CONSTRUCT TCURVE [tcurve] Type Parameters or ... tcurve Modifier

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CONSTRUCT TCURVE [tcurve] Type Parameters
or ... tcurve Modifier

FEMGEN Command only.

This command is used to define a time curve in terms of a time and an amplitude at that time. The curve may be defined as a list of time, amplitude pairs or via a function (e.g. sine, exponential decay etc.). Lists may be read in from a file or typed in at the keyboard; functions are defined interactively using a small number of control parameters. Time curves may be attached to loads in order to vary the magnitude of a load during analysis for those analysis packages which support such features.

Type	Parameters	Meaning

LIST	tn, an etc.	time, amplitude pairs
	FILE filename	name of ascii file containing t,a pairs
STEP	t	length of step
	a	amplitude of step
	[tdelay]	delay before start of step (0)
	[tstop]	termination time after end of step (t)
RAMP	t	length of ramp
	a	amplitude of ramp
	[tdelay]	delay before start of ramp (0)
	[tstop]	termination time after end of ramp (t)
SINE	period	period of the sine wave
	a	amplitude of the sine wave
	[phase]	phase shift expressed as a time (0)
	[a₀ ]	amplitude shift (0)
	[tstop]	termination time (period)
EXPONENT	A₀ , A , t₀ , t_d , [tstop]	a = A₀ + A*exp[-(t-t₀)/t_d]

Time curves may be modified by repeating the time curve command with different parameters. Time curves may also be modified using the commands listed below.

Modifier	Type	Meaning

TSHIFT	real	shifts a list by adding real to all times
ASHIFT	real	shifts a list by adding real to all amplitudes
TSCALE	real	scales a list by multiplying all times by real
ASCALE	real	scales a list by multiplying all amplitudes by real
TSTART	real	define start time in list if not t1
TSTOP	real	define end time in list if not tn
SMOOTH	rad	round off corners on list, step, and ramp with radius rad
CYCLIC	YES	curve is cyclic
	YES n:	curve is repeated n times
	NO	switch cyclic off
DIVISIONS	integer	number of sampling points for function (100)

**Figure 2.48:** Definition of a time curve
$\begin{figure} \centerline{ \psfig {figure=diagrams/tcdef1.ps,width=5.0in} }\end{figure}$

Notes:

1.: Default names
If no name is entered a default name is created, this is TCn where n is a count of defined time curves. The default name can be changed with the CONSTRUCT NAME command.
2.: Shifting a list time curve
Where a list of time curve values read from a file do not align exactly with t=0 a TSHIFT may be introduced in order to move the curve if desired. The ASHIFT subcommand may similarly be used for amplitude shifts.
3.: Scaling a list time curve
The TSCALE and ASCALE subcommands may be used to change the system of units for a list time curve which has been read in from file.
4.: Selecting portions of a time curve Parameters TSTART and TSTOP may be used to select a section of a list time curve rather than using the whole curve. The resulting partial time curve will be shifted so that the start time is always 0.
5.: Reading lists from a file
It is possible to read in long lists of time curve data from file. The file must be ascii and have one t,a pair on each line. The t,a values must be separated by either a comma or a space. The maximum allowable number of pairs is machine dependent but will be at least 10000.
6.: Viewing time curves
Time curves may be viewed by using the command UTILITY GRAPH TCURVE and switched off with UTILITY GRAPH OFF.

Examples:

1.

CONSTRUCT TCURVE LIST 0 0 .2 1 .8 1 1 0

**Figure 2.49:** LIST time curve
$\begin{figure} \centerline{ \psfig {figure=diagrams/tclis.ps,width=3.5in} }\end{figure}$

2.

CONSTRUCT TCURVE STEP 1 5 1 10

**Figure 2.50:** STEP time curve
$\begin{figure} \centerline{ \psfig {figure=diagrams/tcstep.ps,width=3.5in} }\end{figure}$

3.

CONSTRUCT TCURVE RAMP 1 5 1 5

**Figure 2.51:** RAMP time curve
$\begin{figure} \centerline{ \psfig {figure=diagrams/tcramp.ps,width=3.5in} }\end{figure}$

4.

CONSTRUCT TCURVE SINE 10 3 0 5

**Figure 2.52:** SINE time curve
$\begin{figure} \centerline{ \psfig {figure=diagrams/tcsine.ps,width=3.5in} }\end{figure}$

5.

CONSTRUCT TCURVE EXPONENT 0 5 0.2 0.2 1

**Figure 2.53:** EXPONENT time curve
$\begin{figure} \centerline{ \psfig {figure=diagrams/tcexp.ps,width=3.5in} }\end{figure}$

6.

CONSTRUCT TCURVE TC1 RAMP 1 5 1 5
CONSTRUCT TCURVE TC1 SMOOTH .3

**Figure 2.54:** SMOOTH time curve
$\begin{figure} \centerline{ \psfig {figure=diagrams/tcsmoo.ps,width=3.5in} }\end{figure}$

7.

CONSTRUCT TCURVE TC1 LIST 0 0 .2 1 .8 1 1 0
CONSTRUCT TCURVE TC1 CYCLIC YES 3

**Figure 2.55:** CYCLIC time curve
$\begin{figure} \centerline{ \psfig {figure=diagrams/tccyc.ps,width=3.5in} }\end{figure}$

8.

CONSTRUCT TCURVE TC1 SINE 10 3 0 5
CONSTRUCT TCURVE TC1 DIV 20

**Figure 2.56:** Low resolution time curve
$\begin{figure} \centerline{ \psfig {figure=diagrams/tcdivs.ps,width=3.5in} }\end{figure}$

See also the following commands

'CONSTRUCT NAME'
'CONSTRUCT LMASK'
'CONSTRUCT SCURVE'
'PROPERTY ATTACH'
'PROPERTY LOAD'
'UTILITY DELETE'
'UTILITY TABULATE'

Next: CONSTRUCT TRANSFORM Up: Primary Command CONSTRUCT Previous: CONSTRUCT SPACE WORK-BOX Control

Femsys Limited
1st October 1999