Editing Finite Element Modelling (section)

====For Position Analysis Only====

Before we actually construct the bone and screw, we need to exit IPL (using .. as shown directly above) and find the positions and dimensions of the screw and bone. Below is how it is done:

<pre>
$!                          PART II : FINDING SCREW AND BONE DIMENSIONS AND POSITION
$! ---------------------------------------------------------------------------------------------------
$!
$   aix == "$UT:D3_IO_EXAMINE.EXE"
$   PIPE AIX 'sawbone_file' | SEARCH SYS$PIPE "!> Dim"| (READ SYS$INPUT LINE ; DEFINE/JOB LINE_LOG &LINE)
$   line_sym = f$trnlnm("line_log")
$   dimxbone = f$extract(37,3,line_sym)
$   dimybone = f$extract(45,3,line_sym)
$   dimzbone = f$extract(53,3,line_sym)
$   pipe aix 'screw_file' | search sys$pipe "!> Dim"| (read sys$input line ; define/job line_log &line)
$   line_sym = f$trnlnm("line_log")
$   dimxscrew = f$extract(38,2,line_sym)
$   dimyscrew = f$extract(46,2,line_sym)
$   dimzscrew = f$extract(53,3,line_sym)
$   xpos = dimxbone/2 - dimxscrew/2 + changex
$   ypos = dimybone/2 - dimyscrew/2
$   zpos = 60
$!
</pre>

AIX is a VMS command that shows the dimensions of a file. What this section does, is look for where "!> Dim" is in the AIX file and extract a certain number of characters starting at a certain character. For example, dimxbone takes 3 characters starting from the 37th character in that line.

Then the x-, y-, and z-positions are found by looking at the dimensions of the bone and placing the screw somewhere in the x-y plane and raising a bit in the z plane.

Now start up IPL again (using $ipl_batch).

*Use "read" to read in the screw file that was created earlier.
*Use "read" to read in the bone file that was created earlier.
*Use "header" to position the screw at (xpos, ypos, zpos).
*Use "header" to position the screw at (0, 0, 0).
*Use "write" to write the new screw variable to file.
*Use "copy" to make copy of the bone file you just read.
*Use "gobj" to mask the copy of the bone file with the new screw file you just wrote. This creates bone in the shape of the screw.
*Use "subtract" to subtract the screw-shaped bone from the original bone file you read in just above. This essentially creates a sample of bone that has a hole drilled in it. 
*Use "set" on the screw and the drilled bone to set the value of the screw and bone.
*Use "add" to add the screw to the drilled bone.
*Use "write" to write the construct to file.

Then close IPL and end the file, as shown in the previous section.


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