Pero Raos

Influence of cooling conditions on the machining process under MQCL and MQL conditions

Original scientific paper The paper presents the results of investigation of the influence of conditions of forming emulsion and oil mist on the chip shape and surface roughness of X10CrNi18-8 stainless steel during turning. In the tests, the following machining operations have been compared: dry machining, cooling by the MQCL (Minimal Quantity Cooling Lubricat) method, cooling by the MQL (Minimum Quantity Lubricat) method. The tests have been performed in two stages. In the first stage, the influence of the mass flow of the active medium on the chip shape and on the Ra and Rq roughness parameters of the machined surface have been determined. The purpose of stage two was to determine the influence of the MQL and MQCL method on the selected indices of the machining process as compared to dry machining as a function of variable cutting speed. It has been found that, under MQCL and MQL conditions, the area of formation of elemental chips and ones with the shape of short spirals is wider as compared to dry turning. With increased mass flow of emulsion and oil, tangled chip is formed. Cooling by the MQCL and MQL method results in reduction of the selected roughness parameter values by 2 % to 42 % as compared to dry machining.

Different Approach to the Aluminium Oxide Topography Characterisation

Different surface topographic techniques are being widely used for quantitative measurements of typical industrial aluminium oxide surfaces. In this research, specific surface of aluminium oxide layer on the offset printing plate has been investigated by using measuring methods which have previously not been used for characterisation of such surfaces. By using two contact instruments and non‐contact laser profilometer (LPM) 2D and 3D roughness parameters have been defined. SEM micrographs of the samples were made. Results have shown that aluminium oxide surfaces with the same average roughness value (Ra) and mean roughness depth (Rz) typically used in the printing plate surface characterisation, have dramatically different surface topographies. According to the type of instrument specific roughness parameters should be used for defining the printing plate surfaces. New surface roughness parameters were defined in order to insure detailed characterisation of the printing plates in graphic reproduction process.

Stress-Strain Analysis of Single-Lap Tensile Loaded Adhesive Joints

Both, experimental investigation and finite element analysis of single‐lap adhesive joints subjected to tension have been done to find out an optimal overlap length. As the adherend material aluminum was considered with the two component high‐strength engineering adhesive for the bonding of the layers. The thickness of the sheet metal layer was 1,95 mm, while adhesive was 0,15 mm thick. The width of all thin plates was 30 mm, but the overlap length varied as 15, 20, 30, 40 and 60 mm. Real mechanical properties of all materials in the joint have been determined experimentally. Obtained results proved that the overlap length affects directly the joint tensile strength, where an optimum value of overlap length can be defined. Finite element analysis of stress and strain fields could help to determine the moment when the crack initiates at the joint overlap end. In such a manner, complex mechanisms of failure of adhesive joints could be better understood.

Utjecaj mjerne pogreške plinomjera na obračun potrošnje plina

Preliminary notes Natural gas is one of the most important energy sources of the modern age. Gas network delivers gas from the exploitation site to the end user. Flow meters are used to measure quantity of gas supplied and they must meet firm standards regarding measurement. G4 gas meters used in housholds are investigated in test laboratory. Experimental results are analyzed in this paper and conclusions about correlations between measurement error and gas meter type, years in operation and flow dialer reading are given. Error measurement is also expressed as amount of natural gas delivered to end users.

HS 6-5-2 steel surface layer development in carbonitriding with ZeroFlow method

Original scientific paper The paper reviews the process of surface layer development with the use of carbonitriding and carbonitriding with oxidation. Employed for that purpose was a modern and ecological method called ZeroFlow. Research was carried out using HS 6-5-2 steel. Single-component nitrifying atmosphere of ammonia NH3 was applied. The temperature of the processes was 570 °C. Diffusion layers were obtained on the steel. The thickness of the layers achieved during the microstructural research equalled from about 125 μm after carbonitriding with oxidation to about 187 μm after carbonitriding. Surface hardness HV1 was the highest for the carbonitrided layer 1027 HV1, whereas in the case of carbonitriding with oxidation it amounted to 1018 HV1. As far as surface hardness HV30 is concerned, it was at the level of 813 HV30 for the carbonitrided layer and 795 HV30 for carbonitriding with oxidation. Surface hardness test results indicate surface layer hardening.

STUDY ON THERMAL PROPERTIES OF SYNTHETIC AND BIO-BASED POLYURETHANE

Polymers that are created by the chemical polymerization of naturally occurring monomers are attracting considerable commercial interest in the last few years because of their non-toxicity, biodegradability and biocompatibility and use of feedstock that is renewable. The development of specialized lignin compounds, such as electrically conducting polymers, engineering plastics and polyurethane, is an area of highest interest and growth. The paper will present the comparison of the mechanical and thermal properties of conventional polyurethane and bio-based polyurethane, i.e. polyurethane based on polyols produced by liquefaction of waste wood biomass.

Application of Advanced Virtual Reality and 3D Computer Assisted Technologies in Computer Assisted Surgery and Tele-3D-Computer Assisted Surgery in Rhinology

The contribution deals vith application of virtual reality technology and computer assisted surgery in rhinology

Dynamic behaviour of the turning process

Abstract Estimation of dynamic behaviour of the turning process is of great interest in hard material machining. In hard turning, when depth of cutting and feed have low values, lead edge angle and passive force F p are strongly dependant on real time value of cutting depth. Experimental tests and numerical modelling of tool/work piece contact line have been done to evaluate the rate of cutting instability while using and comparing different process monitoring sensors, and acquisition techniques. It was found that high chip thickness alteration occur because of cutting depth that vary for a value of some 60 %. Even higher alteration of F p force signal is recorded when machine tool has inadequate stiffness. If a hard turning is a semi-finishing or finishing process, surface finish is of big relevance. Surface roughness is a consequence of both cutting instability and of tool/work piece loading condition. The results of test indicates, that an optimal cutting depth for final pass, when minimum surface roughness can be achieved, can be valuable for cutting regime determination.

System Analysis and Morphological Classification of Procedures and Molds for Injection Molding

Abstract The theoretical foundation of system analysis is given after historical development of the problem. The key concepts and the technical systems of things are discussed. Based on investigated procedures of injection molding of polymers and other matters a general definition of injection molding is given. This enables us to work out the general model of injection molding of matter, as well as the system analysis of molds for injection molding. From this analysis, it follows that the mold has different functions: primary shaping of the product as well as structuring on the molecular and supramolecular level. The mold is at the same time a very complicated and complex technical system of things. The morphological classification of different systems gives the basis for better process control.