Material Model Definitions

The Granta Material Model Service has endpoints to create and download Material Model Definitions.

Here is an annotated example JSON file. Note: The comments are included in this example for informational purposes. Do not include comments in real Material Model Definitions.

{
    "id": "model.id", 
    "name": "Model name",

    // These are material model properties. These will be dependent on the free parameters (if specified).
    // These are output in a single table with a column for each property and each free parameter.
    // If there are no free parameters, then this table will always contain a single row.
    "properties": [ 
        {
            "name": "Property name output in model", 
            // The symbol that this property usually takes in the material model equation.
            "symbol": "σ", 
            
            // A list of Standard Names, used to identify the Attribute
            // from which data will be exported for this property.
            // If an Attribute corresponding to the first Standard Name is found in the database, 
            // the Material Model Service will use this, otherwise the next Standard Name is examined.
            "attributes": [ 
                {           
                    "standardName": "Attribute standard name"
                }
            ],

            // Optional set of free parameters. If specified, the properties specified in the 
            //`properties` array will be output as a function of these parameters 
            "freeParameters": [ 
            {
                    // The Standard Name of the parameter in the database. 
                    // This is also the name that the parameter is given in the material-model-output.
                    "standardName": "Parameter standard name", 

                    // The symbol that this parameter usually takes in the material model.
                    "symbol": "ε" 
                }
            ],

            // Indicate if a property is optional (defaults to false)
            // If a property cannot be resolved and it is not optional, it will cause the export to fail. 
            // If the property is optional, it will be omitted from the output.
            "optional": true,

            // Specifies how to produce the value for this property from a range value in the database. 
            // If the attribute used is not a range, this setting has no effect.
            // Possible values are: [ GeometricMean, ArithmeticMean, Minimum, Maximum ]
            // Defaults to GeometricMean
            "rangeValueToUse": "ArithmeticMean",
        },

        // example of a property which doesn't depend on free parameters
        {
            // The name that the property is given in the material-model-output.
            "name": "Property name output in model", 
            
            // The symbol that this property usually takes in the material model equation.
            "symbol": "x", 
            
            // A list of Standard Names, which identifies which Attribute data to export for this property.
            // If the first Attribute is identified in the database, the Granta Material Model Service will use this 
            // otherwise the next Standard Name is examined.
            "attributes": [ 
                {           
                    "standardName": "Attribute standard name"
                }
            ]
        }
    ],

    // The value of parameters to use if we need to interpolate Functional Attributes. 
    // Specific Parameter definitions are optional. If not supplied, the default parameter
    // value as defined in the database will be used when needed.
    "constraints": [
        {
            // The Standard Name of the Parameter.
            "parameter": "Temperature",
            // The default value.
            "defaultValue": 73,
            // The unit.
            "unit": "°F"
        }
    ],

    // Packages that this Material Model Definition applies to. 
    // If this list is null/empty, this Material Model Definition will be applied to all packages.
    "restrictedToPackages": [
        {
          "name": "ElectronicsDesktop"
        },
        {
          "name": "ConceptSI"
        }
      ],

    // If true, properties that share the same free parameters are consolidated into a single property in the output.
    // If false, all properties will be kept separate in the output.
    // Set this value to true only when properties use the same free parameters.
    "consolidatePropertiesThatHaveParameters": false
}

Examples

To write a Material Model Definition for the Hooke's law model:

{
  "id": "hookes.law",
  "name": "Hooke's law",
  "properties": [
    {
      "name": "Young's modulus",
      "symbol": "E",
      "attributes": [ 
        {           
          "standardName": "Young's modulus"
        }
      ]
    }
  ]
}

To take data from a Functional Attribute and interpolate it at a particular value. If the constraint for Temperature wasn't required, we would have used the default value defined in the database on the Attribute (or Parameter if the attribute 'Density with Temperature' did not define a default value for Temperature).

{
  "id": "density.room-temperature",
  "name": "Room Temperature Density",
  "properties": [
    {
      "name": "Density",
      "symbol": "ρ",
      "attributes": [ 
        {           
          "standardName": "Density with Temperature"
        }
      ]
    }
  ],
  "constraints": [
    {
      "parameter": "Temperature",
      "unit": "°F",
      "defaultValue": 73
    }
  ]
}

Creating a Material Model Definition

Material Model Definitions can be created by sending an HTTP POST request to the Granta Material Model Service /v1alpha/modelDefinitions endpoint. The body of the request should be a Material Model Definition in JSON format like the examples above.

Material Model Definitions can be updated using a PATCH request to /v1alpha/modelDefinitions/{id}.

For example: /v1alpha/modelDefinitions/hookes.law.

The request body should be a JSON Material Model Definition, but properties that do not need changing may be omitted (this endpoint uses the JSON Merge Patch RFC 7396 format).