ADVANCED LOADING

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ADVANCED LOADING

It is possible to define more complex loads in FEMGEN by the use of Time Curves, Space Curves, Load Masks, and Local Coordinate Systems. These data types are defined separately to the load using the CONSTRUCT command and appended to the load using the PROPERTY ATTACH command. It is thus possible to define a simple load and then increase the complexity of its definition by progressively appending more data to it. Figure 2.109 illustrates the data types which may be associated with a simple load.

**Figure 2.109:** Load Data Structure
$\begin{figure} \centerline{ \psfig {figure=diagrams/load.ps,width=5.0in} }\end{figure}$

TCURVE	=	time curve definition (see CONSTRUCT TCURVE)
SCURVE	=	space curve definition (see CONSTRUCT SCURVE)
LMASK	=	load mask definition (see CONSTRUCT LMASK)
CSYSTn	=	local coordinate system definition (see CONSTRUCT COORDSYS)

Examples:

1.

PROPERTY LOAD FORCE LO1 S1 100 1
LABEL MESH LOADS

**Figure 2.110:** Simple Load
$\begin{figure} \centerline{ \psfig {figure=diagrams/load1.ps,width=3.0in} }\end{figure}$

This is a simple load definition to which more complex data will be defined and attached in the following examples.

2.

CONSTRUCT COORDSYS CYLINDRIC CY1 P1 P2 P3
PROPERTY ATTACH LO1 CY1
DRAWING DISPLAY

**Figure 2.111:** Load with local coordinate system added
$\begin{figure} \centerline{ \psfig {figure=diagrams/load2.ps,width=3.0in} }\end{figure}$

Local Coordinate systems are used to modify the direction of a load and are thus usually reserved for nodal vector loads. A typical application would be to specify a radial load on a circular part by the application of a local cylindrical coordinate system.

3.

CONSTRUCT LMASK LM1 SURFACE .2 .8 .2 .8
PROPERTY ATTACH LO1 LM1
DRAWING DISPLAY

**Figure 2.112:** Load with load mask added
$\begin{figure} \centerline{ \psfig {figure=diagrams/load3.ps,width=3.0in} }\end{figure}$

Load Masks are used to limit the extent of a load. Load Masks may be defined either in terms of parametric (0-1) distances on the loaded part's geometry or in terms of the global coordinate system. It is possible to append a local coordinate system to a load mask defined in the global coordinate system. A typical application might be the definition of the water line on a ship model.

4.

CONSTRUCT SCURVE SC1 SURFACE LINE L1 ELIPSE 10
PROPERTY ATTACH LO1 SC1
DRAWING DISPLAY

**Figure 2.113:** Load with space curve added
$\begin{figure} \centerline{ \psfig {figure=diagrams/load4.ps,width=3.0in} }\end{figure}$

Space curves are used to describe the variation of a load in space and consist of a number of locations and associated values by which the basic load is multiplied. Space curves may be defined either in terms of parametric (0-1) distances on the loaded part's geometry or in terms of the global coordinate system. It is possible to append a local coordinate system to a space curve defined in the global coordinate system. A typical application would be the radial variation of a load on a circular geomery.

5.

CONSTRUCT TCURVE TC1 RAMP 1 1
PROPERTY ATTACH LO1 TC1
DRAWING DISPLAY

**Figure 2.114:** Load with time curve added
$\begin{figure} \centerline{ \psfig {figure=diagrams/load5.ps,width=3.0in} }\end{figure}$

Time curves are used to describe the variation of a load with time and are usually applicable only to dynamic analyses. The Time Curve is a list of times and amplitude values by which the basic load is multiplied. Example applications might be the magnitude of a pressure pulse from an explosion or the variation in film coefficients and temperatures on the boundary of a transient heat transfer analysis.

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Femsys Limited
1st October 1999