Fulltext search in archive

This article deals with unconventional materials usage in design of vehicle bodies. Main focus is on sandwich materials (with honeycomb structure) for walls of the main body. These panels are designed from polypropylene. Joining of theses sandwich panels is also solved here by special aluminium profile. Virtual simulations and stress evaluation are used methods for design evaluating. Research is focused also on material properties testing. Tested are sandwich materials and also connecting aluminium profiles. All material properties and testing principles are here clearly described. Lower weight of vehicle body leads to possibility of floor optimization. Welded frame of floor can be lighter and strength of floor is also evaluated here. All these steps lead to lighter design with economic benefits for producer.

We need to create appropriate and effective numerical (FEM) model to optimize properties of a composite product. The creation and evaluation of an efficient numerical model that could be used for an analysis of layered composite is the aim of this work. The model has to be able to take into account the properties and layout of the individual layers and must allow effective change of these parameters; thickness, material and number of layers especially. Various models of the same product are created and compared. The models differ in the type of used FEM elements. The results of models (deformation primarily) were compared with the result of analytical computation. Further, time and computational requirements of individual models are also evaluated. Element types used for investigated models are: 1D elements, 2D plane stress solid elements, 2D plane strain solid elements and shell elements. Models created form 1D and shell elements showed a close agreement with the analytical solution, and they provide the appropriate tools for the definition of layered structures and for the analysis of results.

The wear of rails and rail wheels is important problem in rail traffic. The change of the shape of the wheel profile has not only a great influence on the dynamic properties of the vehicle (like stability, safety by passing curved tracks, etc.), but also affects the ride comfort of passengers and environmental insults. In extreme cases it can cause rail derailment, which is unwanted status. For these and other reasons, great effort is brought to create a software, which would be capable to compute the wear of a rail wheel profile. The presented article demonstrates how the change of the rail profile influences the resulting contact stresses. The wheel and rail geometries were created by using the CAD software CATIA. For the creation of the rail profile, the PYTHON programming language was used, because the imported .step file caused inaccuracies during import. The contact stresses were computed by using the commercial FEM software ABAQUS, and the results were compared with other methods which are used to calculate contact stresses.

From the initial feedstock to the final product, the manufacture of forged parts is a highly complex process in which a large number of technological factors play their role. These factors are associated with temperature and the amount and rate of deformation. Developing a manufacturing route often involves major effort being put into finding optimum production parameters with respect to boundary conditions which mainly comprise customer requirements and financial aspects. In order to determine an optimum set-up for forging production or to introduce a new technology, a number of essential steps must be taken and sometimes repeated. In this context, material-technological modelling is a promising and effective tool which enables numerous optimization phases to be carried out in a laboratory environment without disrupting the operation of production lines in forge shops. The present paper describes material-technological modelling of production of a closed-die forged part of microalloyed steel involving the use of controlled cooling. The objective of this investigation was to define the processing window for microstructure evolution, depending on the forging temperature, the amount of deformation, and the rate of cooling from the finishing temperature.

This paper deals with the description of a mechanism for calibration vehicle axle scales with a loading capacity up to 10 tons and strength analysis of its selected part. The strength analysis will be carried out in ADINA software and this analysis results will be used to check the safety of the structure and in case of exceeding the permissible stress, deformation, etc. This analysis results will form a benchmark material for optimisation of this structure. The next step of this issue will be strength analyses of all important parts, i.e. boxes with weights and upper girder. After performing these calculations and the resulting optimisation, the prototype production will be feasible.

This article is belonging to the publication series, which we published in the previous issues of this journal and there are described the most important and innovative research and development design solutions and computational procedures as part of European structural funds project. The main object of article is the strength test of new design of freight bogie frame through FEM analysis. For the calculation of the analyzed parts of the bogie through finite element the program ANSYS was used. Results of calculations prove, that new designed construction of the bogie frame satisfies strength conditions.

The aim of the research was to evaluate the lapping length, the adhesive bonded surface treatment and the influence of the filler in the form of the aluminium microparticles on the adhesive bond strength. The alloy AlCu4Mg was the adhesive bonded material bonded by means of a two-component epoxy adhesive used in construction of machines. The filler in a form of aluminium microparticles was added into the adhesive. Laboratory experiments were performed on normalized testing samples of alloy AlCu4Mg prepared under standard ČSN EN 1465. Within the research three various treatments of the adhesive bonded surface were evaluated, i.e. without the surface treatment (WT), mechanical treatment of the surface (MT) and mechanical and chemical treatment of the surface (MCHT). The adhesive bonds without the adhesive bonded surface treatment (marked as WT) reach the smallest adhesive bond strength. When adding the filler in the form of aluminium microparticles (10 vol. %) the adhesive bond strength was increased of about 12%.

Fractographic methods derive their knowledge from Euclidean geometry, set theory, metric theory and chaos theory. In engineering technology, the fractography is primarily used for modeling of fatigue and intergranular fractures. As such defects are not smooth due the principle of their origin, they cannot be described using ordinary mathematical tools. However, if the conditions of self-similarity are met, fractal geometry means can describe various irregular, incomprehensible, crooked or fragmented geometric shapes. Fractographic description of the fracture profile allows more accurate quantification of fractures and it also enables identifying possible causes of their initiation. This study contains several examples of specific cases of Cr-Ni steel failures and a basic explanation of their fractographic description.

Fatigue properties of the constructional materials belong among the very important material parameters, mainly because they are very closely related with the total fatigue life of the part. Knowledge of the boundary between limited and infinite (endurance) life represents a truly very important fatigue parameter. This paper deals with the influence of pre-deformation on aluminium alloy AW-5182 fatigue properties. These tests were performed under fully reversed harmonic cycle (max/min stress ratio R = -1). As a major aim there was determination of so-called S-N curves (stress vs. number of cycles) and their mathematical description by the Basquin's equation via fatigue strenght coefficient σf' [MPa] and fatigue strength exponent b [1]. Measured S-N curves gave a basic overview about the basic pre-deformation influence on the alluminium alloy AW-5182 fatigue properties.

Friction is closely related to every moving machine and fundamentally affects efficiency and service life. Wear tracking of moving and non-moving parts of the engine mechanism is important for expressing the wear trend. The wear and tear trend is specific for gasoline engines in urban traffic. The increase in the number of abrasive non-ferrous particles (Al, Cu, Ni, Cr, Sn, Si) is monitored in Škoda Octavia vehicles. The statistical evaluation of nomogram the wear and the determination of the optimum oil change interval of a vehicle group with sparkignition engines are performed for individual non-ferrous particles. The main aim of the article is to propose and verify the method of determination of the optimal oil change interval using Atomic Absorption Spectroscopy, Thin Layer Chromatography and using limit values of discriminatory analysis. On the basis of the results of the analyses, it is clear that the oil change interval by the manufacturer is inadequate and the oil level must be monitored.

At present, with the development of electric vehicles, great attention is paid to alloys which have very good electrical conductivity, corrosion resistance and resist to high temperatures. These alloys include aluminum bronzes. The electrical conductivity is the higher the finer is the grain or the less it contains almost non-conductive oxides, non-metallic inclusions, porosity, etc. Aluminum bronzes are foundry alloys that exhibit good electrical properties, very good sliding properties at high mechanical values, are resistant to corrosion and heat, have high resistance to acids and alkalis, so they are successfully used to work in aggressive environments. Aluminum increases strength and hardness, approximately 10 wt. % Al dissolves in copper, the alloy structure consists only of crystals α (cubic surface centered grid). Higher Al content also produces fragile crystals γ2 (Cu9Al4) and the alloy is harder and more fragile. The properties of aluminum bronzes with the structure of crystals (α + γ2) have a considerable influence on the cooling rate. Foundry bronzes are also used for more loaded wreath of gears, screw wheels, pump seats, impellers and distributor wheels, heavy load bushings and plain bearings.

This study presents the Resistance Spot Welding (RSW) process of Deep Drawing Steel (DDS) optimization using Response Surface Methodology (RSM) and Simulated Annealing (SA). The RSW process was optimized to obtain the maximum shear force the DDS can withstand. The experiment was conducted under various DDS thickness, welding time and welding current. The experimental processes were conducted using L16 orthogonal array, which has nine rows. The processed DDS was tested using tensile testing machine which will generate the amount of shear force that it can withstand. RSM is first used to develop a suitable mathematical model. The model was tested using Analysis of Variance. From the test result, the model then was used as the objective function of SA. Based on the result, the maximum shear force can be well predicted, which leads to reduced cost and improved welding quality.

An extensive experimental investigation was carried out to study the performance of Stellram Indexable Milling Cutter (XDLT09-D41), used for rough down milling of Ti-6Al-4V alloy. The machining performance was investigated for small depth of cut under different combinations of the operating parameters; like application of high pressure coolant and their impact in terms of tool wear, tool life, thermal crack, etc. The range of operating parameters were broadened, to get comprehensive results in comparison with previous work. The critical observations of the tool wear were at the tool tip/nose and at the bottom part of tool; where thermal deformations were most likely to be propagated with time. It has been noticed that the flank wears were owing to scratching of the cutting chips and diffusion wears were because of high thermal stresses at the bottom of the cutting tool. These findings are in consistent with literature; moreover, the optimum operating parameters were further enhanced to achieve superior performance. Integrated methodology maximized tool life to the moderate speed of 40m.min-1, feed rate of 358 mm.min-1 and depth of cut of 0.8mm. It is generally concluded that the cutting performance has poor relation with alloy properties compared to the operating conditions.

The paper deals with examination of dynamics of linear hydraulic cylinder with mass load. The hydraulic cylinder is placed in vertical position. There is experimentally simulated a system state. In this case a higher piston velocity is achieved due to the mass load compared to the piston velocity that corresponds to a supplied flow. A piston oscillation of the hydraulic cylinder is caused by rapid stop of movement in a desired position. There are experimentally evaluated eigenfrequencies of the linear hydraulic cylinder depending on the piston position and the mass load. Mineral oil was used as the working liquid. Time dependencies of pressures are measured on sides of the piston and the piston rod. Furthermore there are measured time dependencies of the piston position and the oil temperature. A mathematical model is created for this hydraulic system. This model is realized by Matlab SimHydraulics software. There are simulated time dependencies of the piston position and the pressure on the side of the piston rod. The mathematically simulated time dependencies of the pressure and the piston position are compared with the experiment.

This paper presents a kinematic and dynamic analysis and distribution of the stress in items of a planar mechanism by means of the MSC ADAMS software. Graphic dependence of kinematic and dynamic magnitudes of some points is given in dependence on the angle of rotation of the driving item and in dependence on the time. Distribution of the stress in the items presented is in [Pa]. In relation to the kinematic and dynamic analysis and subsequent simulation [1-3] of the planar as well as spatial mechanisms, it is great solution to use MSC Adams software program. The considerable advantage of this mentioned program is based on its simplicity from the aspect of modelling and moreover, it is important to point out that utilisation of the mentioned program leads to results which are precise and accurate in the case of the numerical solution of the equations in the whole magnitude referring to motion of mechanism while the given results are obtained in the graphic form.

Manufacture of new parts of machineries, devices, etc., especially in engineering and metallurgy requires machining of the feedstock in a mechanical way. During machining occurs immediate contact between the tested specimen and the tool and in their mutual relative movement of friction and wear. One of the possible variants how to eliminate this fact is the application of process fluids during machining.
Currently, we are trying to simulate long-term testing by laboratory testing called tribology. The experiment presents friction between two materials that are under real sliding contact. This article examines the tribological characteristics between two materials (tool - ball and workpiece material - disc). The paper contains findings when examining process fluids by tribological test Ball - on - disc, this test is currently used in practice, very widespread, this test can imitate various operations of cutting machining. This paper deals with the evaluation of tribological properties (the coefficient of friction, wear of disc and wear of ball) between the ball from ceramic material Si3N4 and the test material (stainless steel X5CrNi18-10, EN 10088-3 and steel commonly used in engineering 16MnCr5, EN 10084-94) by using two kinds of process fluids.

Method of cold-box-amine is widespread and frequently used technology for the production of cores. [1] Characteristic defect castings of ferrous alloys, which often accompanies the use of amine - Cold box cores are veining . Survey , it was found that 77 % of those surveyed foundries have problems with veining, 71 % foundries solves this problem ( or try to tackle ) anti veining ingredients in nuclear and molding compounds , but only 29 % considered their " antiveining " method for successful and favourable. [2] Article discusses the possibilities of elimination veining. Ingredients called additives lower the temperature at which the SiO2 begin to soften and form a melt at the surface of the grains, reduce the reactivity and increase the temperature of transition to a tridimit and cristobalit. These passages encourage increased tensions subsurface sand and reduce stress for the formation of veining on the surface of the core or mold. Experiments were performed to assess the impact of silica sands and the impact of additives on the quality of the casting surface.

Gases evolving from moulds, cores, coatings deposited on sand and metal moulds constitute one of the basic reasons of several casting surface defects: blow-holes, pinholes, pitted skin, etc. In research performed up to now the moulding sands gas evolution is determined in two ways: normalised, in which the gas amount emitted from the sample placed in a heated flask is determined or in the other way, in which the gas amount emitted from the core - covered with liquid metal - is determined. In these both methods the result constitutes the total amount of gases emitted from 1g of a moulding sand and the emission procedure as a time function. The new method of investigating the kinetics of gases evolution from moulding sands (and coatings), applied for making moulds, is presented in this paper. The kinetics is tested not only as the heating time function but also as the temperature function. The method was developed in the Department of Mould Technology of the Faculty of Foundry Engineering, AGH. Amounts of gases emitted from the moulding sand at the given temperature in the time unit are obtained in investigations. The results of testing the group of moulding sands (furan, alkide, moulding sands with water glass) and the group of protective coatings applied for sand and metal moulds, are presented in this paper.

The aim of this study was to find possibilities of using the Fourier transform in the analysis of vibration load tests of heterogeneous mechanical systems, especially those of a biological nature. The study applied the idea that the dispersion of a stationary stochastic signal depends on its power spectral density. We have verified that a sophisticated reduction in the spectral power of the ergodic signal may be used to filter it effectively. The proposed procedure is suitable for the detection and separation of harmonic artefacts. We have created an algorithm in the MATLAB environment and tested its functionality when analysing the vibration transfer within the human axial system.

The article deals with the effect of variaton of the technological parameters on the change mechanical properties and density of the AlSi7Mg0.3 alloy using squeeze casting technology. The AlSi7Mg0.3 alloy has been chosen because the acting pressure has the most significant impact on Al-Si alloys. For the make a samples was used a direct squeeze casting technology. Differently casting temperatures and mold temperatures at the acting pressure of 30 MPa were varied for individual samples. From the mechanical properties was specifically evaluated tensile strength and elongation.

Current contribution contains of results of experimental measurements performed within the determination of initial raw feedstock materials moisture content and its influence on final properties of subsequently produced briquettes. A birch wood chips samples with five different moisture contents, specifically 5.0%, 7.6%, 16.7%, 19.0% and 27.7%, were used for experimental investigations. Investigated briquette samples were produced by hydraulic high-pressure briquetting press Briklis, type BrikStar 30-12 with cylindrical pressing chamber of 50 mm. All investigated briquette samples were produced under the same conditions with constant adjustment of all parameters of used briquetting press. A basic physical-mechanical properties of investigated briquette samples were used as a criteria of investigations evaluation. All measured values were subjected to the statistical analysis. Final evaluation of measured values indicated that best results were achieved by briquette samples produced from feedstock material with moisture content equal to 7.6%. Evaluation of current investigation also proved that if moisture content was higher or lower, the quality of produced briquette samples decreased.

The article presents the microstructure and mechanical properties of two types of aluminium alloys AlSi10 and AlSi5Mg. The structure and mechanical properties as a tensile test of two alloys AlSi10 and AlSi5Mg were studied and compared. Gravity casting is very good process for making complex mechanical parts of low density metals like aluminium alloys. Therefore our samples are prepared by gravity casting technology. Light metals have come to the forefront in the automotive industry and improved fuel economy. Therefore, we compared the AlSi5Mg alloy with a commonly used alloy AlSi10. This type of alloy AlSi5Mg has excellent casting and technological properties (good machinability and corrosion resistance). We are engaged with the issue of the production of castings for the automotive industry, at our department the Department of Engineering Technology-Technical University of Liberec, many years. Currently, we are focusing on aluminium alloys, their metallurgy and crystallization conditions with minimal internal defects.

Grain refinement in commercial aluminium alloys can be achieved by addition of AlTi5B1 master alloy, containing α aluminium matrix, TiB2 and Al3Ti particles. These particles act as nucleation points for α Al matrix, resulting in a uniform fine, equiaxed as cast microstructure. Current grain-refinement practice involves the addition of master alloy (e.g. Al-Ti-B, Al-Ti-C) before casting introducing inoculants particles to the melt. The final size SDAS in aluminium cast alloys depends on the kinetics of both nucleation and growth of solid in the liquid. As per the classical nucleation theory, the critical activation energy (ΔG*) to form stable nucleus and the critical radius (rkr.) for the nucleus to grow into a crystal with long order atomic arrangement are inversely proportional to the undercooling. In practical instances, nucleation does not occur heterogeneously on solid substrates such as mould walls. Several works, mainly regarding primary foundry alloys, have been carried out on grain refinement revealing how the TiB2 particles present in AlTi5B1 master alloy provide a germ for heterogeneous nucleation; however, these particles become efficient grain refiners only with excess Ti content. This condition can not only increase the nucleating potency of TiB2 particles, but also reduce the grain growth of primary α - Al crystals during solidification. At atomic scale the nucleating potency of TiB2 is dictated by the mismatch between the lattice of this particle and the nucleating phase. The performance of AlTi5B1, well established to be the best grain refiner for cast aluminium alloys as AlSi7Mg0.3 and AlSi12Cu2. Producer of the master alloys as AlTi5B1 guarantee the chemical composition but not size of particles that are very important for solidification process. This review focuses on the quality of five AlTi5B1 master alloys.

The aim of this paper is the comparison of selected rheological properties of polymeric composites with glass fibers materials before and after exposure in UV box. Rate and depth of degradation induced by the environment were evaluated by Frequency Sweep Test, which monitors changes in viscoelastic properties of polymers with respect to their molecular structure and their behavior in thermoplastic processes. Degradation process resulted in changes of complex dynamic viscosity, storage and loss modulus, changes in molecular weight and its distribution. UV radiation is intense degradation factors affecting the change in the structure and properties of polymers - the polymer matrix gradually degrades by UV radiation, the viscosity of the composites decreases, the COP is moved to lower angular frequencies with increasing molar mass.

Spin coating is basic method for preparation of thin polymer resist layer (polycarbonate) or colloidal solution (grapheme oxide in alcohol). This method main benefits are speed of preparation and the possibility of tuning final coating of silicon sample by variations of parameters such as the speed of rotation, time and the amount of the solution. To find out the exact graphene oxide layer spin coating process a planned experiment was designed. The greatest coverage of the silicon sample grapheme was obtained by studying the data obtained from electron microscopy (SEM) and light microscopy (LM) of the spin coating input conditions

In the last decades, advanced brake technology in the port sector follows the global productivity developments of the international maritime trade. Container vessels are getting bigger and bigger and the ship to shore cranes is getting consistently higher. But service, emergency or storm brakes cannot be getting bigger and bigger to meet these increasing demands. Throughout history, innovations and advancements in technology have made industry better through automation and increased efficiency. No matter how advanced industry becomes, the need for emergency duty stopping brakes will not go out of style because there are always circumstances that require mechanical brakes to do the job. Brakes will invariably insure against those rare, yet potentially catastrophic events that even modern technology cannot defend against.

Passing of vehicles along curved track is a serious technical problem, which needs special attention. It is especially actual in the environment of urban lines, where it is necessary to pass a track of small radius. There is a significant strain of track as well as tram's bogies. It results in excessive wear in rail-wheel contact. Considerable is also the noise caused by operation on such track. Behavior of the vehicle when riding along track curve is influenced by the wheelset guidance design. If the wheelset guidance is able to set the wheelsets in track curve to a radial position, mitigation of the negative phenomenon can be expected. This paper deals with a design of a mechanism for setting wheelsets in a track curve to a radial position for tram cars. Dynamical analysis of a simplified tram car model was performed. Courses of monitored values of bogie with and without designed mechanism are compared.

The use of a new method of attaching fixed blades to a stator disc led to the need for evaluating the strength of a riveted joint. Conventional mechanical testing revealed large variations in the strength of this joint. After sectioning the joint, it was found that the shank did not fill completely the hole in the shroud of the disc. Further investigation involved numerical simulations using the DEFORM software, because securing additional samples for physical examination was complicated. The first simulation task focused on determining the tearing-out force, taking into account work hardening of the shank material due to plastic deformation. The second simulation task aimed to identify optimum initial dimensions of the shank. The goal was to ensure that the rotary upsetting process causes the shank to completely fill the hole in the shroud. As a result, the joint strength would be improved and, above all, the variation in strength eliminated.

On the base of a well-known method of machining with disk-shaped rotating tool the self-propelled tool was designed. The principle is based on braking the tool rotation during machining, until the moment of determined wear criterion on the tool flank. As with the growth of tool wear the force of cutting resistance increases, it is possible to use it for automatic tool swinging into a new position by which a new part of cutting edge comes into engagement. The paper describes the tool design, theoretical analysis of Rz after machining and actual experimental machining results.

Grinding is an overly used finishing technology, which can obtain very accurate surface integrity. The desirable surface quality after grinding is one of the most relevant parameters. In production, surface preparation such as chromium plating, nickel plating, etc. are more prevalent. These platings are used as protection against corrosion, erosion, abrasion and as a material for the renovation of worn parts. This paper discusses the change of nickel coating machines, which has an influence on surface integrity and microstructure after grinding. The team has built a completely unique and new technical solution for the covered equipment which had never been built in the past. The input parameters were selected based on past experience in the company, related to the area covered in this paper.