If you're involved in engineering simulations, you know that creating accurate and reliable models (especially material models) can be a time-consuming and challenging process. One of the key factors in creating accurate simulations is properly representing the microstructure of the material being studied. This requires defining a Representative Volume Element (RVE) that captures the important features of the microstructure at the scale of interest. This is commonly used for defining the constituents of a system and/or microstructures, and it is particularly common for modelling composites, or the unit cell of lattice (cellular) structures common in additive manufacturing.
What is an FE-RVE?
A finite element (FE) model of a representative volume element (RVE)
An RVE is a volume of a microstructure that is large enough to yield the microstructure’s aggregate response.
Periodic RVE – when a microstructure tessellates and is under uniform far-field loading, aggregate behavior can be obtained from one tessellating cell (a unit-cell) using periodic boundary conditions.
Abaqus provides a plug-in that can help with this by allowing you to automate the process of creating RVEs, namely “Micromechanics Plugin”. You can use this plug-in to define the material properties of the RVE and generate the appropriate mesh. This can save you a significant amount of time compared to manually creating RVEs for each simulation.
In addition to automating RVE creation, the plug-in can also help with far-field loading. Far-field loading is a type of loading that is applied at the boundaries of the simulation domain and is used to model the effect of external forces on the system being studied. With the plug-in, you can define far-field loading through periodic or non-periodic boundary conditions, and set up the loads and analysis steps necessary to perform homogenization of properties or imposition of a far-field load history.
Overall, the Abaqus plug-in is a powerful tool for automating and streamlining the process of creating accurate and reliable engineering simulations. Whether you're working with microstructures, far-field loading, or other complex simulation scenarios, the plug-in can help you save time and reduce the potential for errors. If you're interested in learning more, be sure to read the below blog, and download the free plug-in and its manual from here:
- The plugin should be extracted into an abaqus_plugins directory (for instance,$HOME/abaqus_plugins) in Abaqus installation directory. It can then be accessed from the Plug-ins main menu in Abaqus/CAE.
- The plugin works with Abaqus/CAE version 2016 or later. Earlier versions of Abaqus/CAE will not function correctly.
The plugin has a range of features that allow for:
Generation of Finite Element Representative Volume Elements (FE-RVE) with specific geometries in a parameterized manner. This includes unidirectional continuous fiber reinforced composites with hexagonal fiber packing, and body-centered or simple-arrayed ellipsoids.
Automated imposition of various boundary conditions on the FE-RVE, including periodic boundary conditions, Taylor boundary conditions (where the RVE surface is constrained to the far-field gradient), and Neumann boundary conditions (where the far-field flux is applied to the RVE surface). These conditions can be driven by user-defined histories or field histories from a larger-scale analysis.
The study of various RVE physics, such as mechanical analysis of both continuum and shell-like microstructures, steady-state heat transfer, and steady-state coupled temperature-displacement.
Homogenization of the material properties of the RVE, including elastic stiffness, thermal expansion, shell section stiffness (ABD matrix), thermal conductivity, fully coupled conductivity-stiffness (9x9 constitutive matrix), density, and specific heat.
Post-processing tools such as field averaging in the entire RVE and per-phase, as well as histogram generation. These tools can help in analyzing the simulation results and understanding the behavior of the system being studied.
Figure 1: RVE Libraries
Figure 2: RVE Boundary Conditions
Figure 3: Homogenization
Figure 4: Post-Processing
Overall, the plugin provides a wide range of functionalities that can greatly benefit engineers and researchers from automating the creation of FE-RVEs with specific geometries to analyzing various RVE physics and homogenizing material properties. The post-processing tools also provide valuable insights into the behavior of the system being studied, making it an essential tool for anyone working in this field.
General Workflow of the Micromechanics Plugin – An Example
There are a broad variety of applications and workflows that these capabilities can be applied to. The preceding figure gives an example of a multi-scale workflow that can be facilitated by the plugin.
Material Calibration Step: Characterize the response of a unidirectional composite material at the micro-scale using a fiber-matrix model to predict the transversely isotropic elastic response.
Material Calibration Step: Characterize the response of a textile laminate at the mm-scale using a textile unit cell model with shell-like boundary conditions to obtain the shell section behavior.
Study Response Step: Conduct an engineering structure simulation at the m-scale to obtain the response of the structure.
Study Response Step: Examine the response of the textile laminate at the mm-scale by analyzing the shell deformation at some point of interest in the engineering structure.
Study Response Step: Examine the response of the fiber-matrix at the micro-scale by analyzing the strain history from a location in the tow, using a fiber-matrix unit cell, all based on the predicted response of the engineering structure.