Fatigue User’s Guide > Weld Analysis > Polar Display (MPOD)
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX''">XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX''">   
Polar Display (MPOD)
The polar display module, MPOD, displays paired [X-Y] data files, normally’theta-R’ files with a .pdm extension. Displays may be scaled in various ways. Functions for windowing specific fields and picking off coordinate pairs are also available.
MPOD cross-plots polar plots that are generated by both the multiaxial fatigue analysis modules, MMLF and FEMLF, and the spot weld analyzer, SPOTW.
MPOD Module Operation
The MPOD module can be run in one of the following three ways:
• From the MSC.Fatigue menu systems as spawned from the MMLF, FEMLF and SPOTW modules
• In stand alone mode by typing mpod at the system prompt
• By incorporating the MPOD batch commands.
Modes one and two are interactive. Once running in interactive mode the MPOD module will prompt with the following screen:
Figure 9‑29 Naming the MPOD Input File
MPOD plots the contents of a paired (,R) data file. By default it expects this file to be a standard paired file with an extension of .pdm and so if such a file is to be displayed, it is only necessary to enter its name, the extension may be omitted.
MPOD will expect to find the input data files to be resident in the user’s directory. However, other directories can also be accessed if the complete file specification, (path name and file name) is entered. If the Alter setup question it set to Yes, then a second window appears. The purpose of each of its fields is as follows:
Figure 9‑30 Altering the MPOD Setup File
The input fields are as follows:
 
Option
Description
R-Axis Minimum
For the purpose of scaling the display, the minimum value of R to be included in the plot may be specified in physical units. The minimum value of the R parameter present in the data file is given as the default limit.
If a value greater than the minimum value is specified then some data will be excluded from the plot.
R-Axis Maximum
For the purpose of scaling the display, the maximum value of R to be included in the plot may be specified in physical units. The maximum value of the R parameter present in the data file is given as the default limit.
If a value smaller than the maximum value is specified then some data will be excluded from the plot.
Plot Type
Having specified the R axis limits, it is now possible to define if the plot is to be generated by displaying the θ-R coordinate pairs discretely (a scatter plot) or if the data are to be plotted by joining up between adjacent values (a joined plot) or both.
Plot 1 in n
Not every point in the file has to be displayed. To display a plot more quickly, enter a number n and only every n'th plot will be displayed.
It also allows hard copies to show adequately the pattern of data in a file with many points without taking too long to physically produce. The selection of either scattered or joined plots is arbitrary. However, scattered plots will, by and large, take longer to plot than joined plots. Joined plots are generated some 30% faster than scatter plots and so they are recommended for longer data sets. In either case, cross-plotting data can be time consuming and care must be taken in selecting the data to plot.
Scaling Options
(Scale R)
Two scaling options for the R axis are possible.
Linear - Linear R
Linear - Log R
Linear-Linear scaling is the default. Set the required option with the left mouse button.
Display Data Sets [1-n]
If the file selected has more than 1 data set, then they can be plotted selectively. Enter the number of the data sets you wish to have plotted. The numbers can be separated by commas. For example 1, 5, 18, will display the 1st, 5th, and 18th data sets.
Change in Shapes
Shapes on/off allows the user to have each data set plotted with a different shaped symbol. For example one set of data points can be plotted with small crosses, another with small triangles, another with small squares etc. Change in Shape=no plots all the data set with the same shaped symbol. When the above fields have been filled, selecting OK will cause MPOD to plot the data.
Clicking the OK button either after altering the setup or without altering the setup will result in a polar plot. When the polar plot is displayed, various manipulation options are available.
Polar Plot Manipulation
The screen is split into 3 regions:
• the prompt line dialog box
• the menu along the top of the form
• the graph area in the centre of the screen.
Figure 9‑31 The MPOD Graphics Screen
The dialog area is used for the following:
• Supplemental questions following option picks
• Entering prompt mode codes
Use the mouse cursor to select the menu options.
The general operation of the graphics menu system is fully described in Module Operations (Ch. 17), but the options available specific to MPOD are all illustrated in the diagram below.
Figure 9‑32 The MPOD Graphics Menu System
The menu options all have corresponding prompt mode codes. They can be typed in the dialogue box (click in it to make it active).
The following lists explain the menu options and also give their corresponding prompt codes. Note that the lists do not cover all menu options because many of the standard options are fully explained elsewhere.
Also, note that some options do not appear at all times - for example the Show Set/Hide Set options do not appear if there is only one set.
.
Option
Command
Meaning
Main Menu options
Options
OP
Display the available prompt options.
New File
NE
Return to the file input screen
Replot
PL
Replot without change. PL is useful after many changes have been made to the plot with Redraw Off, or if the display has been corrupted in any way.
Display View and Axes options
Join
JO
Plot the data by joining the data values with a line
Points
PO
Plot the data point themselves, scatter plot
Join Points
JP
Plot points and join them
Lines
TO
Plot data by displaying radial lines to the values
XMIN = XX
 
Alter the scaling on the specified axis
XMAX = XX
 
The commands may be concatenated with commas
YMIN = YY
 
For example: YMAX = YY XMAX=500,XMIN=-300,YMIN=-500,YMAX=1000
Window R
WR
Pick two values on the Y-axis and plot all between them
Log R
LR
Replot with a logarithmic R-axis
Linear R
NR
Replot with a linear R-axis
Full X/Y
FX/FY
Redraw the plot to include the full X and Y axes
Zoom in
ZI
Zoom in 2 times on the centre of the plot
Zoom out
ZO
Zoom out 2 times on the centre of the plot
grid#
GR
Superimpose the plot on a grid
Box
TI
Graduate the axes with ticks
Zeros On/Off
ZON/ZOFF
Displays zero lines for the X and Y axes
Plot Type and Annotate Options
Note: The title string is stored within the extra details area of the data file for which the string is defined against the keyword GRPTITLE. This means that when the data are re-plotted once MPOD has exited, the title will remain intact.
Point Skip
SK
Plot every n'th point and skip the rest
Set Title
STI
Sets a title which will appear below the plot
Del Title
DTI
Deletes the title below the plot
Add Text
AT
Add text at the position of the mouse cursor
Move Text
MT
Move existing text
Del Text
DT
Delete a block of text
Preferences\ Legend On/Off
Note: These are mostly standard options. However, if between 1 and 6 sets are being plotted then Legend On/Off and Legend Text appears on the menu. It enables each data set to be given an editable label which be toggled on and off the plot.
Keyboard Options
Note: These are normally available when the cursor is selected by typing CU at the prompt when the cursor is over the plot, e.g. to draw a circle on the R-axis, press the R key, and a circle will be drawn through the cursor.
Display Value
V
Pick off a value. Equivalent to pressing the LEFT HAND mouse button
Define Window
W
Define a window. The window is rectangular and its left corner will be the position of the cursor when W is pressed, and the right corner the position of the cursor when the right mouse button is pressed
Save Pair Data
S
Save coordinate pair in the extra details area
Replot
P
Replots entire screen
Hardcopy
H
Hardcopy plot of entire screen including menu and dialogue box. The plot title will take the form PLn.PLT. Use PLTCON to convert it to formats such as HPGL (.HPS)
Draw Circle
R
Draws circle at R
Draw Angle
A
Draws an angle at θ
Quit
Q
Quit from cursor mode
Exit or return options
EX and #EX
Exit MPOD
MPOD Extra Details Keywords
User-Defined Titles
MPOD allows for the inclusion of a user-defined main title and subtitle within a particular plot. The main title appears at the top of the plot and the subtitle at the bottom. Both titles correspond to text strings which are stored in the extra details area of the data file being plotted. The keywords corresponding to each title are detailed below.
:
Extra Data Keyword
Text String Value
$TITLE
<Main Title Text String - top of plot>
GRPTITLE
<Sub-Title Test String - bottom of plot >
<KEYWORD>
<User defined keyword that corresponds to a data point picked off by the user.>
MPOD Batch Operation
MPOD runs in all the standard batch modes.
When run in batch mode MPOD will, by default, produce a hardcopy with the plot file taking on the next available name of the form plN.plt from the plot index.
If the /OPT=PL command is received in batch, MPOD will return to interactive mode and plot the data to the screen.
A list of MPOD’s batch keywords:
 
/INP
Input file name
/RMIN
Minimum on R-axis to display
/RMAX
Maximum on R-axis to display
/TYPE
Plot Type (Scatter/Join/Both)
/ONEIN
Plot 1 in value
/RSCAL
R-axis scaling (Linear/Log10)
/SETS
Data sets to display
/SHA
Whether to change shape between data sets
/OPT
Graphical plot options