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Purpose: This study presents a novel design for a biomass gasification reactor, focusing on analyzing the static mechanical and dynamic vibration characteristics of its kiln shell. Methods: The Taguchi L9 method and Gaussian surface fitting were used to analyze static mechanical properties under varied support positions. Additionally, four different kiln shell configurations were investigated to assess the effects of heat exchange tubes, support positions, and rib reinforcements on vibration displacement characteristics. Results and Conclusion: According to the findings of this study, the support positions have a considerable impact on the static mechanical characteristics of its kiln shell. Moreover, the heat exchange tubes can significantly increase the natural frequencies of the kiln shell，and the suppression of vibration displacements in risk areas can be achieved through the use of rib reinforcements. [ABSTRACT FROM AUTHOR]

The finite element analysis of CFV12000 motorized spindle is carried out in the ANSYS Workbench 16.0. And the free mode experiment is carried out for the actual structure. The finite element model is modified according to the experimental results, so that the model can accurately reflect the actual situation of the motorized spindle. Then the harmonic response of the modified finite element model is analyzed to predict the dynamic characteristics in the actual machining process of the spindle. Finally, the structure of the spindle is optimized to improve its dynamic performance. The rationality of the structure design of the electric spindle is proved, which lays the foundation for the optimization of the structure of the electric spindle and the improvement of its dynamic characteristics. [ABSTRACT FROM AUTHOR]

The oil pipeline is a critical component that influences the vibration and noise levels of the hydraulic system. Inadequate design may result in resonance or leakage issues, rendering it susceptible to external vibration excitation. To enhance the reliability of the hydraulic pipeline, simulations and analyses were conducted on its modal, harmonic response, and fatigue characteristics. Based on the results of harmonic response analysis and strength analysis, an effective reinforcement scheme was proposed and validated. By inputting the acceleration load to the pipeline system for frequency response analysis, the influence of different excitation forces on the pipeline stress can be determined. The findings indicate that pipeline vibration primarily occurs in the outlet pipe of the transmission, with significant stress and vibration displacement observed at the thermostat valve support. Following structural improvements, there was a notable reduction in stress levels at the transmission outlet pipe, along with a shift in maximum stress position due to additional support. This enhancement has improved both structural stiffness of the outlet pipe and overall stability of the pipeline system. [ABSTRACT FROM AUTHOR]

Understanding jujube tree dynamic characteristics is crucial for the design and invention of a catch-and-shake machine for fruit harvesting. Currently, the study of vibration characteristics based on the finite element method is the mainstream method for different types of fruit trees. However, limited by the lack of an accurate 3D tree model, there are still gaps between existing simulation analysis and actual tests to explore vibration characteristics. Specifically, the vibration mechanism of winter jujube trees is still unclear in jujube orchards. To address the issue, a multi-view 3D reconstruction technique is employed to acquire precise 3D tree models for simulation analysis. The obtained results from experiments indicate that the determination coefficient R 2 of the trunks and branches diameter are 0.96 and 0.91 between reconstructed and actual measurement results. Subsequently, material properties of jujube tree are measured to conduct model analysis and harmonic response analysis to find the optimal frequency range (10–20 Hz) in which a considerable vibration response can be obtained at low vibration energies. Moreover, transient analysis and test experiments are conducted to explore the energy transfer properties under different vibration frequency. Results showed that the acceleration response gradually increased from the bottom to the top of the branch on most branches at non-resonant frequencies. The proposed method can provide informative insights on the design of high-efficiency and low-energy jujube catch-and-shake harvesters. [Display omitted] • Accurate 3D models for jujube trees are reconstructed using SfM. • Vibration transfer characteristics are explored using transient analysis. • The optimal harvesting parameters are determined by the finite element method. • The field experiments validate the reliability of the simulation results. [ABSTRACT FROM AUTHOR]

This study presents a numerical investigation of the dynamic behavior of graphene platelet (GPL)-reinforced ethylene tetrafluoroethylene (ETFE) tensile membrane structures subjected to harmonic excitation. Modal and harmonic response analyses were performed to assess both the natural frequencies and the dynamic responses of the ETFE membrane. GPLs were employed as the reinforcements to enhance the mechanical properties of the membrane materials, whose Young's modulus was predicted through the effective medium theory (EMT). Parametric studies were conducted to examine the impact of pre-strain and the attributes of the GPL reinforcements, including weight fraction and aspect ratio, on the natural frequencies and amplitude–frequency response curves of the membrane structure. The first natural frequency substantially increased from 5.46 Hz without initial strain to 31.0 Hz with the application of 0.1% initial strain, resulting in a frequency shift that moved the natural frequency out of the range of typical wind-induced pulsations. Embedding GPL fillers into ETFE membrane was another potential solution to enhance the dynamic stability of the membrane structure, with a 1% addition of GPLs resulting in a 48.6% increase in the natural frequency and a 45.1% reduction in resonance amplitude. GPLs with larger aspect ratios provided better reinforcement, offering a means to fine-tune the membrane's dynamic response. These results underscore that by strategically adjusting both pre-strain levels and GPL characteristics, the membrane's dynamic behavior can be optimized, offering a promising approach for improving the stability of structures subjected to wind-induced loads. [ABSTRACT FROM AUTHOR]

Predicting how the fingertip will mechanically respond to different stimuli can help explain human haptic perception and enable improvements to actuation approaches such as ultrasonic mid-air haptics. This study addresses this goal using high-fidelity 3D finite element analyses. We compute the deformation profiles and amplitudes caused by harmonic forces applied in the normal direction at four locations: the center of the finger pad, the side of the finger, the tip of the finger, and the oblique midpoint of these three sites. The excitation frequency is swept from 2.5 to 260 Hz. The simulated frequency response functions (FRFs) obtained for displacement demonstrate that the relative magnitudes of the deformations elicited by stimulating at each of these four locations greatly depend on whether only the excitation point or the entire finger is considered. The point force that induces the smallest local deformation can even cause the largest overall deformation at certain frequency intervals. Above 225 Hz, oblique excitation produces larger mean displacement amplitudes than the other three forces due to excitation of multiple modes involving diagonal deformation. These simulation results give novel insights into the combined influence of excitation location and frequency on the fingertip dynamic response, potentially facilitating the design of future vibration feedback devices. [ABSTRACT FROM AUTHOR]

In order to study the structural performance of the new bend-twist coupling blade, NREL 5 MW blade was taken as the prototype, and the geometric model of the blade was established by using NX Open Grip parameterization language. The composite lamination design was carried out in accordance with the real processing technology, and the aerodynamic force of the blade was obtained by the computational fluid dynamics (CFD) method. The bend-twist coupling characteristics, harmonic response and strength of conventional and bending-torsional coupling blades were analyzed respectively. The results show that the blade tip displacement increases with the increase of the web deflection. For the same angle, the blade tip displacement of γ > 0 blades was smaller than that γ < 0 blades. The bend-twist coupling effect is the most obvious when γ = 10° and 15°. Compared with the conventional blade, the second-order displacement responses of bend-twist coupling blades are significantly reduced. The γ = 15° blade can reduce the stress on the surface and has a good load reduction performance.

Hydraulic turbines have become indispensable for harnessing renewable energy sources, particularly in-pipe hydraulic turbine technology, which leverages excess energy within pipeline systems like drinking water distribution pipes to produce electrical power. Among these turbines, the propeller-type axial turbine with circular blades stands out for its efficiency. However, there is a notable lack of literature on fluid dynamics and structural behavior under various operational conditions. This study introduces a comprehensive methodology to numerically investigate the hydraulic and structural responses of turbines designed for in-pipe installation. The methodology encompasses the design of circular blades, followed by parametric studies on fluid dynamics and structural analysis. The circular blade's performance was evaluated across different materials, incorporating static, modal, and harmonic response analyses. Results showed that the circular blade achieved a peak hydraulic efficiency of 75.5% at a flow rate of 10 l/s, generating 1.86 m of head pressure drop and 138 W of mechanical power. Structurally, it demonstrated a safety factor exceeding 1 across the entire hydraulic range without encountering resonance or fatigue issues. This research and its methodology significantly contribute to advancing the understanding of designing and assessing the fluid dynamic behavior and structural integrity of circular blades in axial propeller-type turbines for in-pipe installations, serving as a valuable resource for future studies in similar domains. [ABSTRACT FROM AUTHOR]

This article is devoted to the problem of signal decomposition into periodic and aperiodic components. According to the proposed approach, there is no need to evaluate the aperiodic component as a difference between the total signal of its periodic components. This research aims to create a general analytical approach that combines the Fourier and Maclaurin series methodologies into a single comprehensive series. As a result, analytical expressions for determining deposition coefficients were established for an aperiodic signal with a monoharmonic overlay. Recurrence relations were established to determine the coefficients of this series. These relations allow direct integrations of the obtained values of integrals to be avoided. The evaluated numerical values of the coefficients are also presented graphically and tabulated. It was proven that the values of these coefficients are universal numbers since they do not depend on the period/frequency of oscillations. The reliability of the proposed approach was confirmed by the fact that the evaluated coefficients are equal to the Fourier series coefficients in the case of a periodic signal. Also, for an aperiodic signal, these coefficients were reduced to the coefficients of the Maclaurin series. The usability of the proposed generalized analytical approach for signal decomposition is for control and monitoring systems of processes. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Mechanical Strength / Jixie Qiangdu is the property of Zhengzhou Research Institute of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Gamma oscillations, thought to arise from the activity of ɣ‐aminobutyric acid (GABA)ergic interneurons, have potential as a biomarker for schizophrenia. Gamma‐band auditory steady‐state responses (ASSRs) are notably reduced in both chronic and early‐stage schizophrenia patients. Furthermore, alterations in gamma‐band ASSRs have been demonstrated in animal models through translational research. However, the 40‐Hz harmonic responses of the 20‐Hz ASSR are not as well‐characterized, despite the possibility that these harmonic oscillatory responses may reflect resonant activity in neural circuits. In this study, we investigated the 40‐Hz harmonic response to the 20‐Hz ASSR in the early stages of schizophrenia. The study recruited 49 participants, including 15 individuals at ultra‐high‐risk (UHR) for psychosis, 13 patients with first‐episode schizophrenia (FES), and 21 healthy controls (HCs). The 40‐Hz harmonic responses of the 20‐Hz ASSR were evident in all groups. Interestingly, while previous report observed reduced 40‐Hz ASSRs, the 40‐Hz harmonic responses of the 20‐Hz ASSR were not reduced in the UHR or FES groups. These findings suggest that the gamma‐band ASSR and its harmonic responses may represent distinct aspects of pathophysiology in the early stages of schizophrenia.

This study presents a numerical investigation of the dynamic behavior of graphene platelet (GPL)-reinforced ethylene tetrafluoroethylene (ETFE) tensile membrane structures subjected to harmonic excitation. Modal and harmonic response analyses were performed to assess both the natural frequencies and the dynamic responses of the ETFE membrane. GPLs were employed as the reinforcements to enhance the mechanical properties of the membrane materials, whose Young’s modulus was predicted through the effective medium theory (EMT). Parametric studies were conducted to examine the impact of pre-strain and the attributes of the GPL reinforcements, including weight fraction and aspect ratio, on the natural frequencies and amplitude–frequency response curves of the membrane structure. The first natural frequency substantially increased from 5.46 Hz without initial strain to 31.0 Hz with the application of 0.1% initial strain, resulting in a frequency shift that moved the natural frequency out of the range of typical wind-induced pulsations. Embedding GPL fillers into ETFE membrane was another potential solution to enhance the dynamic stability of the membrane structure, with a 1% addition of GPLs resulting in a 48.6% increase in the natural frequency and a 45.1% reduction in resonance amplitude. GPLs with larger aspect ratios provided better reinforcement, offering a means to fine-tune the membrane’s dynamic response. These results underscore that by strategically adjusting both pre-strain levels and GPL characteristics, the membrane’s dynamic behavior can be optimized, offering a promising approach for improving the stability of structures subjected to wind-induced loads.

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Gamma oscillations, thought to arise from the activity of ɣ‐aminobutyric acid (GABA)ergic interneurons, have potential as a biomarker for schizophrenia. Gamma‐band auditory steady‐state responses (ASSRs) are notably reduced in both chronic and early‐stage schizophrenia patients. Furthermore, alterations in gamma‐band ASSRs have been demonstrated in animal models through translational research. However, the 40‐Hz harmonic responses of the 20‐Hz ASSR are not as well‐characterized, despite the possibility that these harmonic oscillatory responses may reflect resonant activity in neural circuits. In this study, we investigated the 40‐Hz harmonic response to the 20‐Hz ASSR in the early stages of schizophrenia. The study recruited 49 participants, including 15 individuals at ultra‐high‐risk (UHR) for psychosis, 13 patients with first‐episode schizophrenia (FES), and 21 healthy controls (HCs). The 40‐Hz harmonic responses of the 20‐Hz ASSR were evident in all groups. Interestingly, while previous report observed reduced 40‐Hz ASSRs, the 40‐Hz harmonic responses of the 20‐Hz ASSR were not reduced in the UHR or FES groups. These findings suggest that the gamma‐band ASSR and its harmonic responses may represent distinct aspects of pathophysiology in the early stages of schizophrenia. [ABSTRACT FROM AUTHOR]

The interest in wind-assisted ship propulsions (WASPs) is increasing to improve fuel efficiency and to reduce greenhouse gas emissions in ships. A rotor sail, one of the typical WASPs, can provide auxiliary propulsive force by rotating a cylinder-shaped structure based on the Magnus effect. However, due to its huge rotating structure, a meticulous evaluation of the influence on the ship structure and dynamical stability of the rotating structure should be conducted in the design stage. In this respect, an analysis of the rotating structure for a 30 m height and 3 m diameter rotor sail was conducted in this study. First, a 4DOF (four-degree-of-freedom) model was derived to simplify the dynamics of the rotor sail. Using the 4DOF model, natural frequencies for four low-order modes of the rotor sail were calculated, and frequency responses at support points were predicted. Next, a comparison and validation with the finite element model of the rotor sail were carried out. For the 1st and 2nd natural frequencies, a difference of approximately 0.3 Hz was observed between the 4DOF model and the finite element model, confirming the effectiveness of the 4DOF model for low-order modes. In analysis with changes in the bearing supporting stiffnesses, it was verified that lower support bearings have a significant impact on rotor dynamics compared to upper support bearings. Vibration response at the upper support was also confirmed through frequency response analysis caused by imbalance at Thom disk and mid-plate. Additionally, when estimating the eccentricity of the Thom disk as imbalance, a limit of eccentricity error could be set as 24 mm. The presented modeling procedures and analysis results can be references during early design stage of a novel rotor sail structure. [ABSTRACT FROM AUTHOR]

Relevance of the research. Numerical studies of structural frequency response of a large-span building with cylindrical-and-slab roof as a large mechanical system were carried out. Finite element model No. 1 “Superstructure-Fixed-end” . The purpose of the study was to develop the methodology for modal analysis of a large-span building structure with a cylindrical-and-slab roof as a mechanical system with a large number of degrees of freedom . Methods. Numerical analysis of the building dynamics was carried out with the use of the САЕ (Computer-aided engineering) software package Femap NX NASTRAN, which implements the finite element method. Results. The “dangerous” resonant frequencies and forms of harmonic oscillations of the structure were revealed, and the sensitivity of the buildings’ reactions to various structural changes was analyzed. Frequency analysis of harmonic response of the building allowed to obtain dependences of amplitude values of nodal displacements (accelerations) and stresses in finite elements from the frequency of the inducing external force. In the next article, it is proposed to conduct a dynamic analysis of a large-span building with a cylindrical-and-slab roof for seismic effects.

Harmonic oscillations of piezoceramic functional-gradient sectioned hollow cylinders are studied, taking into account energy dissipation. A cylinder of finite length is considered. Cylinder consists of an even number of sections polarized in the circular direction, which are connected to each other by similar sides. The material is considered to be functionally heterogeneous in the direction of the previous polarization. The cylinder is loaded by the potential difference applied to the flat faces of the sections. The calculation is performed by the finite element method. Damping matrices forming and determining of coefficients corresponding to methods of introducing frequency-independent damping and Rayleigh damping is described. Electric losses are taken into account by entering the dielectric loss tangent or dielectric loss tangent matrix. The result of calculations is compared with the result obtained with the help of complex elastic and dielectric moduli. Amplitudefrequency characteristics are constructed for movements, charge on the electrodes, electrical admittance and its logarithm, taking into account damping. Energy dissipation consideration is related to the experimental data due to the mechanical quality factor of the piezo element. The frequencies of electrical resonances, anti-resonances and corresponding electromechanical coupling coefficients for functionally inhomogeneous and homogeneous cylinders are determined. For the functional-gradient piezoelectric element of the considered configuration, the maximum CEMC occurs at the frequency of the second electrical resonance. At this frequency, the dynamic stress-strain state of the cylinder is investigated. Forms of oscillations and distribution of stress amplitude values are constructed. The largest normal stresses according to the Coulomb-Mohr strength theory are determined and compared with the von Mises strength theory. FEA allows three-dimensional calculation of harmonic oscillations of functional-gradient piezo elements of complicated geometry. The determined frequencies of electrical resonance and anti-resonance and the corresponding CEMC make it possible to choose the most effective operating mode of the piezo element. The FEM mathematical apparatus makes it possible to quickly and qualitatively evaluate the strength, determine the charge on the electrodes, the current in the circuit, build the amplitude-frequency characteristics of admittance and impedance, and evaluate the efficiency of energy conversion. [ABSTRACT FROM AUTHOR]

To show dynamic properties of a motorized spindle at high speed, C01 type motorized spindle bearing-rotor system is used as a study object, and the dynamic model of the bearing-rotor system is established. The method to analyze vibration characteristics of motorized spindles by power flow is proposed, and it is found that the vibration energy is not necessarily considerable at the position where the vibration displacement response is significant. Finally, the system vibration energy distribution under different bearing stiffness is analyzed. The power flow method can analyze the dynamic characteristics of the bearing-rotor system in terms of energy distribution. [ABSTRACT FROM AUTHOR]

In this study, numerical simulations are carried out to determine the open water performance of the INSEAN E779A marine propeller. On the other hand, modal and harmonic response analysis under hydrodynamic loading are carried out by using unidirectional approach by coupling the ANSYS Mechanical and the ANSYS CFX codes. The finite element model of the propeller has been constructed. By using this model, the dynamic characteristics of the blade have been analysed. The first 12 natural frequencies under nominal operating conditions, and the harmonic response of the exciting fluid pressures, are obtained. During Fluid-Structure Interaction, the flow around the propeller can lead to excitation of the resonance. The calculated open water performances in terms of thrust and torque coefficients correspond very well to the experimental data for a wide range of the advance coefficient. The results obtained show that the operating frequencies of the INSEAN E779A marine propeller are much lower than the resonant frequencies, so resonant conditions are easily avoided. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Chongqing University of Technology (Natural Science) is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Tubes, actuators, and aeroplane landing gears are instances of tubular elements with deep holes and thin-wall constructions; such components are the backbone of the aerospace industry. Precision machining of interior holes of cylindrical objects with narrow bores and significant depth to diameter ratios (> 7–8) is more difficult, which highlights the need of grinding such deep holes. In this study, an enhanced construction of the deep hole internal grinding machine is developed and the structural behavior with two different materials cast iron and artificial granite material studied. The internal grinding shaft tool structure is a critical component of this grinding machine, and it is one of the most important variables affecting surface grinding quality due to the structure's length and intricacy, as well as its restrictive outside dimensions. While carrying out the study of machine structure, shaft is also exclusively analyzed with an optimized design. Being the most crucial part of the machine, shaft design was verified through the comparative study of theoretical, simulation analyses, and experimental work. [ABSTRACT FROM AUTHOR]

This study focuses on the analysis of a linear hydrostatic bearing using harmonic frequency response and harmonic response simulations. The aim is to evaluate the feasibility of replacing the existing alloy steel material with a metal matrix composite (MMC) in terms of its performance and dynamic characteristics for both the base and carriage parts. The simulation results indicate that the MMC material exhibits higher resonant frequencies and improved damping capabilities compared to the structural steel material. The higher resonant frequencies observed in the MMC material are attributed to its stiffness and structural properties. These properties contribute to increased natural frequencies and improved vibration damping characteristics. This suggests that incorporating the MMC material in the bearing design could enhance motion control, improving the ability to precisely control and manipulate the movement of components or systems. In the context of ultraprecision machining applications, incorporating the MMC material in the hydrostatic bearing design can also lead to a more accurate and controlled motion, resulting in improved precision and finer machining outcomes. The displacement analysis confirms that both materials meet the specifications provided by the manufacturer, supporting the viability of using MMC as an alternative. However, further experimental validation and considerations of material feasibility, manufacturing factors, and cost-effectiveness are necessary before implementing the MMC material in practical applications. Overall, this research highlights the potential benefits of MMC in the design of linear hydrostatic bearings, paving the way for enhanced performance in ultraprecision machining processes. [ABSTRACT FROM AUTHOR]

An experimental and numerical study on the mechanical and damping properties of styrene-butadiene rubber (SBR) composites with graphene nanoparticles (GNP) and carbon black (CB) is presented in this paper. The composites were tested for mechanical properties such as hardness and tensile strength. It is observed that the composites with GNP & CB fillers have higher stiffness and percentage elongation for failure. A scale model of the chassis was subjected to forced vibration to find the damping properties of each of the prepared composites. The experimental results were used to create a numerical model in ANSYS software using Yeoh's hyper-elastic model to generate a hyper-elastic material to simulate the composite property and to perform harmonic response analysis in ANSYS. The results from experiments and theoretical findings exhibited good agreement.

The researches on vibration and harmonic responses of a bubble cluster in an acoustic field are the foundations of bubble cavitation dynamics. The nonlinear vibration of bubbles, the harmonic response of bubbles in a spherical bubble cluster and influencing factors are studied. The results show that the interaction between bubbles will suppress the vibration of bubbles and change the frequency of bubble vibration. There is a certain phase difference in the nonlinear vibration of bubbles at different positions in a spherical bubble cluster. The nonlinear vibration of bubbles depends on the amplitude of driving acoustic pressure, driving frequency, the equilibrium radius of a bubble, bubble number and other factors. The nonlinear vibration of bubbles in bubble cluster can excite sub-harmonic, high-order harmonic and ultra-harmonic signals. The type and intensity of harmonics in a bubble cluster are related to the equilibrium radius, bubble number, the amplitude of driving acoustic pressure and driving frequency. [ABSTRACT FROM AUTHOR]

Copyright of Large Electric Machine & Hydraulic Turbine is the property of Large Electric Machine & Hydraulic Turbine Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The interest in wind-assisted ship propulsions (WASPs) is increasing to improve fuel efficiency and to reduce greenhouse gas emissions in ships. A rotor sail, one of the typical WASPs, can provide auxiliary propulsive force by rotating a cylinder-shaped structure based on the Magnus effect. However, due to its huge rotating structure, a meticulous evaluation of the influence on the ship structure and dynamical stability of the rotating structure should be conducted in the design stage. In this respect, an analysis of the rotating structure for a 30 m height and 3 m diameter rotor sail was conducted in this study. First, a 4DOF (four-degree-of-freedom) model was derived to simplify the dynamics of the rotor sail. Using the 4DOF model, natural frequencies for four low-order modes of the rotor sail were calculated, and frequency responses at support points were predicted. Next, a comparison and validation with the finite element model of the rotor sail were carried out. For the 1st and 2nd natural frequencies, a difference of approximately 0.3 Hz was observed between the 4DOF model and the finite element model, confirming the effectiveness of the 4DOF model for low-order modes. In analysis with changes in the bearing supporting stiffnesses, it was verified that lower support bearings have a significant impact on rotor dynamics compared to upper support bearings. Vibration response at the upper support was also confirmed through frequency response analysis caused by imbalance at Thom disk and mid-plate. Additionally, when estimating the eccentricity of the Thom disk as imbalance, a limit of eccentricity error could be set as 24 mm. The presented modeling procedures and analysis results can be references during early design stage of a novel rotor sail structure.

The harmonic response and acceleration characteristic of drillstring is established to improve borehole quality for the hydrogen underground storage (HUS). The harmonic response laws of drillstring is discussed. Harmonic response analysis includes non-failure case and failure case. Absorber control measure is simulated to lower vibration amplitude of drillstring. The drill string collides violently with the wellbore reduces the wellbore quality and increases the unreliability of the HUS. Lateral harmonic response has the greatest damage to well wall. Torsional harmonic response causes less damage than lateral vibration. High WOB (weight on bit) and high RPM (rotary per minute) are not conducive to the quality of HUS. In course of designing drilling parameter, it is required to avoid or reduce drillstring resonance under low-order inherent frequency as much as possible. The research result is of much significance to improve wellbore quality of hydrogen underground storage. • The dynamic response model of drill string in slim borehole was established. • The harmonic characteristic of drill string during compound drilling were studied. • The acceleration characteristics of drillstring in slim borehole were investigated. • The effects of harmonic and acceleration characteristics on the wellbore quality were studied. [ABSTRACT FROM AUTHOR]

Abstract The importance of appropriate offshore wind turbine (OWT) monopile structural modelling technique cannot be overstated in the successful design and installation of a new generation of larger and heavier structures to deliver the increasing capacity demand. The lack of clear design guidance and acceptable structural modelling techniques across the industry results in a range of conservative but expensive design and installation techniques. Most of the OWT monopile modelling efforts lie in the substructure (foundation) and interaction with the supporting soil which is highly nonlinear along the length of the embedment depth of the monopile structure. Typically, monopile offshore wind turbine structural modelling can be completed using, amongst others, one of the following techniques: 3D finite element modelling with mass soil foundation, API p‐y curve soil springs, JeanJean soil springs, and the newly developed PISA modelling approach. The study presented in this paper considers the application of the 3D finite element modelling with mass soil, API p‐y soil springs, and the JeanJean soil springs technique. By comparing the structural response, the 3D finite element modelling with mass soil results in an improved natural frequency and harmonic response. Furthermore, a reduced displacement was observed in the 3D finite element model with mass soil which will ultimately result in a corresponding improvement in the structure's useful operational design life. The application of the API p‐y soil springs, JeanJean soil springs, and other modelling techniques requires extensive calibration to ensure the correct structural response and behaviour are achieved. This becomes a key factor as the boundaries of the size of the structure and turbine capacity are pushed even further for the new concept generation offshore wind turbines, which are required to deliver a higher capacity of 12 to 15 MW with the aim of achieving 20 MW, whilst achieving an efficient cost‐effective engineering design and installation process.

In this study, the dynamic structural and mechanical properties of the polymer composite with natural fiber reinforcement have been investigated experimentally and numerically. First of all, three different types, one-, three- and five-layered jute-epoxy and hemp-epoxy laminated composite, have been manufactured using the hand lay-up method. The tensile strength, bending strength and shear strength of the fabricated composite material have been investigated experimentally using Universal Testing Machine. The density is measured using a density measurement kit using Archimedes principle. Further, frequency and damping factors are also investigated using a vibration test setup. Later on, the numerical model is developed in finite element-based software ANSYS. Different natural frequency modes and corresponding damping factors have been investigated numerically. The mechanical and structural characteristics obtained experimentally and numerically are analyzed and discussed in detail. From the investigation, it is found that the hemp-epoxy composite has a greater strength and stiffness compared to the jute-epoxy composite, irrespective of the number of fiber layers used. Further, it is also found that with the increase in fiber layers or fiber percentage in the composite, the strength and stiffness of the fabricated composite increase significantly.

This paper focuses on the magneto-aero-elastic nonlinear resonances, bifurcations and chaos for superharmonic and subharmonic responses of conductive circular plates spinning in air and magnetic fields. The electromagnetic forces acting on in-plane are presented by using electromagnetic field theory, and a rotational dissipative damping aerodynamic model is employed to characterize the aerodynamic forces acting on the plates. Considering the effects of the geometric nonlinearity and centrifugal tensioning, the magneto-aero-elastic governing equations of spinning conductive circular plates are derived by the Hamiltonian principle. Based on the mode shapes with Bessel functions, the transverse nonlinear vibration differential equations of spinning plates with clamped-edge are derived by the Galerkin method. Amplitude-frequency equations for subharmonic and superharmonic responses are obtained by using the approach of multiple scales, respectively. Numerical calculations indicate the influences of important parameters (e.g. magnetic field intensity, excitation amplitude and rotational speed) on amplitude frequency characteristics. Moreover, it is demonstrated by the numerical results that system responses are sensitive to the variation of these important parameters, where the complex intermittency, period-doubling and chaotic dynamical behaviors exist. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Natural Fibers is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The digital model of the headstock of the XK715 CNC machine tool was imported into the ANSYS Workbench environment, and the first six modal vibration shapes of the headstock were calculated. The resonance frequencies were 349.11, 663.42, 776.91, 1 227.90, 1 440.10 and 1 769.00 Hz, respectively. On this basis, the harmonic response law of the headstock is calculated by using the modal superposition method. The simulation analysis shows that when the excitation load frequency is 350, 660 and 780 Hz, the output values ​​of the deformation corresponding to the flange of the headstock end face are 8.282, 156.910 and 6.970 μm respectively; the maximum value of the stress output in the Z direction of the end face is 6 464.90 μm, 917.42 and 4 670.30 Pa; when the excitation load frequency is 660 Hz, the equivalent stress value at the 90° corner of the lower edge of the rectangular frame of the headstock is the largest, the maximum value is 63.29 MPa, and the maximum value of the total deformation is 0.22 mm. The machine tool at this frequency cannot meet the machining accuracy requirements of the parts. Therefore, the excitation load in this frequency range should be avoided during the machining process. [ABSTRACT FROM AUTHOR]

Functionally Graded Materials (FGM) are extensively employed for hip plant component material due to their certain properties in a specific design to achieve the requirements of the hip-joint system. Nevertheless, if there are similar properties, it doesn’t necessarily indicate that the knee plant is efficiently and effectively working. Therefore, it is important to develop an ideal design of functionally graded material femoral components that can be used for a long period. A new ideal design of femoral prosthesis can be introduced using functionally graded fiber polymer (FGFP) which will reduce the stress shielding and the corresponding stresses present over the interface. Herein, modal analysis of the complete hip plant part is carried out, which is the main factor and to date, very few research studies have been found on it. Moreover, this enhances the life of hip replacement, and the modal, harmonic, and fatigue analysis determines the pre-loading failure phenomena due to the vibrational response of the hip. This study deals with the cementless hip plant applying the finite element analysis (FEA) model in which geometry is studied, and the femoral bone model is based in a 3D scan.

Vibration is a common and urgent technical issue in the steel industry. The world's first multi-mode continuous-casting and rolling plant of Shou Gang Jing Tang Iron and Steel Co., Ltd. (Tangshan, China), has a finishing mill, F3, that experiences frequent, strong vibrations during the process of rolling thin-gauge (<1.5 mm) strip steel, which have seriously hindered the production of high-quality thin strip steel products. The changes in the strips' surface quality are among the factors that induce rolling mill vibrations. In this study, considering the nonlinear surface quality of strip steel, a finite element model of the F3 mill was established, and the harmonic response method was used to obtain a rolling mill vertical system in the ANSYS environment. This study assesses the sensitive amplitude versus frequency characteristics curve of a torsional coupling system, the influence of strip thickness and strip hardness fluctuations on the vibration of the primary drive system, and the dynamic amplitude versus frequency characteristics of the three directions on the top of a torii. Finally, the field experiment verifies the correctness of the analytical results, which provides theoretical guidance for suppressing rolling mill vibrations and has a certain application value. [ABSTRACT FROM AUTHOR]

This study measures the impact of the cut-out shape on the fundamental frequency and the harmonic response of thin composite circular plates under fixed boundary conditions. For this purpose, the Finite Element Method has been employed using the SHELL181 element of ANSYS Workbench 18.2 software. Nine different circular plates having central equilateral triangle, square, regular pentagon, regular hexagon, regular heptagon, regular octagon, regular nonagon, regular decagon, and circular cut-outs have been designed to understand the changes in the vibrational behavior of a structure as the cut-out geometry approximates to circular. Additionally, a solid circular plate has been modelled for comparison purposes. To investigate the effect of the cut-out shape more deeply, all structures have been designed as cross-ply and angle-ply composites. The free vibration analysis has been performed to obtain the fundamental frequency of each structure. The harmonic response analysis problem has been solved by employing the Mode Superposition Method and considering a constant damping ratio. The results of the study have been interpreted by considering the displacement response, stress, and phase shifts at a certain frequency range. The results indicate that the shape of the cut-out considerably affects the fundamental frequency and harmonic response of the circular structure regardless of its fiber orientation. [ABSTRACT FROM AUTHOR]

How nonlinear joints affect the response of large space structures is an important problem to investigate. In this paper, a multi-harmonic equivalent modeling method is presented to establish a frequency-domain model of planar repetitive structures with nonlinear joints. First, at the local level, the nonlinear joint is modeled by the multi-harmonic describing function matrix. The element of the hybrid beam is obtained by the dynamic condensation of the beam-joint element. Second, at the global level, the displacement-equivalence method is used to model the multi-harmonic Euler continuum beam equivalent to the planar repetitive structure. Then, the pseudo-arc-length continuation method is applied to track the multi-harmonic trajectory of response. Afterwards, an experiment is conducted to validate the correctness of the modeling method, considering the effect of hanging rope and air damping. In the numerical studies, several simulation results indicate the similarity of response between a single-degree-of-freedom system with a single nonlinear joint and the system of the planar repetitive structure with a large number of nonlinear joints. Finally, the component of higher-order harmonics is shown to be important for predicting the resonance frequencies and amplitudes. [ABSTRACT FROM AUTHOR]

• An ANN based machine learning multiscale modelling strategy is proposed to predict the mechanical properties of PW-CFRP and other types of CFRP with high accuracy and low computational cost based on generated data sets. • A GDQ based computational strategy is established to calculate the random and harmonic frequency-response characteristics for conical-conical shells. • Excitation type, excitation and response points, geometric parameters on the frequency-response characteristics are extensively analyzed. This study analyzes the frequency-response characteristics under non-stationary base random acceleration and harmonic points force excitations of plain woven carbon fiber reinforced polymers (PW-CFRP) conical-conical shells comprehensively. Artificial neural network (ANN) based machine learning multiscale modelling strategy is introduced in the process of predicting the mechanical properties of PW-CFRP. The dataset is generated by randomization, linear fitting and two-step homogenization and then trained to generate an ANN to predict the mechanical properties of PW-CFRP. The governing equations of the conical-conical shell under random acceleration excitation are obtained according to the first order shear deformation theory (FSDT) and Hamilton's principle. After the structure is split along the circumference at the excitation points, the harmonic points force excitations are introduced based on the discontinuity condition between conical segments. Generalized differential quadrature (GDQ) is applied during the solving procedure. After comparison studies focusing on the frequency-response characteristics under two types of excitations, two examples on harmonic and random responses of conical-conical shell and conical-cylindrical shell are carried out separately. In this process, the effects of excitation type, excitation and response points, geometric parameters on the frequency-response characteristics are extensively analyzed, which proves efficiency and accuracy of the ANN based machine learning multiscale modelling strategy and the constructed GDQ based computational strategy. [ABSTRACT FROM AUTHOR]