Interpolation

The interpolation functionality allows you to characterize your material at any temperature environment. If the selected temperature falls within the range of the provided stress-strain data, the new environment is interpolated between the nearest data points. If the selected temperature falls outside the range of provided stress-strain data, the new environment uses the closest known environment. In other words, there is no extrapolation of environments beyond the provided input boundaries.

The selected environment is used throughout the duration of the FEA simulation, regardless of the temperature of the individual integration points. It can be useful to use the interpolated environment during your FEA simulation if the known operating temperature of the part is in the range between the input environments for the material.

The interpolation functionality is defined by the following two HIN file keywords.

*SELECTEDENVIRONMENT

The *SELECTEDENVIRONMENT keyword is used to select a specific environment from the available environments stored in the SIF and HIN files. This keyword must be a child of the *MATERIAL keyword.

*SELECTEDENVIRONMENT, TYPE=[TENSILE/COMPRESSIVE], TEMPERATURE=temp, HUMIDITY=humidity, STRAINRATE=strainrate

The parameters for the *SELECTEDENVIRONMENT keyword contain the environment specifications for temperature, strain rate, and humidity. If

• If the inputs combine to match an environment in the SIF file, that environment is selected for use in the analysis.
• If no match for the input temperature is found, the closest environment with matching strain rate and humidity inputs is used.
• If no match for the input temperature is found and there are no environments matching the input strain rate and humidity, an error is issued.
• If only a single environment exists in the SIF file or if there is only one environment that matches the input strain rate and humidity, the single environment is used.
• If the .SIF file contains material data for both tensile and compressive environments, but only the tensile environment is defined with the *SELECTEDENVIRONMENT keyword, that environment is used for the compressive case as well.

*INTERPOLATION

The *INTERPOLATION keyword activates the temperature interpolation of the material environments. It must be used in conjunction with the *SELECTEDENVIRONMENT as a child of the *MATERIAL keyword.

*INTERPOLATION, TYPE=TEMP

TYPE=TEMP indicates temperature interpolation is to be used. Currently, temperature is the only type supported. If the selected environment (as defined by the *SELECTEDENVIRONMENT keyword) is outside the temperature bounds of the available environments in the SIF file, the closest environment is used.

Consider the example below which activates temperature interpolation and requests an environment at a temperature of 52.5 degrees, a humidity of 41%, and a strain rate of 0.01.

*MATERIAL, NAME=CA-MATERIAL-1
*INTERPOLATION, TYPE=TEMP
*SELECTEDENVIRONMENT, TYPE=TENSILE, TEMPERATURE=52.5, HUMIDITY=41.0, STRAINRATE=0.01