Papers by Keyword: SEA

Abstract: Occupant safety is one of the critical performance criteria established in the aerospace industry. Several composite materials have been developed but the energy absorption properties are not yet satisfactory. This study investigates the energy absorption characteristics of aluminum tubes reinforced with coir-fiber/epoxy system at varying proportions (10-90%) according to the specifications of hybrid tube thickness compositions (10T, 15T, 20T) towards evolving a criterion for optimal performance. Finite element analysis was conducted in ABAQUS to determine the load–displacement response and the crashworthiness properties of the tubes while a representative volume element (RVE) model was formulated to obtain the elastic properties of the reinforcement phase. The results indicated that the incidence of high peak forces P_max is related to tube thickness variations where the 20T tubes were found to give the best performance, while the 15T tubes showed a superior performance under progressive crushing and presented the best responses for specific energy absorption (SEA). A multi-objective optimization plan was implemented and through the Pareto fronts, tube configurations (C20T60F), (C15T70F) and (C20T40F) were found to be most consistent with the design criteria. Results from experimental validation were found to be in close agreement with numerical predictions and satisfied the overall objective of achieving a good balance in lightweight design for crashworthiness applications.

Abstract: A study about the structure load identification was made in this paper, based on the SEA power flow method. An inversion formula was firstly developed for the case that the load position is known. Using the formula, an algorithm was proposed to locate the source when the load position is unknown. A reference source must be chosen to utilize the algorithm. To make full use of the surplus data and to further improve the identification accuracy, the least square method was applied. Experiments about both cases were taken to validate the approach obtained above and it was shown that the approach is correct and effective. It is proved that the power flow inversion approach has some practical value in engineering.

Abstract: In this paper the crashworthiness of a thin-walled column is selected as the optimization goal and its section gauge size parameters are defined as variables. We use Optimal latin hypercube design method and ASA optimization method respectively to define sampling design points and find optimal design in Kriging metamodel, constructed using function values in FEM results at sampling design points. A design space updating method is introduced in this paper to reduce computational consumption and improve accuracy by several rounds of metamodeling and optimization, practice shows that object parameter SEA in each round converge to a final one, constrained by the demand of no weight added. High accuracy and rapid convergence of this method will be verified by comparison between results by this method and FEM.

Abstract: It is one of the important technologies to realize the wireless network communication in the special marine environment. The fog that contains salt and water above the surface of the sea has certain influence on the attenuation of electromagnetic field in the wireless communication. The attenuation coefficient of electromagnetic wave in such medium is discussed in this paper, by replacing the permittivity of the salty fog with that of the NaCl solution. And then such attenuation coefficient will be introduced to the electromagnetic fading model with the sight considered. Finally, this paper designs a electromagnetic wave attenuation model of the sea, which could provide some suggestions for establishing wireless communication network on the sea.

Abstract: Elliptic curve cryptosystem is used in the process of embedded systems, the selection and generation algorithm of the elliptic curve will directly affect the efficiency of systems. From Elliptic Curve's selection, Elliptic Curve's structure, Elliptic Curve's generation, this paper discussed the realization of a random elliptic curve method of Embedded Mobile Device, the SEA algorithm and its improved algorithm. The results show that this method can achieve a quick implementation of the elliptic curve method to improve the operating efficiency of embedded systems in the same security guarantees.

Abstract: In this paper explicit finite element codes of LS DYNA are applied to simulate the crushing behavior of cylindrical metallic impact energy absorbers with annular machined grooves and the validation of the simulation results are done by comparing with experimental and theoretical findings from the literature. Some efforts are made to find the optimum groove geometry of the tubes by considering two criteria such as the maximum absorbed energy per unit mass (SEA) and maximum ratio of average load to maximum load during crushing (CFE). Maximum allowable load during crushing and the geometrical limits that should not exceed some specified boundaries are considered as design constrains. Based on design of experiment technique (DOE) the conditions that the results should be taken are determined and consequently, response surface (RS) models are created to build a composite objective function that considers both CFE and SEA. Genetic algorithm is applied to find the optimal point for the composite function that meets the design requirements.

Abstract: In order to study the structure-borne sound radiation, statistical energy analysis (SEA) was adopted and an automobile dash was divided into 31 subsystems; the modal density, damping loss factor (DLF) and coupling loss factor (CLF) were acquired, which were the basic parameters of SEA; then dash transmission loss (TL) at the middle and high frequency (MHF) ranging from 100 Hz to 10k Hz was calculated. The most outstanding advantage of SEA was that calculation could be fast done, which was more convenient than FEM (Finite Element Method) and BEM (Boundary Element Method). Finally, a TL experiment was designed to verify the feasibility and reliability of numerical calculation. The 1/3 octave TL curves of the simulation and experiment show a good consistency and the error is engineering permitted, which means SEA simulation possesses high credibility and can guide the engineering research.

Abstract: This paper presents a guide to identify optimal damper location to reduce vibration on built-up structures. The guide is derived from simulation studies carried out on a set of benchmark models. Optimization is carried out using genetic algorithm. Optimal location is found using found using Generic algorithm and the hybrid method. The hybrid modelling method combines the finite element method (FEM) and Statistical energy analysis (SEA) to provide an efficient response predication for mid-high frequencies. The guide to find optimal damper location is tested on a fuselage model of Boeing 737. The fuselage model is developed using VA One software. Good agreement is seen for the optimal locations using the simple guide and result from VA One.

Abstract: A method to predict the modal density and radiation efficiency of orthogonally stiffened cylindrical shell is presented in this paper. The modal density is derived using energy method from the undamped natural frequencies of stiffened shell by treating the stiffeners as discrete elements. The band averaged radiation efficiency is estimated by categorizing the structural modes into acoustically fast and acoustically slow modes. The predicted parameters are compared with experimental results using laser vibrometer measurements. Phase-roll off has been observed in laser vibrometer measurements for which a correction procedure is applied. This prediction method can be easily extended to shells with stiffeners having different size, orientation etc.