Fulltext search in archive

The effects of strengthening phase in particulate ceramic composites on their properties were studied in presented paper. The experimental materials were a monolithic Si3N4 and particulate ceramic composites consisting of Si3N4 matrix with different additions of the SiC strengthening phase (10 and 20 vol.%). The microstructure, density, hardness and fracture toughness of Si3N4 + SiC ceramic composite materials were compared with monolithic Si3N4 based ceramic material. The addition of SiC particles into the Si3N4 based matrix does not positively influence the phase transformation from ?-Si3N4 to ?-Si3N4 in Si3N4 + SiC ceramic composite materials, but it affects the growth of prismatic ?-Si3N4 grains and contributes to the creation of fine-grained microstructure. The increase of SiC strengthening phase portion slightly increases relative density of Si3N4 + SiC ceramic composite materials. The hardness of ceramic materials increased from 14.48 GPa at monolithic Si3N4 ceramics to 16.99 GPa at ceramic composite with 20 vol.% SiC. The highest fracture toughness value of 8.30 MPa.m1/2 was achieved for monolithic Si3N4 ceramics, the lowest value of 7.09 MPa.m1/2 was achieved for ceramic composite with 20 vol.% SiC.

In this paper, the possibilities of selective laser melting (SLM), one of metal additive manufacturing technologies, in the preparation of trabecular structures are discussed. Despite great advantages in geometrical freedom, there are specific process-inherent aspects that must be considered before the production of such structures. To verify SLM capabilities, we tested different orientations (horizontal and vertical) and thicknesses (0.2-4.0 mm) of single struts. Significant irregularities in strut thickness and deviations from the designed cross-sectional area were observed. Horizontal struts showed greater geometrical deviations. Based on our observations, a trabecular structure was prepared with all struts inclined 45° from the building platform. Due to the 72% porosity, mechanical properties approached those of the bone, which is beneficial for the application of such structure in orthopaedics for bone tissue substitution.

This thesis deals with deformations originating from heat treatment of the bearing metals. This is about the comparison of the heat treatment by rotating method in which the parts are feeded individ-ually into the rotating device and heat treated on hardening equipment in continuous way with high capacitive power. After the heat treatment it follows the operations of the grinding of the faces and diameters of the bearing rings. After the hardening we take into account two parameters, which may be mostly affected by hardening process namely: flatness of the faces ( cradle) and outer diameter ovality. Each of such deviations has got adverse influence during the grinding, therefore the hardening tech-nology is in most cases focused on elimination of this problem. The results of the heat treatment with higher deformations were confronted with values achieved by simulation software SYSWELD used for heat-metalurgical analysis.

Magnesium materials are interesting for application in medicine as biodegradable implants. There is an ef-fort to improve mechanical and corrosion properties for this application. Powder metallurgy seems to be a progressive method suitable for improving those demanded properties. Therefore, this paper deals with the preparation of pure Mg by extrusion of milled powder. The milling process should lead to better homogenei-ty of microstructure and the disturbing of the oxide layer on the powder particles. Also, the input deformation energy in the milled powder should affect the deformation and recrystallization process during extrusion. In this paper, the influence of extrusion temperature on microstructure, mechanical, and corrosion properties is evaluated. Higher extrusion temperature leads to the larger deformed grains in the extrusion direction and higher tensile strengths. On the other hand, the plasticity and compressive yield strengths are reduced with higher extrusion temperatures. Corrosion properties are negatively affected by the iron inclusions incorpo-rated in the structure during milling. Otherwise, corrosion resistance decrease with increasing extrusion tem-perature due to the grain size.

This document presents the characterization of the dynamic mechanical properties of a racecar's frame. First, it introduces the applicability of modal analysis, then the modal analysis of a lightweight vehicle chassis will be detailed, which is the focal point of this paper. This analysis was performed to determine some of the modal parameters, in order to reduce the noise of the vehicle, the probability of a component failure and to improve the comfort. The simulation part of the applied analysis was based on dynamic FEM (Finite Element Method). The measurement part of it was based on measuring the FRFs (Frequency Response Functions), with the help of accelerometers fixed at the nodes of the frame. The excitation signals were provided by a shaker connected to the chassis. In order to provide good quality results, the processing and evaluation of the simulated and measured data has to be done properly, which is discussed in detail. However, one dominant factor of a modal analysis is to find the optimal measurement setup. For this reason, the details of the measurement setup will be included. Hence one of the goals was to improve the coherence curves of the FRFs. Thanks to the presented techniques, the coherence curves managed to be improved and the results of the simulation and the measurement were found to be in good agreement.

The aim of the article is to compare the experimental investigation of deflection of the sandwich composite beam with theoretical models. The experimental test specimens were composed of three layers. Skins were made using epoxy-resin-impregnated glass laminates with plain weave. The light weight foam Divinycell H100 was used as sandwich core. The three-point bending test was carried out. Fibre-optic strain gauges, SOFO SMARTape Compact deformation sensors, were used for determining the deflection of the sandwich composite structure. Experimentally obtained data were used for comparison with theoretical models – sandwich theory with the transverse shear, sandwich theory without the transverse shear, laminate theory with the transverse shear and laminate theory without the transverse shear.

This paper deals with the experimental testing of the basic crash element, which is made of PA6 with short carbon fiber reinforcement by additive technology. Additive technologies allow the production of very complex, thin-walled and hollow shapes, which can be used to tune the desired characteristics of the deformation member. The variable size of the deceleration, the length of the deformed portion and the total amount of energy absorbed can be controlled by suitable geometry. The initial impact peaks can be reduced by gradually changing the geometry. Experimental testing of basic crash elements was performed on several specimens and average values are used here. Primarily the maximal and average deceleration and total energy absorbed are monitored. Obtained data will be used for validation of material properties in Crash-Pam software. Using a validated material model, larg-er and more complex deformation members will be proposed, eg for the racing car Formula SAE.

The paper describes the possibility to streamline the process of modal parameters estimation performed on the washing machine heater. As the shape of the mentioned part does not allow to capture its response to excitation using conventional gages of acceleration, Polytec PDV-100 vibrometer based on laser Doppler vibrometry method was used. Such a non-contact device captures the response in a form of velocity only at one point in one direction. For that reason, the process of modal parameters estimation can be relatively timeconsuming, especially in case if the vibration of the analyzed structure occurs in more than one direc-tion. The authors speed up the process of response capturing using full-field high-speed digital image corre-lation system Q-450 Dantec Dynamics allowing investigation of the displacements in three mutually perpen-dicular directions. Its adaption for experimental modal analysis was ensured by developing an additional software called DICMAN 3D. As the output from the stereo camera system is in a form of 3D displacements in time, DICMAN 3D allows evaluating a single or multi-reference measurement using several algorithms. As the operational temperatures of the heater change due to the chosen wash cycle, the authors used numeri-cal modeling to analyze the influence of the temperature on the heater natural frequencies shift.

A huge amount of waste comes into being from tyres which cannot already be used for their purpose. There are many ways how to utilize this waste but material recyclation is a priority. Waste tyre rubbers can be processed into a form of granulate which can be used into polymeric composite materials. This research deals with possibili-ties of tyre waste composite material utilization in areas distinguished for wear. The aim of the research was an assessment of a usage possibility of rubber powder (RP) coming into being from tyre recyclation process as a filler into a thermosetting matrix from firm Havel Composite applied into composite boards made by a vacuum infu-sion. The research focused on an evaluation of wear by friction against loosely fixed abrasive particles according to GOST 23.208-79, hardness and interaction of the matrix and the reinforcement by means of SEM analysis of the polymeric composite materials reinforced with waste microparticles arisen from tyre recyclation process. Research results proved a positive influence of the filler on the improvement of the wear resistance depending on the size of active rubber powder.

In this work the influence of cyclic thermal tistory on the microstructure and mechanical properties of AlSi8Cu2Fe alloy was studied. The commercial aluminum alloy was subjected to a special heat treatment dur-ing which the alloy repeatedly changed from a liquid to a semi-solid state. During this process, samples were taken, and the castings were subjected to another study. Gradual changes in the microstructure, chemical com-position of the alloy, hardness and mechanical properties under pressure at normal temperatures have been documented. With the increasing number of cycles, the content of alloying elements, especially magnesium, decreased significantly, the proportion of casting defects increased, especially hydrogen bubbles, microshrinkage and oxide inclusions in the alloy. These changes also led to a decrease in the mechanical properties of the alloy. A series of samples without cyclic heat loading was also prepared for comparison.

Ti-6Al-4V alloy is the most commercially used material for the production of orthopedic implants. However, despite its excellent properties, it is not an ideal material for use in medicine in terms of vanadium toxicity and relatively high modulus of elasticity. Titanium β-alloys could be a suitable replacement in future years for Ti-6Al-4V alloy, as they have a lower modulus of elasticity and contain non-toxic elements. Some of the alloying elements may even increase the biocompatibility of the alloy. In addition, a progressive 3D printing method would allow custom-made implants with the required properties to be printed. The aim of this work was to characterize the β alloy Ti-30Nb by Selective Laser Melting (SLM) method and to determine its mechanical properties. In addition, heat treatment was applied in order to homogenize the structure. Ti-30Nb alloy was compared in as-built state and in annealed state.

The article deals with analytical and experimental solution of vertical oscillations of a mechanical system of bound bodies. The content of the article is to perform an analytical solution of the vertical oscillation of a system of bodies using the computer program MathWorks Matlab and MS Excel. Furthermore, an experimental investigation on a laboratory model of a mechanical system of the same parameters was proved. The aim of the work was to compare the analytical solution with the experimental method and to check the accuracy and applicability of analytical methods for the solved mechanical system.

Dynamic analysis of crank mechanism is realised by relaxation method, where a connecting rod is modelled with three manners. In the first case the connecting rod is modelled as a rigid body, in the second case this one is modelled with two mass points and in the third case the connecting rod is modelled with three mass points. Results of all manners of modelling are compared and evaluated.

Experience with the use of NC machine tools shows that cutting conditions cannot be optimized without a more detailed knowledge of the machining process. The essence of the adaptive machining system lies in the response to he machining conditions (change in allowance, cutting width, material hardness). In doing so, it allowance a constant selected parameter, e. g. cutting force.

Zinc-based materials are considered as promising materials for an application like biodegradable medical devices (bone fixations, stents). Such materials have to be characterized by an excellent combination of me-chanical, corrosion and biological properties. Presented paper is focused on the characterization of micro-structure and closely related mechanical properties for 3 zinc materials, namely pure Zn, Zn-0.8Mg and Zn-0.8Mg-0.2Sr. Studied alloys were prepared by gravity casting, homogenization treatment at 350 °C and extru-sion at 200 °C and extrusion ratio 11. Alloying by Mg caused the refinement of microstructure, formation of Mg2Zn11 phase and related improvement of mechanical properties like TYS and UTS for an extruded alloy. An additional encore of Sr causes a systematical improvement of TYS and UTS values, although the elonga-tion vas slightly decreased due to the presence of brittle SrZn13 phase.

The properties of bonded magnetic materials (RE-M-B /polymer magnetic composites) depend not only on the magnetic properties of powder, but also on the parameters of the consolidation process and the type of binder. Increasing the binder content in RE-M-B /polymer composites could be very beneficial from the cor-rosion resistance point of view, which, unfortunately, is not conducive to the magnetic properties improve-ment. Therefore, a compromise between both trends is necessary to obtain a material with adequate corro-sion resistance with an acceptable decrease in magnetic properties. In the paper the results of research un-der Nd12Fe77Co5B / biotolerant-polymer composites with different binder content have been presented. The research has been carried out on Nd12Fe77Co5B / biotolerant-polymer composites with 20 and 10 wt. % of binder. Due to the possibility of using the magnetic material in restorative medicine, as a binder the bio-tolerable polymeric material has been used (acrylate). All results has been compared to previously deter-mined measurements for composite with a binder content about 3 % wt.. It has been found that the content of 10 % wt. bio-tolerable polymeric material in the magnetic composite is the most favorable (optimal) - the binder material is evenly distributed throughout the composite volume.

This paper discusses the modeling and simulation results of a new multi-material for a cost-effective Selective Laser Sintering (SLS)-based 3D printer. As this technology utilizes several materials, the me-chanical property analysis of multi-materials is crucial for manufacturing an object with the desired physical characteristics. Firstly, the development of a database of the SLS 3D printing materials is ac-complished and based on the mechanical properties of materials, this optimization technique is proposed. Secondly, enhancement of physical property by stiffeners is considered and based on the stiffening tech-nology, and an alternative optimization method proposed. Finally, two different material minimization methods are discussed in this research. The first method is based on the embedded materials with desired mechanical properties for enhancing the mechanical properties of the printed objects, which are twice optimized by this method with increased material saving. The second method is designed to use stiffeners to improve the stiffness characteristics of the materials, and then, perform material optimization. This method is effective with more suitability to complex composite geometries. Thus, the methods help to reduce materials used as well as the production cost in 3D printing technology.

The paper presents the results of an experimental research and a numerical calculation of a multi-gap seal of a centrifugal pump. The experimental research allowed to obtain the characteristics? performance of the multi-gap seal at different operating modes, in dependence on the axial size of the chambers, pressure distributions? changes, and a leakage from the seal. Using finite volume methods, values of radial hydrostatic forces, pressure distribu-tions and leakage values were obtained. The results of the numerical calculation were compared with the results of the experiment, which showed that they matched.

The objective of this paper was to investigate and respond to the quality and strength of CMT welds that were sub-jected to degradation effects and subsequently to tensile testing. The tensile test was recorded using AE acoustic emission. The experiment focused on the quality of CMT welds (Cold Metal Transfer) and the resistance of these welds to corrosion degradation. Welds are generally exposed to environmental influences such as high stress, stress and degradation effects. The combined effect of these factors may in some cases result in the destruction of weld joints. For this reason, emphasis is placed on the quality of welds and their resistance to environmental influ-ences. For this measurement there were ten samples prepared, divided into two groups, each having five samples. One group was subjected to corrosion degradation, while the other one was at the same time subjected only to envi-ronmental influences. Subsequently, all samples were subjected to tensile testing. The course of this test was rec-orded using the AE acoustic emission, where the AE sensor was attached to each weldment to record dislocations during the tensile test. Named values were evaluated in the Dakel–Daeshow program.

Extrusion process parameters play key roles in aluminum profile extrusion processes. In this literature, by using Box-Behnken experimental design to arrange the simulations using the ALE software HypereXtrude, Response Surface Methodology (RSM) were applied to study the simulation results and discuss the effects of five process parameters, namely billet diameter, billet preheat temperature, die temperature, container temperature, and ram speed, on the outlet velocity distribution uniformity of the profile named an Upper beam on the Train. The interactions between the five parameters also were investigated. Additionally, a second order response surface model between the extrusion process parameters and the evaluation criterion of outlet velocity uniformity was established. An optimization of the process parameters with the purpose to find the most uniform outlet velocity distribution was carried out based on the response surface model. The results show that the three parameters, namely billet diameter, ram speed and die temperature, have significant impact on the outlet velocity uniformity. And there are obvious interactions between these three parameters. After the subsequent optimizations, a more uniform outlet velocity distribution was obtained, and the final acceptable profiles were produced.

This paper completes a design of power monitoring system of machine tool based on MSP430F149 microcontroller. This system is mainly divided into four modules: the electric energy information input and processing module, electric energy metering operation processing module, Single-Chip Microcomputer system internal data processing module, and PC memory module, respectively. The voltage transformer and current transformer collect voltage signal and current signal respectively, which were inputted deferentially to the ATT7022A voltage channel and current channel, to achieve electric energy information input and processing. The special measure chip ATT7022A measures the three-phase active power, reactive power, apparent power, active energy and reactive energy to meter and operate electric energy. MCU system processing module communicates with ATT7022A chip via the SPI bus interface by using the 16 bit MSP430F149 microcontroller. The establishment of database model and database table using the relatively practical method of entity-relationship achieves PC internal data memory module. In addition, the fabrication of PCB circuit board and software writing are also introduced in detail in this paper.

This paper was based on the cooperation the Department of Machining, Assembly and Engineering Metrology with company accredited by Czech Institute for Accreditation. It deals with issues of calibration 3D indicators. Generally, the calibration of non-specified working gauges integral part of every company, which uses such gauges. Checking/calibration of measuring instruments is important for ensuring the uniformity and accuracy of measurements to ensure continuity of measurement results. The paper deals with streamlining the process of calibration of indicators 3D design and practical verification of appropriate gauge for the calibration. The target of innovation is to eliminate the errors and shortcomings of the current solutions. In the conclusion are the results of calibration by help current and new solution checking device and their comparison.

To design an optimal support of a large shade sail it is necessary to determine forces in wire ropes that support the sail. Relations between a sail loading and ropes reaction forces, rope diameters and sail stresses were investigated. To simulate the sail behavior and set up these relations, numerical (FEM) models were created and analyzed. Most of the results show nonlinear relations between above mentioned parameters and they depend on the sail geometry, applied loads and the rope diameter. It means that for every specific geometry and loading of particular sail an optimal rope diameter and support should be designed. The nonlinear numerical analysis is very suitable tool for this purpose and thus specialized systems based on the Finite Element Method (FEM) should be used to simulate and analyze such problems.

The article deals with the calculation of stiffness of a secondary suspension spring built in a bogie of a rail vehicle with a tilting car body. The vertical stiffness of the springs was calculated using the ANSYS program. The results were compared with calculated values afterwards. The lateral stiffness was evaluated in a similar manner. Analytical method by Gross, Wahl, Budrick, Timoshenko and Ponomarev was used for comparison with numerical values. The ANSYS simulation was performed for calculating the vertical stiffness of the triple springs. The most suitable analytical method is a method by Timoshenko and Ponomarev, where the percentage difference was the smallest. The obtained data will be used as an input for the design of coil springs which will be implemented in a model of a vehicle with a tilting car body, for which the comfort values during transition in curve will eventually be determined.

Sandwich composites are well known for many years and its place among the construction materials have they deserved mainly due to very good mechanical properties related to their weight. These materials have been a subject for many researches, but very few of them were focused on the behavior of curved constructions in bend with respect to their specific shape (curvature). With increasing number of new materials and resulting possible material combinations, it is necessary to characterize performance of new prepared structures and also evaluate the effect of a shape on the behavior of sandwich constructions with regard to their material composition. Presented paper deals with an investigation of flat and curved beams of sandwich structures, which correspond by their material composition to those, used in transport industry. Specifically, the influence of curvature size on a change of bending properties of structures with specific material composition compared to flat constructions is evaluated. This influence is also investigated in terms of specimen clamping and type of bending test. Obtained results showed that properties of sandwich structures are dependent not only on size of curvature, bud also on core thickness. Moreover, these results can help designers, constructers or technologists with design, dimensioning or production of these materials for specific applications.

Drill bits used for machining of composite materials can have different geometries and it is difficult to choose suitable geometry for a specific type of composite. Unsuitable geometry of a drill bit leads to bad surface quality. The objective of this paper is to find the most suitable drill bit geometry for machining of the thermoplastic composite C/PPS in terms of surface quality and magnitude of thrust force under different cutting conditions. Three drill bits were chosen for experimental investigation. A significant influence of the point angle was identified. A gradually decreased point angle together with an increased rake angle of the cutting edge lead to better surface quality. In addition, investigation of the influence of cutting conditions on surface quality and cutting forces was performed. A considerable influence of feed was observed in comparison to cutting velocity. Information included in this paper can help to design more suitable technology for drilling of thermoplastic composites.

At design of cutting tools the positioning of cutting edges and geometry of cutting inserts are becoming increasingly diversified with the development of cutting procedures. As a result, the generated tool marks on cut surfaces also can take many forms. Roughness values in face milling can change both in planes parallel with the feed direction and in planes at angle to it, therefore it is particularly important to be able to plan the roughness characteristics of surfaces. A new method is introduced in the paper for planning the roughness characteristics of cut surfaces that can be used to determine theoretical values of roughness characteristics of surfaces generated by tools having defined edge geometry. It is based on CAD modelling of the theoretical cut surface; practically any complex tool geometry can be modelled and 3D roughness parameters determined. In application of rotating tools a variety of tool designs and setting accuracy were taken into consideration during the determination of theoretical values for the simultaneous cutting of more than one edge. An example is shown for two different insert geometries.

Parametric modelling based on mathematical relationships allows creation of different variants of proposed solutions in real time. In particular, parametric modelling enables rapid design of 3D virtual models intended for further analysis and simulations. This paper presents an approach to design of a six strand wire rope model in a CAD environment. The presented model is characterized by double helical winding wires. Wires axes curves are mathematically expressed in the form of parametric equations. The parametric equations used in model generation are presented and the whole methodology of rope model creation in CATIA V5 software is briefly described.

The article deals with non-destructive measurement of the effective throat thickness of fillet weld with deep penetration in T-joint. Ultrasonic Phased Array technology is used to indirectly measurement of effective weld throat thickness. Phased Array ultrasonic systems utilise multi-element probes, which are individually excited under computer control. By exciting each element in a controlled manner, a focused beam of ultrasound can be generated. Software enables the beam to be steered. Two and three dimensional views can be generated showing the sizes and locations of any flaws detected. The results of Phased Array ultrasonic measurements are compared with the real results obtained from the real macrostructural analysis. The methodology is appropriate for verifying compliance with the design weld throat thickness in the production of steel structures.

The present paper deals with the metrology, especially with the legal metrology that is responsible for assuring the uniformity and correctness of measurements. In addition to the definition and explanation of the basic terms and principles applied in the metrology, the paper presents especially the results of the scientific and research work in the cross-disciplinary fields of the legal metrology in Slovakia, namely in design and realization of a new measuring system for the verification of the radar level gauges.