Number Of Finite Element Analyses Research Articles

Constructive solid geometry approach to three-dimensional structuralshape optimization

This paper presents a constructive solid geometry approach to generic three-dimensional shape optimization. The problem definition and shape control are based on constructive solid geometry whereas the assets of boundary representation are exploited to specify the physics of the problem and for meshing the object. This approach is strongly coupled to an automatic mesh generator and uses to its advantage the explicit association of the finite element data with the model geometry for performing shape sensitivity analysis. Hybrid approximation methods are used to minimize the number of finite element analyses. A classical example of a cantilevered plate with a hole and a realistic aircraft turbine disk problem are solved for optimum shape using this new approach.

Arch shape optimization using force approximation methods

The objective of this paper is to provide a method of optimizing areas of the members as well as the shape of both two-hinged and fixed arches. The design process includes satisfaction of combined stress constraints under the assumption that the arch ribs can be approximated by a finite number of straight members. In order to reduce the number of detailed finite element analyses, the Force Approximization Method is used. A finite element analysis of the initial structure is performed and the gradients of the member end forces (axial, bending moment) are calculated with respect to the areas and nodal coordinates. The gradients are used to form an approximate structural analysis based on first order Taylor series expansions of the member end forces. Using move limits, a numerical optimizer minimizes the volume of the arch with information from the approximate structural analysis. Numerical examples are presented to demonstrate the efficiency and reliablity of the proposed method for shape optimization. It is shown that the number of finite element analysis is minimal and the procedure provides a highly efficient method of arch shape optimization.

Adaptive multiple-levelh-refinement in automated finite element analyses

This paper discusses an automatic, adaptive finite element modeling system consisting of mesh generation, finite element analysis, and error estimation. The individual components interact with one another and efficiently reduce the finite element error to within an acceptable value and perform only a minimum number of finite element analyses.

Case history of leakage from a surface impoundment : Daniel, D E; Trautwein, S J In: Seepage and Leakage from Dams and Impoundments (paper to the symposium, Denver, Colorado, 5 May 1985) P220–235. Publ New York: ASCE, 1985

A manufacturing company constructed a 48-acre (19 hectare), unlined surface impoundment at a site in northern Texas to store wastewater. The site is underlain by unsaturated, alluvial soils. An investigation of groundwater conditions beneath the pond, beginning in 1980, showed that a large mound of contaminated groundwater was perched above the aquifer. A number of finite element analyses were performed in which the hydraulic conductivities of the soil strata, as well as other soil properties, were adjusted until the calculated dimensions of the mound of contaminated water matched the known dimensions. The hydraulic conductivities that were needed to achieve good agreement between computed and measured groundwater conditions were, for some of the strata, several orders of magnitude higher than values obtained from laboratory permeability tests. A limited number of field permeability tests at shallow depth yielded hydraulic conductivities which agreed fairly well with the values from the finite element analyses.

A New Beginning

The Fictitious Notch Rounding approach (FNR) is applied here for the first time to V-shaped notches under in-plane shear loading. The fictitious radius is evaluated for different opening angles as a function of the Microstructural Characteristic Length (MCL), the actual radius and the failure hypothesis. A multiaxiality factor is introduced and found to be very sensitive to the opening angle. Under mode II loading, the problem is more complex than under mode I and mode III, mainly because the maximum elastic stress is outside the notch bisector line. The main problem is the choice of the expected crack initiation angle, which defines the direction where the relevant stress has to be integrated. This integration carried out over the MCL gives the effective stress value for the pointed V-notch. To this end, two different criteria are used, the Maximum Tangential Stress (MTS) criterion and the Minimum Strain Energy Density criterion (MSED). A large number of finite element analyses have been carried out to determine the multiaxiality factor. This factor has been evaluated by comparing the theoretical stress concentration factor (SCF) obtained from fictitiously rounded notches to the effective stress concentration factor obtained by integrating the relevant stress over the Microstructural Characteristic Length.

Application of design of experiments and artificial neural networks for stacking sequence optimizations of laminated composite plates

This paper discusses the use of Distance based optimal designs in the design of experiments (DOE) and artificial neural networks (ANN) in optimizing the stacking sequence for simply supported laminated composite plate under uniformly distributed load (UDL) for minimizing the deflections and stresses. A number of finite element analyses have been carried out using Distance-based optimal design, for training and testing of the ANN model. The deflections and stresses were found by analyses which were done by finite element analysis software. The ANN model has been developed using multilayer perceptron (MLP) back propagation algorithm. The adequacy of the developed model is verified by coefficient of determination (R). The sensitivity analysis has been performed to study the behavior of the laminated composite plate. The results obtained from the ANN model are compared with the finite element results. For various fibre orientations, deflections and stresses analyses are performed to get the optimal fibre orientations. A verification tests are also performed to prove the effectiveness of the ANN technique after the optimum levels of fibre orientations are determined. The confirmation experimental results show that deflections and stresses are very good agreed with the finite element (FE) results. Consequently, the Distance-based optimal set of laminates and ANN are shown to be effective for optimization of stacking sequence of laminated composite plates.

Robust Shape Optimal Design With ConsiderationOf Variation

Design Optimization of structures is considered under variation of loading, geometry and material properties. A hybrid, genetic/nonlinear programming algorithm is coupled to a Monte Carlo simulation technique which seeks to locate an optimal design which can function adequately under the specified range of variation. Crossectional, geometric and topological changes are considered in the formulation. A traditional finite element solution is performed for each simulation where a specific value is selected for each design parameter from a statistical distribution which defines the range of variation. A design evaluation is the result of a number of simulations which produces an output distribution for each constraint imposed upon the design. The solution is executed in a parallel computing environment due to the large number of finite element analysis runs required. A specific example involving a truss structure is presented.