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This paper studies the modified sensitivity analysis applied into an elastic-plastic finite element analysis of a 3D blank design in sheet metal forming. Originally the sensitivity method has successfully been applied to several arbitrary shapes. In the present paper the sensitivity coefficients are not considered constant during the analysis. The presented approach computes the new coefficients from the two last iterations. This method can produce an initial blank boundary shape that has any arbitrary flange shape. A cup with uniform flange has been studied in detail and results show a faster solution convergence than the published sensitivity method. Experimental tests were conducted to compare with the numerical simulations. The optimum blank shape obtained from the numerical simulations was used during the experimental trials. The results of experimental tests for both square and optimal blank are presented here. [ABSTRACT FROM AUTHOR]

This paper is focused on solving the problem of the 2D compressible subsonic fluid flow around an obstacle using BEM with higher order boundary elements, with special consideration regarding to the treatment of singulatities. The 2D problem of a compressible fluid flow around an obstacle is equivalent with a singular boundary integral, obtained in terms of primary variables of the problem, the components of the velocity field. This singular boundary integral equation is solved by using quadratic isoparametric boundary elements. The problem is finally reduced to a linear system of equations. Aspects regarding the evaluation of the matrix coefficients are presented and a special attention is given to the treatment of integrals of singular kernels. A method based on the definition of the Cauchy Principal Value of an integral is developed. The method described is implemented into a computer code made in MathCAD and numerical results are obtained for different types of obstacles. We validate the computer through an analytical checking, made by comparing the numerical results with the exact solutions that exist in some particular cases, which are in very good agreement. [ABSTRACT FROM AUTHOR]

For practical engineering purpose, a new flat shell element baptized (ACM_Q4SBE1) is presented in this paper. The formulated element can be used for the analysis of thin shell structures; no matter how the geometrical shape might be. Tests on standard problems have been examined. Since, the analysis of thin shell structures has generally been purely carried out on a theoretical basis; it is of importance to present some experimental results of an elliptical paraboloid under uniformly distributed load pressure. The results obtained from both numerical and experimental work are presented. [ABSTRACT FROM AUTHOR]

Springback is a very important factor to influence the quality of sheet metal forming. Accurate prediction and controlling of springback is essential for the design of tools for sheet metal forming. Several approaches have been proposed for springback compensation by modification of the tooling shape. These approaches are iterative finite element methods. In this paper an analytical approach is presented for one step modification of the tooling shape in channel forming process to compensate the springback error. With the help of this approach, the optimum die shape for producing the target shape can be obtained in a few seconds. The algorithm of springback compensation by inverse FE modelling is also presented. The results of the analytical approach coincide with those of FE approach. The accuracy of the obtained results is verified by the experimental results and high precision is achieved. [ABSTRACT FROM AUTHOR]

Turbomachinery components often operate in dusty environments, such as in desert regions. Operating under such particulate airflow condition usually leads to erosion damage of blades resulting in degradations of their aerodynamic performance. The present paper presents a numerical study of sand particle trajectories and erosion through an axial cooling turbomachinery. The Lagrangian approach for particle tracking as implemented in the present trajectory code is considering the effects of turbulence and complex flow features near walls on solid particles, random particle rebound and random size distribution. The governing equations of particle motion entrained by the airflow are solved in a stepwise manner separately from the flow field, whereas, particle tracking and impacts are predicted in different cells of the computational domain based on the finite element method. A semi empirical erosion correlation is used to predict erosion areas based on impacts information. The results of the numerical simulations obtained for different positions of rotor blade have revealed that the main impacted areas are found over the blade leading edge corner and an area of the pressure side extending towards and over the tip, in addition to a strip along the leading edge of the suction side. [ABSTRACT FROM AUTHOR]

In this paper, elasto-plastic analysis of an edge crack has been performed using element free Galerkin method. A model problem has been solved in plane stress condition under mode-I loading. A system of nonlinear equations has been obtained by using incremental theory of plasticity, and the equations are solved by assuming piecewise linear approximation. A code has been written in Matlab for elastoplastic analysis of cracked components. The size of plastic zone is calculated around the tip of the crack by EFGM code. [ABSTRACT FROM AUTHOR]

This paper is concerned with adaptive numerical methods for initial value problems governed by systems of ordinary differential equations. Here we introduce a novel step selection algorithm based on the simple idea that locally all continuous functions can be suitably approximated by a straight line. Finally we present two sample numerical computations performed by our step selection algorithm. [ABSTRACT FROM AUTHOR]

The research for the complex properties of visco-elastic material in various impact conditions have been interesting and difficult problems, especially in the auto-crash safety engineering process. In this paper an application of boundary-layer computing for the non-Newtonian rate type impact hardening and share thinning phenomenon are discussed. The numerical scheme yields the convergent finite element analysis (FEA) solution and stable semi-discrete Galerkin-Runge-Kutta(G-RK) iteration. To develope the passive protection model based on the non-recover solid metal (phase1) impact, we are deepening our knowledge of soft material recover protection (phase2) concept. The high performance computing (HPC) tool enabled us to carry out the research on the passive safety analysis with engineering computing. [ABSTRACT FROM AUTHOR]

In this paper, we present an integral form of convection-diffusion equation. Then a class of alternating group explicit finite difference method (AGE) is constructed based on several asymmetric schemes. The AGE method is unconditionally stable and has the property of parallelism. Results of numerical examples show the AGE method is of high accuracy. [ABSTRACT FROM AUTHOR]

In this paper, we present a generic differentiation rule that is applicable to all mathematical operators and illustrate how the generic differentiation rule is vital in deducing the derivatives of complex mathematical operations such as functional iteration. We also show how the generic rule offers more insight into the concept of differentiation and provides systematic proofs to differentiation rules that, otherwise, would have been proven using ad hoc approaches. Next, the generic rule is shown to yield interesting results including a proof that the first-degree approximation of the composite of iterated functions, at the limit where the iteration variable approaches zero, is the sum of the iterators of those functions. Consequently, at the vicinity of the specified limit, composition of iterated functions is remarkably symmetric. [ABSTRACT FROM AUTHOR]

The rapid increase in the use of mobile devices demand the need to meet different multimedia application requirements of the users. However, the application demand and allocation could lead to congestion if the network has to maintain such high resources for the quality of service (QoS) requirements of the applications. In this paper, a new admission control policy for wireless mobile multimedia networks is being proposed. Two kinds of traffics are assumed to compete for the access to the limited number of frequency channels available in each cell: Real-time and non-real-time calls. The calls are further categorized as new real-time and non-real-time calls or real-time and non-real-time handoff calls. Hot spot calls are given priority over cold spot calls if the cold spot request is non-real-time. Call of the same cell and priority are served using ticket scheduling. Blocked new real-time and non-real-time calls are lost, while blocked real-time and non-real-time handoff calls can wait in the handoff buffer for channel to be available. The system is modelled by a multi-dimensional Markov chain, and a numerical analysis would be presented to calculate the blocking probabilities of the calls. The scheme would also be simulated using extensive runs to investigate its performance. [ABSTRACT FROM AUTHOR]

Shape optimization is numerically a very demanding process, where several traditionally separate numerical processes meet together in a heterogeneous multidisciplinary environment. Typical elements involved are (1) the optimizer itself that implements the selected search strategy, (2) the parameterization procedure that provides the bidirectional mapping interface between the 3D geometric shape of the object and a limited number of parameters that control the parametric model of the geometry, (3) the simulation program that provides the results of the simulated interaction between the object and its environment (such as finite element analysis, FEA), and (4) control procedures that monitor the overall workflow and invoke mutual application calls (process flows and data flows) and handle data mining as well as acceptance or rejection of individual instances of candidate designs which are numerically generated and analyzed. In this paper, the set-up of this complex process, combined with evolutionary optimization, is developed with the objectives of numerical flexibility, computational efficiency in terms of combining sequential and parallel execution of individual applications, and low-cost implementation within an unmanaged computer cluster based on the Windows Communication Foundation, WCF. [ABSTRACT FROM AUTHOR]

This paper reports the results of an experimental and finite element analysis of tibial screw fixation in hamstring ACL reconstruction. The mechanical properties of the bone and tendon graft are obtained from experiments using porcine/calf bones and tendon. The results of the numerical study are compared with those from mechanical testing. Analysis shows that the model may be used to establish the optimum placement of the tunnel in anterior cruciate ligament reconstruction by predicting mechanical parameters such as stress, strain and displacement at regions in the tunnel wall. [ABSTRACT FROM AUTHOR]

This paper studies the cardiovascular response under heart failure condition supported by two types of ventricular assist devices (VADs): the positive displacement pump and the impeller pump. The cardiovascular system is modeled using the concentrated parameter method developed previously, by considering flow resistance, vessel elasticity and inertial effects of blood in individual conduit segments. The dynamic modeling of displacement and impeller pumps is represented by VAD inlet/outlet flow-rate changes. Results show that in each simulation, the diseased ventricle is effectively unloaded, and the physiological variables of arterial pressure and systemic flow are adequately maintained. The numerical model is under further development for more sophisticated studies of the interaction of the native cardiovascular system with VAD support and other cardiac prosthetic devices. [ABSTRACT FROM AUTHOR]

This paper presents, a two-stage heuristic based procedure for generating part family and machine cell formation in Cellular Manufacturing System. It decreases exceptional elements and voids which in turns decreases intercell flow of parts and increases utilization of machines in the cells. In the first phase; the problem is solved as a bottom-up aggregation procedure for machine grouping. Aggregation is based on the minimization of intercell flow. Later the parts are assigned to the cells according to the proposed heuristic. Upper bound on the cell size is imposed in the first stage which is relaxed gradually in second phase. It ensures the natural cell formation. The solution obtained at the end of first stage is refined in the second phase. Numerical examples were tested for grouping efficiency, grouping efficacy, global efficiency and have been compared with results reported by other researchers. The computational results are encouraging. [ABSTRACT FROM AUTHOR]

This paper presents a new method for the signature analysis of mechanical watch movements. Contrary to the existing method, it analyzes the time-frequency features of mechanical watch movement through a combination of reassigned scalogram and Finite Element Analysis (FEA). By mapping the signal into a 2D domain of time and frequency, the reassigned scalogram reveals the frequency components of the shocks at different time. On the other hand, FEA gives the modal frequencies of the movements. By comparing the frequency components at different shocks to the modal frequencies of the movement, possible malfunctions of the movement can then be detected. A number of demonstration examples are included. [ABSTRACT FROM AUTHOR]

One of major reasons of failure of solder joints is known as the thermal fatigue. Also, The failure of the solder joints under the thermal fatigue loading is influenced by varying boundary conditions such as the material of solder joint, the materials of substrates(related the difference in CTE), the height of solder, the Distance of the solder joint from the Neutral Point (DNP), the temperature variation and the dwell time. In this paper, first, the experimental results obtained from thermal fatigue test are compared to the outcomes from theoretical thermal fatigue life equations. Second, the effects of varying boundary conditions on the failure probability of the solder joint are studied by using the probabilistic methods such as the First Order Reliability Method (FORM) and Monte Carlo Simulation (MCS). [ABSTRACT FROM AUTHOR]

This paper illustrates the use of the differentiation matrix technique for solving differential equations in finance. The technique provides a compact and unified formulation for a variety of discretisation and time-stepping algorithms for solving problems in one and two dimensions. Using differentiation matrix models, we compare time-stepping algorithms for opting pricing computations and present numerical results that show the advantage of the L-stable Alexander method over the Crank-Nicolson method. We also compare the efficiency of the spectral collocation and finite difference methods, and give numerical results that show spectral methods to be competitive for problems with smooth terminal conditions. [ABSTRACT FROM AUTHOR]

In this paper, we bring three theorems that enable us to approximate the solution of Ferdholm integral equations of the second kind. Then we use the Coifman wavelets or Coiflets as scaling functions for projection that satisfied the conditions of theorems for approximation. Also we use this projection to convert the integral equation to a Galerkin system, which is the most important of the expansion methods for solving linear integral equations. Finally, by using numerical examples we show that our estimation have a good degree of accuracy [ABSTRACT FROM AUTHOR]

This paper presents the work carried out by CALPE team on the development of a mathematical model used in the study and simulation of the pantograph-catenarydynamic interaction in high speed railways considering two independent spans of catenary where the transition spans are overlapped. According to the developedmathematical model, a non lineal system of differential equations with variableconstraint depending on the pantograph position has been obtained. In order to verify the correctness of the model, a numerical integration algorithm based on an explicit method of the central differentials has been implemented. The procedure that has been designed allows us to study the more appropiate contact wire configuration, in order to make smoth transition of the pantograph between sets of spans. This procedure can be generalized considering the case of several pantographs, obtaining very realistic simulations. [ABSTRACT FROM AUTHOR]