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1
Luongo, A., i F. D'Annibale. "Double zero bifurcation of non-linear viscoelastic beams under conservative and non-conservative loads". International Journal of Non-Linear Mechanics 55 (październik 2013): 128–39. http://dx.doi.org/10.1016/j.ijnonlinmec.2013.05.007.
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Glabisz, W. "Stability of non-prismatic rods subjected to non-conservative loads". Computers & Structures 46, nr 3 (luty 1993): 479–86. http://dx.doi.org/10.1016/0045-7949(93)90217-2.
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Kim, Min-Geun, Bonyong Koo, You-Sung Han i Minho Yoon. "Asymmetric Design Sensitivity and Isogeometric Shape Optimization Subject to Deformation-Dependent Loads". Symmetry 13, nr 12 (9.12.2021): 2373. http://dx.doi.org/10.3390/sym13122373.
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We present a design sensitivity analysis and isogeometric shape optimization with path-dependent loads belonging to non-conservative loads under the assumption of elastic bodies. Path-dependent loads are sometimes expressed as the follower forces, and these loads have characteristics that depend not only on the design area of the structure but also on the deformation. When such a deformation-dependent load is considered, an asymmetric load stiffness matrix (tangential operator) in the response region appears. In this paper, the load stiffness matrix is derived by linearizing the non-linear non-conservative load, and the geometrical non-linear structure is optimally designed in the total Lagrangian formulation using the isogeometric framework. In particular, since the deformation-dependent load changes according to the change and displacement of the design area, the isogeometric analysis has a significant influence on the accuracy of the sensitivity analysis and optimization results. Through several numerical examples, the applicability and superiority of the isogeometric analysis method were verified in optimizing the shape of the problem subject to deformation-dependent loads.
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Adela Mejia-Nava, Rosa, Ismar Imamovic, Emina Hajdo i Adnan Ibrahimbegovic. "Nonlinear instability problem for geometrically exact beam under conservative and non-conservative loads". Engineering Structures 265 (sierpień 2022): 114446. http://dx.doi.org/10.1016/j.engstruct.2022.114446.
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Sasaki, M., i S. Chonan. "Vibration and stability of elasticity supported circular plates under conservative and non-conservative loads". Journal of Sound and Vibration 103, nr 1 (listopad 1985): 99–108. http://dx.doi.org/10.1016/0022-460x(85)90249-4.
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Guo, X. X. "Vibration Characteristics of the Non-Conservative Thermoelastic Coupling Plate". Applied Mechanics and Materials 66-68 (lipiec 2011): 551–56. http://dx.doi.org/10.4028/www.scientific.net/amm.66-68.551.
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The vibration characteristics of the thermoelastic coupling rectangular plate under the action of uniformly distributed tangential follower force are investigated. The coupled thermoelastic differential equation of the plate under the action of uniformly distributed tangential follower force was derived. Dimensionless complex frequencies of the thermoelastic coupling rectangular plate with one edge clamped and other three edges simply supported, two opposite edges simply supported and other two edges clamped were calculated by the differential quadrature method. The effects of the dimensionless thermoelastic coupling factor on the stability and critical load of the thin plate were analyzed. The results show that the flutter loads of the coupled modes increase with the increase of the dimensionless coupled thermoelastic factor and the aspect ratio.
7
Chonan, S., i M. Sasaki. "Vibration and stability of elastically supported multi-span beams under conservative and non-conservative loads". Journal of Sound and Vibration 99, nr 4 (kwiecień 1985): 545–56. http://dx.doi.org/10.1016/0022-460x(85)90539-5.
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Radin, V. P., V. P. Chirkov, E. V. Poznyak i O. V. Novikova. "Stability of a rod with the elastic joint exposed to distributed non-conservative load". Proceedings of Higher Educational Institutions. Маchine Building, nr 5 (758) (maj 2023): 3–13. http://dx.doi.org/10.18698/0536-1044-2023-5-3-13.
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Numerous features of non-conservative mechanical systems identified in studying their stability determine significant theoretical and practical interest to analyze various options of the calculation schemes. The paper considers stability of a rectilinear rod connected at one end to a joint and loaded with follower and potential loads uniformly distributed along the rod length. The joint was rigid with respect to rotation of the rod end. In order to apply the method of expanding solution to the perturbed motion equation into a series in terms of eigenmodes, the problem of determining the system eigenfrequencies and modes was solved. The cases of separate and combined action of the follower and potential loads were considered. A study was made on the influence of rigidity of the rod fastening and damping in the system on the loads critical values and on the position of the stability region boundaries on the loading parameters plane.
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Mpimpas, H., P. Anagnostopoulos i J. Ganoulis. "Uncertainty of model parameters in stream pollution using fuzzy arithmetic". Journal of Hydroinformatics 10, nr 3 (1.05.2008): 189–200. http://dx.doi.org/10.2166/hydro.2008.037.
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Fuzzy arithmetic is employed for the analysis of uncertainties in water-stream pollution, when the various model parameters involved are imprecise. The one-dimensional advection–dispersion equation, for both a conservative and a non-conservative substance, was solved analytically for point and Gaussian-hill input loads of pollution, considering the dispersion and decay coefficients involved as fuzzy numbers. The solution of the advection–dispersion equation was also conducted numerically for the same input loads with the finite-difference method, employing a Lagrangian–Eulerian scheme. The good agreement between analytical and numerical results presented in the form of fuzzy numbers confirms the reliability of the numerical scheme. The advection–dispersion equation of a non-conservative substance was then solved numerically for ten different water quality parameters, in order to study the water pollution in a water stream. The dispersion coefficient, the source terms and the input loads were expressed as fuzzy numbers, and the concentration of each quality parameter was obtained in fuzzy-number form. With fuzzy modeling, imprecise data can be represented and imprecise output produced, with minimal input data requirements and without the need of a large number of computations.
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Oliveira, D. C., R. B. Gomes i G. S. Melo. "Punching shear in reinforced concrete flat slabs with hole adjacent to the column and moment transfer". Revista IBRACON de Estruturas e Materiais 7, nr 3 (czerwiec 2014): 414–67. http://dx.doi.org/10.1590/s1983-41952014000300006.
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The structural behavior and the ultimate punching shear resistance of internal reinforced concrete flat slab-column connections, with one hole adjacent to the column, with or without flexural moment transfer of the slab to the column was investigated. Main variables were: the existence whether or not hole, flexural reinforcement layout and ratio, the direction and sense of the moment transferred and the eccentricity of the load (M (moment transferred to column) / V (shear)) ratio at the connection - 0,50 m or 0,25 m. Seven internal slab-column joining were tested and ultimate loads, cracking, deflections, concrete and reinforcement strains were analyzed. The existence of hole adjacent to the smaller column dimension, the hole dimension, flexural reinforcement rate and placing, the variation of relation Mu/Vu in function of the load, and, than, of eccentricity of the load, influenced the slabs behavior and rupture load. Test results were compared with the estimations from CEB-FIP/MC1990 [7], EC2/2004 [12], ACI-318:2011 [1] and NBR 6118:2007 [5]. ACI [1] and EC2 [12] presented most conservative estimates, although have presented some non conservative estimates. Brazilian NBR [5], even though being partly based in EC2 [12], presented smaller conservative estimates and more non conservative estimates. A modification on all codes is proposed for taking in account the moment caused by the eccentricity at the critical perimeter for slabs with holes.
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Shukla, Sunil, H. S. Deshmukh, Patil Vinaay i B. A. Thite A. "Evaluation of Gun Support Structure Using Equivalent Dynamic Approach in Non Linear FEA". Applied Mechanics and Materials 376 (sierpień 2013): 331–35. http://dx.doi.org/10.4028/www.scientific.net/amm.376.331.
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Robot Gun structure is an efficient way in which multiple welds can be done simultaneously. However mounting several weld guns on a single structure induces a variety of dynamic loads, especially during movement of the robot arm as it maneuvers to reach the weld locations.The primary idea employed in this paper, is to model those dynamic loads as equivalent G force loads in FEA. This approach will be on the conservative side, and will be saving time and subsequently cost efficient. The approach of the paper is towards creating a standard operating procedure (SOP) when it comes to analysis of such structures, with emphasis on deploying various technical aspects of FEA such as Non Linear Geometry, Multipoint Constraint Contact Algorithm, Multizone meshing .
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Paredes, Helmo K. Morales, Matheus Branco Arcadepani, Alexandre Candido Moreira, Flávio A. Serrão Gonçalves i Fernando Pinhabel Marafão. "Enlightening Load Modeling by Means of Power Factor Decompositions". Energies 16, nr 10 (15.05.2023): 4089. http://dx.doi.org/10.3390/en16104089.
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Considering the proliferation of power electronics applications and distributed energy resources, modern power grids are facing a significant increase in harmonic currents circulation and supply voltage deterioration, occasionally associated with small frequency variations. In such a context, the understanding of power phenomena in circuits with linear and non-linear loads under non-sinusoidal voltage conditions is nontrivial and still does not allow for an easy interpretation of harmonic sources, harmonic power flow or the identification of the parameters of a proper equivalent circuit. The main challenge is to develop modern theoretical approaches for load characterization, modeling, and parameter estimation so that new techniques can be formulated to provide adequate guiding for the analysis, compensation, revenue metering, accountability and other applications of power systems. Thus, based on the Conservative Power Theory (CPT) and further decomposition of its apparent power and power factor definitions, this paper proposes a novel methodology for estimating equivalent parameters and for proposing proper equivalent circuits capable of representing/modeling the main characteristics of single-phase generic loads (black boxes) and the related power phenomena in terms of passive dipoles (linear loads) or of harmonic voltage/current sources and their intrinsic transimpedances/transadmittances (non-linear loads). Simulation and experimental results were depicted to support and validate the proposed approach, showing that it might be a powerful modeling technique to represent generic loads in a modern power grid scenario, while being used for complex applications such as reactive power compensation or accountability in circuits with nonlinear loads and distorted voltages.
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Moriarty, Patrick J., William E. Holley i Sandy Butterfield. "Effect of Turbulence Variation on Extreme Loads Prediction for Wind Turbines". Journal of Solar Energy Engineering 124, nr 4 (1.11.2002): 387–95. http://dx.doi.org/10.1115/1.1510137.
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The effect of varying turbulence levels on long-term loads extrapolation techniques was examined using a joint probability density function of both mean wind speed and turbulence level for loads calculations. The turbulence level has a dramatic effect on the statistics of moment maxima extracted from aeroelastic simulations. Maxima from simulations at lower turbulence levels are more deterministic and become dominated by the stochastic component as turbulence level increases. Short-term probability distributions were calculated using four different moment-based fitting methods. Several hundred of these distributions were used to calculate a long-term probability function. From the long-term probability, 1- and 50-yr extreme loads were estimated. As an alternative, using a normal conditional distribution of turbulence level produced a long-term load comparable to that of a log-normal conditional distribution and may be more straightforward to implement. A parametric model of the moments was also used to estimate the extreme loads. The parametric model required less data, but predicted significantly lower loads than the empirical model. An input extrapolation technique was also examined. Extrapolating the turbulence level prior to input into the aeroelastic code simplifies the loads extrapolation procedure but, in this case, produces loads lower than most empirical models and may be non-conservative in general.
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Cai, Fu Hai, Xin Wang i Fu Ling Zhao. "A New Fatigue Life Calculation Method Based on Non-Linear Cumulative Damage Theory". Applied Mechanics and Materials 423-426 (wrzesień 2013): 2116–22. http://dx.doi.org/10.4028/www.scientific.net/amm.423-426.2116.
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Operating characteristics of small and medium tonnage lattice boom crane which withstand fatigue loads was analyzed in this paper. It showed that the lattice boom crane utilization level is in the overlap zone of low cycle fatigue and high cycle fatigue. There may be some plastic deformation in the structure. So the total damage calculated by the Palmgren-Miner rule had a large scatter. Typical operating conditions was analyzed that K-type welded joints of the boom is under axial load and in-plane bending loads. Several critical areas of K-type welded joints were determined by ANSYS finite element calculation software where the stress amplitude was larger on the single side of the lattice boom. A new stress spectrum acquisition method based on the “measured+statistics+compare+simulation” integrated strategy of crane K-type welded joints was proposed. Based on a simplified Huffman non-linear cumulative damage theory, fatigue life of crane K-type welded Joints were calculated based on the strain parameters. They were compared with Palmgren-Miner rule and together with fracture mechanics method. Results showed that although they were all conservative compared with test results, the new method can be applied easily in for engineering applications because it only need amplitude constant amplitude fatigue strain-life data.
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Qingzhen, Lu, Yin Yuanchao, Yang Zhixun, Chen Jinlong, Yan Jun i Yue Qianjin. "Fatigue Life Prediction of Umbilicals Considering Non-Linear Stress". Polish Maritime Research 24, s2 (28.08.2017): 154–63. http://dx.doi.org/10.1515/pomr-2017-0078.
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Abstract The fatigue problem induced by wave loads and floater movements of dynamic umbilicals in deepwater is studied. The prediction method of the fatigue life is investigated by considering no-linear local stress due to contact and friction between components of the umbilical. A case study of a dynamic umbilical for 1500 meters depth in South China Sea was presented. The results showed that the more accurate result of the fatigue life was calculated by considering non-linear local stress. The fatigue life by considering local stress with the no-slip assumption was conservative. An obviously longer fatigue life was obtained by considering local stress with the full-slip assumption.
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Agapov, Vladimir P., i Kurban R. Aidemirov. "Designing of the blades of aircraft propellers by the finite element method, taking into account the strength of structure". RUDN Journal of Engineering Researches 22, nr 1 (27.08.2021): 65–71. http://dx.doi.org/10.22363/2312-8143-2021-22-1-65-71.
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The blades of contemporary turboprop engines have a complex spatial configuration. They can be classified as shells. Methods for the shells calculation are well known. A number of computer programs have been created on their basis. However, these programs do not take into account the peculiarities associated with the mutual influence of deformations of the blade and the aerodynamic and inertial loads acting on it. The aim of this work is to develop a method of finite element calculation of aircraft propeller blades taking into account aeroelastic effects and to create a computer program on its basis that is available to a wide range of designers and engineers. The finite element method is used in a geometrically nonlinear formulation. As the initial one, the equilibrium equation is used, which includes a complete nonlinear stiffness matrix and takes into account both conservative and non-conservative loads. The blade of one of the serial propellers was calculated. The effect of deformations on the magnitude of the aerodynamic load and, as a result, on the stresses in the design sections was found and analyzed. The proposed technique and the program compiled on its basis can be used in the design of aircraft propeller blades.
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Altman, Wolf, i Luiz Bevilacqua. "Nonconservative Components of Follower Forces in the Classical Shell Theory". Applied Mechanics Reviews 42, nr 11S (1.11.1989): S13—S19. http://dx.doi.org/10.1115/1.3152383.
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An analysis of follower forces acting on shell structures is presented. Attention is focussed on the expressions of such forces as functions of the generalized displacements. Specific expressions for the follower forces are obtained, according to the order of magnitude of the strains and angles of rotation. For small strains the follower forces allow a decomposition into conservative and non-conservative components. This leads to the equations of dynamic stability of shell problems subjected to follower loads. The dynamic counterparts of Donnell-Mushtari-Vlasov stability equations are presented, by either retaining or omitting the prebuckling rotations.
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van Kuik, G. A. M., D. Micallef, I. Herraez, A. H. van Zuijlen i D. Ragni. "The role of conservative forces in rotor aerodynamics". Journal of Fluid Mechanics 750 (9.06.2014): 284–315. http://dx.doi.org/10.1017/jfm.2014.256.
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AbstractThe theory to predict the performance and loads on rotors (propellers, screws, windmills) has a history of more than a century. Apart from modern computational fluid dynamics and vortex panel models taking the true blade geometry into account, most other models proceed from an infinitely thin actuator disc or line. These models assume an externally defined force field distributed at the disc or line, representing the loads on the real rotor. Given this force field, the flow is solved by momentum balances or by the equations of motion. The use of external force fields was discussed in textbooks of the first decades of the 20th century, but has received little attention since then. This paper investigates the higher-order effect of adding thickness to the actuator disc or changing the actuator line to a blade with cross-sectional dimensions. For the generation of a Rankine vortex by a force field acting on an actuator disc with thickness, an exact solution has been found in which not only the thrust and torque determine the flow, but also a radial force. This force is conservative, in contrast to the other force components. For rotor blades, a conservative normal and radial force acting on the chordwise bound vorticity is present. This explains the experimentally observed inboard motion of the tip vortex of model wind turbine rotors before the wake induction field drives it outboard. Simulations by computational fluid mechanics and a vortex panel code reproduce the inboard motion, but an actuator line analysis, in which the chordwise vorticity is absent, does not. The conservative load is only $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}1\mbox{--}2\, \%$ of the thrust on the entire blade but ${\approx }10\, \%$ of the thrust at the tip ($r/R>0.9$). Conservative forces at the disc and rotor blade vanish for vanishing disc thickness or blade cross-section, so play no role in any of the infinitely thin actuator disc or line methods. However, if higher-order effects of non-zero dimensions are to be modelled, the conservative force field has to be included.
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Fleury, Mateus Porto, Lucas Deroide do Nascimento, Clever Aparecido Valentin, Jefferson Lins da Silva i Marta Pereira da Luz. "Creep Behaviour of Recycled Poly(ethylene) Terephthalate Non-Woven Geotextiles". Polymers 13, nr 5 (28.02.2021): 752. http://dx.doi.org/10.3390/polym13050752.
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At the beginning of this century, due to well-established Brazilian recycling processes, geosynthetics’ manufacturers started to use recycled poly(ethylene) terephthalate (PET) yarns/filaments (from PET bottles) in geotextile production. Despite the fact that recycled products cannot act as reinforcement functions, geosynthetics are constantly under sustained tensile load and experiences evolutions of the axial strain (creep behaviour). Thus, this study aims to assess the influence of the structure of (needle-punched) non-woven geotextiles manufactured using recycled PET yarns on their creep behaviour. Two geotextiles with different fibre/filament production processes were investigated (short-staple fibres—GTXnwS—and continuous filaments—GTXnwC). Unconfined in-isolated conventional and accelerated (using the stepped isothermal method) creep tests were performed at 5%, 10%, 20%, 40% and 60% of geotextiles’ ultimate tensile strength. The geotextiles investigated provided similar creep behaviour to geotextiles manufactured with virgin PET material. The standard deviation of the axial strain tends to increase as the load level applied increase. The structure of the GTXnwS harms its tensile –strain behaviour, promoting axial deformation under sustained loads, at least 50% higher than GTXnwC for the same load level applied. The influence of the load level and geotextile structure in the initial axial strain is pointed out. Long-term predictions based on creep tests performed using the stepped isothermal method have proven to be conservative and they must be restricted for quality control of the investigated geotextiles.
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Dietrich, M., K. Kędzior, A. Wittek i T. Zagrajek. "Non-Linear Finite Element Analysis of Formation and Treatment of Intervertebral Disc Herniae". Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 206, nr 4 (grudzień 1992): 225–31. http://dx.doi.org/10.1243/pime_proc_1992_206_294_02.
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A biomechanical model of the spine motion segment L2/L3 consisting of the truncated vertebrae, endplates, intervertebral disc and pieces of anterior and posterior longitudinal ligaments has been used for a computer simulation study. A non-linear finite element analysis has shown that small loads compressing the spine, not greater than those occurring in everyday life, cause loss of stability of an intervertebral disc, resulting in lateral dislocation of its nucleus pulposus. This could be a potential cause of discopathy. The model indicates that conservative therapy of herniated disc by the traction method may result in retraction of hernia by about 40 per cent.
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Ciavarella, M., G. Macina i G. P. Demelio. "On stress concentration on nearly flat contacts". Journal of Strain Analysis for Engineering Design 37, nr 6 (1.08.2002): 493–501. http://dx.doi.org/10.1243/030932402320950116.
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Fretting fatigue can severely damage components subjected to oscillatory tangential loads, leading to a dramatic reduction in fatigue life and causing catastrophic ruptures. A conservative approach that can be used when considering the effect of stress concentration induced by fretting is to ensure that the peak stress is smaller than the fatigue limit of the material. However, this depends on details of the geometry as well as loading conditions. In the present work, the contact problem of a flat rounded punch in contact with a half-plane is considered, where a dovetail joint contact geometry is approximated and the classical Hertzian contact is retrieved in the limit. Developing the analytical results given by Ciavarella, Hills and Monno, an approximate Hertzian equivalent solution using Cattaneo superposition is obtained, leading to a simple formula to estimate the maximum tangential stress as a function of the load parameter Q/(f P) and geometric parameter a/b. The accuracy of the formula is checked numerically. The proposed formula gives a maximum error as low as 4 per cent in the case of zero bulk loads. For non-zero bulk loads an analytical solution is possible for the Hertzian case for moderate bulk. This leads to a second general formula containing the three dependencies (geometry, tangential load and bulk stress), which also gives a very good approximation for rounded flat and larger bulk loads, the error being generally well below 10 per cent.
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Manuel, Lance, Paul S. Veers i Steven R. Winterstein. "Parametric Models for Estimating Wind Turbine Fatigue Loads for Design". Journal of Solar Energy Engineering 123, nr 4 (1.06.2001): 346–55. http://dx.doi.org/10.1115/1.1409555.
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International standards for wind turbine certification depend on finding long-term fatigue load distributions that are conservative with respect to the state of knowledge for a given system. Statistical models of loads for fatigue application are described and demonstrated using flap and edge blade-bending data from a commercial turbine in complex terrain. Distributions of rainflow-counted range data for each ten-minute segment are characterized by parameters related to their first three statistical moments (mean, coefficient of variation, and skewness). Quadratic Weibull distribution functions based on these three moments are shown to match the measured load distributions if the non-damaging low-amplitude ranges are first eliminated. The moments are mapped to the wind conditions with a two-dimensional regression over ten-minute average wind speed and turbulence intensity. With this mapping, the short-term distribution of ranges is known for any combination of average wind speed and turbulence intensity. The long-term distribution of ranges is determined by integrating over the annual distribution of input conditions. First, we study long-term loads derived by integration over wind speed distribution alone, using standard-specified turbulence levels. Next, we perform this integration over both wind speed and turbulence distribution for the example site. Results are compared between standard-driven and site-driven load estimates. Finally, using statistics based on the regression of the statistical moments over the input conditions, the uncertainty (due to the limited data set) in the long-term load distribution is represented by 95% confidence bounds on predicted loads.
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Aida, Tadayoshi. "Basic Equations of Dynamic Elastic Stability for Thin-Walled Structural Members Subjected to Follower Loads and Their Application to Non-Conservative Torque Problems". Transactions of the Canadian Society for Mechanical Engineering 9, nr 2 (czerwiec 1985): 75–83. http://dx.doi.org/10.1139/tcsme-1985-0011.
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The basic equations and the boundary conditions, in which the effect of an initial torsional moment Mz0 is included, and needed for the analysis of the dynamic elastic stability of thin-walled structural members subjected to follower loads are derived by introducing the concept of initial stress and using the principle of virtual work. The stability problems of columns with a channel section subjected to a non-conservative torque are investigated in terms of numerical examples.
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Niu, Congmin, i Huajiang Ouyang. "Nonlinear Dynamic Analysis of Lifting Mechanism of an Electric Overhead Crane during Emergency Braking". Applied Sciences 10, nr 23 (24.11.2020): 8334. http://dx.doi.org/10.3390/app10238334.
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Mechanical brakes are essential for electric cranes when emergency braking occurs. This paper presents, for the first-time, a dynamic response analysis of emergency braking events of electrical cranes that has modelled crane components as flexible and rigid bodies. Based on the Hamilton principle, a nonlinear and non-smooth dynamic model is derived from a modified Lagrangian function and the virtual work of non-conservative forces. The dynamic responses of a 32-ton overhead travelling crane during the emergency braking process of its lifting mechanism with two service brakes determined by simulating realistic operations. The numerical results show that the loads acting on components of the crane during the braking process depend on the braking capacity and the action time of the mechanical brakes, as well as the magnitude and the initial position of the payload. When a dual-brake scheme of the lifting mechanism is adopted, the maximum load of the high-speed links and the maximum thermal power of the mechanical brake appear in the emergency braking process when one of the two brakes fails to work. In addition, it is found to be a false belief that the lower the initial speed, the lower the maximum loads acting on components of cranes become during the braking process.
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Radin, V. P., V. P. Chirkov, A. V. Shchugorev i V. N. Shchugorev. "OFF-CENTER COMPRESSION OF THE ROD BY POTENTIAL AND NONCONSERVATIVE FORCES". Spravochnik. Inzhenernyi zhurnal, nr 275 (2020): 9–16. http://dx.doi.org/10.14489/hb.2020.02.pp.009-016.
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The paper studies the stability of the rectilinear form of equilibrium with the construction of the boundaries of the stability region for a rod with uniformly distributed mass. The stability of the cantilever rod is considered for the off-center application of potential and tracking forces. In case of non-conservative loads, when it is possible to lose the stability of the equilibrium position, a dynamic method of research is used. it is shown that the influence of the eccentric application of loads does not affect the location of the flutter boundary, but in contrast to the classical problem, the rod oscillations do not occur in the vicinity of the rectilinear form of equilibrium, but in the vicinity of the curved shape determined by the eccentricity value.
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Zhao, Yong Xiang, Bing Yang i Ming Fei Feng. "Determination of the Probabilistic Fatigue S-N Curves Including Super-Long Life Regime for a Railway Axle Steel". Advanced Materials Research 44-46 (czerwiec 2008): 57–64. http://dx.doi.org/10.4028/www.scientific.net/amr.44-46.57.
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The structures of railway vehicles are required to service in super-long life regime. Determination of the probabilistic S-N curves including the regime should be a basic work to realize the real fatigue life prediction and reliability assessment. Based on the test results of Chinese railway LZ50 axle carbon steel, a statistical extrapolating method is proposed to determine the curves by applying the conventional test data in mid-long life regime. Some phenomena, i.e. the response of “fatigue limit”, a great of heat affecting using the high frequency ultrasonic fatigue test system, and the non-conservative test results using the conventional frequency tiny multi-specimen test system (machine C), are firstly mentioned in the existent super-long life researches. The too much conservative offers are also noted by the determinations of existent codes. To address the variable amplitude loads in production, the present method extrapolates continuously the curves from the mid- to super-long life regimes under the statistical controls of conventional fatigue limits. The practice for the present material indicates that the curves can well reflect the scattered data not only in mid-long life regime but also in super-long life regime. The non-conservative test results using machine C are also safely included by the curves.
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Zuluaga-Ramírez, Pablo, Malte Frövel, Álvaro Arconada, Tomás Belenguer i Félix Salazar. "Evaluation of the Fatigue Linear Damage Accumulation Rule for Aeronautical CFRP Using Artificial Neural Networks". Advanced Materials Research 1016 (sierpień 2014): 8–13. http://dx.doi.org/10.4028/www.scientific.net/amr.1016.8.
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New optimized aerospace structures use composite materials for critical components and subsystems which make essential the knowledge of their fatigue properties. In the present work, the conventional methodology based on linear damage accumulation rules, applied to determine the fatigue life of structures subjected to spectral loads was evaluated for an aeronautical Carbon Fiber Reinforced Epoxy composite material. A test program has been performed to obtain the classical S-N curves at different stress ratios. Constant life diagrams, CLDs, where determined by means of Artificial Neural Networks due to the absence of consistent models for composites. A series of coupons have been tested until failure with a modified version of the standard FALSTAFF load sequence and were compared to the theoretical damage index calculated based on the conventional linear damage accumulation rule. The obtained results show non-conservative predictions.
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Datta, P. K., i P. J. Deolasi. "Dynamic Instability Characteristics of Plates Subjected to Partially Distributed Follower Edge Loading with Damping". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 210, nr 5 (wrzesień 1996): 445–52. http://dx.doi.org/10.1243/pime_proc_1996_210_218_02.
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The dynamic instability characteristics of rectangular plates with at least one free edge and subjected to non-conservative follower loading at the free edge has been studied by using the finite element formulation. The loading is distributed partially at the centre of the free edge. The modal transformation is applied to the resulting equilibrium equation for subsequent analysis. Structural damping is introduced into the system in terms of equivalent viscous damping. The effects of load bandwidth, plate aspect ratio, direction control parameter, damping, etc., on the stability behaviour of the plates are studied. The results show that the load bandwidth has a significant effect on the dynamic instability characteristics of the plates. The results also show that, under follower loading, the system is susceptible to instability due to flutter alone or due to both flutter and divergence, depending upon the system parameters. Structural damping may significantly reduce the critical flutter loads of the plates.
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Istiono, Heri, i Azhar Yusuf Ramadhan. "Analisis Pengaruh P-Delta Effect Terhadap Perbedaan Ketinggian Struktur Gedung Tahan Gempa (Studi Kasus : Non-Highrise Building)". Rekayasa Sipil 14, nr 3 (25.10.2020): 218–26. http://dx.doi.org/10.21776/ub.rekayasasipil.2020.014.03.8.
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The need for earthquake resistant buildings in Indonesia is something that needs to be considered. Considering that Indonesia is an earthquake prone area. A building structure must be designed to be able to withstand lateral loads such as earthquakes within the limits set by the code/standards. For conservative reasons analysis of the P-Delta Effect needs to be considered because the building development ratio will always increase every time. according to SNI 1726-2019 the P-Delta effect is only required for the design of tall buildings. In this case, the P-Delta effect will be calculated in the modeling of non-high-rise buildings and get the results that P-Delta Effect increased story forces: moment of the building under 10%.
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Radin, V. P., V. P. Chirkov, A. V. Shchugorev i V. N. Shchugorev. "Methods for Determinning Critical Values of Nonconservative Loads in Problems of Stability of Mechanical Systems". Proceedings of Higher Educational Institutions. Маchine Building, nr 10 (715) (październik 2019): 3–13. http://dx.doi.org/10.18698/0536-1044-2019-10-3-13.
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Methods for determining critical values of nonconservative loads in stability problems of mechanical systems with distributed parameters are considered in this work. Based on a dynamic approach to stability problems, the method of direct integration of the linearized equation of perturbed motion is proposed, and the problem of determining critical loads is reduced to the problem of minimizing a complex function of several variables. As a second method, the method of decomposition of the solution of the equation of perturbed motion in the forms of natural oscillations is presented. The fundamentals of the application of the finite element method to the problems of stability under the action of non-conservative loads are also described. The methods are illustrated on classical problems: the stability of the cantilever rod under the action of potential and tracking forces and the stability of the pipeline section with flowing liquid. The accuracy and convergence of the latter two methods are analyzed depending on the number of members in the series and the number of finite elements.
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Cantagallo, Cristina, Marco Terrenzi, Enrico Spacone i Guido Camata. "Effects of Multi-Directional Seismic Input on Non-Linear Static Analysis of Existing Reinforced Concrete Structures". Buildings 13, nr 7 (28.06.2023): 1656. http://dx.doi.org/10.3390/buildings13071656.
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Recent studies have shown the importance of including the seismic input directionality in nonlinear analyses for an accurate prediction of the structural demand on frame structures. This paper proposes a new method that includes the multi-directionality of the input seismic forces in Nonlinear Static Analyses (NSAs). Conventionally, the pushover (PO) analyses apply monotonically increasing lateral loads in two directions that typically correspond with the building X and Y directions, that in the case of a rectangular plan are parallel to the building sides. Since in general the direction of the seismic input is a priori unknown, the effects of applying the PO load patterns along varying angles are studied in this paper. Two non-code-conforming reinforced concrete buildings are used as a case study. They have identical structural design but the first one is doubly symmetric while the second one has a significant plan asymmetry due to the translation of the center of mass. PO loads are applied to both structures at angles between 0° and 360° with 15° increments. The results of the NSAs are compared with those of multi-directional NHAs applied at the same angles. The structural demands show that the multi-directional NSAs are more conservative than the conventional NSAs, especially at the corners of the asymmetric- plan building where they can yield significantly higher demands. The base shear capacities in the X and Y directions decrease for intermediate angles due to the interaction between the responses in the X and Y directions that can be captured thanks to the columns’ fiber section discretization. On average the results of the multi-directional NSAs are closer to those of the NHAs, even though they are generally lower.
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An, Qi, Hua Zhao, Peihai Li i Maohai Fu. "Fatigue strength analysis of bogie frames under random loads". Advances in Mechanical Engineering 11, nr 9 (wrzesień 2019): 168781401987801. http://dx.doi.org/10.1177/1687814019878018.
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In this study, a method for analyzing the fatigue strength of a bogie frame under a random load was proposed. Based on the geometric features, a welded joint coordinate system was established to compute the stress components of each node in this coordinate system. With the influence of small amplitude cycles included, based on the corrected S–N curve and a method for calculating the equivalent constant amplitude stress, the node and comprehensive degree of utilization were calculated based on the anti-fatigue design grade of welded joints to evaluate the fatigue strength of a structure under a given lifespan. The FKM and International Institute of Welding methods were used to evaluate the fatigue strength of typical welded joints of a bogie frame. The characteristics of the node degree of utilization under different analytical methods were compared, and the results showed that when the time histories of the three stress components of the nodes had significant non-proportional features, the FKM method obtained conservative results. When the time histories of the three stress components of the nodes were synchronized, the criterion value specified by the International Institute of Welding method was the main factor affecting the distribution characteristics of the node degree of utilization. The analysis based on the International Institute of Welding method can effectively balance the lightweight design and reliability of the structure.
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Amiri, Amir Parviz Khosravi. "Non-linear study of base shear and moment of composite columns in MRFs". International Journal of Engineering & Technology 4, nr 1 (7.02.2015): 205. http://dx.doi.org/10.14419/ijet.v4i1.4144.
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The main objective of this study is evaluating the seismic behavior of composite columns in MRFs subject to dynamic loads.The design Codes of composite structures contain different views in some cases and therefore conservative provisions, because of lack of enough information about the behavior of these structures. The base shear and moment of structures in non-linear state can be considered as criteria for the potential of a lateral-force-resisting system to dissipate the seismic energy.Lower values of non-linear seismic base reactions indicate better efficacy of the system. In this study the performance of the MRFs with composite columns has been evaluated using 8-story structural models, considering the base reactions obtained from the non-linear analysis. Analytical modeling has been performed based on the AISC Code. The results show good performance of composite sections under the seismic loads. Also, a comparison between two types of composite sections, the full and half-embedded steel sections in concrete, has been made.
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Pecník, Miroslav, Viktor Borzovič i Kamil Laco. "Non-Linear FEM Analysis of Integral Bridges Transition Area". Solid State Phenomena 259 (maj 2017): 152–57. http://dx.doi.org/10.4028/www.scientific.net/ssp.259.152.
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The transition area of bridges is non-homogeneous solid, which consists of soil embankment, transition slab and roadway layers. These transition area elements consist of various materials with different properties. Besides the imposed loads, behavior of these areas is significantly affected by uneven settlement between the bridge abutment and soil embankment. In case of integral bridges horizontal movements of a bridge caused mostly by temperature and ongoing rheological phenomena in concrete have to be taken into account. This leads to abutment deformation in combination with time dependent soil consolidation it results in varying earth pressure over the bridges lifetime together with cyclic horizontal movements of the pavement resulting in its cracks and excessive deformations. In this paper, comparison of different approaches to finite element analysis of transition areas is presented. First analysis was performed using area elements to represent the bridge structure, and volume elements to represent embankment, while second analysis was performed in more conservative way using spring based method proposed by Křížek[3], as representation of the surrounding soil. Results obtained via both methods are compared with each other as well as with data obtained from experimental measurment of a transition area conducted in Switzerland [1].
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Kumar, L. Ravi, P. K. Datta i D. L. Prabhakara. "Dynamic instability characteristics of doubly curved panels subjected to partially distributed follower edge loading with damping". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 218, nr 1 (1.01.2004): 67–81. http://dx.doi.org/10.1243/095440604322786956.
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The vibration and dynamic instability characteristics of doubly curved panels subjected to partially distributed non-conservative follower load are studied using finite element analysis. The first-order shear deformation theory is used to model the doubly curved panels, considering the effects of shear deformation and rotary inertia. The theory used is the extension of dynamic, shear deformable theory according to Sander's first approximation for doubly curved shells, which can be reduced to Love's and Donnell's theories by means of tracers. The modal transformation technique is applied to the resulting equilibrium equation for subsequent analysis. Structural damping is introduced into the system in terms of equivalent viscous damping. The effects of load bandwidth, boundary condition, load direction control parameter and damping are considered for the stability behaviour of the panels. The results show that the load bandwidth has a significant effect on the dynamic instability characteristics of the panels. The analysis also shows that, under follower loading, the system is susceptible to instability due to flutter alone or due to both flutter and divergence, depending upon the system parameters. Structural damping significantly affects the critical flutter loads of the panels.
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Ekenta, O. E. "Catchment Modelling Of Non – Point Source Pollution Accretion For Rivers". European Scientific Journal, ESJ 12, nr 2 (29.01.2016): 309. http://dx.doi.org/10.19044/esj.2016.v12n2p309.
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Catchment process simulation models are designed to model the interaction of hydrological, geochemical and ecological processes and the effects of change. TOMCAT, a catchment scale model was applied in modeling the transport of determinands from non-point (diffuse) sources to Mimram river, a tributary of the river Thames. The magnitude and timing of the processes taking place is stochastic with the model representing as accurately as possible the systematic and random variability of various model inputs and their inter-relationships. The results indicate that the BOD, NH4N and Un-ionised NH3 loads which enter the rivers from non-point sources increased by 0.55mg/l, 0.024mg/l and 0.001mg/l respectively. These values are relatively small. The Dissolved Oxygen concentration along the reach increased by 2.5 mg/l indicating substantial re-aeration along the reach. The accretion value for the conservative determinand Chloride was 3.75mg/l. Non-point source pollutants accretion to the Mimram is influenced by agricultural and silvicultural practices in the catchment. The results of the investigation indicate that the model could be adopted by environmental pollution control agencies as a management tool for intervention in the area of pollution abatement for catchments.
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Scott, Samuel, Peter Greaves, Terence Macquart i Alberto Pirrera. "Comparison of blade optimisation strategies for the IEA 15MW reference turbine". Journal of Physics: Conference Series 2265, nr 3 (1.05.2022): 032029. http://dx.doi.org/10.1088/1742-6596/2265/3/032029.
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Abstract Reference wind turbine models are crucial for enabling the research community to advance technology and meet the challenges associated with upscaling. The IEA 15 MW is one such reference model, designed using NREL’s WISDEM tool, which enables researchers to perform system-level analysis and optimisation. However, the authors have found the blade to be structurally infeasible when subject to aero-servo-elastic simulations and finite-element (FE) analyses. Given the shortcomings, this work aims to develop an updated blade model for the 15 MW turbine platform using the design tool Aeroelastic Turbine Optimisation Methods (ATOM). Two optimisation processes, with a comprehensive suite of feasibility constraints, are applied: 1) a frozen-loads mass minimisation with fixed planform, and 2) an aero-servo-structural levelised cost of energy (LCoE) minimisation. Results show the frozen-loads optimised design results in a 0.93% increase in LCoE due to the mass penalty of attaining feasibility. In contrast, the aero-structural optimised design results in a 2.29% reduction in LCoE due to mass reductions and increased energy capture—highlighting the benefits of an integrated design process. FE shell analysis of the optimised blades indicates the strength predictions in ATOM are accurate and the main load-bearing spar caps are optimally utilised. Whilst an improvement on the baseline, buckling load factors do not satisfy the target values, indicating the lower fidelity checks in ATOM are non-conservative. The WindIO yaml files for these optimised designs are freely available online.
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Dawood, Shilan Nawzad, Abdulsalam Rasheed Al-Zahawi i Laith Abed Sabri. "Mechanical and Thermal Stress Behavior of a Conservative Proposed Veneer Preparation Design for Restoring Misaligned Anterior Teeth: A 3D Finite Element Analysis". Applied Sciences 10, nr 17 (22.08.2020): 5814. http://dx.doi.org/10.3390/app10175814.
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The objective of this study was to evaluate the biomechanical and thermal behavior of a proposed preparation design as a conservative treatment option that aims to preserve both gingival and tooth health structures through a comparative finite element analysis with non-preparation and conventional designs. 3D solid models of laminate veneers with different preparation designs were obtained using cone-beam computed tomography (CBCT) scanning of the maxillary incisor. A 100-Newton load was applied with angulations of 60° and 125° to the longitudinal axis of the tooth to determine the stresses during mastication. In addition, transient thermal analysis was performed to compare the temperature and thermal distribution of the restored tooth models when subjected to thermal loads of 5 °C and 55 °C. Teeth prepared with the proposed design showed lower stress distributions and a repairable failure mode, followed by the non-preparation design, while teeth prepared with the conventional design showed the highest stress concentrations. Furthermore, cold thermal loading yielded larger thermal stress distributions than hot thermal loading, independent of the preparation type, and the effect of temperature changes were within the critical limit near the pulp and dentin regions. Thus, the preparation design geometry affects the long-term success of laminate restoration, and the proposed design yields more uniform and appropriate stress distributions than the other techniques.
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Sree, Phani C. R., i Daniel Kujawski. "A Deviatoric Stress-Strain Function for Fatigue Life Analysis". Advanced Materials Research 891-892 (marzec 2014): 797–802. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.797.
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The Smith-Watson-Topper (SWT) parameter was originally suggested and is still widely used to account for mean stress effects in fatigue life analysis. It is well recognized however, that the SWT parameter might be non-conservative for cyclic loads that involve relatively large compressive mean stresses. Such large compressive mean stresses can develop in notches after overloads. An energy interpretation of the SWT parameter is presented first. Based on analogy with the Neuber’s rule a new deviatoric formulation of the SWTD parameter is proposed. It is found that for positive mean stresses and moderate negative mean stresses the original SWT parameter and the proposed deviatoric SWTD parameter yield similar results. At large compressive mean stresses and non-proportional biaxial fatigue, the deviatoric SWTD parameter demonstrates a fairly good correlation to test data while the original SWT parameter results in wide scatter.
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Galletly, G. D., i K. Pemsing. "Interactive Buckling Tests on Cylindrical Shells Subjected to Axial Compression and External Pressure—A Comparison of Experiment, Theory and Various Codes". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 199, nr 4 (październik 1985): 259–80. http://dx.doi.org/10.1243/pime_proc_1985_199_123_02.
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The buckling of welded steel cylindrical shells under the combined action of external pressure and axial compressive loads is of considerable interest to the offshore oil and nuclear industries. However, test results on this subject are scarce and some design rules which have been proposed recently have not been validated experimentally, especially in the plastic buckling region. In order to check these rules, and suggest others, interactive buckling tests were conducted at Liverpool University on cylindrical shells having R/t ≍ 100. One series of tests consisted of 19 machined and stress-relieved steel models having L/R ratios of 0.33, 0.74 and 1.45. The results obtained on these near-perfect machined models were compared with theoretical predictions of the behaviour of perfect cylindrical shells and the agreement between the two was good The other series consisted of 21 welded steel models and had geometric ratios which were similar to the machined ones. The linear interaction equation Sp + Sx = 1 was used to predict the failure loads of these welded steel models and the predictions were safe in all cases. However, for some combined loading cases the linear equation was rather conservative and, in consequence, some non-linear interaction equations were investigated. These seem promising for design purposes. Irrespective of whether a linear or a non-linear equation is chosen for design, more tests will be needed to establish the scatter bands of the interactive buckling curves for various values of R/t. Some tests were also carried out on (a) the effect of the loading path on the failure loads and (b) models with localized dents. Other topics discussed in the paper are: the effects of residual stresses and initial geometric imperfections, the general procedure adopted by Codes to predict buckling loads and some discrepancies between the predictions of various Codes.
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Yongbing, FENG. "Seismic Performance Analysis of Continuous Rigid Frame Bridges in Expressway under Non-linear Interactions of Soil-Piles". MATEC Web of Conferences 175 (2018): 04037. http://dx.doi.org/10.1051/matecconf/201817504037.
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Taking the three-span pre-stressed concrete continuous rigid frame bridge as an engineering example, MIDAS Civil was utilized to establish a spatial finite element model and the interaction between pile foundation and the soil was simulated by equivalent soil spring. In addition to analyzing shearing force, bending moment and stress of the primary beam's characteristic section under different loads, a response spectrum method and time history analysis were adopted to conduct seismic response analysis respectively. In this case, performance of the bridge could be comprehensively evaluated. Relevant analysis results indicate that internal force of the large-span pre-stressed concrete continuous rigid frame bridge is mainly induced by gravity and pre-stress of the structure; section stresses of the primary beam satisfy the corresponding specification and structural safety can be achieved in a state of operation. Moreover, computed results obtained by the response spectrum method is more conservative than those of the time history analysis. In terms of continuous rigid frame bridge, different seismic directions should be taken into consideration during structural seismic analysis at different construction stages.
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Souza, Larissa R., Ruben B. Godoy, Matheus A. de Souza, Luigi G. Junior i Moacyr A. G. de Brito. "Sampling Rate Impact on Electrical Power Measurements Based on Conservative Power Theory". Energies 14, nr 19 (2.10.2021): 6285. http://dx.doi.org/10.3390/en14196285.
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This article presents a study of the sampling rate effect on electrical power measurements whose definitions are based on the Conservative Power Theory (CPT). The definitions of active power and reactive power of the CPT were applied in the MATLAB® software by varying the sampling rate and using a digital power meter as a reference. The measurements were performed in scenarios with linear and non-linear loads. Due to the usage of an integral in the CPT calculus, an error was verified associated with the reactive power being inversely proportional to the sampling rate. From the present study, it is possible to conclude that depending on the sample rate, the errors associated with the reactive power measurements are unacceptable and make the CPT implementation unfeasible. The results also presented effective information about the minimal sampling rate needed to make these errors neglected and to assist in choosing suitable microprocessors for the digital implementation of the CPT. It is worth mentioning that this paper was limited to assess how accurate the measurements of active and reactive powers were and important to highlight that the CPT has the additional contribution of dealing with distortion currents and consequently new portions of powers. For the latter, the influence of sampling rate may be crucial and new lines of investigation are motivated.
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Reem Sabouni. "Sustainability Considerations for Underground Concrete Manholes". Electronic Journal of Structural Engineering 13, nr 2 (1.06.2013): 50–55. http://dx.doi.org/10.56748/ejse.131722.
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Sewer systems enclose one of the harshest environments on concrete materials. These systems if made of concrete are usually accessed for maintenance and inspection by precast concrete manholes. The present design practices of these shafts components in Canada are generally conservative which results in heavily reinforced bases. If verified by full scale testing the code allows the use of alternative manhole design. To produce a more sustainable precast concrete manhole the steel reinforcement has to be minimized or even eliminated altogether if possible. In the course of introducing a more sustainable manhole a full scale load testing of non-reinforced base precast concrete manhole in a controlled laboratory environment was performed under critical configurations of the Ontario truck. This was followed by an extensive numerical investigation on the proposed manhole. The results showed that the proposed sustainable manhole can withstands applied loads without cracks in the shaft or its base. After verifying the structural validity of the proposed manhole design the sustainability of this design was evaluated. Also, a life cycle assessment scheme for precast concrete manholes was proposed. And the sustainability efforts in Precast Concrete manholes were summarizes
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VACARU, RALUCA-PAULA, SILVIA PER, IOANA-ANDREEA STANCIU, ANETA MUNTEANU, DANIELA MIRICESCU, ALEXANDRA TOTAN, MIHAELA TĂNASE i ANDREEA CRISTIANA DIDILESCU. "Clinical and microbiological features of carious dentin in immature permanent molars". Romanian Biotechnological Letters 26, nr 1 (1.01.2021): 2340–46. http://dx.doi.org/10.25083/rbl/26.1/2340.2346.
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The present study aimed to assess the dentin lesion activity in non-superficial carious lesions affecting vital immature permanent molars and to investigate possible associations between microbiological status, clinical dentin alterations, and salivary cortisol levels. Study sample consisted of a total number of 22 immature permanent molars of 13 children. After clinical estimation of lesion activity, a fine sample of deep dentin layer was removed and inoculated on bacteria tests. Salivary cortisol was assessed using an ELISA method. Most molars were diagnosed as actively carious progressing. There was a gradual increase in the bacterial counts, with higher lactobacilli (p=0.001) and mutans streptococci (p=0.045) loads in deep carious lesions, without any salivary cortisol level association. The findings of the present study discriminate between different clinical characteristics of carious lesions, supporting a conservative cavity preparation approach.
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Ellobody, Ehab. "Finite element modelling and design of composite bridges with profiled steel sheeting". Advances in Structural Engineering 20, nr 9 (1.12.2016): 1406–30. http://dx.doi.org/10.1177/1369433216678865.
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This article discusses the non-linear analysis and design of highway composite bridges with profiled steel sheeting. A three-dimensional finite element model has been developed for the composite bridges, which accounted for the bridge geometries, material non-linearities of the bridge components, bridge boundary conditions, shear connection, interactions among bridge components and bridge bracing systems. The simply supported composite bridge has a span of 48 m, a width of 13 m and a depth of 2.3 m. The bridge components were designed following the European code for steel–concrete composite bridges. The live load acting on the bridge was load model 1, which represents the static and dynamic effects of vertical loading due to normal road traffic as specified in the European code. The finite element model of the composite bridge was developed depending on additional finite element models, developed by the author, and validated against tests reported in the literature on full-scale composite bridges and composite bridge components. The tests had different geometries, different boundary conditions, different loading conditions and different failure modes. Failure loads, load–mid-span deflection relationships, load–end slip relationships, failure modes, stress contours of the composite bridge as well as of the modelled tests were predicted from the finite element analysis and compared well against test results. The comparison with test results has shown that the finite element models can be effectively used to provide more accurate analyses and better understanding for the behaviour and design of composite bridges with profiled steel sheeting. A parametric study was conducted on the composite bridge highlighting the effects of the change in structural steel strength and concrete strength on the behaviour and design of the composite bridge. This study has shown that the design rules specified in the European code are accurate and conservative for the design of highway steel–concrete composite bridges.
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Shoji, Hiroaki, Atsushi Teramoto, Yuzuru Sakakibara, Tomoaki Kamiya, Kota Watanabe i Toshihiko Yamashita. "Stability of the ankle joint in anatomical or non-anatomical anterior talofibular ligament repair". Foot & Ankle Orthopaedics 3, nr 3 (1.07.2018): 2473011418S0044. http://dx.doi.org/10.1177/2473011418s00446.
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Category: Ankle Introduction/Purpose: Chronic ankle instability (CAI) often needs surgical treatment if conservative treatment is ineffective. Recently, arthroscopic surgeries have become widely used to treat CAI. Although it is crucial to accurately ascertain the anterior talofibular ligament (ATFL) attachment site under arthroscopy, previous study showed that it might not be feasible to thoroughly observe the ATFL attachment site, and repair or reconstruction position were often unintentionally carried out proximal to the ATFL attachment site at the fibula as a result. Currently, there are few reports about stability of the ankle joint by different repair position of ATFL. The aim of this study was to evaluate the stability of the ankle joint by different repair position of ATFL. Methods: Six fresh-frozen human cadaveric ankles with the mean age of 83.5 ± 7.3 years were used. The ankles were tested using a six-degrees of freedom robotic system. The following ankle states were evaluated: intact, ATFL transection, ATFL anatomical repair, and ATFL non-anatomical repair. ATFL was transected at fibular attachment. Anatomical repair was performed at the center of original ATFL attachment of the fibula. Non-anatomical repair was set 8mm proximal from anatomical ATFL attachment of the fibula. At each state, laxity of anterior translation under 60 N load, inversion under 1.7 Nm load, and internal rotation under 1.7 Nm load were evaluated. Each test was performed at 30 degrees plantarflexion (PF), 15 degrees PF, 0 degree, and 15 degrees dorsiflexion (DF). The one-way repeated measures analysis of variance (ANOVA) with post hoc pairwise comparisons with Dunnett’s test was adopted. A P value of 0.05 was chosen as the level of significance. Results: Anterior translation under 60 N load was significantly increased in transection condition at 30 degrees PF compared with the intact condition (P=0.005). Anatomical repair and Non-anatomical repair did not show significant differences. Inversion under 1.7 Nm load was significantly increased in transection condition at 30 and 15 degrees PF compared with the intact condition (P=0.004, =0.049). Anatomical repair and Non-anatomical repair did not show significant differences. Internal rotation under 1.7 Nm load was significantly increased in transection condition at 30, 15 degrees PF and 0 degree compared with the intact condition (P<0.001, <0.001, and <0.001). Although anatomical repair did not show significant differences, non-anatomical repair showed significant increase at 30 and 15 degrees compared with the intact condition (P=0.006, =0.026). (Fig. 1). Conclusion: Anatomical repair did not show significant difference in all three loads with the intact condition. In non-anatomical repair, anterior translation and inversion did not show significant difference, but internal rotation significantly increased at 30 and 15 degrees PF compared with the intact condition. Compared with anatomical repair, non-anatomical repair might become more vertical ligament running because its attachment site of the fibula was more proximal. This difference might affect stability of the ankle joint. Anatomical repair of the ATFL might be essential to obtain the stability of the ankle joint like the intact condition.
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Nunes, Riterson, i Wanderson Maia. "ANÁLISE NUMÉRICA DE CANTONEIRAS ENRIJECIDAS ASSIMÉTRICAS DE AÇO FORMADAS A FRIO SUBMETIDAS À COMPRESSÃO CENTRADA". COLLOQUIUM EXACTARUM 13, nr 4 (20.12.2021): 54–68. http://dx.doi.org/10.5747/ce.2021.v13.n4.e376.
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The present work brings a numerical, non-linear physical and geometric analysis using the Finite Element Method, of asymmetrical stiff angles, using the Ansys software. The simulations employed two magnitudes of initial imperfections, and aimed to find the critical buckling loads and failure modes, observing local, global instabilities and the interaction between both. The results obtained were compared with experimental tests, performed by Young and Chen (2008), and with the values proposed by the brazilian standard ABNT NBR 14762: 2010, using the Direct Resistance Method. The procedure adopted for the simulations proved to be quite efficient, producing very interesting results compared to the experimental ones, showing the reliability of this method for the analysis of cold-formed steel asymmetrical angles. The initial imperfections adopted demonstrated that, for the same profile, it was not the same magnitude that produced the best results, emphasizing the importance of your choice. The calculation procedure of ABNT NBR 14762: 2010, using the Direct Resistance Method, proved to be coherent for bars up to 1000 mm, but very conservative for those of greater length, with the increase of slenderness.
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Dutkiewicz, Maciej, Andrii Velychkovych, Ivan Shatskyi i Vasyl Shopa. "Efficient Model of the Interaction of Elastomeric Filler with an Open Shell and a Chrome-Plated Shaft in a Dry Friction Damper". Materials 15, nr 13 (3.07.2022): 4671. http://dx.doi.org/10.3390/ma15134671.
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The results of a study of the contact interaction of an open shell and a chrome-plated shaft with elastomeric filler installed coaxially are presented. The considered contact system is a model of the original design of the shell damper of dry friction. The design feature is the following: the bearing link of the damper is a thin-walled cylindrical shell with a cut along the generatrix; the working body of the damper is elastomeric filler; a hollow chrome-plated shaft centers the damper elements and allows it to be used in technological processes with the presence of aggressive and abrasive-containing media. The mechanical-mathematical modeling of the behavior of the presented damper under the conditions of operational loads has been carried out. The idea of identifying the properties of a cut isotropic shell, which bends under the conditions of a nonaxisymmetric contact load, and a strongly orthotropic continuous shell is applied. As a result, dependences were obtained to determine the rigidity and the maximum allowable load of the damper. The effect of the coefficient of friction of the contact pairs elastomer-shell and elastomer-shaft on the damper performance properties has been studied. A technique for the quasi-static analysis of structural damping in non-mobile, non-conservative shell systems with deforming filler has been developed. The hysteresis loops of the damper under a nonmonotonic load are constructed, the dependence of the amount of dissipated energy on the cycle asymmetry coefficient is found. An analysis of the results obtained showed that the use of open shells in friction shock absorbers can significantly reduce their rigidity compared to solid shells and thereby reduce the resonant frequencies of the dynamic system. This circumstance makes such vibration isolators particularly attractive for use in superresonance vibrators as working modules of drilling shock absorbers and elastic hangers of sucker rods in oil and gas production.
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Anjum, Waqas, Abdul Rashid Husain, Junaidi Abdul Aziz, Syed Muhammad Fasih ur Rehman, Muhammad Paend Bakht i Hasan Alqaraghuli. "A Robust Dynamic Control Strategy for Standalone PV System under Variable Load and Environmental Conditions". Sustainability 14, nr 8 (12.04.2022): 4601. http://dx.doi.org/10.3390/su14084601.
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Dual-stage standalone photovoltaic (PV) systems suffer from stability, reliability issues, and their efficiency to deliver maximum power is greatly affected by changing environmental conditions. A hybrid back-stepping control (BSC) is a good candidate for maximum power point tracking (MPPT) however, there are eminent steady-state oscillations in the PV output due to BSC’s recursive nature. The issue can be addressed by proposing a hybrid integral back-stepping control (IBSC) algorithm where the proposed integral action significantly reduces the steady-state oscillations in the PV array output under varying temperature and solar irradiance level. Simultaneously, at the AC stage, the primary challenge is to reduce both the steady-state tracking error and total harmonic distortion (THD) at the output of VSI, resulting from the load parameter variations. Although the conventional sliding mode control (SMC) is robust to parameter variations, however, it is discontinuous in nature and inherit over-conservative gain design. In order to address this issue, a dynamic disturbance rejection strategy based on super twisting control (STC) has been proposed where a higher order sliding mode observer is designed to estimate the effect of load disturbances as a lumped parameter which is then rejected by the newly designed control law to achieve the desired VSI tracking performance. The proposed control strategy has been validated via MATLAB Simulink where the system reaches the steady-state in 0.005 s and gives a DC–DC conversion efficiency of 99.85% at the peak solar irradiation level. The AC stage steady-state error is minimized to 0 V whereas, THD is limited to 0.07% and 0.11% for linear and non-linear loads, respectively.
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Cicero, Sergio, Juan Fuentes, Isabela Procopio, Virginia Madrazo i Pablo González. "Critical Distance Default Values for Structural Steels and a Simple Formulation to Estimate the Apparent Fracture Toughness in U-Notched Conditions". Metals 8, nr 11 (24.10.2018): 871. http://dx.doi.org/10.3390/met8110871.
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The structural integrity assessment of components containing notch-type defects has been the subject of extensive research in the last few decades. The assumption that notches behave as cracks is generally too conservative, making it necessary to develop assessment methodologies that consider the specific nature of notches, providing accurate safe predictions of failure loads or defect sizes. Among the different theories or models that have been developed to address this issue the Theory of Critical Distances (TCD) is one of the most widely applied and extended. This theory is actually a group of methodologies that have in common the use of the material toughness and a length parameter that depends on the material (the critical distance; L). This length parameter requires calibration in those situations where there is a certain non-linear behavior on the micro or the macro scale. This calibration process constitutes the main practical barrier for an extensive use of the TCD in structural steels. The main purpose of this paper is to provide, through a set of proposed default values, a simple methodology to accurately estimate both the critical distance of structural steels and the corresponding apparent fracture toughness predictions derived from the TCD.