Oasys LS-DYNA Environment 8.1 VOLUME 3 ... - Oasys Software

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Oasys LS-DYNA Environment: User Guide (Version 8.1) *BOUNDARY This section applies to various methods of specifying either fixed or prescribed motion boundary conditions. Restraints can be set up as a *BOUNDARY_SPC_NODE section, however, a *DEFINE_COORDINATE_SYSTEM is required to define the global coordinate system. For compatibility with older versions of LS-DYNA, it is still possible to specify some nodal boundary conditions in the *NODE card section. *CONSTRAINED This applies constraints within the structure between structural parts. For example, nodal rigid bodies (*CONSTRAINED_NODAL_RIGID_BODY_OPTION), rivets (*CONSTRAINED_RIVET), spotwelds (*CONSTRAINED_SPOTWELD), linear constraints (*CONSTRAINED_RIGID_BODIES), adding extra nodes to rigid bodies (*CONSTRAINED_EXTRA_NODES_OPTION) and defining rigid body joints (*CONSTRAINED_JOINT_OPTION) are all options in this section. This section applies constraints within the structure between structural parts. For example, nodal rigid bodies, rivets, spotwelds, linear constraints, tying a shell edge to a shell edge with failure, merging rigid bodies, adding extra nodes to rigid bodies and defining rigid body joints are all options in this section. *CONTACT This section is divided into three main sections. The *CONTACT section allows the users to define a total of 24 different contact types. These contact options are primarily for treating contact of deformable to deformable bodies, single surface contact in deformable bodies, deformable body to rigid body contact, and tying deformable structures with an option to release the tie based on plastic strain. The surface definition for contact is made up of segments on the shell or solid element surfaces. The *CONTACT_ENTITY section treats contact between a rigid surface, usually defined as an analytical surface, and a deformable structure. Applications of this type of contact exist in the metal forming area where the punch and die surface geometries can be input as VDA surfaces which are treated as rigid. Another application is treating contact between rigid body occupant hyper-ellipsoids and deformable structures such as airbags and instrument panels. This option is particularly valuable in coupling with the rigid body occupant modelling codes MADYMO and CAL3D. Each contact definition must start with a *CONTACT_ card. The *CONTACT_1D is for modelling rebars in concrete structure. *CONTROL Options available in the *CONTROL section wither reset default global parameters, such as hourglass type, contact penalty scale factor, shell element formulation; or set parameters such as termination time. Page 4.4
Oasys LS-DYNA Environment: User Guide (Version 8.1) *DAMPING Defines damping either globally or by part identifier. *DATABASE This keyword with a combination of options can be used for controlling the ASCII and binary files output by LS-DYNA. This keyword defines the frequencies at which results are written to the various databases. *DEFINE This sections allows the user to define curves for loadings, constitutive behaviours, etc; boxes to limit the geometric extent of certain inputs; local coordinate systems; vectors; and orientation vectors specific to spring and throughout the input. For example, a coordinate system ID may be referenced on a *BOUNDARY_SPC_NODE card for a restraint, and load curves are used on the *AIRBAG cards. *DEFORMABLE_TO_RIGID This section allows the user to switch materials that are defined as deformable to rigid at the start of the analysis. This capability provides a cost efficient method for simulating events such as roll over events. While the vehicle is rotating the computation cost can be reduced significantly by switching deformable materials that are not expected to deform to rigid materials. Just before the vehicle comes in contact with ground, the analysis can be stopped and restarted with the materials switched back to deformable. *ELEMENT Solid, shell, thick shell, beam bar(truss), spring, lumped mass and seat belt elements can be set up in the input file. The elements used by LS-DYNA are all linear elements (i.e they have no mid-side nodes). As noted above elements belong to a part and have connectivity with other elements. The part has section properties, material properties and hourglass control properties. The connectivity is defined by the nodes on the element. Thus the element definition can be seen as a hierarchy as follows: *ELEMENT,eid,pid,nid1,nid2,nid3,nid4 *NODE,nid,x,y,z ... *PART,pid sid, mid, eosid,hgid *SECTION_SHELL,sid,elform,shrf,nip,propt,qr,icomp *MAT_ELASTIC,mid ro,e,pr,da,db *EOS,eosid *HOURGLASS,hgid In most cases the equation of state (*EOS) and hourglass (*HOURGLASS) options can be ignored. Page 4.5
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Oasys LS-DYNA Environment 8.1 VOLUME 3 ... - Oasys Software

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