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

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Oasys LS-DYNA Environment: User Guide (Version 8.1) ! Node coordinates ! Shell, solid, beam or thick shell elements unless a whole PART is deleted. ! Element topology ! Element part references ! Element formulations ! Material types ! Anything else which affects storage of element stresses etc, such as element local axis systems. ! Seatbelt retractor, slipring, pretensioner and sensor properties ! Airbag parameters ! Rigid body properties (centre of mass, mass inertia tensor) ! Initial velocities ! Rigid body extra nodes, merges and anything else that determines which nodes are part of which rigid body. Other features can in theory be changed, but are likely to cause sudden jumps in stresses when the restart occurs; the jumps can in some situations be so violent that the analysis crashes. Such features include: ! Material properties (including properties for spring and belt elements) ! Section properties ! Joint stiffness and connectivity The following things can be changed: ! Anything to do with contacts - even introduction of new contact surfaces. All contact parameters can be changed. ! Restraints, constraints and other boundary conditions. ! Load curves ! Control parameters (e.g termination time) and output intervals It is also possible to add new nodes, elements, parts, etc which were absent from the original analysis, and to omit whole parts which were present in the original analysis. The new parts will be undeformed at the beginning of the restart analysis, in this case further input is required after *STRESS_INITIALISATION. This can be used for multi stage sheet metal pressing simulations: the tool models can be replaced at the end of each stage. There are some bugs in LS-DYNA affecting full-deck restarts: ! Spotwelds and tie-break contacts (types 8 & 9) which had failed in the original analysis became stuck together again in the restart. ! The previous history of non-linear contacts (types 9, 20, 21) is lost. The force developed on any contacts which was unloading at the time of the restart suddenly jumps to the force registered on the loading curve at the current displacement. Page 3.6
Oasys LS-DYNA Environment: User Guide (Version 8.1) 4.0 KEYWORD INPUT The new keyword input database in this version provides a more flexible and logically organised database that will hopefully reduce the time required by new users in understanding the input. Similar functions are grouped together under the same keyword. For example, under the keyword *ELEMENT we not only include solid, beam, and shell elements, but also spring elements, discrete dampers, seat belts, and lumped masses. In previous versions these elements were specified in separate and disjoint sections of the user's manual. Materials and contact algorithms are specified by names and not by type numbers making the data more readable by those less familiar with the program. The first card should be *KEYWORD. This indicates that the input deck is in keyword format and follows this manual. Alternatively KEYWORD may be specified on the execution line. LS-DYNA Keyword Manual is alphabetically organized in logical sections of input data. Each logical section relates to a particular input. There is a control section for resetting LS-DYNA defaults, a material section for defining constitutive constants, an equation of state section, an element section where element part identifiers and nodal connectivities are defined, a section for defining parts, and so on. Nearly all model data can be input in block form. For example, consider the following where two nodal points and shell elements are defined: $ $ DEFINE TWO NODES $ *NODE 10101 x y z 10201 x y z $ $ DEFINE TWO SHELL ELEMENTS $ *ELEMENT_SHELL 10201 pid n1 n2 n3 n4 10301 pid n1 n2 n3 n4 Alternatively, acceptable input could also be of the form: $ $ DEFINE ONE NODE $ *NODE 10101 x y z $ $ DEFINE ONE SHELL ELEMENT $ Page 4.1
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Oasys LS-DYNA Environment 8.1 VOLUME 3 ... - Oasys Software

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