Готові списки джерел за темами / Multi-input loading

Добірка наукової літератури з теми "Multi-input loading"

Автор: Grafiati

Опубліковано: 17 лютого 2024

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Статті в журналах з теми "Multi-input loading"

Zhi, Hao, and Jiahao Lin. "Random loading identification of multi-input-multi-output structure." Structural Engineering and Mechanics 10, no. 4 (October 25, 2000): 359–69. http://dx.doi.org/10.12989/sem.2000.10.4.359.

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Wang, J., S. Jiang, J. He, and Z. Liu. "Adaptive detectors with diagonal loading for airborne multi-input multi-output radar." IET Radar, Sonar & Navigation 3, no. 5 (2009): 493. http://dx.doi.org/10.1049/iet-rsn.2008.0128.

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Baroux, Emilien, Benoit Delattre, Andrei Constantinescu, Patrick Pamphile, and Ida Raoult. "Analysis Of Real-Life Multi-Input Loading Histories For The Reliable Design Of Vehicle Chassis." Procedia Structural Integrity 38 (2022): 497–506. http://dx.doi.org/10.1016/j.prostr.2022.03.050.

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Kuriki, M., S. Kuroguchi, H. Tajino, T. Takahashi, Z. Liptak, T. Omori, J. Urakawa, and K. Yokoya. "Beam Loading Compensation of Traveling Wave Linac to a Multi-bunch Pulse with Gaps." Journal of Physics: Conference Series 2687, no. 2 (January 1, 2024): 022012. http://dx.doi.org/10.1088/1742-6596/2687/2/022012.

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Abstract In the electron driven ILC (International Linear Collider) positron source, the beam is generated and accelerated in a multi-bunch format with mini-trains. The macro-pulse contains 2 to 4 mini-trains with several gaps, because the pulse format is a copy of a part of the bunch storage pattern in DR (Damping Ring). This pulse format causes a variation of the accelerator field in the pulse due to the transient beam loading and an intensity fluctuation of captured positron. The beam loading is compensated by amplitude modulation on the input RF in the positron booster composed from L-band and S-band traveling wave RF cavity. In this article, we derive the exact solution for the compensation with the gaps. In addition, we evaluate the effect of the time constant (delay) of the input RF modulation due to klystron Q-value.

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Tang, Enling, Li Wang, Ruizhi Wang, Yafei Han, Xiaochu Lin, Guowen Gao, Liping He, Shenghai Xiang, and Meng Wang. "Influence of the Storage Energy Capacitance on Their Electrical Output Characteristics of Piezoelectric Ceramic during the Process of High-Velocity Impact." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 36, no. 5 (October 2018): 949–54. http://dx.doi.org/10.1051/jnwpu/20183650949.

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In order to reveal influence of external capacitance on the voltage input and input energy provided by the PZT-5H piezoelectric ceramic composite structure under high-speed impact loading, experiments have been performed by using one-stage light gas gun loading system combining with a power supplier circuit and power output testing system, which the aspect ratio of 1:1 column projectile impact monolithic and multi-piece piezoelectric ceramic composite structure at the near impact velocity and different storage capacity. The experimental results show that the more larger storage capacitance is, the smaller the piezoelectric ceramic output voltage is. However, the smaller of the capacitor voltage is, the smaller the value of energy storage is; with the energy storage capacitance increasing, the piezoelectric capacitance ratio and the energy conversion rate of piezoelectric ceramics decreases; In addition, the storage energy capacitor increases with the increasing of the piezoelectric ceramic layers; the relationships of storage energy capacitor and piezoelectric ceramic capacitor has a great influence on the input voltage and storage energy for storage energy capacitor.

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Zhang, Lin, Cheng-ge Wu, and Gan-wei Cai. "The inverse kinematics analysis and simulation study on the controllable loading mechanism." MATEC Web of Conferences 189 (2018): 06011. http://dx.doi.org/10.1051/matecconf/201818906011.

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The multi-DOF controllable loading mechanism adopts the electric drive system to replace the hydraulic drive system of traditional loader, not only has higher transmission efficiency and has better mechanical and electrical integration level, but also overcome the shortcomings of high cost of manufacture and maintenance.The inverse kinematics model of this type of loading mechanism was built by means of closed loop vector method. According to the performance index of the loading mechanism, the inverse kinematics model was solved by means of MATLAB software, and the input motion law of the two driving lever at different period of time is obtained, and a small prototype is built, which provides the basis for control system programming of this new type of leading mechanism. To some extent, this research lays a foundation for further development of this type of loading mechanism.

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Chen, Mu-Chun, Tsung-Wen Sun, and Tsung-Heng Tsai. "Dual-Domain Maximum Power Tracking for Multi-Input RF Energy Harvesting with a Reconfigurable Rectifier Array." Energies 15, no. 6 (March 11, 2022): 2068. http://dx.doi.org/10.3390/en15062068.

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This work proposes a dual-domain maximum power tracking (MPPT) technique for multiple-input RF energy harvesting systems. A differential rectifier array is used to implement 4-channel reconfigurable RF to DC power conversion, and an adjustable 4-bit capacitor array is designed to improve the impedance matching between the antennas and the rectifiers. Using the perturbation and observation (P&O) method, both arrays are adaptively configured in the background with the variations of the input energy and output loading. Experimental results show that the proposed circuit successfully tracks the maximum power points while harvesting RF energy, with the peak conversion efficiency of 49.06% when the input energy is −6 dBm. With the proposed dual-domain MPPT, the high efficiency range of the energy harvesting system is greatly extended to 21 dB (−21–0 dBm).

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Kushvaha, Vinod, S. Anand Kumar, Priyanka Madhushri, and Aanchna Sharma. "Artificial neural network technique to predict dynamic fracture of particulate composite." Journal of Composite Materials 54, no. 22 (March 8, 2020): 3099–108. http://dx.doi.org/10.1177/0021998320911418.

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In this paper, the artificial neural network technique using a multi-layer perceptron feed forward scheme was used to model and predict the mode-I fracture behaviour of particulate polymer composites when subjected to impact loading. A neural network consisting of three-layers was employed to develop the network. Artificial neural network was constructed using six input parameters such as shear wave speed ( CS), density ( D), elastic modulus ( Ed), longitudinal wave speed ( CL), volume fraction ( Vf) and time ( t). The influence of input parameters on the output stress intensity factor and crack-initiation fracture toughness were found to be in the order of t > CS > D > Ed > CL > Vf. The degree of accuracy of prediction was 92.7% for stress intensity factor. In this regard, artificial neural network can be used in the modelling and prediction of fracture behaviour of particulate polymer composites under impact loading.

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Kuriki, M., S. Konno, H. Tajino, Z. Liptak, T. Takahashi, M. Fukuda, T. Omori, et al. "Beam loading compensation of standing wave linac with off-crest acceleration." Journal of Physics: Conference Series 2420, no. 1 (January 1, 2023): 012007. http://dx.doi.org/10.1088/1742-6596/2420/1/012007.

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Abstract In E-Driven positron source of ILC, the generated positron is captured by a standing wave cavity. Because the deceleration capture method is employed, the positron is off-crest over the linac. Because the beam-loading is expected to be more than 1A in a multi-bunch format, the compensation is essential to obtain uniform intensity over the pulse. A conventional method for the compensation controlling the timing doesn’t work because RF and Beam induced field are in different phase. In this manuscript, we discuss the compensation with the off-crest acceleration case. A simple phase modulation on the input RF is a solution.

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Koofigar, Hamid Reza, and Ghader Isazadeh. "Optimal robust stabilizer design based on UPFC for interconnected power systems considering time delay." Archives of Electrical Engineering 66, no. 3 (September 1, 2017): 459–74. http://dx.doi.org/10.1515/aee-2017-0034.

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AbstractA robust auxiliary wide area damping controller is proposed for a unified power flow controller (UPFC). The mixedH2/H∞problem with regional pole placement, resolved by linear matrix inequality (LMI), is applied for controller design. Based on modal analysis, the optimal wide area input signals for the controller are selected. The time delay of input signals, due to electrical distance from the UPFC location is taken into account in the design procedure. The proposed controller is applied to a multi-machine interconnected power system from the IRAN power grid. It is shown that the both transient and dynamic stability are significantly improved despite different disturbances and loading conditions.

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Більше джерел

Дисертації з теми "Multi-input loading"

Bellec, Enora. "Spectres de chargement pour le dimensionnement à la fatigue d’un véhicule automobile : identification, analyse et modélisation." Electronic Thesis or Diss., Brest, École nationale supérieure de techniques avancées Bretagne, 2023. http://www.theses.fr/2023ENTA0003.

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Les constructeurs automobiles se doivent d’assurer la fiabilité de l’ensemble des pièces de la liaison au sol sur toute la durée de vie du véhicule. Cependant, aucun cadre normatif global n’existe pour le dimensionnement de ces pièces. Ils doivent donc se baser sur leur expérience. Il est nécessaire pour tout protocole de dimensionnement de maîtriser précisément les chargements vus par les pièces. La sollicitation perçue par la liaison au sol est d’autant plus complexe à considérer qu’elle est à amplitude variable (suivant les situations de vie rencontrées) et multi-entrées (chargements perçus à chaque roue simultanément). Pour le dimensionnement à la fatigue, les sollicitations perçues aux roues sont modélisées comme la somme des chargements issus des manoeuvres, dits Driven Road, et de ceux induits par les aléas de la route, dits Random Road. Un processus de validation de cette partition est illustré à partir de mesures réelles. Il tire parti des particularités de chaque type de chargement, corrélation temporelle et caractéristiques fréquentielles, pour prendre en compte le caractère multi-entrées de la sollicitation. Ce modèle apporte au constructeur des éléments supplémentaires pour caractériser les chargements
Car manufacturers are responsible for ensuring the reliability of all chassis components throughout the life of the vehicle. Nevertheless, no global standard framework exists. Therefore, they must rely on their own experience. For any design protocol, it is imperative to precisely define the loads seen by the parts. The load measures by the chassis system is even more complex to assess as it faces variable amplitude (depending on the life situations encountered) and multi-input load case (loads perceived at each wheel simultaneously). For fatigue design, the loads measured at the wheels are modelled as the sum of the ones induced by the manoeuvers, called Driven Road, and the ones induced by the road conditions, called Random Road. A validation process of the partition is illustrated using real time series. It benefits from the particularities of each loading type, time correlation and frequency characteristics, to consider the multi-input character of the load case. This model provides the manufacturer with additional elements to characterise the loadings

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Bhat, Anirudh. "Response of multi-path compliant interconnects subjected to drop and impact loading." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/50132.

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Conventional solder balls used in microelectronic packaging suffer from thermo- mechanical damage due to difference in coefficient of thermal expansion between the die and the substrate or the substrate and the board. Compliant interconnects are replacements for solder balls which accommodate this differential displacement by mechanically decoupling the die from the substrate or the substrate from the board and aim to improve overall reliability and life of the microelectronic component. Research is being conducted to develop compliant interconnect structures which offer good mechanical compliance without adversely affecting electrical performance, thus obtaining good thermo-mechanical reliability. However, little information is available regarding the behavior of compliant interconnects under shock and impact loads. The objective of this thesis is to study the response of a proposed multi-path compliant interconnect structure when subjected to shock and impact loading. As part of this work, scaled-up substrate-compliant interconnect-die assemblies will be fabricated through stereolithography techniques. These scaled-up prototypes will be subjected to experimental drop testing. Accelerometers will be placed on the board, and strain gauges will be attached to the board and the die at various locations. The samples will be dropped from different heights to different shock levels in the components, according to Joint Electron Devices Engineering Council (JEDEC) standards. In parallel to such experiments with compliant interconnects, similar experiments with scaled-up solder bump interconnects will also be conducted. The strain and acceleration response of the compliant interconnect assemblies will be compared against the results from solder bump interconnects. Simulations will also be carried out to mimic the experimental conditions and to gain a better understanding of the overall response of the compliant interconnects under shock and impact loading. The findings from this study will be helpful for improving the reliability of compliant interconnects under dynamic mechanical loading.

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Частини книг з теми "Multi-input loading"

Sequeira, Movin. "Multi-Stage Fuzzy-Logic Model for Evaluation of Reshoring Decisions." In Advances in Transdisciplinary Engineering. IOS Press, 2021. http://dx.doi.org/10.3233/atde210110.

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Reshoring decisions are complex due to multiple groups of criteria that have an impact on the decision involved. In order to support this manual decision-making process, more advanced tools need to be developed. The purpose of this paper is to explore a multi-stage fuzzy-logic model to support the reshoring decision-making process through a transdisciplinary approach. Three relevant stages pertaining to reshoring decisions were identified: production resources, production capabilities, and competitive priorities. For each stage, factor loading values were used to create fuzzy rules. The model provides a decision recommendation based on a set of input reshoring scenarios. The research contributes to the reshoring literature providing a multi-stage fuzzy-logic model that simultaneously handles different groups of criteria, and to practitioners by contemplating different key competencies within a company during the reshoring decision process.

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V., Karthickeyan, Balamurugan S., Ashok B., Thiyagarajan S., Mohamed Shameer P., and Dhinesh Balasubramanian. "Process Optimization Study of Alternative Fuel Production From Linseed Oil." In Recent Technologies for Enhancing Performance and Reducing Emissions in Diesel Engines, 234–49. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-7998-2539-5.ch012.

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This chapter focuses on the selection of optimum parameters for transesterification of linseed oil biodiesel production in the presence of calcium oxide (CaO) obtained from the waste eggshells. The waste chicken eggshells were calcined at 900°C for 4 hours and it was characterized by X-ray diffractometer (XRD). The transesterification process was conducted according to L9 orthogonal array with selected input control parameters such as methanol to oil molar ratio, reaction temperature, and catalyst loading. The output parameters were biodiesel yield and viscosity. The multi-objective, decision-making technique called Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) was used to identify the optimum transesterification process parameters to obtain maximum biodiesel yield with minimal viscosity. The optimized values for transesterification process parameters were depicted as methanol to oil ratio of 6:1, reaction temperature of 65°C, and catalyst loading of 5% w/w.

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Dimitri, Rossana, and Giorgio Zavarise. "Numerical Study of Discrete Masonry Structures under Static and Dynamic Loading." In Computational Modeling of Masonry Structures Using the Discrete Element Method, 254–91. IGI Global, 2016. http://dx.doi.org/10.4018/978-1-5225-0231-9.ch011.

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Much of the world's architectural heritage consists of Unreinforced Masonry (URM) structures whose preservation is a topical subject. To prevent possible collapse of multi-block systems in hazardous conditions, a promising tool to investigate their structural response is represented by numerical modelling with the Discrete Element Method (DEM). Gothic buttresses of trapezoidal and stepped shapes are first analysed comparatively under static loading, defining the optimal configurations. Numerical results are verified against the analytical predictions of overturning and sliding resistances, based on a continuum approximation of masonry. The DEM is then successfully adopted to assess the first-order seismic behavior of arches and buttressed arches with different shapes as compared to predictions based on limit analysis. A systematic investigation on dynamic behavior failure domains and on modes of collapse of URM structures is finally performed for varying input parameters, as needed to gain more confidence on the numerical results.

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Тези доповідей конференцій з теми "Multi-input loading"

Tan, X. G., Andrzej J. Przekwas, Gregory Rule, Kaushik Iyer, Kyle Ott, and Andrew Merkle. "Modeling Articulated Human Body Dynamics Under a Representative Blast Loading." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-64331.

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Blast waves resulting from both industrial explosions and terrorist attacks cause devastating effects to exposed humans and structures. Blast related injuries are frequently reported in the international news and are of great interest to agencies involved in military and civilian protection. Mathematical models of explosion blast interaction with structures and humans can provide valuable input in the design of protective structures and practices, in injury diagnostics and forensics. Accurate simulation of blast wave interaction with a human body and the human body biodynamic response to the blast loading is very challenging and to the best of our knowledge has not been reported yet. A high-fidelity computational fluid dynamic (CFD) model is required to capture the reflections, diffractions, areas of stagnation, and other effects when the shock and blast waves respond to an object placed in the field. In this effort we simulated a representative free field blast event with a standing human exposed to the threat using the Second Order Hydrodynamic Automatic Mesh Refinement Code (SHAMRC). During the CFD analysis the pressure time history around the human body is calculated, along with the fragment loads. Subsequently these blast loads are applied to a fully articulated human body using the multi-physics code CoBi. In CoBi we developed a novel computational model for the articulated human body dynamics by utilizing the anatomical geometry of human body. The articulated human body dynamics are computed by an implicit multi-body solver which ensures the unconditional stability and guarantees the quadratic rate of convergence. The developed solver enforces the kinematic constraints well while imposing no limitation on the time step size. The main advantage of the model is the anatomical surface representation of a human body which can accurately account for both the surface loading and the surface interaction. The inertial properties are calculated using a finite element method. We also developed an efficient interface to apply the blast wave loading on the human body surface. The numerical results show that the developed model is capable of reasonably predicting the human body dynamics and can be used to study the primary injury mechanism. We also demonstrate that the human body response is affected by many factors such as human inertia properties, contact damping and the coefficient of friction between the human body and the environment. By comparing the computational results with the real scenario, we can calibrate these input parameters to improve the accuracy of articulated human body model.

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Tan, X. G., R. Kannan, Andrzej J. Przekwas, Kyle Ott, Tim Harrigan, Jack Roberts, and Andrew Merkle. "An Enhanced Articulated Human Body Model Under C4 Blast Loadings." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-89067.

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Previously we had developed an articulated human body model to simulate the kinematic response to the external loadings, using CFDRC’s CoBi implicit multi-body solver. The anatomy-based human body model can accurately account for the surface loadings and surface interactions with the environment. A study is conducted to calibrate the joint properties (for instance, the joint rotational damping) of the articulated human body by comparing its response with those obtained from the PMHS test under moderate loading conditions. Additional adjustments in the input parameters also include the contact spring constants for joint stops at different joint locations. By comparing the computational results with the real scenarios, we fine tune these input parameters and further improve the accuracy of the articulated human body model. In order to simulate the effect of a C4 explosion on a human body in the open field, we employ a CFD model with a good resolution and the appropriate boundary treatment to obtain the blast loading condition on the human body surface more accurately. The numerical results of the blast simulation are shown to be comparable to the test data. With the interface to apply the blast pressure loading from the CFD simulation on the articulated human body surface, the articulated human body dynamics due to the C4 explosions are modeled and the simulation results are shown to be physiological reasonable.

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Datar, M., D. Negrut, D. Gorsich, and D. Lamb. "A Framework for Uncertainty Quantification in Nonlinear Multi-Body System Dynamics." In ASME 2009 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/detc2009-86286.

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This paper outlines a methodology for determining the statistics associated with the time evolution of a nonlinear multi-body dynamic system operated under input uncertainty. The focus is on the dynamics of ground vehicle systems in environments characterized by multiple sources of uncertainty: road topography, friction coefficient at the road/tire interface and aerodynamic force loading. Drawing on parametric maximum likelihood estimation, the methodology outlined is general and can be applied to systematically study the impact of sources of uncertainty characterized herein by random processes. The proposed framework is demonstrated through a study that characterizes the uncertainty induced in the loading of the lower control arm of an SUV type vehicle by uncertainty associated with road topography.

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Choi, K. S., and J. Pan. "A Generalized Anisotropic Hardening Rule Based on the Mroz Multi-Yield-Surface Model." In ASME 2008 Pressure Vessels and Piping Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/pvp2008-61800.

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In this paper, a generalized anisotropic hardening rule based on the Mroz multi-yield-surface model is derived. The evolution equation for the active yield surface is obtained by considering the continuous expansion of the active yield surface during the unloading/reloading process. The incremental constitutive relation based on the associated flow rule is then derived for a general yield function. As a special case, detailed incremental constitutive relations are derived for the Mises yield function. The closed-form solutions for one-dimensional stress-plastic strain curves are also derived and plotted for the Mises materials under cyclic loading conditions. The stress-plastic strain curves show closed hysteresis loops under uniaxial cyclic loading conditions and the Masing hypothesis is applicable. A user material subroutine based on the Mises yield function, the anisotropic hardening rule and the constitutive relations was then written and implemented into ABAQUS. Computations were conducted for a simple plane strain finite element model under uniaxial monotonic and cyclic loading conditions based on the anisotropic hardening rule and the isotropic and nonlinear kinematic hardening rules of ABAQUS. The results indicate that the plastic response of the material follows the intended input stress-strain data for the anisotropic hardening rule whereas the plastic response depends upon the input strain ranges of the stress-strain data for the nonlinear kinematic hardening rule.

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Goedecke, Andreas, and Randolf Mock. "Transient Friction Effects Due to Variable Normal Load in a Multi-Scale Asperity-Creep Friction Model." In STLE/ASME 2010 International Joint Tribology Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ijtc2010-41190.

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The study of multi-scale and fractal contact geometries holds many insights into the nature of surface contact. As a common feature of most fractal contact models, the presence of small-scale, plastically loaded asperities has emerged. The latter are, due to their loading close to the yield strength of the material, subject to creep deformation which is often held responsible for transient friction effect like dwell time- or velocity-dependent friction. In this paper, the transient behavior of friction under varying normal force will be studied in the framework of a multi-scale contact model with fractal input parameters. An advanced asperity creep model from previous research is used, yielding the time-dependent creep enlargement of the asperity contact area in response to arbitrary load transients.

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Kostenko, Yevgen, Henning Almstedt, Konstantin Naumenko, Stefan Linn, and Alfred Scholz. "Robust Methods for Creep Fatigue Analysis of Power Plant Components Under Cyclic Transient Thermal Loading." In ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-95680.

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The aim of this paper is to apply robust mechanisms-based material laws to the analysis of typical high-temperature power plant components during an idealized start-up, hold time and shut-down sequence under a moderate temperature gradient. Among others a robust constitutive model is discussed, which is able to reflect inelastic deformation, hardening/recovery, softening and damage processes at high temperature. The model is applied for a creep analysis of advanced 9–12%CrMoV heat resistant steels and calibrated in particular case against experimental data for 10%CrMoV steel type. For a steam temperature profile transient heat transfer analysis of an idealized steam turbine component is performed providing the temperature field. From the subsequent structural analysis with the inelastic constitutive model local stress and strain state variations are obtained. As an outcome a multi-axial thermo-mechanical fatigue (TMF) loading loop for one or several loading cycles can be generated. They serve as input for a fatigue life assessment based on the generalized damage accumulation rule, whose results come close to reality. In addition, the accuracy of a simplified method which allows a rapid estimation of notch stresses and strains using a notch assessment rule (NAR) [1] based on Neuber approach is examined.

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Qian, Cheng, Nikos Kargas, Cao Xiao, Lucas Glass, Nicholas Sidiropoulos, and Jimeng Sun. "Multi-version Tensor Completion for Time-delayed Spatio-temporal Data." In Thirtieth International Joint Conference on Artificial Intelligence {IJCAI-21}. California: International Joint Conferences on Artificial Intelligence Organization, 2021. http://dx.doi.org/10.24963/ijcai.2021/400.

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Real-world spatio-temporal data is often incomplete or inaccurate due to various data loading delays. For example, a location-disease-time tensor of case counts can have multiple delayed updates of recent temporal slices for some locations or diseases. Recovering such missing or noisy (under-reported) elements of the input tensor can be viewed as a generalized tensor completion problem. Existing tensor completion methods usually assume that i) missing elements are randomly distributed and ii) noise for each tensor element is i.i.d. zero-mean. Both assumptions can be violated for spatio-temporal tensor data. We often observe multiple versions of the input tensor with different under-reporting noise levels. The amount of noise can be time- or location-dependent as more updates are progressively introduced to the tensor. We model such dynamic data as a multi-version tensor with an extra tensor mode capturing the data updates. We propose a low-rank tensor model to predict the updates over time. We demonstrate that our method can accurately predict the ground-truth values of many real-world tensors. We obtain up to 27.2% lower root mean-squared-error compared to the best baseline method. Finally, we extend our method to track the tensor data over time, leading to significant computational savings.

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de Morais Teixeira, Giovanni, Radwan Hazime, John Draper, and Dewi Jones. "Random Vibration Fatigue: Frequency Domain Critical Plane Approaches." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-62607.

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Frequency domain analysis offers a very efficient method for the fatigue durability assessment of structures subjected to vibration loading. It also allows engineers to gain valuable insight into system behavior and characteristics that are not easily recognized in the time domain. With some reasonable assumptions, most importantly linearity and steady state behavior, the response of a structure in many engineering applications can be simply evaluated through the “scaling” of the input signal by the Frequency Response Functions (FRFs). In cases where the input is random or stochastic in nature additional assumptions are needed to assess the behavior of the system. Usually such cases assume a stationary and ergodic input signal with a zero mean Gaussian distribution. When making such assumptions the system is still characterized by its FRFs. However, since the input signal is random it can be best described by its Power Spectral Density (PSD). Furthermore, the system response (characterized by the stress tensor) can be evaluated by “scaling” the PSD of the input signal(s) by the magnitude squared of the stress FRFs. The linearity assumption also allows the evaluation of a system response due to multiple inputs through superposition principles. When using stress based fatigue (to assess the durability of a component or a structure) there are several damage evaluation methodologies that can be used. Traditionally, for time domain analysis the von Mises equivalent stress had been the methodology of choice. More recently critical plane search methods have gained popularity and have shown much better correlation with laboratory experiments and field failures, especially under multi-axial and non-proportional loading. Some of these methods have found their way into frequency domain analysis. This paper highlights the application of critical plane methods for the multi-axial fatigue assessment of engineering structures that are subjected to non-deterministic random vibration. A case study is presented to illustrate the process and shows how the proposed method works.

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Hansen, Anders Hedegaard, and Henrik C. Pedersen. "Reducing Fatigue Loading due to Pressure Shift in Discrete Fluid Power Force Systems." In 9th FPNI Ph.D. Symposium on Fluid Power. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/fpni2016-1506.

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Discrete Fluid Power Force Systems is one of the topologies gaining focus in the pursuit of lowering energy losses in fluid power transmission systems. The cylinder based Fluid Power Force System considered in this article is constructed with a multi-chamber cylinder, a number of constant pressure lines and a valve manifold. The valve manifold is used to control the connections between the cylinder chambers and the pressure lines and hereby the resulting force form the cylinder. The valve manifold is equipped with fast on/off valves. However, shifting between pressure lines may yield pressure oscillations in the cylinder chamber, especially for systems with long connections between the cylinder and the valve manifold. Hose pressure oscillations will induce oscillations in the produced piston force. Hence, pressure oscillations may increase the fatigue loading on systems employing a discrete fluid power force system. The current paper investigates the correlation between pressure oscillations in the cylinder chambers and valve flow in the manifold. Furthermore, the correlation between the pressure shifting time and the pressure overshoot is investigated. The study therefore focus on how to shape the valve flow in the manifold to reduce the added fatigue loads. A simple transmission line model is developed for the analysis. Two inputs are given in the Laplace domain and the time domain solution of the cylinder pressure to the given inputs are derived through inverse Laplace transformation. Based on the time domain solutions the pressure overshoot for various pressure shifting times is investigated. With the two input functions defined by the pressure shifting time, T, the main results of the current paper show the correlation between the minimum shifting time and the pressure overshoot in a given cylinder chamber with a given line connection.

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Wang, Xiaowei, and YeongAe Heo. "Artificial Neural Network Surrogate Modeling for Offshore Wind Turbines Under Multi-Hazards." In ASME 2022 41st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/omae2022-81048.

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Abstract Surrogate modeling of offshore wind turbines (OWTs) under multiple hazards such as wind, wave, and earthquakes provides an expedient path toward rapid risk assessment and management of these structures. This paper explores the applicability of artificial neural network (NN) for the surrogate modeling using a synthetic database based on finite element analyses of a typical OWT under combined loading conditions due to winds, waves, and earthquakes. A multi-layer NN with multiple output variables that can effectively capture the OWT’s multi-hazard behavior is developed. Considered input variables include peak ground accelerations, reference wind speeds, wave heights and periods, and damping ratios. A 5-fold-cross-validation-based optimization is conducted to identify the optimal number of hidden layers (N) and the associated optimal number of neurons in each layer (Q). It is found that N = 2 and Q = 12 are optimal for the OWT. The proposed NN model can evaluate the monopile maximum bending moment, and displacement/rotation at mudline with errors less than 30% in general.

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