Week - 9 Material modeling from raw data

OBJECTIVE :

Using the diagram of the true stress-strain curve of graphite iron casting. Two curves are there for different material structures. I need to pick any one of them and use the data to create either a MAT_024 or MAT_018 material model and then validate it.

Theory :

Materials modelling is very necessary in order to make reliable predictions of the behaviour of different types of materials practically and also to eliminate the certain properties and make it used for better performance like cost of the materials, wear resistant, life cycle, improved fatigue etc...,

The main objective of the material modelling is to eliminate the testing on the main physical model and thus eliminating the cost, time and errors.

The process involves mainly two steps i.e, testing and data clean up after that material card is created in the software.

Procedure :

• Testing:

Identifying the standard material according to the requirement and the testing procedure is selected based on the testing and requirements then data is obtained from the experiments that are done on some big machines like UTM, after that testing is done on some more models of same property to get the accurate result.

As the data obtained is of force vs displacement or stress vs strain so to convert that basic formulas like

• Data clean up:

In this step the obtained results are in the graphical form, so to get each small interval points the data digitizer is used the obtained points are not in smooth form as the software’s works better if the curves are smooth so to get the better results the curve fitting is done using MATLAB, python or excel. Before that we need to check the units that units are converted according to the requirements.

• Converting the data:

As the data obtained is in the form of Engineering stress and engineering strain but the software takes the effective stress and effective plastic strain so to obtain this, we need to use some formulas that are as follows

• Keywords setup:

To validate the obtained experimental result the setup as been made in the software that is as follows. Firstly, the boundary is created that is arresting the degree of freedom in one side and motion set is given on the other side.

Defining the curve as shown in the below image

MAT024 card is used to give the material property of graphite iron casting that are density, young’s modulus, poison’s ratio and yield stress that are specified as shown in the image.

Section of 1.5 mm and material of graphite iron casting is assigned to the part

In database the required outputs are specified with giving the specific time interval of output (DT)

Control termination is used to end the experiment with giving end time.

Results:

From the below images we can see that the stress and strain is increasing according to the given condition.

Conclusion :

As per the objective the data is obtained from the graph clean up is done on the obtained data using excel, model is built on the software for the analysis and the result obtained are very much related to the practical data and hence the data's are validated.