th 4 European LS-DYNA Users Conference Plenary Session I Current and future developments of LS-DYNA I Dr. Hallquist J. O., Livermore Software Technology Corp. 4th LS-DYNA User’s Meeting European LS-DYNA Conference Outline of talk LSTC’s Perspective on the future Version 970 status Recent developments for crash Arbitrary Lagrangian-Eulerian Developments Implicit Developments EFG (Mesh-free) Developments MPP Outlook A – I - 01 th Plenary Session I 4 European LS-DYNA Users Conference Perspective on the future LSTC’s major goal is to develop within one explicit finite element program capabilities to seamlessly solve problems that require: Multi-physics Multiple stages Multiple formulations Multi-processing Multi-physics Multi-physics problems require solution methods from more than one discipline. Fluid-Structure interaction A – I - 02 tire hydroplaning airbag deployment Thermo-mechanical problems (hot forging). Bird strike on engine and its effect on the overall structural dynamics of the aircraft (impact + linear response) th 4 European LS-DYNA Users Conference Plenary Session I Multiple stages Multi-stage problems require sequential simulations. Manufacturing-stamping. 1. 2. 3. Manufacturing simulation imported into performance simulation. 1. Binderwrap (implicit dynamics) Sheet metal stamping (explicit with mass scaling) Spring back (dies removed-implicit static). Crash simulation accounts for effects of manufacturing processing Static initialization of dynamic simulation. Multiple formulations No single solution method is suitable for all applications. Solid mechanics: Degree of deformation: Nonlinear elements for large deformations. Linear elements for eigenvalues, superelements, and linear structural analyses. Dynamics: Explicit methods for short duration transient problems. Implicit methods for static and long duration problems. Instantaneously switch between methods A – I - 03 th Plenary Session I 4 European LS-DYNA Users Conference Multi-processing Massively Parallel Processing (MPP) is here to stay. MPP is moving downscale: Desktop MPP under Unix, Windows, and Linux environments Heterogeneous processing. Large MPP machines have many parallel jobs running simultaneously on subsets of processors. Processing across high speed networks. 12-32 are preferred for LS-DYNA Stamping analysis with adaptivity is ideally suited to MPP machines due to the simplicity of contact. Version 970 status Now used at many customer sites. Advantages over version 960: 970 will become the production code at many customer sites after the updated user’s manual is published A – I - 04 The implicit capabilities are greatly expanded The ALE airbag deployment for out-of-position occupants is nearing production level The MPP version is more scalable and, therefore, faster An updated theory manual is ready for release. th 4 European LS-DYNA Users Conference Plenary Session I Recent crash developments Spotwelds Segment based contact Mesh coarsening Binary options for database Model documentation in database Element technology Constitutive models Rigid body related developments MADYMO coupling Tied contact with offsets Slave Node The offset distance is fixed. Implemented with both constraints and penalties. Two algorithms are needed Offset Closest Point on Surface Isoparametric Coordinates s,t Structural element formulation, includes rotational degrees-offreedom Continuum element formulation, no rotational degrees-of-freedom MPP support Implicit implementation for constraint method in version 970 A – I - 05 th Plenary Session I 4 European LS-DYNA Users Conference Tied contact with offsets Available for contact types: TIED_NODES_TO_SURFACE_{OPTION} TIED_SHELL_EDGE_TO_SURFACE_{OPTION} TIED_SURFACE_TO_SURFACE_{OPTION} Options: OFFSET Normal and tangential springs, old method which may not be orthogonal to rigid body motion BEAM_OFFSET Beam like penalty functions Orthogonal to rigid body rotations Can be numerically sensitive CONSTRAINED_OFFSET Exact method based on rigid body kinematics Tied contact with offsets Structural formulation Slave Node s Fm = Fs Fi m = F m N i ( s, t ) + Fi m M m = r × Fm M im = M m N i ( s, t ) + M im V m = ∑Vi m N i ( s, t ) Offset r Master Node i Closest Point on Surface, m, Isoparametric Coordinates s,t A – I - 06 ω m = ∑ ωim N i ( s, t ) Am = ∑ Aim N i ( s, t ) ω& m = ∑ ω& im N i ( s, t ) V s =V m +ωm × r As = Am + ω& m × r + ω m × (ω m × r ) th 4 European LS-DYNA Users Conference Plenary Session I Tied contact with offsets P = M T ω = F TV Solid formulation Slave Node s Virtual Work ω × r = Rω z − y 0 R = − z 0 x y − x 0 Least Squares Relation Between w and V r ( R ω − δVi m ) ⋅ ( Riω − δVi m ) 2∑ i m m m Master Node i δVi = Vi − V Offset Closest Point on Surface, m, Isoparametric Coordinates s,t J=1 T ω = ∑ Ri Ri i −1 ∑R T j δV jm j Exact for Rigid Body Motion Tied contact with offsets Solid formulation Fi m = F s N i ( s, t ) ω = ∑ RiT Ri ∑ R jδV jm i j M = r×F ~ Fi m = Ri [∑ R Tj R j ]−T M m ω& = ∑ RiT Ri ∑ R jδAmj i j m m δAj = A j − Am − ω × (ω × rj ) Forces on Master Segment V s =Vm +ω ×r m s j ~ Fi m equivalent forces due to slave force offset As = Am + ω& × r + ω × (ω × r ) Update of Slave Node Exact for Rigid Body Motion A – I - 07 Plenary Session I th 4 European LS-DYNA Users Conference Frictional beam contact A – I - 08 Recently improvements have been made in beam-tobeam contact Post contact searching to reduce the number of required global searches Soft constraint option is added to improve reliability Interface friction between beams Implicit implementation th 4 European LS-DYNA Users Conference Plenary Session I Spotweld modeling Connection of shell surfaces Spotweld models in LS-DYNA Nodal rigid bodies Deformable beams Continuum elements ? ? Spotweld modeling (bricks) Advantages Contact nodes on both surfaces Axial, bending, and torsional stiffness Size is independent of surface mesh Real width of spotweld is modeled Disadvantages Mass scaling is needed Orientation required for resultant based failure A – I - 09 th Plenary Session I 4 European LS-DYNA Users Conference Spotweld modeling (4-bricks) Compared to 1 brick Mass scaling is similar and overall problem cost increase is insignificant. Interface forces are realistically distributed Spotweld modeling (mat_100) To avoid time step size problems, the desired time step size is defined for *MAT_SPOTWELD: LS-DYNA prints out the added mass for ∆t. Failure can be based on plastic strain, strain resultants, or a combination of plastic strain and resultants: N rr N rrF 2 N rt + N rt F 2 M ss + M ssF 2 M tt + M ttF 2 2 Trr + −1 = 0 T rrF The resultants are computed from the nodal point forces. A – I - 10 2 N rs + N rsF Currently limited to one brick per spot weld th 4 European LS-DYNA Users Conference Plenary Session I New spotweld failure criterion The stress based failure model for beam and solid spot welds, developed at Toyota Motor Corporation, is based on the peak axial and transverse shear stresses, fails the entire weld if the stresses are outside of the failure surface defined by 2 σ rr τ F + F −1 = 0 σ rr τ 2 The peak stresses are calculated from the resultants using simple beam theory. σ rr = A N rr + A = π M rs2 + M rt2 Z 2 τ= d 4 M rr + 2Z Z N rs2 + N rt2 A 3 = π d 3 2 New spotweld failure criterion Three additional failure calculations have been implemented for beam spot welds Notch stress Stress intensity factor Structural stress A – I - 11 th Plenary Session I 4 European LS-DYNA Users Conference MPP segment based contact The name, “Segment Based Contact” is motivated by the most fundamental difference between segment-based contact and the standard LS-DYNA penalty contact: Standard Contact* * The name, “Segment Based Contact” detects penetration of nodes into segments and applies penalty forces to the penetrating node and the segment nodes. is motivated by the most fundamental difference between segment-based contact and the standard LSDYNA penalty contact: ________________________ *standard contact refers collectively to these 9 contact types: 3, a3, 10, a10, 4, 13, a13, 14, and 15 with soft=0 or soft=1. Segment-based vs. standard Segments hit even if nodes miss • Because penetration of segments by segments is checked rather than penetration of segments by nodes. A – I - 12 th 4 European LS-DYNA Users Conference Plenary Session I Segment-based vs. standard Sharp corners are easily handled Because contact is detected between segments, individual nodes cannot go undetected and slip into spaces between segments at corners Falling blocks-segment based One brick element defines each block. Nodes do not make contact with contact segments. A – I - 13 Plenary Session I th 4 European LS-DYNA Users Conference Mesh coarsening for crash The current coarsening capability in LSDYNA for metalforming has now been extended to provide seamless mesh coarsening for crash applications Process Outline Define elements to be coarsened (default=ALL) Perform Internal Coarsening Respect existing constraints Establish new adaptive constraints Initialize new mesh Perform calculations Applications for coarsening A – I - 14 Process Allows Seamless Transition From OneDetailed Model to Various Impact Scenarios Saving Multi-Model Maintenance and CPU Costs Front Impact Rear Impact Side Impact Head-Impact Pedestrian Impact th 4 European LS-DYNA Users Conference Plenary Session I Binary option for ascii files What it is not A file format Proprietary What it is I/O library developed by LSTC Portable Robust Flexible Source code is available on ftp site Binary option for ascii files Flexibility Acts like a file system Directories Variables, Name, Type, Length New data won’t break old applications Easy to use Efficiency and portability Binary files Library handles size/format conversions A – I - 15 Plenary Session I th 4 European LS-DYNA Users Conference Binary option for ascii files “ASCII” output files All can be output in this format today. Serial and MPP codes ASCII (Default on SMP and serial machines) Binary (Default on MPP machines) Both ASCII and Binary possible LS-POST is able to read and post-process the binary database Model documentation ID’s with descriptor information are now available for: A – I - 16 Airbags Contact Cross-section definitions Joints Parts Rigid Walls Nodes Elements SPC’s Displacement boundary conditions th 4 European LS-DYNA Users Conference Plenary Session I Model documentation To keep upwards compatibility, _ID causes ID and heading information to be read. This additional information is written into the ASCII files, and their binary counterpart, to help in post-processing Model documentation The ASCII files which now include model documentation information are: NODOUT, nodal information ELOUT, element information JNTFORC, joint forces MATSUM, part statistics SECFORC, section forces RCFORC, contact reaction forces ABSTAT, airbag statistics file RWFORC, rigid wall force file SPCFORC, single point constraint reaction forces BNDOUT, reaction forces due to applied displacements A – I - 17 th Plenary Session I 4 European LS-DYNA Users Conference Abnormal termination-shells An abnormal termination will occur if a zero or negative Jacobian develops in a shell element. More severe in fully integrated elements Such terminations can be hard to debug to make appropriate model changes. Special checking is now available to identify “bad” elements and either, cleanly terminate, or delete the element and continue running. Two flags control the checking, one for 1 point elements and the other for fully integrated elements Thermal shell A single input flag activates the thermal shell. 8 fictitious nodes are created automatically to represent the upper and lower shell surfaces. A quadratic temperature variation is obtained through the shell thickness. A stiffness matrix is created for implicit solution method used in LS-DYNA for heat transfer A – I - 18 Element stiffness is based on 12-node brick element. The conjugate gradient solution method is used for speed. Thermal contact possible through projected surfaces th 4 European LS-DYNA Users Conference Plenary Session I Beam element enhancements Offsets of the beam nodes to enable a beam to be used as a shell stiffener 1. Orientation vectors to position beam 1. Added as an option for all beam formulations in version 970 for both implicit and explicit applications Added as an option for all beam formulations that use the third orientation node Cross sectional warping Implicit applications only-being added Introduces 1 additional degree-of-freedom per node so scalar nodes are being added to handle the additional DOF. Implicit hexahedron element 48 degree-of-freedom hexahedron element. Accurate linear element A – I - 19 Plenary Session I th 4 European LS-DYNA Users Conference Implicit tetrahedron element 24 degree-of-freedom tetrahedron element is no available for implicit 24-dof tetrahedron A comparison of the 12 and 24 degree-offreedom tetrahedron elements is shown. A – I - 20 th 4 European LS-DYNA Users Conference Plenary Session I 10-node tetrahedron element Implemented for MPP and SMP Same cost per element cycle as SRI solid element. ∆t is small due to high frequencies Contact treated automatically by 4 triangles for each face Available for both implicit and explicit calculations 4 or 5 integration points, constant pressure Element_direct_matrix_input Option for reading and using superelements in explicit computations is now extended to implicit applications Required input is a file in Real*8 NASTRAN format containing: Mass Matrix (must be positive definite) Stiffness Matrix Damping Matrix (optional) The matrices share degrees of freedom with model boundaries and also introduce additional degrees of freedom with nodes and generalized coordinates. A – I - 21 th Plenary Session I 4 European LS-DYNA Users Conference Material definitions Materials in version 970 can be defined by a “long” name or a short name, i.e., *MAT_TRANSVERSLY_ANISOTROPIC_CRUSHABLE _FOAM or simply, *MAT_142 Applies to all material models. Orthotropic viscoplastic Available for material models: Viscoplasticity is optional *MAT_SIMPLIFIED_JOHNSON_COOK *MAT_PLASTICITY_WITH_DAMAGE 40% more costly due to iterative algorithm Damage evolves monotonically in principle strain directions in tension only. Orthotropic behavior after failure. A – I - 22 Better correlation with experimental data Consistent results with minor input changes th 4 European LS-DYNA Users Conference Plenary Session I Transversely_anisotropic_ crushable_foam For modeling low density extruded foam with anisotropic behavior, typically with high strength in the extruded direction Used in energy absorbing structures to enhance automotive safety in low and medium velocity impacts Zero Poisson’s ratio under longitudinal loads A smooth anisotropic yield surface produces physically correct behavior, i.e. weaker in off-axis loading Variable coefficients are used which depend on volumetric strain Accurate off-axis loading provides better results than MAT_HONEYCOMB Modified_crushable_foam Rate effects are available in the extension to the isotropic crushable foam model. (*MAT_163) σ 1-V A – I - 23 th Plenary Session I 4 European LS-DYNA Users Conference Quasilinear_viscoelastic A new model for biological tissues. ε&1 < ε&2 < ε&3 . NT G (t ) = ∑ Gi exp( − β i t ) i =1 6 σ (ε ) (ε ) = ∑σ iε i i =1 Up to 12 terms may be include in the Prony series Built in lease squares fit optional Implemented for solid elements-explicit only. Hill_foam A new hyperelastic compressible foam model, which captures Poisson’s ratio effects. The Cauchy stresses are defined in terms of J and the principal stretches as: 1 ti = J m ∑ j =1 C j (λ i b − J j −nb j ) where i=1,2,3 A least squares fit is available for Cj and bj if uniaxial or biaxial tension and compression test data is available. A – I - 24 th 4 European LS-DYNA Users Conference Plenary Session I Viscoelastic_hill_foam Rate effects are taken into account through linear viscoelasticity by a convolution integral of the form: t σ ij = ∫0 gijkl (t − τ ) ∂ε kl dτ ∂τ The viscoelastic stresses are added to the stress tensor determined from the strain energy functional. A least squares fit is available to determine the viscoelastic constants Low_density_synthetic_foam For modeling rate independent low density foams, which have the property that the hysteresis in the loading-unloading curve is considerably reduced after the first loading cycle. After the first loading cycle the loading-unloading curve is identical If orthotropic behavior develops after the first loading cycle where the material behavior in the orthogonal directions are unaffected then the _ORTHO option should be used Loading Curve f or f irst cycle σ Loading curve f or second and subsequent cycles strain A – I - 25 th Plenary Session I 4 European LS-DYNA Users Conference Simplified_rubber Uses uniaxial data given by a load curve which is defined for the entire range of expected behavior Table may be used to include strain rate effects Force versus change in gauge length, i.e., nominal stress versus engineering strain can be used Models hysterisis Engineering strain rates are optional No fitting of material parameters means that nearly all rubber like behavior can be approximately simulated 1dof_generalized_spring x’ Node 1 DOF 1 z’ Local y’Coordinate System 1 Node 2 z’ DOF 2 x’ y’ Local Coordinate System 2 A – I - 26 Couples arbitrary degrees of freedom between nodes with springs and dampers. a12 F1 = −K F2 − a1a2 . a12 − a1a2 q1 − C 2 a2 q2 − a1a2 − a1a2 q&1 a22 q&2 •Fi = Generalized force for node i. •qi = Displacement for node i. •qi = Velocity for node i. •ai = Scale factor for node i. •K = Stiffness. •C = Damping. Available in both explicit and implicit. th 4 European LS-DYNA Users Conference Plenary Session I Nodal rigid bodies Two new features are implemented for *CONSTRAINED_NODAL_RIGID_BODY Release flags for nodal degrees-of-freedom that allow the translation of the RBE2 constraints in NASTRAN into the nodal rigid body option Either local or global system Can simulate joints between deformable bodies Implicit implementation allows the chaining of rigid bodies Center of mass constraint with _SPC option Either local or global system Constrained_interpolation The motion of a single independent node is interpolated from the motion of a set in independent nodes. Can now be applied in either a local or a global coordinate system. Implicit and explicit implementations Some applications Tie beam or shell elements to solid elements. Distribute mass and inertia from the dependent node to the surrounding independent nodes Distribute forces and moments from dependent node to independent nodes A – I - 27 th Plenary Session I 4 European LS-DYNA Users Conference Joint failure OBJECTIVE: Model mechanical failures in joints without the cost of a finite element model of the joints. Requested by Federal Highway Administration Failure criteria are based on forces and moments. Failure criteria when force and moment failure are uncoupled: 2 max( N xx ,0) N yy + N N xxF yy F 2 N zz + N zzF 2 −1 = 0 M xx M xx F 2 M yy + M yy F 2 M zz + M zz F 2 −1 = 0 Failure criteria when force and moment failure are coupled. 2 2 2 2 2 2 max( N xx ,0) N yy N zz M xx M yy M zz −1 = 0 + + + + + N xx F N yy F N zzF M xx F M yy F M zzF If the value of a failure constant is zero, the corresponding force or moment isn’t considering in the failure criteria. Failure constants can be specified in either a local or the global coordinate system. *…_Joint_stiffness_translational Translational stiffness has been added to joints for joint types Cylindrical Joint Translational joint Planar joint Force yield force curve elastic perfectly plastic behavior elastic stiffness negative stop displacement A – I - 28 Displacement positive stop displacement th 4 European LS-DYNA Users Conference Plenary Session I Madymo coupling Extended coupling allows users to link most MADYMO geometric entities with LS-DYNA FEM simulations. FEM element/nodes. FACET surfaces. Ellipsoids/Planes. This gives LS-DYNA Users access to the most advanced MADYMO Dummy & Human models. The MADYMO contact algorithm will be used to calculate loading between the two models. User can access elastic loading with hysteresis/damping/friction. MADYMO FEM Element Groups will be assigned to an LSDYNA Material, allowing these entities to be defined in contacts with other LS-DYNA materials. Extended MADYMO coupling Extended coupling allows users to link most MADYMO geometric entities with LS-DYNA FEM simulations. FEM element/nodes. FACET surfaces. Ellipsoids/Planes. This gives LS-DYNA Users access to the most advanced MADYMO Dummy & Human models. The MADYMO contact algorithm will be used to calculate loading between the two models. User can access elastic loading with hysteresis/damping/friction. MADYMO FEM Element Groups will be assigned to an LSDYNA Material, allowing these entities to be defined in contacts with other LS-DYNA materials. A – I - 29 th Plenary Session I 4 European LS-DYNA Users Conference Example: us-sid & es2 in lincap Vehicle/barrier/seat are LS-DYNA models. FEM Dummies are MADYMO models. Side Inner Panel + Side Trim Panels are the coupled entities. MADYMO LS-DYNA Vehicle Model Courtesy NHTSA. Lincap with fem es2 •Beta release of v6.0/v970 available at the end of May, 2002. A – I - 30 th 4 European LS-DYNA Users Conference Plenary Session I Seatbelt pretensioner option Force versus time can now be defined: Fo r c e Re t ract or Out Force Pull- Defined Force Vs. Time Curve Ret ract or Lock Time T ime Nastran interface A NASTRAN reader, developed for Superwhams by KBS2 Inc., is now embedded in LS-DYNA version 970 to allow NASTRAN input decks to run directly in LSDYNA without translation. Advantages: Many production problems setup in NASTRAN format exist for normal modes, statics, and buckling that can be used for verification of linear capabilities and constraint equations Nastran input can be augmented by LS-DYNA input to allow one model for NVH and crash. First line in the input file: *NASTRAN or, alternatively, *INCLUDE_ NASTRAN followed by the file name Allows change of element formulations Mix LS-DYNA input with NASTRAN input. A – I - 31 th Plenary Session I 4 European LS-DYNA Users Conference Normal trimming Normal (or 3D) trimming has been implemented, the new features include No vector is required Trimming curves are projected to the element based on its normal Trimming curve could include several segments Both digitized and IGES data are supported Availability: It is available in LS970 The Keyword is *DEFINE_CURVE_TRIM_3D Normal trimming A – I - 32 th 4 European LS-DYNA Users Conference Plenary Session I Normal trimming This method allow distorted Trimming curve Cam trimming One more feature available for cam trimming: Trimming curve can be defined in global coordinate In *DEFINE_CURVE_TRIM, one more parameter is added The seventh parameter, iglobal=1, will activate this feature A – I - 33 th Plenary Session I 4 European LS-DYNA Users Conference Trimming improvements Trimming causes Poor aspect ratios Large internal angles Element size is too small Side effect Poor convergence for the implicit springback prediction Poor mesh for next forming stage Element quality check After trimming, elements are checked for Size Distortion Aspect ratio Internal angles Adaptivity patterns After checking any deficiencies are removed Original result A – I - 34 New trimming Element Checking/Fixing th 4 European LS-DYNA Users Conference Plenary Session I Symmetry plane with SPH Define one or more symmetry plane. First symmetry plane Ghost particles are automatically created to ensure local stability near the boundary. Set of Ghost Particles created by plane # 1 Set of Ghost Particles for plane # 2 Second symmetry plane Symmetry Plane with SPH A – I - 35 th Plenary Session I 4 European LS-DYNA Users Conference New ALE developments MPP Improved fluid-structure interaction Fluid-structure interaction output Point sources for gases *EOS_IDEAL_GAS and *MAT_GAS_MIXTURE *MAT_VACUUM for MMALE simulations New mesh smoothing algorithm for high explosive simulations *INITIAL_VOLUME_FRACTION_GEOMETRY, volume fraction distribution for simple and complex geometries. Mpp ALE capability Design of airbags for out-of-position occupants has created huge interest in ALE capabilities in automotive design A – I - 36 Control volume approach for airbag inflation predicts bag pressures that are unrealistically high and cannot be used for design purposes 1 processor requires 2 weeks per calculation. 32 processors < 12 hours Much effort is being spent in ALE development for airbag deployment th 4 European LS-DYNA Users Conference New development in version 970 Plenary Session I FSI Fluid structure interaction Keyword: *CONSTRAINED_LAGRANGE_IN_SOLID Leakage control Viscous damping Alternative penalty stiffness definition for better numerical stability Automatic time step adjustment at high penalty stiffness ALE structural coupling Prescribed motion of nodes following user defined load curves, and rigid body translation of mesh following mass flow A – I - 37 th Plenary Session I 4 European LS-DYNA Users Conference Benchmark tests Bouncing ball Evaluation: check the path and the shape of the ball Radius 10 cm Bulk modulus 10 GPa Density 2000 kg/m3 40m/s 1m Bouncing ball Second order accurate advection with interface reconstruction preserves shape of rubber ball. A – I - 38 th 4 European LS-DYNA Users Conference Plenary Session I Flat airbag deployed with ALE Shells – 2752 ALE Solids - 43200 Speed-up 1 8000 7000 Elapsed Time (seconds) 1.95 6000 5000 3.89 4000 3000 2000 1000 0 1 2 4 # of Processors A – I - 39 th Plenary Session I 4 European LS-DYNA Users Conference New development in version 970 FSI output Keyword: *DATABASE_FSI pressure x-force y-force porous leakage mass flux through surface z-force Fluid-structure interaction output Number of surfaces: 2 id p fx fy fz pleak mflux 1 2 time= 0.00000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 1 2 time= 0.10200E-03 0.1632E+05 0.4091E+01 0.1947E+05 -0.4878E+01 -0.3215E+01 -0.4174E+01 0.2546E+01 0.2548E+01 0.0000E+00 0.0000E+00 -0.1284E-04 -0.7193E-05 New development in version 97 New EOS for gases New EOS for gases Keyword: *EOS_IDEAL_GAS p = ρ (γ − 1)CV T γ = C P / CV CV = CV 0 + C LT + C LT 2 C P = C P 0 + C LT + C LT 2 A – I - 40 th 4 European LS-DYNA Users Conference Plenary Session I New development in version 970 New gas mixture model Keyword: *MAT_GAS_MIXTURE The model is designed for the treatment of hybrid inflators in coupled ALE-airbag models. *MAT_GAS_MIXTURE handles the mixing of up to eight different ideal gases. Special action is taken to conserve the total energy in the Eulerian advection step. Dissipated kinetic energy is automatically transformed into heat. up to eight different gases p = N ∑ i =1 ρ i (C Pi − C Vi ) T density and heat capacities of the different gas species New development in version 970 Point sources Keyword: *SECTION_POINT_SOURCE_MIXTURE The command is used to model hybrid inflators for coupled ALE-airbag simulations. dynamic inlet temperature section ID inlet gas flow velocity *SECTION_POINT_SOURCE_MIXTURE SID LCT . LCV NIDL1 LCM1 LCM2 LCM3 LCM4 LCM5 NID1 VID1 AREA1 NID2 VID2 AREA2 n point sources . NIDn VIDn AREAn NIDL2 LCM6 NIDL3 LCM7 LCM8 mass flow rates of the different gas species point source inlet areas vectors defining the initial flow direction nodes defining the initial location of the point sources A – I - 41 Plenary Session I th 4 European LS-DYNA Users Conference Point sources-airbag inflators Benchmark tests Pipe A viscous fluid flowing through a pipe point source shell structure Eulerian mesh evaluation: check leakage in the fluid-structure interaction and compare to an analytical pressure distribution A – I - 42 th 4 European LS-DYNA Users Conference Plenary Session I Benchmark tests Pipe A viscous fluid flowing through a pipe Benchmark tests Pipe Pressure distribution along the pipe analytical LS-DYNA x x=0.0 x=0.8 A – I - 43 th Plenary Session I 4 European LS-DYNA Users Conference New development in version 970 Airbag model We have tested a small airbag, deployed with a hybrid inflator, in both a uniform pressure model and in a fully coupled Eulerian model. The inflator and the gas mixture are modeled with *SECTION_POINT_SOURCE_ MIXTURE and with *MAT_GAS_MIXTURE. New development in version 970 Airbag model Airbag inside fluid mesh A – I - 44 th 4 European LS-DYNA Users Conference Plenary Session I New development in version 970 Airbag model Gases inside bag New development in version 970 Airbag model Deployment pattern, UP versus Euler Uniform pressure Euler A – I - 45 th Plenary Session I 4 European LS-DYNA Users Conference New development in version 970 Airbag model Pressure (bar) Gas pressure inside airbag Euler Control volume Time (ms) ALE smoothing for shock fronts A – I - 46 th 4 European LS-DYNA Users Conference Plenary Session I Boeing 757 pentagon impact Courtesy of Purdue University, Department of Civil Engineering, Prof. M. Sozen. Calculations and modeling: Dr. Sami Kilic A – I - 47 Plenary Session I th 4 European LS-DYNA Users Conference Initialization of volume fraction *INITIAL_VOLUME_FRACTION_GEOMETRY Initializing the inside of the tank with fluid A – I - 48 th 4 European LS-DYNA Users Conference Plenary Session I Initialization of volume fraction *INITIAL_VOLUME_FRACTION_GEOMETRY Initializing the inside of the tank with fluid Initialization of volume fraction Sloshing tank, volume fraction of fluid inside deformable tank A – I - 49 th Plenary Session I 4 European LS-DYNA Users Conference Initialization of volume fraction Sloshing tank, stresses in deformable tank Combined implicit-explicit Adding an implicit solution option to an explicit code can utilize the extremely efficient data structures, element formulations, and contact algorithms developed for explicit analysis. Use latest linear direct equation solvers Results in improved explicit algorithms A – I - 50 Sparse matrix solver CG iterative solvers second order accurate formulations required for accurate implicit calculations are automatically available for explicit applications.

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