Two-way Coupled Analysis Research Articles

Electromechanical model and simple numerical analysis for a piezoelectric vibration energy harvester considering nonlinear piezoelectricity, nonlinear damping, and self-powered synchronized switch circuit

Establishment of an analytical technique that considers nonlinear piezoelectricity, nonlinear damping, and the connections to the self-powered synchronized switch circuit represents a challenging but practical issue in the development of piezoelectric vibration energy harvesters. The two-way coupled analysis method, which combines numerical software with a circuit simulator, can simulate the performance of the harvester, but it imposes a high computational load. We develop a numerical analysis technique that is more readily implemented to allow us to produce accurate predictions of the output power, displacement, and frequency response characteristics of this harvester with the switch circuit. First, we derive the electromechanical equation required for the miniature harvester, and we then determine the parameters in this equation using the harmonic balance method. Finally, the governing equation coupling the piezoelectric vibration energy harvester with the self-powered synchronized switch circuit is simplified, taking the form of a quartic equation with respect to the displacement. The simulation replicated a reduction in the displacement at higher resistive loads, wider variations in the resonance frequency, and the nonlinear stiffness softening characteristics that were observed experimentally. This paper provides a practical method for predicting the performance of the nonlinear piezoelectric vibration energy harvester with the synchronized switch circuit.

A Novel Thermal Analysis Method Based on a Multi-Physics Two-Way Coupled Method and Its Application to Submersible Permanent Magnet Synchronous Motors

As a submersible permanent magnet synchronous motor (SPMSM) must function in downhole high temperature crude oil for long periods of time, the accurate prediction of its temperature rise is crucial to improve the stability of the motor. However, the analysis of its temperature field involves multiple physical fields, such as the electric field, the magnetic field, the fluid field and so on, and it is difficult to calculate accurately. Motor loss is usually loaded as a fixed value when calculating the temperature field, while in reality, the loss always changes with temperature. Therefore, the calculation of temperature is inaccurate using this one-way coupled method. In this paper, the relationship between loss and temperature is investigated and an electromagnetic-thermal fluid multi-physics two-way coupled analysis method suitable for SPMSM is proposed. The loss can be loaded as a variable by this new two-way coupled method, which significantly improves the temperature calculation accuracy. In order to prove the feasibility of the two-way coupled method, experiments based of a prototype of high torque and low speed SPMSM and cavity pump are conducted with the fiber Bragg grating (FBG) sensor measuring SPMSM temperature. Finally, the multi-physics two-way coupled method proposed in this paper is proven to be rational and feasible in the analysis of the SPMSM temperature rise.

Numerical Analysis of Laser Pattern Effects to Residual Stress on Metal 3D Printing

In this study, a metal 3D printing process was simulated using finite elements methods (FEM), and the specimens were printed under the same conditions. Subsequently, residual stress was measured to validate the results. The thermal-structure two-way coupled analysis confirmed the phenomenon that occurred during the additive process, thereby allowing the residual stress to be calculated more realistically. In addition, to simulate the printing process, a subroutine was configured to account for the laser heat input path and layer. The process of stacking and hatching in a snake pattern for an area measuring 5 mm × 5 mm was simulated. Four cases with different rotation angles of the layer pattern were calculated using FEM. The specimens were printed compared with the analysis results. To verify the printed condition of the specimen, computed tomography was performed to confirm the appearance of pores and cracks in the specimen. Cracks appeared in the 180° specimen, and the cause was analyzed based on the analysis results. Subsequently, the residual stress was measured by an X-ray diffractometer and compared; it was confirmed that the average error of the specimen without cracks is 8.86%, which is similar to the analysis results. These results confirm that the FEM model conducted in this study can be used to analyze residual stress and cracks in a material, which are difficult to analyze in previous studies. The FEM model constructed in this study is expected to facilitate investigations into 3D printing phenomena as well as enable a more efficient process design.

Coupled Finite Element-Finite Volume Multi-Physics Analysis of MEMS Electrothermal Actuators.

Microelectromechanical systems (MEMS) are the instruments of choice for high-precision manipulation and sensing processes at the microscale. They are, therefore, a subject of interest in many leading industrial and academic research sectors owing to their superior potential in applications requiring extreme precision, as well as in their use as a scalable device. Certain applications tend to require a MEMS device to function with low operational temperatures, as well as within fully immersed conditions in various media and with different flow parameters. This study made use of a V-shaped electrothermal actuator to demonstrate a novel, state-of-the-art numerical methodology with a two-way coupled analysis. This methodology included the effects of fluid–structure interaction between the MEMS device and its surrounding fluid and may be used by MEMS design engineers and analysts at the design stages of their devices for a more robust product. Throughout this study, a thermal–electric finite element model was strongly coupled to a finite volume model to incorporate the spatially varying cooling effects of the surrounding fluid (still air) onto the V-shaped electrothermal device during steady-state operation. The methodology was compared to already established and accepted analysis methods for MEMS electrothermal actuators in still air. The maximum device temperatures for input voltages ranging from 0 V to 10 V were assessed. During the postprocessing routine of the two-way electrothermal actuator coupled analysis, a spatially-varying heat transfer coefficient was evident, the magnitude of which was orders of magnitude larger than what is typically applied to macro-objects operating in similar environmental conditions. The latter phenomenon was correlated with similar findings in the literature.

열-구조 연계 수치해석을 통한 금속 3D Printing 적층 해석

The development in three-dimensional (3D) printing technology or additive manufacturing has provided a superior alternative to existing casting methods. However, the distortion and cracking due to residual stress and the direct measurement of the 3D printing process pose major challenges. Therefore, the finite element method (FEM) analysis was used to confirm changes in the variables having a major influence on the quality. The process of melting and solidification of the powder using a laser was simulated by constructing a thermal-structure two-way coupled analysis. The heat transfer and residual stress were confirmed to be produced by the laser heat input. Subsequently, the analysis model was verified by confirming that a phenomenon similar to the analysis occurred with the 3D printing specimen. Using this study, the residual stress and distortion are expected to be minimized while improving the production efficiency of 3D printing.

Two-Way Coupled Shooting Analysis of Fluid Force in the Annular Plain Seal and Vibration of the Rotor System

Abstract In turbomachinery, the rotor dynamic (RD) fluid force generated in a fluid element, by the interaction between the shaft behavior and the fluid flow, is one of the causes of the shaft behavior and has a great influence on the stability of the turbomachinery. In order to improve the reliability of turbomachinery, it is important to analyze the dynamical behavior considering the mutual influence of the RD fluid force and shaft motion. In this paper, the two-way coupled analysis between the fluid force in the annular plain seal and the vibration of the rotor system was expanded by introducing the shooting method in it. The frequency response was obtained, and the onset speed of instability (OSI) was predicted effectively. The influence of parameters on the OSI was investigated and discussed. Then, the numerical results obtained by this two-way coupled shooting analysis was compared with the experimental results and the validity of the analysis was confirmed. The influence of disturbance on the error of predicted OSI was also discussed. The transition region to instability was introduced for the predicted OSI using the spectral radius, and the error between the numerical and experimental results of the OSI was explained. As a result, the two-way coupled shooting analysis can predict the OSI values in various situations of two-way coupled system more effectively than the direct numerical simulation. Also, the robustness of stability for the predicted OSI can be evaluated simultaneously by investigating the spectral radius and defining the transition region to instability appropriately.

光纤布拉格光栅传感器应变传递双向耦合分析

光纤布拉格光栅传感器应变传递双向耦合分析

Sand Suction Characteristics in the Rear Side of a Revetment Using DEM-WASS-2D

Hur, D.S.; Cho, W.C.; Lee, J.L., and Jeong, Y.M., 2019. Sand suction characteristics in the rear side of a revetment using DEM-WASS-2D. In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 66-70. Coconut Creek (Florida), ISSN 0749-0208.The coupled analysis of a particle method and a wave field model was conducted to examine numerically the characteristics of sand behaviors at the bottom and in the rear side of a revetment. The two-way coupled analysis used in this study can not only consider the interaction among the wave, revetment, and ground but also represent sand behaviors at the bottom and in the rear side of a revetment under waves. The validity and usefulness of the two-way coupled analysis was ensured by comparing hydraulic characteristics around an impermeable revetment with the results of a hydraulic model experiment. In the coupled analysis, characteristics of sand behaviors at the bottom and in the rear side of a revetment were numerically analyzed according to the installation of an incident wave and submerged breakwater. As the wave energy increased, the sand transport from the bottom of the revetment also increased. The transport rates of sand from the bottom of the revetment to the open sea decreased by 14-93% when a submerged breakwater was installed under the tidal condition of this study. In addition, the two-way coupled analysis was also effective in numerically examining the stability of the bottom and rear side of a revetment according to the characteristics of sand behaviors.

Two-way coupled analysis of lithium diffusion and diffusion induced finite elastoplastic bending of bilayer electrodes in lithium-ion batteries

A fully coupling model for the diffusion induced finite elastoplastic bending of bilayer electrodes in lithium-ion batteries is proposed. The effect of the mechanical stress on the lithium diffusion is accounted for by the mechanical part of the chemical potential derived from the Gibbs free energy along with the logarithmic stress and strain. Eight dimensionless parameters, governing the stress-assisted diffusion and the diffusion induced elastoplastic bending, are identified. It is found that the finite plasticity starting from the interface of the bilayer increases the chemical potential gradient and thereby facilitates the lithium diffusion. The full plastic flow makes the abnormal lithium concentration distribution possible, i.e., the concentration at the lithium inlet can be lower than the concentration at the interface (downstream). The increase in the thickness of the active layer during charging is much larger than the eigen-stretch due to lithiation, and this excess thickening is found to be caused by the lithiation induced plastic yield.

Coupled Analysis of Thermo-Fluid-Flexible Multi-body Dynamics of a Two-Dimensional Engine Nozzle

Various components of an engine nozzle are modeled as flexible multi-body components that are operated under high temperature and pressure. In this paper, in order to predict complex behavior of an engine nozzle, thermo-fluid-flexible multibody dynamics coupled analysis framework was developed. Temperature and pressure on the nozzle wall were obtained by the steady-state flow analysis for a two-dimensional nozzle. The pressure and temperature-dependent material properties were delivered to the flexible multi-body dynamics analysis. Then the deflection and strain distribution for a nozzle configuration was obtained. Heat conduction and thermal analyses were done using MSC.NASTRAN. The present framework was validated for a simple nozzle configuration by using a one-way coupled analysis. A two-way coupled analysis was also performed for the simple nozzle with an arbitrary joint clearance, and an asymmetric flow was observed. Finally, the total strain result for a realistic nozzle configuration was obtained using the one-way and two-way coupled analyses.

Comparison of one-way and two-way coupled analyses of electromagnetic machines considering magnetic and structural interactions

We compared one-way and two-way coupled analyses of electromagnetic machines considering magnetic and structural interaction to identify the frequency components of magnetic excitation and to determine the structural coupling effects predicted only by the two-way coupled analysis. We developed finite element models of a C-core switch and an electric motor. In the two-way coupled analysis method, the magnetic force calculated by using the Maxwell stress tensor was applied to the structural finite element model to determine the elastic deformation, and the magnetic finite element model was rearranged by means of the moving mesh method to represent the structural elastic deformation. We showed that two-way coupled analysis predicted the excitation frequency of 80 Hz (4 times the input current frequency) of magnetic force in the C-core switch and the excitation frequency of 667 Hz (the first natural frequency of the rotor, corresponding to the translational mode) of magnetic force in the electric motor undergoing rotor eccentricity. We showed that two-way coupled analysis predicted magnetic excitation and its corresponding structural response more accurately than the one-way coupled analysis, especially for electromagnetic machines in which the structural deformation affects magnetic field through variation of the air gap length.

Robust Fully-Implicit Coupled Multiphase-Flow and Geomechanics Simulation

SummaryMaterial nonlinearity, boundary and arching constraints, nonuniform reservoir flows, sliding along material interfaces, or faults are among the causes of shear deformation or changes in the total stresses and the resulting stress redistribution in hydrocarbon reservoirs. Previous studies have demonstrated that shear or nonuniform deformation and stress redistribution in subsurface formations may have significant effects on reservoir fluid flows. Thus, a two-way coupled analysis is the required approach under circumstances where the shear deformation or changes in total stresses in the reservoir cannot be neglected.A coupled multiphysics simulator is developed for the dynamic modeling of multiphase thermal/compositional flow, and poroelastoplastic geomechanical deformation. The equations that govern multiphase flow in permeable media, heat transport, and poroelastoplastic geomechanics together lead to a highly nonlinear system. Finite-volume and Galerkin finite-element methods are used for the numerical solution of thermal/compositional multiphase fluid-flow and geomechanics equations on general hexahedral grids, respectively. Because of its improved stability and rapid convergence characteristics, the resulting multiphysics system of equations is solved with a fully-implicit formulation by use of an effective implementation of the Newton-Raphson method in the default mode.The coupled simulator is by design maximally modular with self-contained flow and geomechanics modules that can be operated in a two-way coupled mode with explicit-, iterative-, and fully-implicit-coupling options. The coupled-modeling system lends itself naturally not only to near-wellbore coupled flow and geomechanical deformation problems where poroplasticity may play a more prominent role, but also to reservoir-scale simulations where both poroelasticity and poroplasticity are relevant. The coupled simulator is validated against analytical solutions for simple cases, by use of published data in the open literature. Validation results demonstrate the robust, fast, and accurate predictive capabilities of the multiphysics modeling protocol.