Steady-state Dynamic Analysis Research Articles

Dual-Mode Ce-MOF Nanozymes for Rapid and Selective Detection of Hydrogen Sulfide in Aquatic Products.

Increasing concern over the safety of consumable products, particularly aquatic products, due to freshness issues, has become a pressing issue. Therefore, ensuring the quality and safety of aquatic products is paramount. To address this, a dual-mode colorimetric-fluorescence sensor utilizing Ce-MOF as a mimic peroxidase to detect H2S was developed. Ce-MOF was prepared by a conventional solvothermal synthesis method. Ce-MOF catalyzed the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by hydrogen peroxide (H2O2) to produce blue oxidized TMB (oxTMB). When dissolved, hydrogen sulfide (H2S) was present in the solution, and it inhibited the catalytic effect of Ce-MOF and caused the color of the solution to fade from blue to colorless. This change provided an intuitive indication for the detection of H2S. Through steady-state dynamic analysis, the working mechanism of this sensor was elucidated. The sensor exhibited pronounced color changes from blue to colorless, accompanied by a shift in fluorescence from none to light blue. Additionally, UV-vis absorption demonstrated a linear correlation with the H2S concentration, ranging from 200 to 2300 µM, with high sensitivity (limit of detection, LOD = 0.262 μM). Fluorescence intensity also showed a linear correlation, ranging from 16 to 320 µM, with high selectivity and sensitivity (LOD = 0.156 μM). These results underscore the sensor's effectiveness in detecting H2S. Furthermore, the sensor enhanced the accuracy of H2S detection and fulfilled the requirements for assessing food freshness and safety.

Dynamic Characteristics of M-Shape Metal Rubber-Coated Pipeline System: Numerical Modeling and Experimental Analysis

As a high-temperature resistant damping material, reducing vibration by coating with M-shape metal rubber (MMR) in a pipeline system is a promising solution due to its energy dissipation induced by micro dry friction between metallic wires. The main challenge for dynamic calculation and performance evaluation of elastic-porous metal rubber (MR) is derived from the intricate spatial network structure. In this work, the dynamic properties including acceleration admittance and insertion loss of the MMR-coated pipeline system were conducted by numerical simulation and experimental analysis. The constitutive models used to characterize hysteresis phenomena, including Yeoh and Bergström–Boyce models, were identified with different density parameters and adopted for steady-state dynamic numerical analysis. The sine sweep frequency test was conducted to verify the accuracy of the developed numerical model. The results indicate that the maximum error of stress–strain curve between numerical prediction and experimental measurement is 10.7%. In the frequency range of 0–1 500[Formula: see text]Hz, the insertion loss of the MMR-coated pipeline system is positively correlated with the density of MMR, as opposed to the coating distance of pipeline clamps and the influence of excitation force is minimal. Furthermore, the error of dynamic response of the pipeline system in low frequency between the experiment and simulation is 4.7%, indicating that the accuracy of the hysteresis model in predicting the dynamic characteristic of MR materials is effective.

Non-Doped Blue AIEgen-Based OLED with EQE Approaching 10.3 .

Aggregation-induced emission (AIE) luminogens (AIEgens) are attractive for the construction of non-doped blue organic light-emitting diodes (OLEDs) owning to their high emission efficiency in the film state. However, the large internal inversion rate (kIC (Tn) ) between high-lying triplet levels (Tn ) and Tn-1 causes a huge loss of triplet excitons, resulting in dissatisfied device performance of these AIEgens-based non-doped OLEDs. Herein, we designed and synthesized a blue luminogen of DPDPB-AC by fusing an AIEgen of TPB-AC and a DMPPP, which feature hot exciton and triplet-triplet annihilation (TTA) up-conversion process, respectively. DPDPB-AC successfully inherits the AIE feature and excellent horizontal dipole orientation of TPB-AC. Furthermore, it owes smaller kIC (Tn) than TPB-AC. When DPDPB-AC was applied in OLED as non-doped emitting layer, an outstanding external quantum efficiency of 10.3 % and an exceptional brightness of 69311 cd m-2 were achieved. The transient electroluminescent measurements and steady-state dynamic analysis confirm that both TTA and hot exciton processes contribute to such excellent device performance. This work provides a new insight into the design of efficient organic fluorophores by managing high-lying triplet excitons.

Thermodynamic property of sandwich cylindrical shell structure with metallic wire mesh: Numerical modeling and experimental analysis

As a new addition to lightweight composite structures, the sandwich cylindrical shell with a metallic wire mesh core has emerged as a promising solution for thermodynamic performance analysis at elevated temperatures. The intricate interwoven cellular formations within the metallic wire mesh pose difficulties for thermo-mechanical modeling and property evaluation. First, the constitutive models employed to characterize hysteresis phenomena were presented, comprising isotropic elasticity, Bergstrom-Boyce model, Ogden hyper-elasticity, and parameter identification through mechanical examinations at varying temperatures. Second, the finite element modeling of cylindrical shell structures was determined for modal and steady-state dynamic analyses. Third, the experimental procedures were carried out, including the preparation of the sandwich cylindrical shell and the dynamic testing platform. The first-order natural frequency of the cylindrical shell structure is close to the resonance frequency of the dynamic test results, with a maximum error of 6.5%, demonstrating the accuracy of the simulation model. When compared to the solid-core cylindrical shell, the average insertion loss of the sandwich cylindrical shell structure within the frequency range of 10–1000 Hz at room temperature is up to 11.09 dB. Furthermore, at elevated temperatures, the average insertion loss of the sandwich cylindrical shell decreases but fluctuates as the temperature changes.

Steady-state dynamic response analysis of single-degree-of-freedom dual frame-wall resilient system

A mixed dual frame-wall resilient system, composed of a high-strength moment-resisting steel frame (HS-MRF) and self-centering steel plate shear walls (SC-SPSWs), was proposed to address the issue of frame expansion. To study the steady-state dynamic responses of the structural system, an analytical solution of a single-degree-of-freedom nonlinear oscillator under harmonic excitation was solved using the method of averaging. The steady-state responses of HS-MRF, self-centering frame and steel plate shear wall that are represented by the bilinear, self-centering and pinching hysteresis, respectively, were studied individually, followed by a full system study. A stability analysis was also carried out to evaluate the behaviour of the singular points. The results show that the hysteretic damping in the bilinear system can significantly reduce the resonance, and the responses are always stable. Jump phenomenon occurs in the self-centering system, and increasing the post-yield stiffness can reduce the nonlinearity, thus decreasing the resonance and unstable region. Unbounded resonance responses appear in the pinching system under large excitation but can change to jump behaviour under small excitation. A left-unbounded unstable region was also found when the unloading force is small. In the combined-hysteresis system, increasing the portion of bilinear hysteresis has negligible effects on the resonance but can reduce the nonlinearity under lower excitation intensities. However, under higher intensities, increasing bilinear hysteresis can significantly decrease peak responses and reduce both the jump and unbounded phenomena. The unstable regions also strongly depend on the ratio of hysteretic models. These findings shed light on the inherent dynamic properties of the dual frame-wall system and suggest that a well-design can achieve a favourable seismic performance.

A homogenization method for natural frequencies and damping analysis of composite pyramidal lattice truss sandwich structures based on representative volume elements

A homogenization method for the vibration analysis of periodic sandwich panels is presented. Periodic boundary conditions are applied to a representative volume element (RVE) of the structures. The complex responses of the RVE under eight sinusoidal excitations are calculated and the complex stiffness matrix of the sandwich panels is obtained by the direct-solution steady-state dynamic analysis (DSDA) using the finite element method (FEM) in the frequency domain. Based on equivalent single-layer (ESL) theory and finite element-modal strain energy (FE-MSE) method, the natural frequencies, the mode shapes and the loss factors of the structures are obtained by shell models. The effectiveness of the homogenization method is validated by using pyramidal lattice truss sandwich panels made of carbon fiber reinforced plastics (CFRP). The results obtained by the homogenization method are compared with those obtained by experiments and solid models. The effects of the number of cells and damping layers are discussed.

Identification of the parameters of a composite material by experimental-computational damping research

Calculation of the modal and damping characteristics necessary to eliminate resonant oscillation of products made of polymeric materials requires reliable data on the elastic characteristics of the material. The problem is that the mechanical properties of polymer composite materials depend on a large number of factors. The aim of the work is to determine the damping coefficients for a layered composite material and the subsequent validation of the mathematical model. The Rayleigh damping model was chosen to calculate the damping coefficients. The choice is due to the fact that the resulting stiffness and mass matrix is determined by the natural oscillation modes of the problem without attenuation, which makes it possible to split the modes into separate dynamic subtasks. A sample made according to the ASTM standard was chosen as the object of study. To increase an error of the calculation, the mathematical model of the sample was modeled in detail by the finite element method using the technique of layer-by-layer modeling. The method for determining the damping coefficients is carried out in three stages. At the first stage, with the help of modal analysis, the natural oscillation modes are determined, corresponding to the nature of the oscillation studied in the experiment. At the second stage, an implicit dynamic analysis with default damping parameters in order to calculate the damping ratio is performed. At the last stage, a steady-state dynamic analysis taking into account the characteristics obtained in the previous stages. Next, an iterative process begins, including implicit and steady-state dynamic analyses, performed alternately. At each step, the previously calculated Rayleigh proportionality coefficients are introduced into the model. As a result of the identification of the mathematical model, the damping coefficients α and β are calculated. The damping experiment was chosen as a validation problem. The damping ratio ζ was chosen as the criterion of convergence with the experimental data.

UNIFIED POWER FLOW CONTROLLER CONTROL STRATEGIES for POWER FLOW

In order to address power flow control issues, this study introduces the use of Unified Power Flow Controller (UPFC) models. These models are based on regulating the variables influencing the transmission line’s power flow, and they are capable of controlling the bus voltage, the line’s actual and reactive power, all at once and independently. The idea behind the UPFC technique proposed in this paper is to provide the unique functional capability of independently controlling both the real and reactive power flow in the line. The in-phase component of the series injected voltage dominates the reactive power while the quadrature component affects the real power. A conventional controlling steady-state analysis and dynamic stability analysis of the power system is developed based on the UPFC model. UPFC provides real-time controlling of all or any combination of the power system parameters which determine the transmittable power. UPFC can force and maintain strategically chosen values of the active power and the reactive power at a given point of the line by PI control.

Thermal and mechanical analysis of low-temperature and low-pressure silver-based sintered thermal joints

PurposeThis paper aims to perform thermal and mechanical characterization for silver-based sintered thermal joints. Layer quality affects thermal and mechanical performance, and it is important to achieve information about how materials and process parameters influence them.Design/methodology/approachThermal investigation of the thermal joints analysis method was focused on determination of thermal resistance, where temperature measurements were performed using infrared camera. They were performed in two modes: steady-state analysis and dynamic analysis. Mechanical analysis based on measurements of mechanical shear force. Additional characterizations based on X-ray image analysis (image thresholding), optical microscope of polished cross-section and scanning electron microscope image analysis were proposed.FindingsSample surface modification affects thermal resistance. Silver metallization exhibits the lowest thermal resistance and the highest mechanical strength compared to the pure Si surface. The type of dynamic analysis affects the results of the thermal resistance.Originality/valueInvestigation of the layer quality influence on mechanical and thermal performance provided information about different joint types.

Detection of mode frequencies for spherical cavity embedded within a mild steel plate

The modern era of structures has observed a vast increase in non-destructive evaluation techniques in order to detect unwanted damages or porosities within the structure. Detection of defect frequencies will play a vital role in local defect resonance–based defect imaging in the future. In this paper, a technique for porosity and cavity detection in metals is discussed. A numerical investigation is carried out first on a square mild steel plate with a spherical cavity and a square mild steel block with multiple cavities. Different resonance frequencies and corresponding mode shapes in the case of the single cavity are calculated using steady state dynamic analysis. Six fundamental mode shapes are identified as Rocking (R), Torsional (T), Bouncing (B), 4-noded (4 N), 6-noded (6 N) and 8-noded (8 N) modes. Moreover, an explicit dynamic analysis is performed by exciting the model with a chirp signal for both cases of single and multiple cavities. The numerical study is supported by experimental results, performed on a mild steel plate embedded with a single spherical cavity and previously published literature. It is observed that the analytical, numerical as well as the experimental results obtained for all the modes are in close agreement with each other. The bouncing mode is found to be the promising one for pore imaging due to its uniform displacement across all the directions.

Numerical study of the aggregate contact effect on the complex modulus of asphalt concrete

Asphalt concrete (AC) is a composite material consisting of binder, aggregates and air voids. The quantitative effect of aggregate-to-aggregate contact on the mechanical performance of AC is an important and complex issue, which has not been fully understood yet. To fill this gap, this study aims to characterize the aggregate contacts in AC and evaluate their effects on the viscoelastic behavior of AC through micromechanical finite element (FE) modeling. To this end, 3D microstructural models were generated through digital image processing (DIP) method and aggregate contacts were captured in the model via contact zone (CZ) elements. A CZ model was proposed and verified by a parametric study to identify the viscoelastic properties of CZ elements, while the viscoelastic properties of matrix phase were determined through laboratory tests. Steady-state dynamic (SSD) analysis was then conducted to investigate the macro-scale viscoelastic response of AC. It was found that the proposed modeling approach captures the measured response accurately. Accounting for aggregate contacts results in higher predicted AC dynamic moduli and lower phase angles, thus improving the agreement between modeling and experimental results. The numerical model developed in this study provides a promising approach for investigating the effect of aggregate contacts on the mechanical performance of AC.

Steady-state dynamic response analysis of self-centering structural systems with viscous damping

This paper presents steady-state dynamic response analysis of recently developed two types of self-centering structural systems with viscous damping. One of them has nonlinear elastic behavior in the primary structures, and the seismic energy is dissipated by added viscous damping. The other system has elasto-plastic hysteretic behavior in the primary structures, and the seismic energy is dissipated by both yielding of primary structure and added viscous damping. While the developed self-centering structural systems have advantages in reducing residual displacement and acceleration, it is anticipated that such self-centering systems may have large displacement demand due to the potentially limited energy dissipation. The results obtained in this paper show that the supplemental viscous damping of 10% and 20% is required to effectively control the displacement demand for self-centering systems whose primary structural system is nonlinear elastic and elasto-plastic behaviors, respectively. The effects of various parameters of the hysteretic response on the system's seismic peak displacement demand were also investigated.

Self-loosening effects on vibration characteristics of plates with bolted joints: An experimental and finite element analysis

Vibration characteristics of a plate with six-bolt single-lap joint are investigated in both experimental tests and finite element (FE) method. The FE results are obtained using nonlinear steady-state dynamic analysis via ABAQUS software. The interaction surface is simulated by a nonlinear elasto-plastic thin interface layer. Natural frequencies are measured using experimental modal tests for various bolt tightening torques. The FE model is updated using the direct method and the effectiveness parameters are evaluated by experimental data. Finally, the effect of self-loosening of bolted joints on vibration characteristics of the response signal, including natural frequencies, energy parameters, kurtosis, and standard deviation are investigated. The results obtained from the FE model show good agreement with ones from the experimental modal test. Additionally, it can be concluded that for the bolt loosening defects identification, time-domain processes, and energy-based signal parameters, standard deviation, and kurtosis of the vibration signals are more appropriate rather than natural frequencies analysis.

Steady state dynamic analysis and testing of an FSAE vehicle

The work proposes a method for the synthesis of chassis parameters for achieving specific steady state and transient characteristics of a vehicle. An approach that employs a set of static and dynamic tests coupled with vehicle dynamics simulation models is presented which provide a better insight into vehicle tuning and gaining insight into these dynamic test results. The testing procedures are divided into static and dynamic tests. Static tests focus on characterizing the vehicle's suspension and steering systems by employing a Kinematics and Compliance rig. These static tests are essential before conducting any dynamic test to make sure the dynamic tests cover the non-linearity caused due to these. The static test is followed by the dynamic tests along with MATLAB simulations to gain initial understanding of what to expect from these test procedures. A steady state test is carried out to compute the understeer gradient of the vehicle which in physical terms can be translated to how comfortable the vehicle is to drive over a range of lateral acceleration. The simulation involves the static test data which completes the metric estimation at both simulation level as well as from the raw data. This steady state test is followed by a transient test which employs tools from control theory to make it easier to analyze the vehicle and tune it for specific transient response times which are favorable to the driver. These dynamic test outputs can now be used for the synthesis of vehicle parameters. The parameter sensitivity of metrics from the simulations can be used to fine tune the vehicle during testing sessions in a more intuitive and effective manner.

Simulation of L-4 lumbar spine model of motorist exposed to vibration from speed hump

BackgroundThe motorcycle is often used in recurring travel between locations, dense traffic, poor conditioned roads and thus the repetitive loading on the musculoskeletal system of the rider leads to risk factors associated with musculoskeletal disorders. This study was aimed to examine the biomechanical response of the L-4 lumbar spine while riding the motorcycle on the speed hump at 20 km/h. MethodsThree-dimensional (3D) model of the L-4 lumbar spine was reconstructed based on the CT scan data obtained from the subjects. Material properties of the L-4 lumbar spine were assumed to be isotropic and homogenous. Mesh convergence and sensitivity analyses were performed and validated before simulation. Static and dynamic analyses were accomplished using quasi-static and steady-state dynamic analyses. ResultsStatic analysis results show that the highest stress concentrations were found around the pedicle and spinal canal. It is an expected commonplace for injuries because of loading. The dynamic simulation results showed the major resonance of the L-4 lumbar spine model is about 8–40 Hz. The stress, displacement, velocity, and acceleration value declines beyond 40 Hz as the frequency increases. ConclusionsThe simulation specifies the symmetric and unsymmetrical distributions of vibration magnitude regions of the lumbar spine. This study provides the modelling of the lumbar spine (L-4) and validated the effect of overloading failure as well as identified the biomechanical behaviour.

Static & dynamic performance analysis and modal simulations of single point cutting tool

Tool manufacturers’ aims to produce quality tools to with stand higher cutting forces, thermal resistivity with increased wear resistance to improve tool life and to produce better surface finish maintaining dimensional accuracy of the finished product. The paper analyses the machining performances of single point cutting tool made from high speed steel and tungsten carbide in dry machining of mild steel and aluminium. Varying cutting speeds, feed rates and depth of cuts were taken into consideration for the experimental performance, using lath tool dynamometer. The data obtained from the experiments are used for the static, modal and steady state dynamic analysis using FEA package ABAQUS solver. From the static analysis, it was found that WC has a higher stiffness and durability as compared to the HSS. The natural frequencies and the mode shapes of the HSS and WC tools were identified and plotted. The analysis showed WC tool has higher natural frequencies as compared to the HSS tool for each of the six mode shapes. The dynamic analysis of the tools showed the deformation was least for WC. The stress induced in WC was found to be around 50% of that of HSS and the factor of safety was almost double to that of HSS. Thus this paper shows that static and dynamic performance analysis of the WC tools is better than the HSS tools.

Numerical and Experimental Investigation of the Design of a Piezoelectric De-Icing System for Small Rotorcraft Part 1/3: Development of a Flat Plate Numerical Model with Experimental Validation

The objective of this research project is divided in four parts: (1) to design a piezoelectric actuator-based de-icing system integrated to a flat plate experimental setup and develop a numerical model of the system with experimental validation, (2) use the experimental setup to investigate actuator activation with frequency sweeps and transient vibration analysis, (3) add ice layer to the numerical model and predict numerically stresses for different ice breaking with experimental validation, and (4) bring the concept to a blade structure for wind tunnel testing. This paper presents the first objective of this study. First, preliminary numerical analysis was performed to gain basic guidelines for the integration of piezoelectric actuators in a simple flat plate experimental setup for vibration-based de-icing investigation. The results of these simulations allowed to optimize the positioning of the actuators on the structure and the optimal phasing of the actuators for mode activation. A numerical model of the final setup was elaborated with the piezoelectric actuators optimally positioned on the plate and meshed with piezoelectric elements. A frequency analysis was performed to predict resonant frequencies and mode shapes, and multiple direct steady-state dynamic analyses were performed to predict displacements of the flat plate when excited with the actuators. In those steady-state dynamic analysis, electrical boundary conditions were applied to the actuators to excite the vibration of the plate. The setup was fabricated faithful to the numerical model at the laboratory with piezoelectric actuator patches bonded to a steel flat plate and large solid blocks used to mimic perfect clamped boundary condition. The experimental setup was brought at the National Research Council Canada (NRC) for testing with a laser vibrometer to validate the numerical results. The experimental results validated the model when the plate is optimally excited with an average of error of 20% and a maximal error obtained of 43%. However, when the plate was not efficiently excited for a mode, the prediction of the numerical data was less accurate. This was not a concern since the numerical model was developed to design and predict optimal excitation of structures for de-icing purpose. This study allowed to develop a numerical model of a simple flat plate and understand optimal phasing of the actuators. The experimental setup designed is used in the next phase of the project to study transient vibration and frequency sweeps. The numerical model is used in the third phase of the project by adding ice layers for investigation of vibration-based de-icing, with the final objective of developing and integrating a piezoelectric actuator de-icing system to a rotorcraft blade structure.

Interleaved Current-Fed Switched Inverter

Current-fed switched inverter (CFSI) is a high-gain inverter topology suitable for applications which have limited input dc source voltage, e.g., roof-top solar applications. A very high step-up ratio between ac output and dc input along with inherent shoot-through protection makes it suitable for low-power stand-alone inverter applications. In this article, a novel interleaved topology for CFSI (ICFSI) is proposed to augment its power rating. A pulsewidth modulation (PWM) scheme is also proposed to drive the interleaved topology. Various modes of operation of ICFSI, along with the steady-state model and dynamic analysis, with the proposed PWM scheme, are reported. ICFSI, with the PWM scheme, results in a 33% increase in maximum ac gain as compared to CFSI. In this article, the small-signal model of ICFSI is also derived and verified. An analysis comparing the losses in CFSI and ICFSI is carried out. It is observed that interleaved operation improves the efficiency by 4% at 600 W. The proposed topology and analysis are verified with the experimental results obtained from a 600-W laboratory-developed prototype.

Passive vibration control of plate using nodal patterns of mode shape

Passive constrained layer damping (PCLD) is nowadays a general method for reducing vibrations. Constrained layer damping (CLD) is a very good technology in terms of reducing vibration energy. This paper deals with optimal damping of first three modes of a thin square cantilever plate by constrained viscoelastic layers which are positioned according to the nodal patterns of the mode. In essence, the CLD patches are cut according to the nodal patterns and then applied on to the bare plate. Thus, this approach uses prior information of the deformation patterns of the plate. The ABAQUS finite element analysis software was used to create viscoelastically damped plate models subjected to forced vibration. The direct steady-state dynamic analysis was used to obtain the frequency response functions from which the resonance frequencies of the models were derived. Vibration control using nodal pattern CLD patches is a better way to apply CLD treatment to a plate. This is because the mode shapes give good predictions of where the maximum strains are in the plate as well as the design and size of the damping patches required. It is believed that the methodology proposed in this research work is capable of providing good results.

Detection of local defect resonance frequencies using bicoherence analysis

The nonlinear acoustic wave spectroscopy and defectometry (NAWSD) technique is found to be an efficient tool for monitoring intricate and complex defects in composite structures due to its better resolution and accuracy compared to the traditional methods. Local defect resonance (LDR) is one of such methods based on amplifying vibrations at the defect regions only, resulting in defect-selective and high resolution image. In the present work, numerical as well as experimental approach has been presented in order to detect the LDR frequency of aluminium plate having circular flat bottom hole (FBH) and delaminated glass fibre reinforced polymer composite (GFRP) plates. First, a wave propagation study using explicit dynamic analysis is performed followed by, bicoherence analysis to detect the LDR frequency numerically. The LDR frequency modes are also verified by steady state dynamic analysis. A set of experiments are then carried out using Gaussian white noise as well as chirp signal to determine the LDR frequencies from the Fast Fourier Transform (FFT) and bicoherence plots. In every cases, the bicoherence peaks corresponds to the second harmonic of LDR frequency. The bicoherence plots are found to be robust and effective tool for detection of LDR frequencies compared to FFT plots. Bicoherence analysis based LDR frequency determination technique can be further utilized in delamination and disbond imaging of composite structures.