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Öğe AISI 4140 çeliğinde yorulma çatlağı ilerlemesinin sistemin doğal frekansına etkisi(Bolu Abant İzzet Baysal Üniversitesi, 2015) Bilge, Habibullah; Pakdil, MuratBu çalışmada, mühendislik uygulamalarında büyük bir öneme sahip olan kirişlerde yorulma çatlağı büyümesinin sistemin doğal frekansı üzerindeki etkisi çalışılmıştır. Çok geniş bir uygulama alanına sahip olan kirişler, mühendislik yapılarında sıklıkla temel yapı elemanı olarak kullanılmaktadırlar. Bu nedenle bu yapılarda oluşabilecek bir hasarın önceden tespit edilmesi, oluşabilecek yıkıcı hasarların önlenmesi açısından büyük önem arz etmektedir. Hasarların önceden tespit edilmesi konusunda da yaygın olarak kullanılan yöntemlerden biri, yapının titreşim analizidir. Dolayısıyla yapının doğal frekanslarındaki değişimlerin tespit edilmesi ve izlenmesi çok önemlidir. Bu noktadan hareketle çalışmada, 4140 çeliğinden üretilen kirişteki yorulma çatlağı büyümesinin kirişin doğal frekansı üzerindeki etkileri sayısal ve deneysel olarak incelenmiştir. 8x16x500 mm boyutlarındaki kirişe 3 mm uzunluğunda ve 0,25 mm genişliğinde tel erezyon ile bir çatlak açılmıştır. Daha sonra dinamik yorulma cihazında 10 Hz' de 3 nokta eğme testine tabi tutulmuş ve belirli aralıklarla kirişin doğal frekansları ölçülerek kirişin doğal frekanslarında meydana gelen değişiklikler ölçülmüştür. Bu veriler ile dinamik yüklemelere maruz kalan kirişte oluşan yorulma çatlağının, büyüme aşamasında tespit edilmesi ve boyutunun belirlenmesi gerçekleştirilmiştir. Bu yöntem ile deneysel veriler elde edilmiştir. Deneysel veriler, kirişteki yorulma çatlağı büyümesi ile kirişin doğal frekansının azaldığını göstermiştir.Öğe Analytical and experimental investigation of the rotary inertia effects of unequal end masses on transverse vibration of beams(MDPI, 2023) Bilge, Habibullah; Morgül, Ömer KadirIn this study, the transverse vibration of free-free slender beams with two unequal end masses attached were studied. The effects of the rotary inertia of the end masses on the free vibration of the beam were investigated. An exact frequency equation and the boundary conditions were obtained by using the Euler-Bernoulli beam theory and Hamilton's principle. Natural frequencies and mode shapes of the beams in transverse vibrations were calculated for various combinations of physical and geometrical parameters, such as mass ratios, the distances between the attachment point and the center of the masses, etc. The effects of an increase in the rotational inertia of the end masses and different mass ratios on the natural frequencies and mode shapes of the beam are presented. It is shown that the increase in the rotational inertia of the end masses had a greater effect at low frequencies of the beam. In addition, experimental tests were performed to validate the obtained analytical results. A good agreement was obtained between the analytical and experimental results. The main scope of this study was to reveal the effects of the rotary inertia of the end masses on the dynamic behavior of the beam. Thus, the aim is to contribute to the understanding of the properties of the end mass and the effect of rotary inertia on the dynamics of end-mass-attached structures. Furthermore, the results obtained from this research are helpful for designing end-mass-attached structures, such as micromechanical sensors, energy harvesters, and Stockbridge-type dynamic absorbers.Öğe Degeneration of mechanical characteristics and performances with Zr nanoparticles inserted in Bi-2223 superconducting matrix and increment in dislocation movement and cracks propagation(Springer, 2016) Akdemir, Ertuğrul; Pakdil, Murat; Bilge, Habibullah; Kahraman, Mehmet Fatih; Bekiroğlu, Erdal; Yıldırım, Gürcan; Öz, MuhammedThis study explains the role of Zr concentration level on mechanical characteristics and performance belonging to the bulk Bi-2223 superconducting materials by means of standard Vickers microhardness (H-v) measurements at different applied loads in the range of 0.245-2.940 N and evaluated theoretical calculations. The experimental measurement results obtained display that the mechanical performances regress with the increment of the Zr addition level due to the increased artificial disorders/damages/breaks/voids/cracks and irregular grain orientation distribution. In other words, the Zr addition accelerates both the dislocation movement and especially the cracks/voids propagation of as a consequence of the decrement in the Griffith critical crack length, being one of the most striking points deduced from this work. These vital findings are also favored by the extracted parameters of Young's modulus, yield strength, fracture toughness and brittleness index. Nevertheless, it is found that every sample studied exhibit typical indentation size effect (ISE) behavior due to the production of the elastic and plastic deformations simultaneously in the system. Moreover, the load dependent microhardness values are theoretically analyzed with the aid of six available models such as six available approaches: Meyer's law, proportional sample resistance model, modified proportional sample resistance model, elastic/plastic deformation, Hays-Kendall (HK) and indentation-induced cracking model for the first time. The results obtained show that the HK approach exhibits perfectly performance on the analysis of the mechanical characteristics of the superconducting materials exhibiting ISE behavior whereas the other models are inadequate to explain the load independent mechanical characteristics of the Bi-2223 system added by the Zr nanoparticles.Öğe Effect of fatigue crack propagation on natural frequencies of system in AISI 4140 steel(Techno-Press, 2019) Bilge, Habibullah; Doruk, Emre; Fındık, Fehim; Pakdil, MuratIn this study, we investigated the effect of fatigue crack propagation of the beams which have a vital importance in engineering applications, on the natural frequency of the system. Beams which have a wide range of applications, are used as fundamental structural elements in engineering structures. Therefore, early detection of any damages in these structures is of vital importance for the prevention of possible destructive damages. One of the widely used methods of early detection of damages is the vibration analysis of the structure. Hence, it is of vital importance to detect and monitor any changes in the natural frequencies of the structure. From this standpoint, in this study we experimentally investigated the effect of fatigue crack propagation on beams produced from 4140 steel, of the natural frequency of the beam. A crack was opened on the 8x16x500 mm beam using a 3 mm long and 0.25 mm wide wire erosion. The beam, then, underwent 3 point bending tests at 10 Hz with a dynamic fatigue device and its natural frequencies were measured in scheduled intervals and any changes taking place on the natural frequencies of the beam were measured. This data allowed us to identify and measure the crack occurring on the beam subjected to dynamic loading, during the propagation phase. This method produced experimental data. The experimental data showed that the natural frequency of the beam decreased with the propagation of the fatigue crack on the beam.Öğe Effect of Ni diffusion annealing temperature on crucial characterization of Bi-2223 superconducting system(Amer Inst Physics, 2016) Sarıtekin, Namık Kemal; Kahraman, Mehmet Fatih; Bilge, Habibullah; Zalaoğlu, Yusuf; Pakdil, Murat; Doğruer, Musa; Yıldırım, Gürcan; Öz, MuhammedIn this current work, influence of diffusion annealing temperature (650-850 degrees C) on the electrical, superconducting and structural characterizations of pure and Ni diffused Bi-2223 materials produced by conventional solid-state reaction route is surveyed by dc electrical resistivity (rho-T), transport critical current density (J(c)) and powder X-ray diffraction (XRD) measurements. All the experimental findings indicate that the curial characteristics, being responsible for the novel and feasible applications, improve significantly with the enhancement of the diffusion annealing temperature up to the certain value of 700 degrees C after which they degrade dramatically, meaning that the properties initially get better and better as a consequence of the penetration of more and more Ni concentrations into the superconducting grains or over grain boundaries in the Bi-2223 crystal matrix. From the diffusion annealing temperature value of 700 degrees C onwards, the excess penetration of the Ni nanoparticles along with consecutively stacked layers in the Bi-2223 crystal structure is, however, unfavorable for the attractive and feasible applications due to new induced disorders, local structural distortions and artificial dislocations.Öğe Experimental investigation of the effects of chicken and Turkey biodiesel blends on diesel engine noise emissions(Springer, 2019) Dal, Hüseyin; Emiroğlu, Alaattin Osman; Bilge, Habibullah; Şen, MehmetIn today's technology age, especially in urban areas, one of the most important sources of environmental noise pollution is diesel engines. Due to the limited availability of petroleum-based fuels, produced in only certain regions of the world maps, high cost, and being one of the most important causes of environmental pollution, in recent years, researchers have intensively focused on the study of alternative energy sources. Today, one of the most important alternative energy sources is biodiesel obtained from various natural sources. In this study, the effect of broiler chicken and turkey biodiesel on the noise emission of diesel engines was investigated experimentally. The biodiesels were produced with special methods using broiler chicken and turkey rendering fats. Two different kinds of biodiesels were homogeneously blended into the diesel fuel at proportions of 10%, 20%, and 50%. Engine tests were carried out at full load at various engine speeds and partial loads at a constant speed of 2000 rpm. During the experiments, noise measurements of the engine were taken by hand-held noise analyser. For more detailed assessment, 1/3 octave band noise analysis between 10 and 10 kHz was performed as well. Compared with diesel fuel, results of the noise analyses showed that use of biodiesel blends produced from broiler chicken and turkey rendering fat in diesel fuel has no significantly effect on engine noise emissions. Biodiesels produced from broiler chicken and turkey fats can be used safely in terms of noise emissions as engine fuels.Öğe Improvement of mechanical characteristics and performances with Ni diffusion mechanism throughout Bi-2223 superconducting matrix(Amer Inst Physics, 2016) Sarıtekin, Namık Kemal; Bilge, Habibullah; Kahraman, Mehmet Fatih; Zalaoğlu, Yusuf; Pakdil, Murat; Doğruer, Musa; Yıldırım, Gürcan; Öz, MuhammedThis study is interested in the role of diffusion annealing temperature (650-850 degrees C) on the mechanical characteristics and performance of pure and Ni diffused Bi-2223 superconducting materials by means of standard compression tests and Vickers hardness measurements at performed different applied loads in the range of 0.245-2.940N and theoretical calculations. Based on the experimental findings, the mechanical performances improve with increasing annealing temperature up to 700 degrees C beyond which they degrade drastically due to the increased artificial disorders, cracks and irregular grain orientation distribution. In other words, the penetration of excess Ni inclusions accelerates both the dislocation movement and especially the cracks and voids propagation as a result of the decrement in the Griffith critical crack length. Further, it is to be mentioned here that all the sample exhibit typical indentation size effect (ISE) behavior. In this respect, both the plastic (irreversible) and elastic (reversible) deformations have dominant role on the superconducting structures as a result of the enhancement in the elastic recovery. At the same time elastic modulus, yield strength and fracture toughness parameters are theoretically extracted from the microhardness values. Moreover, the elastic modulus parameters are compared with the experimental values. It is found that the differentiation between the comparison results enhances hastily with the increment in the applied indentation test loads due to the existence of the increased permanent disorders, lattice defects and strains in the stacked layers. Namely, the error level increases away from the actual crystal structure. Additionally, the microhardness values are theoretically analyzed for the change of the mechanical behaviors with the aid of Meyer's law, elastic/plastic deformation and Hays-Kendall approaches for the first time.Öğe Uncertainty analysis of milling parameters using Monte Carlo simulation, the Taguchi optimization method and data-driven modeling(Carl Hanser Verlag, 2019) Kahraman, Mehmet Faith; Bilge, Habibullah; Öztürk, SabriSurface roughness plays an important role in the performance of finished structures. The surface quality obtained is enormously affected by cutting parameters. Therefore, the purpose of the present study is to examine the surface roughness value of aluminum 7075 workpiece material during milling operation by considering three steps: (1) the multi-nonlinear regression (MNLR) modeling basis of Taguchi design, (2) optimization based on signal to noise ratio (S/N), and (3) probabilistic uncertainty analysis depending on Monte Carlo technique as a result of depth of cut, cutting speed and feed rate. The depth of cut of 0.2 mm, cutting speed of 900 m x min(-1), and feed rate of 0.1 mm x tooth(-1) were determined as Taguchi-optimized conditions with a surface roughness of 0.964 mu m. In order to justify the surface roughness predicted under optimized conditions in relation to the predicted Taguchi method, three repetitive verification experiments were performed and surface roughness of 0.964 mu m +/- 0.3% was achieved. The best-fit MNLR method with an R-pred(2) (predicted regression coefficient) of 98.02 % is useful for calculating the success of estimating the outcome variable. Monte Carlo simulations were found to be quite effective for identifying the uncertainties in surface roughness that could not be captured by means of deterministic methods.
