Ugur Ozsarac

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...

Wear behaviour investigation of wheel/rail interface in water lubrication and dry friction

Purpose – The aim of this study is to calculate the coefficient of friction of wheel/rail interface in both water lubrication and dry friction conditions.Design/methodology/approach – Specimens taken from wheel and rail used in railway transport were exposed to pin‐on‐disc wear testing with 10, 20, 30 and 40 N loads. The disc took the place of the rail and the pin that of the wheel in wear tests, and rain water was fed to the disc/pin interface with a three drops/min speed in wet friction conditions. The coefficient of friction and weight loss values of specimens were determined and types of wear mechanism were characterized.Findings – It was observed that the friction coefficient decreased in wet sliding experiments, so smaller values were calculated in wet friction conditions than those of dry friction conditions for wheel specimens. However, this decrease was more drastic for rail specimens. Weight and volumetric loss values of rail materials were lower than those of wheel samples.Originality/value – T...

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.

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.