About
MYSTRAN
MYSTRAN is a general purpose finite
element analysis computer program for structures that can be modeled
as linear (i.e. displacements, forces and stresses proportional to
applied load). MYSTRAN is an acronym for “My Structural
Analysis”, to indicate it’s usefulness in solving a wide variety
of finite element analysis problems on a personal computer (although
there is no reason that it could not be used on mainframe computers
as well). For anyone familiar with the popular NASTRAN
computer program developed by NASA (National Aeronautics and Space
Administration) in the 1970’s and popularized in several commercial
versions since, the input to MYSTRAN will look quite familiar.
Indeed, many structural analyses modeled for execution in NASTRAN
will execute in MYSTRAN with little, or no, modification. MYSTRAN, however, is not NASTRAN. All of the finite
element processing to obtain the global stiffness matrix (including the finite element matrix generation
routines themselves), the reduction of the stiffness matrix to the
solution set, as well as all of the input/output routines are written
in independent, modern, Fortran 90/95 code.
The major solution algorithms (e.g., triangular decomposition
of matrices and forward/backward substitution to obtain solutions
of linear equations and Lanczos eigenvalues extraction code), however, were obtained from the popular LAPACK and ARPACK
codes available to the general public on the World Wide Web at the following links:
LAPACK
ARPACK
The code for the grid point sequencing algorithm, BANDIT
(used to insure a minimum bandwidth for the stiffness matrix)
was obtained from the author of Reference 3 in the MYSTRAN Users Reference Manual
There is no inherent limitation to problem
size, or number of degrees of freedom, for the version of MYSTRAN
distributed as “Unlimited Size”. Rather,
the users’ personal computer memory (RAM and disk) limitations and Windows virtual memory page file size limitations will
dictate what size problems can be effectively solved using MYSTRAN
on their computer.
Major features of the program are:
·
3D structures with arbitrary geometry.
·
Linear static analysis.
·
Eigenvalue analysis via Lanczos, Givens and modified Givens methods.
In addition, for the fundamental mode there is also an Inverse Power method
·
Optional calculation of modal mass and/or modal participation factors
·
CraigBampton model generation and synthesis into overall model
·
Interface to the popular FEMAP pre/post processing program.
·
Grid points that define the finite element model mesh:
·
Locations can be defined in rectangular, cylindrical
or spherical coordinate systems that can be different for each grid
·
Global stiffness matrix can be formulated in
rectangular, cylindrical or spherical coordinate systems that can
be different for each grid
·
Six degrees of freedom (three translations and
three rotations) per grid.
·
Scalar points (SPOINT) that have no defined geometry (one degree of freedom).
·
A finite element library consisting of the following
elastic and rigid elements.
Elastic
Elements:
·
1D elements:
·
BAR element with two grids and stiffness for up to six degrees of freedom per grid
(axial, two planes of bending, torsion) for beams that have their shear center and elastic axis coincident
·
ROD element (axial load and torsion element connected to two grid points)
·
2D Triangular and quadrilateral plate elements (properties defined on PSHELL entries)
for thick (Mindlin plate theory) and thin (Kirchoff plate theory) plates:
·
QUAD4 quadrilateral plate element with plate
membrane and bending stiffness, as well as transverse shear flexibility,
based on Mindlin thick plate theory.
·
TRIA3 flat triangular plate element with plate
membrane and bending stiffness, as well as transverse shear flexibility,
based on Mindlin thick plate theory
·
QUAD4K quadrilateral plate element with plate
membrane and bending stiffness based on Kirchoff
thin plate theory.
·
TRIA3K flat triangular plate element with plate
membrane and bending stiffness based on Kirchoff
thin plate theory
·
2D Triangular and quadrilateral composite plate elements (properties defined on PCOMP entry for each ply)
·
QUAD4 quadrilateral plate element.
·
TRIA3 flat triangular plate element.
·
3D solid elements:
·
HEXA 8 and 20 node hexagonal (brick) elements
·
PENTA 6 and 15 node pentagonal elements
·
TETRA 4 and 10 node tetrahedron elements
·
User defined elements:
·
CUSERIN element where the user inputs the stiffness and mass matrices and specifies the connection of the element to defined grids and scalar points
·
Scalar elements:
·
CELAS1,2,3,4 elements connecting two degrees of freedom (either GRID's or SPOINT's)
·
CMASS1,2,3,4 mass elements at GRID's or SPOINT's
Relements:
·
RBE2 rigid element specifying a relationship
for one or more degrees of freedom (DOF's) of one or more grids being
rigidly dependent on the DOF's of another grid.
·
RBE3 element for distributing loads or mass from one grid to other grids.
·
Single point constraints (SPC’s)
wherein some degrees of freedom are grounded (e.g. for specifying
boundary conditions).
·
Other SPC’s wherein
specified degrees of freedom have a specified motion (enforced displacements).
·
Multi point constraints (MPC’s),
wherein specified degrees of freedom are linearly dependent on other
degrees of freedom.
·
Loads on the finite element model via:
·
Forces and/or moments applied directly to grid
points
·
Pressure loading on plate element surfaces
·
Gravity loads on the whole model (in conjunction
with mass defined by the user)
·
Equivalent loads due to thermal expansion
·
Equivalent loads due to enforced displacements
·
Inertia loads due to rigid body angular velocity and acceleration about some specified grid (RFORCE)
·
Loads on scalar SPOINT's (via SLOAD)
·
Linear isotropic, orthotropic and anisotropic material properties.
·
Mass defined via:
·
Density on material entries
·
Mass per unit length, or per unit area, for
finite elements
·
Concentrated masses at grids (CONM2) with optional
offsets and moments of inertia.
·
Scalar masses (CMASS1,2,3,4).
·
Calculation of rigid body mass properties of the model (PARAM GRDPNT).
·
Multiple subcases to allow for solution for more than one loading condition in one execution.
·
Output of the following quantities for any user defined set of grids or elements:
·
Displacements
·
Applied loads
·
Single point forces of constraint
·
Multi point forces of constraint (includes forces of constraint due to MPC's as well as rigid elements)
·
Grid point force balance
·
Element engineering and/or nodal forces
·
Element stresses (including ply stresses in composite elements)
·
Element strains for 2D and 3D elements (including ply strains in composite elements)
·
Effective modal mass and/or modal participation factors in eigenvalue analyses
·
Output transformation matrices (OTM's) in CraigBampton analyses for displacement, acceleration, force, and stress quantities
·
Guyan reduction to
statically reduce the stiffness and mass matrices. This is needed for the Givens method of analyses to remove degrees of freedom that have no mass.
·
Limited CHKPNT/RESTART feature that allows a previous job to be restarted
to obtain new or different outputs (displacements, etc).
The finite element model and solution (SOL in Exec Control) must remain the same
·
General:
·
AUTOSPC (automatic SPC generation based on user control)
·
Stiffness matrix equilibrium checks on request (Bulk Data PARAM entry EQCHECK)
·
Automatic grid point resequencing to reduce matrix bandwidth
(Bulk Data PARAM entry GRIDSEQ with value BANDIT  default)
