Transient Response Analysis Research Articles

Transient response analysis of sandwich composite panel

In order to introduce a novel way relied on enhancing structural design as well as utilizing advanced material for protecting nonmetallic structures from detrimental impacts of transient thermal shock, this research analyzes the transient coupled thermo-elasticity response of the sandwich cylindrical panel with nanocomposite face-sheets strengthened with the functionally graded distributions of graphene-platelets affected by thermal shock loading. To determine the performance of the simply-supported system in the content of the time-altering stresses and deflections, the analytical solving approach, according to the broadly-known Navier technique, is applied to the governing equations developed on the bases of the exact theory of elasticity. It is considered that the internal surface of the panel is thermally isolated, while the outer surface is affected by thermal shock. The energy balance relation specified for this thermal boundary condition is solved to acquire the temperature gradient. Inverting the Laplace transform would be done with the aid of Dubner and Abates’ technique to designate time-history of displacements, shear stresses, and temperature distribution. The Halpin-Tsai micromechanics adjusted for nanocomposites is utilized to calculate thermoelastic properties of the nanocomposite face-sheets. The obtained numerical outcomes revealed the growth of the geometrical factor called mid-radius to thickness ratio leads to higher ultimate temperature and lower transverse shear stress.

Fire resistance of reinforced SHS T-joints considering gradient temperature effect under post-earthquake fire

The earthquake usually causes serious damage on the T-joints in structure, which may reduce its fire resistance. Moreover the gradient temperature distribution for reinforced SHS T-joints appears under a fire. Therefore it is very necessary to evaluate the fire resistance of reinforced SHS T-joint considering gradient temperature effect under post-earthquake fire (PEF). The objective of this paper is to investigate the fire resistance of earthquake-damaged doubler-plate reinforced SHS T-joints considering gradient temperature effect. A computation model was established and validated using the existing experimental results. The gradient-temperature field distribution against reinforced SHS T- joints was conducted by transient-response analysis method, then a parametric study was carried out using 30 established computation models involving following dimensionless parameters such as the width ratio of brace to chord (δ), diameter to thickness ratio of chord (ζ), wall thickness ratio of doubler-plate to chord (α), wall thickness ratio of brace to chord (ε), length ratio of doubler-plate to chord (ξ), ratio of chord length to chord width (φ), welding effect, damage variable (D~) and fire retardant coating thickness. The results demonstrated that damage variable and fire retardant coating thickness had a great influence on the fire resistance of doubler-plate reinforced SHS T-joints, the parameters δ, ζ and α had a major influence on reinforced SHS T-joints. The findings can provide data support and theoretical reference for the design, maintenance and reinforcement of such joints.

Publisher's Note: “Coupling analysis of transient aerodynamic and dynamic response of articulated heavy vehicles under crosswinds” [Phys. Fluids 34, 017106 (2022)

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Parameter Tuning of Sliding Mode Speed Controller of Induction Motor Drive Using Teaching-Learning Based Optimization Algorithm

The optimal settings of the Sliding Mode Controller for three-phase Induction Motor speed regulation are proposed in this paper using a Teaching-Learning Based Optimization Algorithm. It is a straightforward metaheuristic algorithm that simulates the teaching-learning processes in a classroom. Indirect Field Oriented Control is used in this induction motor drive, which allows the motor torque and the flux to be separated, similar to a DC motor. The inner loop uses proportional-integral current controllers, whereas the outside loop uses a sliding mode speed controller. In this paper, the sliding mode controller uses a tanh function as a switching function. Integral Time Absolute Error and Zwe-Lee Gaing's parameters are used as objective functions for tuning sliding mode controller settings. Performances of the proposed scheme in terms of the transient response analysis are compared with the swarm intelligence-based algorithms, namely the modified Particle Swarm Optimization and Grey Wolf Optimization. MATLAB/ SIMULINK software is used to build the three algorithms and sliding mode controller-based induction motor drive models, which are then analysed using simulation experiments. In comparison to the modified Particle Swarm Optimization and the Grey Wolf Optimization algorithms, Teaching-Learning Based Optimization yields the lowest value of the objective function Zwe-Lee Gaing's parameter and it converges quickly.

Rapid decoupling Laplace-domain algorithm for dynamic response estimation of offshore structures with asymmetric system matrices

The vibrating differential equation of offshore structures with asymmetric system matrices cannot be decoupled using normal or complex modes. The dynamic response analysis of offshore structures is employed only using the frequency-domain method or step-by-step integration method, owing to which we cannot avoid the limitations of those methods, such as relying the on calculation time step, low calculation efficiency, and steady-state response analysis. To address these problems, a Laplace-domain algorithm based on the poles and corresponding residues of a decoupled vibrating system and exciting wave force is proposed to deal with the dynamic response analysis of offshore structures with asymmetric system matrices. A theoretical improvement is that the vibrating equation with asymmetric system matrices is decoupled by the lower parts of the left and right eigenvectors, providing the possibility of solving the vibrating equation based on the decoupled equations. Meanwhile, this method analyzes the dynamic response of offshore structures in the Laplace domain, indicating that the proposed method is insensitive to the calculation time step and has a higher calculation accuracy. Considering that this algorithm can calculate the transient response caused by the initial conditions, the wave force can be divided into a series of small segments, and the dynamic response is connected by the initial conditions of the small segments, thereby considerably improving the computing efficiency of the dynamic response analysis. Three test cases were applied to evaluate the performance of the proposed algorithm. The results show that (1) the proposed algorithm can estimate the dynamic response of offshore structures with asymmetric system matrices both in the process of transient and steady-state response analysis; (2) the computational accuracy of the proposed algorithm is insensitive to the calculation time step, which has a more stable calculation result compared with the Newmark-β method; and (3) the proposed algorithm has a higher calculational efficiency owning to the transient analysis capability.

Pole-residue method for dynamic response analysis of floating structures depending on decoupled Cummins equation

This study proposes a new dynamic response estimation algorithm for floating structures based on the pole-residue method, which can be used to calculate the dynamic response induced by the wave force and the transient response created by initial conditions. The proposed algorithm deals with the Cummins equation in the Laplace domain, which can avoid the integral computation of the convolution items and the error accumulation problem in the process of numerical integration. One theoretical improvement is that the transfer function obtained by the Laplace transform is decoupled and the corresponding poles and residues are calculated. Consequently, the coupling system of the floating body and fluid is replaced with the calculated poles and residues, which greatly simplifies the procedure for dynamic response analysis. Furthermore, the method avoids the integral errors of the time-domain method and the application limits of the frequency-domain method, such as energy leakage, periodic hypothesis, and allowing only the stable response calculation. Three test cases were employed to evaluate the performance of the proposed algorithm. The first case is a single degree of freedom (SDOF) system in the form of the Cummins equation. The example shows the implementation procedure of the proposed algorithm in detail. The results demonstrate that the proposed algorithm is able to simulate the dynamic response of the SDOF system accurately, and that its calculation efficiency is better than that of the Newmark-β method. The second case is a spar-type floating offshore wind turbine. Studies show that the dynamic responses estimated by the proposed algorithm match well with those of the time-domain method both in the stable and transient response analysis, and that the proposed algorithm has a better calculation accuracy. The final case is a Floating Production Storage and Offloading unit (FPSO) model. The studies of the FPSO model indicate that the estimated dynamic response obtained applying the proposed algorithm agrees well with that of the WASIM codes of SESAM, which further proves the validity of the proposed algorithm.

Machine Learning Methods to Investigate Drug Delivery in Infusion Pump

In the current scenario, usage of the smart medical pump is predominant in the medical field. The precise drug dosage, flow accuracy should be maintained to increase the performance of an infusion pump. In this work, an attempt has been made to predict and control the speed of the infusion pump for suitable infusion flowrate using machine learning technique and Linear Quadratic Gaussian (LQG) controller. The data for this study is considered from the publicly available online database, electronic Medicines Compendium (eMC). The speed of the infusion pump has been calculated using the drug dosage and flow rate for two different drugs. The prediction of infusion pump speed is achieved using Linear regression with Principal Component analysis (PCR) and Support Vector Machine Regression (SVR). The performance of the prediction schemes is evaluated using standard metrics. To validate the optimal control of the predicted speed, two different medical graded motors are considered. Further, the optimal control of the pump speed is investigated using Proportional–Integral–Derivative (PID), Linear Quadratic Regulator (LQR), and LQG controllers for its stability criteria. The prediction of the pump speed using regression models PCR, SVR has been verified and then the transient response analysis with rise time, settling time for both the motors have been examined. Results demonstrate that the LQG optimal control strategy achieves fast rise time, settling time of motor1 with 0.653s, 1.15s, and 0.22, 0.392s for motor2 respectively.

Rotor Design, Analysis and Experimental Validation of a High-Speed Permanent Magnet Synchronous Motor for Electric Turbocharger

We developed a high-speed surface mounted permanent magnet synchronous motor (SPMSM) and a pulse width modulation (PWM)-driven inverter for a turbocharger with an additional electrically driven compressor (TEDC). These systems operate at 70 000 rpm and are intended to fit 1.6-L diesel vehicles to reduce turbo lag to within 0.4 s. There are key issues in the design of rotors for SPM type machines. To prevent the PM from scattering during high-speed operation, a retaining sleeve is necessary in the rotor. Several studies have reported on rotor design and the effect of retaining sleeve materials, but no papers have applied appropriate modeling and analysis to composite material sleeves. In this study, a specialized tool was used to obtain accurate results for a composite material sleeve. The results of theoretical analyses and finite element analyses (FEA) of rotors with metallic and composite sleeves were compared, considering various stress sources such as interference fit, centrifugal force and temperature gradient. In addition, rotor dynamics and transient response analyses were performed using the proposed models to verify structural stability and response time. The proposed rotor was assembled with the stator and tested in connection with the 1.6-L diesel engine. It was confirmed that the transient acceleration performance was improved by 49.14%.

Coupling analysis of transient aerodynamic and dynamic response of articulated heavy vehicles under crosswinds

Vehicle aerodynamics and dynamics in gusty crosswind conditions are of increasing significance for the lateral stability of heavy ground vehicles, especially articulated heavy vehicles (AHVs). The unsteady aerodynamic loads acting on AHVs can greatly exceed loads of a single-vehicle unit; these may deteriorate the lateral stability and lead to a loss of handling control. In this study, the time characteristics of aerodynamic loads and dynamic response of a tractor semi-trailer were considered, based on simulating the relative motions of these two components to reproduce actual scenarios of AHVs in crosswinds. A dynamic fully coupled method was developed and adopted to realize a real-time data exchange of flow fields and multi-bodies. Two multi-body systems (for non-articulated heavy vehicles and AHVs, respectively) were created to study the influences of the relative motions on the aerodynamic performance and lateral stability of the vehicles. The Reynolds-averaged Navier–Stokes (RANS) method and renormalization group (RNG) k−ε equation were adopted to account for the turbulence. A wind tunnel experiment was conducted to validate the numerical method. The results show that AHVs are more sensitive to the crosswind, with significant differences in the magnitudes and directions of the aerodynamic forces, moments, dynamic yaw angle, and lateral displacement. Three different wind types were considered (step, linear, and sinusoidal). The step crosswind produces the largest average lateral force and yawing moment, resulting in the largest lateral displacement and yaw angle. The largest hitch angle is found for linear gusts, presenting the highest safety risks in regard to jackknifing and trailer swings.

Modelling, performance assessment and transient analysis of brushless DC motor by controller techniques

This paper investigates steady state and transients' performance of Brushless Direct Current Motor (BLDC) motor and collates the performance of Proportional Integral (PI) and Proportional Integral Derivative (PID) Controller. Speed and torque behavior is most valuable nowadays for home appliance and other applications. The torque in motor is produced with effect of magnetic field and current. Magnetic field is generated in motor by the strong permanent magnet, and motor current depends upon voltage control and Eb, which is done by field and speed motor. In order to obtain required torque and speed at a particular load, current required must be controlled. The transient or dynamic response analysis is done with transfer function of BLDC motor obtained by the Laplace transform of equivalent circuit equation. The trapezoidal type BLDC machine is controlled using 3-phase Inverter Bridge. The commutation sequence is done with hall sensor and gate pulses. The simulation work is done in MATLAB/ Simulink software and mathematical model is evaluated. The analysis is done to know the performance of how quickly the transient reduces and gives smooth operation for various applications.

Transient response analysis of nonlinear oscillators excited by Gaussian white noise using complex fractional moments

An approximate analytical method based on complex fractional moments (CFMs) is proposed to obtain the transient response probability density function of a dynamic system with nonlinearity in both stiffness and damping excited by Gaussian white noise. The CFM is a new kind of statistical moment developed in recent years and is related to the Mellin transform of a probability density function. In the proposed method, first, the system response is expressed in the form of quasi-harmonic oscillation with amplitude and phase variables, and then, the equivalent natural frequency of the system, which is given as a function of the amplitude, is determined by the equivalent linearization method. Next, using the equivalent natural frequency and the stochastic averaging procedure, the Fokker-Planck equation governing the probability density of the response amplitude is derived. The Mellin transform of the Fokker-Planck equation yields the governing equations of the amplitude CFMs, which are given by simultaneous linear ordinary differential equations. Finally, the inverse Mellin transform of the CFMs obtained from the differential equations leads to the transient response probability density function. In numerical examples, two types of nonlinear stochastic oscillators are considered. The analytical results of the transient response probability densities obtained by the proposed method are in good agreement with the corresponding Monte Carlo simulation results, including their tail region.

Electrical and butanone sensing study of titania thin film transistor

In this paper, titanium dioxide thin film transistor (TFT) is reported to detect 2-butanone at room temperature. The titanium dioxide (TiO2) is prepared by sol–gel method and deposited on p-Si (100) substrate by dip coating method. The gold (Au) deposited over sensing layer to form source and drain whereas titanium (Ti) metal is deposited at the bottom of p-Si substrate to act as back gate. Titanium tetrachloride (TiCl4) is used as precursor for the preparation of TiO2. The FESEM and AFM characterization of thin film is carried out to investigate the morphology and surface roughness. The average roughness, root mean square roughness of surface is found to be 30.18 nm and 38.5 nm, respectively. The transient response analysis for 5 ppm concentration of butanone reveals that the maximum response magnitude is 60%. The response/recovery time are found to be 61 s and 160 s respectively.

Wind generator transient response analysis and improvement using BESS

Transient stability is very important for safety in the power system. In this paper, transient stability analysis of a wind power generator connected to distribution network is presented. The analysis was performed on a model of a realistic 12-bus system. In order to improve transient response capabilities of the system, battery energy storage system (BESS) is included in the simulations. It was demonstrated that BESS has significant influence on the stability of the network during the fault conditions. All simulations were performed in the DigSILENT Power Factory software. The analysis and assessment of the network was performed for the case of three-phase symmetrical fault with all lines in service and following a single line outage (failure and N-1 criterion). The results show that the connection of the wind generators to distribution network depends on the distance from the primary source of the grid (slack bus). However, BESS system can be used to improve transient stability response in which case distance from the primary source station is not critical. Also, this analysis adds additional evidence on the importance of transient stability calculations during the process of new generator unit connection to the power system.

Accurate Interpolation of the Dependency of Modal Properties on the Rotation Speed for the Transient Response Analysis of Bladed Disks

Abstract During fast gas-turbine engine acceleration and deceleration, the transient vibration effects in bladed disk vibration become significant and the transient response needs to be calculated. In this paper, an effective method is developed for efficient calculations of the transient vibration response for mistuned bladed disks under varying rotation speeds. The method uses the large-scale finite element modeling of the bladed disks allowing the accurate description of the dynamic properties of the mistuned bladed disks. The effects of the varying rotation speed on the natural frequencies and mode shapes of a mistuned bladed disk and its effects on the amplitude and the spectral composition of the loading are considered. The dependency of the modal characteristics on the rotation speed is based on the evaluation of these characteristics at reference points followed by the interpolation to obtain values at any rotation speed from the operating range. A new method has been developed for the interpolation of mode shapes while preserving the orthogonality and mass normalization of the mode shapes. The method of mode shape interpolation is elaborated for tuned and mistuned bladed disks. The accuracy and efficiency of the method are demonstrated on test examples and on analysis of transient forced response of realistic bladed disks.

Transient Response of a Hollow Functionally Graded Piezoelectric Cylinder Subjected to Coupled Hygrothermal Loading

In this paper, transient response of a simply supported finite length hollow cylinder made of functionally graded piezoelectric material (FGPM) subjected to coupled hygrothermal loading was investigated. The coupled equations of heat conduction and moisture diffusion as well as motion equations and the electrostatic equation of FGPM were solved employing the Fourier series expansion method through the longitudinal direction, the differential quadrature method (DQM) along the radius and Newmark method for time domain. Finally, the distribution of temperature, humidity, electric potential, stresses and displacements was achieved. The effect of coupled and uncoupled hygrothermal loading, grading index and hygrothermal loading was illustrated in the numerical examples. The results show that using the coupled model is vital for analysis of transient response of the cylinder subjected to hygrothermal loading.

In situ construction of 0D CoWO4 modified 1D Mn0.47Cd0.53S for boosted visible-light photocatalytic H2 activity and photostability

To enhance the photocatalytic activity, loading proper semiconductor with high efficiency and low cost is one of the most valid approaches. Herein, various amounts of CoWO4 as a novel metal-free material were loaded on Mn0.47Cd0.53S (MCS) nanorods for photocatalytic hydrogen production reaction. The CoWO4/Mn0.47Cd0.53S-25 (CW/MCS-25) exhibits the highest hydrogen production rate of 41.53 mmol·h−1·g−1 in the Na2S/Na2SO3 system, which is about 2.68 times higher than that of pristine MCS. The Mapping and HRTEM reveals the deposited of CoWO4 on the MCS. The detailed analyses of XPS, EIS, TRPL spectra and transient photocurrent responses indicate that CoWO4 and MCS interacted closely and the photogenerated electrons of CoWO4 can be transferred into MCS. In particular, the introduction of CoWO4 can further transfer the photogenerated holes of MCS, thereby inhibiting the photocorrosion of MCS and improving photocatalytic activity. This work provides a reference for the exploration of noble metal-free composite material and shows great potential in the photocatalytic application.

Transient response analysis of FG-CNTRC curved composite panel under multi-directional initially stresses resting on nonpolonomial elastic foundation

Due to importance of exploring novel ways to protect systems from detrimental influences of thermal shock phenomenon, this study aims at analyzing the transient coupled poro/thermoelasticity response of functionally graded CNT reinforced (FG-CNTR) nanocomposite panels surrounded by non-polynomial kind of elastic foundation. In addition to thermal shock, the mentioned nanocomposite structure is subjected to initial mechanical loads in different orientations. As the accuracy of the results is of high prominence to guarantee reliability of the practical designs, the governing equations are developed on the basis of the exact type of elasticity theory known as three-dimensional form. Also, analytical solution is determined by applying Navier approach to solve the governing differential equations for simply-supported boundaries. Energy balance equation is utilized to determine the temperature gradient of the cylindrical panel considering the assumptions that the internal surface is fully isolated and the external one is subjected to thermal shock loading. Modified type of Dunber and Abate’s approach is implemented to inverse the Laplace transform in order to map the response of the system from Laplace into time domain. Convergence of the determined deflection, shear stresses, and temperature versus passing time is analyzed and confirmed. The acquired numerical results elucidate the role of different factors such as mid-radius to thickness ratio, volume-fraction, and scattering pattern of CNT in the transient coupled poro/thermoelasticity response of the FG-CNTR nanocomposite cylindrical panel. As a valuable result, it is found that increasing the volume-fraction of CNT applies negative impacts on the variation of the transverse shear stress.

Simulation, modeling, and experimental verification of moving column precision grinding machine

ABSTRACT Grinding is the final step in machine tool processing; it affects the accuracy and surface roughness of the machined parts. This study aims to improve the static and dynamic performance of precision grinding machines and reduce their deformation and avoid resonance. Based on the static characteristic analysis, the maximum deformation of the spindle head was determined to be 134 μm, which was reduced to 40 μm by applying a counterweight to the design. The first two modal frequencies obtained from the modal analysis were 26.9 and 27.7 Hz. The vibration of the second mode directly affected the processing accuracy of the machine. The vibration frequency and vibration modes of the structure were verified using the simulation results. These experiments and simulations helped improve the performance of the precision grinding machines. A transient response analysis method was implemented to investigate the influence of applied force during the simulation process, and experiments were conducted to evaluate the performance of the machine. As the saddle was increased by 200 mm, the modal frequency of the machine increased by 26% and reached 35.0 Hz. Our redesigning helped increase the modal frequency and avoid resonance at 30 Hz.

Aggregated Model of Virtual Power Plants for Transient Frequency and Voltage Stability Analysis

The Virtual Power Plant (VPP) has been proposed to aggregate Distributed Generations (DGs) to act like a single power plant, thus, also has functions on the frequency and voltage support. The previous models of the VPP are static and focus on the energy trading and management. For the system transient response analysis, a dynamic VPP model must be needed. The paper proposes a reduced-order yet accurate aggregated model to represent VPP transients for the stability analysis of power systems. The goal is to provide a model that is adequate for system studies and can serve to the Transmission System Operator (TSO) to evaluate the impact of VPPs on the overall grid. The proposed model can accommodate the transient response of the most relevant controllers included in the distributed generators that compose the VPP. Using a comparison with a real-time detailed Electro-Magnetic Transients (EMT) models of the VPP confirms the validity of the proposed aggregated model. The case studies based on the IEEE 39-bus system verifies the accuracy of the proposed aggregated model on the system stability analysis.

Pitfalls for transient response analysis with VF-TLP

Analyzing transient ESD device behavior with TLP equipment requires more attention for implementation and measurement details than the classical quasi-static TLP approach. Minimizing hardware parasitics reduces the de-embedding effort and optimizes the quality of the voltage and current measurements. We explore different methods and hardware options and highlight potential pitfalls.