Analysis of Structures

and Thermomechanics

for Surveys and Research

V e r s i o n 7

Code_Aster Possibilities

Code_Aster offers a full range ofmultiphysical analysis andmodelling methods that go wellbeyond the standard functions of athermomechanical calculation code :from seismic analysis to porousenvironments via acoustics, fatigue,stochastic dynamics, etc. Itsmodelling, algorithms and solversare constantly undergoing work toimprove them and add to them(1,200,000 lines of code, 200operators). Resolutely open, it ischained, coupled and encapsulatedin numerous ways.

Phenomena

> Mechanical• Static, quasi-static, linear or otherwise• Dynamic, linear or otherwise, on a

physical or modal basis• Fracture, damage and fatigue• Soil-Structure, Fluid-Structure and Soil-

Fluid-Structure interactions> Thermal

• Stationary, transient, linear orotherwise

• Fixed or moving reference coordinatesystem

> Associated phenomena• Acoustics• Metallurgy• Hydration and drying

Analysis Types

> Standard> Decomposition into Fourier modes> Substructuring> Model superposing, multiscale> Adaptive mesh> Sensitivity calculation> Fitting and optimization> Mechanical reliability calculation

Multiphysical

> Internal chainings with thermics• Hydration, drying• Metallurgy

> Internal chainings with mechanics• Thermal• Metallurgy• Hydration and drying

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> Internal couplings• Thermo-hydro mechanical• Fluid-Structure

> External coupling with other codes• Soil-(Fluid)-Structure (MISS3D)

> External chaining with other codes• Hydraulics : Code_Saturne• Thermal : SYRTHES• Electromagnetism : Flux2D/3D• Fast dynamics : EUROPLEXUS

Loadings

> Mechanical• Nodal or distributed forces• Pressure• Dead load• Centrifugal acceleration• Imposed movements• Anelastic strain• Effect of wind

> Thermal• Temperature• Flows, linear or otherwise• Forced convection• Exchange between walls• Heating by Joule effect

> Specific loads (following forces,electromagnetic forces, initial states)

Nonlinearities in staticand dynamic

> Geometrics• Geometric updating, large strains,

large rotations• Follower forces• Drive in displacement, by arc

length, in strain, by criterionoutput

• Load discharge and non-radialityindicators

• Contact and friction: by activestresses, Lagrange multipliers,by penalization or by thecontinuous method(increased Lagrange)

• First order buckling > Materials (95 constitutive laws)

• Linear and nonlinear elasticity• Nonlinear hyperelasticity• Local elastoplasticity and

elastoplasticity with gradientformulation

• Nonlinear viscoelasticity• Local and with gradient formulation

damage• Elastoviscoplasticity• Metallurgical effects• Material data dependent on

temperature, metallurgical

condition, hydration, drying andfluence

• Progressive strain• Hydration, shrinkage and creep of

concrete• Geomaterials

Dynamics

> Modal analysis• With or without damping (viscous,

hysteretic, modal)• Direct or by substructuring• Normalization, filtering, modal

parameters> Linear transient response

• Direct• On modal basis• By substructuring

> Transient response with localnonlinearities (on modal basis)• Shocks • Friction• Fluid blade

> Harmonic response• Direct• On modal basis• By substructuring

> Random response• Parametric and nonparametric

probabilistic • Stochastics

> Direct nonlinear analysis• Implicit• Explicit• Shocks• Plasticity, damage• Contact and friction

> Substructuring• Conventional or cyclic• Modal, transient or harmonic

analysis> Seismic analysis

• With shocks or multi-support• Spectral or transient direct linear

or on modal basis• Modal damping calculation

(RCC-G)> Extrapolation of experimental

measurements• Temporal or frequential

Interactions

> Fluid-Structure• Structure-incompressible flow

interaction; turbulent stresses• Vibro-acoustics (free surface)

> Soil-Structure and Soil-Fluid-Structure• Absorbent boundary elements• Frequential coupling with MISS3D

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Thermal analysis

> Linear and nonlinear thermics• Phase change• Hydration and drying• Mobile coordinate system

resolution> Metallurgical changes

• Steels, Zircaloy• Phase hardness calculation

> Thermal treatments and welding

Geotechnical CivilEngineering

> Constitutive laws for concrete(reinforced or pre-stressed),geomaterials

> Hydration, drying and specific creepat different time scales

> Passive reinforcement or pre-stressing effect with elastoplasticbehaviour : bar, gridsand membrane

> Creep-cracking coupling> Thermohydromechanics (porous

media, formulation in effectivestresses, constitutive laws in kitform, etc.)

> Specific loads (hydric and gaseousflows)

> Excavation procedure

Fracture, damage,fatigue and destructionof structures

> Global release rate • thermoelasticity : G• thermoelastoplasticity : GP and

GTP> Local release rate in 3D> Stress intensity factors> Models of brittle and ductile fracture,

initiation and instability> Specific load drive > Local and non-local damage> Crack modelling :

joint element and X-FEM> Decoupled damage > Fatigue analysis

• Loading history• Counting methods • Specific criteria applications

> Verification of RCC-M criteria > Zarka-Casier method in cyclic loading> Progressive wear> Limit analysis> Micro-macro approach :

polycrystalline model

Survey quality

> Spatial error indicators• Mechanics (in pure residue, by

grading)• Thermics (in pure residue)

> Mesh refinement/unrefinement viaHOMARD

> More robust finite elements• Mechanics (subintegrated,

incompressible)• Thermics (lumped modelling)

> Mesh diagnosis> Thermomechanical time step

redistribution > Sensitivity calculations

• Mechanical • Thermal • In relation to materials, loadings

and domain variations> Parameter fitting

• Materials or loading• In relation to test

sampling or digitalresults

> Reliability calculations : probability ofexceeding threshold using a FORMtype method

Modelling

> Catalogue of material data> Connecting incompatible meshes.

Superimposing models using theArlequin method

> Modelling connection (shell-3D,beam-pipe, etc.)

> Plane stress condition adaptable toall models

> Beam characteristics calculation> Homogenization (composites,

repetitiveness, etc.)> Addition or removal of matter

Elements library (360finite elements)

> Mechanical• 2D, 2D axi (with or without

Fourier decomposition), 3D,sub-integrated, incompressible

• Bars, beams (simple or multi-fibre), pipes, plates, shells,membranes, cables, discrete ornon-distortable elements

> Thermics : 2D, 2D axi (with orwithout Fourier decomposition), 3D,shells

> Hydration-Drying : 2D, 2D axi, 3D> THM Coupling : 2D, 2D axi, 3D

Solvers

> linear (Gauss, LDLT, multifrontalparallelized, GCPC, FETI,substructuring)

> Nonlinear (Newton, etc.)> Integration schemes (Runge-Kutta,

Newmark, adaptatives, etc.)> Modals (Power, Lanczos, IRAM, etc.)> Extended parameter setting. Several

strategies for re-numbering, storage,pre-conditioning, post-verification, etc.

Dedicated tools

> Pipework stacks and elbowsASPIC/ASCOUF

> Steam Generator Tubes : GEVIBUS

Software environment

> Pre- / post processing : I-DEASTM, GIBI,Gmsh, ENSIGHT, AGRAF, GID, Xmgrace

> Data exchange in MED format> Survey management tool and

engineering application workshop :ASTK

> Command File Editor and SyntaxAnalyser : EFICAS

> Portable nature of bases> Developed command language :

PYTHON• Loop, test, checking structures,

etc.• Method, class, etc.• Interactive calculation and

visualization (mathematic libraries,GUI, scale drawings, etc.)

Not forgetting…

> Software under QA (independentvalidations, reference of 1,700 testcases, documentary coverage 13,000pages, source management,qualification of version, etc.)

> code-aster.org website (downloading,online documentation, forum, FAQ,examples, etc.)

> Communication and network(quarterly ASTER ‘echos’ magazine;User Club, its network ofcorrespondents and the annual day;Free Code_Aster under GPL licence,etc.)

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Nonlinear

In an industrial survey it is oftenimpossible to avoid actually takingnonlinearities into account :geometrics, materials, unilateral,shock, etc. Through the operatorsDYNA_TRAN_EXPLI andDYNA/THER/STAT_NON_LINE,Code_Aster proposes solutionssuitable for each of these.

Non-linear operators…

... rich in functionalities and ever easier to drive :DYNA and STAT_NON_LINE make it possible tocarry out an implicit static or dynamic survey withgeometric (contact, major transformations) andbehavioural nonlinearities; DYNA_TRAN_EXPLItakes them into account in explicit dynamics. Thecalculation options are common to these threeoperators, making it possible to benefit, bothstatically and dynamically, from all the contact-friction methods, selective archiving withobservation, behaviours, etc.In thermics, THER_NON_LINE also simulatesnonlinearities (materials, flows) and makes itpossible to calculate the change in the hydrationand drying of concrete over time.

Quicker and morerobust calculations…

“What degree of accuracy should I choose to gaugethe convergence of my nonlinear calculation?” Theengineer considers this question before starting thecalculation. Until now, implicit nonlinear operatorshave used global convergence criteria. Version 7incorporates a new criterion, which uses physicalreference values (stresses, strains, etc.). Thesestrengths give greater ease-of-use and a better-adapted degree of accuracy, particularly in thepresence of heterogeneous residues (a mix ofmodelling, physics, etc.).In order to make the calculation with softeningbehaviours, the secant matrix may be used insteadof the tangent. The latter may be non-symmetrical in

the case of certain structural or behaviouralnonlinearities.The resolution speed of large non-symmetricallinear systems using the multi-frontal method hasbeen optimized in V7. Although it is also possible toisolate subdomains with linear behaviour within thestructure, it is now possible to treat them ascondensed macro elements (static substructuring,MACR_ELEM_STAT).

Tools for improving surveyquality

When the instability risks appearing at structurelevel (buckling) a criterion may be calculatedcontinuously in order to prevent proximity withcritical points. At local level, the Drucker-Pragerbehaviour benefits from the Rice localizationcriterion in V7. Localization phenomena withpathological dependence on mesh, which arecharacteristic of local damage models, may beresolved by using non-local models (see box).During a thermomechanical survey, the choice ofmechanical and thermal temporal discretizationsmay prove difficult. A criterion in STAT_NON_LINEmakes it possible to adapt them to take account ofsignificant thermal gradients.More generally, how can the correct data besupplied to a calculation (materials, loads, etc.)? Inorder to do this, a retiming procedure(MACR_RECAL) identifies the optimal parametersby comparing the results of an experiment withthose of its simulation. The final pertinence of theseresults may be confronted with various sensitivitycalculations (SENSIBILITE) and error estimations(CALC_ELEM).

95 constitutive laws…

... are available in Code_Aster : isotropic andanisotropic elasticity, elastoviscous plasticity(isotropic hardening, kinematics and viscoplasticity,Chaboche and Lemaître models), laws describingprogressive strain (Taheri model, polycristalline),brittle or ductile damage laws (Rousselier model)and all laws originating from targeted issues(plasticity of and damage to the concrete, steels,assemblies, cohesive elements, etc.). They areavailable in a large number of support models andarrays. In addition, “kit” models make it possible toincrease the possibilities : mono and polycristallinebehaviours, creeping and plasticity of concrete,metallurgy, thermo-hydro mechanics, etc.

➜ Metallurgy

Evaluating the residual stressesof a mechanical componentfollowing a welding operation orsevere thermal transients isessential for explaining certaindeterioration phenomena(corrosion under stress, fatigue,etc.). In such situations, thematerials are stressed in a widedomain of temperatures andspeeds and undergometallurgical changes thatmodify their thermomechanicalbehaviour. The available models(a large choice is offered via themetallurgical/mechanical laws“kit” technique) are elastic /(viscous) / plastic and make itpossible to describe variousphenomena : large strains,hardening, viscous recovery,creep, etc. The materialcharacteristics are suppliedphase by phase and thecombination laws can bedefined by the user.

➜ Simulating porousenvironments…

... is a prerequisite for calculatingstructures (dams, storage sites,chambers, etc.). It takes accountof an interstitial fluid circulationin a solid framework usingdisplacements, temperature andone or two pressures asunknowns for calculating those ofwater and gas. Code-Aster’sthermohydromechanicalmodellings (KIT_THM...) processall the interdependenciesbetween these unknowns bystrong coupling and leave fullfreedom to mix varied laws ofbehaviours. In version 7, themodels available for mechanicshave been enriched with theDrücker-Prager, Badel andMazars models, as well as thoseof the University of Barcelona.

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Rupture of a Charpy resilience test piece.

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Behaviour/elementtransversality…

Having all the nonlinear behaviours available for allmodellings is a choice of architecture that it isimportant to maintain. In order to do this, thespecifities of certain modellings tend to be eliminated.Thus, in even stresses, there is no longer any need forspecial developments : an algorithm attributed to DeBorst enriches all the models in this condition, in bothisoparametric and structure elements. Similarly,modellings with 1D behaviours (bars, multifibrebeams, reinforcement grids for reinforced concrete)can benefit from the richness of behaviours developedin 3D (ALGO_1D=DEBORST) via this method.

... and special finiteelements

Certain modellings have been developed in order tomeet specific criteria. This is the case for elementstaking account of the incompressible nature of plasticstrains or, for limit load calculations, stabilized sub-integrated elements (SHB8 in shells, QUAD4, QUAD8,HEXA27). The modelling of possible cohesive linkruptures is also based on joint elements(XX_FISSURE) added to a Barenblatt type interfacelaw.

Contact-friction…

... is tackled in different ways in Code_Aster : method ofactive stresses, penalized or Lagrangian method, not tomention the new continuous method. Its scope of usecovers the full range of modellings (2D/3D, beam andshell), possibly based on incompatible meshes and withupdated geometries.

Nonlinear thermomechanicalcalculation of a combustion turbinecompressor : bladed rotor and quarter-compressor.

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All these methods can be used in dynamic. Processing isfacilitated by the creation of fields storing the values ofplays and reactions in each potential place of contact,which may be visualized in the form of isovalues orcurves. Finally, use of the contact has been simplifiedthanks to a unique point of entry : AFFE_CHAR_MECA,keyword CONTACT.

Large strains androtations…

... can be modelled in various ways (keyword DEFOR-MATION) : SIMO_MIEHE deals with large plasticstrains and rotations and is available in V7 for severalconstitutive laws : viscoplasticity, possibly takingmetallurgy into account, ductile damage. In nonlinearelasticity, GREEN deals with large transformations.Under the hypothesis of large displacements andsmall strains, it also permits the use of all incrementalbehaviours.PETIT_REAC merely updates the geometry at eachtime step (necessarily small) and only tolerates smallrotations. For surface or streamlined structures, largedisplacements and rotations of beams and shells areprocessed by GREEN_GR.

Load drive

Obtaining quasi-static responses on structuresshowing geometric instabilities (buckling, etc.) ormaterial instabilities (softening type law, damage ) isa difficult problem. It may not be possible to obtainthe continuous response with a monotonous load(snapback/through phenomena), which is a problemregarding the convergence of the process. Thankfully,solution monitoring methods (keyword PILOTAGE)often make it possible to remedy this.General methods are available for monitoring changesto unstable structures or limit load calculation : drivein displacement or by arc length. For materials with asoftening behaviour, drive by elastic prediction makesit possible to limit local loss of stability efficiently bycontrolling the most heavily loaded points. Anothertechnique consists of ensuring the continuity of theresponse in strain.

➜ Material data

A lot of material data isavailable to the user via theoperator INCLUDE_MATERIAU,which is usually used in thenuclear industry : by type(median or extremal, etc.), byAFNOR designation and byvariant (laminated, cast, etc.).This automated accessreinforces the reliability,coherence and sustainability ofsurveys. The associateddatabase capitalizes on thevalidation efforts of EDF R&Dmaterial specialists and thenormative data of RCC-M andRSEM. It is, of course, possibleto re-use this functionality out ofthis context in order to createanother database, which issustainable and can be shared.

➜ Non-localModellings

Softening behavioursnaturally lead to resultsdependent on the mesh. Inorder to avoid this,Code_Aster offers two waysof “delocalizing" the damageand thus eliminating a non-physical dependence of thistype. The first, which is moreaccurate, uses the gradient ofinternal variables and is thusintimately linked to thebehaviour model. It isoperational for the VonMises plasticity models,Lorentz’s brittle damagemodel and Rousselier’sductile damage model. Thesecond limits strainconcentrations via aregularized strain field. It isquicker and applies to alldamage models.

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1300 MW turbo-alternatorhydrodynamic bearing unit.Mechanical stresses,contactnonlinearities

Damage : load drive.(Force/displacement)

Dynamic nonlinearimplicit : plasticity +large strains + contact+ friction.

Code_Aster, a Facilitator of Surveys

Finite elements engineers aredemanding people. They askquestions like : « What degree ofreliability should I attach to my rawdigital results? » or « How can Ire-use my meshes in configurationsfor which in principle they were notdesigned ? » Advancedfunctionalities of Code_Asterprovide answers to these legitimatequestions!

User Effects

With fixed physical data, three user effects are takeninto account : mesh, the types of finite elements andtemporal discretization. The development of mesh isa phase that is difficult and costly in terms ofengineers’ time and it is illusory to claim to buildoptimum mesh in principle since the criteria of anindustrial survey may be variable, or even conflicting.It is better to adapt a coarse mesh to therequirements of a calculation while post-processingits results. The CALC_ELEM operator thus suppliesan error cartography, localized to each element, onwhich the HOMARD refinement/unrefinement tool(see box) relies. This does not, of course, dispensewith the need to carry out an initial mesh diagnosis,via MACR_INFO_MAIL for example, and to followthe code’s recommendations in terms of finiteelements. A STAT_NON_LINE option adapts thetime steps in order to conduct thermomechanicalchaining smoothly.

Sensitivity to data

With fixed discretization and resolution parameters,this time we would like to quantify the sensitivity ofa result in relation to its input data. This is either forcomparing the respective influence of the variousparameters, or for inserting this derivative intoanother calculation (optimization, retiming,reliability, see box, etc.). Thus Code_Aster deliversthe analytical derivative of the usualthermomechanical quantities (displacement, stress,temperature, flow, specific modes, energy releaserates, etc.) in comparison with parameters such asmaterials or loads, in both static and dynamic.Once the “sensitive” parameter has been identified(via DEFI_PARA_SENSI), its drive simply requiresthe addition of the keyword SENSIBILITE to themain command. The result is a field in its own right,which can be used like any other. The experimentshows that these derivatives are more reliable andlest costly than those obtained by using finitedifferences.From the sensitivities survey to retiming, there isonly one step that is crossed by the macro-command MACR_RECAL , which automaticallyretimes the material or load parameters from testscarried out on either test pieces or structure. As wellas the optimum parameter values, the user gets anestimation of their relative importance and thepossibility of coupling them, thus making it possibleto discriminate against parameters with littleinfluence.

New Boundaries forfinite elements

Although it is very widely used within the industry, thefinite elements method does not make it possible toefficiently solve certain problems with complexgeometry or developing over time (crack or excavationmonitoring, linking-up of modellings, etc.). Thesetherefore require localized remeshings, which arearduous or even impossible to manage with existingmeans. Different approaches are proposed for solvingthis : the Arlequin and X-FEM methods.The first (keyword ARLEQUIN) offers a multiscalestrategy for connecting numerical models of differentnatures. Using a superposing technique, it easilycarries out local zooms, links and substitutions(adding a default mesh to a healthy mesh or linkingincompatible modellings and meshes, etc.). The second (keyword XFEM) makes it possible to freethe mesh from the constraint of complying withphysical entities by modelling free surfaces or fielddiscontinuities. A finite element may thus be crossedby a crack, making the remeshing less systematic.

➜ As well as modelling sites...

…the Code_Aster team is constantly strivingto improve the code’s performance levels and scopeof use. In the V7 menu : in quadratic modalcalculation, better handling of viscous and hystereticdamping thanks to the extension of the IRAMmethod; In substructuring, possibilities forassociating linear macro-elements with a nonlinearcalculation; CPU gains of a factor of two in complexand non-symmetrical for the multifrontal linearsolver; introduction of the FETI domaindecomposition method in linear mechanics.

➜ Curve boundarymonitoring…

... in adaptive mesh is nowavailable with HOMARD(encapsulated inMACR_ADAP_MAIL). In fact,when the edge of a geometry iscurved, the meshers approach itvia a succession of segments.The result is that it introducesangles where there are none!Standard adaptive division willinevitably maintain andpropagate them, which ispotentially harmful to thecalculation. The innovationconsists of placing new nodesoriginating from the division onthe actual boundary. Thesefictitious angles become flatmaking the description of thecurved boundary more accurate.Moreover, in 2D all thefunctionalities of the adaptivemesh and the mesh diagnosisopen up to quadrangles.

➜ The range ofmechanicalreliability tools…

... covers a new macro :MACR_FIABILITE. During anAster calculation it is nowpossible to evaluate theprobability of exceeding a giventhreshold depending on acertain variability of data. Inorder to do this, Code_Aster hasbeen coupled to a probabilisticsoftware application developedinternally by EDF R&D,MEFISTO. Based on a FORM typeminimization, the interactionsbetween the two cods are fed byderivatives of the target value inrelation to parameters.Whenever these sensitivities areavailable (keywordSENSIBILITE), it is advisableto use them to accelerate theprocess, otherwise they arecalculated by finite differences.

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Adaptive mesh without (fig. 2) andwith curve boundary monitoring(fig. 3).

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X-FEM :blocks incompressionwith Interfacein contact-friction.

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The dynamic behaviour ofstructures may lead to surprisesthat are not always pleasant.Resonance and the stress levels of apump rise! During an earthquake,water surface movements maycause a reservoir to vacillate !Luckily, Code_Aster can help to takebetter account of the inertia ofstructures and its unexpectedeffects during transient orstationary phenomena.

Introducing inertia terms into mechanical equationsmakes it possible to model the complexity ofdynamic phenomena and vibratory or transientaspects. Whether they are determinist or random,whether the constitutive laws are linear or not,whether or not the distortion of structures arecoupled to acoustic or fluid movements, whetherthe components come into contact or chafe,Code_Aster makes it possible to model them on amodal basis or in physical space, on the entiresystem or by substructuring.

Modal analysis

Calculating the natural frequencies and mode shapesof a material provides precious information about itsvibratory behaviour. The operators MODE_ITER_XXcalculate modal deformations and their specificpulses, with or without structural damping. Themodes can also be the basis for reducing the modeland its main freedoms of movement, thus simplifyingthe study of transients. It is, of course, possible tonormalize modes (NORM_MODE) or to filter them(EXTR_MODE) according to various conventions.

Transient or frequentialanalysis

Knowing the response of the structure to a stimulus isessential for closely analyzing strains and stressesover time. This applies whether the stressesare periodic (DYNA_LINE_HARM), transient(DYNA_LINE_TRAN, DYNA_TRAN_MODAL orDYNA_NON_LINE), expressed in seismic spectra(COMB_SISM_MODAL) or based on probabilities(DYNA_ALEA_MODAL).

Dampings

Dissipative phenomena (friction, viscosity, etc.)occur in structures; they have a significant influenceon the amplitude of responses. Damping isnevertheless often difficult to model. For thisreason, three types of damping are available :viscous, hysteretic and modal.

From measurement tocalculation

Numerical modelling makes it possible to add toexperimental measurements in areas where nosensor is available. In the frequential or temporaldomain of the usual mechanical fields,PROJ_MESU_MODAL extrapolates the desired valueusing a modal base of the numerical model.

Soil-structure interactions…

... occurring in reactor buildings or vault damsdynamics may be resolved in two ways : byfrequential coupling with MISS3D (XX_MISS_3D),integral code equation by ECP substructuring, or viaabsorbent boundary elements modelling quasi-infinite domains (XX_ABSO). In all cases theanechoicity hypothesis is checked (elimination ofplane elastic or acoustic waves diffracted by thestructure towards infinity).

Acoustics

The survey of acoustic propagation in a compressiblefluid and for closed areas is modelled (ACOUSTIQUEphenomenon) via two formulations (conventional andmixed). They solve the Helmholtz equation to deductthe noise level and acoustic intensity fields from it.

➜ Different types of fluidforce...

... are modelled in Code_Aster.In vibration under flow (combus-tible element), we distinguishtwo of these : the forces that areindependent of movement of thestructure and are due to turbu-lence or the diphasic nature ofthe flow (DEFI_SPEC_TURB) andthe “fluid-elastics” that giveconcrete expression to the actualfluid-structure coupling(CALC_FLUI_STRU). CALC_MATR_AJOU calculates thecoefficients associated with thiscoupling. It is also possible tostudy the vibro-acoustic couplingand the rattling of structuresfilled with liquid (piping, tanks,etc.) with free surface using adhoc elements (modellingsXX_FLUI_PESA/STRU...). Thisstrong coupling is processed by asymmetrical formulation (u, p, ϕ).It has recently been generalizedto the transient operatorDYNA_NON_LINE : the structuremay show any type of nonlineari-ty while the fluid remains model-led in a linear way.

Modal stresses on a generator

Dynamics

Pressure of fluid in a tank andfree surface movement.

Modelling the Grésiole dam in case of a seism : soil-structurecoupling between the civil engineering and the tank.

➜ Substructuring for bettercalculation !

Given the complexity ofmechanical structures oftenconsisting of an assembly ofseveral components,conventional numrical orexperimental methods oftenprove costly or unusable. It istherefore preferable to breakthe global model down intoseveral substructures and tostudy their vibratory behaviourseparately before connectingthem. Different types ofinterface modes are available inDEFI_INTERF_DYNA : Craig-Bampton, MacNeal or dynamicinterface methods. The surfacemeshes do not even need to becoincident – Code_Aster adaptsto incompatible connections.

Geomaterials

Why is EDF interested in modellingthe behaviour of concretes, silts,sands, clays and rocks ? Answer :beyond the behaviour of dams,there is also the appraisal ofsolutions envisaged for storingradioactive waste. Code_Aster’sthermohydromechanical models areone of the contributions of EDFR&D to the vexed question of thedownstream part of the cycle.

Nonlinears under nominal load, geomaterials areoften subject to delayed strains : predicting thestate of structures in the short and long termtherefore requires the simulation of theirconstruction phases. This is particularly true sincethe behaviour of the water soaking these materialshas mechanical consequences, especially on long-term changes to the ground and rocks. It is thereforeessential to calculate flows as such, since thecapillary effects linked to partially saturated statessignificantly influence the stress state. This isparticularly true for poorly permeable materials,where strong suctions appear.

Special constitutive laws

The phenomenologies described here can, ofcourse, only be simulated by specific Aster models.Beyond their diversity, they all share the property ofrepresenting the deterioration of materials undershear according to confinement and accompaniedby perceptible volume variations. The formulationframework will vary depending on whether it is acase of a concrete, silt, sand, clay or rock. Theformalism of damage is preferred for concretes, themicro-crack formation of which damages rigidity,whereas in the case of ground, plasticity makes itpossible to take better account of irreversiblestrains. The hardening is rendered dependent onvolume plastic strain for clays and on shear plasticstrain for rocks. In all cases, a softening behaviourappears beyond a certain threshold. For groundsand rocks, the Aster functionalities model theconcomitant dilatancy phenomena quite closely.They also model hydraulic and thermal changes –these lead directly to damage such as cracking dueto drying, collapse due to remoistening, plasticizingdue to clay swelling and ground breakdown due tothe thermal dilation of water.

An Aster offering adapted togeomaterials

For sands and silts, the first level of CJS (Cambou,Jeffari, Sidoroff) laws allows an approach of the “loadlimit” type. The second and third levels introduce acoupling between isotropic and deviatoric plasticmechanisms with isotropic or kinematic hardeningsincluding dilatancy and strain-softening for the thirdlevel.In the case of saturated clays, Cam Clay(RELATION_KIT='CAM_CLAY'), the model star,associates a nonlinear elasticity with a plasticitylimiting stresses to a domain, the size of whichdepends on the consolidation pressure. Its extensionto non-saturated grounds, known as the Barcelonamodel (see box), also makes this domain dependenton capillary pressure. For rocks, Aster has the benefitof the experience of the Centre EDF d'IngénierieHydraulique (EDF Hydraulic Engineering Centre) inChambéry, which has demonstrated the need to retainthe ‘post-peak’ (i.e. cracked) behaviour of rocks andoffered a generalization of the Hoek and Brown model('LAIGLE').Code_Aster meets the variety of hydraulic phenomenawith simple models for drying and hydrating concrete,or more complex ones based on coupled integration oftwo nonlinear flow laws and the integration of theenergy conservation law. In the sophisticated versionof this modelling with no gas pressure hypothesis, theexchanges between phases are governed by verygeneral thermodynamics equilibrium laws. The flowsare darcean, with permeabilities and saturation linkedby any laws supplied by the user. The same applies tothe relationship between saturation and capillarypressure. The distribution mechanisms withingaseous (“dry” gas and vapour) and liquid (dissolvedgases and liquid water) mixtures are governed by theFick laws.

Significant experienceof use

The age of some of these models and the length oftime they have been used have contributed toincreasing their robustness. Coupled THM modellingsare well suited to the EDF requirement : tightness ofthe containment vessels of nuclear power stations,problems connected with the deep storage of waste,re-saturation and the thermomechanics of swellingclays, damage during excavation and theconsolidation of galleries, etc.

➜ Modelling of non-saturatedgrounds...

.. has been subject to recentdevelopments : the introductionof the Barcelona model and ahydraulic coupling law takingaccount of the dissolution of agas in water and diffusionwithin this mixture.(LIQIU_AD_GAZ_VAPE).

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storage and cavities : Swedish KBS-3concept in a granitic environment.

Actual stresses at a storage site :after excavation of the gallery anddigging of wells, one year afterpackages were put in place.

Mechanical stresses in thegallery/well jointing.

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Civil engineering, concreteCivil engineering, concrete

In forecasting and controlling themechanical behaviour of civil engi-neering structures for power pro-duction such as the 58 containmentvessels and the 28 nuclear powerstation cooling towers or the 213dams, EDF’s concerns for the safetyof its installations are dominant.The resolute positioning ofCode_Aster on the nonlinear model-ling of pre-stressed reinforcedconcrete makes it possible to calmlyenvisage numerical monitoring ofsuch structures over time.

Evaluating the service life of a concrete structure aswell as anticipating and correcting its defects requireknowledge of its condition at early age or at a giventime. This creates interest in the diversity of concretemodellings, the methodology of workable surveys andthe experimental validation of these :thermohydration, drying, shrinkage, cracking,damage, creep and the effect of active and passivereinforcements. Other than physical behaviour, therange of problems to be covered is vast; for example,the tightness of concrete containment vessels fornuclear power stations and the distortion of theseover time. Added to these are the effects of accidentalloads such as earthquakes, the loss of primarycoolants or the shock of projectiles.

Physico-MechanicalBehaviour of Concrete

Changes in the properties of concrete are processedby associated thermo-hydration and drying models(Granger, Bazant, Mensi, etc.). The Aster operatorscalculate concrete shrinkage at an early age fromvariations in hydration and desiccation shrinkageusing a drying calculation. For specific creep, twomodels are available : Granger and UMLV biaxial. Forintrinsic desiccation creep, a long-term phenomenonunder the effect of mechanical loading, Code_Asterproposes the Bazant model.

Nonlinear models

The Laborderie model (uniaxial, borne by finiteelements of multifibre beams) covers static or seismicbehaviour analyses well since it takes account ofdissociated damage in traction and compression aswell as the opening and re-closing of cracks. In 2D and3D, the DDP (Double Drüker Prager) isotropeelastoplastic softening model distinguishes betweentraction and compression. The Code_Aster responseto the simulation of the creep-cracking coupling,which is the cause of potential premature rupture ofstructures, is the coupled use of the Granger and DDPmodels. In order to monitor damage to concreteby cracking, the 3D models of Badel(ENDO_ISOT_BETON), Godard (ENDO_ORTH_BETON)and Mazars can be used in both local and non-localformulation. And in case of slow convergence, it is nowpossible to resort to the rigidity secant matrix insteadof elastic or tangent matrices.

Reinforced and pre-stressedconcrete

Concrete reinforcements are modelled by finite ele-ments of bars or excentric orthotropic grids for wel-ded framework plys. Code_Aster draws mesh simpli-city and a low number of nodes from elements of thistype. The Pinto-Menegotto nonlinear law simulatesplasticizing, non-linear hardening and bucklingmechanisms; the latter is described in a phenomeno-logical way. In modelling structures in pre-stressedconcrete, stresses are better described according tothe BPEL (Pre-stressed Concrete in Limit States) rulesby disassociating the mesh of pre-stress cables fromthat of penetrated concrete. For heavily “cabled”structures such as containment vessels, the effects ofcable tension on strains of the structure can thus beaccessed.Recent developments facilitate the modelling of thispre-stressing. CALC_PRECONT thus makes it pos-sible to apply tension in the cables and find it effecti-vely at the end of the calculation. This tension can beapplied in a progressive and differentiated way, cableby cable.In the anchorage areas, punching gives rise to unrea-listic stress levels. With the new CONE option inDEFI_CABLE_BP, the user can define a volume ofrigidified concrete representing the fading cone,which is not usually present in the mesh. This is inorder to distribute the stresses over several nodes ofconcrete, thus guaranteeing a more accurate finiteelement solution.

➜ Steel concrete link

The behaviour of a structure inreinforced concrete is determinedby its components as well as bytheir interactions. The catalogueof models describing concreteand steel is supplemented bythat of the steel-concrete link,JOINT_BA. Available in 2D, itdescribes the rupture mechanismof chemical links and thecrushing of concrete and itsrelated sliding aroundreinforcements. Everything thatis essential for predicting areasof cracking.

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➜ Modellingreinforcementplys…

... is made easier by theintroduction of a new elementcalled GRILLE_MEMBRANE,which complements thetraditional BAR and GRID. This2D plate element worksunidirectionally (2 superimposedelements are necessary fordescribing a framework ply) andhave no bending rigidity.

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SANDIA area model : distorted under dead load and radialpre-stresses and stresses at the Gauss points

CALC_PRECONT :phasing of cables on a

model beam.

Internal semi-containment vessels :network of pre-stressedcables with ribs.

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➜ A new 3D concretecreep model…

(BETON_UMLV_FD) makes itpossible to take account ofstrains due to the variousshrinkages (autogeneous,thermal and desiccation) aswell as desiccation creep.

Fracture, Damage and Fatigue

The analysis of the causes ofdestruction of a structure or amechanical component must takeaccount of the actual nature of thedeterioration recorded and thedegree of fineness being sought.By offering a wide range of modelsand analysis tools from the mostwidely tested to the mostexploratory, Code_Aster covers therange of problems of damage,fracture, fatigue and limit loads.

For mechanical deterioration under repeatedloadings, we speak of “fatigue”. Otherwise it is a caseof “fracture” or “damage”. The mechanics of fracturerelies on global criteria for deciding about thepropagation of an existing crack, whereas the damagemechanics take place in the materials in order todetect the initiation and development of damagedareas.

Crack development

The conventional release rate G, the key parameter infracture mechanics, makes it possible to reach aconclusion regarding whether a crack will propagateor not. The Aster operators CALC_G_XX calculate itfor diverse situations : 2D, 3D, temperature-dependent materials, surface or volume forces, lippressure, etc. This is the case in both elasticity andelastoplasticity, provided the load remainsmonotonous and radial. The other usual criteria inelasticity, which are stress intensity factors, areaccessible in 2D and in certain 3D configurations viaCALC_G_THETA or POST-K1-K2-K3. In order toexceed these limits, POST_ELEM offers two newparameters : GTP (G-total plastic) dedicated to ductilesituations and GP (G-plastic), reserved for brittlerupture in the presence of plasticity. The lattercriterion is an extension to the plasticity of theFrancfort-Marigo formulation (RUPT_FRAG), which,based on the Griffith theory, describes the appearanceand propagation of cracks in an elastic material.Moreover, an approach relying on joint elementsbased on an interface law of the Barenblatt type(taking account of a residual interaction between thelips of the crack) makes it possible to model thedevelopment of two-dimensional cracks in a givendirection, in both static and dynamic.

Damage to structures

Cracking according to an interface law is merely amode of deterioration, the damage mechanics makefiner modelling possible because it uses the materialpoint scale. If we limit ourselves to the study of initiation in thestrictest sense of the word, the operator POST_ELEMsupplies a probability thanks to the WEIBULL model.On the other hand, if we want to model the entireresponse of the structure, from initiation todestruction, it is essential to resort to constitutivelaws coupling the development of the damage andstresses on the material point scale : for example,BETON_DOUBLE_DP, ENDO_ISOT_BETON orMAZARS for concrete and ROUSSELIER for steel.However, if they authorize finer modellings, theselaws come up against two difficulties: the instabilityof the overall response of the structure and thelocalization of strains. In order to overcome these,Code_Aster provides two innovative responses :Specific load drive makes it possible to monitorinstabilities (snap-back/through phenomena) andnon-local formulation behaviours avoid pathologicaldependence on the mesh.

Fatigue damage

Most failures of industrial components in normal ope-ration are due to fatigue. Its latent nature is onlyequalled by its noxiousness, which is why the evalua-tion of this type of phenomenon is important from thedesign stage.Depending on the type of fatigue (with large numberof cycles, oligocyclic, etc.) the type of stresses (deter-minist, random, periodic, multiaxial, etc.), availableinput data (component or stress tensor, etc.) and desi-red results (field in one point, criterion, etc.),Code_Aster offers the most suitable method (operatorXX_FATIGUE...). From the traditional WOHLER to theDang Van Papadopoulos via the TAHERI “in-housemethod”, the range of combinations processed iswide.

➜ Initiation criterion infatigue

In order to respond to theproblem posed by thermalfatigue, multiaxial initiationcriteria in fatigue with a largenumber of cycles have beendeveloped. The idea consists ofsearching for the normaldirection, for which either theshear semi-amplitude or thedamage is maximum. With thesecriteria, periodic or non-periodicloads can be analyzed.

➜ The anisotropycaused bydamage within theconcrete…

is taken into account in theENDO_ORTH_BETON law. Thelatter also makes it possible toreport the unilateral character ofthe behaviour of the concrete(traction/compressiondissymmetry, effect of crackclosure).The non-local version of this lawis available via the GRAD_EPSIstrain control method.

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RRA circuit elbow :damage calculation bythe Dang Van criterionand thermal crazing.

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➜ Modelling thesteel-concretelink…

... is done in 2D using jointelements based on a constitutivelaw JOINT_BA describing thedamage to and rupture of thesteel-concrete link.

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Joint elements for modelling the developmentof a crack in a perforated plate....

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Everything would be easier if onlyone domain of physics played a partin structure mechanics. But in thepower industry, as elsewhere, thephenomena are often coupled.Code_Aster offers tools for makingchainings or couplings ofphenomena internally as well asexternally with other specializedcodes.

For multiscale and multiphysics, it is possible todistinguish the internal and external approaches ofthe code. In the first case, the multiplicity of thephysics is directly taken into account by Code_Aster,whereas in the other case the interaction is doneeither by coupling or by chaining with anothercalculation program.

Internal approaches

Thermomechanical chaining for surveys withtemperature-dependent materials with thermal orhydration-drying-shrinkage changes.By strongly coupling the thermal, hydraulic andmechanical (thermohydromechanical) equations, weare interested in porous media, whether or not theseare saturated : rocks, clays, concretes.In thermo-metallo-mechanics, used in particular forthe simulation of multipass welding, the behaviour ofsteels due to phase changes can be modelled in 2Dand 3D.The fluid-structure interactions make it possible tocalculate the vibrations of a structure containing (orrunning in) a fluid that is resting or flowing.A power-mechanical chaining provides the dynamicsof structures subject to the induced Laplace forces.

Finally, multiscale enters the code with two newfunctionalities : the Arlequin method(keyword ARLEQUIN) and the micro-macro (DEFI_COMPOR).The first connects digital models ofdifferent natures using asuperimposition technique. This opensnumerous perspectives. For example, it is possible tocarry out structural zooms within areas particularlysensitive to loads : cracks, welds, support structures,etc.The micro-macro makes it possible to manipulate theconstitutive laws in a modular way on diverse scales(see box).

External approaches

Code_Saturne chaining (EDF-CEA, thermohydraulicsfor fluid) – Syrthes (EDF, thermal change for thewall) – Code_Aster (structure) with temperature orpressure field interpolation on the mechanicalmesh.Code_Aster – Europlexus chaining (fast dynamicscode from the EDF-CEA-CCR/Ispra-SNECMA-Samtech consortium).Exporting analysis results to LADY (experimentalvibratory analysis). Calculating displacements andstresses brought about by static and seismic loadsfrom a model defined in CIRCUS (vibrations underpipework flows).Frequential response by MISS3D (code of integralequations for propagating PECP waves) to a seismicexcitation for stratified soils or ones with no fluiddomain.Importing into Code_Aster of volume stress fieldsdelivered by the electromagnetism code Flux2D/3Dwith a view to calculating the thermomechanicalbehaviour of transformers or electric motors.

➜ Thanks to the MED format(Modelling and DataExchange...

... of finite elements developedby EDF-R&D and the CEA,Code_Aster exchanges meshes,topological entities and resultswith other codes. The structureof the latter is relatively rich :all types of fields by elementsand size fields, fields that areeither defined or not definedthroughout, and fields involvingheterogeneous components.This richness, which guaranteesthe opening to use of non-proprietary pre- and post-processing tools, has a singleinput point, FORMAT=’MED’, inLIRE_MAILLAGE, LIRE_CHAMPand IMPR_RESU.

➜ Micro-macro

DEFining aBEHaviour fromelementary bricks :a given flowing law, kinematichardening or other isotrope,make it possible to avoiddefining all the combinedbehaviours. Via the operatorDEFI_COMPOR, these bricks areassociated with a monocrystaland its sliding systems, thuscreating a behaviour modelpeculiar to a group of meshes inSTAT_NON_LINE. We can nowcarry out calculations ofaggregates where everychained grain is made up of anoriented monocrystal.This new “micro-macro”functionality opens the way to afully modular multiscale. Allthat needs to be done is tointegrate these various scalesinto a polycrystal made up ofseveral monocrystals and todefine a localization rule for thewhole thing and the calculationcan be started !

Code_Saturne/Code_Aster chaining on an Alstom-Velan glovevalve : mesh and internal fluid pressure field.

From multiscaleto multiphysics

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Micro-macro :Maximum stress

isovalues on apolycrystalline

aggregate.

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Product

The General, Functionalities and Modelling Domainscategories resume and develop the chapters of thisCode_Aster V7 brochure. The transparencies presentedat the Annual User and Free Code_Aster open days arealso available. The Applications section is devoted toAster industrial surveys. The distinction between theFree, Development and Operation versions isexplained in the Versions section. The Quality sectiongives details of the acceptance criteria for changes andcorrections. Finally, the Tools section lists programsusing or used by Code_Aster.

Use

The Documentation section provides allthe code’s technical documentation : forUse, Reference, IT Description andValidation. The Administration Dossier(quality procedures) and the documen-tation relating to the qualified EDF ver-sion are in restricted access in this sec-tion. For Familiarization, in theExamples and Training section, illustra-ted examples with comments and com-mand files are available together withpractical exercise and training media.

Development

The rules applying to developing andhaving your development validatedwithin the centralized version are givenin the Presentation section. InOrganization, the successive updatehistories of the development versionare available together with reports(restricted access) and anorganizational chart of the participantscontributing to code developments.

Training looks at development training course mediaand in NEW Version you can find information aboutenriching your own overloads with weekly versionpatches.

Services

The List and Command category explains the type ofaccess to Code_Aster and its dedicated tools for EDFand its partners (account management, hotlineassistance, etc.). For everyone, Program Anomaliesand Software Changes look at the error collectionand development processing system as well as thetools and documentation for it. Other sections dealwith Modelling Optimization Help (AOM), the Users’Club, the centralized server, not forgetting theessential Forums (see box).

Downloading

This section provides access to downloads for thecode as well as its tools and pre-requisites : aster, thesource code of the various version, astk surveygraphics manager, GIBI mesher and post-processingof the CAST3M code, Gmsh free mesher and post-processing, Eficas intelligent Aster commandgraphics editor, METIS node re-numbering algorithmadapted for Aster, MED data exchange module andHDF5, its library, etc.

➜ The Forums

These very active forums are aprivileged place for exchangesbetween users and developers,both inside and outside EDF.They are divided into themes :Use, Installation andDevelopment.

➜ All in one !

Linux version 7.4 hasinaugurated a new distributionmethod : all in one! The aster-full packages, which can bedownloaded from the site,supply the program’s sourcecode and all the necessary toolsand prerequisites. Installationhas been made much easier andis usually limited to a singlecommand line.

➜ Code_Aster as a freeprogram ! Why ?

The answer is clearlyrecognition and enrichmentthrough use. Defects areidentified fully and morequickly, while diverse know-howand the creativity ofprofessional contributions willfinally speed up and guaranteebetter validation/qualification ofmodels by users of the network.Beyond the technical aspect, thepolitical dimension provided byEDF R&D and its FreeCode_Aster under GPL license(General Public License), thefruit of the skill and qualityrequirements in nuclearengineering, is resolutelypositioning itself within theinnovation – industry transfer.This process is intended tostimulate Aster contributionsfrom both the public and privatesectors (see AE no. 43) byoffering them in return asustainable and reusableplatform for their own work.Code_Aster Free can bedownloaded biannually andeach time benefits from theAster methodology of non-regression, precision andperformance of the existingprogram.

Code_Aster, the website and the free version

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The home page gives information about important facts(new version, events, etc.)

and guides you throughout your tour.

The www.code-aster.org website,the code’s multimedia base, meetsthe double requirement of being atthe service of the users anddevelopers and supporting itsdistribution as a free program.Guided tour of the sections andcategories of the site, taking a lookat the technical and politicalmotives of making Code_Asterfreely available.

Products and services

Since 1989, Code_Aster has beenrecognized within EDF as thenumerical simulation tool deliveringinnovations essential to the expertappraisal of problems in a timelymanner. Version 7 confirms its dualmission : a qualified andoperational calculation tool thattakes on board developmentsoriginating in research.

Quality throughtransparency andvalidation

The Aster quality criteria governing the developmentand distribution of the code are based on anauditable quality frame of reference meeting therequirements of the EDF Nuclear Structures SafetyAuthority. These criteria constitute the AsterProgram Quality Plan and are defined in the codeAdministration Manual. The theoretical foundationsof Aster models are documented in the ReferenceManuals. The independent validation of theoperational versions of the code, which are carriedout by external calculation companies, deals withthe program’s conformity with regard to itsdocumentation, the actual cover of the declaredanalysis domains and non-regression in terms ofprecision/performance. The Quality Sheetaccompanying each operating version is updatedper subversion (corrected errors, applicabledocumentation).

A central team of aroundtwenty EDF R&Dengineers…

... is devoted to the consistency and quality of theAster platform (1,700 validation or non-regressiontests) : architecture, tools, versioning, putting intooperation, Feedback management, validation,documentation, communication, training, etc. It is alsosurrounded by participants in EDF applicationprojects, industrial and university research and surveyand services suppliers. More than 70 engineers havethus participated in V7.

➜ Feedback…

... is a precious tool in the development process. Itcollects user requests, indexes anomalies foundand monitors changes to these over time. It nowuses Intranet technologies in order to manage adatabase of more than 5000 records.

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Products

The Aster architecture, 1,200,000 lines of FORTRAN in object design (250,000 ofwhich are new or modified in V7), supported by C and Python, is based on a diskmemory/image manager, a command “supervisor” and an EF calculation engine(algorithms independent of finite element formulation). Its opening relies on wideuse of catalogues describing the commands and finite elements.

Code_Aster is available in three forms…

... Operation, development and free, all originating from a unique source code. Thissource together with its tools and prerequisites are maintained and validated underUnix and Linux, but the Free Aster community has demonstrated the feasibility oftheir portage under Windows, MacOS, etc.

The Operating Version (V7.4 in Dec. 2004) meets the IPS (Important for Safety) qua-lity requirements. It was subject to corrective maintenance and additional validationsand documentation over a two-year period. This is the version for EDF users and theirauthorized suppliers. It will remain available for 2 more years for resuming surveys.The Development Version (V8.0 in December 2004) is enriched every week by cor-rections, improvements and innovations (40 updates annually). It will become theOperating Version after a development cycle of 2 years and after qualification.The Unix Aster operation and development codes areaccessible to EDF and its partners on the centralizedserver.The biannual version of Free Code_Aster is editedunder GPL license on www.code-aster.org. It origi-nates from the packaging of the currentDevelopment version. Weekly patches make it pos-sible to keep it updated.

Documentation

Use (general, command syntax, examples), IT Description (architecture, memorymanagement, supervisor, data structures), Reference (formulations and algorithms)and Validation (elementary mechanics or non-regression tests). In V7 : 13,000 pages(60% of the corpus renewed) can be accessed on www.code-aster.org.

Training and help with modelling

The value of a simulation program also relies on theskill and critical minds of its users. These qualitiesare acquired through significant initial and ongoingtraining. Aster courses offer training at all levels :“Initiation” to the code or its “Development”,learning to handle “Post-Processing” or “SurveyQuality” tools, “Dynamic” and “Static Nonlinear”analyses.

➜ More and more…

... calculation resources forCode_Aster users : a centralizedAlphaserver Tru64 ES45machine (24 processors at 1GHz,100 GO memory, 48 Gflops), acluster of 10 Opteron 64 bitprocessors and access to themassively parallel machines ofthe Research and TechnologyCalculation Centre (CCRT) of theCEA.

➜ AOM service…

... for Aide à la Modélisation(Modelling Optimization Help)provides the necessary expertisefor complex or innovativesurveys. Contact : code-aster@edf.fr.

The traditional Users’ Day in theAilleret Room (EDF R&D, Clamart)

Products and services

Code_Aster, a user-friendly program

High level calculation is no longersynonymous with “difficult to use”.Today, ergonomic interfaces make itmuch easier to used the code.EFICAS, ASTK and STANLEY define,carry out and post-process yourcalculation in a few clicks.Eventually the SALOME programenvironment platform will increasethese possibilities.

ASTK

The provision of a multi-platform, multi-version IT tool that is used and co-developed byvarious teams has to be done through a Study and Developments Manager. This is ASTK’sraison d’être : selecting the code version, accessing to the various calculation servers,defining the files comprised in a study, defining job type (batch or interactive), creating anoverloaded version, accessing configuration management tools for developers andmanaging Feedback anomalies and changes records. The rapid development of centralizedcalculation systems and Free Code_Aster distribution have accelerated the mutation of theformer ASTERIX survey tool. Its successor, ASTK, has adopted tcl/tk type architecture,which is more modular and portable.The choice of client-server architecture authorizes clear separation between the interfaceand the code access tools. ASTK thus integrates in a single interface all the Atelier de GénieLogiciel Aster (AGLA, Aster Program Engineering Workshop) tools used to manage thebatch reference version (batch processing) and those of local versions.This interface uses network protocols for transferring files between clients and server, orfor starting remote commands, including over the Internet. Users can easily distribute theirdata files and results to different machines as the interface ensures the transfer of files,including compressed ones, over the network.As well as Code_Aster, ASTK makes it possible to use different tools selected by users,such as EFICAS and STANLEY or mesh and visualization programs. For users wanting tomonitor weekly changes to the code, nothing could be easier – ASTK handles everything!Getting update files from the site and reconstructing the executable.

STANLEY

The STANLEY application is an interactive post-processing tool for Aster calculations. Itfacilitates accessing the lists of fields available in the results data structures (displace-ments, stresses, internal variables, etc.), calculating new ones, extracting sub-parts fromthese and visualizing them in isovalues (with Gmsh) or curve form (with Xmgrace). It isalso possible to create new geometric locuses for post-processing (point or straight).STANLEY, which has become an Aster command in its own right, is easy to use : all youhave to do is add STANLEY () to the end of the command file.It adapts to any configuration : workstation under Unix, Linux or Windows, calculationlocally or on a remote server. Setting its parameters allows multi-configuration manage-ment and everything is memorized from one session to the next.

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STANLEY : theCode_Aster results

explorer.

EFICAS : Intelligent Aster command graphics editor.

ASTK : theCode_Aster use anddevelopment hub.

EFICAS

Writing the command file code directly “by hand” in atext editor can prove tedious and be a source of set-backs. It forces you to continually navigate within thedocumentation of commands in order to find their syn-tax, search for missing parentheses and forgotten com-mas, etc.The EFICAS Command File Editor and Syntax Analysermakes life much easier. It is a program with user-friend-ly GUI (Graphic User Interface), which directly gene-rates files with guaranteed syntax according to userchoice. By interpreting the command catalogues itautomatically manages syntax and keywords as wellas the required rules and expected concept types.

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Advanced user scan easily work onthe code, partly thanks to PYTHON,for example to : write professionalapplications, introduce finiteelements and constitutive laws ordefine exchange formats.

Command languages

The Code_Aster user describes the parameters andprogression of the survey in a text file. This is madeup of commands, which themselves containkeywords and receive as arguments : texts, integers,reals… or names of concepts created beforehand byother commands. These concepts are objects namedby the user, produced by commands and that canpotentially be used or modified by other people.The grammar and vocabulary of this language,which is specific to Code_Aster and written in thePYTHON base, are described in catalogues. Tocreate correct command files the user must eitherknow the basic PYTHON script rules and find outabout the syntax of each command from thedocumentation or, more interactively, use theEFICAS graphic command input.

Supervisor and PYTHON

For more advanced use, with PYTHON users mayintroduce programming in their datasets : fromsimple ones (check, loop and test structures) tomore complex ones using all the richness of thisinterpreted language (methods, classes, importingexogenous modules such as Tklnter for GUI,numerical for mathematical uses, etc.).In this illustration, during a single job and with nofile handling by the user, the same calculation is runseveral times by calling a remote modeller / mesherwith a modification of the elbow bending radius. Theloop stops conditionally on a stress limit value.

All FORTRAN memory basic objects can be obtained by the user from the PYTHONarea : this example looks at a maximum stress indicator in the pipe elbow. For themost useful and general global concepts (tables, results, fields, meshes), gatewaysexist for obtaining a PYTHON representation for the purpose of manipulating thislanguage.Moreover, it is possible to easily define macro-commands written directly inPYTHON in the command file. This makes it possible to encapsulate a sequence ofrecurring commands and to clean out its inputs-outputs. The user no longer has tooverload the executable to take advantage of this! The development of line tools hasbeen made much easier.However, a file containing instructions other than the official commands cannot beeither produced or edited by EFICAS. Using the functionalities described aboveconstitutes "advanced” use of the code, which is not currently supported by thistool.For chaining with other codes, everything is possible : launching a third partyexecutable by EXEC_LOGICIEL or direct submission in PYTHON; MED should bethe preferred format for field and mesh exchanges.

Finite elements and constitutive laws

If your problem does not adapt to the 95 constitutive laws currently present,programming or modifying a constitutive law is easy. After consequently enriching theorder catalogues DEFI_MATERIAU and STAT/DYNA_NON_LINE, as keywords makeit possible to introduce input parameters the routine integrating this constitutive lawmust be written. This provides the elementary data essential to the resolutionalgorithm (constraint tensor and updated internal variables, tangent matrix, etc.).Various utility programs facilitate this integration and ensure its reliability.The same applies to finite elements if you do not find a suitable element among the 360existing ones, you may create your own. If the procedure described in the developmentdocumentation is followed, introducing a new finite element is modular and does notrequire a command of the entire code.

Pre-post exchanges in different formats

Code_Aster is also a flexible solver thanks to the number of exchange and data storageformats it has. Mesh, fields and results can be read and written in most knownstandards. In PYTHON, plotting a mesh translation and results interface in a new formatis easy. The memory image of calculated objects, which may be retained afterexecution, may be written in a portable format on any platform.

Code_Aster, a flexibleand open program

Optimizing the bending radius ofan elbow by Gmsh-Code_Asterchaining.

Calculation of the effects of swell on awind turbine pylon with Code_Aster

STREAM-GIBI chaining.

Contact : code-aster@edf.fr

Design : Olivier Boiteau and Emmanuel BoyereTranslation : Bruno Zuber (www.necs.fr)Proofreading/Editing : Jean-Michel Proix and Christophe DurandRelease Manager : François WaeckelArchiving : HT-66/05/010/A

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EDF R&D1, avenue du Général-de-Gaulle 92141 Clamart cedex www.edf.com EDF SA au capital de 8 129 000 000 euros - 552081317 RCS Paris