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What is PyMAPDL?#
PyMAPDL is the pythonic interface for Ansys MAPDL product. What does this mean? It means that you can call Ansys MAPDL functionalities (Solvers, Post processing tools, etc) using Python programming language. MAPDL provides many tools and features which would require A LOT of time to explain, so let’s have a quick overview. Launching PyMAPDL#But first, let’s launch PyMAPDL. from ansys.mapdl.core import launch_mapdl mapdl = launch_mapdl() print(mapdl) Product: Ansys Mechanical Enterprise MAPDL Version: 22.2 ansys.mapdl Version: 0.63.2 Geometry#PyMAPDL support points (keypoints), lines, areas, and volumes for geometry definition. You can plot an area using keypoints: mapdl.prep7() # entering in preprocessor for geometry generation k0 = mapdl.k("", 0, 0, 0) k1 = mapdl.k("", 1, 0, 0) k2 = mapdl.k("", 0, 1, 0) a0 = mapdl.a(k0, k1, k2) mapdl.aplot(show_lines=True, line_width=5, show_bounds=True, cpos="xy")Create a simple cube volume. mapdl.clear() # let's clear first. mapdl.prep7() # entering in preprocessor k0 = mapdl.k("", 0, 0, 0) # defining a keypoint at (0,0,0) location k1 = mapdl.k("", 1, 0, 0) # defining a keypoint at (1,0,0) location k2 = mapdl.k("", 1, 1, 0) # etc k3 = mapdl.k("", 0, 1, 0) k4 = mapdl.k("", 0, 0, 1) k5 = mapdl.k("", 1, 0, 1) k6 = mapdl.k("", 1, 1, 1) k7 = mapdl.k("", 0, 1, 1) # defining volume according the kps v0 = mapdl.v(k0, k1, k2, k3, k4, k5, k6, k7) mapdl.vplot(show_lines=True) Material definition#You can define materials using the following commands: # Define a material (nominal steel in SI) mapdl.mp("EX", 1, 210e9) # Elastic moduli in Pa (kg/(m*s**2)) mapdl.mp("DENS", 1, 7800) # Density in kg/m3 mapdl.mp("NUXY", 1, 0.3) # Poisson's Ratio MATERIAL 1 NUXY = 0.3000000At any point you can use help to get information about each function help(mapdl.mp) Help on method mp in module ansys.mapdl.core._commands.preproc.materials: mp(lab='', mat='', c0='', c1='', c2='', c3='', c4='', **kwargs) method of ansys.mapdl.core.mapdl_grpc.MapdlGrpc instance APDL Command: MP Defines a linear material property as a constant or a function of temperature. Parameters ---------- lab Valid material property label. Applicable labels are listed under "Material Properties" in the input table for each element type in the Element Reference. See Linear Material Properties in the Material Reference for more complete property label definitions: ALPD Mass matrix multiplier for damping. ALPX Secant coefficients of thermal expansion (also ``ALPY``, ``ALPZ``). BETD Stiffness matrix multiplier for damping. .. note:: If used in an explicit dynamic analysis, the value corresponds to the percentage of damping in the high frequency domain. For example, 0.1 roughly corresponds to 10% damping in the high frequency domain. BETX Coefficient of diffusion expansion (also ``BETY``, ``BETZ``) BVIS Bulk viscosity C Specific heat CREF Reference concentration (may not be temperature dependent) CSAT Saturated concentration CTEX Instantaneous coefficients of thermal expansion (also ``CTEY``, ``CTEZ``) CVH Heat coefficient at constant volume per unit of mass DENS Mass density. DMPR Constant structural damping coefficient in full harmonic analysis or damping ratio in mode-superposition analysis. DXX Diffusivity coefficients (also ``DYY``, ``DZZ``) EMIS Emissivity. ENTH Enthalpy. EX Elastic moduli (also ``EY``, ``EZ``) GXY Shear moduli (also ``GYZ``, ``GXZ``) HF Convection or film coefficient KXX Thermal conductivities (also ``KYY``, ``KZZ``) LSST Electric loss tangent LSSM Magnetic loss tangent MGXX Magnetic coercive forces (also ``MGYY``, ``MGZZ``) MURX Magnetic relative permeabilities (also ``MURY``, ``MURZ``) MU Coefficient of friction NUXY Minor Poisson's ratios (also ``NUYZ``, ``NUXZ``) (``NUXY`` = νyx, as described in Stress-Strain Relationships in the Mechanical APDL Theory Reference) PERX Electric relative permittivities (also ``PERY``, ``PERZ``) .. note:: If you enter permittivity values less than 1 for ``SOLID5``, ``PLANE13``, or ``SOLID98``, the program interprets the values as absolute permittivity. Values input for ``PLANE223``, ``SOLID226``, or ``SOLID227`` are always interpreted as relative permittivity. PRXY Major Poisson's ratios (also ``PRYZ``, ``PRXZ``) (``PRXY`` = νxy, as described in Stress- Strain Relationships in the Mechanical APDL Theory Reference) QRATE Heat generation rate for thermal mass element MASS71. Fraction of plastic work converted to heat (Taylor-Quinney coefficient) for coupled- field elements ``PLANE223``, ``SOLID226``, and ``SOLID227``. REFT Reference temperature. Must be defined as a constant; ``C1`` through ``C4`` are ignored. RH Hall Coefficient. RSVX Electrical resistivities (also ``RSVY``, ``RSVZ``). SBKX Seebeck coefficients (also ``SBKY``, ``SBKZ``). SONC Sonic velocity. THSX Thermal strain (also ``THSY``, ``THSZ``). VISC Viscosity. mat Material reference number to be associated with the elements (defaults to the current MAT setting [MAT]). c0 Material property value, or if a property-versus-temperature polynomial is being defined, the constant term in the polynomial. ``C0`` can also be a table name (``%tabname%``); if ``C0`` is a table name, ``C1`` through ``C4`` are ignored. c1, c2, c3, c4 Coefficients of the linear, quadratic, cubic, and quartic terms, respectively, in the property-versus-temperature polynomial. Leave blank (or set to zero) for a constant material property. Notes ----- MP defines a linear material property as a constant or in terms of a fourth order polynomial as a function of temperature. (See the TB command for nonlinear material property input.) Linear material properties typically require a single substep for solution, whereas nonlinear material properties require multiple substeps; see Linear Material Properties in the Material Reference for details. If the constants ``C1`` - ``C4`` are input, the polynomial .. math:: Property = C_0 + C_1(T) + C_2(T)^2 + C_3(T)^3 + C_4(T)^4 is evaluated at discrete temperature points with linear interpolation between points (that is, a piecewise linear representation) and a constant-valued extrapolation beyond the extreme points. First-order properties use two discrete points (±9999°). The :meth:`MPTEMP ` or :meth:`MPTGEN ` commands must be used for second and higher order properties to define appropriate temperature steps. To ensure that the number of temperatures defined via the :meth:`MPTEMP ` and :meth:`MPTGEN ` commands is minimally sufficient for a reasonable representation of the curve, ANSYS generates an error message if the number is less than ``N``, and a warning message if the number is less than ``2N``. The value ``N`` represents the highest coefficient used; for example, if ``C3`` is nonzero and ``C4`` is zero, a cubic curve is being used which is defined using 4 coefficients so that ``N`` = 4.Or you can check the online help at mapdl.docs.pyansys.com Element definition#Since MAPDL is a finite element solver, the type of element needs to be defined. Ansys has an Element Guide which contain all the necessary information mapdl.et(1, "SOLID186") 1SOLID186 is a 3D hexahedron element, suitable for any structural 3D analysis. There are also KEYOPTS which allow us to configure the elements. Also there is the constant sets R which helps us to set the analysis and element configurations. Meshing#Meshing is quite easy, once the element and material are defined. mapdl.esize(1 / 10) # Element size mapdl.vmesh(v0) GENERATE NODES AND ELEMENTS IN VOLUMES 1 TO 1 IN STEPS OF 1 NUMBER OF VOLUMES MESHED = 1 MAXIMUM NODE NUMBER = 4961 MAXIMUM ELEMENT NUMBER = 1000Let’s see the result mapdl.eplot() # plot elements Boundary conditions#There are many boundary conditions options, and most of them are applied using mapdl.d (for displacement) or mapdl.f (for force). Let’s setup this example to represent a compression test. For that purpose, we need to fix the box bottom surface to have zero displacement. But first, we need to select the corresponding nodes using the mapdl.nsel command: help(mapdl.nsel) Help on method nsel in module ansys.mapdl.core._commands.database.selecting: nsel(type_='', item='', comp='', vmin='', vmax='', vinc='', kabs='', **kwargs) method of ansys.mapdl.core.mapdl_grpc.MapdlGrpc instance Selects a subset of nodes. APDL Command: NSEL Parameters ---------- type\_ Label identifying the type of select: S - Select a new set (default). R - Reselect a set from the current set. A - Additionally select a set and extend the current set. U - Unselect a set from the current set. ALL - Restore the full set. NONE - Unselect the full set. INVE - Invert the current set (selected becomes unselected and vice versa). STAT - Display the current select status. The following fields are used only with Type = S, R, A, or U: Item Label identifying data. Valid item labels are shown in the table below. Some items also require a component label. If Item = PICK (or simply "P"), graphical picking is enabled and all remaining command fields are ignored (valid only in the GUI). Defaults to NODE. Comp Component of the item (if required). Valid component labels are shown in the table below. VMIN Minimum value of item range. Ranges are node numbers, set numbers, coordinate values, load values, or result values as appropriate for the item. A component name (as specified on the CM (p. 338) command) may also be substituted for VMIN (VMAX and VINC are ignored). VMAX Maximum value of item range. VMAX defaults to VMIN for input values. For result values, VMAX defaults to infinity if VMIN is positive, or to zero if VMIN is negative. VINC Value increment within range. Used only with integer ranges (such as for node and set numbers). Defaults to 1. VINC cannot be negative. KABS Absolute value key: - `kabs = 0` - Check sign of value during selection. - `kabs = 1` - Use absolute value during selection (sign ignored) Notes ----- Selects a subset of nodes. For example, to select a new set of nodes based on node numbers 1 through 7, do >>> mapdl.nsel('S','NODE','',1,7) The subset is used when the `'ALL'` label is entered (or implied) on other commands, such as >>> mapdl.nlist('ALL') Only data identified by node number are selected. Data are flagged as selected and unselected; no data are actually deleted from the database. When selecting nodes by results, the full graphics value is used, regardless of whether PowerGraphics is on. Solution result data consists of two types, 1) nodal degree of freedom --results initially calculated at the nodes (such as displacement, temperature, pressure, etc.), and 2) element--results initially calculated elsewhere (such as at an element integration point or thickness location) and then recalculated at the nodes (such as stresses, strains, etc.). Various element results also depend upon the recalculation method and the selected results location [AVPRIN, RSYS, FORCE, LAYER and SHELL]. You must have all the nodes (corner and midside nodes) on the external face of the element selected to use Item = EXT. This command is valid in any processor. For Selects based on non-integer numbers (coordinates, results, etc.), items that are within the range VMIN-Toler and VMAX+Toler are selected. The default tolerance Toler is based on the relative values of VMIN and VMAX as follows: If VMIN = VMAX, Toler = 0.005 x VMIN. If VMIN = VMAX = 0.0, Toler = 1.0E-6. If VMAX ≠ VMIN, Toler = 1.0E-8 x (VMAX-VMIN). Use the SELTOL command to override this default and specify Toler explicitly. Table: 208:: : NSEL - Valid Item and Component Labels Table: 209:: : NSEL - Valid Item and Component Labels for Nodal DOF Result Values Examples -------- Select nodes at `x == 0`, Of these, reselect nodes between ``1 < Y < 10``, then finally unselect nodes between ``5 < Y < 6``. >>> mapdl.nsel('S', 'LOC', 'X', 0) >>> mapdl.nsel('R', 'LOC', 'Y', 1, 10) >>> mapdl.nsel('U', 'LOC', 'Y', 5, 6) For other coordinate systems activate the coord system first. First, change to cylindrical coordinate system, select nodes at ``radius == 5``. Reselect nodes from 0 to 90 degrees. >>> mapdl.csys(1) >>> mapdl.nsel('S', 'LOC', 'X', 5) >>> mapdl.nsel('R', 'LOC', 'Y', 0, 90) Note that the labels X, Y, and Z are always used, regardless of which coordinate system is activated. They take on different meanings in different systems Additionally, angles are always in degrees and NOT radians. Select elements assigned to material property 2 >>> mapdl.esel('S', 'MAT', '', 2) Select the nodes these elements use >>> mapdl.nsle() Reselect nodes on the element external surfaces >>> mapdl.nsel('R', 'EXT') Change to cylindrical coordinates >>> mapdl.csys(1) Reselect nodes with radius=5 >>> mapdl.nsel('R', 'LOC', 'X', 5) mapdl.nsel("S", "loc", "z", 0) mapdl.nplot() # check the selectionApplying to all selected nodes, displacement in Z direction equals to zero. mapdl.d("all", "UZ", 0) # Let's check the result mapdl.nplot(plot_bc=True)Let’s apply the rest of the boundary conditions. # Let's fix the box edge XZ to not move except along Y. mapdl.nsel("s", "loc", "z", 0) # "r" is to reselect the nodes, from the previous "S" selection mapdl.nsel("r", "loc", "x", 0) mapdl.d("all", "UZ", 0) mapdl.d("all", "UX", 0) # we will do the same with the line YZ, but not move along X direction. mapdl.nsel("s", "loc", "z", 0) mapdl.nsel("r", "loc", "Y", 0) mapdl.d("all", "UZ", 0) mapdl.d("all", "UY", 0) SPECIFIED CONSTRAINT UY FOR SELECTED NODES 1 TO 4961 BY 1 REAL= 0.00000000 IMAG= 0.00000000Finally let’s fix one node in the directions: mapdl.nsel("s", "loc", "x", 0) mapdl.nsel("r", "loc", "y", 0) mapdl.nsel("r", "loc", "z", 0) mapdl.d("all", "all", 0) # this code is redundant, because the nodal displacements do not overwrite each other # if they are not in the same direction. # This node was included in the previous lines selections, hence its # boundary conditions are already defined. SPECIFIED CONSTRAINT UX FOR SELECTED NODES 1 TO 4961 BY 1 REAL= 0.00000000 IMAG= 0.00000000 ADDITIONAL DOFS= UY UZLet’s check the final result mapdl.nsel("s", "loc", "z", 0) mapdl.nplot(plot_bc=True)Now let’s apply a displacement at the box top at each node. We could apply a force instead if we wish. mapdl.nsel("s", "loc", "z", 1) # mapdl.f("all", "FZ", 1E9) mapdl.d("all", "UZ", 0.01) SPECIFIED CONSTRAINT UZ FOR SELECTED NODES 1 TO 4961 BY 1 REAL= 1.000000000E-02 IMAG= 0.00000000 Analysis setup#Let’s do a simple static analysis mapdl.slashsolu() mapdl.allsel() # making sure all nodes and elements are selected. mapdl.antype("STATIC") output = mapdl.solve() print(output) ***** MAPDL SOLVE COMMAND ***** *** NOTE *** CP = 1.569 TIME= 10:48:46 There is no title defined for this analysis. *** SELECTION OF ELEMENT TECHNOLOGIES FOR APPLICABLE ELEMENTS *** ---GIVE SUGGESTIONS ONLY--- ELEMENT TYPE 1 IS SOLID186. KEYOPT(2) IS ALREADY SET AS SUGGESTED. *** MAPDL - ENGINEERING ANALYSIS SYSTEM RELEASE 22.2 *** Ansys Mechanical Enterprise 00000000 VERSION=LINUX x64 10:48:46 OCT 03, 2022 CP= 1.582 S O L U T I O N O P T I O N S PROBLEM DIMENSIONALITY. . . . . . . . . . . . .3-D DEGREES OF FREEDOM. . . . . . UX UY UZ ANALYSIS TYPE . . . . . . . . . . . . . . . . .STATIC (STEADY-STATE) GLOBALLY ASSEMBLED MATRIX . . . . . . . . . . .SYMMETRIC *** NOTE *** CP = 1.586 TIME= 10:48:46 Present time 0 is less than or equal to the previous time. Time will default to 1. *** NOTE *** CP = 1.590 TIME= 10:48:46 The conditions for direct assembly have been met. No .emat or .erot files will be produced. L O A D S T E P O P T I O N S LOAD STEP NUMBER. . . . . . . . . . . . . . . . 1 TIME AT END OF THE LOAD STEP. . . . . . . . . . 1.0000 NUMBER OF SUBSTEPS. . . . . . . . . . . . . . . 1 STEP CHANGE BOUNDARY CONDITIONS . . . . . . . . NO PRINT OUTPUT CONTROLS . . . . . . . . . . . . .NO PRINTOUT DATABASE OUTPUT CONTROLS. . . . . . . . . . . .ALL DATA WRITTEN FOR THE LAST SUBSTEP SOLUTION MONITORING INFO IS WRITTEN TO FILE= file.mntr *********** PRECISE MASS SUMMARY *********** TOTAL RIGID BODY MASS MATRIX ABOUT ORIGIN Translational mass | Coupled translational/rotational mass 7800.0 0.0000 0.0000 | 0.0000 3900.0 -3900.0 0.0000 7800.0 0.0000 | -3900.0 0.0000 3900.0 0.0000 0.0000 7800.0 | 3900.0 -3900.0 0.0000 ------------------------------------------ | ------------------------------------------ | Rotational mass (inertia) | 5200.0 -1950.0 -1950.0 | -1950.0 5200.0 -1950.0 | -1950.0 -1950.0 5200.0 TOTAL MASS = 7800.0 The mass principal axes coincide with the global Cartesian axes CENTER OF MASS (X,Y,Z)= 0.50000 0.50000 0.50000 TOTAL INERTIA ABOUT CENTER OF MASS 1300.0 -0.41069E-11 -0.16058E-11 -0.41069E-11 1300.0 -0.72902E-11 -0.16058E-11 -0.72902E-11 1300.0 The inertia principal axes coincide with the global Cartesian axes *** MASS SUMMARY BY ELEMENT TYPE *** TYPE MASS 1 7800.00 Range of element maximum matrix coefficients in global coordinates Maximum = 1.914529915E+10 at element 247. Minimum = 1.914529915E+10 at element 556. *** ELEMENT MATRIX FORMULATION TIMES TYPE NUMBER ENAME TOTAL CP AVE CP 1 1000 SOLID186 0.303 0.000303 Time at end of element matrix formulation CP = 1.86823082. SPARSE MATRIX DIRECT SOLVER. Number of equations = 14159, Maximum wavefront = 225 Memory allocated for solver = 113.349 MB Memory required for in-core solution = 108.776 MB Memory required for out-of-core solution = 44.000 MB *** NOTE *** CP = 2.170 TIME= 10:48:46 The Sparse Matrix Solver is currently running in the in-core memory mode. This memory mode uses the most amount of memory in order to avoid using the hard drive as much as possible, which most often results in the fastest solution time. This mode is recommended if enough physical memory is present to accommodate all of the solver data. Sparse solver maximum pivot= 7.658119658E+10 at node 4420 UY. Sparse solver minimum pivot= 4.423964031E+09 at node 672 UZ. Sparse solver minimum pivot in absolute value= 4.423964031E+09 at node 672 UZ. *** ELEMENT RESULT CALCULATION TIMES TYPE NUMBER ENAME TOTAL CP AVE CP 1 1000 SOLID186 0.225 0.000225 *** NODAL LOAD CALCULATION TIMES TYPE NUMBER ENAME TOTAL CP AVE CP 1 1000 SOLID186 0.045 0.000045 *** LOAD STEP 1 SUBSTEP 1 COMPLETED. CUM ITER = 1 *** TIME = 1.00000 TIME INC = 1.00000 NEW TRIANG MATRIX *** MAPDL BINARY FILE STATISTICS BUFFER SIZE USED= 16384 10.250 MB WRITTEN ON ASSEMBLED MATRIX FILE: file.full 1.750 MB WRITTEN ON RESULTS FILE: file.rst Post-Processing#Let’s what we got. Let’s see the displacements: mapdl.post_processing.nodal_displacement("all") array([[ 0. , 0. , 0. ], [-0.003 , 0. , 0. ], [-0.00015, 0. , 0. ], ..., [-0.00285, -0.0027 , 0.007 ], [-0.00285, -0.0027 , 0.008 ], [-0.00285, -0.0027 , 0.009 ]])Let’s plot them mapdl.post_processing.plot_nodal_displacement("Z")We can store the displacements as an array and use them for our calculations. For example: nodal_disp = mapdl.post_processing.nodal_displacement("all") print(f"The maximum displacement is {nodal_disp.max():0.3f}") The maximum displacement is 0.010Oh! By the way, you can format strings in this way, they are very powerful. This type of string is called f-string. The 0.3f after the colon (:) is the format for the number. # First column is X displacement print(f"The maximum X displacement is {nodal_disp[:, 0].max():0.3f}") print(f"The average Z displacement is {nodal_disp[:, 2].mean():0.3f}") The maximum X displacement is 0.000 The average Z displacement is 0.005 Closing session#This is all for today. We hope you enjoyed this talk, as much as we enjoyed preparing it! Closing PyMAPDL session mapdl.exit()Total running time of the script: ( 0 minutes 6.266 seconds) Download Python source code: 01-pymapdl.py Download Jupyter notebook: 01-pymapdl.ipynb Gallery generated by Sphinx-Gallery |
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