Thermal-electrical Coupled Analysis and Experimental Investigation on Spark Plasma Sintering of SiC Ceramics

Finite element simulations were conducted to study the mechanism of spark plasma sintering. The spark plasma sintering of SiC ceramics was simulated by the Marc software based on the load current curve and temperature-time curve deserved by SPS experiment. The concept of equivalent radiation coefficient was presented and applied during the simulation. The temperature distribution regularity of SiC ceramics sintered by SPS technology was got by thermal-electrical coupled finite element simulation. The experimental results show that by thermal-electrical coupled finite element analysis, the temperature rising and distribution regularity of nonconductive material can be preferable forecasted in the sintering process of SPS. In the initial stage of the heat preservation, the temperature of the central part of the sample has achieved sintering temperature, but now, the temperature of the sample is not uniform. The temperature for each part of the die is also quite different and the sample temperature in the center is higher than that in the edge. In the end of heat preservation, the central temperature of the sample is 50 ℃higher than the required sintering temperature, and the temperature gap for each part of the die decreases gradually.

Fluid-structure coupled analysis of underwater cylindrical shells

Underwater cylindrical shell structures have been found a wide of application in many engineering fields, such as the element of marine, oil platforms, etc. The coupled vibration analysis is a hot issue for these underwater structures. The vibration characteristics of underwater structures are influenced not only by hydrodynamic pressure but also by hydrostatic pressure corresponding to different water depths. In this study, an acoustic finite element method was used to evaluate the underwater structures. Taken the hydrostatic pressure into account in terms of initial stress stiffness, an acoustical fluid-structure coupled analysis of underwater cylindrical shells has been made to study the effect of hydrodynamic pressures on natural frequency and sound radiation. By comparing with the frequencies obtained by the acoustic finite element method and by the added mass method based on the Bessel function, the validity of present analysis was checked. Finally, test samples of the sound radiation of stiffened cylindrical shells were acquired by a harmonic acoustic analysis. The results showed that hydrostatic pressure plays an important role in determining a large submerged body motion, and the characteristics of sound radiation change with water depth. Furthermore, the analysis methods and the results are of significant reference value for studies of other complicated submarine structures.

Thermal-Structural Coupled Analysis of ITER Torus Cryo-Pump Housing

An ITER torus cryo-pump housing （TCPH）, which encloses a torus cryo-pump, is connected to a vacuum vessel （VV） by a set of associated double bellows. There are complicated loads due to two different operating states （pumping and regeneration） and foreseeable accidents with the cryo-pump. This paper describes a thermal-structural coupled analysis of the present TCPH according to tho allowatfle stress criteria of RCC-MR, in which the worst cases and outcomes of various load combinations are obtained. Meanwhile, optimization of the structure has been carried oul, to obtain positive analysis results and an adequate safety margin.

Elasto-plasticity and pore-pressure coupled analysis on the pullout behaviors of a plate anchor

A numerical method is proposed for the elasto-plasticity and pore-pressure coupled analysis on the pull- out behaviors of a plate anchor. The bounding-surface plasticity （BSP） model combined with Blot＇s consol- idation theory is employed to simulate the cyclic loading induced elasto-plastic deformation of the soil skeleton and the accompanying generation/dissipation of the excess pore water pressure. The suction force generated around the anchor due to the cyclic variation of the pore water pressure has much effect on the pullout capacity of the plate anchor. The calculated pullout capacity with the proposed method （i.e., the coupled analysis） gets lower than that with the conventional total stress analysis for the case of long-term sustained loading, but slightly higher for the case of short-term monotonic loading. The cyclic loading induced accumulation of pore water pressure may result in an obvious decrease of the stiffness of the soil-Plate anchor svstem.

Coupled DEM-FDM analyses of the effects of falling rock’s shape and impact angle on response of granular cushion and rock shed

Rock shed is an effective protection measure against rockfall.To investigate the influences of falling rock’s shape and impact angle on the impact effect of the cushioned rock shed,a modeling approach for a rock shed with a cushion layer using PFC-FLAC.The granular cushion is modeled as an aggregate of discrete non-cohesion particles,while the concrete plate and the beam are modeled as zones.The falling rock with different sphericities and impact angles is modeled as a rigid assembly.The numerical model is validated by comparing the simulation results with experimental and numerical results from previous literature.This model is applied to analyze the effects of rock shape and impact angle on the dynamic interaction effects between falling rock and cushioned rock shed,including the impact force,transmitted bottom force,penetration depth,and plate deflection.The numerical results show that the variation in the falling rock’s shape has different effects on the falling rock with different impact angles.These findings could support rock shed design by revealing the limitations of the assumptions in the past research,which may result in unsafe rock sheds for some rockfall cases.

RF-thermal-structural-RF coupled analysis on a travelling wave disk-loaded accelerating structure

The travelling wave （TW） disk-loaded accelerating structure is one of the key components in normal conducting （NC） linear accelerators, and has been studied for many years. In the design process, usually after the dimensions of each cell and the two couplers are finalized, the structure is fabricated and tuned, and then the whole structure RF characteristics are measured by using a vector network analyzer. Before fabrication, the whole structure characteristics （including RF, thermal and structural ones） are less simulated due to the limited capability of currently available computers. In this paper, we described a method for performing RF-thermal-structural-RF coupled analysis on a TW disk-loaded structure using only one PC. In order to validate our method, we first analyzed and compared our RF simulation results on the 3 m long BEPC Ⅱ structure with the corresponding experimental results, which shows very good consistency. Finally, the RF-thermal-structure-RF coupled analysis results on the 1.35 m long NSC KIPT linac accelerating structure are presented.

Coupled pile soil interaction analysis in undrained condition

The effective stress method is developed to predict the axial capacity of piles in clay. The effective stress state changes due to the resulting pore pressure change and therefore, the strength and stiffness of the soil will change. In this work, the finite element method is utilized as a tool for the analysis of pile-soil systems in undrained condition. The computer program CRISP was developed to suit the problem requirements. CRISP uses the finite element technique and allows predictions to be made of ground deformation using critical state theories. Eight-node isoparametric element was added to the program in addition to the slip element. A pile loading problem was solved in which the pile-soil system is analyzed in undrained condition. The pile is modelled as elastic-plastic material, while the soil is assumed to follow the modified Cam clay model. During undrained loading condition, the settlement values increase by 22% when slip elements are used. The surface settlement increases by about three times when the load is doubled and the surface settlement at all points increases when using slip elements due to the mode of motion which allows smooth movement of the adjacent soil with respect to the pile. The vertical displacement increases as the distance decreases from the pile and negligible values are obtained beyond 10D (where D is the pile diameter) from the center of the pile and these values are slightly increased when slip elements are used. The vertical effective stress along a section at a distance D from the pile center is approximately the same for all load increments and lower values of effective vertical stress can be obtained when slip elements are used.

Uncertainty assessment in hydro-mechanical-coupled analysis of saturated porous medium applying fuzzy finite element method

The purpose of the present study was to develop a fuzzy finite element method,for uncertainty quantification of saturated soil properties on dynamic response of porous media,and also to discrete the coupled dynamic equations known as u-p hydro-mechanical equations.Input parameters included fuzzy numbers of Poisson's ratio,Young's modulus,and permeability coefficient as uncertain material of soil properties.Triangular membership functions were applied to obtain the intervals of input parameters in five membership grades,followed up by a minute examination of the effects of input parameters uncertainty on dynamic behavior of porous media.Calculations were for the optimized combinations of upper and lower bounds of input parameters to reveal soil response including displacement and pore water pressure via fuzzy numbers.Fuzzy analysis procedure was verified,and several numerical examples were analyzed by the developed method,including a dynamic analysis of elastic soil column and elastic foundation under ramp loading.Results indicated that the range of calculated displacements and pore pressure were dependent upon the number of fuzzy parameters and uncertainty of parameters within equations.Moreover,it was revealed that for the input variations looser sands were more sensitive than dense ones.

Nonlinear Coupled Dynamics Analysis of A Truss Spar Platform

Accurate prediction of the offshore structure motion response and associate mooring line tension is important in both technical applications and scientific research. In our study, a truss spar platform, operated in Gulf of Mexico, is numerically simulated and analyzed by an in-house numerical code ＇COUPLE＇. Both the platform motion responses and associated mooring line tension are calculated and investigated through a time domain nonlinear coupled dynamic analysis. Satisfactory agreement between the simulation and corresponding field measurements is in general reached, indicating that the numerical code can be used to conduct the time-domain analysis of a truss spar interacting with its mooting and riser system. Based on the comparison between linear and nonlinear results, the relative importance of nonlinearity in predicting the platform motion response and mooring line tensions is assessed and presented. Through the coupled and quasi-static analysis, the importance of the dynamic coupling effect between the platform hull and the mooting/riser system in predicting the mooting line tension and platform motions is quantified. These results may provide essential information pertaining to facilitate the numerical simulation and design of the large scale offshore structures.

Design and Coupled Thermo-Mechanical Analysis of Silicon Carbide Primary Mirror Assembly

Based on the principle that the thermal expansion coefficient of the support structure should match that of the mirror, three schemes of primary mirror assembly were designed. Of them, the first is fused silica mirror plus 4J32 flexible support plus ZTC4 support back plate, the second K9 mirror plus 4J45 flexible support plus ZTC4 support back plate, and the third SiC mirror plus SiC rigid support back plate. A coupled thermo-mechanical analysis of the three primary mirror assemblies was made with finite element method. The results show that the SiC assembly is the best of all schemes in terms of their combination properties due to its elimination of the thermal expansion mismatch between the materials. The analytical results on the cryogenic property of the SiC primary mirror assembly show a higher surface finish of the SiC mirror even under the cryogenic condition.

Coupled Dynamics and Integrated Control for Position and Attitude Motions of Spacecraft:A Survey

Inspired by the integrated guidance and control design for endo-atmospheric aircraft,the integrated position and attitude control of spacecraft has attracted increasing attention and gradually induced a wide variety of study results in last over two decades,fully incorporating control requirements and actuator characteristics of space missions.This paper presents a novel and comprehensive survey to the coupled position and attitude motions of spacecraft from the perspective of dynamics and control.To this end,a systematic analysis is firstly conducted in details to show the position and attitude mutual couplings of spacecraft.Particularly,in terms of the time discrepancy between spacecraft position and attitude motions,space missions can be categorized into two types:space proximity operation and space orbital maneuver.Based on this classification,the studies on the coupled dynamic modeling and the integrated control design for position and attitude motions of spacecraft are sequentially summarized and analyzed.On the one hand,various coupled position and dynamic formulations of spacecraft based on various mathematical tools are reviewed and compared from five aspects,including mission applicability,modeling simplicity,physical clearance,information matching and expansibility.On the other hand,the development of the integrated position and attitude control of spacecraft is analyzed for two space missions,and especially,five distinctive development trends are captured for space operation missions.Finally,insightful prospects on future development of the integrated position and attitude control technology of spacecraft are proposed,pointing out current primary technical issues and possible feasible solutions.

Thermal-Mechanical Coupled FE Analysis for Rotary Shaft Seals

The aim of this paper is to model the steady-state condition of a rotary shaft seal (RSS) system. For this, an iterative thermal-mechanical algorithm was developed based on incremental finite element analyzes. The behavior of the seal’s rubber material was taken into account by a large-strain viscoelastic, so called generalized Maxwell model, based on Dynamic Mechanical Thermal Analyses (DMTA) and tensile measurements. The pre-loaded garter spring was modelled with a bilinear material model and the shaft was assumed to be linear elastic. The density, coefficient of thermal expansion and the thermal conductance of the materials were taken into consideration during simulation. The friction between the rotary shaft seal and the shaft was simplified and modelled as a constant parameter. The iterative algorithm was evaluated at two different times, right after assembly and 1 h after assembly, so that rubber material’s stress relaxation effects are also incorporated. The results show good correlation with the literature data, which state that the permissible temperature for NBR70 (nitrile butadiene rubber) material contacting with ~80 mm shaft diameter, rotating at 2600/min is 100°C. The results show 107°C and 104°C for the two iterations. The effect of friction induced temperature, changes the width of the contact area between the seal and the shaft, and significantly reduces the contact pressure.

Static and Dynamic Analysis of Lasing Action from Single and Coupled Photonic Crystal Nanocavity Lasers

The single and coupled photonic crystal nanocavity lasers are fabricated in the InGaAsP material system and their static and dynamic features are compared. The coupled-cavity lasers show a larger lasing e^ciency and generate an output power higher than the single-cavity lasers, results that are consistent with the theoretical results obtained by rate equations. In dynamic regime, the single-cavity lasers produce pulses as short as 113 ps, while the coupled-cavity lasers show a significantly longer lasing duration. These results indicate that the photonic crystal laser is a promising candidate for the light source in high-speed photonic integrated circuit.

Coupling Analysis of Tourism Development and Rural Revitalization in Yannanfei Tea Field Resort of Guangdong Province

By deconstructing the dimensions of rural tourism and rural revitalization and constructing a coupled conceptual model,a coupled evaluation model is constructed.Yannanfei Tea Field Resort in Guangdong is taken as a research case for empirical analysis,to explore the coupled development trend of the two.The results show that①the tourism development of Guangdong Yannanfei Tea Field Resort has a good synergistic relationship with rural revitalization.The two complement and promote each other,and rural tourism has significantly promoted the development of rural revitalization.②The coupling development of tourism development and rural revitalization in Guangdong Yannanfei Tea Field Resort is divided into coupling imbalance period and coupling coordination period.The results indicate that the coordination between the two has not yet reached a level of good coordination and high-quality coordination.It is recommended that the resort should fully utilize the opportunity of rural revitalization strategy,increase investment in rural tourism,promote the transformation and upgrading of the resort,impel the integration of tea and tourism,and develop new business model of tea-tourism rural vacation.

Numerical analysis of coupled sloshing and motion of a cylindrical FPSO in regular waves

In this paper,the coupled sloshing and motion characteristics of a cylindrical floating production storage offloading(CFPSO)are numerically investigated by means of computational fluid dynamics(CFD)tool.The simulations are performed using an in-house CFD solver naoe-FOAM-SJTU which is developed based on OpenFOAM.The active wave generating-absorbing boundary condition(GABC)is utilized for wave generation and absorption.The stabilized k-omega SST turbulence model are used to avoid excessive eddy viscosity near the free surface.CFPSO with and without partially filled liquid tanks in regular waves with different wave periods are simulated and vertical planar motions such as surge,heave and pitch response amplitude operators(RAOs)are compared.Forces due to liquid sloshing and wave loads are extracted and analyzed.The free surface motions inside liquid tanks in one wave period presented to explain the motion characteristics.

Vibration Reduction by a Partitioned Dynamic Vibration Absorber with Acoustic Black Hole Features

Vibration quality is a vital indicator for assessing the progress of modern equipment.The dynamic vibration absorber(DVA)based on the acoustic black hole(ABH)feature is a new passive control method that manipulates waves.It offers efficient energy focalization and broad-spectrum vibration suppression,making it highly promising for applications in large equipment such as aircraft,trains,and ships.Despite previous advancements in ABH-DVA development,certain challenges remain,particularly in ensuring effective coupling with host structures during control.To address these issues,this study proposes a partitioned ABH-featured dynamic vibration absorber(PABH-DVA)with partitions in the radial direction of the disc.By employing a plate as the host structure,simulations and experiments were conducted,demonstrating that the PABH-DVA outperforms the original symmetric ABH-DVA in terms of damping performance.The study also calculated and compared the coupling coefficients of the two ABH-DVAs to uncover the mechanism behind the enhanced damping.Simulation results revealed that the PABH-DVA exhibits more coupled modes,occasionally with lower coupling coefficients than the symmetric ABH-DVA.The influence of frequency ratio and modal mass was further analyzed to explain the reasons behind the PABH-DVA's superior damping performance.Additionally,the study discussed the impact of the number of slits and their orientation.This research further explains the coupling mechanism between the ABH-DVA and the controlled structure,and provides new ideas for the further application of ABH in engineering.

Fully Coupled Effects of Hull,Mooring and Risers Model in Time Domain Based on An Innovative Deep Draft Multi-Spar

The coupled hull, mooring and riser analysis techniques in time domain are widely recognized as the unique approach to predict the accurate global motions. However, these complex issues have not been perfectly solved due to a large number of nonlinear factors, e.g. forces nonlinearity, mooring nonlinearity, motion nonlinearity and so on. This paper investigates the coupled effects through the numerical uncoupled model, mooring coupled model and fully coupled model accounting mooring and risers based on a novel deep draft multi-spar which is especially designed for deepwater in 2009. The numerical static-offset, free-decay, wind-action tests are executed, and finally three hours simulations are conducted under 100-year return period of GOM conditions involving wave, wind and current actions. The damping contributions, response characteristics and mooring line tensions are emphatically studied.

Numerical analysis of ossicular chain lesion of human ear

Abstract Lesion of ossicular chain is a common ear disease impairing the sense of hearing. A comprehensive numerical model of human ear can provide better understanding of sound transmission. In this study, we propose a three-dimensional finite element model of human ear that incorporates the canal, tympanic membrane, ossicular bones, middle ear suspensory ligaments/muscles, middle ear cavity and inner ear fluid. Numerical analysis is conducted and employed to predict the effects of middle ear cavity, malleus handle defect, hypoplasia of the long process of incus, and stapedial crus defect on sound transmission. The present finite element model is shown to be reasonable in predicting the ossicular mechanics of human ear.

Cavity noise sensitivity analysis of tire contour design factors and application of contour optimization methodology

Cavity resonance noise of passenger car tires is generated by interacting excitation between a tire structure and the fill gas (air), and generally lies in a frequency range of 200?250 Hz. As such, this noise is strongly perceived and may be a serious source of driver annoyance. Thus, many studies regarding the cavity noise mechanism and its reduction have already been conducted. In this work, a vibro-acoustic coupled analysis was conducted between a tire structure and air cavity. Using this analysis, we can more accurately simulate the tire noise performance in the region of the cavity resonance frequency. An analysis of the effects of variation of tire contour design factors was conducted, using design-of-experiments methods. Finally, a multi-objective optimization was performed using in-house codes to reduce the cavity noise level while minimizing the loss of other performances, such as diminished ride comfort and handling caused by the variations of contour. As a result of this optimization, an optimized contour shape was derived, which satisfied the multi-objective performances.