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Öğe A parametric study on weld zone shape of resistance spot welded 22MnB5 steel(Taylor & Francis Ltd, 2023) Tuncel, Oguz; Aydin, Hakan; Gonul, AlisanThe resistance spot welding of 22MnB5 with different weld currents, weld times, and quenching conditions is investigated in the current study. A Kriging Response Surface Methodology-based local sensitivity analysis is performed to investigate the effect of weld current, weld time, and quench condition on weld zone morphology and tensile shear load (TSL). When welding current, welding time, and quenching conditions are varied between the minimum and maximum values, the geometry of the weld zone was influenced by 40-60%, 20-40%, and 0-20%, respectively, according to sensitivity studies. It is also found that increasing values of welding current are the most effective welding parameter, increasing TSL by about 45%. In order to better understand the TSL variation at different welding parameters, various hardness measurements are applied for each specimen in the fusion zone and the heat-affected zone (HAZ) regions of the weld zone. Based on the location, the HAZ was divided into three regions: the inner, middle, and outer. The middle HAZ had hardness values 12% higher than the base material, while the outer HAZ had hardness values up to 36% lower than the base material. Also, macro-and microstructure images of the sample produced by combining the quenched and non-quenched materials are obtained to demonstrate how the hardness zones are identified.Öğe Effect of heat input on HAZ softening in fiber laser welding of 22MnB5 steel(Elsevier Sci Ltd, 2023) Tuncel, Oguz; Aydin, Hakan; Davut, KemalThis study investigates the effects of heat input on the heat-affected zone (HAZ) softening in fiber laser welding of quenched 1.1 mm thick 22MnB5 steel. Laser power (1500-2500 W) and welding speed (40-120 mm/s) parameters are considered as the input process variables. Depending on the input parameters, the applied heat input varied between 12.5 and 62.5 J/mm. The results indicate that a minimum heat input of 50 J/mm is required for full weld penetration. Microhardness findings revealed that the drop in hardness in the HAZ region relative to the base material (BM) reached 39% due to grain coarsening caused by an increase in heat input under the welding conditions. Grain coarsening (prior austenite grains) is also detected in SEM analysis. In addition, grain coarsening at high heat input was also determined quantitatively in EBSD analyses. The proportion of 8.91 mu m grain size in the sample with high heat input is 4.2%, while it is 1.2% in the sample with low heat input. When the heat input increased from 12.5 to 62.5 J/mm, the width of the softened zone with the lowest hardnesses in the HAZ grew from 0.2 mm to 2.2 mm.Öğe Effect of rotational speed and dwell time on mechanical properties of dissimilar AA1050-AA3105 friction stir spot welded joints(Carl Hanser Verlag, 2014) Aydin, Hakan; Tuncel, Oguz; Yuce, Celalettin; Tutar, Mumin; Yavuz, Nurettin; Bayram, AliFriction stir spot welding is a newly developed joining technology which is expected to be used in the automotive industry for joining body parts made of aluminum sheets. The effect of the rotational speed and dwell time on the mechanical properties of dissimilar friction stir spot welded aluminum sheet alloys was investigated in this study. In the experimental studies, macro-structural characterization, micro-hardness tests and tensile shear tests were conducted. The experimental results showed that the tensile shear load and tensile deformation of the friction stir spot welded joints decreased roughly by 20 % and 25 %, respectively, when the rotational speed increased from 1000 rpm to 2000 rpm. On the other hand, when the dwell time increased from 3 s to 11 s, the tensile shear load increased roughly by 7 %, while the tensile deformation decreased roughly by 19 %, respectively. © Carl Hanser Verlag GmbH & Co.Öğe Effect of tool pin profile on the hook geometry and mechanical properties of a friction stir spot welded AA6082-T6 aluminum alloy(Canadian Science Publishing, 2021) Aydin, Hakan; Tuncel, Oguz; Tutar, Mumin; Bayram, AliAA6082-T6 alloy was joined by friction stir spot welding using five different pin profiles, namely cylindrical, conical, triangular, hexagonal, and cylindrical with two grooves, at different dwell time. The joints welded by cylindrical pins had larger effective weld width. However, grooves on the cylindrical pin decreased the effective weld width. In the weld made with the hexagonal pin, the hook was bent downward from the interface of the sheets and had the smallest effective weld width. When the conical pin was used, the effective weld width increased with increasing dwell time. In the case of using tools with cylindrical and conical pins, HAZ hardness was relatively lower. With increasing dwell time, HAZ hardness of the joints made with the conical pin decreased. Effective weld width determined the weld strength under the tensile shear loading condition: larger effective weld width resulted in higher weld strength. Weld strength of the joints made with cylindrical pins was higher. The joints fabricated with hexagonal pins had the lowest weld strength. In general, higher dwell time led to higher weld strength. The welds with the higher strength experienced both brittle and ductile fractures, while the joints with the lower strength exhibited completely brittle fracture.Öğe Friction Stir Spot Weldability of AA7075-T6 Sheets with a Pinless Tool Providing Enhanced Stirring Effect(Springer, 2024) Cakan, Betul Gulcimen; Tuncel, Oguz; Tutar, MuminThe automotive and aerospace industries have explored alternative welding methods, such as friction stir welding (FSW) and its derivation, friction stir spot welding (FSSW). Welding parameters and tool shoulder designs influence material flow dynamics and stirring during the FSSW process. The current study uses a newly manufactured pinless tool to focus on the FSSW of 3-mm-thick AA7075-T6 aluminum sheets, which were joined using a pinless tool with a concave shape of three grooves for improved flow characteristics. The experiments explore the impact of welding parameters on the weld quality. Tensile tests, macroscopic examination, fracture surface analysis, and microhardness tests were performed. The geometric characteristics of hook shape and effective weld width substantially affected the tensile shear load (TSL). Tensile test findings and changes in effective weld width with welding parameters reveal that low rotational speed, high penetration depth, and dwell time parameters can result in a high TSL. Microhardness profiles reveal that the stir zone (SZ) exhibits the highest hardness values, reaching 27% above the base material hardness. The heat-affected zone (HAZ) shows the lowest hardness values. Fracture surface morphology analysis reveals different fracture modes in high and low TSL specimens.Öğe Investigation of the effects of welding parameters on mechanical properties and microstructure of triple joined FEP05/DP600/FEP05 steel sheets joined by electrical resistance spot welding(Gazi Univ, Fac Engineering Architecture, 2024) Selova, Levent; Tuncel, Oguz; Cavusoglu, Oktay; Dindar, Cigdem; Aydin, HakanNowadays, resistance spot welding of two or triple joints and of similar or dissimilar sheet metals is widely used in the automotive industry. In the a-, b-, and c-pillars of car bodies, dual-phase (DP) 600 steels and FEP05 steels are commonly welded together. This study investigated the impact of resistance spot welding process parameters such as welding current, welding time, and electrode force on the tensile shear load, elongation, nugget diameter, and indentation depth of triple welded sheet joints (FEP05 + DP600 + FEP05). To determine the mechanical properties of the welded joint, tensile tests and micro-hardness measurements were performed. Microstructural characterization was also used to analyze the weld quality. Additionally, it was demonstrated that welding time, welding current, and electrode force are important factors in triple welded joints. As a result, it has been seen that FEP05 + DP600 + FEP05 sheets can be successfully combined with triple electrical resistance spot welding by choosing the welding parameters appropriately. A shows the relationship of the welding current with the indentation depth and the nugget diameter.Öğe Multi-objective optimization of 3D printing process parameters using gray-based Taguchi for composite PLA parts(Wiley, 2024) Tuncel, Oguz; Tufekci, Kenan; Kahya, CaglarThis study investigates the additive manufacturing (AM) process of 30% ceramic-reinforced composite PLA material using the fused deposition modeling (FDM) technique. The effects of various printing parameters on tensile strength, build time, and material consumption are comprehensively analyzed through a combination of the Taguchi method, analysis of variance (ANOVA), and gray relational analysis (GRA). Experimental design parameters include nozzle diameter, infill density, infill pattern, wall line count, print speed, and layer height. Statistical analyses reveal significant contributions of these parameters to mechanical properties and production efficiency. Single and multi-objective optimizations of the responses were performed. The single optimization resulted in a significant increase in tensile strength from 39.9 to 48.10 MPa. Production time was reduced from 16 to 9 min; material consumption decreased from 4.95 to 2.43 g for tensile test specimens. The use of GRA in multi-objective optimization has led to a significant improvement of 8.31% in the gray relational grade (GRG) when compared to the initial parameter settings. These findings provide valuable insights for optimizing FDM processes in the fabrication of composite PLA materials. This contributes towards the advancement of additive manufacturing technology and its applications across various industries. and its applications across various industries.Öğe Optimization of Charpy Impact Strength of Tough PLA Samples Produced by 3D Printing Using the Taguchi Method(Mdpi, 2024) Tuncel, OguzThis research employs the Taguchi method and analysis of variance (ANOVA) to investigate, analyze, and optimize the impact strength of tough polylactic acid (PLA) material produced through fused deposition modeling (FDM). This study explores the effect of key printing parameters-specifically, infill density, raster angle, layer height, and print speed-on Charpy impact strength. Utilizing a Taguchi L16 orthogonal array experimental design, the parameters are varied within defined ranges. The results, analyzed through signal-to-noise (S/N) ratios and ANOVA, reveal that infill density has the most substantial impact on Charpy impact strength, followed by print speed, layer height, and raster angle. ANOVA identifies infill density and print speed as the most influential factors, contributing 38.93% and 36.51%, respectively. A regression model was formulated and this model predicted the impact strength with high accuracy (R2 = 98.16%). The optimized parameter set obtained through the Taguchi method, namely, a 100% infill density, 45/-45 degrees raster angle, 0.25 mm layer height, and 75 mm/s print speed, enhances the impact strength by 1.39% compared to the experimental design, resulting in an impact strength of 38.54 kJ/m2. Validation experiments confirmed the effectiveness of the optimized parameters.Öğe Optimization of Flexural Performance of PETG Samples Produced by Fused Filament Fabrication with Response Surface Method(Mdpi, 2024) Tuncel, Oguz; Kahya, Caglar; Tufekci, KenanAdditive manufacturing (AM), particularly fused filament fabrication (FFF), has gained significant attention for its design flexibility and cost-effectiveness. This study focuses on optimizing FFF parameters that employ response surface methodology (RSM) to enhance the flexural performance of polyethylene terephthalate glycol (PETG) parts. Three essential parameters-layer height, print speed, and nozzle temperature-were varied, and their effects on flexural strength, flexural modulus, flexural toughness for ultimate strength, flexural toughness at 5% strain, and strain at ultimate strength were evaluated. Based on a Box-Behnken design, the experiments revealed significant effects of these parameters on the mechanical responses. The analysis of variance (ANOVA) indicates that layer height predominantly affects flexural modulus and toughness, while nozzle temperature significantly impacts flexural strength. The RSM models exhibited high accuracy, with R2 values exceeding 99%. Optimal parameter combinations yield remarkable improvements: flexural strength reached 39.55 MPa, flexural modulus peaked at 1344.60 MPa, flexural toughness for ultimate strength reached 218.22 J/mm3, flexural toughness at 5% strain reached 381.47 J/mm3, and strain at ultimate strength reached 3.50%. Validation experiments confirm the effectiveness of the optimization, with errors below 3.17%.
