This paper presents a multinomial model for a special case of the machine interference problem (MIP), where each of N identical machines randomly requests several different service types. The model allows the calculation of the expected interference time in the queue for each service type. The extended version of the model allows calculation of the exact distribution function of the steady state waiting time and total service time for each type of requested service. In addition, the model can be adjusted for the case where the service is provided by a group of K identical operators, each operator is capable to handle all types of service, but each service type has a different priority.
Machines. Technologies. Materials.
Vol. 10 (2016), Issue 1
Table of Contents
THREE-DIMENSIONAL S-N CURVE METHOD TO ESTIMATE FATIGUE LIFE OF EN AW 6063.T66 ALUMINIUM ALLOY DURING COMBINED LOADING UNDER IN-AND-OUT OF PHASE SHIFT 0° AND 90° AND COMPARING WITH FATIGUE CRITERIApg(s) 7-10
The article deals with determining of fatigue lifetime of structural materials during by multiaxial cyclic loading. The theoretical part deals with the fatigue and with criteria for evaluation of multiaxial fatigue lifetime, especially Fatemi-Socie, Smith-Watson-Topper, Brown-Miller and Liu. The experimental part deals with testing of specimens for identification of the strain-life behaviour of material and determining the number of cycles to fracture of aluminium alloy for phase shift 0° and 90°. Extensive fatigue experiments were conducted using 6063.T66 aluminium alloy under multiaxial bending-torsion loading.
Based on the analysis of the initial equations of the plastic state,established the distribution of strains in the initial and final stages of axisymmetric drawing. The dependencies to assess the accuracy of linear and diametrical sizes taking into account volumetric of strain state.
The purpose of this paper was to study the regularities of formation of ultrafine structure in alumina by magnetic pulse compaction (MPC) and spark plasma sintering, and the producing of nanostructured compacts having high density and microhardness. The combined application of two technologies magnetic pulse compaction and spark plasma sintering in the practice of compacting powders is very rare and unique. We have studied the microstructures of consolidated alumina samples. The anomalous zones present in volume of magnetic pulse compacted and spark plasma sintered samples of both types α and δ phases of alumina. The microstructure of the fracture surface between anomalous zones depends on the phase state of the particles of the initial powder. MPC of δ-alumina leads to a more uniform distribution of anomalous zones along diameter compact after SPS. MPC of α-alumina leads to an increase of the microhardness on the surface of compacts.
The report focuses on the process of obtaining closed cell aluminum foam by introducing a composite material obtained by high energy mechanical treatment in a planetary mill into the melt. In contrast to known methods, the paper describes the foaming performed by introducing compressed precursors based on aluminum into the melt. Air-atomized aluminum powder and titanium hydride were used as raw materials for the production of precursors, AK5M2 silumin melt was used for the basis. Implementation of these works does not require the creation of a protective atmosphere and equipment for hot pressing. Photographs of the samples’ appearance and study results have been presented. It has been shown that the method of introducing mechanocomposites into the melt may be used for the manufacture of closed cell aluminum foam.
CREATING NANOSTRUCTURED SUPERHARD AND HEAT-RESISTANT SURFACE LAYERS ON CARBON TOOL STEEL AT INFLUENCE TO INTENSE ELECTRON BEAMSpg(s) 20-22
The saturation of the surface layers of metals and alloys boron is conducted with the purpose of increase of their surface hardness, wear resistance, etc. Multicomponent layers containing in its composition borides of refractory metals, as a rule, formed by the methods of chemical-thermal processing in the interaction boriding component with refractory or by saturation boron refractory impurities metal or alloy.
In this work, we studied the features of formation of vanadium and iron borides on the surface of instrumental steels U8A and R18 under the influence of intense electron beams in continuous and pulse modes.
MODELING AND OPTIMIZATION OF THE COMPOSITION OF TITANIUM -BASED ALLOYS BY APPROXIMATION WITH REGRESSION MODELSpg(s) 23-25
The article is dedicated to an approach optimizing a task of statistical modeling of the mechanical properties of products in real production metallurgy design. The approach is designed for the benefit of producers-metallurgists aimed at providing panels of Ti – alloys of a specific set of eventual industrial properties. This is accomplished by a procedure of composition optimizing based on existing certificates of brands Ti – alloys. The article presents an approach using mathematical models of optimization problem following the implementation of approach the classical methodology capable of decision-making in the production practice.
The aim of this study is to investigate the design of continuous fiber reinforced composite pipes, produced by filament winding technique. For this purpose, the full factorial experimental design was implemented. When designing filament winding composites three major factors are the most important: fiber orientation, fiber tension and velocity of the filament winding. The ultimate target is to achieve the composite pipes with good characteristics as bearing material for construction with the lowest possible weight. Preparation of the composites was done by applying the 23 full factorial experimental design. For the purposes of these investigation, eight test specimen configurations are made and on the basis that, test results should provide material properties useful in the design stage. The velocity of the filament winding was taken to be the first factor, the second – fiber tension and the third – winding angle. The first factor low and high levels were chosen to be 525 m/min and 21 m/min, respectively, for the second factor – 64 N and 110 N, respectively and for the third factor – 100 and 900, respectively.
In tensile machines to measure the change in length of the specimen during the stress, most time extensometer and various contact methods and tools, such as strain gauges are used, but these methods have limitations and low accuracy that cause unexpected and different results from the theoretical values for the strain. In this paper, to address this shortcoming and improve strain measurement, a non-contact method using image processing techniques in the MATLAB environment is introduced. for this purpose after capturing a move of tensile test and converting that in to some high quality pictures and using image processing we put some pattern in the first image and with using a special algorithm with name of Digital Image Correlation (DIC) detect that patterns until the last image then we can use of displacement algorithm and calculate change in the specimen’s length and after that we can also have “Strain” with using these values.
The results of performed analysis and the study of analytical methods for assessing the precision of the measuring system are presented in this paper. Studies are related to the methods for assessing the precision based on the range calculation and the method of variances analysis (ANOVA).The importance of each factor in variation inducation in the measurement process is estimated by applying both methods in the analysis of the same measured sample. In order to assess the accuracy and efficiency of the applied methods, the obtained results are compared, which is the basis for obtaining specific conclusions.Reliability of the obtained results from the investigations are verified by applying the tools of programming package MINITAB.
THE RESISTANCE OF AISI 316Ti STEEL TO PITTING IN 1 M CHLORIDE ACIDIC SOLUTION IN THE ABSENCE AND PRESENCE OF INORGANIC INHIBITORpg(s) 36-38
AISI 316Ti stainless steel is prone to local corrosion in aggressive chloride environments. Its resistance to pitting in the absence and presence of molybdate inhibitor was tested by two independent tests with different mechanisms of corrosion process: by exposure (24 hours immersion test) and electrochemically (potentiodynamic polarisation test). Both tests were carried out in 1 M chloride acidic solution without inhibitor and with two different amounts of added inhibitor (concentration ratio inhibitive/aggressive anions was 1:10 and 1:20 respectively), at room temperature. Results of immersion tests were evaluated on the bases of corrosion rates calculated from corrosion losses during immersion and by morphology of pitting. Results of potentiodynamic polarisation tests were evaluated by pitting potentials.
STRUCTURAL, ELASTIC AND ELECTRONIC PROPERTIES OF Cu2MnZ(Z=Al, Ga, In, Si, Ge, Sn, Sb): A FIRST- PRINCIPLES STUDYpg(s) 39-40
The structural, elastic, electronic and phonon properties of Cu2MnZ (Z=Al, Si, Ge, Ga, Sn, Sb, In) are investigated by first-principles calculations based on density functional theory. In this approach the local-density approximation (LDA) and generalized gradient approximation (GGA) are used for the exchange-correlation (XC) potential. The calculated lattice constant, bulk modulus, and elastic constants are in agreement with the previous ab-initio calculations and available experimental results. Electronic properties are discussed from the calculations of band structure and density of states. The direct method is used to derive the phonon frequencies and density of states.
INVESTIGATION OF EFFECT OF TEXTURE ON COLD RESISTANCE OF NEW GENERATION STEELS FOR BUILDING STRUCTURESpg(s) 41-43
Due to technological particularities of low carbon low alloy API 5L X80 steels producing they have strong texture and its inhomogeneity on plate thickness. Charpy impact tests at ambient and negative temperatures and investigation of texture of samples of API 5L X80 steel were performed. By the method of X-ray structural analysis DPF, IPF and ODF were obtained. Texture components and their volume fraction were determined. It was shown that correlation between volume fractions of main texture components, misoriented grains fraction and DBTT exists. As a result analysis of texture parameters allowed characterization of effect of texture on cold resistance of low carbon low alloy API 5L X80 steel.
The process of low-temperature tempering has been studied by eddy current testing and measuring the hardness HRC at a constant temperature as well as at increasing temperature and duration. Technological factors of tempering were considered in their interdependence, according to the Hollomon-Jaffe equation. It has been argued that the factor levels, temperature and duration, are determined by the carburization and quenching results. Eddy current testing has been introduced as an indicator of quality with high sensitivity to changing technological factors; it has integral importance in terms of structural changes and electromagnetic properties of the parts. Hardness and electromagnetic characteristics, as indicators of quality after low-temperature tempering, were presented as a function of the tempering parameter Pa.
The plasma aided flame retardation of wood, wooden products and cellulosic fibrous materials has been conceived and developed as a result of plasma aided process of capillary impregnation with nitrogen- and phosphorous containing water solution. The surface pre-treatment in non-thermal equilibrium atmospheric pressure plasma substantially alters its electrical, chemical and capillary activity, thus improving some basic characteristics, such as penetration depth, water solution spreading and wicking, liquid adsorption capacity. This study has been developed as part of a large investigation on plasma-chemically activated wood surface and its capillary impregnation with nitrogen- and phosphor flame retardant containing water solution. It has been used to reveal and illustrate the impact of some ionic and silicon surfactant. The experimental studies of some chemical, ion and capillary activity changes of three species of rain-forest Mexican heart wood surfaces using selected surfactants and spreaders show that they have substantial contribution to the effective plasma-aided capillary impregnation processes.
CAPILLARY PENETRATION (SPREADING AND WICKING) MECHANISMS IN PLASMA-AIDED SURFACE FINISHING PROCESSESpg(s) 53-56
The plasma-aided flame retardation of wood, wooden products and cellulosic fibrous materials has been conceived and developed as a surface finishing process of capillary impregnation with nitrogen- and phosphorous flame retardant containing water solution. The surface pre-treatment in atmospheric pressure dielectric barrier discharge plasma substantially alters its capillary activity – the spreading on the wood surface and the wicking in the depth of wood, thus improving some basic characteristics of the impregnation process. This study has been developed as part of a large investigation on plasma-chemically activated (polarized, functionalized) wood surface and surfactants enhanced plasma aided capillary impregnation with nitrogen- and phosphor flame retardant containing water solution. The experimental studies of capillary activity changes on European white pine (Pinus Sylvestris, Bulgaria) wood surfaces using selected surfactants and spreaders show that they have substantial contribution to the effective plasma-aided capillary activity and impregnation processes.
EFFECT OF EQUAL-CHANNEL ANGULAR PRESSING ON CRACK RESISTANCE AND CORROSION DAMAGE OF ZIRCONIUM ALLOY Zr-2.5%Nbpg(s) 57-58
Testing method for static crack resistance has been developed and applied for thin sheet (sample thickness ~ 1mm) samples of zirconium alloy Zr-2.5%Nb. Linear parameter of fracture mechanics – stress intensity factor Kc has been determined. Alloy Zr-2.5%Nb after ECAP was tested for corrosion resistance in the physiological Ringer’s solution for two years.
In frame of the project KEGA 027STU-4/2014 at our institute, we are building a virtual laboratory of robotics. The main objective is to build a laboratory together with a set of training modules in the field of automation and industrial robotics that will serve to teach the principles of automatic control of manipulation and programming of industrial robots, which are now increasingly implemented in production practice. Built laboratory will develop the knowledge and expertise of students in the field of automated and robotic systems, application of innovative educational program and methodology of using modern technologies, including CA and e-learning.