Applied Mechanics and Materials Vol. 431

Abstract: In sodium cooled fast breeder reactors, the high operating temperature necessitates hardfacing of grid plate to avoid galling of the base material. Nickel based cobalt-free alloy called Colmonoy-5 has been chosen as the hard facing material for the Prototype Fast Breeder Reactor (PFBR) grid plate. The grid plate (GP) which is a critical component made of SS316 that holds the core subassemblies are hard faced, to prevent galling caused by subassembly insertion/removal and erosion due to high sodium velocity at 670 K. Colmonoy 5 was hardfaced on circular grid plate along the annular groove by Plasma Transferred Arc Welding (PTAW). The process-induced residual stress generated due to difference in coefficients of thermal expansion between the deposit and substrate material was removed by annealing. In this paper, in order to evaluate Stress Intensity Factor (SIF) near the crack tip of the crack caused by the remote load or residual stresses generated due to thermal cycling owing to on/off of nuclear reactor, a grid plate model hard-faced with colmonoy 5 was prepared and then annealed to remove process-induced residual stress. Considering the plane strain condition to the same geometry of the model, a 3mm crack was considered at the vertical interface between the steel and the colmonoy. By supporting the specimen on the left and right corners of the upper side, load was applied exactly on the opposite side of crack in the positive direction, simulating mode I loading. After loading the model and getting the solution, K_I was obtained at the crack tip. This step was repeated for various loads to obtain the relationship between SIF and load for fracture characteristics.

Abstract: The vibration and sound radiation characteristics of laminated composite flat-panel sound radiators are studied via both theoretical and experimental approaches. In the theoretical study, a finite element model is presented to formulate the forced vibration of the sound radiators. The first Rayleigh integral is used to construct the sound pressure level curve of the sound radiators. In the experimental study, a laminated composite sound radiator was subjected to sweep sine excitation to determine the frequency response spectrum from which the natural frequencies of the sound radiator were identified. The sound radiator with salt powder distributed on its top surface was excited to generate the vibration shapes of the sound radiator at several selected frequencies. The SPL curve of the sound radiator was also measured experimentally. The experimental results are then used to verify the feasibility and accuracy of the proposed finite element model.

Abstract: Concrete truss spar model was tested using regular waves in a wave basin andthe responses in surge, heave and pitch were measured. A program was developed to determine the responses using numerical method. This program was run using the modelparameters. The results are agreed well with thecorresponding results obtained from the test measurements. Then thisprogram was applied to a prototype sparsimulated results were compared with the corresponding numericalresults and test measurements.

Abstract: In this paper, a study on the combustible methane-oxygen mixture was conducted, using the linear stability theory to analyze the deflagration mechanism of methane. The criterion of deflagration detonation transition was proposed. The criterion can be used as a theoretical support for the prevention and control of methane explosion.

Abstract: At high temperatures, heat transfer in foams occurs by conductions through solid matrix and air as well as by thermal radiation propagating the structure. Starting from the analysis of different foam morphological structures, the body-centered cubic cell model is applied to predict the conductive and radiative properties. Both the open foams and the closed foams are analyzed. Temperature-dependency of the material properties is also taken into consideration. The Rosseland approximation is used to predict the radiativie conductivity. Effects of temperature, cell diameter and porosity on the equivalent thermal conductivity are discussed. It is found that both the temperature and the structure parameters have strong influences on the equivalent thermal conductivity.

Abstract: This paper presents a theoretical analysis for the incompressible MHD stagnation-point flows of a Non-Newtonian Fluid over stretching sheets.The governing system of partial differential equations is first transformed into a system of dimensionless ordinary differential equations. By using the homotopy analysis method, a convergent series solution is obtained. The reliability and efficiency of series solutions are illustrated by good agreement with numerical results in the literature.Besides, the effects of the power-law indexthe magnetic field parameter and velocity ratio parameter on the flow are investigated.

Abstract: For contamination of the medium voltage insulators XP-7 strain insulator-string, analysis of localized pollution flashover accident in recent years with a surface of insulator contamination degree of relationship, through the surface of porcelain insulator pollution layer conductivity indicators and calculation analysis on pollution flashover voltage, promote different voltage contaminated insulator under replacing the feasibility of early warning. Results showed that, the relationship between pollution flashover voltage and conductivity parameters is clear, available with microprocessor and more intuitive remote communication unit for remote monitoring and control system of early warning, reduce default phase pollution flashover accident of the power ring network of transmission lines in remote areas , enhance the stability of power load .

Abstract: In undersea applications, contactless power transferring (CPT) systems are surrounded by seawater, and show very different characters versus those used in air. To improve the transferring capacity and stability of CPT systems used in seawater, a new model was established in this paper, and the parasitic capacitance across the coupled coils was considered in this model. By using two-port network method, the model was analyzed to demonstrate the transferring properties of the system. Coupling parameters and parasitic capacitances of a physical prototype were measured, and the data were used to compare the two models inner characters. Conclusions of this research can be used in more in-depth studies.

Abstract: In this paper, an expert PID controller used for digitally controlled DC-DC buck converters is proposed. It is designed bycombing expert theory with traditional PID theory, basing on the controlled objects and the knowledge of control laws. The controller uses the expert experiences to regulate the PID parameters online according to the dynamic characteristics of the system. The simulation and practical results indicated that, comparing with conventional PID controller, the expert PID controller which has faster startup transient response, smaller overshoot and more stable steady-state response, is better than conventional PID controller. It is well fit for the demand of control system.

Abstract: A method to accurately estimate the state of charge (SOC) for LiFePO₄ (LFP) batteries is urgently required, to address the issues associated with the increased use of LPF batteries for portable devices. This paper proposes a hybrid method that combines a radial basis function (RBF) neural network and enhanced particle swarm optimization (EPSO) algorithm for SOC estimating. With a RBF neural network structure, the EPSO algorithm is used to tune the parameters of the RBF neural network, including the centers and widths of the RBF and the connection weights. The trained RBF neural network is then used to estimate the SOC of a LFP battery. In order to demonstrate the effectiveness of the proposed estimation method, the method is tested using 12.6V, 52Ah LFP batteries under varied discharging condition. The effectiveness of the proposed method is compared with the Coulomb integration method and the back propagation (BP) neural network. The results show that the proposed method outperforms the other methods.