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This paper describes algorithm and finite element procedure to model the warpage and shrinkage of “green” powder compacts due to density and density variations during the sintering stage. The numerical procedure has been tested against control experiments of sintering of an advanced ceramics material and found to have good agreement with actual distortions.

In this paper an iterative finite element procedure is presented for the analysis of twoand three-dimensional piezoelectric continua. The procedure is applied to the steady-state analysis of two-dimensional media subjected to mechanical and electrical loading.

Structural damage is bound to have a certain impact on the dynamic characteristics, and further to affect the carrying capability of the structure. With a half-through concrete-filled steel tubular arch bridge as the research object, the finite element procedure ANSYS is used to establish the 3D finite element dynamic model, and figure out the natural vibration frequency and the vibration mode of the bridge; and a research is made on the influence of the damages of the suspenders and cross-braces at different locations on the natural vibration characteristics. The analysis results show that the damage of suspender located in mid-span is even more significant in the influence on the vertical bending vibration, and the damage of cross-brace near the 1/4 span and 3/4 span is of great influence on the lateral vibration of the structure.

Iatrogenic preterm prelabor rupture of membranes (iPPROM) remains the main complication after invasive interventions into the intrauterine cavity. Here, the proteolytic stability of mussel-mimetic tissue adhesive (mussel glue) and its sealing behavior on punctured fetal membranes are evaluated. The proteolytic degradation of mussel glue and fibrin glue were compared in vitro. Critical pressures of punctured and sealed fetal membranes were determined under close to physiological conditions using a custom-made inflation device. An inverse finite element procedure was applied to estimate mechanical parameters of mussel glue. Mussel glue was insensitive whereas fibrin glue was sensitive towards proteolytic degradation. Mussel glue sealed 3.7mm fetal membrane defect up to 60mbar (45mmHg) when applied under wet conditions, whereas fibrin glue needed dry membrane surfaces for reliable sealing. The mussel glue can be represented by a neo-Hookean material model with elastic coefficient C(1)=9.63kPa. Ex-vivo-tested mussel glue sealed fetal membranes and resisted pressures achieved during uterine contractions. Together with good stability in proteolytic environments, this makes mussel glue a promising sealing material for future applications.

WOS: 000310667100008, Walls are the most important vertical load-carrying elements of masonry structures. Their bond designs are different from one country to another. This paper presents the shear effects of some structural bond designs commonly used for masonry walls. Six different bond designs are considered and modeled using finite element procedures under lateral loading to examine the shear behavior of masonry walls. To obtain accurate results, finite element models are assumed in the inelastic region. Crack development patterns for each wall are illustrated on deformed meshes, and the numerical results are compared.

Numerical procedures for efficient mass conservative solutions of the head-based form of the Richards equation are presented. Mass conservative solutions are shown to result when the capacity coefficient, C, is formulated by equating the storage term and its chain rule expansion in their discretized forms. Equivalence in the storage term expansion is maintained in finite difference models when C is evaluated with a standard chord slope approximation. This scheme is shown to produce excellent global mass balance accuracy in simulations of vertical moisture infiltration. An analogous approach to the expansion of the storage term using finite elements results in element dependent expressions of C. Application of this approach produces mass balance accuracy with errors less than 1%, but also exhibits slow convergence in the consistent form. A nontraditional finite element procedure is presented which maintains equivalence in the storage term expansion when C is evaluated with the standard chord slope approximation. This scheme exhibits excellent mass balance accuracy, in either the consistent or lumped forms, without significant loss in computational efficiency.

Hot plane strain compression tests on 1050, 1198, 3003 and 3004 aluminium alloys have been conducted. Based on these experiments and on a set of internal type constitutive equations for hot working, the values of the parameters in the constitutive functions are determined. The constitutive equations proposed here, with the constitutive functions and material parameters associated, accurately reproduce the basic tests. The procedure used to fit the material parameters is improved, in comparison with classical slip line analysis, by using a finite element modelling of the plane strain compression test. It is demonstrated that accurate plane strain or three-dimensional large strain finite element analysis can be used to correct the friction and lateral spread effects. Furthermore, it is demonstrated from comparison with the experimental observations that microstructural parameters can be accurately determined from numerical modelling. The constitutive equations and finite element procedure proposed here can be useful for obtaining an improved analysis of hot rolling of aluminium alloys.

Numerical simulations of damage progression in laminated composites with a hole are presented. The finite element procedure which incorporates two-phase continuum damage constitutive relations is utilized for the numerical predictions. The pre dictions from the numerical simulations are compared with the experimental results. The similarities and contradictions between predictions and experimental observations are dis cussed. Overall, the predictions are qualitatively close to experimental observations. The qualitative difference between predictions and experimental observations is obvious in laminates where delamination and edge stresses play a significant role in damage evolution up to ultimate failure. The discrepancy in results in these cases is due to limitation of the failure modes incorporated in the model and the damage induced by the out-of-plane stresses.

It is shown that, for a class of time-dependent partial differential equations of the form ut = ℒu, one step of the moving finite-element (MFE) procedure corresponds to one iteration of an algorithm for obtaining best L2 fits with adjustable nodes to continuous functions. In the steady-state limit the MFE procedure gives the best fit of ℒu, with adjustable nodes, to the null function. For first-order partial differential equations, the MFE procedure moves nodes with approximate characteristic nodal speeds. We identify an additional speed component arising directly from the L2 projection which seeks a best fit in the sense described above. © 1994 John Wiley & Sons, Inc.

The authors thank Mrs. G. Starzyk, F. Baratto, N. Charoy and M. Moura for the projects they realised to develop the SPT equipment and to realize the tests presented here. Moreover we thank Drs. S. Allain and J.-Ph. Masse (ArcelorMittal, Maizières-lès-Metz) for the DP steel sheets supplied and discussions on the DP characterization. We also thank J.C. Vervisch for its valuable help in experimental activities.; In this paper an inverse finite element procedure was developed to assess the true- stress strain relationship of a DP dual phase. Experiments were performed both by means of instrumented indentation and small punch tests on small samples cut in the same steel sheet. Tests are developed on a Zwick macro-hardness tester. Single test are first proposed in order to estimate the parameters of the constitutive law (K,n). We propose to conduct SPT tests using PTFE lubricant and hard (WC / Co) ball. An inverse method based on the Nelder and Mead algorithm has been developed in order to found experimental curves. Nevertheless we show that this method lead to poor estimation of the parameter of the constitutive law. We propose to improve these estimations by cross-mechanical tests. Indeed we show that the estimation of the low-error (K,n) domains deduced from each single test can be crossed. This method leads to a better estimation of the constitutive law. Moreover both load/displacement curves of SPT and macrohardness can be found again.; International audience; In this paper an inverse finite element procedure was developed to assess the true- stress strain relationship of a DP dual phase. Experiments were performed both by means of instrumented indentation and small punch tests on small samples cut in the same steel sheet. Tests are developed on a Zwick macro-hardness tester. Single test are first proposed in order to estimate the parameters of the constitutive law (K,n). We propose to conduct SPT tests using PTFE lubricant and hard (WC / Co) ball. An inverse method based on the Nelder and Mead algorithm has been developed in order to found experimental curves. Nevertheless we show that this method lead to poor estimation of the parameter of the constitutive law. We propose to improve these estimations by cross-mechanical tests. Indeed we show that the estimation of the low-error (K,n) domains deduced from each single test can be crossed. This method leads to a better estimation of the constitutive law. Moreover both load/displacement curves of SPT and macrohardness can be found again.

The threat of terrorist attack on subway system using explosives intensifies considerably in recent years. Explosion inside subway tunnels may damage the subway structures and result in further socioeconomic losses. Specifically, the century-old single-track cast-iron subway tunnels in New York City and London are very vulnerable to this type of attack. In this study, a 3D Finite Element procedure was developed to investigate the damage of cast-iron tunnels in saturated soils subject to internal explosions using medium amount of explosive (75 kg TNT) that might be perpetrated by terrorists. The stress path and damage mode of these tunnels subject to internal blast loading were firstly investigated, based on which the damage of cast-iron tunnel lining was simulated using hardening elasto-plastic model considering shear damage. The study then focused on the influences of soil-structure interaction and the compression of saturated soil under large compressive loading. It was found in the study that compressibility of saturated soil influenced significantly the damage of cast-iron lining while the effect of soil-structure interface was much smaller.

The present paper deals with the problem of stresses generated during the setting process of polymer tooth fillings. A finite element procedure capable of accurately predicting the stresses along an interface between two different materials is presented. Adaptation of the finite element mesh is carried out based on a simple error estimator. The procedure is tested against benchmark problems and then applied to polymer tooth fillings. The results of the study are relevant in understanding and improving the behaviour of dental restorations.

A theoretical and experimental investigation of a laminated plate with an embedded, initially circular delamination, loaded in uniaxial compression is described. The main issue concerns the combined postbuckling and crack growth behaviour in general situations at arbitrary crack contours and applied to fibre-reinforced carbon-epoxy composite plates. In a numerical procedure a standard FE-code is used to solve the structural postbuckling problem and extended to account also for contact effects. To predict interlaminar crack growth an automatic finite element procedure was employed for the purpose. Delamination growth in laminates was detected by the aid of acoustic emission. After successive crack increments, the evolution of the delamination front was mapped using an ultrasonic C-scan technique and also for comparison by X-ray. Predicted and observed results are compared as regards postbuckling behaviour and in particular the magnitude and shapes of delamination growth fronts.

An efficient finite element procedure has been developed for the analysis of quenching problems involving nonisothermal phase changes. The finite element analysis includes temperature dependent material properties, a mixed hardening rule to describe the material constitutive model, and the incorporation of time-temperature-transformation (TTT) diagrams. The procedure is applied to the simulation of quenching of steel cylinders and an aluminum connector with temperature-dependent convection boundary conditions. First, the stress analysis of the quenching of an infinite cylinder is carried out and the predicted distributions of temperature and stresses are compared with an available numerical solution to validate the accuracy of the present formulation and procedure. To demonstrate the predictive capability and practical applicability of the developed procedure, the simulation of quenching of finite cylinders of various length-to-diameter ratios and of a square bar are presented. The role of edge effects and specimen geometry on the residual stress distribution is analyzed. In addition, the microstructures developed during the quenching of 1080 carbon steel cylinders are predicted using TTT diagram incorporated in the analysis. The final example addresses the simulation of age hardening in spray quenched 2024 aluminum connector. The example problems are directly related to many practical applications, such as the heat-treatment of solid piston pins used in automotive engines and the spray quenching of aluminum connector. They also illustrate the wide range of material transformations which can be modeled using the present finite element procedure.

The large-amplitude vibration of unidirectionally reinforced graphite/aluminum cylindrical panels exposed to a sudden rise in surface temperature is investigated using the finite element procedure. Numerical results are presented for square and rectangular simply-supported panels having various radii of curvature. Responses predicted using linear and quasi-static formulations are compared with solutions to the nonlinear problem.

In Chapter 7 we discussed the difficulties encountered in the formulation of reliable and effective shell elements. These difficulties are summarized in the synopsis of Figure 8.1 in correspondence with the various types of shell asymptotic behaviors that can be encountered, as addressed in Chapter 5. The objective of the present chapter is to propose some strategies to evaluate shell finite element discretizations in the search for improved schemes. With general analytical proofs not available for the convergence behavior, the numerical assessment is a key ingredient in these strategies. As an example we present the formulation of the MITC shell elements and demonstrate how the numerical assessment of these elements can be performed.

Purpose – To purpose of this paper is to introduce a procedure to compute the d‐ and q‐axis parameters of the induction motor.Design/methodology/approach – A finite element procedure, based on the d‐ and q‐axis model of the induction motor is adopted.Findings – Such a procedure is well suited to analyse IM with anisotropic rotor, where an intentionally created saliency is introduced in the rotor bar geometry, so as to detect the IM rotor position without sensor.Originality/value – The proposed procedure allows one to evaluate the sensorless control capability of the IM. It will be useful for both analysis of the IM performance and design of the machine itself.

In this study, higher order beam elements are developed based on the absolute nodal coordinate formulation. The absolute nodal coordinate formulation is a finite element procedure that was recently proposed for flexible multibody applications. Many different elements based on the absolute nodal coordinate formulation are introduced, but still the beam elements are not able to describe the trapezoidal cross section mode. This leads to the locking phenomena, and therefore, the beam elements based on the absolute nodal coordinate formulation with three dimensional elasticity converge to an inexact solution. In order to avoid the locking phenomena, the trapezoidal cross section deformation mode is included in the beam elements based on the absolute nodal coordinate with additional degrees of freedom. The proper description for the trapezoidal cross section deformation is important for the continuum beam elements based on three‐dimensional elasticity where the material model is often based on general continuum mechanics.

This paper deals with the analysis of induction motor (IM) with an intentionally created saliency, rearranging the rotor bar geometry, so as to allows a sensorless detection of the IM rotor position. A finite element (FE) procedure, based on the d- and q-axis model of the IM, is used to compute the d-and q-axis parameters of the machine. The proposed procedure is useful for both analysis and design of the machine evaluating the sensorless control capability of the IM. The FE procedure focuses on the prediction of the IM parameters variation, the effect of slot harmonics, and the impact of the rotor skewing on the rotor parameter.

An automatic adaptive refinement procedure for finite element analysis is presented. The procedure is applied to two-dimensional elastostatic problems to obtain solutions of prescribed accuracy. Through the combined use of new mesh generator using contour developed by Lo1 and the concept of strain energy concentration, high-quality graded finite element meshes are generated. The whole process is fully automatic and no user intervention is required during the successive cycles of the mesh refinements. The Zienkiewicz and Zhu2 error estimator is found to be effective and has been adopted for the present implementation. In the numerical examples tested, the error estimator gives an accurate error norm estimation and the effectivity index of the estimator converges to a value close to unity.

In a companion paper, it was pointed out that when the ratio of the out‐of‐plane flexural stiffness to the in‐plane flexural stiffness is not small, classical analysis may lead to inaccurate predictions of the out‐of‐plane lateral buckling loads of beams and beam‐columns, since the effects of the in‐plane prebuckling deformations are not considered. This paper investigates numerically the effects of the in‐plane prebuckling deformations on the lateral buckling of beams and beam‐columns by using the finite element procedure developed in the companion paper. The numerical results show that the classical predictions of the lateral buckling loads of beams and beam‐columns are generally conservative, but the predictions obtained by a linearized procedure that ignores second‐order terms are overestimated. The predictions by the nonlinear iteration procedure recommended in the companion paper agree well with the experimental results. The effects of span length and height of the load point have also been investig...

This paper illustrates the application of the finite element method to the form finding of membrane tension structures. A method for automatic mesh generation of triangular elements is developed to...

An adaptive h-version finite element procedure is presented for a 2D elastodynamic transient analysis using direct integration. The procedure modifies the spatial discretization, i.e. the mesh, in time so that the spatial discretization error can be controlled in each time instant. We analyse an a priori error estimate for the total energy which shows that an a posteriori error estimate developed by Zienkiewicz and Zhu for linear elastostatics can reasonably be extended to dynamic transient analysis. For the time integration, both explicit and implicit time integration schemes can be coupled with the procedure. However, the study in this paper is confined to the use of the Newmark scheme. Numerical examples are used to study the performance of the error estimate and to illustrate the adaptive procedure. Obtained numerical results indicate that: (i) the extension of the Zienkiewicz–Zhu estimate to dynamic transient analysis is useful; (ii) the presented adaptive procedure can, in an efficient way, provide a finite element solution with a user-controlled accuracy.

This paper describes a finite element (FE) procedure to compute the performance of a controlled induction machines (IM). The choice of the reference frame for the FE solutions corresponds to the rotor flux oriented reference frame. Thanks to the particular analysis strategy, only magnetostatic FE simulations are used to reduce the computation time. The use of magnetostatic simulations allows the saturation effects in all the machine parts to be taken into account during all computations. Experimental tests are included in the paper to confirm the accuracy of the predictions achieved by the proposed analysis.

Newman's Dugdale strip-yield model for crack closure was used to estimate the crack-closure behavior of cracks emanating from notches. The estimated effective stress-intensity ratio U(a) = ΔK e f f (a)/ΔK(a) obtained usingNewman's model did not exhibit the frequently observed "dip" presumably caused by the notch plasticity. To incorporate the effects of notch plasticity into the Newman model, the plastic stretches caused by the notch were superposed on the plastic stretches caused by the crack tip. A finite element procedure was used to calculate the magnitude of the notch plastic stretches. It was found that the magnitude of the notch plastic stretches was much larger than that of the crack-tip plastic stretches and that the notch plastic stretches were the main source of the plastic wake when the crack tip was within the notch plastic zone. The validity of the proposed modification of Newman's Dugdale strip-yield model was verified by comparing the predicted results with the published experimental data for various notched components. The effects of the notch-plastic zone on U(a) were found to be significant for stress ratio R ≥ 0 but to be unimportant for R ≤ -1.

In this paper, an extension of the static shakedown theorem (Melan’s theorem) for elastic-plastic materials with temperature-dependent elastic modulus is presented. Cases of the decrease of yield function and the variation of coefficient of thermal expansion with temperature are included. The proposed extension leads to the introduction of a shakedown safety coefficient. To illustrate the statements of our theorem, step-by-step finite element procedure is applied to study a three-bar problem and a plate with the central hole subjected to thermo-mechanical cyclic loadings.

The moving finite-element procedure of Miller [SIAM J. Numer. Anal., 18 (1981), pp. 1019–1057] is analysed and broken down into a number of steps. The central step is a mapping from element velocities to nodal velocities which is exact for a class of one-dimensional scalar nonlinear partial differential equation (PDEs). For more general PDEs the mapping is preceded by an element-by-element projection step. In higher dimensions the mapping is followed by node-by-node projection. For first-order PDEs the procedure gives rise to ordinary differential equation systems approximating the method of characteristics. For second-order operators the behaviour of the nodes can only be described qualitatively.The central mapping is a Legendre transformation from the data to the nodal velocities while the full procedure is an approximate Legendre transformation. The same transformation can be used to construct a dual PDE which may be numerically easier to solve.The structure is used to analyse nodal movement and to giv...

Hierarchical single surface (HISS) δ0 and δ1 models are briefly discussed. An algorithm for the implementation of δ0 and δ1 models in a finite element code and the associated subroutines, written in FORTRAN 77, are presented. The algorithm is general and can be adopted for other computer codes with minor changes. Detailed steps and subroutines are included for easy implementation of the models in specific codes. Two example problems are also presented to enable the user to verify the implementation.

Within the framework of a finite elastoplasticity model, a complete formulation for sliding friction is given to provide a precise treatment of the deformation occurring in metal forming processes. The sliding friction is governed by a set of interface equations that satisfy both the kinematic constraint and the equilibrium requirement. These equations are deformation sensitive and are dependent on the local configuration and its rate changes. The equations, together with the field equations of the finite elastoplasity model, are then adopted into a least squares finite element procedure for problem solving. The analysis capability accounts for both dilation and shear banding, and provides insight into the mechanics of an actual deformation process. As an illustration, upset forging of a block of mild steel is analyzed. The analysis results indicate that the frictional response at the die-workpiece interface is a bulk phenomenon. Both normal pressure and frictional traction can change drastically along the die-workpiece interface during deformation. The results also exhibit a unique feature of the analysis capability as they delineate an upper-and-lower yield phenomenon along the load-deflection curve. Inside the bulk, the development of void growth and shear bands agrees with what had been observed experimentally. These results demonstrate the efficacy of the solution method in treating metal forming problems.

Torsion often occurs in real engineering structures such as beams, shafts, and framed structures in conjunction with bending actions. This work mainly focuses on torsion of shafts with noncircular sections. Generally, torsion of beam with noncircular cross-section produces warping or nonuniform out-of-plane displacements in the cross-section. Warping introduces longitudinal strains as the section twists and significantly affects the torsional stiffness. The principal objective of this work is the development of a smart structure technique, which involves piezoelectric materials that necessarily involve coupled mechanical and electrical field, for the control of warping displacement of twisted noncircular shafts. In this work, expressions for warping displacement and shear stress at a section have been derived for the coupled load case. This work focuses on two interrelated cases in relation to the warping of the noncircular bar. Firstly, the warping of cross-section of host structure is analyzed. Secondly, the warping control of a smart shaft with selected noncircular cross-section is analyzed. The paper also describes a Finite Element procedure for the 2D and 3D analysis. In this paper, numerical results have been generated and plotted using MATLAB® for different cases like pure mechanical loading, pure electrical loading, and the coupled field loading with a view to quantify the stiffness characteristics of smart shaft. The finite element calculations are made with ANSYS® for the present analysis work.

This chapter contains sections titled: Introduction Green's Function Analysis Using Finite Element Method Normalized Eigenfunction Finite Element Procedure Complex Gyrator Circuit of Junction Circulator Contour Integral Method

A three-field mixed finite element procedure for the analysis of wave propagation through fluid-saturated porous soils is presented. This approach uses the solid displacement, the fluid displacement relative to the solid and the pore-fluid pressure as the field variables. Thus, a continuous pore pressure field is ensured and pore pressure boundary conditions, e.g., free-draining surfaces can be easily handled. Application of the procedure to a one-dimensional problem shows good agreement with the analytical solution. However, the method is more expensive than the customary two-field formulation using the solid and the relative fluid displacements as the field variables.

In this paper we focus on the analysis of solids and structures when these are subjected to extreme conditions of loading resulting in large deformations and possibly failure. The analysis should be conducted with finite element methods that are as reliable as possible and effective. The requirement of reliability is important in any finite element analysis but is particularly important in simulations involving extreme loadings since physical test data are frequently not available, or only available for some similar conditions. To then reach a high level of confidence in the computed solutions requires that reliable finite element procedures be used. While in this paper a large field of analysis is covered, the presentation is narrow because it only focuses on our research results, mostly published in the last decade (since 1995), and only on some of our contributions. Hence, this paper is not written to fully survey the field.

Micro-electro-mechanical systems (MEMS) devices are widely used in industry. The micro-actuator is an important component of such devices, transforming external influence into mechanical displacement. The development of a design technique to derive the optimal design parameters for a micro-actuator is a problem of current interest. The present paper describes a technique for determining geometric parameters for a simplified micro-actuator structure (a hemispherical shell), such that under a prescribed critical pressure it will undergo a specified discrete deflection. Such a deflection is commonly referred to as "snap-through". A mathematical model and a Finite Element procedure for the mechanical analysis of a flexible thin-walled shell under large deformation are proposed. Initially the snap-through is modelled as a quasi-static effect, but subsequently, the influence of the inertia is also considered. The optimization procedure was performed using the PSE/MACROS optimization program. The results for an example model numerical optimization are shown.

In this paper, a drop vehicle of LCD system was selected to address the assembly-induced stress and its effect on the integrity of assembly system in drop simulation. A finite element procedure was implemented to analyze a two-step loaded LCD system in terms of ABAQUS/Standard and ABAQUS/Explicit tools. Firstly, the LCD is statically loaded by the pretension of the screws and the pressure of the elastomer to determine the stress/strain equilibrium by using the ABAQUS/Standard tool. Secondly, the pre-stressed LCD system is loaded by dropping it from one and half meters high onto a hard floor to assess its reliability under impact loading by means of the ABAQUS/Explicit tool. From the finite element analysis, it is found that the maximum stress level obtained from a model without assembly-induced pre-stressing is generally smaller than that obtained from a model with assembly-induced pre-stressing. In addition, the effect of the ratio of the pressed thickness of the elastomer to the non-pressed thickness of the elastomer on the LCD reliability was investigated based on the proposed procedure. An optimized ratio was recommended.

The application of p- or hp-refinement techniques on an adaptive finite element procedure requires the use of hierarchical basis functions in order to facilitate the tangential continuity of the solution on the interface between two elements with different order. Interpolatory and hierarchical are nowadays well-established families of basis functions. Hierarchical basis functions have been used already in antenna analysis. In this paper, this kind of basis functions is employed in the full-wave analysis of closed waveguiding structures, which requires scalar/vector interpolation and is compared with interpolatory basis functions, mainly in terms of their convergence.

The disturbed state concept (DSC) presented herein represents a unified and powerful approach for constitutive modeling of materials and interfaces in electronic packaging. Together with the computer finite element procedure it provides an analysis tool for calculation of stresses, strains, disturbance and cycles to failure. The accelerated procedure allows economical approximation of cycles to failure and distribution of disturbance at different cycles for design and reliability.Copyright © 2003 by ASME

Engineering design and manufacturing process selection are two of the most important steps in creation process of optimal product. Thin plate-workpieces are very frequently used as equipment members. Because of their very tight tolerances required and controlled surface finish it is very important to know how to predict and describe their manufacturing process. This paper deals with numerical modelling of rolling process. Large elastoplastic strains using updated Lagrangian Hencky formulation are modelled. Numerical procedure is based on the finite element technique. An example is presented.

We give a finite element procedure for the Dirichlet Problem corresponding to surfaces of prescribed mean curvature and prove an optimal convergence estimate in the H 1-norm.

The electromechanical response of a two-phases dielectric material with an active piezoelectric part is considered. The variational formulation of the problem is presented and a finite element procedure which allows to compute the coupled electro-mechanical response is proposed. A simple geometry of a possible active composite material is studied under different loading conditions. The relevant linear response is then shown in terms of the electrical and mechanical variables.

The recent catastrophic failure of an offshore platform brought back into question the shear design of reinforced concrete members. Specifically, there is renewed suspicion that the current design practice may be unconservative for members without shear reinforcement when such members are subjected to shear and axial compression. This paper describes nonlinear finite element analyses made to determine the shear response of the tricell regions of two offshore structures; regions subjected to such loading conditions. The accuracy of the finite element procedure is demonstrated by comparing its predictions with the experimental response of series of specimens tested under varying ratios of shear-to-axial compression. It is concluded that, while current empirical code equations do not perform adequately under the conditions considered, nonlinear analyses can provide reliable results.

A geometrically and physically nonlinear solid-like shell element is presented to analyse the behaviour of laminated structures. The geometrically nonlinear formulation of the element is derived from three-dimensional continuum mechanics and accounts for the change of thickness. The geometry of the element is described by sixteen nodes which are located at the top and the bottom surface of the element. At each node three translational degrees of freedom are defined. Additionally, four internal degrees of freedom are assumed to improve the description of the internal stretching. The physically nonlinear behaviour is assumed to be governed by the Hoffmann yield criterion for orthotropic materials and the von Mises yield criterion for isotropic materials. It is explained how the element can be applied to laminated structures. By calculating benchmark tests obtained from the literature the behaviour of the element is compared with that of standard finite shell and solid elements. From these tests it is concluded that the solid-like shell element is well suited to compute laminated structures. Finally, the element is applied to compute the behaviour of a tensile specimen made of the Fibre Metal Laminate GLARE which gives results which are in good agreement with experimental data. [Author abstract; 16 Refs; In English]

Experimental data from a multiple blade shed incident is used to determine the forces exerted by the blades on a containment ring. A transient, dynamic, finite element procedure is used to model the ring during the blade shed. This work focuses on the selection of the proper numerical parameters that lead to a stable and accurate numerical solution while maintaining physical reality. Examination of the degree of implicitness and various measures of damping, as well as incorporation of large displacement algorithms, has lead to a simulation that successfully determines the forces on the ring. Accurate determination of these forces is necessary for optimal design of containment systems.Copyright © 1993 by ASME