Wyniki wyszukiwania - Biblioteka Nauki

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Application of multiple regression and neural networks to synthesize a model for peen forming process planning

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Delijaicov S. , Fleury A. T. , Martins F. P. R.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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tom Vol. 43, nr 2

651--656

EN

Purpose: this paper aims to present a simple method to synthesize an empirically-based model that permit to estimate the maximum displacement of a plate when a shotpeening process values are known. Design/methodology/approach: This approach regards the difficulty to develop a mathematical model to describe the relationship between the shot peening process variables (shot diameter, impact velocity, static preload and coverage) and the curvature of the piece. Such a model was generated through the application of statistical inference methods - multivariable regression and neural networks – to a set of experimental data concerning the application of peen forming processes to a group of 215 aluminium 7050 alloy rectangular plates. Findings: Although the estimated displacements from both models comply reasonably well with the experimental data, the obtained results exposed the superiority of the regressive model concerning accuracy. Research limitations/implications: Shot peen forming, a die less forming process, is one of the most successful methods to produce slight and smooth curvatures on large panels and plates. Through the application of a regulated blast of small round steel shot on the piece surface, a thin internal layer of residual compressive stress causes the elastic stretching of the shotted surface, giving rise to a permanent non-plastic deformation of the whole piece. Although this forming process has been used since the fifties, especially by the aerospatial industry, a scientific method for peen forming process planning has not been developed yet. Originality/value: The referred model can be used as an engineering tool to aid setting up a peen forming process in order to produce a desired curvature on a given plate.

2

Improved model to predict machined surface roughness based on the cutting vibrations signal during hard turning

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Delijaicov S. , Leonardi F. , Bordinassi E. , Batalha G.

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2010

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tom Vol. 45, nr 2

102-107

EN

Purpose: The objective was to study the influence of cutting vibrations in hard turning of AISI 1045 steel. Design/methodology/approach: A design of experiments using a complete factorial was used in the experiments. The specimens were tempered and quenched with 53 HRC. A piezoelectric dynamometer for turning with an acquisition data system was used in the measurements. Findings: The results showed excellent correlation between the model and results and showed that the frequency amplitudes increase the model reliability by 5%. Research limitations/implications: The instrumentation of machine and its correlation with the amplitudes of frequencies from data system acquisition could personalize the models for each experiment on the machines. Originality/value: The paper uses a commercial piece and provides important information for the improvements in the roughness of hardened steel, which is an important factor for the components surface integrity.

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Surface integrity functional analysis in hard turning AISI 8620 case hardened steel through 3D topographical measurement

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Farias A. , Delijaicov S. , Batalha G.

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tom Vol. 46, nr 1

47-52

EN

Purpose: This work aims investigate the resulting machined surface condition from hard turning process of mechanical components manufactured from case hardened steel. Design/methodology/approach: The surface was examined by parameters obtained from the three-dimensional surface topography obtained with an interferometric laser instrument. Findings: The selected roughness parameters analysis intends to have a functional characterization such as bearing capacity, fluid and lubricants retention ability and contact wear resistance. Research limitations/implications: The obtained results were validated against similar ones, showing that the employed measuring techniques and analyses were correctly conducted. Practical implications: The functional bearing area curve analysis parameters indicates that the resulting surface has a good area contact, good bearing capacity and reasonable ability to fluid retention as the reduced valley depth parameter Svk not produced higher values for all conditions tested. Originality/value: The obtained results in the surface roughness measurement shows consistency with other authors results, and it shows that the technique of hardened material turning is capable of producing surfaces with functionality and quality.

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Superficial integrity analysis in a super duplex stainless steel after turning

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Bordinassi E. C. , Stipkovic M. F. , Batalha G. F. , Delijaicov S. , Lima de N. B.

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tom Vol. 18, nr 1-2

335--338

EN

Purpose: Purpose of this paper was to study the main effects of the turning in the superficial integrity of the duplex stainless steel ASTM A890-Gr6A. Design/methodology/approach: The focus of the work was the finishing operations and a complete factorial planning was used, with 2 levels and 5 factors. The tests were conducted on a turning center with carbide tools and the main entrances variables were: tool material class, feed rate, cutting depth, cutting speed and cutting fluid utilization. The answers analyzed were: micro structural analysis by optical microscopy and x-ray diffraction, cutting forces measurements by a piezoelectric dynamometer, surface roughness, residual stress by x-ray diffraction technique and the micro-hardness measurements. Findings: The results do not showed any changes in the micro structural of the material, even when the greater cutting parameters were used. All the other answers were correlated with the cutting parameters and its better combination was founded for the best superficial integrity. The smaller feed rate (0.1 mm/v), smaller cutting speed (110 m/min) and the greater cutting depth (0.5 mm) provided the smaller values for the tensile residua stress, the smaller surface roughness and the greater micro-hardness. Research limitations/implications: The correlation between all the answers was very difficult to analyze because there was great interaction between the factors, but for some data group it was possible. Originality/value: The paper contribute for the study of the super duplex stainless steel, considering that no one researches was founded for the studied topics in this material in witch presents different behavior in machining when compared with another stainless steels.