Showing papers in "Periodica Polytechnica Mechanical Engineering in 2008"

Producing metal matrix syntactic foams by pressure infiltration

Abstract: This paper presents the possibility of syntactic foam production by pressure infiltration technology. Syntactic foams have low density and relatively high strength. Therefore they can be the material of many important parts in automotive technology or in aviation. The parameters of infiltration were studied and physical and mechanical investigations were performed. Microscopic investigations showed almost perfect infiltration at the applied infiltration pressure. The densities of the foams were significantly decreased. Low density ensures good specific properties and economical energy consuming in the case of moving the parts. Syntactic foams showed a plateau region in their upsetting diagrams and absorbed a high energy during upsetting. The effect of aspect ratio was also investigated. Specimens with higher aspect ratios showed lower peak stress, lower plateau level and higher modulus of elasticity.

Human Weaknesses and strengths in collaboration with robots

Abstract: This paper describes the importance of the incorporation of ergonomics, human factor, errors analysis and cognitive engineering approaches in the design of human-robot systems, how consideration of these subjects help designers and workers to avoid hazardous situations and make human-robot interaction in vicinity more effective, reliable and safe. Basing on acquired knowledge and guiding by acquired knowledg e we propose our trial application for disassembly cell.

Energetical optimization of water distribution systems in large urban centers

Abstract: In the present conditions of water distribution towards the users by pumping, in large urban centers, the reconsideration of the structure and functioning principles of the distribution systems, from the point of view of the energetical optimization, becomes a necessary and major problem, which can be solved by a new structural design. This paper presents and analyses in a detailed manner, giving numerical examples, certain optimization methods and solutions for the distribution systems, with a view to diminishing the pumping energetic consumption, using interior potential elements, ascertaining the energetical and economical efficiency.

FE simulation of the hysteretic friction considering the surface topography

Abstract: Present study investigates the hysteretic rubber friction in case of ideally rigid, rough surfaces sliding on a rubber plate. To characterize the topography of the rough surface stylus and AFM measurements were performed. Two- and three-dimensional models were created in order to predict the hysteretic rubber friction by finite element analysis. The characteristic wavelengths and amplitudes of the engineering surface studied were determined and simple, two-dimensional roughness models with different length scales were constructed. In 3D, NURBS surface was used to model the surface roughness. In order to describe the non-linear and viscoelastic material behaviour of the observed EPDM rubber, two-parameter Mooney-Rivlin material law combined with 40-term generalized Maxwell-model has been used. The effect of sliding speed, temperature and geometric parameters of the roughness model were also investigated.

Measuring the effects of some laser parameters on the surface and near surface region of laser treated cast iron cylinder bore

Abstract: The environmental and polluting materials emission standards in Europe are going to be always stricter, so in order to keep up with them, one of the largest European automotive manufacturers performs a laser treatment on the cylinder bores of their combustion engines. In this article the laser treated layers of cast iron cylinder bores with lamellar graphite are investigated with a FISCHERSCOPE^\unhbox \voidb@x \hbox \textregistered HM2000 XY microhardness measurement system and with a FEI Nova Nanolab 600 SEM/FIB dual beam scanning electron microscope (SEM), equipped with focused Ga-ion beam source. Four samples treated by two different laser sources in three configurations were investigated.

Thermophysical properties of porous mineral-resin composites determined by a transient measurement technique

Abstract: Due to the continuous development of material sciences there is a constant demand to determine the thermophysical properties of new materials especially in the field of polymer technology. The temperature dependent volumetric heat capacity and thermal conductivity of two different porous mineral-resin composites were measured simultaneously by a transient technique developed by the authors. The technique includes one transient measurement and a genetic algorithm based evaluation method. We shortly present the principle of the technique and the measurement process and results for the two materials. The applied measurement technique can reduce the time consumption and the costs of the measurements compared to other well-known methods.

Investigation of the load transmission in the toothing of a flat wheel harmonic gear drive

Abstract: The function principle of the flat wheel harmonic gear drive is similar to the basic principle of the classical harmonic drives. The flexible and the rigid gear of the drive are coaxial flat wheels. The rotating wave generator deforms periodically and elastically different portions of an annular face gear on the flexible member in axial direction into engagement with teeth on an annular face gear on the rigid member. The numbers of teeth of the face gears are different. An analytical method is introduced, that investigates backlash conditions of flat-wheel harmonic drives. The tooth flanks were approximated by planes. The numbers of the connected teeth taking part in the load-transmission and the tangential component of the acting force on them in the range of tooth engagement are dependent on backlash. Finite element investigations were launched at different levels of torques even in case of preloaded flexible gear.

Magnetic saturation of poly(dimethyl-siloxane) matrix composites based magnetorheological elastomers

Abstract: The most common used parameters in applications of magnetorheological elastomers are characteristic data of magnetization curve. Vibrating sample magnetometer (VSM) is a unique technique to record the magnetization curve of small samples. From measurement data the further calculations have to be done for determination of the saturation magnetisation as among other factors some materials can not be saturated with this VSM, but the saturation magnetization can be determine as the fitted curve´s parameter. It was found, that the saturation magnetisation depends on filling factor (as rate of components). To get composite saturation magnetisation components saturation magnetisation in proportion of their weight percentage should summing-up. The knowledge of error limits presents a usable tool for further examination.

Pilot test and theoretical analysis of evaporation of one and more component fuels

Abstract: The evaporation rate of different liquids was measured by exposing small droplets to an intensive radiative heat load. Several liquids were used namely water, 1-, 2-butanol, 1-, 2-propanol, isobutanol and rape seed oil. A mixture of alcohol and rape seed oil (20/80 vol%) was also analysed. The sample results show the evaporation of different fractions of liquid for different wall temperatures and a constant counter flow of nitrogen.

The amount of extractable heat with single U-tube in the function of time

Abstract: Heat pumps can be used for different purposes in building services. They obtain heat from the environment of lower temperature (e.g. air, water, earth) and transfer it into the building at a higher temperature. The heat of the ground can be the primary energy source of the heat pumps. We extract this heat with the help of ground heat exchangers. These exchangers are the U-tubes, which are either single or double. In our paper we deal with the problem of the extractable heat from the ground with these heat exchangers. We show a simple calculation method for the temperature change in the heat carrier fluid and for the overall thermal resistance of the U-tube.

Influence of the infiltration pressure on the properties of MMC wires

Abstract: MMC wires are ceramic fibre reinforced metal matrix composites produced by continuous infiltration method (Blucher process). During the MMC (Metal Matrix Composite) wire production it is possible to change the applied infiltration pressure which overcomes the poor wetting behaviours between the ceramic reinforcement and the molten metal. The changing of infiltration pressure has influence on the mechanical properties by the porosity of MMC wires.

A transformation technique for efficient shape optimization in CAD/CAE environment

Abstract: In the course of shape optimization in an integrated CAD/FEM environment, finding of appropriate bounds of the shape parameters, has a principal importance: on one hand, non-recoverable geometries and structural model are to avoid, on the other hand, valid combination of shape parameters must not be excluded because they may include the optimum. To resolve this contradiction, a transformation is introduced to project the variable dimensions of the geometry onto the n dimensional unit cube, so these normed design variables are used in the course of the optimization. In simpler cases this transformation can be derived from the limit relations of the geometry construction as it is shown on the optimization example of a handhold used in public transport.

Analysis of colour moiré phenomenon in colour space

Abstract: Moire topographic technique is widely used for three-dimensional surface reconstruction. One of the main problems is determination of the absolute order of a fringe for finding the depth difference between two points in moire patterns, i. e. convex and concave surfaces distinction. Most solutions of the problem are very complicated; also they usually require several moire images. Application of colour-encoded gratings in projection moire method allows solving the problem simply and quickly. The authors analyze the information that contains in colour moire fringes and estimate its effectiveness. With this purpose device independent simulations for colour formation of one moire fringe in colour space by different conditions were made.

Human wavelength identification, numerical analysis and statistical evaluation

Abstract: Monochromatic wavelength identification never had such significance as today when several lighting applications favor the use of light emitting diodes as light sources. People with normal color vision designing the color appearance of a monochromatic lighting solution usually do not consider the different appearance of these stimuli for color blind. In our study we have measured the monochromatic color identification of more than 100 observers with different types of color vision and we have found significant differences in their color identification. The results should be implemented in all illumination design where the use of LEDs is considered.

Analysis of energy consumption of air handling units based on probability theory

Abstract: The existing building stock in Hungary accounts for over 40% of total energy consumption of which heating and air-conditioning systems use represents the most. International and national regulations encourage cutting down the energy consumption in buildings. For this reason it is important to determine energy consumption exactly. In view of outdoor air parameters (temperature, humidity and enthalpy) variation a new calculation method was necessary to set up for evaluating of energy consumption of air handling units. In consideration of the fact that outdoor air condition values can be regarded as a probability variable we have worked out a new evaluation method of energy consumption of air handling units based on probability theory. The research work was carried out by scientific methods.

Geothermal energy mining

Abstract: In Hungary the geothermal gradient is relatively high which means that there are high-temperature rocks underground. In theory the extraction of the heat of the rocks would be a perfect solution to ensure the heating of the country. The mathematical model written in the essay demonstrates that the exothermic system - consisted of two wells - is operable. The re-pressing was proved to be highly possible by many measurements, so the technological solution is ensured. In the USA scientists developed the hot dry stone method, when they make path for the fluid into the stones. Different system is used in France, when they repumping the fluid into the leaky stone.

The effect of the manufacturing parameters on the surface hardness and shrinkage of polyurethane integral skin foam products

Abstract: The effect of the manufacturing parameters on the surface hardness and shrinkage of polyurethane integral skin foam products has been investigated. Three production parameters were examined in details with the Taguchi method of experimental design, and the connection between these factors and the surface hardness were estimated by regression analysis. Furthermore the relation between the average density, as one of the key-properties of the polyurethane integral skin foam products, and the surface hardness and the shrinkage have been studied. Finally, the two time-dependent properties, the volumetric shrinkage and the surface hardness, have been investigated.