This section describes the options available for the mapping of material properties for *MAT ANISOTROPIC_ELASTIC_PLASTIC (*MAT_157). The initial input is the same as above, with minor changes to the target options and additional fields being specific for the initialization of material properties for (*MAT_157) with the *INITIAL_STRESS_SHELL card.
This section covers:
| TargetMaterialModel = INT |
Define the ID of the target material model corresponding to [20]. Here, it must be 157. |
| NTHICK = INT | The number of through-thickness integration points in the target mesh. |
| NPLANE = INT |
1 - Reduced integrated shell elements 4 - Fully integrated shell elements |
| MapStress = YES | Define whether *INITIAL_STRESS_SHELL cards should be written. If the data should be available for the *MAT_157 material model via *INITIAL_STRESS_SHELL cards, this option should be YES. Newer versions will also map the stresses stored on the source mesh to the target mesh. These stresses may be the result of a spring-back simulation, performed within Moldflow. If stresses should not be mapped, exclude them from the source mesh. |
| MapMainDir = NO | Activate mapping of the main directions onto *ELEMENT_SHELL_COMPOSITE cards. For use with *MAT_157, this option is NO. |
| TargetThickness = DOUBLE | Define the thickness of the target part. If a SectionFile is included in the source mesh, this value is ignored. If the target mesh already has elements with a thickness value, this option can again be ignored. |
| IHIS = INT |
Flag that defines the material parameter written to *INITIAL_STRESS_SOLID cards for *MAT_157, according to [20]. The following values are supported: |
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IHIS = 1 - q-values are written to the first two history variables. | |
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IHIS = 3 - q-values are written to the first two history variables, tensor components Cij are written to history variables #7 - #27. | |
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IHIS = 11 - q-values are written to the first two history variables, tensor components Cij are written to history variables #7 - #27, table IDs for strain rate dependent plasticity are defined in history variable #28. | |
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For IHIS = 1, no further input has to be defined. | |
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If IHIS > 1, define the following variables: | |
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HomogenizationMethod = Halpin − Tsai Tandon − Weng Voigt Kukuri Mori − Tanaka 1 Mori − Tanaka 2 Mori − Tanaka 3 | Define the homogenization method used to calculate the unidirectional stiffness matrix. For further information about these methods, see [10] or [16]. |
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ClosureApproximation = Linear Quadratic HybridA HybridB ORF ORS |
Define the closure approximation method used to calculate the 4th-order orientation tensor from the 2nd-order orientation tensor given by Moldflow. For further information about these methods, see [10] or [16]. ORF calls the orthotropic fitted closure approximation proposed by [12], distinguishing between different fiber interaction coefficients based on the equation provided in [7]. ORS refers to the orthotropic smooth closure approximation. |
The following elastic constants must be defined:
| E11F = DOUBLE | Fiber Young’s modulus in the main direction. |
| E22F = DOUBLE | Fiber Young’s modulus perpendicular to the main direction. |
| RHOF = DOUBLE | Fiber density. |
| PRBAF = DOUBLE | Fiber in-plane Poisson’s ratio. |
| PRCBF = DOUBLE | Fiber out-of-plane Poisson’s ratio. |
| G12F = DOUBLE | Fiber shear modulus. |
| EM = DOUBLE | Matrix Young’s modulus. |
| RHOM = DOUBLE | Matrix density. |
| PRM = DOUBLE | Matrix Poisson’s ratio. |
| AspectRatio = DOUBLE | Fiber aspect ratio (length/thickness). |
| FiberVolumeFraction = DOUBLE |
Fiber volume fraction in percent. |
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InclusionShape = Ellipsoidal Spherical Needle Disc |
Shape of the inclusions. |
If IHIS > 3, you must define several direction-dependent curve files, representing different strain rates, so that the strain rate and direction-dependent plasticity can be defined. The following input can be given:
| NumberOfCurveFiles = INT |
Define the number of curve files that are read. |
| CurveFileName#i = STRING |
Define the name and, if needed, path of the curve files. This card must be written NumberOfCurveFiles times. |
| NumberOfDirections = INT | Define the number of directions to which the curve files belong. The recommended value for short fiber reinforced plastic materials is 3. |
| Direction#i = DOUBLE | Define angles, relative to the direction of flow, used to generate the plasticity curves. Typical angles are 0◦, 45◦, and 90◦. This card must be written NumberOfDirections times. |
| NumberOfStrainRates = INT | Define the number of strain rates to which the curve files belong. |
| StrainRate#i = DOUBLE | Define the strain rates that are considered by the defined curves. This card must be written NumberOfStrainRates times. |
| StrainRate#iDirection#j = INT | Define the curve IDs that belong to the respective strain-rate/direction combination. This card must be written NumberOfDirections x NumberOfStrainRates times. |
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HISV_HANDLING = YES NO CLEAR | Enables you to move and modify history variables manually. Refer to [20] and [4] for the meaning of these. If CLEAR, all history variables will be removed before generating the result file. If YES, define as many history variables as should be modified (see below). |
| MAX_NUM_HISV = INT | Define the new maximum number of history variables. This is an easy way to remove unwanted histories that are of no use for the new model, but also enables you to extend the number of histories being output. If a history variable is being moved to a position which is higher then the actual number of history variables in the input deck, the number of histories will be extended automatically. |
The Envyo application implements an equation parser based on the Shunting yard algorithm and is available as an MIT license [6]. This equation parser has been modified to work with common LS-DYNA application variables such as histories, and effective plastic strains and stresses. Variables are declared using the & symbol and commands are executed in the order of input. The following variables are available:
| &HISV#i |
History variable at position i. |
| &EPS |
Effective plastic strain (the last entry in *INITIAL_STRESS_SHELL which may have a different meaning to eff. plast. strain). |
| &ELELENGTH |
Element length of the current element. |
| &SIG_IJ |
Components of the second order stress tensor. |
| &SIG_INIT |
Enables initialization of a specific stress value that refers to all stress components. |
| exp |
Exponent. An alternative input would be e**. |
Example
The following example illustrates usage of the equation parser. The commands following the additional history are executed in the order of input:
&HISV#4 = abs(&HISV#3-&HISV#2)*0.000467354 &HISV#8 = &HISV#2 &HISV#9 = &ELELENGTH MAX_NUM_HISV = 8
The value of history variable #4 will be calculated using the absolute value of history #3 - #2, multiplied by a scale factor. Following these operations, history variable #8 will be assigned the value at history variable #2, and the element length will be stored at history variable #9. Nevertheless, only eight history variables will be written to the final result file due to MAX_NUM_HISV.