What problem does the software solve?

When we expose a solid body to strain (stretching, compression), particles inside the body move. If the strain exceeds a specific threshold, deformation caused by the strain is irreversible. The characteristic property of some groups of materials is that they react to a small strain with a substantial change in shape and dimensions. The change may be measured in tens, but often hundreds of percent of the original dimensions.

A fundamental property of these materials is also their ability to rapidly return to their original shape and original dimensions, immediately upon releasing the strain. If a material possesses both the above-mentioned properties, it is termed a hyperelastic material. Hyperelastic characteristics are seen in e.g. rubbers or soft biological tissues.

To understand the behaviour of such materials it is not enough to observe them from the outside; rather, it is necessary to focus on processes in their internal structure. Strain deformation responses of hyperelastic materials do not occur in a linear manner and they are difficult to simulate. For this, constitutive models are used, which are currently realized as with the assistance of computers.

New software tool developed at BUT

HYPERFIT software is used for identifying the parameters of hyperelastic constitutive models. The software tool implements a large number of constitutive models currently used for computing simulations of elastomers (rubbers) and soft tissues (vascular walls etc.), several types of experimental tests, an unlimited number of input experimental tests, several types of weight units for weighted regression, various types of residua, specific models for non-elastic effects and lots of other parameters and settings available to the user.

The added value HYPERFIT software primarily offers is the unification of various procedures in one tool which is not dependent on a superordinate commercial platform and which can easily be extended. Compared to most commercial systems it also offers the very latest functions (on-line imaging etc.).

Solution in practice

HYPERFIT can be used in any sphere of human interest where hyperelastic materials can be found. The particular avenues pursued in the Faculty of Mechanical Engineering included modelling material behaviour in crash-tests (in what crash situations would vehicle passengers still not be in danger) or simulating the behaviour of arterial aneurysms (what conditions constitute a risk of aneurysm rupture and what parameters should an artificial substitute potentially meet).

The leader of the programme, Ing. Pavel Skácel, Ph.D., works in the Institute of Solid Mechanics, Mechatronics and Biomechanics at the Faculty of Mechanical Engineering, Brno University of Technology.