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Öğe Compression behavior of sheet-network triply periodic minimal surface metamaterials as a function of density grading(Sage Publications Ltd, 2024) Temiz, Abdurrahim; Pehlivan, Fatih; Ozturk, Fatih H.; Demir, SermetThis study involved the fabrication and experimental testing of five distinct geometries of triply periodic minimal surface (TPMS) cellular structures characterized by uniform and relative density grading. The specific geometries examined were Schoen-Gyroid, Schwarz-Diamond, Schoen-I-WP, Schwarz-Primitive, and Fischer-Koch S. The experimental tests focused on subjecting these structures to compression loads. Samples were produced with a masked stereolithography (MSLA) printer. The samples had initial and end volume fractions (VFs) ranging from 20% to 60% in increments of 10%, with five varied relative densities. The Taguchi method is utilized to determine the optimal testing parameters, while the Analysis of Variance (ANOVA) test is employed to examine the data. The novelty of this paper is to comprehensively investigate the structural efficiency and versatility of TPMS for various applications by optimizing five different functionally graded TPMSs. The ANOVA findings highlighted the substantial impacts of Initial VF, Final VF, and TPMS type on the observed fluctuations in stress at the first peak. The Initial VF made a significant contribution, demonstrating 28.8% higher effectiveness than the Final VF. The TPMS type had a statistically significant effect on the amount of energy absorbed, revealing that different lattice types have abilities to absorb energy.Öğe The effect of the foam structure and distribution on the thermomechanical vibration behavior of sandwich nanoplates with magneto-electro-elastic face layers(Taylor & Francis Inc, 2024) Pehlivan, Fatih; Esen, Ismail; Aktas, Kerim GokhanThis study examined the thermal vibration of a foam core nanoplate composed of ceramic silicon nitride (Si3N4) and metal biomaterial (Ti-6Al-4V) in the core layer, and cobalt-ferrite (CoFe2O4) and barium-titanate (BaTiO3) in the face layers. The constitutive equation is influenced by various factors, including nonlocal elasticity, thermal expansion, strain gradient elasticity, magnetostrictive, and electroelastic properties, as well as sinusoidal higher-order shear deformation theory (SHSDT) with stretching effect. The study found that the thermomechanical vibration behavior of nanoplates was influenced by the ratio of open cell foam to solid, nonlocal factors, thermal load, electrical and magnetic potentials, and different foam distribution.Öğe Enhancing tensile properties of polymer-based triply periodic minimal surface metamaterial structures: Investigating the impact of post-curing time and layer thickness via response surface methodology(Wiley, 2024) Pehlivan, FatihThis research aims to explore the influence of post-curing time and layer thickness on the tensile characteristics of various triply periodic minimal surface (TPMS) structures produced by mask stereolithography (MSLA). The study determined the best post-curing duration, layer thickness, and TPMS lattice type to improve ultimate tensile strength (UTS) and absorbed energy. To experimentally evaluate the tensile characteristics, a dog bone-shaped specimen was utilized. Three distinct TPMS structures, Gyroid (G), Neovius (N), and Diamond (D), were present in the test region. After investigating many process factors with response surface methodology (RSM), optimization methods are applied to find their best printing procedure. The work shows the novel use of RSM to optimize post-curing and printing parameters on TPMS structure mechanical properties during manufacturing. According to the optimization results, the biggest factor affecting UTS is layer thickness, while the most significant factor increasing energy is curing time. The optimal operating parameters for MSLA printing based on the optimization results are a layer thickness of 0.05 mm, a post-curing period of 40 min, and a lattice type of N. The optimum responses corresponding to the optimum parameters were determined as 7.16 MPa for UTS and 18.16 J for energy.Highlights Optimized the production process parameters of TPMS geometries. Compared TPMS structures for mechanical performance. Identified optimal input parameters to improve UTS and energy absorption. Conducted comprehensive experimental evaluations to validate the optimization. Investigation and optimisation of tensile properties of TPMS structures. imageÖğe The investigation of printing parameters effect on tensile characteristics for triply periodic minimal surface designs by Taguchi(Wiley, 2024) Demir, Sermet; Temiz, Abdurrahim; Pehlivan, FatihThe advent of additive manufacturing also referred to as 3D printing, has brought about substantial changes in the industrial domain, as it possesses the capability to fabricate intricate items with enhanced cost-efficiency and productivity. Fused Filament Fabrication (FFF) is a 3D printing process that has gained significant popularity due to its versatile capabilities and cost-effectiveness. This paper investigates the impact of the printing parameters on the tensile characteristics of Triply Periodic Minimal Surface (TPMS) manufactured using FFF 3D printing. TPMS patterns have unique geometric properties and potential applications, making them an intriguing subject of study. The behavior of three different TPMS lattices with three printing parameters is investigated. Finding the best testing settings is done with the Taguchi method, and the data is analyzed with the Analysis of Variance (ANOVA) test. TPMS pattern was found to be the most effective parameter with 83.78%. While the highest strength was obtained in Schwarz diamond, the highest energy absorption was observed in the Gyroid structure. The contributions of printing parameters to tensile strength are line thickness, printing speed, and layer height, respectively. As line width and printing speed increase, both energy absorption and strength increase. Therefore, 0.40 mm line width and 60 mm/s printing speed give optimum values. When considered for energy absorption, the optimum value is 0.20 mm layer height, while when considered for strength, 0.10 mm layer height is the optimum value. The findings emphasize the importance of optimizing printing parameters for desired mechanical characteristics in 3D printed components and highlight the potential of TPMS structures in various applications. This research contributes to the growing knowledge in additive manufacturing and provides insights into optimizing FFF 3D printing for improved mechanical performance.Öğe MODELING AND SIMULATION OF VIBRATIONS OF RAIL SYSTEM VEHICLES BY USING ELECTRICAL-MECHANICAL ANALOGY(2020-02-21) Pehlivan, FatihRaylı araçların dinamik davranışlarının belirlenmesine yönelik çalışmalar günümüzde hızlı bir şekilde devam etmektedir. Bilim çevreleri raylı araçları çok yüksek hızlara çıkarabilmek için farklı farklı teker-ray etkileşim teorileri geliştirmektedirler. Bu gelişmeler ışığında teker ve ray arasında oluşan temas bölgesi tanımlanarak burada oluşan temas kuvvetleri hesaplanabilmekte ve buradan yola çıkarak raylı araç üzerinde oluşan kuvvetler belirlenebilmektedir. Bunun yanı sıra yolcu konforuna önemli ölçüde etki eden ray pürüzlülükleri farklı simülasyon ortamlarında gerçek zamanlı olarak dinamik test ünitelerinde denenmesine yönelik çalışmalar da geliştirilmeye devam etmektedir. Bu çalışmada, üretimi ve montajı yüksek maliyet gerektiren dinamik raylı araç test ünitelerinin elektrik-mekanik analoji yöntemi ile elektriksel eş değer devresi deneysel ortamda elde edilip, gerçek zamanlı farklı yol şartlarındaki simülasyon çalışmaları, geliştirilen devre üzerinden elde edilmiştir. İlk etapta basit bir kütle-yay-damper sistemi ele alınmıştır. Newton’un ikinci hareket kanunu kullanılarak bu sisteminin serbest cisim diyagramı çizilip hareket denklemleri elde edilmiştir. Daha sonra mekanik ve eşdeğer elektrik devresi oluşturulmuştur. En son olarak da sisteminin transfer fonksiyonu ve Simulink modeli elde edilip bilgisayar ortamında Simulink modeli, transfer fonksiyonu ve eşdeğer elektriksel devresinin karşılaştırılması yapılmıştır. Yapılan işlemler pasif süspansiyon sistemi, iki serbestlik dereceli raylı taşıt modeli ve beş serbestlik dereceli boji modeli için de uygulanmış ve analizler gerçekleştirilmiştir. Sonrasında on serbestlik dereceli yarım raylı taşıtı ele alınmış, matematiksel modeli çıkartılmış, elektrik modelinin doğrulanması için MATLAB Simulink ortamında raylı aracın davranışını analiz etmeyi sağlayan bir şema oluşturulmuş, çapraz korelasyon ile sonuçlar karşılaştırılmıştır. En son olarak da teorik olarak doğrulanmış olan elektrik-mekanik analoji teorisinin deneysel açıdan da karşılaştırılmasını yapabilmek için iki serbestlik derecesine sahip raylı araç modeli üzerinde hem mekanik hem de elektriksel olarak üçer kez deney yapılmış ve elde edilen sinyaller teorik verilerle karşılaştırılmıştır.Öğe Modeling and Validation of 2-DOF Rail Vehicle Model Based on Electro-Mechanical Analogy Theory Using Theoretical and Experimental Methods(Eos Assoc, 2018) Pehlivan, Fatih; Mizrak, Cihan; Esen, IsmailThis paper presents theoretical and experimental results on modeling and simulation of two degrees of freedom rail vehicle by using electro-mechanical similarity theory. In this study, the equations of motion were derived using Newton's second law of motion and then mechanical and equivalent electrical circuits were obtained with the help of a free body diagram. A schema in Simulink allowing analyzing of the behavior of the primary and secondary suspension was created. In order to verify the electrical model, transfer function and schema were developed in Simulink. The simulation results were compared with the experimental data and the comparison showed that the results of the mechanical experiments were close to the simulation results, but the electrical results showed better periodic behavior.Öğe Temperature-dependent thermal buckling and free vibration behavior of smart sandwich nanoplates with auxetic core and magneto-electro-elastic face layers(Springer, 2024) Aktas, Kerim Gokhan; Pehlivan, Fatih; Esen, IsmailThis article addresses the thermomechanical thermal buckling and free vibration response of a novel smart sandwich nanoplate based on a sinusoidal higher-order shear deformation theory (SHSDT) with a stretching effect. In the proposed sandwich nanoplate, an auxetic core layer with a negative Poisson's ratio made of Ti-6Al-4V is sandwiched between Ti-6Al-4V rim layers and magneto-electro-elastic (MEE) face layers. The MEE face layers are homogenous volumetric mixtures of cobalt ferrite (CoFe2O4) and barium titanate (BaTiO3). The mechanical and thermal material properties of the auxetic core and MEE face layers are temperature-dependent. Using Hamilton's principle, governing equations are constructed. To characterize the size-dependent behavior of the nanoplate, governing equations are adapted with the nonlocal strain gradient theory (NSGT). By applying the principles of Navier's technique, closed-form solutions are obtained. Parametric simulations are carried out to examine the effects of auxetic core parameters, temperature-dependent material properties, nonlocal parameters, electric, magnetic, and thermal loads on the free vibration and thermal buckling behavior of the nanoplate. According to the simulation results, it is determined that the auxetic core parameters, temperature-dependent material properties, and nonlocal factors significantly affect the thermomechanical behavior of the nanoplate. The outcomes of this investigation are expected to contribute to the advancement of smart nano-electromechanical systems, transducers, and nanosensors characterized by lightweight, exceptional structural integrity and temperature sensitivity. Also, the auxetic core with a negative Poisson's ratio provides a metamaterial feature, and thanks to this feature, the proposed model has the potential to be used as an invisibility technology in sonar and radar-hiding applications.Öğe Thermomechanical Response of Smart Magneto-Electro-Elastic FGM Nanosensor Beams with Intended Porosity(Springer Heidelberg, 2024) Pehlivan, Fatih; Esen, Ismail; Aktas, Kerim GokhanThis study investigates the behavior of free vibrations in a variety of porous functionally graded nanobeams composed of ferroelectric barium-titanate (BaTiO3) and magnetostrictive cobalt-ferrite (CoFe2O4). There are four different models of porous nanobeams: the uniform porosity model (UPM), the symmetric porosity model (SPM), the porosity concentrated in the bottom region model (BPM), and the porosity concentrated in the top region model (TPM). The nanobeam constitutive equation calculates strains based on various factors, including classical mechanical stress, thermal expansion, magnetostrictive and electroelastic properties, and nonlocal elasticity. The study investigated the effects of various factors on the free vibration of nanobeams, including thermal stress, thermo-magneto-electroelastic coupling, electric and magnetic field potential, nonlocal features, porosity models, and changes in porosity volume. The temperature-dependent mechanical properties of BaTiO3 and CoFe2O4 have been recently explored in the literature for the first time. The dynamics of nanosensor beams are greatly influenced by temperature-dependent characteristics. As the ratios of CoFe2O4 and BaTiO3 in the nanobeam decrease, the dimensionless frequencies decrease and increase, respectively, based on the material grading index. The dimensionless frequencies were influenced by the nonlocal parameter, external electric potential, and temperature, causing them to rise. On the other hand, the slenderness ratio and external magnetic potential caused the frequencies to drop. The porosity volume ratio has different effects on frequencies depending on the porosity model.Öğe Vibration analysis of half rail vehicle model with 10 degrees of freedom based on mechanical-electrical analogy theory(Inderscience Enterprises Ltd, 2021) Pehlivan, Fatih; Esen, Ismail; Mizrak, CihanAim of this paper is to show that vibrations of 10 degree of freedom (10 DOF) half rail vehicle models obtained by both mechanical mechanism and equivalent electrical circuit are identical. Firstly, the system was modelled and then a free body diagram was formed. Afterwards, motion equations of the system were determined using Lagrange's method, mechanical circuit was constructed using force equations and its equivalent electrical circuit was obtained using Kirchoff current law (KCL) and force-flow similarity. Then, a schema was formed by means of MATLAB Simulink to analyse the vibrations of the rail vehicle model. To make simulations, the speed of the rail vehicle model was selected as 400 km/h. As input, track irregularities in American Railway Standard and non-random irregularities were applied to all the wheels separately. As a conclusion, it was observed that the signals taken by both the mechanical and its equivalent electrical circuit appeared similar and the vibration analysis of a complex mechanical system can be modelled not only mechanically but also electrically.
