2.3. MaterialPointSimulator

See Also

Overview

A model in Matmodlab is defined by a MaterialPointSimulator object. The MaterialPointSimulator object manages and allocates memory for materials and analysis steps. In this section, the MaterialPointSimulator object is described.

The MaterialPointSimulator Constructor

class MaterialPointSimulator(job, verbosity=1, d=None, inital_temperature=DEFAULT_TEMP, output=DBX)

Create a MaterialPointSimulator object and set up the simulation.

The job string is the simulation ID. Generated files are named job.ext, where ext is the file extension.

The following arguments are optional.

The verbosity integer set the simulation verbosity. Generally, 0=quiet, 2=noisy. The d string is the simulation directory, the default is the working directory. initial_temperature is the initial temperature, the default is 298 K. The output symbolic constant specifies the output type, it defaults to DBX if not specified. See Matmodlab File Formats for a description of supported output formats.

Examples:

>>> mps = MaterialPointSimulator('model')

>>> mps = MaterialPointSimulator('model', verbosity=2, d='/home/user/sim')

Defining a Material Model

MaterialPointSimulator.Material(model, parameters, name=None, switch=None, rebuild=False, source_files=None, depvar=None, fiber_dirs=None, user_ics=False, order=None, response=None, libname=None, param_names=None)

Create and assign a material model

The required arguments are a model name and material parameters. The model name must be a recognized material model (see Materials). parameters is either a dictionary of key:value (key being the parameter name, value its numeric value) or ndarray.

The following arguments are optional and applicable to all materials.

rebuild is a boolean that, when True, forces the material model to be rebuilt before the simulation. switch is a tuple containing the material name and the name of another material to be switched in to its place.

The following arguments are applicable to user materials:

A user material is invoked by setting model to one of USER, UMAT, UHYPER, UANISOHYPER_INV (see User Defined Materials for details).

source_files is a list of model source files. Each file must exist and be readable on the file system. depvar is either the integer number of state dependent variables or a list of state dependent variable names. fiber_dirs is an array of fiber directions (applicable only to uanisohyper_inv models). param_names is a list of parameter names. If user_ics is True, Matmodlab calls the user supplied SDVINI subroutine to initialize state dependent variables - otherwise they are set to 0. order is a list of strings specifying the component ordering of second order tensors. response is one of MECHANICAL, HYPERELASTIC, or ANISOHYPER and is used to determine which type of response the model will describe.

Examples:

>>> mps.Material('elastic', {'K': 123e9, 'G': 53e9})

>>> mps.Material(UMAT, (10e6, .333, 42e3),
                 source_files=('umat.f', 'umat.pyf'),
                 param_names=('E', 'nu', 'Y'), user_ics=True,
                 depvar=('EQPS',))

Optional Material Addons

Thermal Expansion

A Thermal Expansion object, enabling the computation of thermal strains associated with thermal expansion.

Viscoelasticity

A Viscoelasticity object defining the linear relaxation response of the material. When given, the elastic moduli are treated as the instantaneous values.

Time-Temperature Shift

Used in conjuction with a Viscoelasticity to compute a reduced time.

Defining Simulation Steps

The recommended way to create simulation steps is to use the following convenience functions.

MaterialPointSimulator.StrainStep(*)

All step components are interpreted as components of the strain tensor.

The arguments represented by the * are common to all other step methods and are described in Common Step Arguments.

MaterialPointSimulator.StrainRateStep(*)

All step components are interpreted as components of the strain rate tensor.

The arguments represented by the * are common to all other step methods and are described in Common Step Arguments.

MaterialPointSimulator.StressStep(*)

All step components are interpreted as components of the stress tensor.

The arguments represented by the * are common to all other step methods and are described in Common Step Arguments.

Note

kappa is set to 0 for stress steps

MaterialPointSimulator.StressRateStep(*)

All step components are interpreted as components of the stress rate tensor.

The arguments represented by the * are common to all other step methods and are described in Common Step Arguments.

Note

kappa is set to 0 for stress rate steps

MaterialPointSimulator.DisplacementStep(*)

All step components are interpreted as components of the displacement vector, applied only to the “+” faces of a unit cube centered at the coordinate origin.

The arguments represented by the * are common to all other step methods and are described in Common Step Arguments.

MaterialPointSimulator.DefGradStep(*)

All step components are interpreted as components of the deformation gradient tensor.

MaterialPointSimulator.DataSteps(filename, tc=0, columns=None, descriptors=None, skiprows=0, comments='#', sheet=None, *)

Generate steps from a data file.

filename is the name of a file containing the data. tc is the integer index of the column containing time. columns are the indices of the columns containing data. If not given, columns is taken to be the first six columns of the file, that are not tc.

skiprows is the integer number of rows to skip before reading data, comments is the comment delimiter. sheet is the sheet from which to read data, if filename is an excel file.

The ith descriptor designates the physical interpretation of the ith. descriptors must be one of 'E' (strain), 'D' (strain rate), 'S' (stress), 'R' (stress rate), 'P' (electric field), 'T' (temperature).

The arguments represented by the * are common to all other step methods and are described in Common Step Arguments.

MaterialPointSimulator.MixedStep(descriptors=None, *)

All step components are interpreted as components of stress and/or strain.

The ith descriptor designates the physical interpretation of the ith. descriptors must be one of 'E' or 'S' with 'E' representing strain and 'S' representing stress.

The arguments represented by the * are common to all other step methods and are described in Common Step Arguments.

Common Step Arguments

The arguments common to all step functions are:

components are the components of the tensor defining the step. Tensor ordering is described in Conventions. For all tensors, the components are assumed to be the “tensor values”, as opposed to the “engineering values”. For symmetric tensors, specifying only the three diagonal components implicitly assigns the off-diagonal components a value of zero. For strain type tensors, if only a single component is given, it is assumed to be a volumetric deformation. For stress type tensors, if only a single component is given, it is assumed to be a pressure.

scale is a multiplier applied to all components. It can be a float or a numpy ndarray (so that a different scale could be applied to each component separately).

frames is the integer number of increments that the step is subdivided in to.

kappa the Seth-Hill strain parameter. See The Strain Tensor for details.

temperature is the temperature. If not specified, the step is assigned the same temperature as the previous step.

elec_field is the electric field vector. If none is given, it is set to (0, 0, 0).

num_dumps is the integer number of times to write the output database. If not specified, all step increments are written.

Running the Simulation

MaterialPointSimulator.run(termination_time=None)

Run the simulation

termination_time is the termination time. If not given, the final time from the last step is used.

Extracting Results from the Output Database

MaterialPointSimulator.get(*variables, model=None, disp=0)

Get variables from output database.

variables is a list of variables to extract. If disp is 1, the variables are returned, in addition to a header describing the variables.

Viewing Simulation Results

MaterialPointSimulator.view(model=None)

Display simulation results in visualizer.

Exporting Results to Other Formats

MaterialPointSimulator.dump(variables, model=None, format='ascii', ffmt='%.18f')

Writes simulation results for the requested variables to the requested format.

variables is a list of variables to extract from the database and are written the MaterialPointSimulator.job.ext, where ext is a file extension that depends on the requested output format.