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Öğe Effects of compaction pressure on microstructure, mechanical properties, and machining characteristics of sintered AISI 316L steel(Walter De Gruyter Gmbh, 2024) Erden, Mehmet Akif; Koklu, Ugur; Guldibi, Ahmet Serdar; Elitas, MuhammedIn this study, the effect of compaction pressure on the properties of AISI 316L and its machining performance was evaluated. AISI 316L powders were subjected to three different compaction pressures (550, 650, and 750 MPa). Subsequently, the samples were sintered in an argon atmosphere at a constant temperature of 1523.15 K. The microstructure, hardness, and mechanical properties of the materials were investigated. To examine the effect of compaction pressure on drilling characteristics (thrust force, torque, surface roughness, chip formation, and burr formation), the samples were subjected to dry drilling at different feed rates and cutting speeds. It was observed that increasing the compaction pressure resulted in smaller grain sizes in the microstructure, increased hardness, and higher tensile strength. Higher compaction pressure led to higher thrust force and torque, whereas lower compaction pressure resulted in improved hole surface quality and shorter chips. Additionally, at higher cutting speeds, the color of the chips changed due to the elevated temperatures associated with increased cutting speeds.Öğe The Effects of the Welding Parameters on Tensile Properties of RSW Junctions of DP1000 Sheet Steel(Eos Assoc, 2018) Elitas, Muhammed; Demir, BilgeIn this study, the maximum tensile shear load bearing capacity of the resistance spot welded DP1000 steel was measured and the tensile shear properties of the joints were evaluated. The effects of different welding parameters on microstructure, microhardness and tensile shear properties were investigated. Weld processes were performed by using 5kA and 7kA weld currents and 2-6bar electrode pressures. The microstructure of the welded materials was evaluated and the hardness profiles were determined. Experimental results showed that increasing electrode pressure and weld current increased the tensile shear load bearing capacity. It was also observed that the expulsion had a negative effect on the tensile shear load bearing capacity.Öğe Evaluation of the effect of MWCNT amount and dispersion on bending fatigue properties of non-crimp CFRP composites(Elsevier - Division Reed Elsevier India Pvt Ltd, 2022) Pekturk, Hatice Yakut; Elitas, Muhammed; Goktas, Mustafa; Demir, Bilge; Birhanu, SalihMulti-walled carbon nanotubes (MWCNTs) have many unique features that improve composite material properties, including a large surface area, thermal and chemical stability, and thermal and electrical conductivity. Our study aimed to examine the influence of MWCNT weight percentage on the fatigue characteristics of a polymer matrix composite strengthened with carbon fiber in fabric form. This study aimed to explore the additional properties and functions of these MWCNTs. For the experiments, MWCNTs were prepared by mixing them in solution with epoxy in three different weight percentages (0.5 %, 1.0%, and 1.5%) using a surfactant, and at 0.5 wt% without a surfactant. The prepared solutions were injected into four-axis non-crimp carbon fiber fabric plates via the vacuity mixture method and then cured for 48 h to produce nanocomposite plates. Using five types of composites, fatigue tests were carried out at six different amplitudes and a fixed frequency. Fatigue test specimens were subjected to detailed SEM analysis of their fatigue fracture surfaces. The investigational results revealed that the 0.5 wt% MWCNT epoxy solution had been homogeneously dispersed and exhibited the highest absorbance spectrum. The 0.5 wt% MWCNT specimen achieved the highest value in the fatigue life experiments. In addition, electron microscopy studies of the fracture surfaces of the test specimens determined that individual COOH-MWCNTs interrelated with the fibers and formed a bridge between fiber and matrix, whereas agglomerations caused weak bonding between the reinforcement fibers and matrix, making the material more brittle.(c) 2021 Karabuk University. Publishing services by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Öğe Finite element modelling of the fatigue damage in an explosive welded Al-dual-phase steel(Walter De Gruyter Gmbh, 2023) Elitas, Muhammed; Goktas, Mustafa; Acarer, Mustafa; Demir, BilgeIn this study, production of dual phase steel-Al 1100 aluminium alloy laminated composite by explosive welding and investigation the microstructural and mechanical properties especially fatigue life of the composite and its components were aimed. Finite element analysis (FEA) was used to simulate the bending fatigue tests of the Al 1100-DP steel (LITEC 1050) bimetal. A semi-wave at the explosive interface with intermetallic was obtained as a microstructural result. Hardness was increased near the interface due to deformation and intermetallic formation at the explosive weld interface. The impact test results showed that the samples' impact toughness was enriched by fabricating steel-Al laminated composite. The results also showed that the Al 1100-DP steel (LITEC 1050) bimetal composite properties were appropriate to the composite theory and satisfied strength-ductility relations accomplished. Additionally, the bending fatigue test and FEA results were compatible. Moreover, fatigue cracks were observed at the explosive weld interface between Litec DP steel and intermetallic but not at the Al-intermetallic interface.Öğe Investigation of the effect of different welding parameters on tensile properties and failure modes of non-alloyed steel produced by powder metallurgy(Sage Publications Ltd, 2023) Elitas, Muhammed; Erden, Mehmet AkifResistance spot welding was implemented to unalloyed steel produced by powder metallurgy method at different welding parameters in this study. Other welding parameters are constant, but electrode force values are 0.21-0.28-0.35 kN and welding current values are 9-10-11 kA. The effects of different welding parameters on microhardness, nugget diameter, tensile shear force, and failure mode were investigated. Consequently, the tensile shear force increased as welding current and electrode force up to a certain value increased. When critical electrode force value was exceeded, tensile shear force decreased, although nugget diameter increased. Compared to the base material, a decrease in tensile shear force has occurred in resistance spot welded joints. Except for values higher than the critical electrode force value, a linear relationship was determined between the nugget diameter, tensile shear force, and microhardness. Two different failure modes were observed, namely sheet transverse failure and partial interfacial failure.Öğe Investigation of the tensile shear property of DP600 steel combined with resistance spot welding(Pamukkale Univ, 2022) Demir, Bilge; Elitas, Muhammed; Karakus, HuseyinThis study focused on optimization of different electrode tip types (Conical round, Flat R3, Flat R6, Flat conical) and welding current parameters to obtain the ideal tensile shear strength of resistance spot welded DP600 steel. Welding processes were carried out at 5 and 7 kA welding currents for each of the 4 different tip types. Experimental results showed that welding current is the most important variable affecting tensile shear strength. As the welding current increased, the tensile shear strength increased. It has been determined that there is a linear relationship between the nugget diameter value and the tensile shear strength. The highest tensile shear strength values were obtained with flat 3 mm radius electrode tips and the lowest with conical round tip electrodes.Öğe An investigation on bending fatigue in a corrosive environment of dual-phase 1000 sheet steel RSW joints and damage model via experiment and numeric analysis(Sage Publications Ltd, 2024) Goktas, Mustafa; Demir, Bilge; Elitas, MuhammedFatigue, corrosion, and fatigue damage models are best addressed to improve and understand the service performance of materials, particularly automotive steel. This study is an attempt to experimentally and finite element investigates plain bending fatigue performance and damage model of DP 1000 sheet steel resistance spot welding (RSW) joints in 3% NaCl aqueous corrosive treatment. RSW applications were carried out using different weld currents. The joint samples were then subjected to optical image analysis, tensile shear, and fatigue tests (3% NaCl-aqueous and normal atmosphere). A proper damage model of RSW junctions was developed and corrected by numeric analysis. Besides, RSW nugget formation, tensile shear, and plain bending fatigue tests were also applied. Consequence, fatigue behavior, tensile load carrying capacity, and effective fracture behavior of resistance spot welded joint specimens were evaluated. Results showed that a corrosive environment negatively affected fatigue performance. With the developed model, it was observed that the fatigue life of the samples decreased by 30-35% in the fatigue tests performed in the corrosive environment. Experimental and numerical analysis results of plain bending were compatible.Öğe An Optimization Study on Resistance Spot Welding of DP600 Sheet Steel via Experiment and Statistical Analysis(Eos Assoc, 2023) Alzahougi, Abdulkarim; Demir, Bilge; Elitas, MuhammedResistance Spot Welding (RSW) is widely used in many automotive, boiler, and ship manufacturing industries. Therefore, the optimization and effectiveness of the RSW process are very useful and cost-efficient processes in addition to improving weld quality. This study used various welding parameters to investigate the optimization of the RSW process of Advanced High Strength Steel (AHSS). RSW was carried out using different welding times, currents, and electrode pressure values. Microstructural analysis, nugget formation, and tensile shear test were performed on samples. This study applied the Taguchi method and ANOVA to set up the welding process and optimize its results. Microstructural characterization showed that the weld nugget microstructures had a high-volume fraction of martensite. Using the Minitab software, Taguchi (DOE) and ANOVA on the tensile shear test results showed that welding current is more effective than clamping pressure on the tensile shear load-bearing capacity (TLBC). However, clamping pressure affects the weld current effects on weld performance. Additionally, the TLBC of RSW samples increases, whereas increasing the clamping pressure leads to a decrease in TLBC and nugget dimensions. Consequently, a detailed analysis of the RSW coefficients and their effects led to optimized results.Öğe Residual stress evaluation during RSW of DP600 sheet steel(Carl Hanser Verlag, 2020) Elitas, Muhammed; Demir, BilgeIn this study, resistance spot welding (RSW) process has been used on DP600 automotive steel at pressures of 2, 3, 4, 5 and 6 bar at a welding current of 7 kA. Microstructure, hardness and residual stress were examined to evaluate the effect of the welding pressure. An experiment at 5 kA and 6 bar was also conducted to investigate the effect of welding current on this behavior of steel sheet. The results show that microhardness values were higher in the welding region than in any other parts. There was no considerable change in the hardness behavior versus the welding pressure applied except for the sample welded at 7 kA and 4 bar. When the welding current changed from 7 to 5 kA, hardness improved. Residual stress evaluation reveals that compression stress was found in the specimens, and the specimen welded at 5 kA and 6 bar exhibited the highest residual stress.Öğe RSW Junctions of Advanced Automotive Sheet Steel by Using Different Electrode Pressures(Eos Assoc, 2018) Alzahougi, Abdulkarim; Elitas, Muhammed; Demir, BilgeThe effects of different types of welding current and electrode pressure on tensile shear properties of resistance spot welding (RSW) of commercial DP600 steel have been investigated in this study. In tensile shear tests of the welded joints, tensile shear force and maximum displacement were utilized to characterize the performance of the welding process. Nugget diameter has been measured to create a clear definition of RSW physical properties. Experimental results show that tensile shear load bearing capacity increases as the electrode pressure increases. Low current value occurs at low and at high electrode pressures. During high current value, the material can exhibit superior mechanical properties. The effect of electrode pressure on tensile shear load bearing capacity increases as welding current increases.
