Implementation of algorithms in a software tool: AgedMAT

AgedMAT is the software tool that integrates the different successful algorithms developed in this thesis, allowing the user to consider easily the age of the subject as an important variable affecting significantly the different human tissues. With this tool, the users can output the estimates for the different human tissues properties in function of the age, required to model the human body in vehicle safety environments. Therefore, this scaling tool is designed to cover, with different degrees of definition, the influence of age and strain rate in bones, cartilage, ligaments, tendon and skin.

The scaling tool is structured in three parts:

• The Input panel, where the user defines the age of the subject to calculate the different material properties.

• The Results panel, where the calculations are displayed to the user in different forms.

• The Output panel, where the user defines which output the tool will generate into disk.

The user can navigate through them as shown in the Figure 4-21, going from the input forward to the result panel, from the result panel back to the input or forward to the output

panel and from the output panel back to the result or the input panels. The current panel is shown in all the caption bars of the different forms.

Figure 4-21: Navigation options between panels of AgedMAT.

The input panel welcomes the user to the application giving the basic information about the tool, allowing the user to start the application once the input box is filled with the age of the subject (left), enter into the application tutorial (middle) or exit the application.

Figure 4-22: Input panel of AgedMAT.

Section II: Multibody analyses of pedestrian scenarios

Units Parameter

Bones Soft tissue

Ultimate strength MPa MPa

Yield stress MPa MPa

Elastic modulus GPa MPa

Ultimate Load -- N

Strain % %

Table 4-13: Units used for AgedMAT©.

Figure 4-23: Results panel for bones.

The results panel aims to present the user the whole set of material parameters for a human subject of the different ages, using as units for each of them the ones summarized in the Table 4-13. It is divided into two sub-folders:

• The bones properties folder, which has two parts: On the left part, the bone properties folder shows the numerical value of the Ultimate Compression Strength

(UCS), Elastic Modulus in compression (Ec): Ultimate Tensile Strength (UTS), Elastic Modulus in tension (Et) Ultimate Strain (Ustrain, Yield strength (YS), Elastic Modulus of plasticity (Ep) for different cortical bones. On its right part, the user can see the stress-strain function in tension and compression resulting from these parameters at the reference strain rate. Extra buttons named “strain rate” into each cortical bone areas lead to pop-up forms that show the behaviour of the stress strain curve at different strain rates (shows slices of the surfaces shown in Figure 4-20) and calculate the parameters for Johnson-Cook and Cowper-Symonds models for strain rate dependency. Under these parameters, a note reads informing about the maximum and minimum strain rate considered to fit the strain rate dependency models.

• The soft tissue folder, where the material parameters for tendon, ligaments, cartilage and skin are shown. Tensile material properties are given for all the soft tissues (tendons, ligaments, cartilage and skin) (Ultimate Tensile Strength, Elastic modulus in Tension and Ultimate Strain) while compression properties are only found for cartilages (Ultimate Compression Strength, Elastic modulus in Compression). Only the numerical values given into white background do depend on age. The bold yellow values are only recommended range values, as there were not enough data to build an age dependent functions for them.

Figure 4-24: Results panel for soft tissues.

Section II: Multibody analyses of pedestrian scenarios

Additionally to these two folders, navigation buttons to go back to the input panel or to go forward to the output panel, along with the help button and the exit button, are available in the bottom part of the panel.

Finally the output panel gives the user the interface to define the outputs from the application as well as it presents similar navigation capabilities than the previous panels.

There are two options to output from the tool, each of them available in each of the two folders of the panel.

In the “output to file” folder, the user can define the parameters to output from the tool between the whole set of parameters calculated to be exported into a user-defined folder.

The output to file folder allows the user to select which data output to a file by a checkbox.

(Bone properties data, strain rate dependency model parameters, soft tissue data and images). When click to the export outputs button, the user is asked to select a folder. In this folder, the application creates the files where the data is exported:

• If the images are exported, each one is exported as jpeg file in this folder.

• If any of the datasets are exported, a text file named props_at_age_of_(input age).txt is created. This file contains the information regarding each data set selected in the checkboxes: (bone data, soft tissue data and strain rate dependency model parameters).

Figure 4-25: Output panel: export to file folder.

The “output to model” folder was included in AgedMAT in order to automatically update mathematical FE models to a selected age; however, this automatic generation of an elder pedestrian model has not been programmed in the current release.