Actual Boundary Conditions Research Articles

Analysis of the low-frequency magnetoelectric performance in three-phase laminate composites with Fe-based nanocrystalline ribbon

The theoretical analysis of magnetoelectric (ME) performance in three-phase Terfenol-D/PZT/FeCuNbSiB (MPF) laminate composite is presented in this paper. The ME couplings at low frequency for ideal and less than ideal interface couplings are studied, respectively, and our analysis predicts that (i) the ME voltage coefficient for ideal interface coupling increases with the increasing layers (n) of Fe-based nanocrystalline ribbon FeCuNbSiB (Fe73.5Cu1Nb3Si13.5B9) while the sizes of PZT (Pb(Zr1−xTix)O3) and Terfenol-D (Tb1−xDyxFe2−y) are kept constant, and then it tends to be a constant when the layers of FeCuNbSiB are >100; (ii) by introducing the interface coupling factor k and considering the degradation of d33m,f with n, the ME voltage coefficient for a less than ideal interface condition is predicted. As the FeCuNbSiB layer increases, it first increases and reaches to a maximum value, and then slowly decreases. Various MPF laminates are fabricated and tested. It is found that the theoretical predictions for the consideration of actual boundary conditions at the interface are in agreement with the experimental observations. This study plays a guiding role for the design of MPF composite in real applications.

Finite Element Analysis for Wave Spring of Multi-Disc Wet Clutch Based on ANSYS

Wave spring is a key component of multi-disc wet clutch and the response speed and running quality of multi-disc wet clutch is affected by its characteristics. This paper analyses the theoretical calculation of load-deformation relationship of wave spring. The load-deformation relationship of wave spring is obtained by ANSYS10.0 software according to its structural characteristics and actual boundary condition and compared with the calculated results based on different methods and the measured value, and then study the effect of the wave number on the load-deformation relationship of wave spring. The results show that the calculated value of finite element analysis (FEM) is closer to the measured value and the FEM has more advantages on simulation of the working performance of wave spring.

CFD ANALYSIS OF ECONOMIZER IN A TENGENTIAL FIRED BOILER

This paper presents a simulation of the economizer zone, which allows for the condition of the shell-side flow and tube-side and tube-wall, thermal fields, and of the shell-tube heat-exchange. Selection of the economizer zone from the thermal power plant only because, it is found trends of failure that the economizer is the zone where the leakages are found more. The maximum number of cause of failure in economizer unit is due to flue gas erosion. The past failure details revels that erosion is more in U-bend areas of Economizer Unit because of increase in flue gas velocity near these bends. But it is observed that the velocity of flue gases surprisingly increases near the lower bends as compared to upper ones. The model is solved using conventional CFD techniques by STAR- CCM+ software. In which the individual tubes are treated as sub-grid features. A geometrical model is used to describe the multiplicity of heat-exchanging structures and the interconnections among them. The Computational Fluid Dynamics (CFD) approach is utilised for the creation of a three-dimensional model of the economizer coil. With equilibrium assumption applied for description of the system chemistry. The flue gas temperature, pressure and velocity field of fluid flow within an economizer tube using the actual boundary conditions have been analyzed using CFD tool. Such as the ability to quickly analyse a variety of design options without modifying the object and the availability of significantly more data to interpret the results. This study is a classic example of numerical investigation into the problem of turbulent reacting flows in large scale furnaces employed in thermal power plants for the remediation of ash deposition problems. And the experimental setup is from Chandrapur Super Thermal Power Station, Chandrapur having the unit no IV of 210 MW energy generations.

CFD Analysis of Temperature Distribution in Can-Type Combustor Firing Synthetic Gas

This paper presents CFD analysis of the effect of syngas combustion in a full scale gas turbine combustor with specific emphasis given to the flame and flue gas temperature distribution. A base case solution was first established using conventional natural gas combustion. Actual operating boundary conditions such as swirl, diffusion and fuel mass flow were imposed on the model. The simulation result is validated with the flame temperature of typical natural gas combustion. Result from flow and combustion calculation shows reasonable trend of the swirl mixing effect. The maximum flame temperature was found to be the highest for syngas with the highest H2/CO ratio. However, the flue gas temperature was found to be approximately identical for all cases. The prediction of temperature distribution in the combustor would enable further estimation of pollutant species such as CO2 and NOx in complex regions within the combustor.

Couplonics Of Cyclic Ternary Systems: From Coupled Periodic Waveguides To Discrete Photonic Crystals

In the context of coupled periodic waveguides, "couplonics" refers to the rigorous equivalence between continuous wave coupling and localized interactions. We extend it here to a cyclic ternary system, looked upon as the simplest discrete photonic crystal with actual periodic boundary conditions. A linear decomposition on a supermode basis enables one to reduce the original sixwave problem to three independent two-wave distributed Bragg reflectors (or 1D PC).

Impact damage on a thin glass plate with a thin polycarbonate backing

We present experimental and computational results for the impact of a spherical projectile on a thin glass plate with a thin polycarbonate backing plate, restrained in a metal frame, or in the absence of the frame. We analyze the dependence of the damage patterns in the glass plate on the increasing impact velocities, from 61 m/s to 200 m/s. Experimental results are compared with those from peridynamic simulations of a simplified model. The main fracture patterns observed experimentally are captured by the peridynamic model for each of the three projectile velocities tested. More accurate implementation of the actual boundary conditions present in the experiments will likely further improve modeling of brittle damage from impact on a multi-layered system. The peridynamic computational model sheds light into the early stages of the complex brittle damage evolution in the glass layer, and the influence of boundary conditions on the dynamic fracture process.

Computation of Thermal-Stresses and Contraction Joint Distance of RCC Dams

A new approach in 3D numerical modeling for unsteady phased thermal-stress analysis of a massive concrete hydraulic structure is presented. The temperature field is computed first, providing a drive for the unsteady, nonlinear, viscoelastic, stress-strain analysis. This model is devised with actual initial and boundary conditions, appropriate material properties, and the observed concrete placement schedule. The verification is based on the field investigations of the Platanovryssi dam. The results of a long-term analysis have shown close agreement with the observed dam conditions. The proposed model presents a reliable tool for thermal-stress computation and transverse contraction joint distance evaluation.

Performance of the Boiler and To Improving the Boiler Efficiency Using Cfd Modeling

The power sector is one of the sectors of the India's economy. The development of the country to a large extent is dependent on the growth of this sector. Through the progress of the power sector during the past four decades has been sustainable, the power industry has been unable to fulfill primary obligation of production quality power supply in required quantity. We did our project in Stage- 4, Unit -7 of Dr. Narla Tata Rao Thermal Power Station, Vijayawada and analyzed the performance of the boiler of the above-mentioned unit of capacity 500MW. Our project was mainly concerned with the Boiler Operations & Maintenance Department (O&M). Initially, we calculated the performance and efficiency of the boiler. The Computational Fluid Dynamics (CFD) approach is utilised for the creation of a two-dimensional model of the economizer coil. Using mild steel material in the economizer part it gives better performance compared with the carbon steel material. The fluid flow temperature, pressure is increase and velocity is decrease field of fluid flow within an economizer tube using the actual boundary conditions have been analyzed using CFD tool. So the boiler performance will be increased. And the experimental setup is from Dr. NTTPS, Vijayawada having the unit no IV of 500 MW energy generations.

Finite Element Analysis of Curvature Precast Polymer Panel for Temporary Support of Tunnels

In the past few decades, underground railway systems as one of the accepted transportation system have become an integral part of populated cities, and consequently developing advanced structure to speed up the tunnels construction process become vital. Ceiling collapse is defined as the major failure in construction of tunnels that need to be concerned to prevent any hazardous on workers. Sprayed Concrete (SC) is the traditional structure that has been used for temporary support of tunnels under construction process. The disadvantages of SC such as tough preparation and installation process that is also time consuming procedure, is caused a necessary need to design new structure to be replaced by traditional cases. This study is concentrated on design and mechanical analysis of curvature polymer panel to be replaced by SC in tunnels. For this reason, Hard Density Polyethylene (HDPE) Polymer is selected due to its specific mechanical features such as high strength and stiffness to weight ratio. The tests of compression and tension are performed to extract the material properties and mechanical behaviour of HDPE polymer. A good study is done on mechanics of polymer materials to select an appropriate model accurate enough to model HDPE polymer. YEOH model is selected and utilized in Finite Element Analysis (FEA) using ABAQUS 6.9EF. Explicit Dynamic (ED) Procedure is used to simulate the hyperelastic deformation of HDPE polymer structures. The mathematical model and computational procedure are validated using simulation results of a three-dimensional (3D) model of a cubic HDPE polymer under compression load that compared well with experimental data. The established simulation procedure has applied on the proposed model of curvature HDPE polymer structure for temporary supports of tunnels. The actual loading and boundary condition in tunnels are tried to apply on the structure and the model is ran using FEM and ED procedure. The flexural strength response of structure is plotted as load-deflection curve to show the stiffness that can be tolerated with the curvature structure. A complete discussion is given on stress and hyperelastic deformation of the structure. The results are illustrating the advantage and disadvantage of designed structure and the possibility of utilize polymer materials in tunnelling process. The computational procedure is strongly recommended for design and analysis of polymer structures for different engineering application.

Identification of the Out-of-Plane Shear Modulus of a 3D Woven Composite

This study deals with the identification of macroscopic elastic parameters of a layer-to-layer interlock woven composite from a full-field measurement. As this woven composite has a coarse microstructure, the characteristic length of the weaving is not small as compared to the specimen size. A procedure based on an inverse identification method and full-field digital image correlation kinematic measurement is proposed to exploit a three-point bending test on short coupons to characterize the out-of-plane shear modulus. Each step of the proposed procedure is presented, and their respective uncertainty is characterized with the help of numerical simulations. The shear modulus is identified with an accuracy of about 1.5 % and is 15 % lower than the estimate obtained through Iosipescu tests. The proposed procedure shows a correlation between the ideal mesh size and the weaving period. It also reveals that the actual boundary conditions deviate from the ideal ones and hence a special attention is paid to their optimization.

Measuring shallow water flow velocity with virtual boundary condition signal in the electrolyte tracer method

Summary Accurate measurement of hill-slope shallow water flow velocity is an important issue in soil erosion prediction. The pulse model of electrolyte tracer advanced by Lei et al. (2005) indicated that the boundary condition is critical for accurate velocity measurement. To improve the measurement accuracy, Lei et al. (2010) improved the method by employing practically measured boundary condition instead of the pulse assumption, by an additional sensor close to the electrolyte injection location. The measurement precision was improved significantly as compared with that by the pulse model. However, the measured boundary condition is not the actual boundary condition, which may still cause errors in the measured velocities. The sensor for boundary measurement can otherwise be used to measure flow velocity if it can be rationally determined without measurement. In this study, modifications are made to the previous methods. The boundary condition is not measured by an additional sensor but is determined by fitting the model to the experimental data so as to determine virtual/real boundary condition (Virtual B.C.) at its actual position and the flow velocity simultaneously. The measured velocities and the estimated boundary condition are verified using the experimentally measured data involved three flow rates (12, 24 and 48 L min−1), three slope gradients (4°, 8° and 12°) and six measurement positions (0.05, 0.3, 0.6, 0.9, 1.2, and 1.5 m). The newly-proposed Virtual B.C. method improved the measurement precision of velocities as compared with those by the previous methods. An additional experimental data set is used for sensitivity analysis. This experiment involves three flow rates (12, 24 and 48 L min−1), three slope gradients (4°, 8° and 12°), four measurement positions (0.3, 0.6, 0.9, and 1.2 m), and three electrolyte injection durations (0.2, 0.3, and 0.4 s). The sensitivity analysis on measured velocity indicates that the Virtual B.C. method shows significant advantage of stability, regardless of electrolyte injection duration. The improvement is relatively more significant for shorter distance measurement and shorter electrolyte injection duration. The results are very encouraging to claim that the improved method is sound for short distance measurement and for portable instrument development.

Effects of flux boundary conditions on pore-water pressure distribution in slope

Many geotechnical analyses commonly ignore the flux boundary conditions at the ground surface to avoid the complexity in determining the actual flux values at the soil-atmosphere interface. However, actual flux boundary conditions can be an important input to many geotechnical analyses, especially those related to unsaturated soils. Therefore, the effects of flux boundary conditions on pore-water pressure distribution in a residual slope are investigated in this paper. The study focuses on infiltration and evaporation processes. The characterization of climatic data in Singapore is presented in this paper to illustrate the quantification of flux boundary conditions. Evaporation rate for the seepage analyses is calculated using Penman's method. The classification of Singapore climate is carried out using Thornthwaite index.The typical differences between air and soil temperatures in Singapore are presented in this paper using case study from a residual soil slope at Yishun, Singapore. Finite element seepage analyses were conducted to investigate the effect of rainwater infiltration and evaporation on pore-water pressure distribution of a residual soil slope at Jalan Kukoh, Singapore. The numerical analysis results show good agreement with those obtained from field measurements if the evaporation is applied in the analyses during the drying process. This indicates that rainfall and evaporation play important roles in pore-water pressure changes within soil slope.

Power flows between strongly coupled structural components

In this study, the energy distributions and power flows between some basic structural components such as beams, plates, and shells are studied using a so-called Fourier Spectral Element Method (FSEM). Similar to the SEA modeling, a complex system is here also considered as an assembly of subsystems or components. The FSEM, however, is deterministic in nature in that the solution is obtained by directly and faithfully solving the governing equations for each component under the actual boundary and coupling conditions. What make this model powerful and unique lie in its capability and flexibility of effectively dealing with model uncertainties (due to the probabilistic/stochastic natures of some model parameters) and engineering and manufacturing errors which tend to become critically important at higher frequencies. Since this method does not involve any artificial assumptions or simplifications, it potentially offers a whole frequency solution with adaptive spatial and frequency resolutions.

Analysis of Temperature Field of Concrete Box Girder and Secondary Development of Program

Taking a two-lane bridge as the background, accurate gradient mode of wall temperature for concrete box girder has been summed up in this paper, based on the comparative analysis between temperature field numerical simulation according to the heat exchange equilibrium theory of prestressed box girder and field measurement. Comparative analysis shows that, this type of numerical simulation of temperature field can objectively reflect the actual boundary conditions with high accuracy, and can meet the requirements of practical design and analysis in engineering well. Then visual module for the analysis of temperature field for pre-stressed concrete is developed, with the same style as ANSYS, taking advantage of second development of ANSYS. Example shows that, the visual module can be well applied in practice, improving efficiency.

Prediction of Full Field Dynamic Strain from Limited Sets of Measured Data

Dynamic response is an important consideration for design of structures due to operating or occasional loadings. The resulting dynamic stress strain is also of concern for fatigue and structural health monitoring. Typically, the actual loading and structural condition (boundary conditions, environmental condition, geometry, mechanical properties, etc.) are not necessarily known. Much effort is expended in attempting to identify the loads and appropriate model for prediction of these types of events. At best, the forces and actual boundary conditions are approximate and have an effect on the overall predicted response and resulting stress-strain that is identified for subsequent evaluation.Experimental data can only be obtained from limited sets of points, such as those typically collected with accelerometers. These are normally used in the evaluation the state of a structure in service condition. More recently, Digital Image Correlation (DIC) and Dynamic Photogrammetry (DP) have become very important techniques to measure the surface response. These are non-contact and full-field techniques, which allow that much more simultaneous data to be measure. The sets of limited surface data that are collected can be used in conjunction with an expansion algorithm to obtain full field information. The finite element model mass and stiffness matrices are used to obtain the normal constitutive relations as well as the modal characteristics. This information is used to develop the expansion algorithm and for the stress recovery during the back substitution process typically employed.

Extended Identification of Mechanical Parameters and Boundary Conditions by Digital Image Correlation

This paper represents a further contribution to the study of identification procedures for material mechanics resting on kinematic measurements provided by 2D Digital Image Correlation (DIC) at the microscale. Reference is made to non-conventional experiments on adhesively bonded assemblies industrially manufactured for aerospace applications. For calibration purposes a local approach is considered under plane stress conditions, focusing on a small sub-domain on the sample surface, in which mixed mode debonding is monitored. As a novelty, both the (cohesive) mechanical parameters of the interface and the actual boundary conditions prescribed at different time instants during the test are considered as unknowns to be estimated on the basis of full-field data. In this way, data smoothing and parameter identification procedures, so far usually performed in a sequence, are tackled simultaneously in a coupled framework. Since the inverse problem generalized as mentioned above turns out to be severely ill-posed, suitable regularizing provisions are applied, concerning the a priori regularity of (kinematic) displacement fields, from which boundary data are sampled, and the equilibrium (Neumann) conditions along the cracked part of the interface.

Application of Contact Analysis in Strength Analysis of Helicopter Transmission System

Taking the strength analysis of the tail rotor transmission system for one type helicopter as an example, the implicit nonlinear finite element contact analysis was taken to the control arms and flange of the tail rotor pitch control system using MSN/NASTRAN in this paper. It was pointed out that rightly modeling the actual load and boundary conditions of components is essential in the strength analysis of the transmission system.

Instability of equilibrium of evolving laminates in pseudo-elastic solids

This study is concerned with isothermal stability of equilibrium of evolving laminated microstructures in pseudo-elastic solids with a multi-well free energy function. Several possible modes of instability associated with phase transition between energy wells are analysed. The related rate-independent dissipation is included by imposing a threshold value on the thermodynamic driving force. For a homogenized phase-transforming laminate with no length scale it is shown that localization instability is a rule in case of a non-zero interfacial jump of a directional nominal stress, irrespectively of actual boundary conditions. A stabilizing effect of elastic micro-strain energy at the boundary of the localization zone is demonstrated for laminates of finite spacing. Illustrative numerical examples are given for an evolving austenite–martensite laminate in a crystal of CuZnAl shape memory alloy.

Special Section on Landslides: Setting the Scene and Outline of Contributing Studies

The guest editors introduce the special section on landslides, including each of the contributions and implications for future research. Advances in our understanding will involve multidisciplinary research and applications with the goal of preventing damage to infrastructure and the environment.

A topological optimization method for flexible multi-body dynamic system using epsilon algorithm

In a flexible multi-body dynamic system the typical topological optimization method for structures cannot be directly applied, as the stiffness varies with position. In this paper, the topological optimization of the flexible multi-body dynamic system is converted into structural optimization using the equivalent static load method. First, the actual boundary conditions of the control system and the approximate stiffness curve of the mechanism are obtained from a flexible multi-body dynamical simulation. Second, the finite element models are built using the absolute nodal coordination for different positions according to the stiffness curve. For efficiency, the static reanalysis method is utilized to solve these finite element equilibrium equations. Specifically, the finite element equilibrium equations of key points in the stiffness curve are fully solved as the initial solution, and the following equilibrium equations are solved using a reanalysis method with an error controlled epsilon algorithm. In order to identify the efficiency of the elements, a non-dimensional measurement is introduced. Finally, an improved evolutional structural optimization (ESO) method is used to solve the optimization problem. The presented method is applied to the optimal design of a die bonder. The numerical results show that the presented method is practical and efficient when optimizing the design of the mechanism.