Short Introduction to LS-DYNA and LS-PrePost
Contents
1. Create a new rigid body using existing nodes PID Part id req is a unique one CID Coordinate system for output NSID Node set PNODE Optional centre node IPRT Print flag For spot welds and other types of rigid connections Initial Boundary Conditions 2013 09 09 53 CONSTRAINED CONSTRAINED_JOINT_ JOINTTYPE N1 N2 N3 NA N5 N6 RPS DAMP Define mechanical joints between rigid bodies N1 N6 Nodes in the rigid bodies RPS Scale the penalty stiffness DAMP Dynamic damping N1 N3 N6 in RB1 N2 N4 N6 in RB2 Place the nodes in one RB far apart N1 N2 etc initially coincident except universal joint read the manual Motor and gear joints are available for advanced mechanisms DV NA Initial Boundary Conditions 2013 09 09 54 WV O RE norDbic CONSTRAINED Sa Cylindrical T Spherical Translational Locking Universal 59 Contacts Some of the available contacts CONTACT_option_option_ AIRBAG_SINGLE_SURFACE AUTOMATIC_GENERAL AUTOMATIC_GENERAL_INTERIOR AUTOMATIC_NODES_TO_SURFACE AUTOMATIC_NODES_TO_SURFACE_TIEBREAK AUTOMATIC_ONE_WAY_SURFACE_TO_SURFACE AUTOMATIC_SINGLE_SURFACE AUTOMATIC_SURFACE_TO_SURFACE AUTOMATIC_SURFACE_TO_SURFACE_TIEBREAK CONSTRAINT_NODES_TO_SURFACE CONSTRAINT_SURFACE_TO_SURFACE DRAWBEAD ERODING_NODES_TO_SURFACE ERODING_SURFACE_TO_SURFACE FORCE_TRANSDUCER_CONSTRAINT FORCE_TRANSDUCER_PENALTY FORMING_NODES_TO_SURFACE_TIEBREAK FORMING _ONE_WAY_SURFACE_TO_SURFA2. E Young s Modulus RO Density PR Poisson s Ratio SIGY Yield stress ETAN Tangent modulus BETA Hardening parameter FS Failure strain SRC strain rate parameter C VP Rate formulation flag SRP Strain rate parameter P DV N A Material Models 2013 09 09 44 M O RE norDiIic Elastic plastic material with Bauschinger efftect Definition of material hardening Kinematic hardening Isotropic hardening Other models with kinematic hardening MAT_PLASTIC_GREEN NAGHDI RATE MAT_ANISOTROPIC_VISCOPLASTIC MORE norpic EOS Certain material models only solve for the deviatoric part of the stress tensor An Equation of State EOS is required to find the pressure part of the stress tensor Mostly used in conjunction with fluid like behaviour high explosives airbag inflation Solid elements only 46 Boundary Initial Conditions Initial and Boundary Conditions Variation in time using load curves Variation in space Traction t Arbitrary directions using iii Local coordinate systems Vectors But limited to cartesian coordinates u t 48 LOAD LOAD NODE SET POINT NODE NSID DOF LCD SF CD M M M3 Nodal loads for one node or a set of nodes DOF _ Direction of load in current coordinate system LCID Load curve ID for variation in time SF Scale load curve amplitude CID Define a local coordinate system E M1 M3 Follower force definition Singularities at point loads may be a problem F M3
3. Multiple load cards are accumulated A MI M2 Initial Boundary Conditions 2013 09 09 49 INITIAL INITIAL_STRESS _BEAM _SHELL _ SOLID INITIAL_STRAIN _SHELL _ SOLID Initialise the state of stress and strain in elements Normally used to carry results obtained in one simulation to another Multistage forming Forming gt Crash Keyword data normally generated automatically by preprocessors Initial Boundary Conditions 2013 09 09 50 Kinematic Conditions Prescribe motion in the model BOUNDARY w r t cartesian coordinates Fixed supports Symmetric boundaries CONSTRAINED internal definitions Mechanical Joints Merging shell brick elements Define rigid bodies 21 BOUNDARY_PRESCRIBED_MOTION_ BOUNDARY PRESCRIBED MOTION NODE SET RIGID ID DOF VAD LCID SF VID DEATH BIRTH Apply nodal displacement velocity or acceleration to the model translations or rotations DOF Direction of load global or local direction see manual VAD Type of load LCID Load curve ID for variation in time SF Scale amplitude of the loadcurve VID Vector ID for vector to be used if DOF 4 or 8 DEATH BIRTH Active range of time for this boundary condition Use the RIGID option for rigid bodies For local directions with rigid bodies see the MAT RIGID keyword Fo w INT ZA Initial Boundary Conditions 2013 09 09 52 WV O RE norDbic CONSTRAINED CONSTRAINED_NODAL_RIGID_BODY PID CID NSID PNODE IPRT
4. CE FORMING _SURFACE_TO_SURFACE NODES_TO_SURFACE NODES_TO_SURFACE_INTERFERENCE ONE_WAY_SURFACE_TO_SURFACE RIGID_NODES_TO_RIGID_BODY RIGID_BODY_ ONE_WAY_TO_RIGID_BODY RIGID BODY TWO WAY TO RIGID BODY SINGLE EDGE SINGLE SURFACE SLIDING ONLY SLIDING ONLY PENALTY SURFACE TO SURFACE SURFACE TO SURFACE INTERFERENCE TIEBREAK NODES TO SURFACE TIEBREAK SURFACE TO SURFACE TIED NODES TO SURFACE TIED NODES TO SURFACE OFFSET TIED SHELL EDGE TO SURFACE SPOTWEALD SPOTWEALD WITH TORSION TIED SURFACE TO SURFACE TIED SURFACE TO SURFACE OFFSET Contact A way of treating interaction between different parts are defined by sets node part segments or a 0X Generally there is a master side and a slave side of the contact The master side can be a mathematically described with a geometrical surface rigid The thickness of shells are normally taken into account Most recommended contacts are based on the penalty method Several contacts treating special applications exists Old contact types kept for compatibility reasons Motion Am MASTER 1 o Interesting Keywords for Contacts Contacts in LS DYNA is affected by many different keywords SECTION SHELL Shell thicknesses middle top bottom surface meshed MAT xxx Penalty stiffness E pr dens m u DEFINE_FRICTION Friction behavior between parts PART CONTACT Contact behavior for parts CONTROL_CONTACT Overall contact behavior CON
5. Short Introduction to LS DYNA and LS PrePost Jimmy Forsberg Content DYNAmore Nordic presentation Introduction to LS DYNA General work with different solvers LS DYNA capabilities Keywordfile structure Introduction to LS PrePost Layout Pre processing Post processing Special features Composite tool DYNAmore Group CAE Software Engineering services Distributor for LSTC Personnel 70 LSTC code developer 10 Head office in Stuttgart Germany DYNAmore Group Sweden 17 Employees 3 years in average 9 Ph D 8 M Sc 1 Economics Adm Office in Link ping Office in Goteborg sus E pelei LL DYNAmore GmbH Germany 60 Employees Headquarters in Stuttgart Vaihingen Offices Ingolstadt Dresden Wolfsburg Furstenwalde Berlin On site Offices Sindelfingen Unterturkheim Weissach Ingolstadt DYNA 7 MORE norb c Business model RETRACE UNE 49 IF 53202 50 db A1 am HH3 W5 33 BFPO Technical Software Software development Consultancy work seis Development Non linear analysis Support Research Linear analysis Training Implementation Dynamic analysis Improvement Static analysis Support Optimization DYNAmore Nordic e LS DYNA Vehicle safety LS OPT Material modeling Explosion analysis N Contacts Metal forming Cah dunne Element technology Offshore e Crash barriers Training Energy Oasys Primer GUI deve
6. TACT xxx Contact definition i a The different parameters on different keywords slave 4 might be used depending on contact type The parameter might have a different meaning depending on contact type use Makes contact definition tricky in LS DYNA Some of the most interesting parameters found on master different cards will be examined in this presentation DYNA MORE norb c Important contact parameters penalty method default Motion a penetration Contact force k interface spring stiffness Solid elements Shell elements ckA KA VA diagonal K bulk modulus c penalty factor k The time step of the analysis is determined by LS DYNA from the elements of the FE mesh without considering the contact interfaces DYNA MORE norb c 60 Contact Thickness and Initial Penetrations E d2 Change of shell thickness only for contact treatment h 1 SRN SS Og WSN Ja Initial eee le MORE no 61 Important contact parameters friction Sliding friction FS FD DC and VC Defined in keyword CONTACT Based on Coulomb friction Default values gives no friction u FD FS FD e FS and FD are static respectively dynamic friction coefficient DC decay coefficient lf FD and FS not are equal then FD should be less than FS and DC nonzero VC is the coefficient for viscous friction and limits the friction force typically 3 of yield stress Viscous damping VDC improv
7. aterial PART S Define element types and integration SECTION SHELL S Define material properties MAT ELASTIC MAT FIBER S Define nodes and elements NODE ELEMENT SHELL S Define loads and BC LOAD NODE END Mandatory DYNA 23 MORE NORDIC Keyword Format Input file k Similar functions are grouped together under the same keyword A data block begins with a keyword and ends with the next keyword Keywords are left justified No distinction between lower and upper case letters Variables are right justified in their fields A 0 or blank means that the variable will get the default value The decimal point is always written out for floating point variables 24 Keyword Format Input file k Comments rows are written after a dollar sign in the first position COMMENT keyword exist Do not use tabs when editing or creating your file Line feed signs may cause problems when transferring files from Dos to Unix Keywords Define Geometry Input file k NODE S NID X L 0 00 2 1 0E 2 3 0 02 4 2 00 2 X ELEMENT SHELL i CID PLO nl N2 Bo 0 0 01 0 02 1 Ly io LG 5 L 2 Sy 6 27 5 Local coordinate system Ke from n1 to n2 Ye perpendicular to x directed towards n3 MORE NORDIC y Z 0 08 0 0 l 0E 2 Free format O1 A Fixed format Elements Some element formulations are more costly
8. e defined hierarchically The order between them are LS DYNA defaults Control card input Individual Keyword input Set your defaults with the control cards and change the keyword input where default values not should be used Input of 0 will normally give the default value which is shown in the manual Most Important Control Cards Always consider the following control cards since they can strongly affect your results or output CONTROL_ACCURACY CONTROL_CONTACT CONTROL_ENERGY CONTROL_HOURGLASS CONTROL_SHELL CONTROL_SOLID CONTROL_TERMINATION CONTROL_TIMESTEP Implicit Solution Types Linear Analysis static or dynamic single multi step Eigenvalue Analysis frequencies and mode shapes linear buckling loads and modes modal analysis extraction and superposition Dynamic analysis by modal superposition 971 Nonlinear Analysis Newton Quasi Newton Arclength solution static or dynamic default LS DYNA static and nonlinear DYNA 7 MORE norb c Output Files Binary files can be viewed in LS PrePost DATABASE_BINARY_ Option ASCII files for more detailed output graphs can be shown in LS PrePost DATABASE Option Data in the binary and ASCII files is controlled by DATABASE_EXTENT_Option DATABASE HISTORY Option Control files d3hsp Message files messag Output Files D3PLOT database for complete output states D3DUMP complete database for restart RUNRSF run
9. ementally updated from the strain rate with aid of the constitutive tensor C Ao oAt A DAt Most of the materials in LS DYNA are based on this formulation for the elastic response Merits and drawbacks theoretical It is fairly straightforward to use and easy to implement in a finite element code The response is path dependent the stress for a closed strain cycle can be nonzero it should be used when the elastic deformation is relatively small It is difficult to deal with anisotropic constitutive models because the constitutive tensor C is restricted to be isotropic for nonlinear analysis This is however solved in LS DYNA with a co rotational update Hyperelasticity definition A material is hyperelastic if the internal work is independent of the deformation path It is characterized by the existence of a strain energy function that is a potential for the stress S Second Piola Kirchhoff stress tensor E Green strain tensor C Right Cauchy Green tensor Typically used when elastic deformation is substantial e g rubber Stress and strain uni axial deformation Tensile test Engineering stress 9 F A Engineering strain s L L L In LS DYNA True stress o F A True strain I1n L L o Elastic response Hooks law o Eg Area reduction A A l 2ve see ss DYNA 40 MORE norb c Elasto plasticity in 3 D multi axial deformation _Deviatoric stress VYolume
10. ent units S1 S2 S3 ins RL EE time second second millisecond D me ion tome Dee Newton Newton even 7 85E 09 density of steel 7 85E 03 Keyword User s manual GENERAL CARD FORMAT LS DYN A The following sections specify for each keyword the cards that have to be defined Each E card is defined in its rigid format form and is shown as a number of fields in an 80 character KEYWORD USER S MANUAL string Most cards are 8 fields with a length of 10 and a sample card is shown below Card Format l 2 gt Q 8 August 2006 Version 971 me fa ao LIVERMORE SOFTWARE TECHNOLOGY CORPORATION Remarks EL AIT Rights Reserved The type is the variable type and is either F for floating point or I for an integer The default gives the value set if zero is specified the field is left blank or the card is not defined The remarks refer to comments at the end of the section The card format is given above the card if it is other than eight fields of 10 Free formats may be used with the data separated by commas 3 6 7 EU ENS Copyright 1992 2006 CT te te DYNA 2 MORE NORDIC Input file Keywords Input file k Comment card begins with KEYWORD Mandatory TITLE Test example S Control cards govern entire model simulation CONTROL TERMINATION SCONTROL TIMESTEP S Define output of results DATABASE BINARY D3PLOT DATABASE GLSEAT S Define section and m
11. es stability For metal contacts use 20 and for soft material 40 60 Vel 62 Automatic contacts without self contact CONTACT_AUTOMATIC_NODES_TO_SURFACE CONTACT_AUTOMATIC_SURFACE_TO_SURFACE Thickness taken into account Contact surface is offset by half thickness from mid plane Orientation of segments not needed Contact from both sides Handles disjoint meshes Applies a smooth surface based on a radii at the edges including free edges Initial penetrations are detected Possible to change or scale contact thickness Friction and damping available 63 Single surface contacts self contact CONTACT_AUTOMATIC_SINGLE_SURFACE CONTACT_AUTOMATIC_GENERAL Same features as the automatic contacts Only require definition of the slave surface Include self contact Sensitive to initial penetrations Possible to use only one contact definition forthe complete model Beam and edge to edge contacts are included CONTACT AUTOMATIC GENERAL Edge Beam Contacts CONTACT_AUTOMATIC_GENERAL 26 exclude interior edges entire length of each exterior edge is checked for contact OBS the edge cylinder is not affected by OPTT or TH when using part_contact CONTACT_AUTOMATIC_GENERAL_INTERIOR 126 like CONTACT_AUTOMATIC_GENERAL but interior edges are treated like exterior edges Alternative way to treat edge contact creating null beam elements ELEMENT BEAM MAT NULL approximately 1mm in diameter al
12. ion through the thickness gives a membrane element 2 point integration through the thickness is the default sufficient for a linearly elastic material For plastic bending behaviour at least 3 points are needed throush the thickness 5 points recommended for sheet metal stamping 7 points for springback Use odd numbers to include the neutral axis Element Performance UUOr 8 0109 TH P gt yea sayur Ang TH p3ye 3ayu Aqua Or 9d Lg pesou Aqua eEUOTJEJO AO nrT soysnH nry soysny surly SUOM OHUDSI P IH uBUyJeIAyT oyyosyApog SSOUJJS SUICIBA AUSL OHUWDSI PI AUSL OHUPSJ PH 33 2013 09 09 Keyword and Elements DYNA MORE NORDIC CONTROL_ACCURACY Invariant node numbering particularly important when large shear forces are present in an element 2nd order stress update spinning bodies such as turbine blades rotating tires sometimes for stiffness hourglass control implicit solutions with large strains in each step Material Models Material Models Over 200 models for various applications exists in LS DYNA Determine the stress based on strain strain rate temp etc Not materials but models subject to restrictions Load magnitude Deformation speed strain rate Temperature The models are defined by material parameters E v p etc Hypoelasticity Hypoelasticity relates a strain rate to a corresponding stress rate 6 C D O EE Stress is incr
13. lopment Roadside safety DynaForm HPC Cluster Accident reconstruction e FormingSuite Vibration and NVH e Femzip Thermo mechanical On site DYNA MORE NORDIC DYNAmore Nordic Selected customers BAE SYSTEMS BENTELER V Va BOMBARDIER froi Autoliv EDES ED Westinghouse lt gt e Ve HARDTECH i Benes SSAB cesT TOOLING np en TNO WW A res E gt NTNU DYNAmore Group Selected customers AUTOMOTIVE Autoliv PORSCHE HYUNDAI Drive your way GESTAM HARDTECH A MAGNA STEYR more value more car Contact Software Products Dr Marcus Redhe E mail marcus redhe dynamore se Mobile 46 0 70 55 131 42 Engineering Service and Support Dr Daniel Hilding E mail daniel hilding dynamore se Mobile 46 0 70 65 366 85 Address DYNAmore Nordic Brigadgatan 14 587 58 Link ping Sweden Web http www dynamore se Phone 46 0 13 23 66 80 DYNA MORE norb c Introduction to LS DYNA I LS DYNA One code strategy Combine the multi ohysics capabilities into one scalable code for solving highly nonlinear transient problems to enable the solution of coupled multi physics and multi stage problems Explicit Implicit Incompressible Fluids Heat Transfer Mesh Free CESE Compressible Fluid EFG SPH Airbag Particle Solver User Interface Electromagnetism Elements Materials Loads Acoustics Freque
14. ncy Response Modal Methods Discrete Element Method SBD Simulation Based Design Instead of a physical prototype a virtual model is created The purpose of the model is to resemble the behaviour of the physical product All development testing is made in the virtual product Thus you treat the model as you would if it was a physical product The benefits are several Shorter time to market Reduce number of costly prototypes Increased innovation Lower development costs Higher quality but also the challenges Rethink development process Trust the results Educate personnel new partners DYNA MORE norpic Volvo XC60 DYNA 15 MORE NORDIC What do you need PRE PROCESSOR dant Generates the FE model Geometry Applies boundary conditions etc Material nen Process 4 cts S PrePost SOLVER Solves the numerical model POST PROCESSOR View the results Cae SIC Do 242 es lt Dependence on analysis om Simulation process Build FE model FLE Element LS PrePost ANSA Modify Process Initial powder volume Geometry LS PrePost Evaluate results LS PrePost Pre simulation Initial stress stress Bolts etc LS PrePost Eu a Test 2013 09 09 18 Introduction to LS DYNA I Keywords and Elements Keywords Define Geometry Input file k Newton s second law F ma requires consist
15. ning restart file overwritten D3PART as D3PLOT but includes just specified parts D3THDT database for time history data of element subsets D3DRLF dynamic relaxation database D3MEAN CFD database INTFOR database for output of contact interface data XTFILE extra time history data D3EIGV modal data from eigenvalue analysis D3CRCK crack data from Winfrith concrete model ASCII Output Files GLSTAT global data MATSUM material energies RCFORC resultant interface forces SLEOUT sliding interface energy NODOUT nodal point data ELOUT element data SECFORC cross section forces RWFORC rigid wall forces SSSTAT Subsystem data DEFORC discrete elements NCFORC nodal interface forces DEFGEO deformed geometry SPCFORC SPC reaction forces NODFOR nodal force groups DYNA MORE norb c ABSTAT airbag statistics BNDOUT boundary condition force energy RBDOUT rigid body data GCEOUT geometric contact entities JNTFORC joint force SBTOUT seat belt output AVSFLT AVS database SWFORC nodal constraint reaction forces MOVIE MPGS TRHIST trace particle history TPRINT thermal output SPHOUT SPH data MORE NORDIC Test 2013 09 09 Demonstrate LS PrePost PreProcessing PostProcessing Thank you Test 2013 09 09 71
16. ong every edge wished to be considered for edge to edge contact and including these null beams in a separate AUTOMATIC GENERAL contact CONTACT_SINGLE_EDGE 22 Treats only edge to edge contact no thickness offset at the contact edge CONTACT_xxx_MORTAR edge to edge contact no thickness offset at the contact edge DYNA J MORE norb c Tied contacts CONTACT_TIED_NODES_TO_SURFACE CONTACT_TIED_SURFACE_TO_SURFACE CONTACT_TIED_SHELL_EDGE_TO_SURFACE wee OFFSET Possibility to tie nodes to a surface segment NODES_ and SURFACE_ ties translational d o f SHELL_EDGE_ ties translational and rotational d o f Constraint based Thus will not work with rigid bodies OFFSET allows for a segment thickness and is penalty based _TIEBREAK_ has failure options Can be used to model glue spotwelds etc 66 Control Cards amp Execution Control Cards The purpose is Activate solution options implicit solution adaptive remeshing mass scaling Change default values on options and parameters Remember that Ordering between them and position are arbitrary Good practise is to put them first in your input file Do not use more then one control card of each type All control cards are optional except CONTROL_TERMINATION Os CO Control Card Default Values Default values exist for all options and most parameters Control cards change default values globally Default values ar
17. than others Stresses and strains are calculated at the integration points Accelerations velocities and displacements are evaluated at the nodes DYNA n Under Integrated and Fully Integrated Elements Most element formulations in LS DYNA are under integrated i e the stresses and strains are only calculated in the mid point of each element Advantage Computational efficiency The material model is called once per integration point and time step Disadvantage The element formulation contains zero energy modes hourglass modes Integration O point s Under Integrated and Fully Integrated Elements The following element deformation does not yield any strains in the integration point and thus no stress There is deformation but no associated internal energy hence the name zero energy modes These modes have to be suppressed using hourglass control No strain Hourglass Control Zero energy modes Hourglass modes Hourglass controlled by CONTROL_HOURGLASS and HOURGLASS Hourglass modes for 1 point integration Q4 shell Hourglass modes for 1 point integration solid elements fl ro UM SECTION_SHELL Element formulation Belytschko Isay Belytschko Wong Chiang Hughes Liu Belytschko Leviathan Fully integrated shells Higher order shells 6 8 noded tria quad Element thickness Number of integration points through shell thickness 31 Elements shell NIP 1 point integrat
18. tric stress Stress decomposition OO 3 Von Mises yield criterion f 5 8 O E Plastic strain O e FT OS ee AC Perfect plasticity Isotropic hardening Kinematic hardening ioy NIA Material Models 2013 09 09 41 MI O RE norpic Elastic visco plastic material MAT_PIECEWISE_LINEAR_PLASTIC MD RO E PR SIGY ETAN FAIL TDEL C P LCSS LCSR VP EPS1 EPS2 EP1 ES2 For Metals loading exceeding yielding stress rate effects In All element types Theory Isotropic plasticity model with visco plasticity option E Young s Modulus Gr Strain rate parameters RO Density LCSS Load curve for o e PR Poisson s Ratio LCSR Load curve for strain rate scaling SIGY Yield stress VP Visco plastic flag ETAN Tangent modulus EPS1 Piecewise linear def lw INI AR Material Models 2013 09 09 42 WV O RE norDbic Elastic visco plastic material Activati ng visco plasticity O static yield stress C P 0 No visco plastic effects El p C P 0 VP 1 gt Yield stress is given by 0 0 a VP 1 Is recommended as It uses a consistent visco plastic theory Dow NA Material Models 2013 09 09 43 WV O RE norDic Elastic plastic material with Bauschinger efftect MAT_PLASTIC_KINEMATIC MID RO E PR SIGY ETAN BETA SRC SRP FS VP For Metals under large loading In All element types Theory Isotropic and kinematic hardening plasticity viscoplastic
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