Analysis Computer Code Research Articles

Probabilistic dynamic buckling of composite shell structures

A computationally effective method is described to evaluate the probabilistic dynamic buckling of thin composite shells. The method is a judicious combination of available computer codes for finite element, composite mechanics and probabilistic structural analysis. The solution method is an incrementally updated Lagrangian. It is illustrated by applying it to a thin composite cylindrical shell subjected to dynamic loads. Both deterministic and probabilistic buckling loads are evaluated to demonstrate the effectiveness of the method. A universal plot is obtained for the specific shell that can be used to approximate buckling loads for different loading rates and different probability levels. Results from this plot show that the faster the rate, the higher the buckling load and the shorter the time. The lower the probability, the lower the buckling load for a specific time. Probabilistic sensitivity results show that the ply thickness, the fiber volume ratio, the fiber longitudinal modulus, dynamic load and loading rate are the dominant uncertainties in that order.

The Effect of Turbine Blade Cooling on the Cycle Efficiency of Gas Turbine Power Cycles

A thermodynamic cycle analysis computer code for the performance prediction of cooled gas turbines has been used to calculate the efficiency of plants with varying combustor outlet temperature, compressor pressure ratio, and turbomachinery polytropic efficiency. It is shown that the polytropic efficiency exerts a major influence on the optimum operating point of cooled gas turbines: for moderate turbomachinery efficiency the search for enhanced combustor outlet temperature is shown to be logical, but for high turbomachinery efficiency this is not necessarily so. The sensitivity of the cycle efficiency to variation in the parameters determining the cooling flow rates is also examined. While increases in allowable blade metal temperature and film cooling effectiveness are more beneficial than improvements in other parameters, neither is as important as increase in turbomachinery aerodynamic efficiency.

Analysis and optimization of a solid oxide fuel cell and intercooled gas turbine (SOFC–ICGT) hybrid cycle

Abstract The power generation community faces a major challenge: to protect the environment while producing a plentiful supply of clean low-cost energy. “21st Century Energy Plants” (Vision 21 Plants) have been proposed and conceptualized to meet the energy and environmental challenges. The solid oxide fuel cell and intercooled gas turbine (SOFC–ICGT) hybrid cycle introduced in this work is one example of a Vision 21 Plant. The system includes an internal-reforming tubular-SOFC, an intercooled gas turbine, a humidifier, and other auxiliary components. A recently developed thermodynamic analysis computer code entitled advanced power systems analyses tools (APSAT) was applied to analyze the system performance of the SOFC–ICGT cycle. Sensitivity analyses of several major system parameters were studied to identify the key development needs and design and operating improvements for this hybrid cycle. A novel optimization strategy including a design of experiments (DOEx) approach is proposed and applied to the hybrid system. Using this optimization strategy, a system electrical efficiency higher than 75% (net ac/lower heating value (LHV)) could be achieved when the system was designed to operate under a high operating pressure (50 bara) and with a low percent excess air (EA) (55%) in the SOFC.

Efficient computation of a high-Q resonator realized by a thin-film multilayer metal/dielectric structure

We present the computer code for a full-vector analysis of the fields inside a multilayer structure with an arbitrary number of layers. The code is validated by the analysis of a microwave resonator realized with thin-film technology. The periodic boundary conditions in the multilayer structure are derived for the cavity resonator. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 48–51, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20543

Experimental and Analytical Studies on the Penetration Integrity of the Reactor Vessel Under External Vessel Cooling

Experimental and analytical studies on the penetration integrity of the reactor vessel have been performed to investigate the potential for reactor vessel failure during a severe accident in the Advanced Power Reactor 1400. Six tests have been performed to analyze the effects of the annulus water between the in-core instrumentation nozzle and the thimble tube, external vessel cooling, in-vessel pressure, melt mass, and melt flow for the maintenance of penetration integrity using alumina (Al2O3) melt as a simulant. The experimental results have been evaluated using the Lower head IntegraL Analysis computer Code (LILAC) and the Modified Bulk Freezing (MBF) model. The test results have shown that the water inside the annulus is very effective in the maintenance of the reactor vessel’s penetration integrity because the water prevents the melt from ejection through penetration. The penetration in the no external vessel cooling case has more damage than that in the external vessel cooling case. An increase in in-vessel pressure from 1.0 to 1.5 MPa did not create penetration damage, but an increase in melt mass from 40 to 60 kg and melt flow due to the vessel geometry significantly increased the amount of penetration damage. The analytical results using the LILAC computer code and the MBF model are very similar to the experimental results for the ablation depth of the weld and the melt penetration distance through the annulus, respectively.

A structural model for panel zones in non linear seismic analysis of steel moment-resisting frames

With the aim of providing a tool for the comprehensive seismic analysis of steel moment resisting frames (MRFs), the paper presents the development of a structural model which is able to describe the deformation modes of the panel zone in beam-to-columns joints, without resorting to a computationally heavy FE discretization. The model is able to take into account the finite dimensions of the joint, differently from the “scissor model” currently adopted, and can incorporate the most recently proposed constitutive models for monotonic and cyclic loading. The proposed approach, based on a simple structural representation of the joint, does not modify the centre-to-centre line scheme and the nodal degrees of freedom usually adopted in the analysis of plane frames, but adds up to five more degrees of freedom to each node. These describe the deformation modes of the panel zone, namely extensional, flexural and due to shear. A non-linear behaviour can be associated to each of these modes; based on experimental results, a simple hysteretic model is proposed for the shear deformation. The panel zone model has been implemented in an ad hoc developed computer code for the non linear seismic analysis of steel MRFs (named STEFAN, STEel Frame ANalysis), including a non-linear fracturing beam model as well. As an example of application, the dynamic behaviour of a 5-bay 9-story frame designed according to Eurocodes 3 (EC3) and 8 (EC8) has been investigated, for different panel zone stiffness and with different models, both in the linear and non linear range, emphasizing the need for a correct panel zone modelling.

비선형 지반-구조물 상호작용해석을 위한 새로운 복합법

이 논문에서는 비선형 지반-구조물 상호작용해석을 위한 새로운 시간-주파수영역 복합법을 제시하였다. 제안한 방법은 등가선형 지반-구조물 상호작용해석 프로그램과 범용 비선형 유한요소해석 프로그램을 동시에 사용하는 실용적인 방법이다. 이 방법에서는 먼저 주파수영역에서 등가선형 지반-구조물 상호작용해석을 수행하여 유한요소 영역의 경계면에서 응답을 구한 다음, 이를 범용 비선형 유한요소해석 프로그램에 의한 비선형 동적해석의 시간의존 경계조건으로 입력한다. 제안된 방법의 검증을 위하여 2차원 지하철 정거장 구조물에 대한 지진해석을 수행하였다. 이를 위하여 등가선형 지반-구조물 상호작용해석 프로그램 KIESSI-2D와 비선형 유한요소해석 프로그램 ANSYS를 사용하였다 수치적인 해석결과로부터 이 연구에서 제안한 방법의 타당성을 확인할 수 있었다. This paper presents a novel hybrid time-frequency-domain method for nonlinear soil-structure interaction(SSI) analysis. It employs, in a practical manner, a computer code for equivalent linear SSI analysis and a general-purpose nonlinear finite element program. The proposed method first (calculates dynamic responses on a truncated finite element boundary utilizing an equivalent linear SSI program in the frequency domain. Then, a general purpose nonlinear finite element program is employed to analyze the nonlinear SSI problem in the time domain, in which boundary conditions at the truncated boundary are imposed with the responses calculated in the previous frequency domain SSI analysis, In order to validate the proposed method, seismic response analyses are carried out for a 2-D underground subway station in a multi-layered half-space, For the analyses, a equivalent linear SSI code KIESSI-2D is coupled to ANSYS program. The numerical results indicate that the proposed methodology can be a viable solution for nonlinear SSI problems.

A model for droplet entrainment in heated annular flow

The ability to accurately predict droplet entrainment in annular two-phase flow is required to effectively calculate the interfacial mass, momentum, and energy transfer, which characterizes nuclear reactor safety, system design, analysis, and performance. Most annular flow entrainment models in the open literature are formulated in terms of dimensionless groups, which do not directly account for interfacial instabilities. However, many researchers agree that there is a clear presence of interfacial instability phenomena having a direct impact on droplet entrainment. The present study proposes a model for droplet entrainment, based on the underlying physics of droplet entrainment from upward co-current annular film flow that is characteristic to light water reactor safety analysis. The model is developed based on a force balance and stability analysis that can be implemented into a transient three-field (continuous liquid, droplet, and vapor) two-phase heat transfer and fluid flow systems analysis computer code.

Validation of a mathematical and numerical model for dynamic 1-D moisture content evolution in layered building elements

The paper describes the experiment conducted to validate predictions, derived by the heat and mass transfer numerical analysis computer code MA1DW, for dynamic moisture-content evolution. The tests included two samples: an autoclaved aerated concrete (AAC) and a regular concrete rendered by thermal plaster (CTP). An excellent fit was derived for temperature evolutions in both samples. A good fit was derived for the trends and general evolutions of moisture contents, with much better absolute-value approximations for the AAC samples. This demonstrated the significance of establishing reliable Design Values for material coefficients. The validation actually supplied the confidence for undertaking the further steps of development and modification of the computer code into a 2-D analysis tool.

Relationship between the fifth order aberration coefficients in electron optical deflective focusing system

Relationships between aberration coefficients up to the fifth order have been derived using symplectic conditions for a rotationally invariant electron optical deflective focusing system. These relationships show that the third and fifth order coefficients correlate and a part of the fifth order aberration coefficients can be calculated by the third order coefficients. Using these relationships, we side checked a computer code for the fifth order aberration analysis with a differential algebra method.

Coupled Vibration Analysis of Rotor and Foundation Using Quasi-Modal Transformation. 1st Report. Complex Eigenvalue Analysis.

For estimating the vibration of rotating shafts like turbine-generator sets, the rotor vibration analysis must include the vibration characteristics of the foundation. In this paper we propose a method of analyzing the vibration of a coupled rotor-foundation system. This is a quasi-modal technique based on the same concept as the well-known modal synthesis method. It provides a reduced model of an actual system using a combination of eigen modes of an inner system restricted at the bearings plus deflection modes created when inputting the load at the boundary points. A rotor system and a foundation system are each reduced using this quasi-modal technique, and the reduced models are then coupled at the bearing boundary points. Through this procedure, we developed computer code for the vibration analysis of the whole system. This code was applied to a simple model consisting of a rotor and a foundation system using several parameters. The calculated results of this coupled system proved the effectiveness of this code.

再突入回収カプセル用アブレータ材の炭化アブレーション数値解析

A computer code for charring ablation and thermal response analysis has been developed for simulation of one-dimensional transient thermal behavior of multi-layer stack of isotropic charring ablation materials used for re-entry capsules. Mathematical model of charring ablation including governing equations is summarized. Analytical solutions of several thermal response problems with or without ablation agreed very well with numerical results that are obtained with the charring ablation analysis code. Arc-heated tests of CFRP ablator models were carried out and measured results including temperature response data were compared with the simulation results of the ablation analysis code. Test results and the simulation results agreed very well. These results show that the analysis code based on the present mathematical model are available for the thermal response prediction of CFRP ablator used in the re-entry capsules such as USERS/REM.

Experiment tests and numerical simulation of double diffusive convection in isothermal three component diffusion boundaries

A computer code for the unsteady 3-dimensional analysis of convection and diffusion has been applied to the three-component system Sucrose(1)-Sodium chloride(2)-Water. Numerical results show the evolution of convective motions due to gravitational instabilities that arise as a consequence of diffusion (double diffusive convection), in agreement with theory and experiment. The evolution of convection was also observed directly and some pictures of these motions have been reported.

Relationship between fifth-order aberration coefficients in rotationallysymmetric electron optical system

Relationships between aberration coefficients up to the fifth orderhave been derived using symplectic conditions for a rotationally symmetricelectron optical system. These relationships show that the third- andfifth-order coefficients correlate and some of the fifth-order aberration coefficientscan be calculated by the third-order coefficients. Using these relationships, wecross-checked a computer code for the fifth-order aberration analysis with adifferential algebra method.

Multidimensional Deterministic Nuclear Data Sensitivity and Uncertainty Code System: Method and Application

In the nuclear industry, an increased demand exists to provide modeling results with credible confidence bounds not only for simple but also for refined modeling. With the objective to facilitate and promote such analysis, a user-friendly and complete computer code package was developed comprising the multidimensional cross-section sensitivity and uncertainty code package SUSD3D, the secondary angular distribution (SAD) covariance data-processing module ERRORR34, and the cross-section covariance matrix library ZZ-VITAMIN-J/COVA.The discrete ordinates sensitivity formulation of the first-order perturbation theory is implemented in the SUSD3D code. Much effort was devoted to mitigate some drawbacks of the discrete ordinates-based sensitivity analysis, in particular to allow the analysis of complex geometries and to reduce memory requirements. The SUSD3D code is linked via interface files to a wide range of state-of-the-art transport codes suitable for complex radiation transport and facility design studies (like ANISN, DOT-3.5, DANTSYS, DORT, and TORT) and supports the new cross-section and covariance data formats. The SAD and secondary energy distribution effects can be taken into account. The complete SAD covariance matrices, as available in the European Fusion File evaluations (EFF-2 and -3) can be treated. The computer codes are written in FORTRAN-77 and run under DOS (PC), UNIX (workstations), VMS (VAX), and other compatible operating systems.The code system is extensively used to study fission- and fusion-related problems. The validation and several practical applications of the package are presented, including the reactor pressure vessel surveillance uncertainty studies, and ASPIS-iron, VENUS-3, and FNG benchmark experiment analyses.

Modeling the viscoelastic response of GMT structural components

A glass-mat-reinforced thermoplastic (GMT) composite material has been fabricated from randomly oriented continuous glass fibers embedded in a polypropylene matrix. The mechanical constitution of this composite has been characterized by using a linear viscoelastic micromechanically based material model. This material model has subsequently been implemented to several finite-element computer codes for analysis of structural components fabricated from polypropylene GMT. In this paper several example problems have been studied in order to determine the applicability of this modeling approach to predicting time-dependent deformations due to creep in GMT components. These example problems have been solved by utilizing two commercially available codes: ABAQUS, and ANSYS. Furthermore, results obtained with the codes have been compared to both analytic and experimental results, with varying degrees of success. The paper details these results for each of the example problems considered herein.

Linear Thermoelastic Higher-Order Theory for Periodic Multiphase Materials

A new micromechanics model is presented which is capable of accurately estimating both the effective elastic constants of a periodic multiphase composite and the local stress and strain fields in the individual phases. The model is presently limited to materials characterized by constituent phases that are continuous in one direction, but arbitrarily distributed within the repeating unit cell which characterizes the material’s periodic microstructure. The model’s analytical framework is based on the homogenization technique for periodic media, but the method of solution for the local displacement and stress fields borrows concepts previously employed by the authors in constructing the higher-order theory for functionally graded materials, in contrast with the standard finite element solution method typically used in conjunction with the homogenization technique. The present approach produces a closed-form macroscopic constitutive equation for a periodic multiphase material valid for both uniaxial and multiaxial loading which, in turn, can be incorporated into a structural analysis computer code. The model’s predictive accuracy is demonstrated by comparison with reported results of detailed finite element analyses of periodic composites as well as with the classical elasticity solution for an inclusion in an infinite matrix.

Temperature dependence of composite microwave cavities

Composite microwave resonant cavities contain several regions of different dielectric materials. The variation of the resonant frequency with temperature is described in terms of a linear model. One part of the frequency variation is caused by the physical expansion of material parts, and the other by the change in the relative dielectric constant. The frequency sensitivity coefficients for both types of variation are obtained with the use of a computer code for numerical analysis of the electromagnetic field inside bodies of revolution.

The effects of processing parameters on the microstructure and mechanical properties of modified B390 alloy in direct squeeze casting

The direct squeeze casting of B390 has been investigated as a function of melt temperature and applied pressure. Commercial finite volume method (FVM) computer code for heat transfer analysis, MAGMAsoft, was used to simulate cooling curves obtained from the direct squeeze casting process. The experimental and modeling results are discussed, and the correlation between cooling rate and microstructure is studied. The effects of applied pressures and melt temperature on the formation of primary Si and Chinese scripts are also discussed in connection with mechanical properties such as hardness and tensile strength.

Static strength analysis of CANDU-6 reactor fuel bundle

A static analysis, finite-element (FE) model was developed to simulate out-reactor fuel–string strength tests with use of the well-known, structural analysis computer code ABAQUS. The FE model takes into account the deflection of fuel elements, and stress and displacement in endplates subjected to hydraulic drag loads. It was adapted to the strength tests performed for CANFLEX 43-element bundles and the existing 37-element bundles. The FE model was found to be in good agreement with experiment results. With use of the FE model, the static behavior of the fuel bundle string, such as load transfer between ring elements, endplate rib effects, hydraulic drag load incurring plastic deformation in fuel string and hydraulic flow rate effects were investigated.