SDT-base         Contents     Functions              PDF Index

7.9  Curves and data sets

• Multi-dim curve
• tdof (outputs), DOF, dof (input/output pair)
• FEM Result
• Inputs
• Response data associated with inputs and outputs
• Shapes at IO pairs

Curves are used to specify Inputs (for time or frequency domain simulation) and store results from simulations. The basic formats are the Multi-dim curve and FEM result def. For experimental modal analysis, Response data and Shapes at IO pairs are also used.

All these formats can be displayed using the iiplot interface. For extraction see fe_def SubCh.

Multi-dim curve

A curve is a data structure with fields

The following gives a basis generation example.

 t=linspace(0,10,100)';lab={'ux';'uy'};
 C1=struct('X',{{t,lab}},'Xlab',{{'Time','DOF'}}, ...
  'Y',[sin(t) cos(t)],'name','Test');
 iicom('curveinit',C1.name,C1);iicom('ch1:2');

tdof (outputs), DOF, dof (input/output pair)

SDT identifies quantities involved in FEM and test. Different fields are used for different context.

• .DOF is used to identify fields at nodes. This is the standard DOF definition of the form NodeID.DOFID introduced in section 7.5.
• .dof is a matrix used to identify input/output pairs. The columns are
  1. RespNodeID.RespDOFID identifier of the output / sensor. This is typically called SensId
  2. ExciNodeID.ExciDOFID identifier of the input / actuator
  3. address are optional integer numbers used to identify columns of xf matrices. They typically correspond to a measurement channel number.
  4. RespGroupID optional identifiers of group names given in the nmap('Map:Group') entry.
  5. ExciGroupID optional identifiers of group names given in the nmap('Map:Group') entry. (this is really only supported by ufread).
  6. FunID correspond to universal file format specification but unused.
  7. LoadCase identifier of experiment.
  8. ZaxisValue for experiments that depend on another parameter (rotation speed, ...)
  this field corresponds to data in line 6 of ufread 58 except for address, stored in the measurement label in Test-Lab for example.
• .tdof is a column vector of SensId typically with the form RespNodeID.RespDOFID) used for response at sensors. It does not allow repetitions found in the .dof field where the same sensor can be used for multiple inputs.

  For test/analysis correlation, it is associated with the sensor topology definition described in section 4.7 where additional columns are added to the .tdof field to describe the supporting node and a general measurement direction.

FEM Result

See section 7.8 or sdtweb('def'), uses the .def, .DOF, .data fields.

Inputs

Inputs for time or frequency simulations are stored as entries {'curve', Name, data} in the model stack or in the case of inputs in the load.curve cell array.

A curve can be used to define a time (or frequency) dependent load {F}=[B]{u}. [B] defines the spatial distribution of the load on DOFs and its unit is the same as F. [B] is defined by a DOFLoad entry in the Case. {u} defines the time (or frequency) dependency as a unitless curve. There should be as many curves as columns in the matrix of a given load def. If a single curve is defined for a multi-load entry, it will affect all the loads of this entry.

As an illustration, let us consider ways to define a time dependent load by defining a .curve field in the load data structure. This field may contain a string referring to an existing curve (name is 'input' here)

 model=fe_time('demo bar');fe_case(model,'info')

 % Define input curve structure (single input step) 
 % For examples see: sdtweb fe_curve#Test 
 model=fe_curve(model,'set','input','TestStep t1=1e-3');

 % define load.curve{1} to use that input
 model=fe_case(model,'setcurve','Point load 1','input');

 % Run a simulation
 TimeOpt=fe_time('timeopt newmark .25 .5 0 1e-4 100');
 model=stack_set(model,'info','TimeOpt',TimeOpt);
 def=fe_time(model); feplot(model,def); fecom ColorDataAll

It is also possible to directly define the .curve field associated with a load

 model=fe_time('demo bar');fe_case(model,'info')
 model=fe_case(model,'remove','fd'); % loads at both ends
 data=struct('DOF',[1.01;2.01],'def',1e6*eye(2),...
             'curve',{{'test ricker dt=1e-3 A=1',...
                       'test ricker dt=2e-3 A=1'}});
 model = fe_case(model,'DOFLoad','Point load 1',data);

 TimeOpt=fe_time('timeopt newmark .25 .5 0 1e-4 100');
 model=stack_set(model,'info','TimeOpt',TimeOpt);
 def=fe_time(model); feplot(model,def); fecom ColorDataAll

Response data associated with inputs and outputs

Response data sets xfstruct correspond to groups of universal files of type UFF58 that have the same properties (type of measurement, abscissa, units, ...). They are used for identification with idcom while the newer curve format is used for simulation results. They are characterized by the following fields

The .w and .xf fields contain the real data while other fields give more precision on its nature.

The idopt field is used to point to identification options used on the data set. These should point to the figure options ci.IDopt.

The .group field is used to associate a name to the group identification numbers RespGroupID ExciGroupID defined in the .dof columns 4 and 5. These names are saved by ufwrite and used for geometry identification.

The load field describes loading cases by giving addresses of applied loads in odd columns and the corresponding coefficients in even columns. This field is used in test cases with multiple correlated inputs.

Shapes at IO pairs

Shapes at DOFs is used to store modeshapes, time responses defined at all nodes, ... and are written to universal file format 55 (response at nodes) by ufwrite. The fields used for such data sets are