Structural Integrity of Welded Structures XI

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Authors: Elena Simona Dogar Cutean, Ion Mitelea, Viorel Aurel Şerban, Cosmin Codrean
Abstract: Scratch test is one of widely used, fast, and effective methods to obtain the critical loads that are related to adhesion properties of coatings. The determination of adhesion and the scratch resistance is essential for the mechanical characterization of surface layers for research and industry. To evaluate the performance of coatings the scratch test with a Rockwell-C diamond stylus as indenter is a commonly used test for the characterization of hard coatings on predominant metallic substrates due to its comparatively robust experimental setup, the easy use and the representative results. This is the only technique capable of imaging such interface defects which are due to the stressin duced by the scratch experiment.This paper aims to characterize the adhesion and scratch resistance using Millennium200 - Technical Tribo equipment of Ti layer deposited on steel surfaces by means of TIG/WIG welding technique. Ensuring appropriate functional properties of WIG welding coatings (Ti) requires a good compatibility with the substrate material (S235). For this reason was used to deposit titanium WIG welding an intermediary layer of copper, obtained in the same experimental conditions. The optimal selection of the coating material takes into consideration the metallurgical, mechanical and process technology compatibility. The mechanical properties of coatings must match the substrate. From this point of view, maintaining a high corrosion resistance is mainly conditioned by achieving a good adhesion and a microstructure free of internal cracks or other defects.
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Authors: Ion Aurel Perianu, Ion Mitelea, Viorel Aurel Şerban
Abstract: This study presents investigations regarding processing X2CrNi18-9 stainless steel sheet with 2 mm thickness using abrasive waterjet cutting.By variation of base technological parameters (water pressure, travelling speed, abrasive rate and focusing tube inner diameter) the shape together with size of the kerf were analyzed.Roughness measurements from the entrance to exit of cut surfaces in correlation with the analysis carried out using an optical microscope highlights work hardening of the marginal layer. This phenomenon is less accentuated in the higher area which is in the vicinity of the focusing tube and intensifies towards the lower area of cut material.
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Authors: Emilian Stanciu, Doina Frunzaverde, Gilbert Rainer Gillich, Ionica Negru, Marius Tufoi
Abstract: The number and diversity of global nondestructive testing methods applicable to welded structures have rapidly increased in last decades. Vibration-based damage detection methods make possible the evaluation of structures at once; the damage location can be found without having direct access to the structure’s damaged region. Butt welded components often bring complexity in the structures, since the weld introduces cross-section shape changes and alteration of the material’s physical and mechanical characteristics. Moreover, the structure continuity can be interrupted by cracks or cavities. All changes occurring due to the weld induce mutations in the structures dynamical behavior. This paper presents a method to identify structural changes by using information from the modal analysis, actually analyzing the natural frequency shifts. Mathematical relations describing the individual or coupled effect of mass change and geometrical discontinuities are derived and used in the identification process; in fact, finding the mass changes or cracks becomes an inverse problem. The mathematical models are successfully tested on virtual and real structures.
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Authors: Victor Verbiţchi, Lia Boțilă, Cristian Ciucă, Ana Kostov, Aleksandra Milosavljević, Radiša Todorović
Abstract: In the frame of the Romania-Republic of Serbia IPA Cross-border Cooperation Programme, in the Project Ecosolder, the National Research & Development Institute for Welding and Material Testing - ISIM Timisoara, Romania, has elaborated a brazing procedure with a new ecological brass of the type B-Cu60ZnSnSiMn, elaborated by the Mining and Metallurgy Institute - MMI Bor, Serbia. The brazing test was carried out according to the standard EN 13134:2000 related to the brazing procedure approval. The applied process is oxygen-acetylene flame brazing of steel sheets, with the sizes of 87 mm x 80 mm, thickness of 1.0 mm and overlap 7 mm. Images of the execution of the brazing procedure are presented, with comments on every phase. The appearance of the joint is adequate, by the visual examination. By the metallographic analysis, the constituents of the deposited filler metal are dendritic solid solution, with fine particles of Sn, Si and Mn. No defects have been revealed. The values of the hardness are 91-133 HV1. The results of the specific shear test comply with the requirements. The technological, ecological, structural and mechanical characteristics of this filler alloy are adequate. Some applications of brazing with the new ecological brass are recommended.
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Authors: Emilia Florina Binchiciu, Traian Fleșer, Ionelia Voiculescu
Abstract: Brazing copper or copper-steel structures imposes measurements regarding deposits and base materials, and regarding the gas content, hydrogen and oxygen, that comes from the deoxidizing coat. The deoxidizing coat is made out of complex salts, hydroxides and acids with high hygroscopicity. Research effected in order to improve the deoxidizer capacity of the coat and to reduce its hygroscopicity, taking into account the ratio at coating of the rods, has highlighted the possibility of equipping the material with powders that have chemical active proprieties for deoxidizing processes at brazing. To this end we developed the pre-alloy type 48%Cu–47%Sn–4%P–1%Si, powder, grain size 0,05mm. The product was used, with a participation of 8% of the total coating mass, at manufacturing by extrusion of the new rods for brazing copper semi-products. We executed and characterized deep joints type copper-copper and copper-stainless steel.Brazing process results, have appreciated, detected by melted metal deposition tests, moistening angle and respectively of the mechanical characteristics of the achieved joints.Results have confirmed the above mentioned hypothesis; it highlighted superior values to those obtained with classic rods, at technical and technological proprieties.
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Authors: Ion Mitelea, Ion Dragoş Uţu, Daniel Ochian, Mircea Burcă
Abstract: Butt welding by TIG method using a low alloyed steel wire with solid state transformation point, G3Si1, having 1 mm diameter is a feasible solution for both unique and small series production and for saw blades reshuffling made of dissimilar steels (rapid steel HS 2-10-1-8 for the active part and X32CrMoV4-1 steel for the tool holder).This paper analyses the structural and chemical composition modifications occurred in the heterogeneous welded joints areas by endless saw blades. The phenomena which manage the continuous evolution of the weld chemical composition are highlighted by Energy Dispersive X-Ray Analysis (EDX) and Scanning Electron Microscopy (SEM).
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Authors: Cosmin Codrean, Aurelian Magda, Mircea Burcă, Dragoş Buzdugan
Abstract: In this paper will be presented experimental researches on development advanced alloys with amorphous structures based on Ni and Cu for resistance brazing joints. The main advantages of these amorphous alloys in shape of ribbons are their ductility and flexibility. These ribbons are obtained by ultra-rapid cooling of the melt. Using resistance brazing process, were obtained brazing joints of stainless steel and copper strips. The joints were mechanical and structural analysed. It was performed mechanical shear test on the brazed joints to establish the shear strength of the joints, and also it was performed structural investigation to emphasize the microscopic structure and the structural transformations that take place in the base material and brazing alloys during the brazing process.
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Authors: Oana Roxana Chivu Vîrlan, Corneliu Rontescu, Dumitru Titi Cicic, Mihai Vasile
Abstract: It is well known that, due to their working under severe conditions, the crankshafts in the automotive industry yield in the area of the crankpin journals and that buying a new crankshaft means high costs. Due to these reasons, various welding processes are frequently used for repairs. Certain welding processes are difficult to apply because the heat energy introduced into the parts during the welding process is very high and will lead to deformations and residual stresses and to structural changes. The paper contains the experimental results related to the effect of applying the WIG welding process to certain characteristics of the deposit layer: hardness, heat affected zone, structure etc.
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Authors: Elena Muncut, Ion Aurel Perianu, Dan Glavan, Gheorghe Sima
Abstract: The work includes work steps for joining thin sheets with a thickness ranging from1.0 mm (according to EN10327-2004). The study presents the following steps: problems arising from joining with CMT weld-brazing process of galvanized low-carbon steel sheets, used as filler material CuSi3. This is due to the fact that copper induces: grain refinement by lowering the transformation temperature and precipitation hardening after rapid cooling and tempering the theoretical and experimental study of these problems leads to the possibility of combining copper with iron. This is an experiment to investigate the formation of interlayer containing intermetallic compounds, inter layer located between the molten material and the base material. An important part of the study was the optimizing of weld-brazing parameters: welding current, welding speed and dynamic correction factor Ina.Keywords: galvanized sheets steel, joining, weld-brazing CMT, preserving the zinc layer, intermetallic layer.
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