Advanced Materials Research Vols. 264-265

Abstract: In this paper, the tool life and tool wear performance of PCBN tool in end milling of AISI D2 hardened steel under room and preheated machining conditions is presented. The tool life and tool wear patterns were examined through tool maker microscope and scanning electron microscope. The results show that the dominant modes of tool wear observed were flank wear, chipping, and notch wear. The main wear mechanisms were abrasion, adhesion, and diffusion promoted by high stress and cutting temperature. It was also observed that longer tool life and higher volume metal removed could be achieved when employing higher preheating temperature.

Abstract: This paper proposes a multi-criteria optimization technique using the mathematical models developed by the response surface methodology (RSM) for the target responses combined with desirability indices for the determining the optimum cutting parameters in end milling of AISI D2 hardened steels. Different responses may require different targets either being maximized or minimized. Simultaneous achievement of the optimized (maximum or minimum) values of all the responses is very unlikely. In machining operations tool life and volume metal removed are targeted to be maximized whereas the machined surface roughness need to be at minimum level. Models showing the combined effect of the three control factors such as cutting speed, feed, and depth of cut are developed. However, a particular combination of parameter levels appears to be optimum for a particular response but not for all. Thus adoption of the method of consecutive searches with higher desirability values is found to be appropriate. In this study the desirability index reaches to a maximum value of 0.889 after five consecutive solution searching. At this stage, the optimum values of machining parameters - cutting speed, depth of cut and feed were determined as 44.27 m/min, 0.61 mm, 0.065 mm/tooth respectively. Under this set condition of machining operations a surface roughness of 0.348 μm and volume material removal of 7.45 cm3 were the best results compared to the rest four set conditions. However, the tool life would be required to compromise slightly from the optimum value.

Abstract: Experimental and numerical studies of fracture prediction with Czech steel no.41 2050 are presented. Seven ductile fracture criteria were calibrated, applied to simulation of rod cutting and bolt head trimming operation and compared with experimental results of these processes, obtained in semi-industrial conditions in cooperation with our industrial partner. Movement of the cutting tool was stopped in predefined positions, so that a step-by-step mapping of subsequent stages of both processes were obtained at different specimens. By metallographic analysis of these, full view of plastic deformation and damage in the vicinity of the cutting region could be seen, and their comparison with the computational results was done.

Abstract: In practice, there are a lot of factors that can affect the expected final outcome of machining processes. That is why during last decades a great number of experimental studies have been made for improving this kind of processes. As the realization of the tests for taking into account factors such as machines, materials, tools and cutting conditions requires resources of different types and can provoke environmental damage at different levels, diverse methods of experimental design and statistical analysis have been developed looking for efficient experimentation. This paper is focused on the study of these statistical methods. It collects the principal types of experimental designs and statistical procedures used in experimental studies for the control and the improvement of machining processes. Additionally, the review and analysis of the main works on the machining processes area for each one of these statistical tools has been made.

Abstract: A new EDM method of small hole is presented in which critical size of EDM drilling can be reduced less than that of limit of primitive EDM system by current dividing. The drilling characters of small hole EDM by means of current dividing based on a principle of discharging-area equalization were studied and discussed. The experimental results show that drilling speed and discharging gap decrease a little, and electrodes wear increases slightly. There is a drilling consistency in EDM ability between single and double electrodes under discharging-area equalization, and new method helps to improve the drilling precision. The research outcomes provide a deeper understanding for a small hole EDM.

Abstract: The aluminium alloys are widely employed in the aeronautical, aerospace and automotive industries in the most important manufacturing processes. This is due to the fact they have a high resistance even at high temperatures as well as a low density. Nevertheless, these materials can commonly show problems associated with the heat generated during the machining process that reduces their machinability. For this reason, cutting fluids are still widely used. However, the growing social preoccupation towards environmental conservation has made it necessary to develop cleaner production technologies as dry machining, in which no cutting fluids are employed. This situation makes necessary to look for combinations of cutting parameters and types of tools that improve the machining in those extreme work. In this study, the UNS A97050-T7 and UNS A92024-T3 aluminium alloys were analyzed in terms of surface roughness and the morphology of chips obtained, using tools with TiN coating. It was found that the surface quality of the aluminium UNS A97050-T7 and UNS A92024-T3 bars improves with the descent of the feed and with the increase of the cutting speed, being the feed the cutting parameter more influential on the surface roughness. Thus the machining of the UNS A92024-T3 allows obtaining shorter chips than the UNS A97050-T7.

Abstract: This paper investigates the effect of the CBN abrasive types, sizes, concentration, bond amount, and porosity of a vitrified-bonded CBN wheel on grinding ratio, grinding forces, and surface roughness of grinding hardened steels. The experiment results showed that during grinding hardened steels the amount of bond with increase of the depth of cut increased, which makes the wheel to have a better bonding strength to get a better grinding ratio and surface roughness of the workpiece. The grinding forces produced increased with the increase of the depth of cut. In addition, too much porosity of a vitrified CBN wheel will cause the low bond strength, leading the wheel to wear rapidly. Hence, to obtain a higher grinding ratio and better surface roughness of the workpiece during the grinding hardened steels should select relatively a higher amount of bond, a lower porosity, and a higher grit strength and concentration, but the grinding forces produced were relative higher.

Abstract: Life cycle engineering is the engineering and design of products and processes to minimize the cost and environmental impact for the life cycle phases of a product. Relevance Vector Machine method (RVM) is used to determine recycling strategy (reuse, service, remanufacture, recycle with disassembly, recycle without disassembly and disposal). Seven parameters (wear – out life, technology cycle, level of integration, number of parts, reason for redesign and design cycle) were considered as the input for the RVM model. Three electronic equipments were selected to be examined such as vacuum cleaner, washing machine, television. All the results verify previous literature study. The prediction model predicts the end of life (EOL) strategies quite closely with real industry practices.

Abstract: The environmental problem is an extensive, complex problem, and some example areas of study are energy consumption, material/resources use, recycling, and environmentally relevant substance control. Life cycle engineering is the engineering and design of products and processes to minimize the cost and environmental impact for the life cycle phases of a product. Functional Radial Basis Function Networks (FRBFN) is used to determine recycling strategy (reuse, service, remanufacture, recycle with disassembly, recycle without disassembly and disposal). Seven parameters (wear – out life, technology cycle, level of integration, number of parts, reason for redesign and design cycle) were considered as the input for the FRBFN model. Eight equipments were selected to be examined such as vacuum cleaner, washing machine and television. All the results verify previous literature study. The prediction model predicts the end life strategies quite closely with best industry practices but only 25 % match average industry practices.

Abstract: Electrical discharge machining (EDM) technique has been widely used in modern metal working industry for producing complex cavities in dies and moulds, which are otherwise difficult to create by conventional machining. The process has the advantage of being able to machine hardened tool steels. However, its low machining efficiency and poor surface finish restricted its further applications. To address these problems, one relatively new technique used to improve the efficiency and surface finish is EDM in the presence of powder suspended in the dielectric fluid. Powder mixed electric discharge machining (PMEDM) is one of the recent innovations for the enhancement of capabilities of EDM process. In PMEDM, the electrically conductive powder is mixed in the dielectric fluid of EDM, which reduces the insulating strength of the dielectric fluid and increases the spark gap between the tool and workpiece. As a result, the process becomes more stable, thereby, improving the material removal rate (MRR) and surface finish. Moreover, the surface develops high resistance to corrosion and abrasion. This paper presents the current research trends on dry, near dry EDM and review on research carried out in the area of PMEDM.