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Öğe ANN prediction of impact toughness of ship steel/ stainless steel plates produced by explosive welding(University of Kuwait, 2020) Kaya, Y.; Kalyon, A.; Kahraman, N.In this study, ship steel/stainless steel plates were produced by joining ship steel with stainless steel using explosive welding process. The characterization of the joining interface of the plates was carried out by optical microscopic examination. Charpy impact tests were conducted at different temperatures to determine the impact toughness of the ship steel/stainless steel plates and the effect of the rolling on the impact toughness. In addition, after the Charpy impact test, the fractured surfaces of the specimens were investigated via scanning electron microscopy (SEM). Using the data obtained as a result of the impact toughness tests, an artificial neural network (ANN) model was improved for the prediction of the impact toughness. Five different material types, two different rolling directions, and eight different temperatures were used as the input parameters of the Charpy impact tests. The impact toughness values obtained at the end of the tests were used as the output parameters of the generated prediction model. The high R2 value obtained in the developed prediction model demonstrated that it could be successfully used for predicting impact toughness. © 2020 University of Kuwait. All rights reserved.Öğe Bending fatigue properties of structural steel fabricated through wire arc additive manufacturing (WAAM)(Elsevier B.V., 2022) Ayan, Y.; Kahraman, N.Wire arc additive manufacturing (WAAM) has become an essential production method with advantages such as ease of application and economic benefits, along with high material savings and its ability to produce large parts close to their final form in a short time. In recent years, many studies have been carried out on WAAM, most of which have investigated the properties of the manufactured parts. Among these properties, the topic of fatigue was less frequently examined. The reasons for this may include difficulties such as the long duration of fatigue tests and the large number of test specimens required. However, since fatigue is responsible for most of the damage in metal components, it is important to determine the fatigue strength of the parts produced using WAAM. In this study, the WAAM process was applied to low alloy ER70S-6 steel, which is widely used in the metal industry and is also one of the most common materials used in WAAM processes. After the fabrication, horizontal and vertical specimens were obtained from the manufactured part and mechanical and metallurgical tests were applied, including, fatigue tests, with the fatigue properties of the produced WAAMed part determined using a specially designed and produced bending stress fatigue testing machine. Results demonstrated that the fatigue limits of the horizontal and vertical fatigue specimens at 107 cycles were very close to each other, as approximately 180 MPa. The fatigue strength values of the vertical and horizontal specimens were quite similar. However, the fatigue strength of the vertical specimens up to 106 cycles was found to be slightly higher. © 2022 Karabuk UniversityÖğe The Design of Fatigue Test Machine and the Analysis of Fatigue Behavior of FSWed Dissimilar Aluminum Alloys(Springer, 2023) Yuruk, A.; Cevik, B.; Kahraman, N.Aluminum alloys have low density and high yield strength, thus leading them to be commonly used in aircrafts, sea vessels and land vehicles to acquire light weight and their use in these industries has been increasing every passing day. It is necessary to assemble many dissimilar aluminum alloys in such a way that they fit one another in the application. However, the parts made of these alloys are exposed to very different stresses (tensile, bending, impact, etc.) and fatigue occurs in the parts working especially under dynamic loads by causing structural damage. In this study, a computer-based fatigue test machine was designed and manufactured in order to do the fatigue tests for plate-type materials. This machine was used for the fatigue tests of dissimilar aluminum alloys (AA5754/AA6013) welded by the friction stir welding (FSW). FSW was carried out at 12.5, 25, and 32 mm/min welding feed rates and 1250 rpm. In addition, metallographic examinations and hardness tests were carried out to determine macrostructural and microstructural properties of weld zones and the effects of the joints on fatigue strength. The findings of the tests were evaluated and interpreted. The new machine successfully tested the fatigue of the FSWed samples. It was determined that in FSW, welding feed rate and material type were effective on the heat input, microstructure, hardness distribution of the weld zone and fatigue strength and life of the joints.Öğe Destructive and non-destructive inspection of pipes welded by MIG-MAG technique(2006) Gülenç, B.; Candan, I.; Kahraman, N.In this study, spiral welded steel pipes made of X52 material were butt joined at different positions using full automatic gas metal arc welding (MAG). In order to examine the influence of the torch position on the weldment, the specimens were subjected to destructive (tensile, impact toughness and hardness) and nondestructive (floroskop) testing. Test results showed that position of the torch during welding changed tensile strength and impact toughness. The non-destructive test showed that position of the torch effected weld bead form. Inadequate fusion melting was observed at some positions and at some others positions poor weld root bead was formed.Öğe Effect of Continuous and Pulsed Currents on Microstructural Evolution of Stainless Steel Joined by TIG Welding(Carl Hanser Verlag, 2015) Durgutlu, A.; Findik, T.; Gulenc, B.; Cevik, B.; Kaya, Y.; Kahraman, N.In this study, AISI 316L series austenitic stainless steel sheets were joined by tungsten inert gas welding method in continuous and pulsed currents. Regarding microstructural investigation and hardness values of weld metal, samples were welded to investigate the effect of current type on grain structures of weld metal. Results showed that samples welded by using pulsed current had considerable different properties compared to the samples welded by using continuous current. While the weld metals of joinings obtained by using continuous current displayed a coarse-grained and columnar structure, weld metals obtained by using pulsed current had a finer-grained structure. It was also found that hardness values of samples, which were welded with continuous and pulsed current, were quite different.Öğe The Influence of Hydrogen Addition to Argon as a Shielding Gas on the Fatigue Performance of TIG Welded AISI 304 Stainless Steel(Natl Acad Sciences Ukraine, Inst Metal Physics, 2013) Gozutok, E.; Kahraman, N.[No abstract available]Öğe The influence of hydrogen addition to argon as a shielding gas on the fatigue performance of TIG welded AISI 304 stainless steel(2013) Gözütok, E.; Kahraman, N.In this study, AISI 304 austenitic stainless steel sheets are joined through TIG welding under various shielding media. Bending fatigue, notch impact and bending tests are performed on the joined materials. Hardness of the joined materials is also determined. The welding processes are carried using pure argon, argon + 1.5% H2 and argon + 5% H2 as shielding media at three different welding currents. Both butt and overlap welding processes are carried out at the same welding parameters. The ER 308 L type wire is used as the filler material for all the joints. The highest fatigue and impact strengths are obtained for both types of joints for argon shielding media. The bending test is applied up to 180°, and no tearing, crack or any other bending defects after visual examination of the bended samples are observed. The welding metal gives the highest hardness values, and they are followed by HAZ and base material.Öğe An investigation into the effect of welding current on the plasma arc welding of pure titanium(Redakcia Kovove Materialy, 2010) Kahraman, N.; Taskin, M.; Gulenc, B.; Durgutlu, A.In the present study, plasma arc welding method was applied to commercial purity titanium using various welding current values. In order to determine the strength of the resulting joints, tensile tests, impact tests and hardness tests were applied. Additionally, optical microscopy examinations were carried out to determine the interface properties of the joints. The work showed that the highest interface strength was obtained for the specimens joined at 65 A. For all the welding parameters, the hardness test results showed that weld metal gave a higher hardness value than heat affected zone and base metal. The microstructure in welded joint consisted of acicular alpha and twins.Öğe An investigation into the effect of welding current on the plasma arc welding of pure titanium(2010) Kahraman, N.; Taskin, M.; Gülenç, B.; Durgutlu, A.In the present study, plasma arc welding method was applied to commercial purity titanium using various welding current values. In order to determine the strength of the resulting joints, tensile tests, impact tests and hardness tests were applied. Additionally, optical microscopy examinations were carried out to determine the interface properties of the joints. The work showed that the highest interface strength was obtained for the specimens joined at 65 A. For all the welding parameters, the hardness test results showed that weld metal gave a higher hardness value than heat affected zone and base metal. The microstructure in welded joint consisted of acicular alpha and twins.Öğe An investigation into the joining of titanium with copper through diffusion welding/bonding(2013) Aydin, K.; Hidiroglu, M.; Kaya, Y.; Kahraman, N.In this study, Ti-6Al-4V and copper were joined through different welding temperatures (825 and 850 °C) and holding time (15, 30 and 60 min) diffusion welding/bonding method under argon shielding. The welded joints were subjected to hardness and shearing tests in order to determine their interfacial strength. In addition, microstructural properties of the joined interface were examined using optical and scanning electron microscope (SEM). EDS graphs and diffusion maps of the interface were obtained by carrying out line and elemental analyses. The shearing tests revealed that increasing welding temperature and holding time increased the shearing strength of joined parts. The hardness tests indicated that hardness values increased with increasing distance from titanium to the interface and decreased with increasing distance from the interface to the copper. EDS analyses showed that different reaction areas took place in the welded parts depending on the temperature and holding time.Öğe Investigation of mechanical and microstructural properties of AA5754/AA6013 dissimilar aluminium alloys joined by GMAW and FSW methods(Redakcia Kovove Materialy, 2021) Yuruk, A.; Ayan, Y.; Cevik, B.; Kahraman, N.Aluminium alloys AA5XXX and AA6XXX have low density and high yield strength and are frequently used to make air, sea, and land vehicles/technology lighter. Different types of aluminium alloys need to be adaptively assembled together. Therefore, it is important but difficult to weld aluminium alloys. This study investigated the microstructural and mechanical properties of two dissimilar aluminium alloys, AA5754 and AA6013, which were welded using gas metal arc welding (GMAW) and friction stir welding (FSW). Hardness, tensile, bending, and fatigue tests were done on the welded samples. The test results were evaluated and interpreted according to the literature. The weld zone (weld metal, HAZ) of AA5754 and AA6013 aluminium alloys joined by GMAW and FSW showed significant differences. The highest tensile strength and fatigue life were obtained from the FSWed sample after the base metals. The welded samples joined using both welding methods were successfully deformed by 180 degrees without damaging their upper or lower surfaces.Öğe Investigation of mechanical and microstructural properties of aa5754/aa6013 dissimilar aluminium alloys joined by gmaw and fsw methods(Institute of Materials and Machine Mechanics, Slovak Academy of Sciences, 2021) Yuruk, A.; Ayan, Y.; Cevik, B.; Kahraman, N.Aluminium alloys AA5XXX and AA6XXX have low density and high yield strength and are frequently used to make air, sea, and land vehicles/technology lighter. Different types of aluminium alloys need to be adaptively assembled together. Therefore, it is important but difficult to weld aluminium alloys. This study investigated the microstructural and mechanical properties of two dissimilar aluminium alloys, AA5754 and AA6013, which were welded using gas metal arc welding (GMAW) and friction stir welding (FSW). Hardness, tensile, bending, and fatigue tests were done on the welded samples. The test results were evaluated and interpreted according to the literature. The weld zone (weld metal, HAZ) of AA5754 and AA6013 aluminium alloys joined by GMAW and FSW showed significant differences. The highest tensile strength and fatigue life were obtained from the FSWed sample after the base metals. The welded samples joined using both welding methods were successfully deformed by 180° without damaging their upper or lower surfaces. © 2021 Institute of Materials and Machine Mechanics, Slovak Academy of Sciences. All rights reserved.Öğe Investigation on joint properties of AA5754 and AA6013 dissimilar aluminum alloys welded using automatic GMAW(Elsevier B.V., 2020) Mercan, E.; Ayan, Y.; Kahraman, N.Aluminum alloys AA5754 and AA6013 were joined using gas metal arc welding (GMAW) and the mechanical, microstructure and corrosion properties of the joints were investigated. The welding process was performed using argon as shielding gas with three different wire feed speeds and welding speeds. Metal wire (ER5356 filler) with a diameter of 1.2 mm was used in the welding process. In order to determine the mechanical properties of the joints, the welded specimens were subjected to tensile and hardness tests. In addition, an electrochemical corrosion test was conducted to determine the corrosion resistance of the specimens. The welding zone of the specimens was characterized via microstructure examination. In the tensile tests, fractures occurred in the weld metal and the heat affected zone (HAZ). However, tensile strength performance of the joints exceeded 90% under the appropriate welding parameters. The corrosion test results showed that the samples with joint defects (insufficient melting) were exposed to corrosion more rapidly than the others. Hardness test results revealed that maximum hardness values were measured at the HAZ of the AA6013 specimen, followed by the weld metal and HAZ of the AA5754 specimen, respectively. Microstructure inspections showed the structures of all the weld metals to be dendritic. © 2019 Karabuk UniversityÖğe Joining of copper and steel plates by shielded metal arc and tig welding methods and investigation of their interface properties(2005) Durgutlu, A.; Kahraman, N.; Gülenç, B.In this study, low carbon steel and copper plates were welded to each other by shielded metal arc and tungsten arc welding processes. Mechanical and microstructural properties of the joints were investigated. Tensile, bending and hardness tests of the welded specimens were conducted. Optical microscopy and SEM studies were carried out, in order to make the microstructural evaluation. During the tensile tests of the welded specimens, fracture occurred in the copper side apart from the weld region. Macro examination of the bended specimens showed no crack and tears. The results showed that hardnesses of the shielded metal arc welded specimens were higher than those of tungsten arc welded samples. However, hardness values of the weld metal were found to be lower than those of the low carbon steel but it was found to be higher than those of the copper side. From the results of metallographic examination, a uniform transition from parent metal to weld metal was observed in the weld region and more grain growth was observed in TIG welding specimens due to higher heat input when compared to the shielded metal arc welded samples.Öğe Mechanical properties and corrosion behavior of similar/dissimilar resistance spot welded automotive aluminum alloysMechanische Eigenschaften und Korrosionsverhalten von artgleichen/artungleichen widerstandspunktgeschweißten Aluminiumlegierungen für die Automobilindustrie(Wiley-V C H Verlag Gmbh, 2023) Kaya, I.; Baser, T. A.; Kahraman, N.Recently, usage of high strength aluminum alloys in automotive applications increase. The reasons for that increase are the light-weight, high strength, good formability, weldability and corrosion resistance of the aluminum alloys to improve fuel economy as well as decreasing carbon dioxide emission. Automotive hybrid structures are commonly manufactured using dissimilar AA5000-AA6000 joints to improve mechanical requirements and corrosion resistance of the parts. In this study, AA5754 H111-AA6063 T4 materials were joined both similarly and dissimilarly by resistance spot welding method. Within the study, a mid-frequency direct current technology was used instead of conventional alternative current technology. The welded zone was investigated by micro hardness measurements and microstructural characterization. Tensile-shear and cross-tension tests were performed. The welded zone of all welded specimens was subjected to salt spray corrosion test. A nugget pull-out fracture mode was observed on the fracture surface of the all welded joints after tensile-shear and cross-tension tests. The lowest hardness values were measured from the weld metals for all welded joints. Porosity and inclusion were observed in the weld nugget with minor cracks in heat affected zone by optical microscope investigations. In this work, AA5754 H111-AA6063 T4 materials were joined both similarly and dissimilarly by resistance spot welding method. A mid-frequency direct current technology was used instead of conventional alternative current (AC) technology. The welded zones were examined by micro hardness measurements, microstructural characterization, tensile-shear, cross-tension and salt spray corrosion tests.imageÖğe Metallurgical and corrosion properties of explosively welded Ti6Al4V/low carbon steel clad(2005) Kahraman, N.; Gülenc, B.Titanium alloy (Ti6Al4V) and low carbon steel (LCS) were joined by explosive welding method using different ratios of explosive. Some metallurgical properties of joined samples were investigated. Joined samples were examined by means of optical microscope, scanning electron microscope (SEM) and tensile-shearing tests. Bending, tensile, hardness and corrosion behaviour of the samples were investigated. Separation was not occurred on the joining interface after tensile-shearing and bending tests. It is seen that hardness of both plates were increased with increasing explosive. It is found that increasing explosive ratio leads to an increase in corrosion. It is also found that corrosion rate was high at the beginning of the experiment but the rate of the corrosion decreased subsequently during the experiment.Öğe MICROSTRUCTURE AND MECHANICAL PROPERTIES OF DISSIMILAR RESISTANCE SPOT WELDED ZN-COATED DP800-TBF1180 AUTOMOTIVE STEELS USING MFDC TECHNOLOGY(Polska Akad Nauk, Polish Acad Sciences, Inst Metall & Mater Sci Pas, 2024) Hidiroglu, M.; Baser, T. A.; Kahraman, N.The use of advanced high-strength steel in the automotive industry is increasing in last decade. This is due to the restrictions to reduce fuel consumption and thereby decrease harmful carbon dioxide emissions. This paper aims to investigate welding properties of dissimilar resistance spot welded hot dip galvanized DP800-TBF1180 automotive steels using MFDC (Mid Frequency Direct Current) technology. LME crack occurrence due to the zinc coating was determined by magnetic particle test. The mechanical properties of welded joints were determined by tensile-shear, cross-tension and hardness measurements. The micro structural characterization was also performed in the weld zones of the joints. The appropriate welding parameter range were selected for welding processes by MFDC technology. Therefore, LME crack formation were not observed according to magnetic particle test. The highest strength was obtained as 17.60 kN and 5.51 kN by tensile-shear and cross tension tests, respectively with a welding current of 8 kA. In addition, a soft zone was found in the HAZ for both base metals. The hardness decrease in HAZ is more pronounced on the TBF1180 side. The soft zone hardness values of the sample S4 were approximately 330 HV, and the hardness values of the base material were measured in the range of 376-386 HV.Öğe MIG welding of AISI 409 and Ç1010 steel using an austenitic electrode and investigation of their mechanical properties(2009) Kilinçer, S.; Kahraman, N.In this study, joinability of dissimilar metals by using gas metal arc welding was investigated. For this aim, a ferritic stainless steel (AISI 409) and a low carbon steel (Ç 1010) were joined at different welding parameters through automated robotic gas metal arc welding process using an austenitic filler metal. Mechanical and metallographic properties of the specimens were obtained by means of tensile test, bending test, microhardness test, impact test and optical microscopy examinations. In the tensile tests, fracture always occurred in the low carbon steel portion of the welded specimens away from the weld zone. Visual observation of the bended specimens showed no crack and tears. For all welding parameters, hardness test results showed that weld metal gave higher hardness value than HAZ and base metal. From the results of metallographic examination, it was seen that grain growth in the weld metal and HAZ increased with increasing heat input.Öğe A novel approach to diffusion bonding of copper to stainless steel(Sage Publications Ltd, 2012) Kaya, Y.; Kahraman, N.; Durgutlu, A.; Gulenc, B.In this study, austenitic stainless steel and copper materials were bonded through the diffusion welding method, one of the solid-state welding processes. The welding process was carried out at 875 degrees C temperature for 30 minutes under 3MPa pressure. Two different methods were employed in the welding process. In the first method, the conventional diffusion welding procedure was followed. In the second one, an external electrical current was applied to the parts to be joined with the help of a system that was added to the conventional system. By doing so, the aim was to determine the diffusion amount and length for the specimens obtained with and without current. The weld quality of the diffusion welded specimens was examined using the tensile and hardness test. In addition, microstructural analyses were done using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The highest hardness value was obtained in regions next to the interface and it was decreased gradually as the distance from the interface increased on both sides of the interface. The results indicated that the highest interface strength was obtained for the specimens joined when the external current was applied. According to the EDS and EDS line element analyses results, it can be seen that the specimens joined by applying the external current had a higher amount of diffusion and length than the specimens joined by the conventional technique.Öğe Production of wire reinforced composite materials through explosive welding(Elsevier Urban & Partner Sp Z O O, 2016) Gulenc, B.; Kaya, Y.; Durgutlu, A.; Gulenc, I. T.; Yildirim, M. S.; Kahraman, N.Explosive welding is a solid state welding process, which uses a controlled explosive detonation to force two metals together at high pressure. The process has been fully developed with large-scale applications in the manufacturing industry. The explosive bonding technique has an ability to bond a variety of similar and dissimilar materials, and has been applied to fabricate the clad materials and some composites such as multilayered and wire-reinforced materials. In this study, aluminum plates were explosively welded by placing a steel wire mesh between them in order to produce wire mesh reinforced composite materials. The steel wire meshes were placed at two different orientations (45 degrees and 90 degrees). The wire mesh was used to improve the mechanical properties of the explosively welded aluminum plates. Hardness, tensile strength, toughness, bending and microstructure of the explosively welded composite materials were evaluated. The tensile and toughness tests results showed that the 45 wire mesh reinforced composites exhibited higher strength than unreinforced explosively bonded Al plates. No separation was observed in the interface of the welded composite materials after three-point bending. The highest hardness value was measured for the area near the joining interface. (C) 2015 Politechnika Wroclawska. Published by Elsevier Sp. z o.o. All rights reserved.
