as an object of automatic control in the state space and frequency domain; to generate graphic models in the form of structural diagrams in the time and frequency domains; to analyze the functional properties of an object of automatic control: stability, controllability, observability, structural and signal diagnosability concerning violations of the functional properties of electric drives and sensors of the angular position of the body and wheels. The methods of the study: the Lagrange method, Taylor series, state-space method, Laplace transformations, Lyapunov, Kalman criteria, and diagnosability criterion. The results: physical models of a two-wheeled experimental sample have been obtained in the form of a kinematic diagram of the mechanical part and the electric circuit of an electric drive; mathematical descriptions of translational and angular motions have been developed in nonlinear and linearized forms; structural diagrams have been developed; functional characteristics of a two-wheeled experimental model as an object of automatic control have been analyzed to solve problems of control algorithms synthesis. Conclusions. The scientific novelty lies in obtaining new models that describe the translational and angular motion of a two-wheeled experimental model as an object of automatic control. The obtained models differ from the known ones by considering the dynamic properties of sensors and electric drives, as well as the relationship of movements.

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Nguyen, Ngoc Hung, Van Phan Do et Hoa Tien Vu. « Estimating Disturbance Torque Effects on the Stability and Control Performance of Two-Axis Gimbal Systems ». Journal of the Russian Universities. Radioelectronics 25, n^o 4 (29 septembre 2022) : 63–71. http://dx.doi.org/10.32603/1993-8985-2022-25-4-63-71.

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Introduction. Two-axis gimbal systems are applied for stabilizing and controlling the line of sight (LOS) of an optical or imaging system mounted on a moving vehicle. Gimbal systems are intended to isolate various disturbance torques and control the LOS toward the direction of a target. Two-axis gimbals can be of two main types, namely Yaw-Pitch and Swing-Roll type. In this article, we focus on investigating mathematical models of two-axis gimbals, which describe the impact of cross-disturbance torques on their stability and control performance. Simulations were conducted to compare advantages and disadvantages of the two types of two-axis gimbals.Aim. To study mathematical models describing the impact of cross-disturbance torques on the stability and control performance of two-axis gimbals.Materials and methods. Mathematical models of two-axis gimbal systems were synthesized by the Lagrange method. The operation of two-axis gimbal systems was simulated in the Matlab-Simulink environment. Results. Mathematical models and structural diagrams of the synthesized Yaw-Pitch and Swing-Roll gimbals were obtained. The conducted simulations of typical cases revealed different cross-disturbance effects.Conclusion. Motion equations for Swing-Roll and Yaw-Pitch gimbals were derived using similar methodology. The impact of cross-disturbance torques on gimbal systems was evaluated. The obtained results form a basis for selecting an optimal structure of tracking systems meeting the desired characteristics.

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WYLLER, JOHN, PATRICK BLOMQUIST et GAUTE T. EINEVOLL. « ON THE ORIGIN AND PROPERTIES OF TWO-POPULATION NEURAL FIELD MODELS - A TUTORIAL INTRODUCTION ». Biophysical Reviews and Letters 02, n^o 01 (janvier 2007) : 79–98. http://dx.doi.org/10.1142/s1793048007000441.

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Neural field models have a long tradition in mathematical neuroscience, and in the present tutorial paper we outline the neurobiological and biophysical origin of such models, in particular two-population field models describing excitatory and inhibitory neurons interacting via nonlocal spatial connections. Results from investigations of such models on the existence and stability of stationary localized activity pulses ('bumps') and generation of stationary spatial and spatiotemporal oscillations through Turing-type instabilities are described.

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Corradi, Valentina, et Norman R. Swanson. « Testing for structural stability of factor augmented forecasting models ». Journal of Econometrics 182, n^o 1 (septembre 2014) : 100–118. http://dx.doi.org/10.1016/j.jeconom.2014.04.011.

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Maldhure, Atul V., et Jayant D. Ekhe. « Effect of modifications of lignin on thermal, structural, and mechanical properties of polypropylene/modified lignin blends ». Journal of Thermoplastic Composite Materials 30, n^o 5 (22 octobre 2015) : 625–45. http://dx.doi.org/10.1177/0892705715610402.

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Use of organic biomass, industrial waste lignin, was considered interesting due to its easy availability, polymeric nature, and ample scope to modify with an aim to replace conventional metal oxides to achieve improved properties of the blend when blended with polyolefins. To study the effect of chemical modification of lignin on the thermal, structural, and mechanical properties of polypropylene (PP)/modified lignin blends, purified industrial waste lignin was modified by two different chemical methods and blended in various proportions in PP matrix. The thermal stability of the blends was studied by thermogravimetric analysis, whereas melting and crystallization behavior of blends was studied by non-isothermal differential scanning calorimetry. The results show improved thermal stability of blends with increasing modified lignin proportion in the PP matrix. More depression in melting point was observed in PP/alkylated lignin blends than PP/arylated lignin blends, whereas addition of alkylated lignin shows polymorphism in PP matrix. Intermolecular interactions between blend components have been evaluated by applying several mathematical models to experimental mechanical property data. In most of the cases, good agreement has been obtained between the predictions made by using mathematical models and interpretations done on the basis of experimental data, showing the suitability of these models for predicting the mechanical properties of PP/modified lignin blends.

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Barigozzi, Matteo, et Lorenzo Trapani. « Sequential testing for structural stability in approximate factor models ». Stochastic Processes and their Applications 130, n^o 8 (août 2020) : 5149–87. http://dx.doi.org/10.1016/j.spa.2020.03.003.

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Akimov, Pavel A., Alexandr M. Belostosky, Marina L. Mozgaleva, Mojtaba Aslami et Oleg A. Negrozov. « Correct Multilevel Discrete-Continual Finite Element Method of Structural Analysis ». Advanced Materials Research 1040 (septembre 2014) : 664–69. http://dx.doi.org/10.4028/www.scientific.net/amr.1040.664.

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The distinctive paper is devoted to correct multilevel discrete-continual finite element method (DCFEM) of structural analysis based on precise analytical solutions of resulting multipoint boundary problems for systems of ordinary differential equations with piecewise-constant coefficients. Corresponding semianalytical (discrete-continual) formulations are contemporary mathematical models which currently becoming available for computer realization. Major peculiarities of DCFEM include universality, computer-oriented algorithm involving theory of distributions, computational stability, optimal conditionality of resulting systems and partial Jordan decompositions of matrices of coefficients, eliminating necessity of calculation of root vectors.

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Thèses sur le sujet "Structural stability Mathematical models"

鄭定陽 et Dingyang Zheng. « Vibration and stability analysis of plate-type structures under movingloads by analytical and numercial methods ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31239791.

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Uliana, David A. « The effects of earthquake excitations on reticulated domes ». Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/45667.

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Comparisons were made on the behavior of two full-sized reticulated domes subjected to uniform static loads only and uniform static loads with earthquake excitations. Space truss elements were used in the dome models. The stiffness matrix of the space truss element allows for the nonlinear strain-displacement behavior and the stress-strain behavior of the material is modeled with a bilinear approximation. The nonlinear solution technique is the Newton-Raphson method while the direct integration technique is the Newmark- Beta method.

The joint displacements for the static and the dynamic analyses were compared for both domes along with the axial stresses in all members. The percentage increases in the axial stresses of the dynamic analyses as compared to those of the static analyses were determined.

The reticulated domes used in the study were found to bet capable of withstanding the earthquake excitations when subjected to various uniform loads without failure.

Master of Science

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Choi, Yam-ming Kelvin, et 蔡任明. « Use of block theory in tunnel stability analysis ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B45014358.

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Walker, John Griffith. « Investigation of induced strain actuator patches implementing modeling techniques and design considerations to reduce critical stress ». Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-03042009-040453/.

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Yi, Tianyi. « Experimental Investigation and Numerical Simulation of an Unreinforced Masonry Structure with Flexible Diaphragms ». Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5149.

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Unreinforced masonry (URM) construction, which has been widely used in the United States, presents a large threat to life safety and regional economic development because of its poor seismic resistance. In this research, the nonlinear seismic properties of URM structures were investigated via a quasi-static test of a full-scale two-story URM building and associated analytical and numerical studies. The tests of the 24ft. by 24ft. in plan 22ft. high URM building revealed that the damage was characterized by (1) the formation of large discrete cracks in the masonry walls and (2) the rocking and sliding of URM piers. Both of these results were consistent with the predictions based on individual component properties obtained in previous research. However, the tests also revealed significant global behavior phenomena, including flange effects, overturning moment effects, and the formation of different effective piers in a perforated wall. This global behavior greatly affected the response of the URM building tested. In order to understand the nonlinear behavior of the test structure, a series of analytical studies were conducted. First, at the material level, a mechanical key model was proposed to describe the failure of URM assemblages under a biaxial state of stress. Second, at the component level, an effective pier model was developed to illustrate the mixed failure modes of a URM pier and its nonlinear force-deformation relationship. Third, at the structure level, a nonlinear pushover model was built using the mechanical models at the material and component levels to describe the nonlinear properties of a URM building. This nonlinear pushover model and a three-dimensional finite element model were employed to analyze the test structure. Both gave results in good agreement with the test data. Improvements to current provisions for the evaluation of existing masonry structures were proposed.

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Siegel, Paul B. « The relationship between changing economic structure and performance : diversification, diversity, growth, stability, and distribution impacts ». Diss., Virginia Tech, 1992. http://hdl.handle.net/10919/40017.

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Stephens, Max Taylor. « Numerical and Experimental Analysis of Composite Sandwich Links for the LCF System ». PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/579.

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Shear links are used as fuse elements in lateral load resisting systems to provide ductility and dissipate seismic energy. These links have traditionally been employed in eccentrically braced frames, but have more recently been suggested for use in the innovative linked column frame system (LCF). Current design specifications for shear links require intermediate web stiffeners to provide out-of-plane web stability so ductility requirements can be achieved. This research focused on moving from discrete transverse web stiffening to continuously stiffened webs in built up shear links. Built up links were designed to yield in shear when subjected to severe cyclic loading, however the webs of the links were designed using two metal sheets joined by an elastic core. These composite "sandwich" webs allowed for an increase in web thickness (and inherent flexural rigidity) without increasing the shear strength of the links. Numerical and experimental investigations were conducted to assess the performance of composite sandwich links subjected to severe loading. Numerical results showed improved web behavior in sandwich links in which the core material was assigned an elastic modulus greater than 5000psi. Due to fabrication limitations, experimental specimens were fabricated with a core material elastic modulus of 1000psi. These specimens did not perform as well as unstiffened base case links in terms global hysteretic behavior or ductility.

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Nassiri, Esmail. « Modelling nonlinear behaviour of two-dimensional steel structures subjected to cyclic loading ». Thesis, Queensland University of Technology, 1998.

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Burnham, Christian James. « Structural and dynamical properties of mathematical water models ». Thesis, University of Salford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299208.

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Musa, Zulkarnain 1964. « An accelerated conjugate direction procedure for slope stability analysis ». Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276912.

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CSLIP2 (De Natale, 1987) is the only slope stability program that utilizes a "direction set" optimization routine in its search for the minimum safety factor. However, CSLIP2 which employs Powell's Conjugate Direction Method permits only the horizontal and vertical directions (x and y) to be used as the initial direction set. The efficiency of the existing search routine is improved by replacing the x-y coordinate directions with initial directions that are parallel to and perpendicular to the principal axis of the safety factor contours.

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Livres sur le sujet "Structural stability Mathematical models"

Stolz, Claude. Stabilité des matériaux et des structures. Palaiseau [France] : Editions de l'Ecole polytechnique, 2003.

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Pawlikowski, Jan. Oddziaływania stałe i zmienne na konstrukcje budynków : Permanent and variable actions on buildings structures. Warszawa : Wydawnictwa Instytutu Techniki Budowlanej, 2010.

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Kindmann, Rolf. Stahlbau. 4^e éd. Berlin : Ernst & Sohn, 2008.

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Dunant, Halim, et Fleming Andrew J, dir. Spatial control of vibration : Theory and experiments. River Edge, N.J : World Scientific, 2003.

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Pawlikowski, Jan. Oddziaływania stałe i zmienne na konstrukcje budynków = : Permanent and variable actions on buildings [sic] structures. 2^e éd. Warszawa : Wydawnictwa Instytutu Techniki Budowlanej, 2007.

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Slivker, V. I. (Vladimir Isaevich), dir. Handbook of mechanical stability in engineering. Singapore : World Scientific Pub., 2013.

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Juyi, Cao, et Zhang Kuanquan, dir. Gong cheng jie gou ke kao du. Beijing : Ke xue chu ban she, 2011.

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Skrzypek, Jacek J. Modeling of material damage and failure of structures : Theory and applications. Berlin : Springer, 1999.

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Skrzypek, Jacek. Modeling of material damage and failure of structures : Theory and applications. Berlin : Springer, 1999.

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Carr, Peter. Development of a method to make use of sensitivity studies and its application to analysis of uncertainties in environmental loading on offshore structures. London : H.M.S.O., 1989.

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Chapitres de livres sur le sujet "Structural stability Mathematical models"

Hritonenko, Natali, et Yuri Yatsenko. « Variational Models and Structural Stability ». Dans Applied Mathematical Modelling of Engineering Problems, 85–104. Boston, MA : Springer US, 2003. http://dx.doi.org/10.1007/978-1-4419-9160-7_3.

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Ramadan, Rabie, Rodolfo Ruben Rosales et Benjamin Seibold. « Structural Properties of the Stability of Jamitons ». Dans Mathematical Descriptions of Traffic Flow : Micro, Macro and Kinetic Models, 35–62. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-66560-9_3.

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Zhou, Yicang, Baojun Song et Zhien Ma. « The Global Stability Analysis for an SIS Model with Age and Infection Age Structures ». Dans Mathematical Approaches for Emerging and Reemerging Infectious Diseases : Models, Methods, and Theory, 313–35. New York, NY : Springer New York, 2002. http://dx.doi.org/10.1007/978-1-4613-0065-6_18.

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Shikhovtseva, Elena S. « Conducting Channels Structure and Dielectric-Metal Switching Stability in Thin amorphous Films ». Dans Mathematical Models of Non-Linear Excitations, Transfer, Dynamics, and Control in Condensed Systems and Other Media, 301–10. Boston, MA : Springer US, 1999. http://dx.doi.org/10.1007/978-1-4615-4799-0_25.

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Bhattacharya, Paritosh, Susmita Paul et K. S. Choudhury. « Analysis on Food Web Structure, Interaction, Strength and Stability of Different Mathematical Models of Prey and Predator ». Dans Lecture Notes in Electrical Engineering, 207–17. New Delhi : Springer India, 2014. http://dx.doi.org/10.1007/978-81-322-1817-3_22.

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Godehardt, Erhard. « Mathematical Symbols and Notation ». Dans Graphs as Structural Models, 1–4. Wiesbaden : Vieweg+Teubner Verlag, 1988. http://dx.doi.org/10.1007/978-3-322-96310-9_1.

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Weinberger, H. F. « Some Mathematical Aspects of Buckling ». Dans Summation Theorems in Structural Stability, 1–37. Vienna : Springer Vienna, 1995. http://dx.doi.org/10.1007/978-3-7091-2912-8_1.

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Jeffries, Clark. « Qualitative Stability of Ecosystem Models ». Dans Mathematical Modeling in Ecology, 128–43. Boston, MA : Birkhäuser Boston, 1989. http://dx.doi.org/10.1007/978-1-4612-4550-6_6.

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Fok, Alex, et Hooi Pin Chew. « Stability of Dental Implants ». Dans Mathematical Models for Dental Materials Research, 55–64. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-37849-3_8.

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Del Prete, Eugenio, Serena Dotolo, Anna Marabotti et Angelo Facchiano. « Basic Exploratory Proteins Analysis with Statistical Methods Applied on Structural Features ». Dans Mathematical Models in Biology, 173–87. Cham : Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-23497-7_13.

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Actes de conférences sur le sujet "Structural stability Mathematical models"

Ashimov, Abdykappar A., Bahyt T. Sultanov, Yuriy V. Borovskiy, Zheksenbek M. Adilov, Askar A. Ashimov, Muhammed Hasan Aslan, Ahmet Yayuz Oral, Mehmet Özer et Süleyman Hikmet Çaglar. « Structural Stability of Mathematical Models of National Economy ». Dans INTERNATIONAL CONGRESS ON ADVANCES IN APPLIED PHYSICS AND MATERIALS SCIENCE. AIP, 2011. http://dx.doi.org/10.1063/1.3663114.

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Hiramoto, Kazuhiko, Taichi Matsuoka et Katsuaki Sunakoda. « Semi-Active Control of Civil Structures With a Simultaneous Reduced-Order Modeling and a Tuning of the Control Law ». Dans ASME 2011 Pressure Vessels and Piping Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/pvp2011-57886.

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Various semi-active control methods have been proposed for vibration control of civil structures. In contrast to active vibration control systems, all semi-active control systems are essentially asymptotically stable because of the stability of the structural systems themselves (with structural damping) and the energy dissipating nature of the semi-active control law. In this study, by utilizing the above property on the stability of semi-active control systems, a reduced-order structural model and a semi-active control law are simultaneously obtained so that the performance of the resulting semi-active control system becomes good. Based on the above fact any semi-active control laws derived from some models stabilize all real-existing structural systems that have structural damping. It means that the difference of dynamic behaviors between the real structural system and the reduced-order mathematical model in the sense of the open-loop response is no longer an important issue. In other words, we do not have to consider the closed-loop stability, which is one of the most important constraints in active control, in the process of the reduced-order structural modeling and the semi-active control design. We can only focus on the control performance of the closed-loop system with the real structure with the (model-based) semi-active control law in obtaining the reduced-order model. The semi-active control law in the present study is based on the one step ahead prediction of the structural response. The Genetic Algorithm (GA) is adopted to obtain the reduced-order model and the semi-active control law based on the reduced order model.

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Zhao, Huyue, et F. Ehmann Kornel. « Single- and Multi-Stand Chatter Models in Tandem Rolling Mills ». Dans ASME 2008 International Manufacturing Science and Engineering Conference collocated with the 3rd JSME/ASME International Conference on Materials and Processing. ASMEDC, 2008. http://dx.doi.org/10.1115/msec_icmp2008-72530.

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Many different modes of chatter and their possible causes have been identified after years of research, yet no clear and definite theory of their mechanics has been established. One of the most important reasons for this can be attributed to the fact that only oversimplified models with a single input and a single output were historically used to formulate chatter in rolling. Such a situation has hindered a complete analysis of the underlying mechanisms. In this paper, a state-space representation of single- and multi-stand chatter models will be proposed in a rigorous and comprehensive mathematical form for stability analysis of the various chatter mechanisms. First, a dynamic model of the rolling process that utilizes homogeneous deformation theory will be established that includes the material strain-hardening and work roll flattening effects. By coupling this dynamic rolling process model with a structural model for mill stands, a single-stand chatter model in a state-space representation will be proposed. Based on the single-stand chatter model, a multi-stand chatter model will be formulated by incorporating the inter-stand tension variations and the time delay effect of the strip transportation. A simulation program will also be presented for the study of the dynamic rolling process in the time domain and for verifying the results from stability analysis.

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Dadfarnia, Mohsen, Nader Jalili et Darren M. Dawson. « An Investigation of Damping Mechanisms in Translational Euler-Bernoulli Beams Using a Lyapunov-Based Stability Approach ». Dans ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-41165.

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A translational cantilevered Euler-Bernoulli beam with tip mass dynamics at its free end is used to study the effect of several damping mechanisms on the stabilization of the beam displacement. Specifically, a Lyapunov-based controller utilizing a partial differential equation model of the translational beam is developed to exponentially stabilize the beam displacement while the beam support is regulated to a desired set-point position. Depending on the composition of the tip mass dynamics assumption (i.e. body-mass, point-mass, or massless), it is shown that proper combination of different damping mechanisms (i.e., strain-rate, structural, or viscous damping) guarantees exponential stability of the beam displacement. This novel Lyapunov-based approach, which is based on the energy dissipation mechanism in the beam, brings new dimensions to the stabilization problem of translational beams with tip mass dynamics. The stability analysis utilizes relatively simple mathematical tools to illustrate the exponential and asymptotic stability results. The numerical results are presented to show the effectiveness of the controller.

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Nurmi, Simo, Piroz Zamankhan, William Polashenski, Pertti Heikkila¨ et Ilkka Jokioinen. « Flotation and Aerodynamic Instability of Webs in a Dryer ». Dans ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56191.

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A mathematical model has been developed as a design optimization tool for the prediction of the aerodynamic behavior of a web in an industrial dryer. In particular the key modeling objective is to examine the propagation of stress waves within the web to determine its lateral motion and hence its stability. Numerical solutions were obtained through a coupling of computational fluid dynamics (CFD) calculations and structural dynamic simulations (SDS). The viscoelastic behavior of the web and the presence of turbulence were found to significantly affect the stability of the web.

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Roukema, Jochem C., et Yusuf Altintas. « Kinematic Model of Dynamic Drilling Process ». Dans ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-59340.

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A mathematical model of the torsional-axial chatter vibrations in drilling is presented. The model considers the exact kinematics of both rigid body, and coupled torsional and axial vibrations of the drill. The drill is modeled as a pretwisted beam that exhibits axial deflections due to torque and thrust loading. A mechanistic cutting force model is used to model the cutting torque and thrust as a function of feedrate, speed, radial depth of cut, and drill geometry. The drill rotates and feeds axially into the workpiece while the structural vibrations are excited by the cutting torque and thrust force. The exact location of the drill edge is predicted using the model, and the generated surface is digitized at discrete time intervals. The distribution of chip thickness, which is affected by both rigid body motion and structural vibrations, is evaluated by subtracting the presently generated surface from the previous one. The model considers nonlinearities in cutting coefficients, tool jumping out of cut and overlapping of multiple regeneration waves. The dynamic chip thickness obtained from the true kinematics model allows simultaneous prediction of force, torque, power and dimensional form errors left on the surface. The time domain simulation model allows prediction of stability lobes. The paper provides details of the mathematical model, supported by experimental results of both stable and unstable cuts.

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Corpus, William T., et William J. Endres. « An Analytical Model to Predict Chatter in Multi-Dimensional Periodically Time-Varying Machining Processes ». Dans ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-42488.

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An approach is presented to determine the stability limits for machining processes that exhibit periodic time variation and multi-dimensional structural dynamics. The approach leverages the solution for the single-dimensional case, which identified an added set of stability lobes in addition to those corresponding to the time-invariant case. The solution is developed for two-dimensional dynamics for both a damped system and an undamped system; it may be expanded to any order and extended to three-dimensional dynamics. The undamped solution provides a mathematical description of the stability lobe locations along the speed axis and asymptotes for the damped case. Numerical time-domain simulation is used to confirm the analytical solution. While the agreement is good even for a first-order analytical result, yet another extra stability lobe, not seen in the one-dimensional case, is now seen in the numerical simulation results. Some of its characteristics are noted; however, further study is needed to understand its source.

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Szabo, Barna A., et Ricardo L. Actis. « Mathematical Models of Fastened Structural Connections ». Dans General, Corporate & Regional Aviation Meeting & Exposition. 400 Commonwealth Drive, Warrendale, PA, United States : SAE International, 1999. http://dx.doi.org/10.4271/1999-01-1576.

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Rondon, Andres, et Sukru Guzey. « Evaluation of the Anchor-Bolt Chair Design Considering Localized Stresses in the Shell of Anchored Storage Tanks ». Dans ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-63712.

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Anchor bolt chairs are structural attachments used to control the overturning stability of aboveground storage tanks subjected to external and internal forces. Throughout this investigation three different design procedures were evaluated in order to determine the localized stresses occurring in the shell above the chairs due to wind load. The implemented methods are based on mathematical equations, stress linearization and stress extrapolation. Moreover, 3D finite element models were built to estimate the effect of tank height, diameter, shell thickness and anchor chair height. The results of the three methods are compared in terms of the localized stresses obtained from each one as well as in terms of the utilization ratio of the shell material.

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Fujita, Katsuhisa, et Akihide Gotou. « Dynamic Stability of an Elastic Beam Subjected to Follower Forces ». Dans ASME 2012 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/pvp2012-78278.

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The stability of nonconservative system of a beam is investigated when an elastic beam is subjected to follower forces. The mathematical formulations for a conservative system and a nonconservative system are established regarding to a uniform cantilever subjected to a concentrated force and a uniform distributed force axially. The displacement of a uniform cantilever is assumed to be obtained by superposing the modal functions which are normal modes in a vacuum, and is estimated by applying the Galerkin’s method. Changing the forces, the eigenvalue analysis is performed, and the root locus is calculated for the stability analysis. And, the relationship between forces and frequencies for the undamped system and the damped system of the uniform cantilever subjected to a concentrated force and a uniform distributed force is investigated. When the system is considered to be conservative, the divergence phenomenon is confirmed to appear first. On the other hand, when the system is considered to be nonconservative, the flutter phenomenon is confirmed to appear first although the critical force becomes high. And, by changing the structural damping, the destabilized effect due to the damping is confirmed when an elastic beam is subjected to follower forces.

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Rapports d'organisations sur le sujet "Structural stability Mathematical models"

Chen, Xiaojun, Hailin Sun et Roger J. Wets. Regularized Mathematical Programs with Stochastic Equilibrium Constraints : Estimating Structural Demand Models. Fort Belvoir, VA : Defense Technical Information Center, juillet 2013. http://dx.doi.org/10.21236/ada609521.

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Modlo, Yevhenii O., Serhiy O. Semerikov, Ruslan P. Shajda, Stanislav T. Tolmachev et Oksana M. Markova. Methods of using mobile Internet devices in the formation of the general professional component of bachelor in electromechanics competency in modeling of technical objects. [б. в.], juillet 2020. http://dx.doi.org/10.31812/123456789/3878.

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The article describes the components of methods of using mobile Internet devices in the formation of the general professional component of bachelor in electromechanics competency in modeling of technical objects: using various methods of representing models; solving professional problems using ICT; competence in electric machines and critical thinking. On the content of learning academic disciplines “Higher mathematics”, “Automatic control theory”, “Modeling of electromechanical systems”, “Electrical machines” features of use are disclosed for Scilab, SageCell, Google Sheets, Xcos on Cloud in the formation of the general professional component of bachelor in electromechanics competency in modeling of technical objects. It is concluded that it is advisable to use the following software for mobile Internet devices: a cloud-based spreadsheets as modeling tools (including neural networks), a visual modeling systems as a means of structural modeling of technical objects; a mobile computer mathematical system used at all stages of modeling; a mobile communication tools for organizing joint modeling activities.

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Riveros, Guillermo, Felipe Acosta, Reena Patel et Wayne Hodo. Computational mechanics of the paddlefish rostrum. Engineer Research and Development Center (U.S.), septembre 2021. http://dx.doi.org/10.21079/11681/41860.

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Purpose – The rostrum of a paddlefish provides hydrodynamic stability during feeding process in addition to detect the food using receptors that are randomly distributed in the rostrum. The exterior tissue of the rostrum covers the cartilage that surrounds the bones forming interlocking star shaped bones. Design/methodology/approach – The aim of this work is to assess the mechanical behavior of four finite element models varying the type of formulation as follows: linear-reduced integration, linear-full integration, quadratic-reduced integration and quadratic-full integration. Also presented is the load transfer mechanisms of the bone structure of the rostrum. Findings – Conclusions are based on comparison among the four models. There is no significant difference between integration orders for similar type of elements. Quadratic-reduced integration formulation resulted in lower structural stiffness compared with linear formulation as seen by higher displacements and stresses than using linearly formulated elements. It is concluded that second-order elements with reduced integration and can model accurately stress concentrations and distributions without over stiffening their general response. Originality/value – The use of advanced computational mechanics techniques to analyze the complex geometry and components of the paddlefish rostrum provides a viable avenue to gain fundamental understanding of the proper finite element formulation needed to successfully obtain the system behavior and hot spot locations.

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EFFECT OF RANDOM PRE-STRESSED FRICTION LOSS ON THE PERFORMANCE OF A SUSPEN-DOME STRUCTURE. The Hong Kong Institute of Steel Construction, mars 2022. http://dx.doi.org/10.18057/ijasc.2022.18.1.5.

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The key to the high-efficiency performance of the suspen-dome structure is to apply the pre-stressed design value to the structure accurately. However, engineering practice has found that the use of tensioning hoop cables to apply the pre-stress will produce noticeable pre-stressed friction loss (PFL), which significantly affects the safety performance of the structure. In this paper, based on a 1:10 scaled-down experiment model of a suspen-dome structure with rolling cable-strut joint installed, the random PFL (RPFL) effect of the suspen-dome on structure performance was analyzed through a probability statistics theory. First, aiming at the unequal tensioning force at both sides of the tensioned hoop cable during the tensioning process, a pre-stressed force calculation method is proposed that considers the unequal tensioning control force and RPFL at all cable–strut joints, and the reliability of this method is verified through a tension test. Then, based on the cable-joint tension test carried out in the early stage of the research group, a random mathematical model of the friction coefficient (FC) at the rolling cable–strut joint is established. And then, the cable force calculation method is used to establish the random finite element model, and independent and random changes in the FC at each rolling cable–strut joint can be considered. Subsequently, the Monte Carlo method is used to calculate the random mathematical characteristics of the mechanical performance parameters such as the member stress and joint deformation, and the obtained results are verified through a static loading experiment. In addition, to investigate the effect of random defects on structural stability, other random defects, such as the initial curvature and installation deviation, were continuously introduce based on the random finite element model. As such, we could obtain the law of the effect of multi-defect random variation coupling on the structure’s ultimate bearing capacity.

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STUDY OF IINTIAL IMPERFECTION OF CONCRETE-FILLED CIRCULAR STEEL TUBE COLUMNS FOR DIRECT ANALYSIS (ICASS’2020). The Hong Kong Institute of Steel Construction, août 2022. http://dx.doi.org/10.18057/icass2020.p.364.

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The initial imperfection and residual stress play important roles in the buckling resistance of both structural system and structural members. The latest Standard for Design of Steel Structures (GB50017-2017) firstly introduces the direct analysis method for the stability design of steel structures in China. The equivalent initial imperfections for steel members have been well specified in this code. However, as an important part of modern structures, there is limited research on the initial imperfections of steel-concrete composite members in relevant regulations in China. Therefore, it is urgent to study the equivalent initial imperfections of steel-concrete members for direct analysis. This paper collects extensive experimental data on concrete-filled circular steel tube columns (CFCSTC) for calibration of finite element models using software ABAQUS. The key factors affecting CFCSTC’s behaviors such as section dimensions, grades of steel and concrete, and width-to-thickness ratios have been taken into account. A comparative analysis for the CFCSTC with and without initial imperfections will be presented. From this study, the equivalent initial imperfection for CFCSTCs will be proposed for practical direct analysis of steel-concrete composite structures to achieve a safer and economical design without use of conventional effective length method.

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