Articoli di riviste: "Nonlinear impact loads"

1

Masoum, M. A. S., E. F. Fuchs e D. J. Roesler. "Impact of nonlinear loads on anisotropic transformers". IEEE Transactions on Power Delivery 6, n. 4 (1991): 1781–88. http://dx.doi.org/10.1109/61.97721.

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Schellin, Thomas E., e Ould el Moctar. "Numerical Prediction of Impact-Related Wave Loads on Ships". Journal of Offshore Mechanics and Arctic Engineering 129, n. 1 (8 novembre 2006): 39–47. http://dx.doi.org/10.1115/1.2429695.

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We present a numerical procedure to predict impact-related wave-induced (slamming) loads on ships. The procedure was applied to predict slamming loads on two ships that feature a flared bow with a pronounced bulb, hull shapes typical of modern offshore supply vessels. The procedure used a chain of seakeeping codes. First, a linear Green function panel code computed ship responses in unit amplitude regular waves. Ship speed, wave frequency, and wave heading were systematically varied to cover all possible combinations likely to cause slamming. Regular design waves were selected on the basis of maximum magnitudes of relative normal velocity between ship critical areas and wave, averaged over the critical areas. Second, a nonlinear strip theory seakeeping code determined ship motions under design wave conditions, thereby accounting for the nonlinear pressure distribution up to the wave contour and the frequency dependence of the radiation forces (memory effect). Third, these nonlinearly computed ship motions constituted part of the input for a Reynolds-averaged Navier–Stokes equations code that was used to obtain slamming loads. Favorable comparison with available model test data validated the procedure and demonstrated its capability to predict slamming loads suitable for design of ship structures.

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Ghorbani, M. Jawad, e Hossein Mokhtari. "Impact of Harmonics on Power Quality and Losses in Power Distribution Systems". International Journal of Electrical and Computer Engineering (IJECE) 5, n. 1 (1 febbraio 2015): 166. http://dx.doi.org/10.11591/ijece.v5i1.pp166-174.

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This paper investigates the harmonic distortion and losses in power distribution systems due to the dramatic increase of nonlinear loads. This paper tries to determine the amount of the harmonics generated by nonlinear loads in residential, commercial and office loads in distribution feeders and estimates the energy losses due to these harmonics. Norton equivalent modeling technique has been used to model the nonlinear loads. The presented harmonic Norton equivalent models of the end user appliances are accurately obtained based on the experimental data taken from the laboratory measurements. A 20 kV/400V distribution feeder is simulated to analyze the impact of nonlinear loads on feeder harmonic distortion level and losses. The model follows a “bottom-up” approach, starting from end users appliances Norton equivalent model and then modeling residential, commercial and office loads. Two new indices are introduced by the authors to quantize the effect of each nonlinear appliance on the power quality of a distribution feeder and loads are ranked based on these new defined indices. The simulation results show that harmonic distortion in distribution systems can increase power losses up to 20%.

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Arsava, K. Sarp, e Yeesock Kim. "Modeling of Magnetorheological Dampers under Various Impact Loads". Shock and Vibration 2015 (2015): 1–20. http://dx.doi.org/10.1155/2015/905186.

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Magnetorheological (MR) damper has received great attention from structural control engineering because it provides the best features of both passive and active control systems. However, many studies on the application of MR dampers to large civil structures have tended to center on the modeling of MR dampers under seismic excitations, while, to date, there has been minimal research regarding the MR damper model under impact loads. Hence, this paper investigates nonlinear models of MR dampers under a variety of impact loads and control signals. Two fuzzy models are proposed for modeling the nonlinear impact behavior of MR dampers. They are compared with mechanical models, the Bingham and Bouc-Wen models. Experimental studies are performed to generate sets of input and output data for training, validating, and testing the models: the deflection, acceleration, velocity, and current signals. It is demonstrated that the proposed fuzzy models are effective in predicting the complex nonlinear behavior of the MR damper subjected to a variety of impact loads and control signals. The proposed fuzzy model resulted in an accuracy of 99% to predict the impact forces of the MR damper.

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Lin, Jie, Chao Deng e Jia Chu Xu. "Nonlinear Dynamic Buckling of FGM Shallow Conical Shells under Triangular Pulse Impact Loads". Advanced Materials Research 460 (febbraio 2012): 119–26. http://dx.doi.org/10.4028/www.scientific.net/amr.460.119.

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In this paper, nonlinear dynamic buckling of FGM shallow conical shells under the action of triangular pulse impact loads are investigated. The nonlinear dynamic governing equation of symmetrically FGM shallow conical shells is built. Using Galerkin method, the nonlinear dynamic governing equation is solved, and the nonlinear dynamic response equation of symmetrically FGM shallow conical shells is obtained. The Runge-Kutta method is introduced to numerically solve the nonlinear dynamic response equation and the impact response curve is achieved. Budiansky-Roth motion criterion expressed by the displacement of the peak of the shell is employed to determine the critical impact buckling load. The influences of geometric parameters and gradient constants on impact buckling are discussed as well.

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Du, Chang Long, Yu Liu e Jian Ping Li. "Numerical Analysis on Impact Load of Elasto-Plastic Spherical Impact". Advanced Materials Research 189-193 (febbraio 2011): 1840–43. http://dx.doi.org/10.4028/www.scientific.net/amr.189-193.1840.

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The spherical impact is a common phenomenon in mechanical engineering. The elasto-plastic impact is more complicate than the elastic impact. The elasto-plastic impact loads are investigated for the different contact stiffness and the different impact velocity by the nonlinear finite element method. The accuracy and reliability of the finite elements model are verified by comparing the numerical results of the elastic impact with the Hertz results. The elasto-plastic impact simulation shows that the impact loads have a negative exponential relation with the contact stiffness as well as a linear relation with the impact velocity. The contact time decrease with the increase of the contact stiffness and the impact velocity. The comparison between the influence of the contact stiffness and the impact velocity indicates that the impact velocity has a significant influence on the impact load and the contact stiffness has a big influence on the contact time.

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Manito, Allan, Ubiratan Bezerra, Maria Tostes, Edson Matos, Carminda Carvalho e Thiago Soares. "Evaluating Harmonic Distortions on Grid Voltages Due to Multiple Nonlinear Loads Using Artificial Neural Networks". Energies 11, n. 12 (26 novembre 2018): 3303. http://dx.doi.org/10.3390/en11123303.

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This paper presents a procedure to estimate the impacts on voltage harmonic distortion at a point of interest due to multiple nonlinear loads in the electrical network. Despite artificial neural networks (ANN) being a widely used technique for the solution of a large amount and variety of issues in electric power systems, including harmonics modeling, its utilization to establish relationships among the harmonic voltage at a point of interest in the electric grid and the corresponding harmonic currents generated by nonlinear loads was not found in the literature, thus this innovative procedure is considered in this article. A simultaneous measurement campaign must be carried out in all nonlinear loads and at the point of interest for data acquisition to train and test the ANN model. A sensitivity analysis is proposed to establish the percent contribution of load currents on the observed voltage distortion, which constitutes an original definition presented in this paper. Initially, alternative transient program (ATP) simulations are used to calculate harmonic voltages at points of interest in an industrial test system due to nonlinear loads whose harmonic currents are known. The resulting impacts on voltage harmonic distortions obtained by the ATP simulations are taken as reference values to compare with those obtained by using the proposed procedure based on ANN. By comparing ATP results with those obtained by the ANN model, it is observed that the proposed methodology is able to classify correctly the impact degree of nonlinear load currents on voltage harmonic distortions at points of interest, as proposed in this paper.

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Sarp Arsava, Kemal, Yeesock Kim, Tahar El-Korchi e Hyo Seon Park. "Nonlinear system identification of smart structures under high impact loads". Smart Materials and Structures 22, n. 5 (3 aprile 2013): 055008. http://dx.doi.org/10.1088/0964-1726/22/5/055008.

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Finn, Patrick J., Robert F. Beck, Armin W. Troesch e Yung Sup Shin. "Nonlinear Impact Loading in an Oblique Seaway". Journal of Offshore Mechanics and Arctic Engineering 125, n. 3 (11 luglio 2003): 190–97. http://dx.doi.org/10.1115/1.1578499.

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There is an increasing interest in developing direct calculation methods and procedures for determining extreme wave loads on ship girders (e.g. ISSC, 2000 [1]). Ships experiencing bottom and bow flare slamming have heightened the need for computational tools suitable to accurately predict motion and structural responses. The associated nonlinear impact problem is complicated by the complex free surface and body boundary conditions. This paper examines a “blended” linear–nonlinear method by which extreme loads due to bottom impact and flare slamming can be determined. Using a high-speed container ship as an example, comparisons of motions, shear and bending moments, and pressures are made in head and oblique bow-quartering waves. The time-domain computer program used in the comparison is based upon partially nonlinear models. The program, NSHIPMO, is an blended strip theory method using “impact” stations over the forward part of the ship and partially nonlinear stations over the rest. Body exact hydrostatics and Froude-Krylov excitation are used over the entire hull. The impact theory of Troesch and Kang [2] is employed to estimate the sectional nonlinear impact forces acting upon the specified nonlinear sections, while the linear theory of Salvesen et al. (STF) [3] is used to blend the remainder of the hydrodynamic forces, that is the radiation and diffraction components. Results from the simulation are presented with discussions of accuracy and time of computation. Several issues associated with the blended nonlinear time-domain simulation are presented, including modeling issues related to directional yaw-sway control and a vertical plane dynamic instability in long waves that has not previously been recognized.

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Piatkowski, Tomasz, Janusz Sempruch e Tomasz Tomaszewski. "DYNAMICS OF A SORTING PROCESS WITH A STREAM OF DISCRETE IMPACT LOADS". Transactions of the Canadian Society for Mechanical Engineering 38, n. 1 (marzo 2014): 139–54. http://dx.doi.org/10.1139/tcsme-2014-0009.

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The sorting process applied to a stream of unit loads (cubiform objects, parcels) transported on conveyors is investigated. The sorting process is performed by means of an active fence (flexible arm) that makes a 1dof rotary motion. The manipulated loads are treated as bodies with nonlinear elastic-damping properties described by modified nonlinear Kelvin model. The equations of motion of the flexible fence, and those of the interacting object, are derived using the finite element method. The assessment of influence of constructional and operating parameters of the fence on the course of the sorting process and dynamic forces exerted on the loads handled is studied.

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11

Tedesco, J. W., P. B. McGill e W. G. McDougal. "Response of Dolos Concrete Armor Units to Impact Loads". Journal of Offshore Mechanics and Arctic Engineering 113, n. 4 (1 novembre 1991): 286–91. http://dx.doi.org/10.1115/1.2919932.

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A finite element analysis is conducted to determine the critical impact velocities for concrete dolos. The model formulation includes deformations at the contact surface and nonlinear material properties. Two dolos orientations are considered: vertical fluke seaward and horizontal fluke seaward. In both cases, the larger units fail at lower angular impact velocities. It is also shown that doubling the concrete strength increases the impact resistance by approximately 40 percent.

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Sarp Arsava, K., Yunyoung Nam e Yeesock Kim. "Nonlinear system identification of smart reinforced concrete structures under impact loads". Journal of Vibration and Control 22, n. 16 (8 agosto 2016): 3576–600. http://dx.doi.org/10.1177/1077546314563966.

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13

P. Monteiro, Flávia, Suzane A. Monteiro, Maria E. Tostes e Ubiratan H. Bezerra. "Using True RMS Current Measurements to Estimate Harmonic Impacts of Multiple Nonlinear Loads in Electric Distribution Grids". Energies 12, n. 21 (30 ottobre 2019): 4132. http://dx.doi.org/10.3390/en12214132.

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Currently, for analyzing harmonic impacts on voltage at a point of interest, due to multiple nonlinear loads, the literature recommends carrying out simultaneous and synchronized measurement campaigns in all suspicious points with the use of high cost energy quality analyzers that are usually not available at the customers’ facilities and very often also not at the electric utilities. To overcome this drawback this paper proposes a method of assessing the harmonic impact due to multiple nonlinear loads on the total voltage harmonic distortion using only the load current true RMS values which are already available in all customers’ installations. The proposed methodology is based on Regression Tree technique using the Permutation Importance indicator which is validated in two case studies using two different electrical systems. The first case study is to ratify the use of Permutation Importance to measure the impact factor of each nonlinear load in a controlled scenario, the IEEE-13 bus test system, using ATP simulation (Alternative Transient Program). The second is to apply the methodology to a real system, an Advanced Measurement Infrastructure System (AMI) implanted on a campus of a Brazilian University, using low cost meters with only true RMS current measurements. The results achieved demonstrated the feasibility of applying the proposed methodology in real electric systems without the need for additional investments in high-cost energy quality analyzers.

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14

Long, Xiaohong, Ahmed Turgun, Rong Yue, Yongtao Ma e Hui Luo. "Influence Factors Analysis of RC Beams under Falling Weight Impact Based on HJC Model". Shock and Vibration 2018 (21 ottobre 2018): 1–16. http://dx.doi.org/10.1155/2018/4731863.

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Impact loads may cause serious or even fatal damage to the structure (component), in most existing specifications in China, and there are no special terms that take impact load into consideration. So, the response analysis of the structure (component) under impact loads is very important. In this paper, the sensitivity analysis was conducted for the 22 parameters of the Holmquist–Johnson concrete (HJC) constitutive model of concrete, and the sensitive parameters of the HJC model are identified with A, B, G, Pl, μl, and fc respectively. LS-DYNA nonlinear transient finite element analysis code was used for this paper. Based on the validation of finite element modeling and choosing midspan deflection of RC beams and impact loads as response indices, some influencing factors on RC beams under falling weight impact were investigated, such as the mass and speed of falling weight, impact position, the strength of concrete and rebar, longitudinal reinforcement ratio, and the span of the beam.

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Zhang, Suo Huai, e Hai Ming Wang. "Research on Impacting Loads between Metro Vehicles". Applied Mechanics and Materials 628 (settembre 2014): 199–204. http://dx.doi.org/10.4028/www.scientific.net/amm.628.199.

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In order to research impacting characteristics of the trainset, the impacting model and governing equations are established, in which, the stiffness and nonlinear damping of a buffer, friction force between rail and the vehicles wheels is considered. The stiffness and nonlinear damping of the buffers used in the model is verified by testing results. By numerical simulation, it is found that when moving trainset impacts standing trainset, because the impacting force, stroke of the buffers located in impacting interface is the maximum, the buffers capacity must be large enough to avoid rigid impact. The impacting force, comfort and safety of moving vehicles or standing vehicles far from the impacting interface with the same distance are nearly same. The farer the vehicle is from impacting interface, the little the vehicles damage is, and the safer the passages are. When vehicles are more, the maximum impacting force is constant approximately; when vehicles are fewer, the maximum impacting force descends obviously. If vehicles are fewer, after impacting, it takes short time for trainset to stop.

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MIMURA, K., T. UMEDA, M. YU, Y. UCHIDA e H. YAKA. "EFFECTS OF IMPACT VELOCITY AND SLENDERNESS RATIO ON DYNAMIC BUCKLING LOAD FOR LONG COLUMNS". International Journal of Modern Physics B 22, n. 31n32 (30 dicembre 2008): 5596–602. http://dx.doi.org/10.1142/s0217979208050875.

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In this research, the buckling behavior of long columns under dynamic load was investigated both experimentally and numerically, and an effective buckling criterion for dynamic load was derived from the results in terms of the impact velocity and the slenderness ratio. In the experiments, a free fall drop-weight type impact testing machine was employed. The dynamic buckling loads were measured by the load sensing block, and the displacements were measured by a high speed magnetic-resistance device. In the numerical analyses, dynamic FEM code 'MSC-Dytran' was used to simulate the typical experimental results, and the validity and the accuracy of the simulations were checked. The dynamic buckling loads at various impact velocities were then systematically investigated. From both experimental and simulated results, it was found that the dynamic to static buckling load ratios can be successfully described as a square function of the slenderness ratio of the columns, while they can be also described by a power law of the applied impact velocity.

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Heskes, Peter J. M., Johanna M. A. Myrzik e Wil L. Kling. "Impact of distribution system's nonlinear loads with constant power on grid voltage". European Transactions on Electrical Power 21, n. 1 (12 luglio 2010): 698–711. http://dx.doi.org/10.1002/etep.470.

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18

Zhang, Junhua, Xiufang Zhu, Xiaodong Yang e Wei Zhang. "Transient nonlinear responses of an auxetic honeycomb sandwich plate under impact loads". International Journal of Impact Engineering 134 (dicembre 2019): 103383. http://dx.doi.org/10.1016/j.ijimpeng.2019.103383.

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19

Xiao, Sen, Yanchao Qie, Wu Chen, Jikuang Yang e Jeff R. Crandall. "Investigation of chest biomechanical response by variation of restraint loads in frontal impact". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 234, n. 5 (14 ottobre 2019): 1377–88. http://dx.doi.org/10.1177/0954407019881067.

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The seatbelt restraint load is one of the primary sources of occupant chest injury. Thus, studying the different biomechanical responses of chest by varying the seatbelt loads will result in a significant improvement in seatbelt protection performance. Based on the high-biofidelity mechanical dummy model, a sled-dummy test was conducted to investigate the differences in chest injury outcomes caused by the variation of seatbelt load paths or load processes. The chest kinematics and kinetics are compared to determine the influence of load factors on these biomechanical outcomes. Results show that chest injury severity has a positive nonlinear correlation with impact speed. However, the injury risk is mainly determined by the seatbelt peak load in the chest deflection analysis. The results of this study can provide a reference to seatbelt safety design and optimization. The model and method can be used in other research works on the biomechanics of frontal impact.

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Han, Bing, Hao Feng, Yuan Yuan Liu e Feng Han. "Harmonic Impact on the Energy Meter". Advanced Materials Research 645 (gennaio 2013): 263–66. http://dx.doi.org/10.4028/www.scientific.net/amr.645.263.

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A large number of harmonics generated by nonlinear loads injected into the grid will make the power system voltage and current waveforms produce a serious distortion, in turn impact on the measuring instrument. Harmonic generation because and it’s impact on induction watt-hour meter are introduced in this paper, the measurement error on the induction meter is analized, and methods and countermeasures to reduce the induction meter power measurement error are proposed.

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Ma, Niu-Jing, Li-Xiong Gu e Long Piao. "Nonlinear Dynamic Response of Elastically Supported Stiffened Plates with Initial Stresses and Geometric Imperfections Under Impact Loads". International Journal of Structural Stability and Dynamics 20, n. 04 (aprile 2020): 2050053. http://dx.doi.org/10.1142/s0219455420500534.

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This paper deals with the nonlinear dynamic response of elastically supported stiffened plates with initial stresses under impact loads. A stiffened plate is assumed to be composed of a plate with some stiffeners, which are treated separately. The plate is modeled by the thin plate theory, whereas the stiffeners are considered as geometrically nonlinear Euler–Bernoulli beams. First, the equations of both the kinetic energies and strain energies of the plate and stiffeners are established. Then, the dynamic equilibrium equations for the stiffened plate are derived as the Lagrange’s equation of the functional. A parametric analysis is performed to evaluate how initial stresses, initial geometric imperfections, elastic supports, impact loads and configuration of stiffeners affect the time-history responses of the stiffened plates. Some useful nonlinear dynamic properties are obtained, which serve as references for engineering design and application.

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Iqbal, Muhammad Naveed, Lauri Kütt, Kamran Daniel, Bilal Asad e Payam Shams Ghahfarokhi. "Estimation of Harmonic Emission of Electric Vehicles and Their Impact on Low Voltage Residential Network". Sustainability 13, n. 15 (31 luglio 2021): 8551. http://dx.doi.org/10.3390/su13158551.

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The EV penetration in the low voltage residential grids is expected to increase rapidly in the coming years. It is expected that EV consumers will prefer overnight home charging because of its convenience and lack of charging infrastructure. The EV battery chargers are nonlinear loads and likely to increase the current harmonic emission in the distribution network. The imminent increase of EV load requires upgrading or managing the existing power system to support the additional charging load. This paper provides the estimation of the current harmonic emission of the EV charging load at different voltage distortions using the stochastic EV load model. The impact of EV charging on the distribution transformer is also presented.

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Rozegnał, Bartosz, Paweł Albrechtowicz, Dominik Mamcarz, Monika Rerak e Maciej Skaza. "The Power Losses in Cable Lines Supplying Nonlinear Loads". Energies 14, n. 5 (3 marzo 2021): 1374. http://dx.doi.org/10.3390/en14051374.

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This paper presents the skin effect impact on the active power losses in the sheathless single-core cables/wires supplying nonlinear loads. There are significant conductor losses when the current has a distorted waveform (e.g., the current supplying diode rectifiers). The authors present a new method for active power loss calculation. The obtained results have been compared to the IEC-60287-1-1:2006 + A1:2014 standard method and the method based on the Bessel function. For all methods, the active power loss results were convergent for small-cable cross-section areas. The proposed method gives smaller power loss values for these cable sizes than the IEC and Bessel function methods. For cable cross-section areas greater than 185 mm2, the obtained results were better than those for the other methods. There were also analyses of extra power losses for distorted currents compared to an ideal 50 Hz sine wave for all methods. The new method is based on the current penetration depth factor calculated for every considered current harmonics, which allows us to calculate the precise equivalent resistance for any cable size. This research is part of our work on a cable thermal analysis method that has been developed.

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Michalec, Łukasz, Michał Jasiński, Tomasz Sikorski, Zbigniew Leonowicz, Łukasz Jasiński e Vishnu Suresh. "Impact of Harmonic Currents of Nonlinear Loads on Power Quality of a Low Voltage Network–Review and Case Study". Energies 14, n. 12 (19 giugno 2021): 3665. http://dx.doi.org/10.3390/en14123665.

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The paper presents a power-quality analysis in the utility low-voltage network focusing on harmonic currents’ pollution. Usually, to forecast the modern electrical and electronic devices’ contribution to increasing the current total harmonic distortion factor (THDI) and exceeding the regulation limit, analyses based on tests and models of individual devices are conducted. In this article, a composite approach was applied. The performance of harmonic currents produced by sets of devices commonly used in commercial and residential facilities’ nonlinear loads was investigated. The measurements were conducted with the class A PQ analyzer (FLUKE 435) and dedicated to the specialized PC software. The experimental tests show that the harmonic currents produced by multiple types of nonlinear loads tend to reduce the current total harmonic distortion factor (THDI). The changes of harmonic content caused by summation and/or cancellation effects in total current drawn from the grid by nonlinear loads should be a key factor in harmonic currents’ pollution study. Proper forecasting of the level of harmonic currents injected into the utility grid helps to maintain the quality of electricity at an appropriate level and reduce active power losses, which have a direct impact on the price of electricity generation.

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Cointe, R. "Two-Dimensional Water-Solid Impact". Journal of Offshore Mechanics and Arctic Engineering 111, n. 2 (1 maggio 1989): 109–14. http://dx.doi.org/10.1115/1.3257083.

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The general problem of a two-dimensional water-solid impact is considered. The method of matched asymptotic expansions is used to solve the resulting boundary value problem for small penetration depth. The first-order solution obtained extends the classical Von Ka´rma´n and Wagner theories to non-normal impact and initially curved free surfaces. It accounts for nonlinear features such as the creation of a jet at each waterline. The application of the method to the computation of the impact loads exerted by spilling breakers on a marine structure is discussed.

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Liu, K., e J. Zhao. "Progressive Damage Behaviours of Triaxially Confined Rocks under Multiple Dynamic Loads". Rock Mechanics and Rock Engineering 54, n. 6 (5 maggio 2021): 3327–58. http://dx.doi.org/10.1007/s00603-021-02408-z.

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AbstractInvestigation of rock progressive damage under static confinement and strain rates facilitates the generation mechanism of natural fault damage zones. A triaxial Hopkinson bar apparatus is used to perform dynamic triaxial compression tests to examine the damage and degradation process of rocks subjected to multiple impacts. Dynamic mechanical properties are determined under a static triaxial pre-stress of (30, 20, 10) MPa and multiple dynamic loadings, with the repetitive impact velocity of 27 m/s and strain rates from 50 to 150/s. The acoustic characteristics are identified by ultrasonic measurement to qualify the damage values. The micro-crack parameters, including crack area and volumes are detected using synchrotron X-ray micro-computed tomography (μCT) to characterize the progressive damage. In addition, the microcrack orientation, density and fractal dimension are analysed from thin section. Experimental results show that dynamic stress-strain curves can be divided to elastic, nonlinear deformation and unloading phases. Dynamic peak stress, Young’s modulus and ultrasonic wave velocity decrease with increasing impact times. The high frequency of ultrasonic wave is filtered by the induced microcracks. The progressive damage and evolution of fracture networks are associated highly with microcrack initiation, propagation, branching and coalescence. Shear bands are commonly generated in granite, and tensile cracks are dominant in marble, while sandstone is mainly failed by compaction and deformation band. The absorbed energy of rock increases nonlinearly with increasing crack surface and volume. Besides, microcracks propagate primarily along the maximum principal stress; the density and fractal dimension exhibit an anisotropic distribution controlled by true triaxial confinement and dynamic impacts.

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Dong, Jun, Jian Guo Xu, Hao Zhang, Yu Jie Pei e Xian Feng Li. "Research and Application of SVC Technology in Grid". Applied Mechanics and Materials 543-547 (marzo 2014): 878–83. http://dx.doi.org/10.4028/www.scientific.net/amm.543-547.878.

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The cause serious deterioration in power quality problems for the growing impact and nonlinear load capacity, introduced SVC device in the role of modern power systems and applications. According to the lack of adequate regional dynamic reactive power regulation means to cause voltage fluctuations, harmonics exceeded the actual situation, through analysis and simulation of the existing 66kV grid power quality conditions, refers to the necessity of application of SVC, the compensation capacity for SVC, filter capacitor system parameters and control strategies were designed, the results show improved 220kV SVC reactive power flow distribution system, reducing the system once or twice a net loss, reducing the impact and harmonic interference voltage caused by nonlinear loads, system security, economic operation of great significance.

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Dong, Yongle, Fan Zhang, Xuan Li, Lifang Zhang, Jia Yu, Yongmei Mao e Guanglong Jiang. "Nonlinear Load Harmonic Prediction Method Based on Power Distribution Internet of Things". Scientific Programming 2021 (24 maggio 2021): 1–12. http://dx.doi.org/10.1155/2021/9978900.

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A large number of nonlinear loads have an impact on the stable operation of the power system. To solve this problem, this article proposes a nonlinear load harmonic prediction method based on the architecture of Power Distribution Internet of Things. Firstly, this method integrates the characteristics of edge computing technology and Power Distribution Internet of Things technology and proposes a Power Distribution Internet of Things framework applied to nonlinear load harmonic prediction, which provides top-level design for subsequent harmonic prediction methods of Power Distribution Internet of Things; then, considering the electrical characteristics of the typical nonlinear load, the mathematical model of nonlinear load data is constructed based on the harmonic coupling admittance matrix model on the edge side. At the same time, a nonlinear load harmonic prediction model based on dynamic time warping and long-term and short-term memory network (DTW-LSTM) is established in the cloud computing center to realize high accuracy and high real-time prediction and analysis of nonlinear load harmonics. Finally, the simulation results based on the general data set show that the MAE evaluation index of the proposed method is less than 5% in the experimental group, which shows good generalization ability, and has some advantages over the current method in operation efficiency.

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Bocian, Mirosław, Krzysztof Jamroziak e Maciej Kulisiewicz. "An identification of nonlinear dissipative properties of constructional materials at dynamical impact loads conditions". Meccanica 49, n. 8 (8 aprile 2014): 1955–65. http://dx.doi.org/10.1007/s11012-014-9931-z.

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Gholipour, Gholamreza, Chunwei Zhang e Asma Alsadat Mousavi. "Nonlinear failure analysis of bridge pier subjected to vessel impact combined with blast loads". Ocean Engineering 234 (agosto 2021): 109209. http://dx.doi.org/10.1016/j.oceaneng.2021.109209.

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Xi, Cao, e Yun Hong Hao. "The Doubly Nonlinear Limit Load Analysis of Space Grid Structure". Applied Mechanics and Materials 166-169 (maggio 2012): 144–49. http://dx.doi.org/10.4028/www.scientific.net/amm.166-169.144.

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This paper first adopts variational inequation—the method of linear complementary equation. We use this method to analyses the elastoplastic limit load of space grid structure. This is a way to resolve the nonlinear question. Adopting this method to resolve the limit load of space grid structure avoid some drawback caused by adopting iteration method. We only need do some limited compute to a load-increment then we can obtain consequence, which fit in with all condition. Particularly, though adopting the method of linear complementary equation, we can control the value of limit load, make the calculated load can not exceed the limit load. Once exceeding, computer can decrease load- increment automatically and load again till getting the limit load of structure. Based on elastoplastic limit load analysis, this paper has considered big deformation impact on the limit load of bspace grid structure. We have made analysis of doubly nonlinear limit loads under the condition of coupling out of elastoplastic big deformation. The method and theory of this paper can combine with all kinds of single rod mechanics model.

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Yao, Xing Jia, Jiang Sheng Zhu, Kui Chao Ma e Qing Ding Guo. "The Research of Model-Free Adaptive Control for Large Scale Wind Turbine". Applied Mechanics and Materials 433-435 (ottobre 2013): 1293–97. http://dx.doi.org/10.4028/www.scientific.net/amm.433-435.1293.

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Dynamic load is a key consideration in large scale wind turbine design. It is approved that the performance of controller can distinguish impact wind turbine loads. For strong external disturbances and inaccurately modeled of large wind turbines, In this paper, we propose model-free adaptive (Model Free Adapt, MFA) individual pitch control algorithms. The controller was developed in to mitigate the rotor unbalance structural load for variable speed wind turbine. The controller is designed from a nonlinear model of the system which takes into account the blades, shaft and tower flexibilities. Bladed software was used for the control strategy and traditional PID control strategy simulation comparison. The results show that the new control strategy can effectively stabilize wind turbine power output and reduce aerodynamic loads.

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Li, Jia-Xiang, Hong-Nan Li e Xing Fu. "Stability and Dynamic Analyses of Transmission Tower-Line Systems Subjected to Conductor Breaking". International Journal of Structural Stability and Dynamics 17, n. 06 (agosto 2017): 1771013. http://dx.doi.org/10.1142/s0219455417710134.

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Ice loads exerted on the transmission line can increase the probability of conductor breaking, which will lead to the stability failure of transmission towers. In this paper, a transmission tower-line system is established for two towers and three span lines. Then the nonlinear static stability analysis and nonlinear dynamic stability analysis induced by the conductor breaking are carried out to obtain the load versus displacement curves, while studying the failure modes of the transmission tower-line system. Moreover, the ice load and initial eccentricity are considered in the numerical simulation. In addition, a parametric analysis is performed to investigate the influence of span, insulator length and initial tension force on the stability failure of the system. The results show that the dynamic instability will occur earlier than the static instability due to the dynamic impact effect and conductor breaking with ice loads can lead to the progressive collapse of the transmission tower-line system. Finally, the span length has the greatest effect on the response of transmission tower caused by conductor breaking.

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Hao, Ceng Ceng, Yue Jin Tang e Jing Shi. "Study on the Harmonic Impact of Large Scale Electric Vehicles to Grid". Applied Mechanics and Materials 443 (ottobre 2013): 273–78. http://dx.doi.org/10.4028/www.scientific.net/amm.443.273.

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Large scale electric vehicles integration into power grid, as nonlinear loads, will pose inevitable impacts on the operation of power system, one of which the harmonic problem will affect the power quality greatly. Firstly, the article analyzes the characteristics of harmonic caused by electric vehicle charging. And then, the harmonic flow distribution is analyzed based on the IEEE standard node systems. During transient analyses, the electric vehicle charging stations connected to electric grid are represented as harmonic sources. Results show that structure and voltage grade of electric grid, capacity and access points of electric vehicle charging load will have different effects on harmonic problem. At last, a few conclusions are given for connecting electric vehicles to electric grid.

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Cheng, Qiangqiang, Yiqi Yan, Shichao Liu, Chunsheng Yang, Hicham Chaoui e Mohamad Alzayed. "Particle Filter-Based Electricity Load Prediction for Grid-Connected Microgrid Day-Ahead Scheduling". Energies 13, n. 24 (8 dicembre 2020): 6489. http://dx.doi.org/10.3390/en13246489.

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This paper proposes a particle filter (PF)-based electricity load prediction method to improve the accuracy of the microgrid day-ahead scheduling. While most of the existing prediction methods assume electricity loads follow normal distributions, we consider it is a nonlinear and non-Gaussian process which is closer to the reality. To handle the nonlinear and non-Gaussian characteristics of electricity load profile, the PF-based method is implemented to improve the prediction accuracy. These load predictions are used to provide the microgrid day-ahead scheduling. The impact of load prediction error on the scheduling decision is analyzed based on actual data. Comparison results on a distribution system show that the estimation precision of electricity load based on the PF method is the highest among several conventional intelligent methods such as the Elman neural network (ENN) and support vector machine (SVM). Furthermore, the impact of the different parameter settings are analyzed for the proposed PF based load prediction. The management efficiency of microgrid is significantly improved by using the PF method.

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Ganji, H. Doumiri, S. S. Ganji, D. D. Ganji e F. Vaseghi. "Analysis of Nonlinear Structural Dynamics and Resonance in Trees". Shock and Vibration 19, n. 4 (2012): 609–17. http://dx.doi.org/10.1155/2012/702712.

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Wind and gravity both impact trees in storms, but wind loads greatly exceed gravity loads in most situations. Complex behavior of trees in windstorms is gradually turning into a controversial concern among ecological engineers. To better understand the effects of nonlinear behavior of trees, the dynamic forces on tree structures during periods of high winds have been examined as a mass-spring system. In fact, the simulated dynamic forces created by strong winds are studied in order to determine the responses of the trees to such dynamic loads. Many of such nonlinear differential equations are complicated to solve. Therefore, this paper focuses on an accurate and simple solution, Differential Transformation Method (DTM), to solve the derived equation. In this regard, the concept of differential transformation is briefly introduced. The approximate solution to this equation is calculated in the form of a series with easily computable terms. Then, the method has been employed to achieve an acceptable solution to the presented nonlinear differential equation. To verify the accuracy of the proposed method, the obtained results from DTM are compared with those from the numerical solution. The results reveal that this method gives successive approximations of high accuracy solution.

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Hernández, Jairo, Andrés A. Romero, Jan Meyer e Ana María Blanco. "Impact of Nonlinear Lighting Loads on the Neutral Conductor Current of Low Voltage Residential Grids". Energies 13, n. 18 (16 settembre 2020): 4851. http://dx.doi.org/10.3390/en13184851.

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In the last decade, mainly due to political incentives towards energy efficiency, the share of lamps with power electronic interfaces, like Compact Fluorescent Lamps (CFL) and Light Emitting Diode (LED) lamps, has significantly increased in the residential sector. Their massive use might have a substantial impact on harmonic currents and, consequently, on the current flowing in the neutral conductor. This paper analyzes the impact of modern energy-efficient lighting technologies on the neutral conductor current by using a synthetic Low Voltage residential grid. Different load scenarios reflecting the transition from incandescent lamps, via CFL, to LED lamps are compared concerning the neutral conductor current at different points in the network. The inherent randomness related to the use of lighting devices by each residential customer is considered employing a Monte Carlo simulation. Obtained results show that the use of CFL has a greater impact on the neutral conductor current of Low Voltage (LV) residential grids and that, with increasing use of LED lamps, a decreasing impact can be expected in the future.

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Pakhmurin, Oleg, Victor Mikhaylov e Matvey Khamgushkeev. "Impact of genetically nonlinear application of external loads on the stress-strain state and on the principal vibration modes of reinforced concrete frame buildings on elastic subsoil". EPJ Web of Conferences 221 (2019): 01038. http://dx.doi.org/10.1051/epjconf/201922101038.

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In this paper authors discuss the impact of genetically nonlinear application of external loads on the stress-stain state and on principal vibration modes of reinforced concrete frame structures on elastic foundation. The reader will find a methodology for integrated numerical and instrumental analysis. Six examples of linear and nonlinear FEA-models calculated in SCAD Office are given in comparison.

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Zhu, Shengyang, Jun Luo, Mingze Wang e Chengbiao Cai. "Mechanical characteristic variation of ballastless track in high-speed railway: effect of train–track interaction and environment loads". Railway Engineering Science 28, n. 4 (30 novembre 2020): 408–23. http://dx.doi.org/10.1007/s40534-020-00227-6.

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AbstractDue to the fact that ballastless tracks in high-speed railways are not only subjected to repeated train–track dynamic interaction loads, but also suffer from complex environmental loads, the fundamental understanding of mechanical performance of ballastless tracks under sophisticated service conditions is an increasingly demanding and challenging issue in high-speed railway networks. This work aims to reveal the effect of train–track interaction and environment loads on the mechanical characteristic variation of ballastless tracks in high-speed railways, particularly focusing on the typical interface damage evolution between track layers. To this end, a finite element model of a double-block ballastless track involving the cohesive zone model for the track interface is first established to analyze the mechanical properties of the track interface under the loading–unloading processes of the negative temperature gradient load (TGL) followed by the same cycle of the positive TGL. Subsequently, the effect of wheel–rail longitudinal interactions on the nonlinear dynamic characteristics of the track interface is investigated by using a vehicle-slab track vertical-longitudinal coupled dynamics model. Finally, the influence of dynamic water pressure induced by vehicle dynamic load on the mechanical characteristics and damage evolution of the track interface is elucidated using a fluid–solid coupling method. Results show that the loading history of the positive and negative TGLs has a great impact on the nonlinear development and distribution of the track interface stress and damage; the interface damage could be induced by the wheel–rail longitudinal vibrations at a high vehicle running speed owing to the dynamic amplification effect caused by short wave irregularities; the vehicle dynamic load could produce considerable water pressure that presents nonlinear spatial–temporal characteristics at the track interface, which would lead to the interface failure under a certain condition due to the coupled dynamic effect of vehicle load and water pressure.

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40

Zheng, Enlai, Xinlong Zhou e Sihong Zhu. "Dynamic response analysis of block foundations with nonlinear dry friction mounting system to impact loads". Journal of Mechanical Science and Technology 28, n. 7 (luglio 2014): 2535–48. http://dx.doi.org/10.1007/s12206-014-0611-7.

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41

Mousseau, R., e G. Markale. "Obstacle Impact Simulation of an ATV Using an Efficient Tire Model". Tire Science and Technology 31, n. 4 (1 ottobre 2003): 248–69. http://dx.doi.org/10.2346/1.2135271.

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Abstract When a vehicle travels over a large obstacle at a significant speed, dynamic loads are created that are severe enough to cause damage to its components. Prediction of these impact loads early in the design can greatly aid the vehicle development process. Thus, automobile manufactures have devoted considerable effort developing computer models to simulate durability events. An important part of any durability simulation is the tire model. This paper focuses on the problem of efficiently predicting dynamic loads that occur when an all terrain vehicle (ATV) impacts obstacle impact. An ATV simulation model that uses an efficient and simple tire model to represent the enveloping behavior and dynamic response was developed with the AUTOSIM multibody dynamics program. This program, using Kane's Method and symbolic algebra to automatically generate fully parametric simulations that are both efficient and easy to use, was used to model both the tire and ATV rigid body dynamics. This paper describes the combined ATV multi-body vehicle dynamics and tire simulation. To demonstrate the effectiveness of tire simulation, results from the efficient tire model isolated from the vehicle are compared to output from a nonlinear finite element model. Also, the paper compares results from the full vehicle ATV simulation and a field test.

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Ali, Saima, Xuemei Liu, Sabrina Fawzia e David Thambiratnam. "Study of the Mechanical Performance of the Improved Multi-Layer Composites Under Drop Weight Impact Loads". International Journal of Structural Stability and Dynamics 20, n. 06 (giugno 2020): 2040002. http://dx.doi.org/10.1142/s0219455420400027.

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This study attempts to propose innovative multi-layer cement-based composites to have high impact resistance which could be used for runway. In this paper, the performances of two innovative multi-layer composite runway pavements using asphalt concrete-high strength concrete-cement-treated aggregate and asphalt concrete-high strength concrete-cement mortar in surface-base-subbase layer were evaluated under impact loads. ABAQUS/Explicit software was used to simulate loading condition and nonlinear stabilized runway pavement layers characteristics. In addition, a detailed parametric study was also carried out to explore the effects of the selected materials and load-related parameters in changing the performance of multi-layer composites. The findings of the study will be helpful to introduce protective multi-layer composite runway pavement and consequently to reduce the maintenance work of runway pavement.

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Egorov, D. E., V. P. Dovgun, N. P. Boyarskaya, A. V. Jan e A. S. Slyusarev. "Power factor correction in power delivery systems with mutipulse nonlinear loads". Power engineering: research, equipment, technology 22, n. 6 (26 marzo 2021): 3–15. http://dx.doi.org/10.30724/1998-9903-2020-22-6-3-15.

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THE PURPOSE. Мutipulse rectifiers are widely used as a nonlinear loads in industrial distribution systems. The advantage of mutipulse rectifiers is low harmonic emission and high power factor. However input currents of mutipulse rectifiers have a wide spectrum including characteristic and noncharacteristic harmonics. This has a negative impact on the power quality. Shunt capacitors are the simplest form of reactive power compensation in industrial power distribution systems. However power systems with nonlinear loads suffer from severe harmonic distortion due to the parallel resonance between capacitors and system inductance. Special compensating devices for reactive power compensation and correction of power system frequency response for resonances damping are necessary. METHODS. In this paper shunt compensating devices for power delivery systems with multipulse nonlinear loads are considered. Proposed devices are composed of 3-5 order parallel connected passive broadband filters. They provide power factor correction, voltage and current harmonics mitigation and resonance modes damping. A general broadband filter design procedure based on frequency and reactive power scaling of normalized filter parameters is developed. RESULTS. Characteristics of different compensating devices configurations using broadband passive filters are discussed. It is shown that broadband filtering devices enable compensation of fundamental frequency reactive power as well as mitigation of voltage harmonic level to values determined by Russian and international standards. Proposed devices have lower fundamental power losses in c omparing with known solutions. CONCLUSION. Proposed analytical design method is applicable to broadband filters of different orders.

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Geanta, Victor, Ionelia Voiculescu, Tudor Chereches, Teodora Zecheru, Liviu Matache e Adrian Rotariu. "Behavior to Dynamic Loads of Multi-layer Composite Structures". Materiale Plastice 56, n. 2 (30 giugno 2019): 460–65. http://dx.doi.org/10.37358/mp.19.2.5207.

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The explosive effect and high velocity penetration of the ballistic projectiles of various sizes, design and compositions, on impact with different targets (armors composed of a combination of different metals) are complex. Both practical experiments and mathematical modeling of the phenomena associated to the interaction projectile-target are required to estimate their effect or to design more efficient projectiles and armor. In this study, the basic element of the simulation model is an incendiary projectile of caliber 7.62 mm with medium piercing power, launched with a maximum speed of 750 ms-1 on the multi-material target, which contains 4 different layers assembled into a ballistic cassette made of aluminum. The purpose of this ballistic cassette is to ensure a better contact and handling of multi-layer materials. The proposed model was calculated using mathematical modeling and empirical material constants to describe the nonlinear transitory impact process. Mathematical simulation of the impact between the projectile and target during impact shows that the projectile moves sequentially through the ballistic package, causing perforation, plastic deformation and heating, the resulting fragments being then expelled into the space around the target. The model indicates that the projectile will penetrate the front aluminum plate, as well as the AlCrFeCoNi and steel plates, but will be stopped by the aluminum backing plate. The real impact tests carried out using the ballistic cassette at dynamic impact with the 7.62mm incendiary projectile confirm the model assumptions, which prove the capacity of the composite model to safely stop the projectile.

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Currie-Gregg, Nancy J., e Kelly Carney. "Development of a finite element human vibration model for use in spacecraft coupled loads analysis". Journal of Low Frequency Noise, Vibration and Active Control 38, n. 2 (27 aprile 2018): 839–51. http://dx.doi.org/10.1177/1461348418757994.

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Finite element human vibration models were developed and implemented for use in human-tended spacecraft-coupled loads analysis, an analytical process used to predict low-frequency spacecraft loads which occur during dynamic phases of flight of such as launch, ascent, or ascent aborts. Human vibration may also affect stress predictions for spacecraft systems which the crew interacts with, such as crew seats and crew impact attenuation systems. These human vibration models are three-dimensional, distributed-mass representations of 1st-percentile female, 50th-percentile male, and 99th-percentile male American crew members and provide a relatively simple linear and low-load representation of the nonlinear dynamic response of a seated human. The most significant features of these finite element models are anthropometrically based geometric human mass distribution, soft tissue vibration attributes, and skeleton and joint stiffness.

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Zhu, Rui, Baoquan Mao, Qijin Zhao, Zhiqian Wang, Xiaoping Han, Yuying Yang e Hua Li. "Dynamic characteristics of Mn-Cu high damping alloy subjected to impact load". Advances in Mechanical Engineering 13, n. 4 (aprile 2021): 168781402110136. http://dx.doi.org/10.1177/16878140211013616.

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Mn-Cu high damping alloy is a twin-type damping alloy. Owing to its martensite twin structure at room temperature, it can convert vibration energy into heat energy, thereby reducing vibration. Although essentially a nonlinear elastic material, Mn-Cu damping alloys are treated as linear elastic materials in current engineering practice. However, introducing a constant damping coefficient alone will produce significant errors when modeling vibration reduction characteristics of the material, especially under impact loading. In this study, vibration test was performed on Mn-Cu damping alloy cantilever beam subjected to an impact load and deviation between the test result and the one of existing modeling method was analyzed. A generalized fractional-order Maxwell model was established to describe the nonlinear constitutive relation of the Mn-Cu damping alloy. Then, the model was extended to the three-dimensional state and a secondary development was performed. Finally, various applications for the damping alloy were explored and the effects of the damping alloy on the vibration characteristics of composite cantilever beam structures subjected to impact loads were investigated with the aim of better understanding the dynamic characteristics and improving the effectiveness of vibration reduction applications using Mn-Cu damping alloy in the future.

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Park, S. U., B. J. Gilmore e R. R. Singer. "Simulation of Nonlinear Dynamics of Liquid Filled Fuel Tanker Shell Structure Subjected to Rollover Collision With Validation". Journal of Mechanical Design 120, n. 4 (1 dicembre 1998): 573–80. http://dx.doi.org/10.1115/1.2829317.

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The transport of hazardous materials in truck cargo tanks can cause severe environmental damage as a result of the tank’s failure during a collision. Impact due to collision involves the transient dynamic response of the tank, fluid and their interaction. This paper develops a design oriented computational approach to predict the dynamic transient response of the tank shell structure subjected to impact loads during crash accidents. In order to compute the fluid and structural interaction, the finite element formulations for the added mass to the structure are developed and integrated with DYNA3D, a nonlinear dynamic structural finite element code, and they are validated by pendulum impact experiment. This paper presents the lumping process required by the added mass approach for cargo tanks under impact conditions. Thus, due to its efficiency the computer based approach provides a design tool for fluid filled thin walled structures in general and cargo tanks subjected to an impact situation. The structural performance of cargo tank shell construction is investigated. This research will contribute to improvement in design, modeling, and analysis techniques for crashworthiness and integrity of liquid mechanical structure systems which are subjected to impulsive loads like those found in vehicle collisions.

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Zhang, ZH, Y. Chen, HX Hua e Y. Wang. "Crush dynamics of rubber tube under low velocity impact". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 228, n. 3 (24 aprile 2013): 426–40. http://dx.doi.org/10.1177/0954406213486871.

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It is proved that hyperelastic honeycomb coatings can attenuate underwater blast loads impinged on the ship hull. The crush behavior of a unit tube cell of the coating made of rubber material is investigated in this study. A series of tests are conducted to investigate the crush dynamic behavior of the tube under low velocity impact loads. Numerical analyses are carried out to explore the impact process of the rubber tube and the role of some dynamic parameters, thereby serve as a reference in the design of new coating. Some characteristics, such as the geometric imperfections, nonlinear elasticity and material viscosity, are analyzed. The results of simulation and experiments show that the geometric imperfections not only attenuate the shock force in the buckling and the force plateau stages, but also enhance the shock force in the densification stage greatly and promote the global peak force initiation, while the material viscosity enhances the force plateau and attenuates the shock force in the densification stage greatly. These effects are illustrated and quantified with the aid of experiments and numerical calculations.

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Stumberger, Gorazd, Miran Roser, Ivan Skratek e Viktor Tajnsek. "Experimentally evaluated impact of nonlinear loads on the energy transmission losses and distortion of voltage waveforms". Renewable Energy and Power Quality Journal 1, n. 08 (aprile 2010): 449–54. http://dx.doi.org/10.24084/repqj08.355.

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Marino, Enzo, Claudio Borri e Udo Peil. "A fully nonlinear wave model to account for breaking wave impact loads on offshore wind turbines". Journal of Wind Engineering and Industrial Aerodynamics 99, n. 4 (aprile 2011): 483–90. http://dx.doi.org/10.1016/j.jweia.2010.12.015.

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