Fulltext search in archive

Dynamic characteristics of a machine-tool-workpiece system are not constant during machining, but they can be changed by a variable spindle position, a rising tool wear or a gradual change of a workpiece geometry. This paper deals with an influence of spindle unit extrusion on stability of a machining process. Two milling cutters with different rigidity, flexible and stiff, were used for experimental machining at three axis milling machines. Clamped milling cutters were extracted systematically and a frequency response function was measured simultaneously. Reached data (natural frequency and dynamic compliance) were used for finding a correlation between dynamic parameters and extrusion of the spindle. Critical extrusion of the spindle unit was predicted by an experimental measurement and an axial depth of cut thresholds was established for the stable machining.

The aim of this paper is to describe anodizing technology for deposition of Al2O3 coatings on Al substrates. Various methods of layer deposition were used for the experiments. Deposition was carried out in acidic environments, using sulphuric acid (H2SO4) and chromic acid (H2CrO4). Several samples were heat treated (annealed). Chemical composition of the substrate and the coating was tested by GDOS method using SA2000 and GDS 500A devices. Surface morphology and structure were evaluated by SEM, using VEGA5135 electron microscope. Selected mechanical properties as thickness, microhardness and adhesion were also determined.

An efficient polishing process has been carried out at the polishing speed about 200 mm/s in vacuum with temperature of 850˚C. With the polishing time reaches 120min, the surface roughness of polished could get to Ra0.016 compared to original Ra9.67. Mass loss rate per hour was used to quantify the polishing efficiency. Increasing the polishing pressure could get high mass loss rate, which could be used in the rough machining process. In fine machining process, the polishing pressure should be lower and the high polishing speed should be remained. The 3D morphology from atomic force microscope(AFM) shows there are some summits about 30-40nm in height, and the summits take into the shape of directional narrow cone.

Aluminum specimens for pilot resistance testing at higher temperature and mechanical loading were prepared by means of powder metallurgy. The aluminum powders with nanooxide surface layers were prepared. The tests were performed at 300°C and applied stress of 100, 125, 150, 175 MPa and at temperatures 350°C and 400°C and stress of 100 MPa. Aluminum specimens tested at 300°C and stresses of 100 and 125 MPa were characterized by very high resistance. Similar resistance was exhibited by specimens tested at 350°C and 100 MPa. The rupture of specimens tested at 350°C at 150 and 175 MPa was initiated mainly from surface defects. By aluminum tests at temperatures below 400°C, compact oxide layer was not disturbed. Oxide layer fragmentation at 400°C resulted in lower resistance of aluminum specimens. The resistance increase was accompanied by higher portion of ductile fracture with dimpled morphology. Large angle grains size was not changed. Higher temperatures and stresses cause dislocation netting on grain boundaries and initiate subgrains formation.

There are many situations when you need information about the internal structure of the materials. Computed Tomography (CT) is a non-destructive method of evaluating the internal structure, which was originally used for medical examination of the human body. Today it is already used in many different fields, where the aim is the examination of the internal structure of the material. Geopolymer is a term for all inorganic polymeric materials which are prepared from alumino-silicate materials by geopolymerization in alkaline environment at normal temperature and pressure. Computed tomography (CT) is an advanced method that allows the study of the structure based geopolymer composites with short fibers or nanoparticulate reinforcement.

Cutter vibration characteristics of five-axis milling machine in high-speed milling process were studied. Finite Element Modal Analysis for high-speed cutters with different parameters is conducted using finite element software.The impact of tooth number, extended length, diameter and material of milling cutter on the mode shapes and natural frequencies of milling cutter is researched in detail. Harmonic response curves of High-speed cutter under different frequency are calculated. Based on the response curve, the resonance frequency range of high-speed cutter is obtained in order to achieve high-precision milling and longer life of the tool. Analysis shows that: mode shapes of milling cutter are divided into strong vibration mode shapes and weak vibration mode shapes and its natural frequency become smaller with the increase of the cutter teeth number. Natural frequency of milling cutter decreases with the increase of extended length of milling cutter. The number of strong vibration mode is smaller with the increase of milling cutter diameter so that the milling cutter with large diameter can play a role of anti-vibration. Natural frequency of the high-speed steel cutter is lower than that of the diamond and carbide cutter. This research provides theoretical basis for the design of high speed milling cutter and reducing milling chatter.

The application of Al-Si alloy castings has gradually increased in many mechanical components in the last years, especially for cars and rail vehicles, thanks to the great potential of these materials as replacements for ferrous alloys. Controlling the microstructure of secondary aluminium cast alloy (Al-scrap and workable Al-garbage) is very important, because these alloy containing more of additions elements, that forming various intermetallic phases in the structure. The mechanical properties are strongly depending on the morphologies, type and distribution of the structural parameters. Microstructure control was realized with combination of different analytical techniques (light microscopy, scanning electron microscopy (SEM) upon deep etching and energy dispersive X-ray analysis - EDX).

The requirements for reducing the weight and increasing the strength and carrying capacity of the plane and space structures are constantly growing. The one of the way how to meet demands is to use the layered shell composite structures. They could be applied not only in mechanical engineering (containers, pressure vessels, etc.) but also in the civil engineering (cooling towers, roofs, etc.). The article deals with computation procedure of shell and plates using meshless methods. A mesh-free local Petrov-Galerkin (MLPG) method is applied to solve laminate plate problems described by the Reissner-Mindlin theory. Two projection methods are developed to generate the shell surface using the Lagrangian mesh-free interpolations. The bending moment and the shear force expressions are obtained by integration through the laminated plate for the considered constitutive equations in each lamina. The Reissner-Mindlin theory reduces the original three-dimensional (3-D) thick plate problem to a two-dimensional (2-D) problem. Results of transient dynamic loads in the composite plates using MLPG solution are presented here.

Presented work focuses on the influence of Mn and Fe in different ratios on the structural characteristics of AlSi6Cu4 alloys and identification of present intermetallic phases by means of EDX analysis in addition to the light microscopy. The intermetallic phases whatever of type never contribute to strain transfer in matrix and in this view are harmful in the structure. From an economic perspective it is desirable to use cheaper secondary alloys, but to guarantee the required strength properties of the material used for castings, it is needed to control the morphology of intermetalic phases. From the professional literature and practice, relationship between the content of iron and manganese (Mn/Fe≥ 0.7) is well known to guarantee the exclusion of intermetallic Fe in the form/shape of a "Chinese script characters" and not dangerous spindles (needles). It was discovered that this ratio affects the presence of Mn/Fe also in the intermetallic phases. With increasing Sr content in the experiments conducted, the percentage of Mn/Fe ratio in intermetallic phase in form of "Chinese script characters" reduces. It was found that under certain circumstances, also the ratio Mn/Fe = 0.7 does not guarantee the presence of intermetallic Fe phases only in the form of "Chinese script characters" in areas of highest stress of castings, i.e. on the castings of cylinder heads in the area of combustion chambers.

The work deals with non-destructive ultrasonic testing of butt and circumferential fillet welds in the repairing of gas pipelines. The new ultrasonic technique Phased Array was used for testing. The article compared the results of Phased Array ultrasonic inspection to X-ray inspection. Experimental samples were taken from real gas pipelines' repairs. It is a circumferential butt joint connecting 2 gas pipelines and 2 other types of circumferential fillet welds occurring during repairs of gas pipelines with pressure steel and steel patch. Experimental testing was conducted on ultrasonic flaw detector OmniScan MX2 by Olympus. Indications of defects in the weld joints obtained by ultrasonic testing are corresponding with the experimental results of X-ray inspection. Experimental results provided information for proposal of manufacture of artificial defects in these samples.

The article focuses on the issue of 3D measuring surface parameters using optical measuring devices, designing a statistical experiment and following evaluation. The development non-contact surface texture measurement methods lead to new possibilities for describing the surface of machine parts. But cannot be to rely only on the obtained the measured parameters values, and it is true that it is necessary to prepare the measurement. The processes of measurement enter many influences. Some of these effects can manage it, and then we call those factors. At the output of the receive process feedback. Method DOE (Design of Experiments) is used to locate a combination of factors that provide the most favorable response. The proposal described experiment compares and evaluates various surface roughness parameters of two different materials and machining technologies samples. Measurements were done by two operators, and each measurement was carried out three times. Measurement took place on a confocal laser microscope LEXT OLS 3000.

This paper deals with non destructive magnetic evaluation of ground surfaces of variable hardness based on Barkhausen noise (BN) technique. Except magnetic investigation, obtained BN signals are correlated with metallographic observation, microhardness readings as well as residual stress measurements. The results show that regime of heat treatment - annealing after hardening significantly affects the possible concept for monitoring surfaces after grinding. Conventionally heat treated surfaces of hardness 62 HRC indicate the typical surface thermal softening induced by grinding cycle whereas samples of lower hardness exhibit rehardening effect associated with the progressive decrease of Barkhausen noise responses along with the developed grinding wheel wear.

Material crystal compositions and their phase structures have become the necessary and important part of the materials research and advanced technology in recent decades. Each property and information about material phase structure is more or less immediate way depending on the structure and crystal composition. Prerequisite of any technological breakthroughs in this area is therefore detailed information on the structural parameters of materials.

The article describes the fundamental physical principles of the ultrasonic defectoscopy Phased Array, which provides new possibilities in the non-destructive testing (NDT) of materials, especially of welded joints. There is a report from the ultrasonic testing of welded joint with ultrasonic flaw detector OmniScan MX2 from the company Olympus NDT. The artificial defects were designed in software ESBeamTool 5 from the company Eclipse Scientific, which simulates the geometrical ultrasonic beams spread. Then, ultrasonic testing was performed at the same welded joint with artificially made defects. At the end, data from both ultrasonic testing were evaluated. The same procedure will be used for the design of ultrasonic inspection TOFD (Time of Flight Diffraction) and Phased Array at welded joints of gas pipelines.

The design of elliptic trajectories of kinematic mechanisms by classical method is a challenge. New method is proposed. Theoretical tests were conducted on a method. It can not be used for scaling and rotation. Some limitations are revealed as well. Geometric modeling showed the method can be applied to arbitrary curves. It should be noted that the theoretical and modeling researches of arbitary curves is not full. Simple robot was designed for processing ellipses. The design of the stand was assembled from aluminum profiles, linear modules and fasteners RK Rose + Krieger. Experiments have shown a difference between the theoretical and actual trajectory less than 5%. The error of stationing was 8,5% before using of the direct analytical method.

Molds used for pressing refractory fireclay shapes are exposed to very strong abrasive wear, which is given by the combination of applied pressure of more than 60MPa and processed materials like alumina (Al2O3) and silica (SiO2). Typical lifespan of molds is in several thousand cycles, our aim was to improve the lifespan 10 fold at minimum. To increase the lifespan of the critical parts of the molds, it was decided to use HVOF coating technology based on WC. This article evaluates the quality of the coating on the pins for pressing tools based on the technology used for deposition. An analysis was made on two sets of HVOF coated pins from different suppliers marked as a sample "A and B". Pins were analysed on tactile CMM with scanning system and samples from these pins were analysed on a multisensor CMM.

The compaction of powder metals and alloys is very difficult field due to preserving of unique properties of initial materials. One of few possible method of succesful compaction is plasma sintering. To describe detailed structure os powder metallurgy materials, it is necesary to use advanced microscopy methods such as SEM and TEM. In this study, the structure of NiAl intermetallic compaoud is described. The material was at first produce by reactive sintering from pure elements. Subsequently, the NiAl porous master alloy was milled and compacted by spark plasma sintering (SPS) technique.The particle size of NiAl powder was compareable to the grain size of compact material, which exhibited low porosity. It was proven that the interconnection on NiAl particles is performed by thin layer of nanocrystalline oxides.

The paper deals with some problems of quantitative metallography which includes evaluation of microstructure by etalons, measurement of structural parameters by coherent test grids and automatical image analysis. Some advantages and disadvantages of these methods are shown in this contribution on the example of evaluation of microstructure of graphitic cast irons. The automatical image analysis enables to eliminate some disadvantages of evaluation of microstructure by etalons and by coherent test grids but it has also some negatives.

The paper deals with the practical use of matrix model of sustainable development, the MSD (Matrix of Sustainable Development) in Industrial Management and an introduction to possible problems in implementation. The method is based on expert evaluation, the output of the relational matrix are values of importance, resp. the overview of the priorities of the problem, i.e. the individual social requirements and the factors of quality products. The implementation of the MSD model contributes to the holistic understanding of the product's life cycle. The results reveal the model on the one hand in it is the real importance, and, on the other hand, the possible shortcomings of some hitherto unknown factors. The benefit is also involved in research in the field of quality management and a focus on customer requirements.

This paper presents the theoretical and practical aspects of industrial robots transport systems problems focused on application possibilities connected with concrete type of robotic device. Introduction of the article presents today possibility of robot transport systems and collect information about basic technical parameters of transport systems, their design and construction. Main part describe industrial robot ABB IRB 140, collect information about technical parameters, its construction, axes, motions and applications used in industrial practice. Practical part of paper is focused on proposal of robot transport system design from manufacturing point of view.

Light reflection of materials depends on many factors, mainly on their colour and type, angle of light incidence and surface structure. This paper is focused on evaluation of the surface shape influence of expanded polyvinylchloride on light reflection. For this reason polyvinylchloride samples with different shapes, depths, widths and numbers of surface grooves were produced on CNC milling machine. The light reflection of the investigated material samples was experimentally measured by means of illuminance ratio. The samples were subsequently compared in terms of their ability to reflect light. A part of the work deals with mathematical simulation of the daylight factor for definite surface shapes. The simulations were performed using Wdls 4.1 software. It was found that the surface shape has an influence on the light reflection and on the illuminance in a given point too. The light reflection of the tested material is in general influenced by shape, depth, width and number of surface unevenesses.

The paper puts forward structure design and parameter analysis of the multi-angle and stepping transmission device, and this paper focuses on design and analysis of the multi-angle steering parts in the device. According to mathematical calculation and simulation analysis, the parts size of steering component is simulated and designed by the double cam-linkage mechanism. Though the design of these critical components of the steering device, the rods can be rotated in the specified angle (45° and 90°) by their relative motion without any external force, and the steering device is simulated by SolidWorks Motion. The results show that the multi-angle and stepping transmission device realizes the upset forging process requirements, improves the mechanization level of the sucker rod forging. The device will be used for the rod head machining operation in narrow space in automatic production line, and it also can be extended to other cylindrical rod's multi-angle and multi-position automatic machining operation.

Secondary and backscaterred electrons are the most common signals used for imaging in the scanning electron microscopy. Generally, SE are used to obtain topographical contrast while BSE show differences in chemical composition (so called Z-contrast).The aim of the present work is to show possibilities and techniques to obtain not-so-common information using BSE, as e.g. orientation contrast, residual stress, different allotropic modifications, etc.

Internal damping is able to monitor the microstructural changes in solid materials and these changes can be based onvarious mechanisms. In this investigation a same heat treatment was carried out on AZ31 and AZ91 magnesium alloys, aimed at detection of microstructure changes of material after homogenization annealing and also the process of precipitation was continuously analyzed by the internal damping measurement. Internal damping was measured as a function of temperature in AZ31 and AZ91 magnesium alloys by ultrasonic resonance spectroscopy. The internal damping spectrum was measured in the temperature range from 50 °C up-to 390 °C. Peaks of internal damping occurred in temperature range from 250 °C up-to 350 °C on AZ91 magnesium alloy. Also the mictrostructure analysis was carried out at the diferent stages of the internal damping measurement which showed creation of continuous precipitate in the maximum of the internal damping peak. The creation of the peak is caused by absorbation of energy by the process of continuous precipate nucleation and growth in the volume of material grains.

Metalworking fluid (MWF) aerosols are generated continuously during conventional machining operations and can have a number of adverse health effects. Exposure to the aerosols has often been reported to cause acute respiratory difficulties including asthma, hypersensitive pneumonitis and lung cancer. Aerosol measurement data was conducted to identify the major determinants that may affect exposure to aerosol fractions during turning of a cylindrical work piece on an uncovered conventional lathe. The aerosol mass concentration was investigated as function of spindle speed, fluid flow rate and sampling position. Synthetic fluid, mixed at 5% concentration with water, was applied via nozzle centred above the work piece at a distance of 70 mm. The aerosol mass concentration was determined gravimetrically and particle size analysis was performed by optical method. The results show that aerosol mass concentration increases with increasing the fluid flow rate and decreases by increasing the spindle speed. Moreover, the particle size analysis detected that a high quantity of particles smaller than 0.2 mm is generated at higher spindle speeds.

Nowadays is issue investigation the notch problems and their influence on component durability. For many manufactured components, we find various types of notches, such as grooves, step and holes. They have a tend to be the place where is concentrated stress, so called the macroscopic stress concentrator. In this area is higher risk of part destruction. Nowadays, there are hypotheses that are based on the assumption that the higher the roughness, the lower the durability. In many cases the designers prescribe unnecessarily high surface quality. It is necessary to maintain adequate quality of the surface, and also necessary that the component has attained a high durability. The paper deals with the influence of machining technology carrying capacity of notched components. As the test material was used steel Fe510 according to EN ISO (11523, according to CSN 42 0002).

Presented research paper is focused on the development of train front end cab, specifically on choice of material composition and production technology. Experimental part deals with a selection of the most appropriate multiaxial fabric based on its saturation by resin and type of polyester resin most suitable for low-pressure vacuum infusion. This technology is chosen with respect to dimensions of the part, resin savings (compared to hand lay-up technology) and also production cost of the cab. Prepared samples are evaluated regarding to the progress of production technology, part face quality (voids, dry spots, and delamination) and technological properties. As a result, optimal material composition for front end cab production is chosen and fabrication of prototype cab is conducted.

Mechanical alloying is one of the ways how to prepare nanostructured and amorphous metallic materials. In this paper we used this method to prepare Mg-Zn alloy containing 50 wt.% of zinc. Powders produced by milling in a planetary ball mill were consequently compacted by the SPS method, a very fast method which prevents grain coarsening. The prepared samples were subjected to a closer examination - microstructure, phase composition, hardness and short-term thermal stability were studied. We found out that the prepared powder consisted of Mg and Mg7Zn3 phases, which were very fine and homogeneously distributed. After the SPS compacting, the metastable Mg7Zn3 phase decomposed and new phases (Mg, MgZn, MgZn2, Mg2Zn11) formed. The compacted sample possessed relatively inhomogeneous microstructure and hardness about 260 HV5. Investigation of the short-term thermal stability was accomplished by annealing at temperatures up to 300 °C. We observed changes in hardness - it regularly decreased up to 200 °C and then it slightly increased.

This article deals with the non-destructive ultrasonic testing of split sleeve butt joints by ultrasonic methods. Split sleeve is used to repair gas pipelines with gas leakage. The new ultrasonic methods TOFD and Phased Arrays are compared considering to the selected butt weld configuration. To compare testing methods, ES Beam Tool software was used to prediction of ultrasonic beam spread through weld joint. TOFD technology was selected to butt weld section testing according to the beam spread simulation results. The results of ultrasonic testing by TOFD method were compared with results of macrostructural analysis of weld joint. Controlling the suitability of testing method to planar defect identification, the artificial defects were prepared and tested. The appropriate setting of measuring technique can be predicted from experimental results.