2 THE Z88 MODULES

2.1 THE DIRECT CHOLESKY SOLVER Z88F

NOTE:

Always compare FEA calculations with analytical rough calculations, results of experiments, plausibility considerations and other tests without exeption !

The principal task of every FEA program is the calculation of the displacements. That's the job of Z88F. The calculated deflections are the starting point for a stress calculation with Z88D or nodal force calculation with Z88E.

Z88F is the right solver for small to medium structures. For large structures launch the iteration solver Z88I1 and Z88I2.

For the displacement calculation the FE processor Z88F can be started in different modes. This is chosen in Z88F in the Mode menu. Compact Mode is provided as default.

Note: The files Z88I1.TXT and Z88I2.TXT mentioned here are described more precisely in chapter 3.

(1) Compact Mode

Windows: Z88F > Mode > Compact Mode, Compute > Go

UNIX: z88f -c (console) or Z88F with option Compact (Z88COM)

Input files:

Z88I1.TXT (general structure data)

Z88I2.TXT (boundary conditions, constraints)

Output files:

Z88O0.TXT (processed structure data for documentation)

Z88O1.TXT (processed boundary conditions for documentation)

Z88O2.TXT (deflections)

In addition two binary files Z88O1.BNY and Z88O3.BNY are generated. These binary files are later used by Z88D (stress processor) and Z88E (nodal force processor).

A third binary file Z88O2.BNY can be generated in addition which contains the total stiffness matrix. By ist use the same structure can be computed with different boundary conditions without a new formatting and compiling process. This is provided by (2) New Mode. Because this file Z88O2.BNY can get very large, the generation of it can be suppressed with the option (1) Compact Mode. Prefer Compact Mode if

> Only one set of boundary conditions should be processed

> Computing of big structures (disk space !)

Basically, Compact Mode can always be used !

The other two modes Z88F > Mode > New Mode and Z88F > Mode > Old Mode for Windows NT/95 and z88f -n and z88f -a for the UNIX operating systzem can save computing time for a structure with several sets of constraints.

(2) New Mode

Windows: Z88F > Mode > New Mode, Compute > Go

UNIX: z88f -n (console) or Z88F with option New (Z88COM)

Input files:

Z88I1.TXT (general structure data)

Z88I2.TXT (boundary conditions)

Output files:

Z88O0.TXT (processed structure data for documentation)

Z88O1.TXT (processed boundary conditions for documentation)

Z88O2.TXT (deflections)

In addition two binary files Z88O1.BNY and Z88O3.BNY are generated. These binary files are later used by Z88D (stress processor) and Z88E (nodal force processor).

A third binary file Z88O2.BNY is generated in addition which contains the total stiffness matrix. By ist use the same structure can be computed with different boundary conditions without a new formatting and compiling process. The Old Mode Z88F > Mode > Old Mode reads in Z88O2.BNY, see below.

Prefer Compact Mode if

> Several sets of boundary conditions should be processed

Keep in mind that big structures can cause huge Z88O2.BNY files. Also see Z88F > Mode > Old Mode.

(3) Old Mode

Windows: Z88F > Mode > Old Mode, Compute > Go

UNIX: z88f -a (console, yes, lowercase A) or Z88F with option Old

Input files:

Z88I2.TXT (boundary conditions)

(Z88O2.BNY, was produced by a previous run Z88F > Mode > New Mode or z88f -n)

Output files:

Z88O1.TXT (processed boundary conditions for documentation)

Z88O2.TXT (deflections)

In addition the binary file Z88O3.BNY is filed. This binary file used by Z88D (stress processor) and Z88E (nodal force processor).

Z88F reads Z88O2.BNY containing the total stiffness matrix and the boundary conditions from Z88I2.TXT and solves the system of equations. The formatting and compiling process is skipped so that a given structure with different sets of constraints can be computed more quickly than with multiple runs of Z88F > Mode > Compact Mode (z88f -c for UNIX). This Mode can be used only if Z88F > Mode > New Mode (z88f -n for UNIX) was run before.

Example:

General structure data Z88I1.TXT and

- 1st set of boundary conditions in Z88I2.TXT, Z88F > Mode > New Mode

- 2nd set of boundary conditions in Z88I2.TXT, Z88F > Mode > Old Mode

- (more sets of boundary conditions, Z88F > Mode > Old Mode)

- Last set of boundary conditions in Z88I2.TXT, Z88F > Mode > Old Mode

Modify the contents of Z88I2.TXT between the Z88F runs. Z88I2.TXT cannot maintain more than one set of constraints.

(4) Test Mode

Windows: Z88F > Mode > Test Mode, Compute > Go

UNIX: z88f -t (console) or Z88F with option Test (Z88COM)

Input files:

Z88I1.TXT (general structure data)

Output files:

Z88O0.TXT (processed structure data for documentation)

Only the file Z88O0.TXT (processed structure data for documentation) is produced along with the memory needs for total stiffness matrix and coincidence vector plotted on the screen. Use this mode for

> Checking the memory needs for MAXGS and MAXKOI.

> Checking if Z88F interprets Z88I1.TXT correctly and, as requested, puts the data in Z88O0.TXT.