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Honourary Staff (in alphabetical order) bensabra hakim (algeria), BORDEA MARIUS, chabour salem (algeria), gencang yang (china), R. S. HOUK (S.U.A.), I. IMRIŠ (TECHNICAL UNIVERSITY OF KOŠICE, SLOVAK REPUBLIC), puşici miho (Slovenia), roşescu gheorghe (grecia), roxana ruxandra (california), w.m. nicola (tri. state university angola, indiana, s.u.a.), xianqing you (china)
romanian metallurgical foundation Scientific publishing house editorial board : Prof. colan horia Ph. D., member of Romanian Academy of Technical Sciences Prof. Coşmeleaţă georgeta Ph. D. Prof. Elena drăgulănescu Ph. D., Catedra GDGI, Aerospatial Engineering Faculty, Bucharest Politechnical University Prof. Dumitrescu Constantin Ph. D., deputy member of Romanian Academy of Technical Science Prof. French David Ph. D., CSIRO Energy Technology, Australia Prof. Găluşcă Dan-Gelu Ph. D. Prof. Mihaela Grigore Ph. D., University of New South Wales, Sydney, Australia Prof. Lawson Cristopher Ph. D., Copenhague Technical Institute, Denmark Prof. Nicolae Avram Ph. D. Prof. Maria Nicolae Ph. D. Prof. doc. Oprea Florea Ph. D., member of Romanian Academy of Technical Sciences Prof. Veena Sahajwalla Ph. D., University of New South Wales, Sydney, Australia Prof. Sakurovs Richard Ph. D., CSIRO Energy Technology, Australia Prof. Salvo Luc Ph. D., Grenoble National Politechnical Institute, France Prof. Saiter Jean-Marc Ph. D., Rouen University, France Prof. Scorţea Costin Ph. D. Prof. Simiti Ioan Vida Ph. D. Prof. Sofroni Laurenţie Ph. D., member of Romanian Academy of Technical Sciences Prof. Şaban Rami Ph. D., Dean of Materials Science Faculty, Bucharest Politechnical University Prof. ŞTEFĂNESCU DORU Ph. D, Ohio State University Columbus, S.U.A. advisory board : Prof. bejan Mircea Ph. D Prof. cănănău nicolae Ph. D Prof. hepuţ teodor Ph. D Prof. Doina Răducanu Ph. D Prof. samoilă Corneliu Ph. D Prof. SOFONEA GALAgTION Ph. D Managing Director: Editor-in-chief: Professor Scorţea Costin Ph. D. Manager Scientific Publishing House F.M.R.: eng. Florentina Brânduşa Scorţea		Contents Issn 1582 – 2214 Nadia A. Badr: The role of stabilizing elements on the tensile bond strength and electrochemical behavior of assembled Nickel-Chromium Ceramo-Metal alloys during joining and after simulating porcelain firing cycles ……………………. 5 GÂRLEANU Gabriel, Delia GÂRLEANU, CALEA Gheorghe, Nicolae Avram: Booth for the welding stresses from the welded joints using ultrasonic actuators …….…. 20 Agop Maricel, VIZUREANU Petrică, Nica P., Mamut Eden, Ioannou P. D.: Hydrodynamic model of scale relativity theory for nanomaterials. (II) The anomaly of the heat transfer in nanofluid by means of a differential negative thermal conductance ………………….… 24 Nedelcu Dorian: Numerical study of the local stress for a circular fillet corner .... 30 ? FOSECO Turbostop system – reference list …I-II ? Press Release…….................…..……............ III - X ? New books, published by romanian metallurgical foundation……………….……….....…...... XI - XII

abstract

metalurgia International 3/2007

Key words: assembled Nickel-Chromium Ceramo-Metal alloys Nadia A. Badr: The role of stabilizing elements on the tensile bond strength and electrochemical behavior of assembled Nickel-Chromium Ceramo-Metal alloys during joining and after simulating porcelain firing cycles Metalurgia International (vol. XII), no.3, 2007, p. 5 Purpose: This study aimed at deducing the effect of Nb and Ta elements in Ni-Cr ceramo-metal dental casting alloys during exposure to high temperature as in joining two components and after porcelain firing cycles. The investigated alloys were assembled by soldering or cast connection techniques. The tensile strength at the junction and its electrochemical behavior were studied. Materials and methods: A total of 40 full length specimens were constructed using two Ni-Cr and Be free base metal alloys, 20 for each investigated alloys. Half of the specimens were assembled by soldering technique (group I) and the other half were assembled by cast connection technique (group II). Each group was further subdivided into two equal subgroups (n=5) to be tested before and after porcelain firing cycles. The tensile bond strength was calculated. Potential resistance, corrosion rate and potentiodynamic behavior were determined. XRD analysis of the fractured surfaces was used to detect phases and the grain size. EDX was used for qualitative and quantitative analyses of the elements. Results: The tensile bond strength showed insignificant difference either between the used alloys or before and after exposure to porcelain firing cycles. However, the cast connection technique resulted in higher significant tensile strength values than those of soldered ones. The electrochemical behavior and corrosion rate of both used alloys showed comparable results with slight improvement in the corrosion resistance after porcelain firing cycles. Cast connection group showed higher electrochemical activity than soldered ones. Conclusion: Presence of Nb and Ta has enhancing effect on the tensile bond strength while it seemed that they slightly affect the electrochemical properties. D.C.: 574 GÂRLEANU Gabriel, Delia GÂRLEANU, CALEA Gheorghe, Nicolae Avram: Booth for the welding stresses from the welded joints using ultrasonic actuators Metalurgia International (vol. XII), no.3, 2007, p. 20 The work presents the booth for the welding stresses from the welded joints, using ultrasonic actuators, designed and

manufactured uses the protocol of a method recognized and formalized by the branch of knowledge strength of materials “Blind Hole Drilling” This stand contains an ultrasonic actuator, which allows some measurements through many methods simultaneously of the size of the displacement at release of the welding stresses. D.C.: 66.015.24 Agop Maricel, VIZUREANU Petrică, Nica P., Mamut Eden, Ioannou P. D.: Hydrodynamic model of scale relativity theory for nanomaterials. (II) The anomaly of the heat transfer in nanofluid by means of a differential negative thermal conductance Metalurgia International (vol. XII), no.3, 2007, p. 24 Considering that the motion of the micro-particles takes place on continuous but non-differentiable curves, i.e. on the fractals, the dynamics of the fluid/nano-particle interface was analyzed. In the general case, the heat transfer through the interface reproduces a d.c. or an a.c. Josephson effects of thermal type, while in the linear approximation, the standard form of heat transfer results. Consequently, the interface is self-structuring and a negative differential thermal conductance appears. Since through self-structuring the interface releases heat to the environment, in our opinion it explains the anomaly of the heat transfer in nanofluids. Key words: circular fillet corner Nedelcu Dorian: Numerical study of the local stress for a circular fillet corner Metalurgia International (vol. XII), no.3, 2007, p. 30 The components from the engineering domain include section variation due specific elements (thread holes, grooved wedge, thrust collar, etc.), where the experimental and theoretical studies show local stress with increased values comparative with the calculated stress values by classical resistance formulas. The paper present a numerical study of the local stress for a circular fillet corner with tensile force applied on a rod shaped and comparative results of the numerical and experimental data.

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