Overview
Finite element analysis (FEA) is a powerful tool for simulating the behavior of complex structures and materials under various conditions. However, accurate modeling requires accurate material properties, which can be difficult to obtain. Material calibration is the process of determining the “software” properties (material behavior constants) from material test data (experiments). Material calibrations can be created in three general steps:
Create data sets or import data sets into Abaqus/CAE or 3DEXPERIENCE® platform.
Process these data sets using filters and tools that enable you to scale, smooth, and truncate the data and to convert the data between nominal and true forms.
Derive material properties such as Young's modulus, Poisson's ratio, Mullins effect or others from your data sets.
Abaqus FEA and the 3DEXPERIENCE® Platform both offer material calibration capabilities, but how do they compare?
Abaqus Material Calibration
The three steps of any typical material calibration in Abaqus is explained below and is shown on the Figure below.
Figure 1: Typical workflow of Material Calibration in Abaqus
The first step is to import material data to Abaqus from text (.txt) files and customize these data in a data table. You can also specify quantity types to describe the data, such as stress and strain or force and displacement.
Optionally, the second step is to perform some data processing in Abaqus to clean up your material data before using it to define material behaviors. This includes:
Converting calibration data between nominal and true forms (i.e., engineering stress to true/nominal stress, since Abaqus uses nominal stress)
Scaling calibration data.
Smoothing calibration data.
Truncating and shifting calibration data.
You may also choose to perform the second step in Excel, MATLAB or equivalent prior to importing to Abaqus.
The third step is to define the calibration behavior in Abaqus, which is dependent on the material and behavior of interest. Abaqus offers a variety of material models that can be calibrated to experimental data. These models include isotropic elasticity, isotropic elasticity-plasticity, and hyperelasticity, among others. Here are the Abaqus material calibration behaviors supported in Abaqus:
Converting calibration data between nominal and true forms (i.e., engineering stress to true/nominal stress, since Abaqus uses nominal stress)
Calibrating data for isotropic elastic-plastic material behavior
Calibrating data for hyperelasticity with permanent set
The hyperelasticity with permanent set calibration behavior enables you to extract plastic and hyperelastic material behaviors and Mullins effect from uniaxial and biaxial data sets of the loading, unloading, and reloading of elastomers and thermoplastics. You can extract data from a uniaxial test, a biaxial test, or from both types of tests. The calibration process includes the following steps:
Upload uniaxial and/or biaxial test data files into Abaqus/CAE as new data sets.
Extract the loading, unloading, and reloading cycles and the permanent set data from the data files you provide and create separate data sets for the load, unload, and reload phase of every cycle.
If desired, select any data cycles that you want to exclude from calculations of material behavior.
Select the yield point from the viewport and, if desired, edit individual points on the primary loading data set to create a smoother curve. The permanent set curves are based upon the current yield point, so these curves also change when you select a new yield point.
Once you determine the test data sets that you want to use for deriving material behaviors and you specify primary curve options, you can derive material behaviors from the selected data. Abaqus/CAE maps plastic, hyperelastic, and Mullins effect material behaviors to the material you select.
Calibrating data for custom behaviors
The isotropic elastic calibration behavior enables you to derive isotropic elastic data (Young's modulus and Poisson's ratio) from calibration data sets and to apply these material constants to the elastic material properties of a material definition in your model.
The isotropic elastic-plastic calibration behavior enables you to derive isotropic elastic and plastic material behaviors.
You can also add support for custom calibration behaviors, which appear as new options in the Calibration Behavior dialog box. For more information, see "Creating custom material calibration plug-ins in Abaqus/CAE" in the Dassault Systèmes Knowledge Base at http://support.3ds.com/knowledge-base/.
Once the steps above are completed, and the Behavior defined is executed, Abaqus will automatically create a Material Model with the evaluated behavior constants.
3DEXPERIENCE® Platform Material Calibration
The 3DEXPERIENCE® Platform includes a suite of tools for material modeling and simulation. The platform uses a unified data model to integrate simulation and manufacturing processes, making it easier to manage and share material data across different applications.
The Material Calibration app within the 3DEXPERIENCE® Platform allows users to calibrate material models to experimental data. The app includes a variety of material models, including polymers (elastomers and elastomeric foams), crushable foams, geomechanics materials, cohesionless soils, concrete, etc. Users can specify the experimental data and the material model to be calibrated, and the app generates a simulation model that can be run and analyzed within the platform.
Some of the available material models for material calibration in 3DEXPERIENCE® Platform are listed and shown in the Figure below.
Linear elasticity Models with or without (Plasticity, Creep, Both, Linear Viscoelasticity, etc.)
Hyperelasticity Models with or without (Linear viscoelasticity, plasticity, Mullins effect, etc.)
Hyperfoam Models with or without (Linear viscoelasticity, Mullins effect, etc.)
Chaboche Model
Drucker-Prager Plasticity model
Parallel Rheological Framework (PRF) Models (multi-network)
User-defined Materials
and much more...
Figure 2: The available material models for FE mode in 3DEXPERIENCE® Platform
A typical workflow of the material calibration on the 3DEXPERIENCE® Platform is shown in the figure below. It starts by importing the test data, then continue editing the test data if needed, define the calibration mode, and the material model, define the optimization option and finally execute the calibration and review the results.
Figure 3: Typical Workflow of Material Calibration on the 3DEXPERIENCE® Platform
Watch the YouTube video to learn more about the advanced material calibration capabilities of the 3DEXPERIENCE® Platform:
Portfolio Connections: Isight
Isight and Abaqus can be combined to automate and optimize material calibration. Isight is a tool provided free-of-charge with every Abaqus purchase, as part of the new extended packaging of Abaqus (Power of the Portfolio).
Isight can:
Seamlessly encapsulate a workflow for complete automation
Run Abaqus simulations on unit test specimens
Compare the simulation response with physical experimental data
Perform an optimization that varies the material coefficients used in the Abaqus simulation to minimize the difference between the simulation response and the experimental data
Example: Lead-free solder material calibration
Modified Anand material model requires 15 material constants calibrated from 20 experimental data sets
Isight-calibrated material constants are able to predict material behavior at all data points
Reference: “Calibrating material constants from experimental data for lead-free solder materials using a parametric optimization approach” SIMULIA, NAFEMS WC-2011
