A categorization has been proposed of the welded joints depending on the type and character of loading and the needed safe- ty requirement of the structure of which they are an integral part. Four “production requirement grades”: “PRGs”, have been intro- duced. They allow the objective grading of welding requirements put forward towards the preparation of each and every welded joint for which the loading and operation conditions are familiar.
Machines. Technologies. Materials.
Vol. 8 (2014), Issue 10
Table of Contents
Results of the theoretical analysis of invariant criteria for evaluating the stress-strain state under specific mechanical schemes stresses and deformations on forming operations and their impact on the sustainable flow of processes of plastic deformation are presented
THE STUDY OF THE PROCESS OF COMPLEX DIFFUSION SATURATION WITH BORON AND VANADIUM ON THE CARBON STEELSpg(s) 7-8
The study investigates the formation of the diffusion layers and their properties on carbon steels after saturation with boron and vanadium in pastes. Metallographic analysis was performed with the use of the optical microscope “Neophot -21”.
Microhardness was determined by tester PMT-3M. X-ray spectral analysis was carried out by the electron scan microscope JSM-6510LV JEOL with microanalysis system INCA Energy 350.
Simultaneous Thermal Analysis (STA) unifies the simultaneous application of thermogravimetry and differential scanning cal- orimetry to one and the same wood sample in a single instrument, under perfectly identical conditions – same atmosphere, gas flow rate, pressure, heating rate, thermal contact, etc. A new thermal analysis approach to distinguish between the flaming and glowing combustion of wood was discussed. The results obtained by STA were used in a new way, to reveal the influence of plasma-aided capillary impregnation on thermal decomposition and glowing of wood controlled by oxygen and nitrogen containing flame retardant. New integral criteria of thermal behavior and decomposition such as specific enthalpy change, and specific heat flux or heat release rate, have been developed by investigat- ing three species rain-forest wood (Mérida, Yucatán) – Mexican white cedar (Cupressus Lusitanica); Caoba mahogany (Swietenia macro- phylla); and Tzalam (Lysiloma bahamensis).
Finite Element Method has been proved as valuable tool for solving different electromagnetic problems inside electrical machines. Calculation of magnetic flux density and its distribution in machine cross-section is difficult to be calculated by analytical methods. Therefore Finite Element Method is implemented for solving set off Maxwell equation which enables precise calculation of electromagnetic field and magnetic flux density in three different electrical machines: three phase squirrel cage motor type 5AZ801-4 prodct of company Rade Koncar, three phase distribution transformer type product of company EMO, and single phase capacitor motor FMR-35/6 product of company MikronTech. Distribution of magnetic flux density in all three machines is calculated for different operating regimes.
Geometrical synthesis of fine-module ratchet toothing in which the contacting surfaces of the teeth formed by the straight segments are considered. The proposed profile of fine-module ratchet teeth allows increasing the load capacity and manufacturability production. The formulas for determination of the main geometrical parameters of the proposed fine-module ratchet teeth are obtained.
IMPROVING THE UNIFORMITY OF PROPERTY DISTRIBUTION ALONG THE SURFACE OF FILTER MATERIALS OBTAINED USING POROGENSpg(s) 24-27
A method of obtaining filter materials from metal powders intended to significantly improve the uniformity of properties along their working surface has been described. The method is easy to perform and is based on granulating the initial powders by the porogen through transferring it into an aqueous solution. It eliminates the segregation of porogen in the bulk of the charge during the implementation of technological operations and enables the automation of the pressing process.
Since diffusion bonded joint is formed from atomic migration across an interface without a liquid phase, the interface is homogeneous microstructure and hence mechanical properties are not different from those of the matrix metal. However, it is not easy to control process variables at high temperature. This paper presents diffusion bonding process and a machinery with tool material selection to develop diffusion bonding press machine for joining complex contoured metals using hot forming and diffusion bonding technology.
A multi-agent Process Planning system for prismatic parts is proposed. This system consists of different basic agents and a negotiation protocol between the agents is described. The individual agents have the ability to communicate with other agents and make different decisions.
EXPERIMENTAL INVESTIGATION ON THE EFFECT OF COOLING AND LUBRICATION ON SURFACE ROUGHNESS IN HIGH SPEED MILLINGpg(s) 35-38
The article presents experimental investigations on the effect of cooling and lubrication conditions of the cutting zone on the surface texture after high speed milling of stainless steel 1.4301 and C45 steel in a wide range of cutting parameters. In the study three methods of cooling and lubrication were used: cooling with emulsion, minimal cooling and lubrication (MQL) and without emulsion – dry milling. The methodology and techniques of studies as well as their results and analysis of the effects of the investigated factors (conditions of cooling and lubrication and cutting parameters) on the geometric structure of the machined surface are presented. Conclusions regarding the impact of cooling and lubrication modes together with cutting parameters on the values of the analyzed surface parameters as well as their application recommendations are given too.
Investigated the wear resistance of coatings obtained by saturation with boron and copper under dry friction – sliding on the air, and found that the coatings obtained by saturation with boron and copper have 2 times better wear resistance than the coating after boriding. Found that the saturation of boron and copper complex provides optimal performance when wear boride phases, namely sufficient microhardness – 15.5 MPa, 0,5 0,5 low porosity, increase in viscosity layer, the value K reaches 2.1 MPa · m to compared with 1.2 MPa · m 1C without complex saturation and increasing stress chipping values to 290 MPa compared to 170 MPa for the boride layers.
Numbers of both ferrous and non-ferrous bimetal productions and applications have been increased due to useful advantages.
Bimetal fabrication techniques and procedures are developing and getting various. Liquid metal based techniques are in basic bimetal fabrication methods which have two types; liquid-solid and liquid-liquid processes. Lost foam casting technique can be successfully employed for both liquid-solid and liquid-liquid bimetal composite productions. In this work, A380 and A2014 aluminium alloys were used to produce bimetal structure by conventional lost foam casting with liquid-liquid process. There are two main principles of liquid-liquid process. First, both alloys are joined in liquid phase and solidified and second, crucibles tilting are carried out synchronously at the same time. HB hardness of the cast specimens were measured and micro structure of the joint field were observed.
Metal/metal composites are a group of promising composite materials with high developing and service potential. Especially in many fields they can be a powerful low cost alternative to metal/ceramic composites. The most commonly encountered type of these composites is steel reinforced aluminium matrix composites which stand out with high wear and abrasion resistance. Significant fabrication processes of metal/metal composites are based on liquid metal techniques. In this study, Al/steel composite specimens were produced by using vacuum assisted solid mould investment casting technique. A380 aluminium casting alloy were infiltrated into steel preforms, which were produced with H13 hot-work tool steel turnings, in the plaster based solid investment casting moulds. Micro structure observations, HB hardness measurements and XRD, EDS analysis were carried out for characterization.
WOOD SURFACE ENERGY DETERMINED BY SESSILE DROP TECHNIQUE AS QUALITY PARAMETER OF PLASMA-CHEMICAL MODIFYED WOOD SURFACESpg(s) 50-2
The analysis of pre-treated wood surfaces, which have been plasma modified is also very informative for wood quality. Our measuring instruments determine the wettability based on the contact angle. The optical shape analysis of drops which are dispensed onto the surface is a reliable method for carrying out this measurement. The aim of this study was to verify possibility of determining the contact angle values of the plasma activated wood and calculate the surface free energy and its components of wood from the obtained contact angle values using Zisman, Equation of state (EOS), Fowkes and Wu theory and calculation method. Based on the contact angle data, the surface energy was obtained from the polar-dispersive(non-polar) approach. This study has been created as part of a large investigation on plasma- chemically activated wood surface and flame retardant treated wood.
The experimental analysis of passive heat transfer intensification in the case of plate heat exchanger has been carried out. The passive intensification was obtained by a modification of the heat transfer surface, which was covered by a metallic porous microlayer. The experiment was accomplished in two stages. In the first stage the commercial stainless steel gasketed plate heat exchanger was investigated, while in the second one – the identical heat exchanger but with the modified heat transfer surface. The direct comparison of thermal and flow characteristics between both devices was possible due to the assurance of equivalent conditions during the experiment. Equivalent conditions mean the same volumetric flow rates and the same media temperatures at the inlet of heat exchangers in the corresponding measurement series. Experimental data were collected for the single-phase convective heat transfer in the water-water and water-ethanol configuration. The heat transfer coefficients were determined using the Wilson method.