For *MAT_157, several additional mapping input data are required to intitialize the orientation and more components at the integration point level. Additional input parameters are dependent on the chosen IHIS option.
| IHIS = INT | Flag that defines the material parameter which is written onto *INITIAL_STRESS_SOLID cards for *MAT_157, according to [20]. The following values are supported: |
| IHIS = 1 | Q-values are written on the first two history variables. No further input must be defined with this option. |
| IHIS = 3 | Q-values are written on the first two history variables, tensor components Cij are written on history variables #7 - #27. |
| IHIS = 11 | Q-values are written on the first two history variables, tensor components Cij are written on history variables #7 - #27. Table IDs for strain rate dependent plasticity are defined on history variable #28. |
Important: If IHIS > 1, define the following variables:
|
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]. |
|
ClosureApproximation = Linear Quadratic Hybrid A Hybrid B 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 in the thickness 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 to thickness). |
| FiberVolumeFraction = DOUBLE | Fiber volume fraction in precent. |
|
InclusionShape = Ellipsoidal Spherical Needle Disc | Shape of the inclusions. |
If IHIS > 3, you must define several direction-dependent curve files, belonging to different strain rates so that the strain-rate and direction-dependent plasticity is defined. The following input can be given:
| NumberOfCurveFiles = INT | Define the number of curve files which are read. |
| CurveFileName#i = STRING | Define the name and, if needed, the path of the curve files. This card is written NumberOfCurveFiles times. |
| NumberOfDirections = INT | Define the number of directions to which the curve files belong to. A recommended value for short fiber reinforced plastic materials is 3. |
| Direction#i = DOUBLE | Define angles compared to the flow direction which are used to generate the plasticity curves. Typical angles would be 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 to. |
| StrainRate#i = DOUBLE | Define the strain rates that are considered by the defined curves. This card has to be written NumberOfStrainRate times. |
| StrainRate#iDirection#j = INT | Define the curve IDs that belong to the respective strain-rate and direction combination. This card has to be written NumberOfDirections x NumberOfStrainRates times. |
The Envyo application implements an equation parser based on the Shunting yard algorithm and is available as MIT license [6]. This equation parser is modified to work with common LS-DYNA application variables such as histories, eff. plast. strains, and stresses. Variables are declared by 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 than eff. plast. strain). |
| &ELELENGTH | Element length of the current element. |
| &SIG_IJ | Components of the second order stress tensor. |
| &SIG_INIT | Enables initializing a specific stress value that refers to all stress components. |
| exp | Exponent. An alternative input would be e**. |
Example
The following example illustrates the 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 is calculated using the absolute value of history #3 - #2, multiplied by a scale factor. Following these operations, history variable #8 is assigned the value at history variable #2, and the element length is stored at history variable #9. Nevertheless, only eight history variables are written to the final result file due to MAX_NUM_HISV.