Vol. 5 No. 2 (2020)

Published April 15, 2020


Materials Sciences

  • Fundamental Considerations for Finite Element Modelling of Rubber Material Tensile Test

    Aim of this research is to get familiar with the fundamental considerations for finite element modelling of rubber’s tensile test. Hyperelastic materials such as rubber are widely used in a variety of industries ranging from tire to aerospace for various structural applications. The most important feature of rubbers is their ability to experience substantial deformation under small loads and maintain initial configuration without noticeable permanent deformation after removal of the load.

  • Modern Applications of Aluminium Foams

    The implementation of aluminium alloy foam has more and more attention. Application of closed cell aluminium foam has made an impact in automobile and aerospace applications where crash energy absorption, vibration and weight reduction are obligatory [1,2,3]. The aluminium alloy foam is an advanced lightweight material providing high strength and stiffness at relatively low density. The technological use of aluminium alloy foam is difficult with the currently available technologies. In the case of open cell aluminium foams, the most common research areas for application are heat exchanger components, filters and sound damping elements [3]. The manuscript focuses on the manufacturing techniques of the aluminium alloy foams according to the application areas. First step is the investigation of the requirements for the application: what are the loads and the circumstances and why can we use aluminium foams. Second step is the knowledge of the producing methods of the foam or the component. And the last step is the investigation of the possible testing methods.

  • The Pressure Characteristics of the Released Gases from Sand Cores

    The core packages used for the production of castings are generally made from cores of different quality (no- bake phenol, HB-phenol, and HB-furan) and resin quantity, to meet the various requirements for the casting. In our research, the effect of the amount of resin on the pressure of the gases evolved from the cores was investigated. Experiments have shown that increasing the amount of resin has a different effect on different binder systems.

  • Effect of the Changes in Bulk Density and Granulometric Properties on the Strength Properties of the Moulding Sand Mixtures

    Foundry technology uses a lot of several natural materials. Sands use for preparing mixtures whereby making moulds or cores. Sand is defined as a granular, refractory major portion of mixture (90 – 98% in dependence on used binder). Sand properties depend on it has chemical and mineralogical composition; mainly particle size distribution and shape of grains and its size and sand surface texture. A comparative measurement of two quartz sand with different surface quality was carried out. Greensand mixtures were prepared to measure their permeability, compressive strength and wet tensile strength. The strength of sand mixtures has two main components. One of them is the cohesion of the binder; the other one is the adhesion between the binder and the foundry sand. The aim of this research is to determine the ratio of cohesion and adhesion within the strength values.

  • Polylactic Acid as a Potential Alternatives of Traditional Plastic Packagings in Food Industry

    Huge quantity of synthetic polymers is used as packaging materials in different fields of food industries. A significant part of these polymers applied as a primary, direct food contact construction. The scoped application area is the sweet industry. In this field Polystyrol (PS), Polypropylene (PP) and Polyethylene terephthalate (PET) have used but during the last fifteen years the usage of PET has been grown. In one hand the price of this material is efficient, form other hand the PET is the one of the most safe (for food industrial applications) petrol chemical plastic that can be used as primary or secondary food contact packaging material. To maximize the customer safety and minimize the environmental impact of traditional PET, a new bio-sourced and bio-degradable alternative polymer aimed to be used in this special food industrial segment. One of the potential alternatives is the Polylactic acid (PLA) that would be a possible substitute as it is compostable and produced from renewable sources and has good physical and mechanical properties [1].

  • Literature Overall of Fatigue Analysis Approaches of Vehicle Components Made of Rubber

    Generally, the most frequently used structural materials are metals which have high strength and stiffness. However, there are many cases when other important properties come to the front, as well as high deformation capacity with elastic behavior, high viscosity namely good damping effect. Due to its above mentioned properties, rubber is widely used in vehicle and automotive industry. Vehicle components made of rubber usually exhibit large deformations. Cyclic finite deformations generate temperature in hyperelastic materials. Furthermore it is necessary to take into consideration the effects of ambient temperature. The mechanical properties of rubber depend on temperature and temperature changes can accelerate chemical alteration processes which lead to the material deterioration and fatigue processes. Research on fatigue behavior and fatigue properties of rubber has a great significance for predicting fatigue life and improving durability of rubber products. There are several studies on the fatigue behavior of rubber-based materials, but there is less research in the fatigue life prediction considering the influence of temperature and temperature changes. First purpose of this paper is summarizing the influence of temperature and temperature changes on the fatigue behavior of rubber. The second purpose of this study is to provide an overview of the state of the art on the fatigue life prediction of rubber with primary focus on the different methods available for prediction of fatigue life under the influence of temperature and temperature changes.

  • Investigation on Double Oxide Film Initiated Pore Formation in Aluminum Casting Alloys

    The most common, and in fact, the most deleterious defects of aluminum casting alloys are the so-called double oxide films or bifilms, which have a central role in porosity formation, as they can easily unfurl and inflate into pores during the solidification of the alloys. Sr addition is generally used in the foundry industry for the modification of the eutectic Si phase of hypoeutectic Al-Si alloys. However, Sr microalloying usually leads to an increased pore formation tendency. As bifilms are preferred sites for pore formation, it should be expected that Sr additions have a significant effect on the number and/or the structure of double oxide films present in the melt. In this work, the relationship between Sr-concentration and the susceptibility to pore formation has been investigated through the evaluation of melt quality of melts which had different levels of Sr. The bifilm content of the melts was investigated by the analysis of K-mold specimens and X-ray computed tomography (CT) of reduced pressure test (RPT) samples. It was found that liquid alloys with a higher Sr concentration had a significantly greater tendency to pore formation, which can be explained by the presence of a larger number of bifilm defects in the liquid alloy.

  • Formation of Oxide Layers with Femtosecond Laser on Steel Surfaces for Color Marking

    With the appearance of ultrashort pulse lasers, the researchers have begun working on various laser marking technology. Atmospheric heating and ablation of a surface induce laser coloration of metal surfaces. However, their application is still problematic today in the industry. With the appearance of femtosecond pulse lasers, a new concept became available for color marking. This concept is based on the formation of laser-induced periodic surface structures (LIPSS) on metal surfaces. The purpose of this article is to summarize the literature of laser color marking with ultrashort pulse lasers.

  • Structural Investigation of Granular Composites by Modern Methods

    Structural investigations of polymer-based particulate composites were carried out using modern test methods. We had composite sheets with different compositions and different injection molding speeds. In the polypropylene matrix, three types of glass beads were mixed in three weight percentages. In our investigations, the granular composites were studied with a widely used examination equipment, scanning electron microscope (SEM) and industrial computer tomography (CT) as a modern diagnostic tools. The purpose of the study was to investigate the distribution and interfacial adhesion of glass beads.

  • Simulation of Hot Rolling by Cellular Automata

    Our research is focusing to one of the most complex and important production step of flat rolled products that is the simulation of hot rolling. During hot rolling two phenomena as work hardening and the process of regeneration of crystals has strong influence for physical properties of microstructure of aluminium alloys. It needs to be taken into account in case of rolling technology steps and development. When we talk about aluminium the dynamic softening in fact it is dynamic recovery that is followed by dynamic recrystallization. It goes in the same order of magnitude rate. But in steels the recovery has only a minor effect. Hot rolled and newly modified grain structure is influenced by these dynamic phenomena. Hot rolled grain structure goes through significant changes under further production steps like cold rolling and heat treatments. But aside from these intermediate production steps the microstructure that we get after hot rolling has significant effect for mechanical and grains structure of the final flat rolled product. Proper technology planning is essential that for cellular automata simulation method can ensure useable and good solution for the simulation of recrystallization.

  • Analysis of a Special, 3D Metal-Printed HPDC Tool Material

    High Pressure Die Casting (HPDC) is still the most productive metal-casting method of our time, however the more demanding are the industrial expectations, the more challenging it becomes to ensure the creation of the difficult cavity geometries and the thermal balance of the die-cast tool. New perspective is required, thus we can utilize high heat-conductivity tool steels and additive manufacturing technology.

  • Synthesis of Polylactic Acid (PLA) by Polycondensation Method

    The Polylactic acid (PLA) is compostable and natural renewable sourced plastic type. Its mechanical properties quite similar to the PET, therefore the PLA is a good alternative for strongly ruled food industrial application. The PLA only has one critical attribute – the relatively low glass transition temperature. According to the relevant literature the glass transition of PLA is in the range of 40-70°C. In light of this fact, this material can be used only in that segments of food industrial field where the packaging process temperature are under of the lower limit of Tg range. The actual Tg of a material is highly depends on the molar mass and material structure, therefore the molar mass and the structure of material should be designed according to the future requirements of application and procedures.

  • Investigation of the Granulometric and Mechanical Properties of Inorganic Used Sand

    This paper examines the use of a modified inorganic binder in metal-alloy casting. The results of investigations regarding the effect of reusing the used sand multiple times without reclamation. The technological properties of silica sand with inorganic binders were presented, two different temperatures were applied to make the used sands. After lump crushing the inorganic used sand was recycled in order to make a new sand mixture. Our work was focused on the effect of multiple usage of inorganic used sands on the mechanical and granulometric properties prepared with modified inorganic binder.

  • Pin on Disc Tests of Closed Cell Aluminium Foams

    Metal foams have a lightweight cellular structure with excellent mechanical and physical properties and are at the forefront of materials development for the automotive and other industries. Although metal foams are popular, they are still not sufficiently characterized thanks to their extremely complex structure. The aim of the research is the tribological investigation of closed cell metal foams with different production technologies and different cell sizes. The paper introduces the closed cell aluminium foams produced by direct foaming and gas injection and those raw materials. The Pin on Disc instrument and the most important parameters of the experiments are also presented.


Mechanical Engineering

  • Use of ANSYS Software for the Acetabular Cup Structure Analysis out of the Hip Implant

    Modelling the hip implant has been one of the most important researches over the past few decades. In addition, using the ANSYS software for this purpose is well-known procedure to understand the real reaction of the hip implant parts during the daily life of the installed part. This study is to focus on the practical part of the use of ANSYS software to analyse the performance of the hip implant through the feature of structure analysis available in the ANSYS. The research applies the static loads behaviour only with the help of the static structural analysis to view the advantages and the disadvantages of every design, which helps us estimate the implant’s behaviour. The study investigates the optimization of the acetabular cup using the lattice optimization along with the infill option available in the ANSYS software in order to optimize the stress and the fixture of the cup inside the pelvis.

  • Topology Optimization of Acetabular Cup by Finite Element Simulation

    Hip replacements typically consist of a four-part piece. Our research will focus primarily on the acetabular component. Several different types of materials can be used when creating a hip replacement implant ranging from plastic to titanium. Different materials are used to accommodate for allergic reactions or circumventing potential health risks. Aside from the material, the size of the components plays a factor in terms of durability; a larger diameter head might avoid dislodgement though it could increase wear and tear on the stems through constant friction. A patient’s force applied to the hip replacement is usually measured through a number of physical assessments. Finite element analysis (FEA), a computer-based method of data observation, allows for us to accurately simulate hip forces and their impact on the hip replacements. Through this, it becomes easier to predict and calculate the performance of specific designs. Generative systems can also be used to support performance analysis and optimization through assessing a multitude of cases, many of which apply in real-world scenarios. By applying both systems, we designed and modeled an acetabular cup that when measured decreased the mass from 129 grams initially down to 52 grams, a 60% decrease in total mass. Furthermore, the design we created lessened the trauma on the piece through distributing force across the entirety of the piece rather than specific segments only. This shows an increased durability and life expectancy when compared to usual acetabular cups.

  • Neutral Inhomogeneity in Circular Cylinder Subjected to Axial Load on its Lateral Boundary

    In this paper we consider the problem of single circular elastic inhomogeneity embedded within a circular cylinder whose curved boundary surface is subjected to surface traction acting on axial direction. We investigate the displacement neutrality of the coupled system of host body and inclusion. Neutral inhomogeneity (inclusion) does not disturb the displacement, strain and stress fields in the host body. The deformation of the considered inhomogenneous cylinder is antiplane shear deformation.

  • Application of Additive Technology in Precision Casting

    In this paper the surface of the prepared test specimens had been examined with light microscopy and surface roughness measurements. In order to improve the surface smoothness of PLA specimens, application of ethyl acetate was required. After this surface treatment, microscopic images were taken again. The melting and decomposition temperatures of the materials had been determined using derivatography. The chosen method was precision casting with gypsum molding. Also, the plaster molds had been burnt out according to the predefined melting and firing diagram. The measurement series shows that the samples produced by 3D printing can also be used in the field of precision casting. They provide greater freedom of design, more sophisticated pieces, and prototypes can be finished in a shorter amount of time.

  • Design of Manufacturing Process of Mould for Die Casting by EDM Technology with the Computer Aided

    At present, we cannot imagine a modern production process without computer support. At the same time, its integral part is the implementation of advanced and highly sophisticated production processes and technologies. Their aim is first and foremost to ensure quality production of products with high economic efficiency of the production process. EDM technology is one of the currently active progressive technologies. This is a technology that in practice is characterized by high product quality. The high quality of products not only through this progressive technology, but also other, whether conventional or progressive, is difficult to achieve without computer support. The aim of the paper is therefore to demonstrate the process of manufacturing a die-casting mould using progressive EDM technology using computer support.

  • Analysis of Conceptual Solutions of Universal Helical Geared Reducers

    Geared reducers are mechanisms designed to reduce the number of revolutions using geared elements and nowadays they present one of the most commonly used types of mechanical transmissions in mechanical engineering. Due to the different shapes of geared elements, there are different types of geared transmissions: helical, bevel, worm, special and combined transmissions.  This paper analyses only helical geared transmissions, since there is a great extent of whole this matter. Helical transmissions are analysed only with external helical gearing, since internal geared pairs represent a special and very large group of gears. Within the external helical geared transmissions, only torque transmissions are analysed, while the transmissions of motion are not analysed and they represent another large group of transmissions. Only universal gear reducers with axial, or almost-axial, parallel shafts are considered (two-stage and three-stage transmissions). Although, single-stage gear reducer produced with parallel shafts are not considered by the paper in order to reduce the area of researching. Gear reducers are most commonly delivered to customer with electric motor, known as motor geared reducer, and they are studied here extensively. Gear reducer can be also delivered without motor, only with input shaft. The basic aim of this paper is to present all characteristics and specificities of motor geared reducer in one place.

  • Design of Chip Conveyor

    The following article examines the design methodology of screw conveyors. The most significant steps are discussed concerning the design of the apparatus and its use in machine tools as a service component is explained.

  • Effect of the Friction Coefficient on Clinch Joints

    In this study the effect of the friction coefficient on the clinch joints was examined in experimental and numerical way also. The knowledge of the frictional behaviour during the mechanical joining (i.e. clinching) is important from the point of view of resultant geometry which is related to and influence the strength of the joints, and furthermore the maximal forming force is limited by the tool’s failure load which can be reach with a non-favourable frictional condition, as well the aesthetic aspect are also has an importance in some special cases (e.g. in automotive industry).

  • Influence of MTP on Surface Roughness and Geometric Accuracy of Machined Surface at WEDM

    Electrical discharge machining technology is one of the most precise machining methods. Therefore, even the smallest deviation of micro and macro geometry generally has a significant impact on the overall quality of products produced by this progressive technology. The quality of the machined surface after Wire Electrical Discharge Machining (WEDM) is influenced by a large number of factors, most of which are influenced by the Main Technological Parameters (MTP). The aim of the paper was to describe the results of experimental research aimed at assessing the impact of MTP for WEDM on the quality of machined surface in terms of geometric accuracy and roughness parameters Ra and Rz. The samples were made of high alloyed ledeburitic chromium-molybdenum-vanadium steel designated EN X155CrVMo12-1 on a Sodick AQ535 electroerosion machine. The tool used was a standard compact brass wire  0.25 mm with the designation Elecut Brass CuZn37.

  • Parameter Estimation of Drag Coefficient and Rolling Resistance of Vehicles Based on GPS Speed Data

    In this paper, a parameter estimation method of the model-based design approach is applied to estimate the drag coefficient and the rolling resistance coefficient of a vehicle. In fact, a constant-force parameter (c_const) and a velocity-square-force parameter (c_square) are in the vehicle model, and these result in the sum force applied along the translational DOF that models the vehicle. It is only an assumption that the constant force is the rolling resistance and the force proportional to the square of the velocity is the drag force of the air. Only GPS speed data is used for the estimation process. The conclusion is that parameter estimation is a good alternative when expensive measurement devices are not available to measure the force losses separately and directly.

  • Experimental Study on the Effect of the Geometry of Punching Tool on Clinch Joints

    In this study the effect of the punching tool’s geometry on aluminum alloy clinch joints is analyzed by experiments. Based on FE simulations the tip radius and the cone angle of the punching tool is changed, and their effect was analyzed by microscopic investigations and single lap tensile-shear tests.

  • Casting Issues of Thick-Walled High Pressure Die Castings

    Die casting is a manufacturing process for producing accurately dimensioned, sharply defined, smooth or textured surface metal parts. It is accomplished by injecting liquid metal at fast velocity and under high pressure into reusable steel dies. Compared to other casting processes, die casting is at the top end of both velocity and pressure. The high velocity translates into a very turbulent flow condition. The process is often described as the shortest distance between raw material and the finished product.

    Pre-fill is a process technique that is the result of significantly delaying the start of fast shot beyond the “metal at the gate” position. It can be stated as a percentage of cavity fill or as a distance beyond metal at the gate.

  • Principles of Three-Dimensional Computer Design for Understanding Impossible Figures

    For a better understanding of the impossible figures, it is advisable to use modern technological means by which the design of the geometry of the models gives a complete understanding of how they are made. Computer-aided 3D design completely solves this problem. That is, on the one hand, the ultimate visual variant of impossible figures is created, on the other hand, there is the possibility for real manipulation, movement, rotation and other models of space. In this study, 3D models of impossible figures are fully constructed, which are applied in the educational process in order to develop logical thinking. The steps of creating 3D geometry using open source software Blender 3D are described in details.

  • Compliant Mechanisms in Progress and Development Of Modern Technology

    In this paper, the compliant mechanisms will be presented. There will be presented some representative works that have brought progress and development in modern technology. Examples will be presented from simple concepts such as a tweezers, staples, to mechanical clutches, pointer and micro-compliant mechanical structures.

  • Analysis of Abrasion of Hot Metal Powder Spray Coated Layer

    By the application of the tradicional overhead welding and the different powder coating technologies results a new surface with improved abrasion resistance, we can optimize the dimensions of the part or we can rebuild some surface as a kind of repairing technology. By application of this technology we can avoid the replacement of the total expensive parts of the structure. Opposite to the tradicional overhead welding in this case there will be diffusion connection between the raw material and the surface coating, this connection type shows several positive properites. Our goal is to investigate the abrasion resistance of the coating. In this article we would like to introduce our results of the abrasion test by apllication of different powder coatings.


Vehicle Engineering

  • Survey of the Application Fields and Modeling Methods of Automotive Vehicle Dynamics Models

    In this paper, a review is presented on automotive vehicle dynamics modeling. Applied vehicle dynamics models from various application fields are analyzed and classified in the first section. Vehicle dynamics models may be simplified because of different reasons: several control/estimation/analysis methods are suitable only for simplified models (e.g. using control-oriented models), or because of the computational cost. Detailed/truth models of vehicle dynamics represent another field of vehicle dynamics modeling, these models play an important role in the virtual prototyping of vehicles. In the second section, the main modeling considerations of vehicle dynamics are presented in longitudinal, lateral and vertical directions. Various physical effects must be considered in the case of vehicle dynamics modeling, a lot of these effects are significant only in a specific direction of the vehicle body, which is the main potential of model simplification. The section presents vehicle modeling considerations in all of the three translational directions of the vehicle body.

  • Calculations of Performance Losses for Automobile Vehicles

    Vehicle-energetic-models are used to analyze the performances and when a comprehensive structure is established even optimization could be done. For these kinds of models, the losses of the vehicles have to be known. These losses could significantly effect of the vehicle fuel consumption. From these losses the rolling resistance, drive elements and aerodynamic drag are discussed. This paper reviews some of the literatures that describes the calculation methods and gives us some idea about the degree of their value. Our further goals are to have an UpToDate loss coefficient dataset and calculation methods for further vehicle-energetic modelling.

  • Trends in Greenhouse Gas Emissions and Renewable Energy Policies in the EU and USA, with Special Emphasis on the Transportation Sector

    The aim of this work is to review recent trends in the field of greenhouse gas (GHG) emissions and renewable energy policies of the European Union and the United States of America. During the last few decades, there was a significant shift within the political attitude towards these fields, therefore important changes were realized in the electricity production and the climate policy. In the present paper, we discuss the current situation focusing on the transportation segment.

  • Review of Modern Vehicle Powertrains and Their Modelling and Simulation in MATLAB/Simulink

    Thanks to technological advances and environmental standards, as well as changing usage patterns, road vehicles are constantly developing. Electric and hybrid vehicles are playing an increasingly important role in today’s road transport. The most significant changes are probably in the powertrain of vehicles. The efficiency of internal combustion engines increases while their emissions continue to decline. In addition, high performance electric motors, batteries and even fuel cells play an increasingly important role in hybrid and electric vehicles. In this publication, we review the drive systems of current modern vehicles and the types and characteristics of their major components. We also review the available models and computer programs for their simulation, focusing mainly on MATLAB/Simulink applications. Based on this, we can develop our own models and simulation programs which will help us to perform different driving dynamics simulations and to compare the performance, dynamic and energetic characteristics of these powertrains and their components to each other.

  • Review on Construction Procedures of Driving Cycles

    The goal of this paper is to give an overview of the literature of construction techniques of driving cycles. Our motivation for the overview is the future goal of constructing our own driving cycles for various types of vehicles and routes. This activity is part of a larger project focusing on determination of fuel and energy consumption by dynamic simulation of vehicles. Accordingly, the papers dealing with sample route determination, data collection and processing, driving cycle construction procedures, statistical evaluation of data are in our focus.

  • Vehicle Dynamic Simulation Possibilities Using AVL Cruise M

    In most cases, when creating vehicle dynamics simulations, we need software that can speed up model creation and simulation. There are many programs on the market for this purpose, but they have different knowledge and user interfaces. We present in this article briefly introduces the use of one of the market's leading vehicle simulation software, the AVL Cruise M.

  • Design and Implementation of BHN Testing Equipment To Measure Remaining Stress Of Wheelset Parts (Tie Rod and Stabilizer Bar)

    Nowadays in the automotive industry both production and service, requires accurate lifetime calculations. Today we have big amount of theoretical background and nowadays the importancy of technical and industrial databases become more and more important. By materials scientific and fracture mechanics aspects are well covered, but the remaining stresses which are present in every step of production, we can not clearly identify the origin of them. There are different paralell methods to mesure them, but the application of different methods are depending on the engineers, and their expreiences at the company. This part of the analysis is not standardised yet, so there are differences even in the same company. 

  • Analysis of Driving Data of Lorries on a Certain Route

    In this paper the development of a driving cycle for lorries traveling a certain route is presented. A typical transportation route has been selected, which used by lorries instrumented with the proper data-collecting equipment. We used these on-board units to collect data over a long time period in the real-life traffic. We filtered the collected data, and carried out a statistical evaluation on the basis of the measured data.

  • Applicability of Optimization Methods in the Design of Automotive Rubber Products

    Size, shape or topology optimization are widely used to fulfil the requirements in the design process of rubber products. In many cases, the shape of the product is very complex and comes into contact with other components during operation. It is commonly subjected to large deformation for which the rubber shows strongly nonlinear behaviour. For this complex problem analytical solution is not available, thus finite element method could be used in which the analysis running is a time consuming process. The object of my research is to compare the efficiency and computational cost of different optimization algorithms. This article focuses on the applicability of various optimization methods in the field of automotive rubber goods. Direct search optimization and surrogate model optimization methods will be introduced.


Engineering Education

  • Planning, Implementation and Experience of a Skill Development Workshop

    The development of students' different skills, both in primary and secondary schools, plays an extremely important role. The development of this age group in the form of playful activities can be effectively implemented. The article discusses the pedagogical background and planning steps of such occupations. A specific example of algorithmic skill development will be presented. We also list the experiences we have gained from holding this workshop, which may be helpful for the future development of the session.

  • The Role of the Geometric Transformations in ihe Formation Process of the Function Concept

    The concept of the function and the different geometrical transformations play important role in the technical sciences. Since geometric transformations are functions, so-called geometric functions, therefore, in this study, we present a possible way of that, how can we apply the animations of the geometrical transformations which are made with GeoGebra in the formation process of the function concept in the primary and secondary school level.

  • Development of engineering and innovation skills

    Spatial visualization skills have an important role in teaching and learning of engineering studies. Many studies have shown that there are correlations between various measures of spatial skills and performance in particular Science, Technology, Engineering and Mathematics (STEM). Many engineering students have problems with solving mathematics problems, using mathematical models in practice, imagining a spatial figure and therefore to solve the spatial geometry exercises, so development of these abilities is very important. We have developed special tools and worksheets for development of engineering and innovation skills.

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