Fig. 1. Before and after CIA treatment

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1 PROCEEDINGS OF THE INSTITUTE OF VEHICLES 3(89)/2012 (12pt) (12pt) Grzegorz Służałek 1, Marek Kubica 2, Mateusz Służałek 3 (12pt) COMPUTER METHODS IN STUDY OF HISTORICAL ASSYRIANS CHARIOT (12pt) 1. Introduction Assyrian chariots are exceedingly short, but apparently, they must have been of a considerable width. They contain two, three or even four persons. The warrior who fights from a chariot is necessarily attended by his charioteer [1]. Today's technology allows to recreate the battle chariot in the virtual CAD environment applications of the ancient model, as well as completing the analysis of materials in terms of stress, strain and displacement. In modern CAE programs engineering simulations could be performed. To modelling the battle chariot used a reverse engineering (RE) technique and computer image analysis (CIA). 2. Computer image analysis of the battle chariot For better analyze and visualize detailed images of the battle chariot computer image analysis (CIA) were done in the Met-Ilo and ImageJ applications. The computer image analysis allowed to treatment images by reducing noise, enhance clarity of the relevant factors. CIA was realized by using mathematical operations of gamma correction process, adjust contrast and brightness, subtract background, enhance contrast, the use of mean and median filters [2]. The images of Assyrian chariot before [1] and after CIA are shown on the figure 1. Fig. 1. Before and after CIA treatment The 3D surface plot plugin was used (fig. 2.). This plugin creates interactive surface plots from all kinds of image types. The luminance of each pixel in the image is interpreted as the height for the plot. Selections, also non-rectangular, are supported. The plot can be displayed in different color schemes: original colors, grayscale and different LUT schemes. Scale, rotation, perspective and position can be adapted. Using a smoothing option reduces noise. An adjustment of the lightning condition improves the visibility of small differences. 1 Grzegorz Służałek, Ph.D., Assist. Prof., Department of Materials Science, Faculty of Computer and Materials Science of University of Silesia 2 Marek Kubica, M.Sc., PhD student, the Faculty of Computer and Materials Science at University of Silesia 3 Mateusz Służałek,Student of University of Silesia 135

2 a) b) Fig. 2. Showing interactive 3D Surface Plot: a) grayscale b) Thermal LUT The surface plot supports four different drawing modes: dots, lines, meshes or a filled surface [3]. The visualization process of 3D surface plot plug-in work is shown on figure 3. Fig. 3. Visualization process of the proposed 3D rendering scheme [3] 3. 3D model of the assyrian battle chariot Autodesk Inventor software was used for the three-dimensional modeling and rendering the virtual reconstruction of the battle chariot. This program is the Computer Aided Design (CAD) tool for modeling in the 3D space, using solid model and surface model. Inventor model is an accurate 3D digital prototype that enables to validate the form, fit, and function of a design as you work, minimizing the need to test the design with physical prototypes. By enabling to use a digital prototype to design, visualize, and simulate models digitally, Inventor software helps communicate more effectively, reduce errors, deliver more innovative product designs faster [4]. The screenshots while creating the Assyrians battle chariot were showed on figures 4 and 5. Fig. 4. The chosen elements of the battle chariot in CAD software 136

3 Fig. 5. Wheals of the battle chariot 4. FEM analysis of the battle chariot The finite element method (FEM) is a numerical technique for finding approximate solutions of partial differential equations (PDE) as well as of integral equations. The solution approach is based either on eliminating the differential equation completely (steady state problems), or rendering the PDE into an approximating system of ordinary differential equations, which are then numerically integrated using standard techniques such as Euler's method, Runge-Kutta, etc. In a structural simulation, FEM helps tremendously in producing stiffness and strength visualizations and also in minimizing weight, materials and costs. FEM allows detailed visualization of where structures bend or twist, and indicates the distribution of stresses and displacements. FEM software provides a wide range of simulation options for controlling the complexity of both modeling and analysis of a system. FEM allows entire designs to be constructed, refined, and optimized before the design is manufactured [5]. This powerful design tool has significantly improved both the standard of engineering designs and the methodology of the design process in many industrial applications. The introduction of FEM has substantially decreased the time to take products from concept to the production line [6]. It is primarily through improved initial prototype designs using FEM that testing and development have been accelerated. In summary, benefits of FEM include increased accuracy, enhanced design and better insight into critical design parameters, virtual prototyping, fewer hardware prototypes, a faster and less expensive design cycle, increased productivity, and increased revenue [7, 8]. a) b) Fig. 6. Boundary conditions: a) wheels torque, b) torque wheels and force of gravity 137

4 Numerical analyses were carried out in Autodesk Inventor FEA integrated module. Boundary conditions corresponding to the real were introduced to simulation. On the axes of the vehicle assigned torque (Fig. 6a.), and geometry has been assigned to the force of gravity (Fig. 6b. ). On the figure 7 we can see position and the pressure of human feet (orange arrows), force of gravity (red arrow) and torque wheels (yellow arrows). a) b) Fig. 7. Battle chariot simulation: a) pressure of human feet, b) all of boundary conditions The finite element mesh was applied on the modeled geometry consist of nodes and elements (fig. 8.). Local mesh control was made on the battle chariot platform. Fig. 8. The finite element mesh on the battle chariot geometry Material properties presented in table 1 entered into the simulation. Analyses were taken for a battle chariot made of different wood birch or oak. Tab. 1. Material properties Parameter Material Wood birch Wood oak Density 0.55 g/cm g/cm 3 Young's modulus 10.3 GPa 9.3 GPa Poisson's ratio Yield 56.3 MPa 46.6 MPa Tensile strength 6.3 MPa 5.5 MPa 138

5 The results of stress simulation are shown on figures 9 and 10. The arrows shows wheels torque, gravity load and feet load. Fig. 9. Results of FEM stress simulation - top view. Fig. 10. Results of FEM stress simulation Fig. 11. Results of FEM displacement simulation 139

6 Stress maps indicate the places most vulnerable to damage and wear. Maximum stress occurred in the tested model in the place where the axis contacts with the chariot chassis. The results showed that stress in the model, made of oak are slightly smaller. The results of analysis of displacement have been presented on the figures 11 and 12. By applying displacement magnification in graphical presentation shows that it is possible deformation of the axis of the battle chariot. Fig. 12. Results of FEM displacement simulation 5. Rendering of the battle chariot Real-Time 3D Photorealistic Rendering was realized after designing the model of the battle chariot in the software Autodesk Showcase application. Rendering takes into account real materials and realistic lighting and the surroundings of the model [9]. The effects of the work of the application Showcase illustrate figures 13 and 14. Fig. 13. The model of the battle chariot after rendering in Autodesk Showcase 140

7 Fig. 14. The model of the battle chariot after rendering 6. Summary The present technology of CAx was used in this work to bring closer questions from the ancient history. The realization of the 3D model allows see as objects looked, often well-known few and only in the two-dimension. Virtual models can be analyzed by using finite element method (FEM) in modern CAE programs, and give the answer to many engineering problems, for example, what material should be constructed in the proposed design. Computer simulation shown concentration of stress in a model, and location of displacement. With a computer model using rapid prototyping techniques one can print it on the printer 3D as an element of the equipment of historical study or can be the object of farther scientific investigations. References: [1] Rawlinson G.: The Seven Great Monarchies of the Ancient Eastern World Babylonia, Media and Persia, 2002, New York, J. W. Lovell. [2] Tadeusiewicz R., Korochoda P.: Komputerowa analiza i przetwarzanie obrazów, 1997, Kraków, FPT. [3] Kai Uwe Barthe: 3D-Data Representation with ImageJ, International Media and Computing, Berlin, Germany, [4] [5] [6] Hastings, J., Juds, M., Brauer, J.: Accuracy and Economy of Finite Element Magnetic Analysis, 33rd Annual National Relay Conference, April [7] McLaren-Mercedes: Vodafone McLaren-Mercedes: Feature-Stress to impress, [8] Służałek G., Kubica M., Bąkowski H.: Modelowanie zmiennych warunków eksploatacji dla skojarzenia kostka-płytka z wykorzystaniem MES. Mechanik nr 7, Warszawa, [9] Kubica M., Służałek G, Służałek M.: Metody komputerowe w badaniu historycznego wozu bojowego. Logistyka 3, Poznań,

8 Abstract This paper is about the Assyrian battle chariot, which is one of the most characteristic element of the historical military. To modeling the battle chariot used a reverse engineering (RE) technique in CAD Solid Edge and computer image analysis (CIA) in Met-Ilo and ImageJ applications. The numerical analysis which using finite element method (FEM) for calculations, were made in Autodesk Inventor software. 3D photorealistic rendering was realized after designed the model of the battle chariot in the Autodesk Showcase. Keywords: Battle chariot, Assyrian, three-dimensional model, modeling, computer aided design, 3D, FEM, computer simulation, reverse engineering (8pt) METODY KOMPUTEROWE W BADANIU HISTORYCZNEGO WOZU ASYRYJSKIEGO (10pt) Streszczenie Artykuł traktuje o Asyryjskim wozie bojowym, który jest jednym z najbardziej charakterystycznych militarnych elementów historycznych. Do zamodelowania wozu posłużono się metodami inżynierii odwrotnej (IO) zrealizowanej w programie CAD Solid Edge, użyto również komputerowej analizy obrazu (KAO) wykorzystując aplikacje Met-Ilo i ImageJ. Analizy numeryczne z zastosowaniem metody elementów skończonych (MES) zostały wykonane w Autodesk Inventor. Fotorealistyczny rendering zamodelowanej bryły wozu bojowego uzyskano w programie Autodesk Showcase. Słowa kluczowe: Wóz bojowy, Asyryjski, model trójwymiarowy, modelowanie, komputerowe wspomaganie projektowania, 3D, MES, metoda elementów skończonych, symulacja komputerowa, inżynieria odwrotna 142