2.6 THE PLOT PROGRAM Z88P

The more modern Z88 plot program is the new OpenGL plot program Z88O, ref. Chp. 2.11. However, the approved plot program Z88P stays part of the Z88 FEA system.

The plot program Z88P plots undeflected, deformed, both undeflected and deflected structures as well as super structures.

Z88P can plot on the screen or into a file. The plot file contains so-called HP-GL commands which are used by HP plotters. Of course, it is optional to process the HP-GL files also in other programs, e.g. in CorelDraw, WinWord etc. If necessary change the ending .TXT. E.g. Winword expects the ending . HGL or .PLT for HP-GL files.

In addition, von Mises stresses can be plotted on the screen or send to a plotter. The screen colors can be adjusted for Windows in the file Z88P.COL. The file Z88.FCD for the UNIX operation system allows for much more possibilities in changing colors and fonts as well as the sizes and locations of the pushbuttons, radioboxes etc. You can completely modify the whole appearance of Z88P for UNIX as you wish.

Needed Files | Super structures | Undeflected FE struc. | Deflected FE struct.
Z88NI.TXT | Yes | No | No
Z88I1.TXT | No | Yes | Yes
Z88O2.TXT | No | No | Yes
Z88O5.TXT | No | Yes, for Mises stresses | No

For fastest operation Z88P connects the nodal points with straight lines, although for Serendipity elements 7, 8, 10, 11 and 12 the edges of the elements are square or cubic curves.

Note: You can also use your CAD program together with CAD converter Z88X to plot super structures and undeflected finite element structures, yet deflected structures and von Mises stresses do need Z88P. Or convert Z88's plot files (HP-GL language) into DXF files: CorelDraw does a very good job.

Z88P saves the last structure file name, the several factors and label adjustments in a file Z88P.STO. This file is loaded when starting Z88P, so that the last structure is restored automatically. If you like to start with a new structure, the file Z88P.STO should be deleted before launching Z88P. This can be done with Plot > Delete Z88P.STO (Windows) or Plot with option rm z88p.sto (UNIX) in the Z88-Commander Z88COM.

Special key strokes for Windows:

Prior: increase zoom
Next: decrease zoom
Cursor left: panning X direction
Cursor right: panning X direction
Cursor up: panning Y direction
Cursor down: panning Y direction

..And in addition for 3-D structures for Windows:

Home: panning Z direction
End: panning Z direction
F2: rotate around X axis
F3: rotate around X axis
F4: rotate around Y axis
F5: rotate around Y axis
F6: rotate around Z axis
F7: rotate around Z axis
F8: reset all rotations to 0

Under UNIX use the usual X and Motif key assignments: Tab key and arrow keys for choice and space bar for activation.

Pen plotters draw the undeflected structure with pen 1 and the deflected structure with pen 2.

Explanation of some menu items:

Name of Structure File:

Windows: File > Structure File
UNIX: Stru. text field directly on window

Choose the structure file here. Enter name, if necessary with path, press return. The new stucture is loaded and drawn immediately.

Name of Plotter File:

Windows: File > Plotfile
UNIX: Plot. text field directly on window

Choose a plotter file name here. Default name is Z88O6.TXT. The plot file includes HP-GL commands in ASCII code ready for reprocessing by other programs, e.g. CorelDraw.

Windows: Serial plotters: A direct output from Z88P to a plotter does not always work. If necessary, put Xon/Xoff sequence in Z88O6.TXT with the Z88-Commander after producing Z88O6.TXT. Then Z88O6.TXT can be send to a serial plotter by

copy /B Z88O6.TXT com1: (or com2:)

You also can use the Hyperterminal of Windows. Try ASCII, CR-LF ending, local echo, line delay 10 msec, byte delay 1 msec. However, large files can cause timeouts. This is a generally poor attribute of serial interfaces, cf. the notes below for UNIX.

Windows: HP LaserJet: Some laser printers can be switched from PCL mode to HP-GL mode by hand, for others this works unfortunately only by software. In this case put a LaserJet sequence in Z88O6.TXT with the Z88-Commander Z88COM after producing Z88O6.TXT. Then do normal printing.

UNIX: Serial plotters: Serial interfaces are adjusted with the stty-command as root

stty sane ixon ispeed 9600 cs8 -cstopb -parenb < /dev/ttyS1

Here /dev/ttyS1 is the second serial interface. The first serial interface is /dev/ttyS0 . If your plotter needs a software switchover on protocol Xon/Xoff, start the little utility pxon88 after the production of Z88O6.TXT by Z88P . Then send Z88O6.TXT as root to the interface:

cat z88o6.txt > /dev/ttyS1

You can also put the serial plotter as a raw-device into /etc/printcap directly. Lets say it would be called HP7475A-a3-raw there. As a normal user you can then plot via the UNIX spooling system

lpr -PHP7475A-a3-raw z88o6.txt

Caution: Serial pen plotters are extremely slow devices, i. e. they can plot a lot due to the very efficient HP-GL language with extremely little information. For huge HP-GL files this can have the effect that the serial interface - despite Xon/Xoff - delivers far too few bytes to the plotter and therefore gets a timeout. See these general difficulties for LINUX under /usr/doc/howto at printer-howto and serial-howto.

UNIX: LaserJet: Some laser printers can be switched from PCL mode to HP-GL mode by hand, for others this works unfortunately only by software. In this case put a LaserJet sequence in Z88O6.TXT by the little utility laserj88 after producing Z88O6.TXT with Z88P. Take care that laser printers have a raw entry in /etc/printcap as the UNIX spooling system is supposed to pass the HP-GL files completely unfiltered. Plot using

lpr -Praw z88o6.txt

Notes Windows and UNIX: The HP-GL commands produced by Z88 work faultlessly on several HP and IBM plotters if the physical adjustments are fixed correctly. Check out if your plotter is actually 100 % HP-compatible !

Another predefined file name is Z88O7.TXT. You can store the undeflected structure in Z88O6.TXT and the deflected structure in Z88O7.TXT if you do not want to do it by the Z88P command Structure > Un- and Deflected. The file Z88O7.TXT can be appended alternatively to Z88O6.TXT later allowing the plotting of the undeflected and the deflected structure in one run. Mind the order: Store Z88O6.TXT first, then Z88O7.TXT. But you can also plot completely different structures.

Deformation Modes of the Structure:

Windows: Structure > Undeflected, Deflected, Un- and Deflected
UNIX: Radio box Undefle., Deflected, Un+Defle.

Plots the undeflected structure, the deflected structure or both. Stresses can be plotted only on undeflected structures. When using Un- and Deflected nodes and element labels are plotted on the undeflected structure.

Caution Deflected and Un- and Deflected: The user must have executed a calculation of displacements before using this function. Do a FEA run with Z88F before using Z88P. Otherwise, some old files Z88O2.TXT (displacements) from earlier Z88 runs are opened causing totally wrong results !!

Output in Plotter File:

Windows: Output > CRT, Plotter
UNIX: Pushbutton Plot.

Default is plotting on the screen (CRT). Selecting Plotter produces a HP-GL file whose name has been selected with Interface at choice. This runs very fast. Z88P shifts back again immediately to CRT after storing the HP-GL file and after quitting the message box.

Choice of View:

Windows: View > XY, XZ, YZ, 3-Dim
UNIX: Radio box XY, XZ, YZ, 3D

Select view depending on structure: At 2-dimensional structures XY, at 3-dimensional structures 3-Dim. Mind 3-D structures: The desired side views can be shown with XY, XZ and YZ, however, the nodes and element labels are plottet ascendingly (starting with node 1 or element 1 ascending to the last node or element), the stress points in the order of the Gauss points, ascending from element to element. The finished pictures can therefore show nodes and element numbers as well as stresses which does not really lie in the level of the side view! Only 3-D view gives reliable information. Note: If starting with a "fresh" 3D- structure in Z88P you will see under Windows the menu hook improperly set on XY or under UNIX the radio button XY set, because the menus are built up before reading the Z88 files. Do not care.

Drawing Node and Element Numbers:

Windows: Labels > No Labels, Elements, Nodes, Label All
UNIX: Radio box No Labels, Elements, Nodes, Both

Plot the element numbers or the node numbers or both or skip numbering. Labeling can get confusing because, depending on view, different numbers of complicated space structures are plotted several times at the same location. Carefully place structure parts by corresponding rotations.

Coordinate System:

Z88P uses a coordinate system which starts in the center of the CRT or the center of the sheet. It is fixed as follows:

Axis | CRT min | CRT max | Plotter min | Plotter max
X | -100 | +100 | -138 | +138
Y | -100 | +100 | -100 | +100
Z | -100 | +100 | -100 | +100

For 3-D structures the transformation of the 3-D coordinates to the 2-D CRT or plotter is carried out via an isometric view ref. ISO 5. If the rotation angles ROTX, ROTY and ROTZ are set to 0 respectively, then is valid: X : Y : Z = 1 : 1 : 1. Z points up and X and Y are tilt by 30 degrees.

Windows: The rotation angles can be modified by steps of 10 degrees with the buttons F2 to F7 or with Factors > Rotations 3-D in optional values. F8 resets all rotation angles to 0 degrees.

UNIX: The rotation angles can be modified by steps of 10 degrees with the Pushbuttons RX+, RX-, RY+, RY-, RZ+ and RZ-. Pushbutton Rot 0 resets all rotation angles to 0 degrees.

Plots fitting entirely on the screen usually work with the same factors for the plotter. However, because plotters have different X-Y ratios, factors need to be changed slightly for plotter output sometimes.

Global Magnifications:

Windows: Factors > Global Magnifications

Do zooming either in steps with the keys Prior and Next or delicately with factors FACX, FACY, FACZ. The entry of factors is also useful if several structures should be plotted using the same factors.

UNIX: Pushbuttons Zoom+ and Zoom-

Panning:

Windows: Factors > Centre Factors

Do panning into X direction with left and right cursor keys, into Y with cursor up and cursor down and into Z (at three-dimensional structures) with Home and End. Alternatively you can use Factors > Centre Factors : CX, CY and CZ.

UNIX: Pushbuttons X+, X-, Y+, Y-, Z+, Z-

Enlarging Deflections:

Windows: Factors > Deflections
UNIX: Text fields FUX, FUY and FUZ

Enlarge the computed deflections with the factors FUX, FUY and FUZ. Default values are 100. Attention UNIX: As usual for UNIX, the changes only apply at a respective Return. However, you can type in all three fields without Return and then press the Pushbutton Regen (for Regenerate).

Rotations:

Windows: Factors > Rotations 3-D

The rotations around X, Y and Z axises are defined with Factors > Rotations 3-D : ROTX, ROTY and ROTZ. Default values are 0. With the F2 . . F7 keys the structure can be revolved in steps of 10 degrees.

UNIX: Pushbuttons RX+, RX-, RY+, RY-, RZ+, RZ-

Turn in steps of 10 degrees. Pushbutton Rot 0 resets the rotations to 0.

Height Ratio:

Windows: Factors > X-Correction FXCOR
UNIX: Text field FXCOR

With the function X-Correction FXCOR the height ratio can be adjusted to the monitor customization. The default values are 0.75 for NT and 0.85 for UNIX. Modify FXCOR depending on monitor type if necessary. FXCOR is stored in Z88P.STO for further use.

Von Mises Stresses:

Windows: Mises Stresses > No von Mises stresses, Show von Mises stresses
UNIX: Pushbutton Mises

If you have calculated von Mises stresses by Z88D (only useful and possible for continuum elements of the type 1, 3, 6, 7, 8, 10, 11, 12, 14, 15, 16, 17, 18, 19 and 20) then you can plot the von Mises stresses either into the Gauss points (elements No.1, 7, 8, 10, 11 and 12) or into the center of gravity of the elements (elements No.3 and 6). Possible for CRT and Plotter.

Stresses will only show if you have chosen Structure > Undeflected. Z88P otherwise recalls that you wanted to plot von Mises stresses and shows them when switching from Show von Mises stresses to Structure > Undeflected.

If you choose Show von Mises stresses and then Output > Plotter the von Mises stresses are converted into a letter scale from A to J to match even ancient pen plotters with only 2 or 6 pens or monochrome laser printers.

On the screen the stresses are plottet using a color scale. You can adjust this color range in Z88P.COL (Windows) or Z88.FCD (UNIX) to match your personal wishes.

Consult the output file Z88O3.TXT for exact stress results because Z88P shows stresses only in a 10-step range.

Caution: The operator is responsible for first running a stress calculation by Z88D before using this function. Run Z88F or the Iteration solver for calculating the displacements and then the stress processor Z88D before starting Z88P. Otherwise some old stress files Z88O5.TXT from earlier calculations are read causing totally wrong results !!

Keep in mind:

- Calculate stresses with Z88D. Enter 1 for the von Mises flag ISFLAG in the file Z88I3.TXT and a value greater than 0 for the integration order INTORD in Z88I3.TXT when using elements 1, 7, 8, 10, 11 and 12.
- Von Mises stresses are only computed for continuum elements of type 1, 3, 6, 7, 8, 10, 11, 12, 14, 15, 16, 17, 18, 19 and 20.
- Switch to Undeflected.
- Take into account: For showing a "nice" stress scale make the stresses in the range from 0 to 100 or from 0 to 1,000. If necessary enter modified boundary conditions and recalculate to real results. This is because the stress scale is built of integer results.

Automatic Scaling:

Windows: Autoscale > No Autoscale, Yes Autoscale
UNIX: Pushbutton AutoS

The Autoscale function takes care that structures will completely fit on the screen.

Autoscale activates automatically if no file Z88P.STO is available or if a new structure is loaded by File > Structure File. Autoscale again is deactivated immediately and the hook points to No Autoscale. If a file Z88P.STO is present the factors are read from this file. You can then scale properly with Autoscale > Yes Autoscale. However, Autoscale switches again immediately to No Autoscale. Autoscale > Yes Autoscale is a kind of pushbutton. The explanation above corresponds to UNIX as well.