# BS EN 16603-32-03-2014

BSI Standards Publication BS EN 16603-32-03:2014 Space engineering — Structural finite element modelsBS EN 16603-32-03:2014 BRITISH STANDARD National foreword This British Standard is the UK implementation of EN 16603-32-03:2014. The UK participation in its preparation was entrusted to Technical Committee ACE/68, Space systems and operations. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. © The British Standards Institution 2014. Published by BSI Standards Limited 2014 ISBN 978 0 580 83983 2 ICS 49.140 Compliance with a British Standard cannot confer immunity from legal obligations. This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 August 2014. Amendments issued since publication Date Text affectedBS EN 16603-32-03:2014EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM EN 16603-32-03 August 2014 ICS 49.140 English version Space engineering - Structural finite element models Ingénierie spatiale - Modèles éléments finis pour les structures Raumfahrttechnik - Strukturmodelle der finiten Elemente Methode This European Standard was approved by CEN on 10 February 2014. CEN and CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN and CENELEC member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN and CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions. CEN and CENELEC members are the national standards bodies and national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels © 2014 CEN/CENELEC All rights of exploitation in any form and by any means reserved worldwide for CEN national Members and for CENELEC Members. Ref. No. EN 16603-32-03:2014 EBS EN 16603-32-03:2014 EN 16603-32-03:2014 (E) 2 Table of contents Foreword 4 Introduction 5 1 Scope . 6 2 Normative references . 7 3 Terms, definitions and abbreviated terms 8 3.1 Terms from other standards 8 3.2 Terms specific to the present standards . 8 3.3 Abbreviated terms. 9 3.4 Symbols 10 4 General requirements. 11 4.1 Overview 11 4.2 Coordinate systems and unit system 11 4.3 Modelling requirements 12 4.4 Requirements for reduced models 12 5 Model checks 14 5.1 General . 14 5.2 Model geometry checks for non reduced models 14 5.3 Elements topology checks for non reduced models 14 5.4 Rigid body motion checks for reduced and non reduced models 15 5.4.1 Overview . 15 5.4.2 Rigid body motion mass matrix . 15 5.4.3 Rigid body motion strain energy and residual forces check . 15 5.5 Static analysis checks for reduced and non reduced models 16 5.6 Stress free thermo-elastic deformation check for non reduced models . 17 5.7 Modal analysis checks 18 5.8 Reduced model versus non reduced model consistency checks . 18 6 Test – Analysis correlation 19 6.1 Overview 19 BS EN 16603-32-03:2014 EN 16603-32-03:2014 (E) 3 6.2 Provisions . 19 Bibliography . 20 BS EN 16603-32-03:2014 EN 16603-32-03:2014 (E) 4 Foreword This document (EN 16603-32-03:2014) has been prepared by Technical Committee CEN/CLC/TC 5 “Space”, the secretariat of which is held by DIN. This standard (EN 16603-32-03:2014) originates from ECSS-E-ST-32-03C. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by February 2015, and conflicting national standards shall be withdrawn at the latest by February 2015. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. This document has been developed to cover specifically space systems and has therefore precedence over any EN covering the same scope but with a wider domain of applicability (e.g. : aerospace). According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. BS EN 16603-32-03:2014 EN 16603-32-03:2014 (E) 5 Introduction The concept of model is of primary importance in all the fields of the science. In engineering disciplines - and specifically in structure mechanics - a model is a representation, able to describe and predict the behaviour of a structure in terms of quantifiable variables. A first step to build a model is to choose the variables which are relevant to the studied phenomenon (e.g. displacements, stress, or frequencies) and the types of relationships among them (e.g. the theories provided by elasticity, plasticity, stability, statics, or dynamics): this representation is called the physical model. The second step is to build a mathematical representation (e.g. using differential equations, integral equations, or probability methods): this representation is called the mathematical model. A third step is to build a numerical model, which is a formulation of the mathematical model by means of numerical algorithms, based on several approaches (e.g. the finite element method, the boundary method, or the finite difference method). A finite element model of a structure is such a type of numerical model of structure behaviours. This Standard is restricted only to the requirements for finite element models of space structures, to be fulfilled to ensure modelling quality, i.e. the correct use of this specific technology – the finite element method - and the acceptance of the results. BS EN 16603-32-03:2014 EN 16603-32-03:2014 (E) 6 1 Scope ECSS-E-ST-32-03 (Space engineering – Structural finite element models) defines the requirements for finite element models used in structural analysis. This Standard specifies the requirements to be met by the finite element models, the checks to be performed and the criteria to be fulfilled, in order to demonstrate model quality. The Standard applies to structural finite element models of space products including: launch vehicles, transfer vehicles, re-entry vehicles, spacecraft, landing probes and rovers, sounding rockets, payloads and instruments, and structural parts of all subsystems. This standard may be tailored for the specific characteristics and constrains of a space project in conformance with ECSS-S-ST-00. BS EN 16603-32-03:2014 EN 16603-32-03:2014 (E) 7 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this ECSS Standard. For dated references, subsequent amendments to, or revision of any of these publications, do not apply. However, parties to agreements based on this ECSS Standard are encouraged to investigate the possibility of applying the more recent editions of the normative documents indicated below. For undated references, the latest edition of the publication referred to applies. EN reference Reference in text Title EN 16601-00-01 ECSS-S-ST-00-01 ECSS system – Glossary of terms EN 16603-32 ECSS-E-ST-32 Space engineering – Structural general requirements BS EN 16603-32-03:2014 EN 16603-32-03:2014 (E) 8 3 Terms, definitions and abbreviated terms 3.1 Terms from other standards For the purpose of this Standard, the terms and definitions from ECSS-S-ST-00-01 and ECSS-E-ST-32 apply. 3.2 Terms specific to the present standards 3.2.1 constrained DOF DOF which has a known value, given as input 3.2.2 degrees of freedom scalar components of the solution vector in the FE method NOTE Examples of DOF are displacement and rotation components, and other physical quantities as beam warping variable, or modal coordinates. 3.2.3 dependent DOF DOF which is computed from the values of other DOF, by means of a multi- constraint equation, provided as additional modelling input NOTE Examples of multi-constraint equations are the rigid body relationship of two or more DOFs. 3.2.4 dynamic reduction (also referred as dynamic condensation) method to reduce the FE model size by means of a transformation of the full set of FE DOFs in a set of modal coordinates, and a subset of retained displacement and rotation components NOTE There are several methods of dynamic reduction (e.g. Craig-Bampton, MacNeal). 3.2.5 free DOF unconstrained independent DOF 3.2.6 modal DOFs (also referred as modal coordinates) DOFs related to a basis of dynamic eigenmodes BS EN 16603-32-03:2014 EN 16603-32-03:2014 (E) 9 3.2.7 output transformation matrix matrix which pre-multiplies the reduced model DOF vector or its time derivatives to obtain the value of remaining non-retained DOFs and output variables (e.g. element force and stress) 3.2.8 quantifiable structure variable structure property which can be measured and is chosen to quantify a structure behaviour NOTE Examples of quantifiable structure variables are: displacements, stresses, natural frequencies, material properties, element properties, loads, temperatures. 3.2.9 rigid body motion matrix matrix which has as columns the vectors of rigid body displacements 3.2.10 size of FE model number of all the DOFs of the FE model 3.2.11 static reduction (also referred as static condensation) method to reduce the number of the DOFs in a model by means of a reduction transformation matrix or constraint modes matrix. NOTE Guyan reduction is a widely employed method of static reduction. 3.2.12 structural model representation of a specific structure behaviour - described by a chosen sets of quantifiable structure variables - by means of relationships which predict the values of variables subset (named output variables) as depending from the remaining variables (named input variables) 3.3 Abbreviated terms For the purpose of this Standard, the abbreviated terms from ECSS-S-ST-00-01 and the following apply: Abbreviation Meaning DOF degree of freedom FE finite element OTM output transformation matrix BS EN 16603-32-03:2014 EN 16603-32-03:2014 (E) 10 3.4 Symbols The following symbols are defined and used within this Standard: Symbol Meaning ER rigid body motion strain energy matrix FR rigid body motion residual nodal force vector K stiffness matrix M mass matrix ΦR rigid body motion matrix BS EN 16603-32-03:2014 EN 16603-32-03:2014 (E) 11 4 General requirements 4.1 Overview The Finite Element (FE) models are categorized as follows: • ‘Non-reduced’ models: defined only by nodes and finite elements (with their properties), and using as DOFs the node displacements and rotations. • ‘Statically reduced’ models: defined by nodes and matrices obtained from static reduction, and using as DOFs the node displacements and rotations. • ‘Dynamically reduced’ models: defined by nodes and matrices obtained from dynamic reduction, and using as DOFs both modal coordinates and node displacements and rotations. NOTE 1 ‘Reduced’ models are also referred to as ‘condensed’ models. NOTE 2 Combinations of non-reduced and reduced models can be used. 4.2 Coordinate systems and unit system a. All local coordinate systems of the mathematical model shall refer, directly or indirectly, to a unique local coordinate system that is defined with respect to the basic coordinate system. NOTE 1 The basic coordinate system is a Cartesian rectangular system having the origin in x=0; y=0; z=0. NOTE 2 The requirement allows easy merging of different FE models. b. The following units should be used for FE models: 1. meter, for length 2. kilogram, for mass 3. second, for time 4. newton, for force. BS EN 16603-32-03:2014 EN 16603-32-03:2014 (E) 12 4.3 Modelling requirements a. Modelling guidelines shall be established and agreed with the customer. NOTE Guidelines are established at least on the following modeling aspects: • Types of elements to be used or avoided • Aspect ratio thresholds for the elements • Warping threshold for shell elements • Types of springs to be avoided (e.g. non-zero length) • Types of permitted rigid elements • Modelling of the offset of elements • Modelling of bolted and riveted connections • Specific aspects of dynamic models • Specific aspects of the thermal stress models (e.g. ability to represent temperature discontinuities due for instance to thermal washer) • Specific aspects of non-linear analysis models • Specific aspects for axi-symmetric models, cyclic symmetry models and Fourier series development • Suggested, required and to-be-avoided analysis related parameters • Mesh density • Mesh refinement • Interface definition • Numbering rules • Coordinate system definition • Definition of equivalent properties • Fluid effects (e.g. sloshing, added mass) 4.4 Requirements for reduced models a. The static behaviour of the structure shall be described by the reduced stiffness and mass matrices, and reduced force vector relative to the retained degrees of freedom. b. The dynamic behaviour of the structure shall be described by the reduced stiffness, mass and damping matrices, and reduced force vector relative to the retained degrees of freedom. c. The reduced model shall be supplied with related instructions for model integration. BS EN 16603-32-03:2014 EN 16603-32-03:2014 (E) 13 d. The modal DOFs shall be ordered in the matrices according to the mode numbering sequence. e. The numbering range of the modal DOFs shall be outside of numbering ranges of other DOFs (e.g. node displacements). f. Output Transformation Matrices (OTMs) shall be provided and separated according to the type of output. g. OTMs shall be supplied with related user instructions and output item lists. h. A specific format of reduced matrices and OTMs shall be agreed with the customer. i. OTMs shall be verified by consistency with non reduced model (see clause 5.8) j. OTMs provided for the recovery of displacements and displacement- related data (e.g. elemen