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.

No abstract

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.

This study investigated the correlation between bone characteristics, the design of orthodontic mini-implants, the pull-out force, and primary stability. This experimental in vitro study has examined commercial orthodontic mini-implants of different sizes and designs, produced by two manufacturers: Tomas-pin SD (Dentaurum, Ispringen, Germany) and Perfect Anchor (Hubit, Seoul, Korea). The total number of 40 mini-implants were tested. There are two properties that are common to all tested implants—one is the material of which they are made (titanium alloy Ti-6Al-4V), and the other is the method of their insertion. The main difference between the mini-implants, which is why they have been selected as the subject of research in the first place, is reflected in their geometry or design. Regardless of the type of implant, the average pull-out forces were found to be higher for a cortical bone thickness (CBTC) of 0.62–0.67 mm on average, compared to the CBTC < 0.62 mm, where the measured force averages were found to be lower. The analysis of variance tested the impact of the mini-implant geometry on the pull-out force and proved that there is a statistically significant impact (p < 0.015) of all three analyzed geometric factors on the pull-out force of the implant. The design of the mini-implant affects its primary stability. The design of the mini-implant affects the pulling force. The bone quality at the implant insertion point is important for primary stability; thus, the increase in the cortical bone thickness increases the value of the pulling force significantly.

No abstract

No abstract

Difference between industrial designer and product designer is not precisely defined. There is a lot of discussions and misunderstandings about these two professions. What is the job of industrial designer and what is the job of product designer? This question if often asked from people, which want to hire someone to design a new product for them. Through this research, same real-life design contest is given to group of students from Faculty of Mechanical Engineering, Department of Mechanical Design, at Industrial design course and to group of students from Academy of Fine Arts, Department of Product Design as product design project. Goal of the contest was to design an upholstered chair for indoor use with a modern and refined style. Goal of this research was to find some unique characteristic of designs from industrial designers and product designers. Resulted designs were evaluated analysing the fulfilment of the requirements criteria defined by contest and analysing additional criteria, which is important for new product design. Analysing the resulted designs some important conclusions are made. Most important conclusion is that industrial designer can be product designer but product designer cannot be industrial designer. For product design, engineering knowledge is not necessary, but for industrial design, it is most important.

The stiffness and stress analysis of beech wood laminated straight and curved cantilever beam is performed in the paper. Analysis was conducted layer by layer on the laminated beams with different veneer compositions. Finite element analysis is carried out with a '2D linear elastic model' for orthotropic materials. Analytic stiffness and stress evaluation is carried out by a 'transformed cross section method'. The influence of the veneer fiber orientation, veneer position, and thickness on the mechanical properties of laminated wood and the possibilities of both used methods for design of different shape of laminated wood have been analyzed. The results revealed that the laminated wood beam is stiffer when the outside veneers have longitudinal orientation in span direction or the thickness of outside veneers with longitudinal orientation is greater and that longitudinally oriented veneers sustain larger stress than veneers with tangential orientation. The results obtained by both used methods confirm that it can be used to achieve behaviour analysis of laminated wood in rectangular form. Curved forms require more complex analysis, but the methods can be used to achieve approximate data. The numerical in-plane stress analysis that applied to curved beam is not capable to calculating radial (interlaminar) stress.