Finite Element Analysis and Structural Optimization of a Vibration Feeder Based on ANSYS

Based on ANSYS software, a finite element model is built for the fatigue break of a vibration feeder influenced by an exciting force alternate load. We first study the harmonic response of the feeder and discovers the weak links which is an angle steel junction of side plate, feed inlet and the junction panel between the no-feed side plate and the bottom plate. Then, we carry out structural optimization. A streamlined method for optimum design of a vibration feeder is presented.

Finite element analysis of dynamic response and structure borne noise of gearbox

A dynamic finite element method combined with finite element mixed formula for contact problem is used to analyze the dynamic characteristics of gear system. Considering the stiffness excitation, error excitation and meshing shock excitation, the dynamic finite element model is established for the entire gear system which includes gears, shafts, bearings and gearbox housing. By the software of I-DEAS, the natural frequency, normal mode, dynamic time-domain response, frequency-domain response and one-third octave velocity grade structure borne noise of gear system are studied by the method of theoretical modal analysis and dynamic response analysis. The maximum values of vibration and structure borne noise are occurred at the mesh frequency of output grade gearing.

Finite element analysis of stress-strain localization and distribution in Al-4.5Cu-2Mg alloy

Finite element analysis has been carried out to understand the effect of various processing routes and condition on the microscale deformation behavior of Al–4.5 Cu–2 Mg alloy. The alloy has been developed through four different routes and condition, i.e. conventional gravity casting with and without refiner, rheocasting and SIMA process. The optical microstructures of the alloy have been used to develop representative volume elements（RVEs）. Two different boundary conditions have been employed to simulate the deformation behavior of the alloy under uniaxial loading. Finally, the simulated stress-strain behavior of the alloy is compared with the experimental result. It is found that the microstructural morphology has a significant impact on stress and strain distribution and load carrying capacity. The eutectic phase always carries a higher load than the α（Al） phase. The globular α（Al） grains with thinner and uniformly distributed eutectic network provide a better stress and strain distribution. Owing to this, SIMA processed alloy has better stress and strain distribution than other processes. Finally, the simulated yield strength of the alloy is verified by experiment and they have great agreement.

Finite Element Analysis of Contact Pressures between Seat Cushion and Human Buttock-Thigh Tissue

Unrelieved pressure on load-bearing muscle tissues of humans can produce pressure ulcers. In a seated upright posture, the highest pressures occur inferior to the ischial tuberosities (ITs). Moreover, the vibration can initiate the development of pressure ulcer. Therefore, the seat cushion is not only used to lower the maximum seating pressure on buttocks but also minimize the transmission of vibration to human body. The purpose of this study was to investigate the effects of varying vertical vibration frequencies on seat-interface contact pressure during sitting on three different seat cushions by using a finite element modeling approach. A simplified two-dimensional human buttock-thigh model was developed to simulate the mechanical response of the muscle of buttocks and thigh under vertical vibration. Static and vibrational loads with five different frequencies of 0.1, 1, 10, 30 and 50 Hz and the same amplitude of 3 mm were applied to different seat cushions. The result showed that the “SAF 6060” seat cushion with both hyperelastic and viscoelastic behaviors could be effective in reducing the amplitude of varying maximum contact pressure, especially for the frequency of 10-20 Hz. This method could help in design of seat cushions with appropriate material properties and shape so as to reduce vibrations transmitted to human body at a certain frequency range.

Arc-length technique for nonlinear finite element analysis

Nonlinear solution of reinforced concrete structures, particularly complete load-deflection response, requires tracing of the equilibrium path and proper treatment of the limit and bifurcation points. In this regard, ordinary solution techniques lead to instability near the limit points and also have problems in case of snap-through and snap-back. Thus they fail to predict the complete load-displacement response. The arc-length method serves the purpose well in principle, received wide acceptance in finite element analysis, and has been used extensively. However modifications to the basic idea are vital to meet the particular needs of the analysis. This paper reviews some of the recent developments of the method in the last two decades, with particular emphasis on nonlinear finite element analysis of reinforced concrete structures.

Finite Element Analysis of Vehicle Load Effect on Harvesting Energy Properties of a Piezoelectric Unit

To realize the goal of harvesting energy from pavement vibration on a large scale, a new type of piezoelectric harvesting units as the energy transducer has been proposed. The piezoelectric harvesting units are paved 40 mm below the asphalt, which is the same as thickness of the top layer of typical asphalt pavement in China. The spacing distance is 2200 mm, which is the same as the one between two tires of a normal vehicle. A mathematical model of the unit is deduced on Meda empirical formula and Hamilton principle and piezoelectric equations. Effects of the external vehicle load on its harvesting energy properties and pavement deformation and stress are analyzed with the finite element method. The results show that the excited voltage is linearly variation with contact pressure while the harvested electrical energy exponential varies with contact pressure. The more the contact pressure is, the larger the harvested electrical energy and the deformation and stress are. The harvested electrical energy also increases with the load frequency. At least 100 mJ of electrical energy can be collected with the proposed piezoelectric harvesting unit. It shows that the technology application of the piezoelectric harvesting energy from pavement is promising.

Stochastic Finite Element Analysis of Plate and Shell Construction

The response of random plate and shell construction is analyzed with the stochastic finite element method (SFEM). Random material properties and geometric dimensions of construction are involved in this paper. A simplified isoparametric local average model is used to describe the random field. Numerical results of the examples indicate that the approach presented herein is an economical and efficient solution for such an analysis compared with Monte Carlo simulation (MCS).

Vibration Response Analysis of a New Scientific Research Ship Based on Finite Element Modeling

To control the vibration level of ships under construction,MSC Software’s Patran&Nastran modeling solutions can be used to establish a detailed finite element model of a new manned submersible support mother ship based on a line drawing,including the deck layout,bulkhead section,and stiffener distribution.After a comprehensive analysis of the ship simulation conditions,boundaries,and excitation forces of the main operating equipment,modal analysis and calculation of the ship vibration can be conducted.In this study,we calculated and analyzed the vibration response of key points in the stern area of the ship’s main deck and the submersible warehouse area under design loading working conditions.We then analyzed the vibration response of typical decks(including the compass deck,steering deck,captain’s deck,forecastle deck,and main deck)under the main excitation forces and moments(such as the full swing pod and generator sets).The analysis results showed that under DESIDEP working conditions,the vibration of each deck and key areas of the support mother ship could meet the vibration code requirements of the ship’s preliminary design(using the pod excitation and generator sets).Similarly,the vibration response of a scientific research ship under other loading conditions also met the requirements of the code and provided data support for a comprehensive understanding of the ship’s vibration and noise levels.Using actual vibration measurements,the accuracy of the vibration level simulations using finite element modeling was verified,the vibration of each area of the ship comfortably meeting the requirements of the China Classification Society.

Flow, thermal, and vibration analysis using three dimensional finite element analysis for a flux reversal generator

This paper presents the simulation of major mechanical properties of a flux reversal generator （FRG） viz., computational fluid dynamic （CFD）, thermal, and vibration. A three-dimensional finite element analysis （FEA） based CFD technique for finding the spread of pressure and air velocity in air regions of the FRG is described. The results of CFD are mainly obtained to fine tune the thermal analysis. Thus, in this focus, a flow analysis assisted thermal analysis is presented to predict the steady state temperature distribution inside FRG. The heat transfer coefficient of all the heat producing inner walls of the machine are evaluated from CFD analysis, which forms the main factor for the prediction of accurate heat distribution. The vibration analysis is illustrated. Major vibration sources such as mechanical, magnetic and applied loads are covered elaborately which consists of a 3D modal analysis to find the natural frequency ofFRG, a 3D static stress analysis to predict the deformation of the stator, rotor and shaft for different speeds, and an unbalanced rotor harmonic analysis to find eccentricity of rotor to make sure that the vibration of the rotor is within the acceptable limits. Harmonic analysis such as sine sweep analysis to identify the range of speeds causing high vibrations and steady state vibration at a mode frequency of 1500 Hz is presented. The vibration analysis investi- gates the vibration of the FRG as a whole, which forms the contribution of this paper in the FRG literature.

Finite Element Analysis of the Frequency Response of a Microbubble Under Ultrasonic Field

The finite element numerical models of the microbubble with and without shell are built in our study.The calculation results indicate that the frequency response of the shell-microbubble is different from that of microbubble without shell.Furthermore,the frequency response of microbubble is closely related to the relevant parameters of the shell.The thickness and the Young's modulus willinfluence the frequency response.The increase of the thickness or the Young's modulus of the shell leads to the increase of the resonance frequency and the decrease of the oscillation amplitude of the microbubble.

Finite element response sensitivity analysis of three-dimensional soil-foundation-structure interaction (SFSI) systems

The nonlinear finite element（FE） analysis has been widely used in the design and analysis of structural or geotechnical systems.The response sensitivities（or gradients） to the model parameters are of significant importance in these realistic engineering problems.However the sensitivity calculation has lagged behind,leaving a gap between advanced FE response analysis and other research hotspots using the response gradient.The response sensitivity analysis is crucial for any gradient-based algorithms,such as reliability analysis,system identification and structural optimization.Among various sensitivity analysis methods,the direct differential method（DDM） has advantages of computing efficiency and accuracy,providing an ideal tool for the response gradient calculation.This paper extended the DDM framework to realistic complicated soil-foundation-structure interaction（SFSI） models by developing the response gradients for various constraints,element and materials involved.The enhanced framework is applied to three-dimensional SFSI system prototypes for a pilesupported bridge pier and a pile-supported reinforced concrete building frame structure,subjected to earthquake loading conditions.The DDM results are verified by forward finite difference method（FFD）.The relative importance（RI） of the various material parameters on the responses of SFSI system are investigated based on the DDM response sensitivity results.The FFD converges asymptotically toward the DDM results,demonstrating the advantages of DDM（e.g.,accurate,efficient,insensitive to numerical noise）.Furthermore,the RI and effects of the model parameters of structure,foundation and soil materials on the responses of SFSI systems are investigated by taking advantage of the sensitivity analysis results.The extension of DDM to SFSI systems greatly broaden the application areas of the d gradient-based algorithms,e.g.FE model updating and nonlinear system identification of complicated SFSI systems.

Mixed finite element and differential quadrature method for free and forced vibration and buckling analysis of rectangular plates

This paper presents a combined application of the finite element method （FEM） and the differential quadrature method （DQM） to vibration and buckling problems of rectangular plates. The proposed scheme combines the geometry flexibility of the FEM and the high accuracy and efficiency of the DQM. The accuracy of the present method is demonstrated by comparing the obtained results with those available in the literature. It is shown that highly accurate results can be obtained by using a small number of finite elements and DQM sample points. The proposed method is suitable for the problems considered due to its simplicity and potential for further development.

B-Spline Wavelet on Interval Finite Element Method for Static and Vibration Analysis of Stiffened Flexible Thin Plate

A new wavelet finite element method(WFEM)is constructed in this paper and two elements for bending and free vibration problems of a stiffened plate are analyzed.By means of generalized potential energy function and virtual work principle,the formulations of the bending and free vibration problems of the stiffened plate are derived separately.Then,the scaling functions of the B-spline wavelet on the interval(BSWI)are introduced to discrete the solving field variables instead of conventional polynomial interpolation.Finally,the corresponding two problems can be resolved following the traditional finite element frame.There are some advantages of the constructed elements in structural analysis.Due to the excellent features of the wavelet,such as multi-scale and localization characteristics,and the excellent numerical approximation property of the BSWI,the precise and efficient analysis can be achieved.Besides,transformation matrix is used to translate the meaningless wavelet coefficients into physical space,thus the resolving process is simplified.In order to verify the superiority of the constructed method in stiffened plate analysis,several numerical examples are given in the end.

Strain rate analyses during elliptical vibration cutting of Inconel 718 using finite element analysis,Taguchi method,and ANOVA

The high strain rate in metal cutting significantly affects the mechanical properties of the work piece by altering its properties.This study outlines the material strain rates during elliptical vibration cutting.The finite element analysis,Taguchi method,and analysis of variance(ANOVA)were employed to analyze the effects and contributions of cutting and vibration process parameters(feed rate,rake angle,tangential amplitude,and frequency of vibration)on the variation of strain rates during machining of Inconel 718.Taguchi signal-to-noise analysis on an L18(2^1×3^3)orthogonal array was used to determine the optimum parametric combination for the maximum strain rate,and ANOVA was applied to evaluate the significance of control parameter factors on the strain rate.The results of the finite element analysis under different conditions illustrated that the feed rate and rake angle were negatively related to the strain rate,whereas the tangential amplitude and frequency had a positive response.Furthermore,ANOVA results indicated that the effect of the feed rate,tool rake angle,vibration frequency,and tangential amplitude on the strain rate were all statistically significant,with a reliability level of 95%.Of these,the dominant parameter affecting the strain rate was the feed rate,with a percentage contribution of 40.36%.The estimation of the optimum strain rate and confirmation tests proved that the Taguchi method could successfully optimize the working conditions to obtain the desired maximum strain rate.

Vibration Analysis of Beams by Spline Finite Element

In this paper,the spline finite element method is developed to investigate free vibration problems of beams.The cubic B-spline functions are used to construct the displacement field.The assembly of elements and the introduction of boundary conditions follow the standard finite element procedure.The results under various boundary conditions are compared with those obtained by the exact method and the finite difference method.It shows that the results are in excellent agreement with the analytical results and much more accurate than the results obtained by the finite difference method,especially for higher order modes.

Seismic response comparison and sensitivity analysis of pile foundation in liquefiable and non-liquefiable soils

Case history investigations have shown that pile foundations are more critically damaged in liquefiable soils than non-liquefiable soils.This study examines the differences in seismic response of pile foundations in liquefiable and non-liquefiable soils and their sensitivity to numerical model parameters.A two-dimensional finite element(FE)model is developed to simulate the experiment of a single pile foundation centrifuge in liquefiable soil subjected to earthquake motions and is validated against real-world test results.The differences in soil-pile seismic response of liquefiable and non-liquefiable soils are explored.Specifically,the first-order second-moment method(FOSM)is used for sensitivity analysis of the seismic response.The results show significant differences in seismic response for a soil-pile system between liquefiable and non-liquefiable soil.The seismic responses are found to be significantly larger in liquefiable soil than in non-liquefiable soil.Moreover,the pile bending moment was mainly affected by the kinematic effect in liquefiable soil,while the inertial effect was more significant in non-liquefiable soil.The controlling parameters of seismic response were PGA,soil density,and friction angle in liquefiable soil,while the pile bending moment was mainly controlled by PGA,the friction angle of soil,and shear modulus of loose sand in non-liquefiable soil.

Dynamic Response Analysis of A 5 MW NREL Wind Turbine Blade under Flap-Wise and Edge-Wise Vibrations

A wind turbine is subjected to a regime of varying loads.For example,each rotor revolution causes a complete gravity stress reversal in the low-speed shaft,and there are varying stresses from the out-of-plane loading cycle due to fluctuating wind load.Consequently,wind turbine blade design is governed by fatigue rather than ultimate load considerations.Previous studies have adopted many different beam theories,using different techniques and codes,to model the National Renewable Energy Laboratory(NREL)5MWoffshore wind turbine blade.There are differences,from study to study,in the free vibration results and the dynamic response.The contribution of this study is to apply the code written by the authors to the different beam theories used with the aim of comparing the different beam theories presented in the literature and that developed by the authors.This paper reports the investigation of the effects of deformation parameters on the dynamic characteristics of the NREL 5 MW offshore wind turbine blades predicted by the different beam theories.The investigation of free vibrations is a fundamental step in the analysis of structural dynamics,and this study compares different computational structural methods and investigates their effect on the predicted dynamic response.The modal characteristics of every model examined have been combined with strip theory to determine the dynamic response of the blade.

Assessment of natural frequency of installed offshore wind turbines using nonlinear finite element model considering soil-monopile interaction

A nonlinear finite element model is developed to examine the lateral behaviors of monopiles, which support offshore wind turbines(OWTs) chosen from five different offshore wind farms in Europe. The simulation is using this model to accurately estimate the natural frequency of these slender structures, as a function of the interaction of the foundations with the subsoil. After a brief introduction to the wind power energy as a reliable alternative in comparison to fossil fuel, the paper focuses on concept of natural frequency as a primary indicator in designing the foundations of OWTs. Then the range of natural frequencies is provided for a safe design purpose. Next, an analytical expression of an OWT natural frequency is presented as a function of soil-monopile interaction through monopile head springs characterized by lateral stiffness KL, rotational stiffness KRand cross-coupling stiffness KLRof which the differences are discussed. The nonlinear pseudo three-dimensional finite element vertical slices model has been used to analyze the lateral behaviors of monopiles supporting the OWTs of different wind farm sites considered. Through the monopiles head movements(displacements and rotations), the values of KL, KRand KLRwere obtained and substituted in the analytical expression of natural frequency for comparison. The comparison results between computed and measured natural frequencies showed an excellent agreement for most cases. This confirms the convenience of the finite element model used for the accurate estimation of the monopile head stiffness.

Biomechanical Response of the Root System in Tomato Seedlings under Wind Disturbance

Wind disturbance as a green method can effectively prevent the overgrowth of tomato seedlings,and its mechanism may be related to root system mechanics.This study characterized the biophysical mechanical properties of taproot and lateral roots of tomato seedlings at five seedling ages and seedling substrates with three different moisture content.The corresponding root system-substrate finite element(FE)model was then developed and validated.The study showed that seedling age significantly affected the biomechanical properties of the taproot and lateral roots of the seedlings and that moisture content significantly affected the biomechanical properties of the seedling substrate(p<0.05).The established FE model was sensitive to wind speed,substrate moisture content,strong seedling index,and seedling age and was robust.The multiple linear regression equations obtained could predict the maximum stress and strain of the root system of tomato seedlings in the wind field.The strong seedling index had the greatest impact on the biomechanical response of the seedling root system during wind disturbance,followed by wind speed.In contrast,seedling age had no significant effect on the biomechanical response of the root system during wind disturbance.In the simulation,no mechanical damage was observed on the tissue of the seedling root system,but there were some strain behaviors.Based on the plant stress resistance,wind disturbance may affect the growth and development of the root system in the later growth stage.In this study,finite element and statistical analysis methods were combined to provide an effective approach for indepth analysis of the biomechanical mechanisms of wind disturbances that inhibit tomato seedlings’growth from the root system’s perspective.

Five-phase Synchronous Reluctance Machines Equipped with a Novel Type of Fractional Slot Winding

Multi-phase machines are so attractive for electrical machine designers because of their valuable advantages such as high reliability and fault tolerant ability.Meanwhile,fractional slot concentrated windings(FSCW)are well known because of short end winding length,simple structure,field weakening sufficiency,fault tolerant capability and higher slot fill factor.The five-phase machines equipped with FSCW,are very good candidates for the purpose of designing motors for high reliable applications,like electric cars,major transporting buses,high speed trains and massive trucks.But,in comparison to the general distributed windings,the FSCWs contain high magnetomotive force(MMF)space harmonic contents,which cause unwanted effects on the machine ability,such as localized iron saturation and core losses.This manuscript introduces several new five-phase fractional slot winding layouts,by the means of slot shifting concept in order to design the new types of synchronous reluctance motors(SynRels).In order to examine the proposed winding’s performances,three sample machines are designed as case studies,and analytical study and finite element analysis(FEA)is used for validation.