Finite Element Systems

The current version of the ADINA system is briefly described. The philosophy behind the program development is given, and the elements, material models, numerical solution methods and pre- and post-processing capabilities are summarized. Finally, the use of the program in some interesting applications is pointed out and some program developments planned for the future are summarized.

ANSYS is a general purpose finite element computer program for the solution of structural and heat transfer engineering analyses. ANSYS solution capabilities include: static analysis, elastic, plastic, thermal stress, stress stiffened, large deflections, bi-linear elements; dynamic analysis, modal (natural frequencies and mode shapes), harmonic response, linear time history, nonlinear time history; heat transfer analysis, conduction, convection, radiation, coupled to fluid flow, coupled to electic flow; substructures. Analyses can be made in one, two, or three dimensions, including axisymmetric and harmonic element options. ANSYS also contains a complete graphics package and extensive pre and postprocessing capabilities.

APPLE-SAP is a general purpose structural analysis and finite element (f.e.) system developed by ITALIMPIANTI upon two programs originally created at the University of California — Berkeley, namely SAP4 and DOT.

Design of ASAS commenced in late 1969 and the first computer bureau version was released in December 1971. The original software was based largely on a research package for elasto-plastic analysis sponsored by the Atomic Weapons Research Establishment, Aldermaston. Although this was a specialist program in terms of its facilities, the design philosophy was quite general so the extension to more catholic use proved relatively straightforward. Now ASAS is a large-scale and sophisticated system which includes capabilities for linear elastic stress and natural frequency analysis of complex structures. In addition, various facilities for dynamic and heat transfer analysis, a substructure (super-element) capability and numerous specialist pre- and post- processor programs are included.

The ASKA program system was developed at the Institute for Statics and Dynamics in Aerospace Engineering. Stuttgart University, in cooperation with the Imperial College London. Later on, the concept was implemented step by step with the aid of IKOSS and various industrial enterprises.

Over the past decade the finite element method (FEM) has become established as a valuable tool in the solution of a wide variety of problems in engineering. The FEM may be seen as a method of solving boundary value problems where the phenomenon in the domain being studied obeys known differential equations. In the FEM the domain is discretized into a number of elements in each of which the solution of the governing equation is approximated by some function which satisfies the boundary conditions. A set of equations is then set up which when solved forces the solution at various points in the domain, known as nodal points, to the best approximation allowed by the approximating functions and the boundary conditions.

BERSAFE is an established computer system based on the finite element method for the stress analysis of complicated structures. The system has been developed within the UK power industry (the CEGB) over a period of 14 years, and because of its generality of scope and continuous development, is regularly used in many different engineering industries in the UK and abroad. The present scope of the system is described together with its availability on different computers in different centres.

CASTEM is a general purpose finite element software for the solution of mechanical and heat transfer analysis for the linear or non-linear problems. It has been developed since 10 years jointly by the mechanical and thermal research department (DEMT) of the French Atomic Energy Commission (CEA) and the CISI which commercializes this system. The CASTEM system is based on the very extensive experience acquired by the CEA engineers, in the main problems encountered in the nuclear industry. This capabilities are continuously upgraded by the mechanical testing sessions performed at the CEA, mainly for the purpose of development and validation of the computational schemes.

CA.ST.OR, in French, means Calcul de Structures sur Ordina-teur (Structure Analysis by Computer). It is developed at CETIM (Centre Technique des Mécaniques), which is the technical center of the French mechanical engineering industry.

COMET-PR is an advanced finite element software system. While retaining all of the essential features of conventional finite element software systems, it provides the additional user-capability of varying the order of (polynomial) approximation over each element. This provides two important practical advantages: greatly increased reliability and substantial reduction in the cost of analysis.

DIAL is a general purpose 2D and 3D finite element system consisting of a family of independently executable modules called processors; these communicate with each other through a common database (Figure 1). Each processor is driven by a free field command language that allows data statements, arithmetic expressions, looping, and conditional and unconditional branching similar to FORTRAN. User-written FORTRAN subroutines also are allowed for maximum flexibility, in which case the subroutine must be compiled and the processor linked to obtain an executable element. DIAL can perform nonlinear static and transient response structural analysis, extract frequencies and mode shapes for modal analysis, and perform bifurcation buckling analysis. The bifurcation buckling and vibration analyses can be performed from either a linear or nonlinear prestress state. In linear problems, unsymmetric vibration modes, buckling modes, or response under unsymmetric loading can be obtained using the method of Fourier decomposition. The unsymmetric vibration or buckling modes can be computed only from an axisymmetric state of prestress.The total Lagrangian formulation is used to include the effects of geometric nonlinearities and finite strains.The element library consists of a full set of modern multiorder isoparametric solid elements along with the corresponding degenerate curved shell and plate elements. Gap and contact elements, constraint elements, straight and curved beam elements, and lumped nonlinear springs and dashpots are also provided.The material library consists of general anisotropic linear materials along with isotropic elastic-plastic, nonlinear elastic orthotropic, isotropic incompressible, isotropic high temperature creep, and incompressible hyperelastic materials. All materials are temperature dependent.Restart capability is provided at almost any point in the analysis along with extensive post-processing and plotting. Because of the modular database architecture, user control is very versatile and economical. Large problems can be solved in an interactive environment. The system is operational on the UNIVAC 1100 series, CDC Cyber 175, and VAX 11/780 computers.

FASOR (Field Analysis of Shells of Revolution) is a user-oriented code for the analysis of stiffened, laminated axisym-metric shells. Very general shell geometries are allowed in that the reference surface meridian may form a branched, multicircuit figure. Modes of response treated are linear asymmetric and geometrically nonlinear axisymmetric prebuckling, and asymmetric buckling and vibration under static axisymmetric loads. Bifurcation buckling under asymmetric loads is also treated by using a symmetrized prebuckling state based on the linear response of a user-specified meridian. For each mode of response, the user may specify any combination of orthotropic or anisotropic material properties with classical or transverse shear deformation shell theories.FASOR employs a numerical integration method (called the field method) whereby a numerically unstable linear boundary-value problem (all modes of response reduce to a sequence of such problems) is converted into two successive numerically stable initial-value problems. In this context, numerical stability means that round-off errors introduced at each step of the integration process tend to decay out. As a consequence, solution accuracy is controlled essentially by a single number, the truncation error tolerance, which is satisfied by automatically adjusting the size of each integration step. The field method thus eliminates the need for mesh generation required by finite element and finite difference methods, and the associated problem of numerical convergence. It also provides for automatic determination of response storage points so as to obtain a uniformly valid discrete approximation of the continuous response.In this paper the field method is briefly described, basic aspects of the mathematical model are discussed, the organization of input data is presented, and input and plot output are given for specific examples.

FINITE ELEMENT GRAPHICAL SYSTEMS Limited is the agent for FEMGEN and FEMVIEW in the U.K. and Norway.

The finite element programs FLASH2 and STATIK were originally developed at the Swiss Federal Institute of Technology (l)-(5). FLASH2 is a general finite element program for the analysis of frames, in-plane, plate and shell problems. STATIK is a sophisticated frame analysis package.

GIFTS-1100 is a pre- and post-processor for structural analysis programs such as NASTRAN, SAP 4 and ICES-STRUDL. It is used via a graphics display terminal: a Tektronix 4010 or equivalent. Plotter output may be generated on any Calcomp compatible device.GIFTS-1100 program modules operate on, and communicate with one another via the GIFTS-1100 Unified Data Base, which is designed to facilitate the process of finite element analysis.The system is capable of generating a range of 2 and 3 dimensional models including frames, trusses, plates, shells and solid objects. These models may be analysed statically, subjected to vibration analysis or transient response analysis or with further mesh generation, to finite element analysis. A wide variety of finite elements are included in the system. The models generated by GIFTS-1100 may be displayed and edited using the graphics facilities.Displacements, distorted shapes and stress results may be displayed and finite element meshes may be shown in stressed and unstressed form. Loads and boundary conditions may be displayed and edited.A bandwidth optimiser is included for finite element analysis; however, after node renumbering the user may still address the original node numbers throughout the rest of the computations.Interfaces are available to NASTRAN, SAP 4 and ICES-STRUDL II.

RAFTS and LAWPILE have been developed in order to provide the engineer with economic tools for the analysis and design of raft foundations and laterally loaded piles and walls respectively. Both programs take account of the effects of soil-structure interaction and utilise standard structural finite elements connected to an approximate soil boundary element. The latter allows the economic modelling of inhomogeneous, layered, elastic continua with extensions to enable non-linear behaviour to be studied. The philosophy behind the two programs is outlined and examples of their use presented.

MARC is a general purpose finite element program designed for the linear and nonlinear analysis of structures in the static and dynamic regime. Its extensive element library makes it useful in elastic analysis and its broad coverage of the structural mechanics area makes it invaluable as a nonlinear analysis tool. It is written in Fortran IV in general form with variable dimensions passed down to the subroutines. The user defines his own working space depending on element type, the size of the problem and available memory.

Elastic buckling in slender frames can be determined by methods based on different approximations in the basic strain-displacement relationship and in the choice of shape functions for the deflections. The programme package, Defence Research Elastic Analysis of Masts (DREAM) permits ready comparison of the results of the various procedures for any given frame and static loading. The nature of the approximations involved in the various alternatives can be seen concretely in the analytical forms of the element matrices used by the package.

MSC/NASTRAN is a large-scale general purpose digital computer program that solves a wide variety of engineering problems by the finite element method. The program capabilities include static and dynamic structural analysis, material and geometric nonlinearity, heat transfer, aeroelasticity, acoustics, electromagnetism and other types of field problems. It has been successfully used by large and small companies throughout the world engaged in such diverse fields as automotive, aerospace, civil engineering, shipbuilding, off-shore oil, industrial equipment, chemical engineering, optics and government research,NASTRAN® development was initiated in 1966 under the sponsorship of the National Aeronautics and Space Administration based on known requirements of the aerospace industry for structural analysis. MSC/NASTRAN is an improved version of this program developed and maintained by the MacNeal-Schwendler Corporation; it is marketed and serviced from MSC’s offices in Los Angeles, Texas, Wisconsin, New York, Munich and Tokyo. The program is available at most public data centres and is currently operational on more than 200 computers, including the IBM 360/370 series, the Itel AS, the Fujitsu M series, the Siemens 7800, the Amdahl series, the CDC 7600, the CDC CYBER series, the Univac 1100 series, Digital’s VAX 11/700 series and the CRAY-1.The proven positive characteristics of MSC/NASTRAN account for its longevity, generality of application, ease of modification, user convenience and operational efficiency.®NASTRAN is a registered trademark of NASA.The MSC/NASTRAN package consists of the finite element analysis program MSC/NASTRAN as well as the model generation program MSGMESH and the associated graphics package MSGVIEW. Postprocessing is achieved with the plotter programs NASPLOT and TECK, for hard plotters and Tecktronix devices respectively, and with MSGSTRESS which generates a summary of the stress distributions over the model.Also delivered are programs for data deck editing and file manipulation, as well as the input libraries for the demonstration and test problems.

PAFEC is a well established finite element system developed in the U.K. and marketed worldwide. It provides comprehensive solution facilities and a wide range of element types. And, equally important, when used with PAFEC’s interactive graphics pre and post processor, PIGS, it offers a swift and convenient interface between finite element analysis and the practising engineer.

The creation of accurate three-dimensional models for various finite element and finite difference programs classically has been one of the more costly, error-prone and time-consuming elements in the simulation process. A new and rather unique solution to this problem has been packaged into a software system called PDA/PATRAN-G.This presentation will briefly highlight a few of the capabilities of this system, which includes the following features: The PDA/PATRAN-G modelingHuman engineering of man-machine communications Simple geometry and property-modeling directives Multilevel synthesis of shapes and composite materialsTransparent data base management systemAutomated model generationAutomated mesh refinementAutomated equivalencingReusable structural design modelComputer, display device and application program independenceInteractive three-dimensional color graphic displayMultiple split screensTotal view controlColor-coding

The program PECET (Boundary Element Program in Three-Dimensional Elasticity) is presented in this paper.This program, written in FORTRAN V and implemen ted on a UNIVAC 1100,has more than 10,000 sentences and 96 routines and has a lot of capabilities which will be explained in more detail.The object of the program is the analysis of 3-D piecewise heterogeneous elastic domains, using a subregionalization process and 3-D parabolic isopara, metric boundary elements.The program uses special data base management which will be described below, and the modularity followed to write it gives a great flexibility to the package.The Method of Analysis includes an adaptive integration process, an original treatment of boundary conditions, a complete treatment of body forces, the utilization of a Modified Conjugate Gradient Method of solution and an original process of storage which makes it possible to save a lot of memory.

Two special purpose programa will be presented here, one for plate bending analysis and the other for in-plane analysis of plates. Main characteristics for both programs are minimization of the time required for preparation of input data and for interpretation of the calculated results.

SAP7 is a general purpose finite element computer program developed at the Structural Mechanics Computer Laboratory, University of Southern California. The program is based on the original SAP4(1) ‘and NONSAP(2) programs. The complete package is comprised of three individual programs interfaced together for the purpose of generating and controlling the system mesh, executing the required analysis, and evaluating the output in a graphic mode. SAP7 is capable of linear as well as nonlinear static and dynamic analyses. The nonlinearities are due both to geometry and material and their combination. An important attribute of the program lies in its modular structure which allows quick modifications and simple additions, particularly in the nonlinear a-rea where due to continuous research and development revis ions are constantly required. The program is operational on IBM, CDC, VAX, PRIME, and DATA GENERAL computers.

A suite of finite element programs for WANG desktop computers is presented, covering 2-D and 3-D static and dynamic analysis of beam- and plate-type structures. Emphasis is given to a user-friendly input, to practice-ready result interpretation and to powerful theoretical applied techniques. Table 1 describes the main characteristics.

Fatigue growth calculations of through plane cracks, semi-elliptic surface cracks and internal elliptic cracks are described. The analyses are based on the energy release rate method in an efficient combination with the multilevel super-element technique. The fatigue life calculation has been based on Paris1 crack growth formula. Some numerical examples of growth of through crack in a welded cruciform joint, semi-elliptic surface crack in an aluminium plate and internal elliptic cracks in a nickel plate are reported.

This paper does not set out to convince you that our brand is better than the hapless brand “x” program. Rather it describes how our firm, one of the Country’s largest firms of Civil & Structural Consulting Engineers, has responded to its requirement for a capability to solve Finite Element analyses.The Ove Arup Partnership supports a number of Engineering analysis and design programs on an in-house DEC-10 computer.The major part of the paper is devoted to the STAN structural analysis system, an interactive command driven system which helps the user to carry out all aspects of a Finite Element analysis in a flexible and friendly manner. The system is mounted on the DEC-10 computer.The Ove Arup Partnership has offices worldwide, and because of this it is not feasible for all offices to use the central computer. We have, therefore, also developed a large number of programs for the Hewlett Packard 9845 desktop computers which are installed in many of these regional and overseas offices.One such program, AP117, is a plane stress/strain Finite element program and is also briefly described.

The decade of the 70’s has seen a phenomenal spurt in structural analysis software capabilities. The late 60’s had been witness to the emergence of large capacity, multi-purpose computer analysis programs, and through the 70’s these systems have gained dominance over the field of structural analysis. They have grown larger, faster, more efficient, more capable, and have been responsible for introducing engineering oriented computer usage into relatively low technology industries.

The new implementations introduced to the limited-purpose structural code STDYNL are: the application of boundary element method to the analysis of plates under plane stress or plane strain and under bending, the dynamic analysis of the geometrically nonlinear plane frameworks and the modification of the soil structure interaction to include the effect of the axial force on the dynamics of the frameworks (l), (2), (3), (4).

It is apparent that the requirements for a finite element analysis system for practising civil engineers are, for the most part, some way behind the theoretical capabilities of the finite element method. Practising civil engineers rarely meet the type of structural problem which requires a finite element solution, but when this is required it is important that the software available is readily used with clearly defined input requirements and easily understood results. This intermittent use situation is that for which the SUSAN system has been designed. The program, whilst somewhat distant from the frontiers of finite element technology allows straightforward data preparation for even complex structures with a minimum of user training.

TITUS is a general finite element structural analysis system which performs linear/non-linear, static/dynamic analyses of heat-transfer/thermo-mechanical problems.One of the major features of TITUS is that it was designed by engineers, to address engineers in an industrial environment. This has resulted in an easy to use system, with a high-level free-formatted problem oriented language, a large selection of pre-and post processors and sophisticated graphic capabilities. TITUS has many in civil, mechanical and nuclear engineering applications.The TITUS system is available on various types of machines, from large mainframes to mini computers.

It is perfectly possible to attend a seminar like this and to go away afterwards in a daze, confused by the number of alternative Finite Element programs which have been described, and uncertain about the choice between mini or mainframe, and also about the in-house versus bureau service options.

The FEMALE system has been designed to assist the finite element user in the areas of data preparation and results interpretation whatever analysis software is used. Hence FEMALE is an FE modelling system and not an analysis system.