This paper describes a structural analysis of the CAD model three versions fixators Sarafix which to explore the possibility of introducing composite materials in the construction of the connecting rod fixators comparing values of displacement and stiffness at characteristic points structure. Namely, we investigated constructional performance of fixators Sarafix with a connecting rod formed from three different composite materials, the same matrix (epoxy resin) with three different types of fibers (E glass, kevlar 49 and carbon M55J). Results of structural analysis fixators Sarafix with a connecting rod made of composite materials are compared with the results of tubular connecting rod fixators made of stainless steel. After comparing the results, from the aspect of stiffness, we gave the final considerations about composite material which provides an adequate substitution for the existing material.

The development process of the knowledge-based engineering (KBE) system for the structural size optimization of external fixation device is presented in this paper. The system is based on algorithms for generative modeling, finite element model (FEM) analysis, and size optimization. All these algorithms are integrated into the CAD/CAM/CAE system CATIA. The initial CAD/FEM model of external fixation device is verified using experimental verification on the real design. Experimental testing is done for axial pressure. Axial stress and displacements are measured using tensometric analysis equipment. The proximal bone segment displacements were monitored by a displacement transducer, while the loading was controlled by a force transducer. Iterative hybrid optimization algorithm is developed by integration of global algorithm, based on the simulated annealing (SA) method and a local algorithm based on the conjugate gradient (CG) method. The cost function of size optimization is the minimization of the design volume. Constrains are given in a form of clinical interfragmentary displacement constrains, at the point of fracture and maximum allowed stresses for the material of the external fixation device. Optimization variables are chosen as design parameters of the external fixation device. The optimized model of external fixation device has smaller mass, better stress distribution, and smaller interfragmentary displacement, in correlation with the initial model.

The paper provides mathematical model for solution of lubrication problem in case of mixed friction, i.e. when total contact load of two bodies is partially transmitted through the peaks of roughness of a solid contact, and partly through the pressure generated in the oil film. Mathematical model used for solution of lubricated contact with mixed friction is based on the bases of thermoelasto-hydrodynamic (TEHD) theory of lubrication expanded by equation of solid bodies contact. Based on the presented mathematical TEHD model own computer program was developed, which enables rapid analysis of tribological parameters at the point of contact of two bodies (the thickness of the oil film, the pressure transmitted by solid body, the pressure transmitted by fluids, temperature in the oil film) in the function of working conditions parameters.

This article presents architecture of integrated intelligent computer-aided design system for designing mechanical power-transmitting mechanisms (IICADkmps). The system has been developed in C# program environment with the aim of automatising the design process. This article presents a modern, automated approach to design. Developed kmps modules for calculation of geometrical and design characteristics of mechanical power-transmitting mechanisms are described. Three-dimensional geometrical parameter modelling of mechanical power-transmitting mechanisms was performed in the computer-aided design/computer-aided manufacturing/computer-aided engineering system CATIA V5. The connection between kmps calculation modules and CATIA V5 modelling system was established through initial three-dimensional models – templates. The outputs from the developed IICADkmps system generated final three-dimensional virtual models of mechanical power-transmitting mechanisms. Testing of the developed IICADkmps system was performed on friction, belt, cogged (spur and bevel gears) and chain transmitting mechanisms. Also, connection of the developed IICADkmps system with a device for rapid prototyping and computer numerical control machines was made for the purpose of additional testing and verification of practical use. Physical prototypes of designed characteristic elements of mechanical power-transmitting mechanisms were manufactured. The selected test three-dimensional virtual prototypes, obtained as an output from the developed IICADkmps system, were manufactured on the device for rapid prototyping (three-dimensional colour printer Spectrum Z510) and computer numerical control machines. Finally, at the end of the article, conclusions and suggested possible directions of further research, based on theoretical and practical research results, are presented.

This paper presents the development and experimental verification of a generative CAD/FEM model of an external bone fixation device. The generative CAD model is based on the development of a parameterized skeleton algorithm and sub-algorithms for parametric modeling and positioning of components within a fixator assembly using the CATIA CAD/CAM/CAE system. After a structural analysis performed in the same system, the FEM model was used to follow interfragmentary fracture displacements, axial displacements at the loading site, as well as principal and Von Mises stresses at the fixator connecting rod. The experimental analysis verified the results of the CAD/FEM model from an aspect of axial displacement at the load site using a material testing machine (deviation of 3.9 %) and the principal stresses in the middle of the fixator connecting rod using tensometric measurements (deviation of 3.5 %).The developed model allows a reduction of the scope of preclinical experimental investigations, prediction of the behavior of the fixator during the postoperative fracture treatment period and creation of preconditions for subsequent structural optimization of the external fixator.