UNCONVENTIONAL MATERIAL PART FEM ANALYSIS

The article covers the usability of alternative materials in vehicles construction. The paper elaborates upon the setup of the process and analysis of the results of carbon composite component FEM model. The 3D model, used for the examination, is a part of axle from alternative small electric vehicle. The analysis was conducted with the help of MSC Adams and Ansys Workbench software. Color maps of von Mises stress in material and total deformations of the component are the results of calculation.


Introduction
According to the statistical data from 2012, about 84 million vehicles were produced worldwide every year. This number has been increasing every year [1,2]. This is closely related to the problems of environmental pollution and at the same time reduction of oil reserves, which are the main source of fuel for more than 99% of the vehicles. Manufacturers and governments want to reduce fuel consumption. One of the current trends is called "Downsizing". This is about engine downsizing strategy and improvement of their energy balance, for example with the use of turbocharger. Other manufacturers are moving towards the use of alternative energy sources, hybrid technology or going the way of the weight reduction of vehicles using unconventional materials such as aluminum alloys, high strength steels or the use of carbon and other composites [3].

Analysis characteristics
The article covers the calculations of vehicles body strength made from unconventional material, specifically carbon fiber. Design and calculations are made by using the CAD system Creo Parametric 2.0, Catia and FEM software ANSYS Workbench, which includes the necessary functions to calculate the composite structural FEM model [4].
The process of creating a 3D model with next necessary modifications is described below.

3D model creation
As a first step, the model and shell structure were created in the Creo Parametric 2.0 software. The shell thickness was the same as the thickness of composite, which the component was made from. The part is a component from an assembly of a small vehicle frame shown in fig. 1.

Extraction of the 3D surface model
By using CATIA V5 software, the outside surface of the 3D model was extracted. The extracted geometry of the calculated part is shown in fig. 3. Extraction was performed by using the "Multiple Extract" feature. Consequently, it was necessary to save this area in STEP format and define it in ANSYS Workbench as the basic geometry [5,6].
Second part of this section described the procedure of definition of boundary conditions in ANSYS Workbench software.

Defining the boundary conditions
After the transfer of the extracted areas from the 3D model into the ANSYS Workbench, defining the boundary conditions of component-size or location of a burdensome power,the location and number of degrees of freedom withdrawal of component is needed (Fig. 4).

Definition of material properties
The component was simulated as an element made of the carbon fiber composites. Selection of a predefined material from the software library which characteristics correspond with used carbon fabric is needed [7]. The next step was to create a fabric with a thickness corresponding to the thickness of the carbon fabric offered by different manufacturers. Creation of the laminate followed the determination of the type and thickness of the fabric (Fig. 3).
It is important to choose the order of layers and the orientation of the carbon fibers correctly, when entering the laminate in it [8,9]. The next part of the article describes the procedure of strength calculations of the components in ANSYS Workbench, in order to obtain the values of tension and deformation of the desired structure.

Selecting the direction of orientation of the layers of laminate
It is necessary to select the area that will define the shape and orientation of the neutral axis of the filaments. Fig. 5 shows the distribution of fibers within the laminate and directional laminate stiffness which depends on the angle of rotation of the individual layer of fabrics neutral axis. Dimensions of layers are on the left side of the picture and the stiffness characteristic on the right side.

Results analysis
The results analysis of classical strength calculations of material's stress (Fig. 7) and total deformation of the component (Fig. 8) was necessary to achieve the goal of the research. The maximum von Mises stress value was detected in the thinnest area of the frame part (881 MPa) and the maximum deformation in the y-axis at the end of the part (51.104 mm).

Conclusions
The results of simulation of the frame part made from a carbon composite had shown the possibility of usage of this type of material for small vehicle suspension without the need of the classical spring arrangement.

Acknowledgment
This paper presents results of work supported by the Slovak Scientific Grant Agency of the Slovak republic under the project No. VEGA 1/0077/15.