1,721,060 research outputs found
Improving of mechanical properties of GX8CrNi25-21 grade austenitic stainless steel
No full textFen Bilimleri Enstitüsü, Makine Mühendisliği Ana Bilim Dalı, Makine Mühendisliği Bilim DalıBu çalışmada, döküm yöntemi ile GX8CrNi25-21 malzemesi üretilmiştir. Malzeme dört farklı sıcaklık ve altı farklı soğutma şiddetine maruz bırakılarak ısıl işleme tabi tutulmuştur. Isıl işlemin birincil ve ikincil karbür içeriği, karbür dağılımı, karbür biçimi üzerindeki etkileri araştırılmıştır. Aşıma deneyleri neticesinde malzemenin termal şoklara karşı davranışı ve aşınma direnci belirlenmiş ve en uygun ısıl işlem şartları belirlenmeye çalışılmıştır. Malzemeye uygulanan homojenleştirme ısıl işlemi sonrası soğutma şiddetinin artırılmasının sertliği azalttığı saptanmıştır. Sertlik artışının sebebinin yapıda martenzitik dönüşümden kaynaklanmadığı, yapıdaki ikincil karbür içeriği ile ilgili olduğu belirlenmiştir. Homojenleştirme ısıl işleminden sonra yapıda karbür yapısı ve dağılımı farklılık göstermiştir. Primer karbürlerin boyutu azalmış ve dağılımları homojenlik kazanmıştır. Matriste daha küçük ve eş eksenli tane içine dağılmış sekonder karbürler meydana gelmiştir. Karbürün sertlik ve hacim oranının aşınma oranını belirlediği saptanmıştır.In this study, GX8CrNi25-21 material was produced by casting. The material was subjected to heat treatment by being exposed to four different temperatures and six different cooling intensities. The effects of heat treatment on primary and secondary carbide concentration, carbide distribution, and carbide type were investigated. As a result of abrasion tests, the behavior of the material against thermal shocks and wear resistance were determined and the most suitable heat treatment conditions were tried to be determined. It was determined that increasing the cooling intensity after the homogenization heat treatment applied to the material decreased the hardness. It was determined that the reason for the increase in hardness was not due to the martensitic transformation in the structure, but was related to the secondary carbide content in the structure. After the homogenization heat treatment, the carbide structure and distribution in the structure differed. The size of the primary carbides decreased and their distribution became homogeneous. Secondary carbides dispersed into smaller and equiaxed grains were formed in the matrix. It was determined that the hardness and volume ratio of carbide determined the wear rate
Evaluation of the metallurgical and mechanical properties of friction-welded joints of dissimilar metal combinations AISI2205/Cu
No full textIn this study, the joining performances of AISI2205/Cu friction-welded joints were studied using different friction pressures (35, 50, and 65 MPa) and friction times (6, 9, and 12 s). The microstructural properties of welded samples were examined by scanning electron microscopy. In order to determine the phases that occurred during welding, welded samples were examined with energy dispersive spectrometry and X-ray diffraction analysis. The microhardness across the interface of samples was measured, and also the strength of the joints was determined with tensile tests. The experimental results indicate that the tensile strength of friction-welded AISI2205/Cu components were significantly affected by joining friction pressure and friction time selected
Plasma arc welding of hood sheet used in automotive industry
No full textURL: http://sutod.selcuk.edu.tr/sutod/article/view/124Bu çalışmada, yüksek dayanımlı, düşük alaşımlı (YDDA) galvanizli sac malzemeler, plazma ark kaynak (PTA) yöntemiyle birleştirilmiştir. Çalışmada, sabit ilerleme hızı, plazma ve koruyucu gaz debisi şartlarında, akım şiddetinin bağlantıların kaynak nüfuziyeti üzerindeki etkisi deneysel olarak araştırılmıştır. Birleştirilmiş numunelerin ara yüzeylerinde meydana gelen yapısal değişimler, optik mikroskop ile incelenmiş ve mikrosertlik değerleri ölçülmüştür. Sonuç olarak, PTA yöntemi ile tam nüfuziyet elde edilmiş ve akım şiddetinin mikrosertlik değerlerini artırdığı tespit edilmiştir. Anahtar KelimelerIn this study, galvanized high strength and low alloy (HSLA) sheets were welded using plasma arc welding (PTA) technique. In the study, the travelling speed, flow rates of plasma and shielding gases were fixed, while the current density was chosen as alternative. The effect of current density on the welding penetration was experimentally investigated. Following the tests, the microstructural changes of interface of samples were studied by using optical microscope and microhardness tests were carried out at these regions. Finally, the full penetration was revealed by PTA and an increase in current density was lead to harder interface
The role of TiB2, Fe2B reinforcements on the wear rate of the coated AISI 430 stainless steel surface by PTA
No full textIn-situ synthesized TiB2, Fe2B reinforced coating was fabricated on AISI 430 steel substrate by using plasma transfer arc (PTA) and FeB, FeTi, FeW powders. The effects of powder type and powder ratio on the wear rate of coating were investigated experimentally. SEM, EDS and XRD analyses were used to differentiate the effect of coating parameters on the microstructure, which characterize the coated surfaces. Primary ferrite (alpha) phase and complex TiB2, Fe2B borides were detected on the subsurface microstructure. Abrasive wear tests were performed on the coated surface of specimens to examine the influence of the size-vol.% of borides and microstructural changes on the wear rate. Depending on the results, it is seen that the specimens coated by (FeB-FeTi-FeW) ferro-alloy powders mixture have the lowest wear rate
Effect of Alloy Content in Hardox450+FeW Composites Alloyed by PTAW on Wear Characteristic
No full textIn this study, Hardox450 + FeW alloys were coated on AISI1020 substrate material by using plasma transferred arc welding (PTAW) technique. The ratios of the coating materials were chosen as 5, 10, 15, 20 and 25 wt % FeW. The coating process was carried out as the current density (130 A), shielding gas (pure argon), shielding gas flow rate (25 L min(-1)), plasma gas flow rate (0.8 l min(-1)), welding speed (0.01 m min(-1)) and electrode diameter (3.2 mm). The coated alloys were characterized by optical microscope (OM), Scanning electron microscope (SEM), Elemental mapping, Energy dispersive spectrometer (EDS) and X-Ray diffractometer (XRD). Moreover, microhardness and wear tests were applied to determine the mechanical behavior. After wear test, wear rates were calculated by the mass losses of the specimens. The morphologies of worn surfaces were evaluated by SEM. Hardox450 + 25 wt % FeW showed the most combination in terms of wear performance with lower wear values under high-stress wear
OTOMOTİV ENDÜSTRİSİNDE KULLANILAN KAPORTA SACININ PLAZMA ARK KAYNAĞI
Get PDFBu çalışmada, yüksek dayanımlı, düşük alaşımlı (YDDA) galvanizli sac malzemeler, plazma ark kaynak (PTA) yöntemiyle birleştirilmiştir. Çalışmada, sabit ilerleme hızı, plazma ve koruyucu gaz debisi şartlarında, akım şiddetinin bağlantıların kaynak nüfuziyeti üzerindeki etkisi deneysel olarak araştırılmıştır. Birleştirilmiş numunelerin ara yüzeylerinde meydana gelen yapısal değişimler, optik mikroskop ile incelenmiş ve mikrosertlik değerleri ölçülmüştür. Sonuç olarak, PTA yöntemi ile tam nüfuziyet elde edilmiş ve akım şiddetinin mikrosertlik değerlerini artırdığı tespit edilmiştir
An Analysis Experimental for Archieving High-Quality Keyhole Shape in The Plasma Transferred Arc Welding of AISI 304/AISI 1030 Steel
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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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