Examinando por Materia "Time domain analysis"
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Ítem Computational characterization of the wave propagation behavior of multi-stable periodic cellular materials(Elsevier Limited, 2019-01-01) Valencia, Camilo Andres; Restrepo D.; Mankame N.D.; Zavattieri P.D.; Gomez, Juan David; Mecánica AplicadaIn this work, we present a computational analysis of the planar wave propagation behavior of a one-dimensional periodic multi-stable cellular material. Wave propagation in these materials is interesting because they combine the ability of periodic cellular materials to exhibit stop and pass bands with the ability to dissipate energy through cell-level elastic instabilities. Here, we use Bloch periodic boundary conditions to compute the dispersion curves and introduce a new approach for computing wide band directionality plots. Also, we deconstruct the wave propagation behavior of this material to identify the contributions from its various structural elements by progressively building the unit cell, structural element by element, from a simple, homogeneous, isotropic primitive. Direct integration time domain analyses of a representative volume element at a few salient frequencies in the stop and pass bands are used to confirm the existence of partial band gaps in the response of the cellular material. Insights gained from the above analyses are then used to explore modifications of the unit cell that allow the user to tune the band gaps in the response of the material. We show that this material behaves like a locally resonant material that exhibits low frequency band gaps for small amplitude planar waves. Moreover, modulating the geometry or material of the central bar in the unit cell provides a path to adjust the position of the band gaps in the material response. Also, our results show that the material exhibits highly anisotropic wave propagation behavior that stems from the anisotropy in its mechanical structure. Notably, we found that unlike other multi-stable cellular materials reported in the literature, in the system studied in this work, the configurational changes in the unit cell corresponding to its different stable phases do not significantly alter the wave propagation behavior of the material. © 2019Ítem Determination of the technical state of suspension elements based on the OMA-LSCE method(Collegio Ingegneri Ferroviari Italiani, 2012-01-01) Castañeda, L.; Martinod, R.; Betancur, G.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Estudios en Mantenimiento (GEMI)A study is established regarding the behavior of the vehicle under the influence of the damping elements, proposing a methodology for the validation of the technical state of the dampers through the registration of dynamic variables under commercial operating conditions of the vehicle, by applying the Operational Modal Analysis COMA) technique via Least-Square Complex Exponential (LSCE) method to experimental tests and numeric simulations to a multi-body system (MBS) model. The OMA-LSCE method is applied to the signals acquired during a test performed on a passenger of a three- car unit in typical commercial travel operation. From the signals in time domain of each section of the segment, the respective discrete function PSD is calculated. Once the model is defined, a set of numeric simulation is executed according to the design of the experiment. The results of the numeric simulations show that the natural frequency generates a lineal regressive model with correlation coefficient values.Ítem Determinazione dello stato tecnico degli elementi delle sospensioni sulla base del metodo OMA-LSCE(Collegio Ingegneri Ferroviari Italiani, 2012-01-01) Castañeda, L.; Martinod, R.; Betancur, G.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Estudios en Mantenimiento (GEMI)A study is established regarding the behavior of the vehicle under the influence of the damping elements, proposing a methodology for the validation of the technical state of the dampers through the registration of dynamic variables under commercial operating conditions of the vehicle, by applying the Operational Modal Analysis COMA) technique via Least-Square Complex Exponential (LSCE) method to experimental tests and numeric simulations to a multi-body system (MBS) model. The OMA-LSCE method is applied to the signals acquired during a test performed on a passenger of a three- car unit in typical commercial travel operation. From the signals in time domain of each section of the segment, the respective discrete function PSD is calculated. Once the model is defined, a set of numeric simulation is executed according to the design of the experiment. The results of the numeric simulations show that the natural frequency generates a lineal regressive model with correlation coefficient values.Ítem Frequency-domain analytic method for efficient thermal simulation under curved trajectories laser heating(Elsevier BV, 2019-01-01) Mejia-Parra D.; Moreno A.; Posada J.; Ruiz-Salguero O.; Barandiaran I.; Poza J.C.; Chopitea R.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEIn the context of Computer Simulation, the problem of heat transfer analysis of thin plate laser heating is relevant for downstream simulations of machining processes. Alternatives to address the problem include (i) numerical methods, which require unaffordable time and storage computing resources even for very small domains, (ii) analytical methods, which are less expensive but are limited to simple geometries, straight trajectories and do not account for material non-linearities or convective cooling. This manuscript presents a parallel efficient analytic method to determine, in a thin plate under convective cooling, the transient temperature field resulting from application of a laser spot following a curved trajectory. Convergence of both FEA (Finite Element Analysis) and the analytic approaches for a small planar plate is presented, estimating a maximum relative error for the analytic approach below 3.5% at the laser spot. Measured computing times evidence superior efficiency of the analytic approach w.r.t. FEA. A study case, with the analytic solution, for a large spatial and time domain (1m×1m and 12s history, respectively) is presented. This case is not tractable with FEA, where domains larger than 0.05m×0.05m and 2s require high amounts of computing time and storage. © 2019 International Association for Mathematics and Computers in Simulation (IMACS)