# Techniques for Material Model Calibration in Abaqus

## Abaqus Material Model Calibration

As an Abaqus user, when working with material models, you have faced the challenge of finding constants/coefficients /parameters for the material model, such as Johnson-Cook plastic properties, coefficients of Hyperelastic models, coefficients of creep relations, and things like this.
This is a challenge for all simulation engineers and especially for Abaqus application engineers. For this reason, I tried to collect as many available tools as possible, such as plugins, software, and other tools. I try to update this blog over time.
Since the content volume may be large, I will divide this blog into several separate blogs according to specific topics and updates will be made in the same blog.
The goal is that we, as FEA analysts, can obtain the parameters and coefficients of the material model under investigation using laboratory test data for use in the Abaqus in the shortest possible time.

### What is a material model?

The material model is one of the main things that a simulation engineer works with. it is a mathematical representation of the behavior of a material under various conditions. It is used in simulations to predict how a material will behave in a given situation. Material models can be simple or complex, depending on the level of accuracy required and the class of materials being modeled. They are commonly used in engineering, physics, and materials science.

### So, what is material calibration?

Perhaps the first question that arises is what is material calibration?

In computational mechanics, calibration means:

Therefore, the material calibration means:

In other words, material calibration involves “reverse engineering “ the material coefficients/parameters based on available tests (experimental) data.

The goal is to ensure that the material model accurately captures the mechanical response of the material under various loading conditions. This is important for engineering simulations and analyses, as it allows for more accurate predictions of how a structure or component will behave in real-world scenarios.

So, the accuracy of a finite element simulation’s ability to capture the behavior of a structure is highly dependent on the material model selected. The material model must be:

1. Suitable for the intended application and class of materials,
2. Properly calibrated.

Sophisticated material models that require many parameters can present a challenging calibration task, but optimization techniques can be utilized to determine appropriate parameter values.

Well, there are different methods for curve fitting laboratory tests and determining material constants. In the following, for each category of materials, I will share with you the methods of determining the constants that I usually use myself, and I hope you will also help me with this.

## Plasticity Models

What do you do to calibrate and determine the plasticity parameters of material models?

Suppose you want to prepare the Johnson-Cook constants of a metal material using experimental test data for Abaqus. How do you get them?

The calibration app in Abaqus only supports elastic, isotropic plastic, and hyperelastic behaviors. Maybe not all of us use the Material Calibration App in 3DEXPERIENCE. Although it must be said that it is very good that this app is being developed.

My experience says that using Abaqus plugins or Excel is very helpful. That’s why I try to share my experience with calibrating materials in Abaqus on this page with FEA analysts.

## Plugins

### 1- Plastic Curve Generator Abaqus Plugin

This Plug-in implements different plastic laws for defining plastic curves. Hollomon, Ludwik, Johnson Cook, Swift, Krupkowski, Ramberg-Osgood, Ramberg-Osgood Simplified, and Ramberg-Osgood Modified which is done by Curve Fit, Least-Squares, and similar operations to estimate the material parameters.

Two of the laws (Hockett-Sherby and Hollomon Linear Constant) are based on an iterative process to fit FEM results to experimental data. That is, to determine the plastic parameters, the material parameters are determined by making a virtual laboratory specimen and using iteration with the FEM method.

## Abaqus tutorials

Abaqus Tutorial: Abaqus/CAE Plug-in Utility to Calibrate Nitinol Material Behavior