Faruk Varol

The Effect Of Nugget Sizes On Mechanical Properties In Resistance Spot Welding Of SPA-C Atmospheric Corrosion Resistant Steel Sheets Used In Rail Vehicles*

Abstract This publication presents an experimental study on the resistance spot welding of SPA-C steel sheets used in side wall and roof application of rail vehicles. SPA-C atmospheric corrosion resistant steel sheets with a thickness of 2.3 mm were joined by using resistance spot welding as lap joint. A timer and current controlled resistance spot welding machine with 120 kVA capacity and a pneumatic application mechanism with a single lever were used to join the specimens. Welding periods were chosen as 5, 10, 15, 20, 25 and 30 cycles (1 cycle = 0.02 s) and also welding currents were increased from 6 kA up to 14 kA by rising in steps of 0.5 kA. The electrode force was kept constant at 6 kN. The welding joints obtained were exposed to tensile peel and tensile shear tests and their nugget sizes were calculated by results of optical microscopy measurements. The effect of nugget sizes on tensile peel strength and tensile shear strength was researched by using related diagrams and the optimum welding currents and times were advised.

Production of functionally graded SiC/Al-Cu-Mg composite by centrifugal casting

Abstract This study is aimed at investigating the production and wear properties of a functionally graded (FG) silicon carbide (SiC)-reinforced composite material, which was produced by stir casting followed by centrifugal casting. SiC powder (5 wt.%) was added into liquid aluminum at 750°C via stir casting, at which temperature a centrifugal force was applied to the mixture to drive the SiC particles toward the outer region of the mold. The results showed that two distinct regions formed in the cast samples after the centrifugation process. The outer region showed approximately 25% SiC particles resulting in almost SiC particle-free area in the internal region of the FG SiC-reinforced composite material. The test results showed that higher hardness and higher wear resistance could be obtained at the SiC-rich periphery of the cast FG composite material.

Investigation of carbon–carbon composite brake pads in wet and dry sliding wear conditions

Purpose – The purpose of this study was to investigate wear behaviours of brake pads produced from carbon–carbon (C/C) composites in both wet and dry friction sliding conditions. Carbon is probably the most remarkable element in science and also C/C composites are a family of advanced composite materials. They are the most advanced form of carbon and consist of fibre based on carbon precursors embedded in a carbon matrix. In the present work, wear test specimens were prepared according to the related standards and they were exposed to pin-on-disc wear testing in wet and dry sliding conditions with different loads as 10, 20, 30 and 40 N with 1 m/s constant sliding speed. Wet friction process was conducted on all specimens by means of rain water collected from the nature. Design/methodology/approach – Pin-on-disc wear test tribology lubrication was used. Findings – Mechanical and physical property measurements of C/C composite brake pad materials: hardness, modulus of elasticity, density and water absorptio...

Investigation of Mechanical Properties of MIG Brazed DP 600 Steel Joints Using Different Working Angles

Abstract In this study, dual phase (DP 600) steel plates with a thickness of 1 mm were joined by copper-based (CuAl8) wire using gas metal arc brazing technique. Specimens were prepared in butt joint form. Brazing operations were done at four different working angles: 50°, 60°, 70°, 80° and 90°, respectively. CuAl8 wire consisted largely of copper served as the filler metal. After completing the brazing operations, the tensile properties as well as the micro- and macro-structures of the joints were analyzed in order to investigate the joinability of DP 600 steel using gas metal arc brazing technique.

SAC METAL ŞEKİLLENDİRMEDE MUKAVEMET ARTTIRMA VE SONLU ELEMANLAR ANALİZLERİNİN DİNAMİK TESTLER İLE KARŞILAŞTIRILMASI

Bu calismada, beyaz esya sanayide yatay eksendeki kapaklarin acilip kapanmasini ve istenen seviyelerde dengede durmalarini saglayan yayli bir mentese mekanizmasi ele alinmistir. Mentesenin montajlanacak oldugu urunun geometrik sinirlari, calisma sartlari ve calisma araliklari tanimlidir. Menteseyi olusturan her bir parca icin detayli cizimler “SolidWorks” yazilimi yardimi ile yapilmis, 3d model olusturulmustur. Calisma esnasinda mentese mekanizmasi acma kapama omur test cihazi ile test edilmis ve deformasyona ugrayan parcalar belirlenmistir. Deformasyona ugrayan parcalarin sonlu elemanlar analizleri “SolidWorks Simulation” ile yapilmis, test sonuclarinin analiz verileri ortustugu gozlenmistir. Deformasyona ugrayan parca uzerinde geometrik iyilestirme yapilarak sonlu elemanlar analizleri ile yapilan iyilestirmenin sayisal karsiligi degerlendirilmis, alinan sonuclar laboratuvar testleri ile karsilastirmali olarak incelenmistir.

Microstructural Investigation of IF Steels Joined by Metal Inert Gas Brazing

In this study, interstitial-free (IF) Erdemir 7116 and galvanized Erdemir 1315 steels having 1.0 mm thickness were joined by metal inert gas (MIG)-brazing method. CuAl8 wire was used as filler material. The specimens were cut in 200 mm × 200 mm dimensions and joined by using 40, 45, 50, 55, 60, 65 and 70 A currents both in butt and overlap joint forms. Having prepared the joints, all specimens were exposed to tensile test according to TS 138 EN 10002-1 standard. Micro and macro-structure investigation of samples were performed by optical microscope and scanning electron microscope (SEM). The matrix structure and the other phases occurred during brazing process were characterized and the effects of them on mechanical properties of joints were discussed.

Microstructural Investigation of MIG-Brazed 304L Stainless Steel Joints

In this paper, austenitic 304L stainless steel plates having 1.0 mm thickness were joined by copper-based CuAl8 wire in gas metal arc brazing technique with 100 % Ar gas as a protective atmosphere. Specimens were prepared in butt and overlap joint positions. The metal inert gas (MIG) brazing operations were done with seven different arc voltages and weld currents as 40, 45, 50, 55, 60, 65 and 70 A. CuAl8 wire composed largely of copper serves as the filler metal was used. Owing to the low fusion temperature of the filler metal (900\(-\)1,100 \(^{\circ }\mathrm{C})\), no fusion of the base metal takes place in MIG-brazing. The 1,500 \(^{\circ }\mathrm{C}\) fusion temperature of the base metal was not reached. A solid joint between the workpieces was brought about by diffusion. Having accomplished the brazing operations, micro and macro-structures of joints were investigated by optical microscope and scanning electron microscope (SEM) in order to see the joinability of stainless steels by gas metal arc brazing technique.