Product: Abaqus/Standard
Benefits: Field expansion is similar to thermal expansion except that it is driven by a user-specified predefined field variable instead of temperature. It can be used to model stresses due to volumetric expansion as a result of, for example, moisture absorption by a structure.
Description: Abaqus/Standard now allows the modeling of volumetric expansion caused by physical effects that are similar to thermal expansion. Field expansion strains are computed based on user-specified field-expansion coefficients (that can be defined independently, if needed, for more than one field variable at a time) and the change in the value of the corresponding predefined field variable about some reference value. Similar to strains associated with thermal expansion, field expansion strains can result in significant stresses in situations where the structure is constrained from undergoing free expansion.
This capability can be used to model the stresses due to the combined effects of thermal expansion and moisture absorption in microelectronic components. The workflow is typically as follows:
Carry out a heat transfer analysis to determine the temperature distribution in the component.
Use these results to drive a mass diffusion analysis that computes the distribution of moisture concentration in the component.
Perform a stress/displacement analysis to determine the stresses due to (i) thermal expansion associated with the temperature distribution and (ii) field expansion associated with the moisture concentration distribution, where the field expansion is driven by the moisture concentration, which is treated as a predefined field variable in the stress/displacement analysis.
You can find further details on importing the mass concentration as a predefined field variable in “Reading nodal output for temperature, normalized concentration, and electric potential from an output database into predefined field variables,” Section 9.3.
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