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nl_inout

• DofSet
• Power
• FuTable
• K_t
• MexIOa
• SCLd
• LRFu
• slab sensor non-linearity
• temp still undocumented

Purpose

The generic form of NLdata specification is discussed in section ??.

DofSet

Implementation of linear or large rotation setting of DOF values from time curves of a fe_case DofSet entry. sdtweb('_eval;','d_fetime.m#NLNewmark_LrDofSet').

Supported variants are

• large rotation trajectories (using MBBryan) uses .unl(:,:,1) corresponding to large displacement and updates .unl(:,:,j1) when changing time step to allow velocity computations (currently only valid for fixed time step). Requires setting .KeepDof=1 and enforcing 6 DOF associated with the master node.
• translation trajectories (xxx).

Power

uses NLdata.opt=[comstr('Power',-32) k n] and s_nl=k u_nlⁿ.

FuTable

uses tabular definitions in either NLdata.Fu or NLdata.Fv. If you want a case with both simultaneously to be reimplemented please provide a test case. Implements a Jacobian using tangent stiffness. Run example with sdtweb('_eval;','d_fetime.m#ModalNew_FuTable').

K_t

Implement time varying matrices and DofSet xxx.

MexIOa

Implements callback to user defined .m file implementations of non-linearities as detailed in section ??.

SCLd

Large displacement surface contact supported as part of the contact module (see sdtweb(xxx)). Possible application : rail/wheel contact. This supports low pass filtering of contact forces, using an evolution equation of the form Ḟ_c/ω_c + F_c = k_c g (for a positive constant) or Ḟ_c/ω_c + F_c = k_c √(g) for a negative constant. This avoids incorrect bouncing of stiff contacts in implicit computations and ω_c should be a fraction of the sampling frequency (inverse of time step) or the maximum mesh frequency.

LRFu

Large rotation tabular spring for multi-body applications. cbush kinematics are expected and rotations are assumed using Bryan angles in radians. Requires one non-linearity for each spring (not currently vectorized). The NL.Node field gives slave and master node for each body (4 nodes). The observed motion is given at the master node and large rotation is used to determine the current position of the slave node. With single axis springs (large rotation rod) the position of the two slave nodes should be disjoint.

The stress vector used by this non-linearity contains 24 elements

• sx1,sy1,sz1,srx1,sry1,srz1 forces and moments on node 1
• sx,sy,sz,srx,sry,srz forces and moments on node 2
• PX1,PY1,PZ1,rx,ry,rz absolute position of node 1 and rotations
• ux,uy,uz relative displacements in x,y,z directions, sex,sey,sez force in element frame.

slab sensor non-linearity

This non-linearity supports observation of various quantities during FEM computations. The base definition is associated with the sdtweb('sensor# scell')

• For direct resultant sensors in time integration schemes using enforced displacement -fieldOut4, leading to NL.iopt(6+isens)==4. See more details in xxx

Needs documentation, see sdtweb d_fetime('slab').

  NL=struct('type','nl_inout','slab',{li(:)},'UserObs',dyn_solve('@doObs'));
  mt=stack_set(mt,'pro','Sensors',struct('il',1e5-1,'type','p_null', ...
       'NLdata',NL));  

Note that in predictor/corrector schemes, it may be necessary to recompute the residual to obtain the correct residual.

temp still undocumented

• FuExpon s_nl=a b^u_nl.
• uMaxw generic C implementation of nl_maxwell.m file
• FuDahlC Dahl model with constant force
• STS PSA scalar STS
• CLIMA2 connector non-linearity developed with Marco Rosatello
• FuFric basic friction model with F_k=Ku bounded by ± F_max.
• nl_bset xxx
• DofSet xxx