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Öğe A finite element approach for addressing the interphase modulus and size interdependency and its integration into micromechanical elastic modulus prediction in polystyrene/SiO2 nanocomposites(Elsevier Sci Ltd, 2024) Soudmand, Behzad Hashemi; Biglari, Hasan; Fotouhi, Mohammad; Seyedzavvar, Mirsadegh; Choupani, NaghdaliThe perturbed transitional area between the nanoparticle and matrix shapes the properties of polymer nanocomposites. Due to the stochastic nature of these interphase regions, their size and physical properties are intricately linked. For instance, a higher interphase modulus, Eint, might result from a thinner interphase, and vice versa. The inherent randomness can introduce variability in the interphase modulus with respect to interphase thickness, tint. This challenges the practicality of conventional micromechanical approaches, which assume the interphase modulus to be either a constant or a function of filler and matrix properties when predicting the elastic modulus of polymer nanocomposites. Unlike conventional approaches, which simply used interphase quantification to predict global stiffness and treated the interphase modulus independently of its thickness, this study aims, for the first time, to consider the stochastic nature of the interphase, seeking to exclusively explore the interdependencies within the Eint - tint relationship in polystyrene/SiO2 nanocomposites. Simulations were conducted using finite element analysis, FEA, providing high accuracy and flexibility. To manage the large number of simulations, FEA was streamlined with a customized Python scripting, generating a spectrum of (Eint, tint) solutions for varying SiO2 contents based on experimental measurements and a rigorous methodology. Subsequently, empirical equations were formulated, unveiling the relationship between Eint and tintper composition. The FEA-driven interphase intercorrelation scheme was compared to the results obtained from a modified three-phase Halpin-Tsai model. Additionally, the FEA scheme was utilized to modulate the HT model by adjusting its relevant interphase terms.Öğe A hybrid ANN/PSO optimization of material composition and process parameters for enhancement of mechanical characteristics of 3D-printed sample(Emerald Group Publishing Ltd, 2023) Seyedzavvar, MirsadeghPurposeThis paper aims to study the effects of inorganic CaCO3 nanoadditives in the polylactic acid (PLA) matrix and fused filament fabrication (FFF) process parameters on the mechanical characteristics of 3D-printed components. Design/methodology/approachThe PLA filaments containing different levels of CaCO3 nanoparticles have been produced by mix-blending/extrusion process and were used to fabricate tensile and three-point bending test samples in FFF process under various sets of printing speed (PS), layer thickness (LT), filling ratio (FR) and printing pattern (PP) under a Taguchi L27 orthogonal array design. The quantified values of mechanical characteristics of 3D-printed samples in the uniaxial and the three-point bending experiments were modeled and optimized using a hybrid neural network/particle swarm optimization algorithm. The results of this hybrid scheme were used to specify the FFF process parameters and the concentration of nanoadditive in the matrix that result in the maximum mechanical properties of fabricated samples, individually and also in an accumulative response scheme. Diffraction scanning calorimetry (DSC) tests were conducted on a number of samples and the results were used to interpret the variations observed in the response variables of fabricated components against the FFF parameters and concentration of CaCO3 nanoadditives. FindingsThe results of optimization in an accumulative scheme showed that the samples of linear PP, fabricated at high PS, low LT and at 100% FR, while containing 0.64% of CaCO3 nanoadditives in the matrix, would possess the highest mechanical characteristics of 3D-printed PLA components. Originality/valueFFF is a widely accepted additive manufacturing technique in production of different samples, from prototypes to the final products, in various sectors of industry. The incorporation of chopped fibers and nanoparticles has been introduced recently in a few articles to improve the mechanical characteristics of produced components in FFF technique. However, the effectiveness of such practice is strongly dependent on the extrusion parameters and composition of polymer matrix.Öğe A study on the ?wire-EDM of Ni55.8Ti shape memory superalloy: an experimental investigation and a hybrid ANN/PSO approach for optimization(Springer Heidelberg, 2023) Akar, Samet; Seyedzavvar, Mirsadegh; Boga, CemThe unique properties of high hardness, toughness, strain hardening, and development of strain-induced martensite of nickel-titanium superalloys made the micro-wire electro discharge machining (mu wire-EDM) process one of the main practical options to cut such alloys in micro-scale. This paper presents the results of a comprehensive study to address the response variables of Ni55.8Ti superalloy in mu wire-EDM process, including the kerf width (KW), material removal rate (MRR), arithmetic mean surface roughness (R-a) and white layer thickness (WLT). To this aim, the effects of pulse on-time (T-on), pulse off-time (T-off), discharge current (I-d) and servo voltage (SV) as input parameters were investigated using the experiments conducted based on Taguchi L-27 orthogonal array. The results were employed in the analysis of variance (ANOVA) to examine the significance of input parameters and their interactions with the output variables. An optimization approach was adopted based on a hybrid neural network/particle swarm optimization (ANN/PSO) technique. The ANN was employed to achieve the models representing the correlation between the input parameters and output variables of the mu wire-EDM process. The weight and bias factor matrices were obtained by ANN in MATLAB and together with the feed forward/backpropagation model and developed functions based on PSO methodology were used to optimize the input parameters to achieve the minimum quantities of KW, R-a and WLT and the maximum value of MRR, individually and in an accumulative approach. The results represented a maximum accumulative error of nearly 8% that indicated the precision of the developed model and the reliability of the optimization approach. At the optimized level of input parameters obtained through the accumulative optimization approach, the KW, R-a, and WLT remained nearly intact as compared with the levels of responses obtained in the individual optimization approach, while there was a sacrifice in the machining efficiency and reduction in the MRR in the mu wire-EDM process of Nitinol superalloy.Öğe A study on the effects of internal architecture on the mechanical properties and mixed-mode fracture behavior of 3D printed CaCO3/ABS nanocomposite samples(Emerald Group Publishing Ltd, 2023) Seyedzavvar, Mirsadegh; Boga, CemPurpose The purpose of this study was to investigate the effects of CaCO3 nanoparticles on the mechanical properties, and mixed-mode fracture behavior of acrylonitrile butadiene styrene 3D printed samples with different internal architectures. Design/methodology/approach The nanocomposite filaments have been fabricated by a melt-blending technique. The standard tensile, compact tension and special fracture test samples, named Arcan specimens, have been printed at constant extrusion parameters and at four different internal patterns. A special fixture was used to carry out the mixed-mode fracture tests of Arcan samples. Finite element analyses using the J-integral method were performed to calculate the fracture toughness of such samples. The fractographic observations were used to evaluate the mechanism of fracture at different concentrations of nanoparticles. Findings The addition of CaCO3 nanoparticles has resulted in a significant increase in the fracture loading of the samples, although this increase was not consistent for all the filling patterns, being more significant for samples with linear and triangular structures. According to the fractographic observations, the creation of uniformly distributed microvoids due to the blunting effect of nanoparticles and 3D stress state at the crack tip in the samples with linear and triangular structures justify the enhancement in the fracture loading by the addition of CaCO3 nanoparticles in the matrix. Originality/value There is a significant gap in the knowledge of the effects of different nanoparticles in the polymer samples produced by the fused filament fabrication process. One of such nanoparticles is an inorganic CaCO3 nanoparticle that has been frequently used as nanofillers to improve the thermomechanical properties of thermoplastic polymers. Here, experimental and numerical studies have been conducted to investigate the effects of such nanoadditives on the mechanical and fracture behavior of 3D printed samples.Öğe A transfer learning-based machine learning approach to predict mechanical properties of different material types fabricated by selective laser melting process(Sage Publications Ltd, 2023) Pashmforoush, Farzad; Seyedzavvar, MirsadeghThe necessity for a massive dataset has limited the desirability of the machine learning approaches for industrial applications, especially in the metal additive manufacturing processes, where, collecting a large dataset is expensive and virtually ineffective. Concerning this restriction, an effective machine learning technique should be developed to bridge the gap between the academia and the industry. Hence, in this research, a transfer learning-based artificial neural network (TL-ANN) model was developed to predict the mechanical properties of different metallic specimens fabricated by selective laser melting (SLM) process. This model was integrated with a Bayesian hyperparameters optimization algorithm to select the optimum training parameters of the model. The proposed model consists of a target network and a source network. The source network was trained based on the mechanical properties that were obtained experimentally for various materials, including pure and alloyed copper, steel, titanium, nickel, etc. The overall regression correlation coefficient (R) of the TL-ANN model was about 0.99, with the mean square error of testing, validation, and training of datasets of about 2.031, 1.423, and 1.068, respectively, representing the successful execution of the source network in prediction of the mechanical properties of the SLMed parts. Using the achieved knowledge of the source network, the target network was trained to predict the mechanical properties of the target material (here SLMed pure and alloyed aluminum specimens). The obtained results revealed that with the help of the transfer learning, the hybrid neural network could predict the mechanical properties of SLM-fabricated aluminum parts with a high accuracy level, even with the small number of training dataset of the target material. To demonstrate the influence of transfer learning in the accuracy of the model, a separate network was developed from scratch, i.e. with random initial weights of the neurons. The R-values of the test dataset of the individual model for the output parameters of ultimate tensile strength, relative density, and yield strength of the fabricated aluminum samples were 0.787, 0.742, and 0.817, respectively, as compared with that of TL-ANN model of 0.966, 0.903, and 0.971, respectively, representing an average of 21% enhancement in the accuracy of the predictivity of the model by application of transfer learning algorithm.Öğe Assessing the safety and reliability of type-3 high-pressure composite tanks: a comprehensive analysis of failure metrics(Springer India, 2024) Avcu, Adem; Seyedzavvar, Mirsadegh; Boga, Cem; Choupani, NaghdaliPressure tanks play a pivotal role in various industrial applications, serving as vessels for the storage of gases under different pressures and environmental conditions. The burgeoning interest in hydrogen gas as a clean energy source has necessitated a comprehensive assessment of pressure tank structural integrity, particularly under high-pressure demands exceeding 700 bar. In this study, we systematically investigate the influence of different aluminum alloys, including AL6061, AL7075, and AL7178, reinforced with various fiber/epoxy composite materials. Our primary objective is to identify the optimal combination of liner and composite materials, along with the number of composite layers and fiber winding orientations that minimize distortion energy within the tank's liner and composite layers while maximizing safety factors. Our results indicate that distortion energy decreases as the fiber angle increases from zero to 75 degrees, with the ideal fiber orientation angle shifting with the number of composite layers. The lowest distortion energy levels in the liner were achieved in composite tanks comprising 60 laminates of reinforcing composite material, wound at an orientation angle of [+/- 55 degrees/90 degrees]. Across various internal pressure levels, pressure tanks reinforced with boron/epoxy composite material consistently outperformed other fiber materials. In terms of aluminum liner materials, AL6061 exhibited a remarkable 10.5% reduction in distortion energy on average when compared to AL7075. Safety indices revealed that pressure tanks reinforced with aramid/epoxy composite material provided the highest level of reliability, particularly when applying the maximum principal stress criterion. Carbon/epoxy and graphite/epoxy composites followed closely. In contrast, glass/epoxy and Kevlar/epoxy composites did not meet the stringent safety requirements for high-pressure storage tanks. These findings offer invaluable guidance for designing high-pressure composite tanks, ensuring their structural integrity and safety when storing hydrogen gas at elevated pressures, and exemplify the importance of materials and design considerations for such critical applications.Öğe Characterizing the effects of liner and fiber-reinforced resin composite shell on fracture energy in type-III high-pressure composite tanks(Springer Heidelberg, 2024) Avcu, Adem; Seyedzavvar, Mirsadegh; Boga, Cem; Choupani, NaghdaliThe increasing adoption of fuel-cell vehicles, driven by their environmentally friendly zero-emission features, is a crucial step towards reducing environmental damage. However, current research primarily focuses on stress-related aspects of pressurized tanks, leaving a critical knowledge gap regarding potential fractures within the tank's body, which can accelerate pressure tank failure. This study aims to address this concern by analyzing alternative fiber materials beyond carbon fiber in a finite element analysis model, with the primary objective of enhancing the durability of pressurized tanks for hydrogen-fueled vehicles against fracture loading. The investigation revolves around the fracture behavior of type-III high-pressure composite tanks, pivotal components for the secure operation of hydrogen-powered fuel cell vehicles. Various configurations of Al6061 and Al7178 liners coupled with six distinct fiber materials and six different winding orientations [(+/- 15/90)n]T, (+/- 30/90)n, [(+/- 45/90)n]T, [(+/- 55/90)n]T, [(+/- 60/90)n]T, and [(+/- 75/90)n]T have been meticulously assessed to provide an in-depth analysis of fracture energy behavior in composite tanks. The stress intensity factor (GI) was computed using a compact tension model developed in Abaqus, for all composite variations under consistent conditions, providing a robust foundation for understanding the fracture behavior. Additionally, MATLAB was utilized to calculate the effective elastic modulus for the selected composite materials. Subsequently, the strain energy release rate was derived from the relationship between the GI and the effective elastic modulus of composite tanks. The derived GI revealed notable improvements in fracture resistance for specific composite shells and liner materials, particularly at higher winding orientations. The results emphasized the superior performance of boron-epoxy composite shells for type-III pressure vessels, exhibiting the lowest GI values and exceptional crack resistance. Notably, Al7178 combined with boron-epoxy outperformed Al6061 composites at higher winding orientations, while glass-epoxy shells exhibited greater susceptibility to crack propagation, especially in specific ply orientations.Öğe Experimental investigation and numerical analysis: fracture mechanics and microstructural development in Ni55.8Ti superalloy under mixed-mode loading at different temperatures(Springer, 2022) Seyedzavvar, Mirsadegh; Boga, Cem; Choupani, NaghdaliShape memory alloys (SMAs) and specifically NiTi superalloys have gained significant attention in different industries for their excellent mechanical properties and superior material characteristics including processability, corrosion resistance, cyclic stability and bio-compatibility. Static and dynamic properties of NiTi SMAs, mainly under tensile loadings, have been widely evaluated in pseudoelastic and pseudoplastic states in many studies. However, there is a gap in the literature concerning the fracture failure of these materials under mixed-mode loadings, as these types of loadings are responsible for the most of the material failures in practical applications. This study is aimed at investigating the fracture toughness and microstructure of NiTi ASTM F2063 shape memory superalloy under mixed-mode fracture conditions and various temperatures, ranging from below the A/M phase transformation temperature to above the temperature at which the material behaves pseudoplastically. The material has been characterized using differential scanning calorimetry (DSC) and uniaxial tensile test apparatus under varying temperature to determine the mechanical and metallurgical characteristics before the mixed-mode fracture experiments. The fracture tests have been conducted using a tensile test machine equipped with a temperature control chamber and an in-lab developed special fixture to make the application of mixed-mode loading on a butterfly shaped specimen, known as Arcan sample, feasible. X-ray diffractometry and fractography using scanning electron microscope have been conducted to characterize the mechanism of failure and development of microstructure under different loading modes and temperatures. Finite element analyses were conducted to determine the fracture toughness and strain energy release rate of NiTi superalloy at different loading conditions.Öğe Experimental study and hybrid optimization of material extrusion process parameters for enhancement of fracture resistance of biodegradable nanocomposites(Pergamon-Elsevier Science Ltd, 2023) Seyedzavvar, Mirsadegh; Boga, Cem; Zehir, BurcakAmong the additive manufacturing processes, the material extrusion (ME) is the most popular and affordable technique in production of a wide range of products, from prototypes to the final products, for different industrial sectors. The most popular raw material in this process is the biodegradable polylactic acid (PLA) polymer that offers ease of production in relatively low price and wide applications in synthesis of medical proteases. However, the mechanical strength of fabricated samples and their resistance against the fracture loadings, which are critical for components synthesized for medical applications, are strongly dependent on the ME process parameters and the composition of the base material. Therefore, this study is aimed to address both the strengthening mechanisms of inorganic CaCO3 nanoadditives in the PLA matrix and the influence of ME process parameters on the fracture resistance of fabricated samples. To this aim, the PLA/CaCO3 nanocomposite filaments have been produced by mix-blending/extrusion tech-nique and were employed to fabricate tensile and fracture test samples in ME process under different sets of parameters, including printing speed, layer thickness, filling ratio and printing pattern, determined by Taguchi L27 orthogonal array. The fracture experiments were conducted on a uniaxial tensile test machine using a specially designed fixture that makes the application of mixed-mode loading on fracture samples possible. The results of fracture toughness of specimens were employed as input data to model the response of fabricated samples and to determine the ME parameter levels and nanoparticle concentrations for maximum fracture resistance of fabri-cated samples based on a hybrid algorithm of artificial neural network and ant colony optimi-zation (ANN/ACO). Differential scanning calorimetry was used to characterize the thermal features (i.e. glass transition, crystallization and melting temperatures) as well as the degree of crystallization of ME samples. Scanning electron microscopy of fracture surfaces were employed to study the influence of ME parameters and CaCO3 nanoadditives on the characteristics of fracture of 3D printed specimens under various modes of loading. Overall, the results showed that the effects of ME parameters on the fracture behavior of 3D printed samples are highly inter-connected and, in the case of a semicrystalline polymer, are highly dependent on the physical characteristics of the fabrication process, including the heat transfer and crystallization rate of the matrix.Öğe Exploring mixed-mode fracture behavior and mechanical properties of selective laser sintered polyamide 12 components(Emerald Group Publishing Ltd, 2024) Zehir, Burcak; Seyedzavvar, Mirsadegh; Boga, CemPurposeThis study aims to comprehensively investigate the mixed-mode fracture behavior and mechanical properties of selective laser sintering (SLS) polyamide 12 (PA12) components, considering different build orientations and layer thicknesses. The primary objectives include the following. Conducting mixed-mode fracture and mechanical analyses on SLS PA12 parts. Investigating the influence of build orientation and layer thickness on the mechanical properties of SLS-printed components. Examining the fracture mechanisms of SLS-produced Arcan fracture and tensile specimens through experimental methods and finite element analyses.Design/methodology/approachThe research used a combination of experimental techniques and numerical analyses. Tensile and Arcan fracture specimens were fabricated using the SLS process with varying build orientations (X, X-Y, Z) and layer thicknesses (0.1 mm, 0.2 mm). Mechanical properties, including tensile strength, modulus of elasticity and critical stress intensity factor, were quantified through experimental testing. Mixed-mode fracture tests were conducted using a specialized fixture, and finite element analyses using the J-integral method were performed to calculate fracture toughness. Scanning electron microscopy (SEM) was used for detailed morphological analysis of fractured surfaces.FindingsThe investigation revealed that the highest tensile properties were achieved in samples fabricated horizontally in the X orientation with a layer thickness of 0.1 mm. Additionally, parts manufactured with a layer thickness of 0.2 mm exhibited favorable mixed-mode fracture behavior. The results emphasize the significance of build orientation and layer thickness in influencing mechanical properties and fracture behavior. SEM analysis provided valuable insights into the failure mechanisms of SLS-produced PA12 components.Originality/valueThis study contributes to the field of additive manufacturing by providing a comprehensive analysis of the mixed-mode fracture behavior and mechanical properties of SLS-produced PA12 components. The investigation offers novel insights into the influence of build orientation and layer thickness on the performance of such components. The combination of experimental testing, numerical analyses and SEM morphological observations enhances the understanding of fracture behavior in additive manufacturing processes. The findings contribute to optimizing the design and manufacturing of high-quality PA12 components using SLS technology.Öğe Finite Element Analyses of Stresses Developed in Oil Separator Composite Tank Used in Screw Type Compressor Systems(2022) Gezginci, Volkan; Boğa, Cem; Seyedzavvar, MirsadeghPressure vessels are geometrically cylindrical, spherical or conical work equipment used for the storage and transportation of pressurized fluid. In the case of design and/or manufacturing deficiency, or for the case of improper applications of such vessels due to working conditions, the damages that may occur can cause serious harm to the environment and employees. The aim of this study is to estimate the performance of a typical oil separator pressure vessel used in screw compressor systems, exposed to high pressure and temperature, using finite element method. Here, the aim is to estimate performance of this tank after modifications in design and to compare the results with that of pressure vessel designed using conventional materials. The inner liner of the separator tank is metal material and the other layers are wrapped with three different composite materials, including carbon fiber/epoxy, glass fiber/epoxy and kevlar fiber/epoxy, at different angles, and then were exposed to high pressures in the environment of finite element simulation software. As a result of the study, stress and deformation values were examined and the most suitable material and orientation angle for the composite pressure vessel were decided. According to the results, it was observed that the lowest first-ply equivalent stress value was obtained in glass fiber/epoxy coated separator tanks at 11.25 bar pressure and 45 degree winding angle. In addition, it was observed that the lowest total deformation value was obtained in kevlar fiber/epoxy coated separator tanks at 11.25 bar pressure and 45 degree winding angle.Öğe Investigation on the effects of printing pattern on the load carrying capacity of 3D printed U-notched samples(Springer, 2022) Seyedzavvar, Mirsadegh; Boga, CemThe application of fused filament fabrication (FFF) process has been growing fast in different fields of industries as a practical and cost-effective solution for prototyping and production of functional components. However, the fracture behavior of the printed specimens is a subject of research as there is a need for service reliability and predictable performance of components. In this paper, the effects of internal architecture in FFF process on mixed-mode I/II fracture of U-notched printed samples were experimentally and numerically investigated. The load carrying capacity of U-notched 3D printed parts were calculated using a combined J-integral criterion and equivalent material concept (EMC) to consider the elastic-plastic behavior of the material. The tensile and fracture specimens were printed by biodegradable polylactic acid (PLA) thermoplastic filaments under constant filling ratio and at different filling patterns, namely, 3D infill, hexagonal, linear and triangular. The experiments were performed to determine the transversely isotropic mechanical properties and the fracture loadings of the samples at different loading angles. A finite element model was developed to conduct the J-integral calculation for each sample based on transversely isotropic properties of printed samples and plane-stress analyses. Based on the results, the samples with 3D infill structure possessed the lowest strength, load carrying capacity and fracture toughness as compared with that of other filling patterns. In contrast, the triangular filling pattern incorporated the highest fracture toughness and load carrying capacity in samples produced by FFF technique.Öğe Investigation on the effects of printing pattern on the load carrying capacity of 3D printed U-notched samples(Springer, 2022) Seyedzavvar, Mirsadegh; Boga, CemThe application of fused filament fabrication (FFF) process has been growing fast in different fields of industries as a practical and cost-effective solution for prototyping and production of functional components. However, the fracture behavior of the printed specimens is a subject of research as there is a need for service reliability and predictable performance of components. In this paper, the effects of internal architecture in FFF process on mixed-mode I/II fracture of U-notched printed samples were experimentally and numerically investigated. The load carrying capacity of U-notched 3D printed parts were calculated using a combined J-integral criterion and equivalent material concept (EMC) to consider the elastic-plastic behavior of the material. The tensile and fracture specimens were printed by biodegradable polylactic acid (PLA) thermoplastic filaments under constant filling ratio and at different filling patterns, namely, 3D infill, hexagonal, linear and triangular. The experiments were performed to determine the transversely isotropic mechanical properties and the fracture loadings of the samples at different loading angles. A finite element model was developed to conduct the J-integral calculation for each sample based on transversely isotropic properties of printed samples and plane-stress analyses. Based on the results, the samples with 3D infill structure possessed the lowest strength, load carrying capacity and fracture toughness as compared with that of other filling patterns. In contrast, the triangular filling pattern incorporated the highest fracture toughness and load carrying capacity in samples produced by FFF technique.Öğe Investigation on tribological performance of CuO vegetable-oil based nanofluids for grinding operations(Shanghai University, 2020) Seyedzavvar, Mirsadegh; Abbasi, Hossein; Kiyasatfar, Mehdi; Ilkhchi, Reza NajatiWith ball-bearing and tribofilm lubrication effects, CuO vegetable oil-based nanofluids have exhibited excellent anti-wear and friction reduction properties. In this study, CuO nanofluids were synthesized by a one-step electro discharge process in distilled water containing polysorbate-20 and vegetable oil as a nanoparticle stabilizer and source of fatty-acid molecules in the base fluid, respectively. Pin-on-disk tribotests were conducted to evaluate the lubrication performance of synthesized CuO nanofluids between brass/steel contact pairs under various loadings. Surface grinding experiments under minimum lubrication conditions were also performed to evaluate the effectiveness of the synthesized nanofluids in improving the machining characteristics and surface quality of machined parts. The results of pin-on-disk tests revealed that adding nanofluids containing 0.5% and 1% (mass fraction) CuO nanoparticles to the base fluid reduced the wear rate by 66.7% and 71.2%, respectively, compared with pure lubricant. The lubricating action of 1% (mass fraction) CuO nanofluid reduced the ground surface roughness by up to 30% compared with grinding using lubricant without nano-additives. These effects were attributed to the formation of a lubrication film between the contact pairs, providing the rolling and healing functions of CuO nanoparticles to the sliding surfaces. The micrography of ground surfaces using a scanning electron microscope confirmed the tribological observations. © 2020, Shanghai University and Springer-Verlag GmbH Germany, part of Springer Nature.Öğe Micro-WEDM of Ni55.8Ti shape memory superalloy: Experimental investigation and optimisation(Inderscience Publishers, 2021) Meshri, Hassan Ali M.; Akar, Samet; Seyedzavvar, Mirsadegh; Kiliç, Sadik EnginNickel-titanium superalloy has gained significant acceptance for engineering applications as orthotropic implants, orthodontic devices, automatic actuators, etc. Considering the unique properties of these alloys, such as high hardness, toughness, strain hardening, and development of straininduced martensite, micro-wire electro-discharge machining (?-WEDM) process has been accepted as one of the main options for cutting intricate shapes of these alloys in micro-scale. This paper presents the results of a comprehensive study to address the material removal rate (MRR) and surface integrity of Ni55.8Ti shape memory superalloy (SMA) in the ?-WEDM process. The effects of discharge current, pulse on-time, pulse off-time, and servo voltage on the performance of this process, including MRR, white layer thickness, surface roughness, and micro-hardness of the machined surface, were investigated by multi-regression analysis using response surface methodology (RSM). The optimisation of input parameters based on the gradient and the swarm optimisation algorithms were also conducted to maximise the MRR and minimise the white layer thickness, surface roughness, and micro-hardness of the machined samples. © 2021 Inderscience Enterprises Ltd.. All rights reserved.Öğe Molecular dynamic approach to predict thermo-mechanical properties of poly(butylene terephthalate)/CaCO3 nanocomposites(Elsevier Ltd, 2021) Seyedzavvar, Mirsadegh; Boğa, Cem; Akar, Samet; Pashmforoush, FarzadThermo-mechanical properties of poly(butylene terephthalate) polymer reinforced with carbonate calcium nanoparticles have been investigated using molecular dynamics simulations. Detailed analyses have been conducted on the effects of nanofiller content, at concentration levels of 0–7 wt%, on the mechanical properties of PBT, i.e. Young's modulus, Poisson's ratio and shear modulus. Thermal properties, including thermal conductivity and glass transition temperature, have been determined using Perl scripts developed based on nonequilibrium molecular dynamics and a high temperature annealing procedure, respectively. Experiments have been performed to verify the accuracy of the results of MD simulations. The CaCO3/PBT nanocomposites were synthesized using melt blending and mold injection techniques. The uniaxial tensile test, thermal conductivity, differential scanning calorimetry and x-ray diffraction spectroscopy measurements were conducted to quantify the thermo-mechanical properties of such nanocomposites experimentally. The results showed significant improvements in the mechanical properties by addition of CaCO3 nanoparticles due to strong binding between rigid particles and PBT polymer and high nucleation effects of nanoparticles on the matrix. Thermal conductivity and glass transition temperature of nanocomposites represented a consistent increase with the ratio of CaCO3 nanoparticles up to 5 wt% with an enhancement of 38% and 36% with respect to that of pure PBT, respectively. © 2021 Elsevier LtdÖğe Molecular dynamics simulation and experimental investigation of mechanical properties of calcium carbonate and graphene reinforced polylactic acid nanocomposites(Springer, 2023) Zehir, Burcak; Boga, Cem; Seyedzavvar, MirsadeghContextThe use of Molecular Dynamics (MD) simulations to examine the mechanical characteristics of polymer composites reinforced with calcium carbonate (CaCO3) and graphene (GR) is represented in this work. The effects of CaCO3 and GR nanoadditives in polylactic acid (PLA) matrix in different concentrations were evaluated using the results of MD simulations. Experimental analyses have been conducted to validate the results of MD based on the mechanical properties of fabricated nanocomposites, including modulus of elasticity, shear modulus, and Poisson's ratio. The modeling, computation, and analysis of several simulations on the improved mechanical characteristics of PLA/CaCO3 and PLA/GR nanocomposites are introduced and discussed. The results revealed that the addition of GR nanoparticles were more effective in enhancing the mechanical properties of PLA components as compared with that of CaCO3 nanoparticles, as the modulus of elasticity, shear modulus and Poisson's ratio increased by approximately 21%, 17%, and 16% for addition of 3 wt% GR nanoparticles in the PLA matrix, respectively.MethodsThe mechanical behavior of PLA/CaCO3 and PLA/GR nanocomposites have been simulated based on the molecular dynamic technique using material studio (MS) that enabled the analyses of synergy between the polymer molecules and the nanoparticles. Molecular models for a system of nanocomposites were built by embedding the nano-clusters into an amorphous PLA matrix. Nanoparticles have been modeled as spherical nanoclusters of graphite and calcite unit cells. Molecular models of the pure PLA matrix were also developed for comparison. The relaxed systems of MD simulations have been carried out to calculate the mechanical properties of nanocomposites containing 1, 3 and 5 wt% nanofiller contents. To validate the results of the simulations, the PLA/CaCO3 and PLA/GR nanocomposite granules, containing different weight ratios of the nanofillers in the matrix, have been synthesized by melt-blending technique. These granules have been used to produce tensile test samples by injection molding technique, with different fractions of nanoparticles in the matrix, to study the effects of such nanoadditives on the mechanical properties of the PLA nanocomposites.Öğe Numerical simulation and experimental investigation: Metal spinning process of stepped thin-walled cylindrical workpiece(Murat Yakar, 2022) Seyedzavvar, Mirsadegh; Seyedzavvar, Mirali; Akar, Samet; Abbasi, HosseinMany equipment and devices utilized in the aerospace industry are formed as symmetric parts through high plastic deformation of high strength sheet metal alloys with low thickness. Considering the inherent advantages of the spinning process of simple tooling and concentrated deformation loading, this process can be considered as one of the main options in producing these thin-sectioned lightweight parts. In this study, a Finite Element (FE) model has been developed to simulate the formation of a stepped thin-walled cylindrical workpiece of AISI 316 stainless steel alloy by spinning process. The FE simulation results were employed to investigate the effects of process parameters, including feed rate of the roller and rotational velocity of the mandrel on the distribution of stress and strain in the sheet metal, wrinkling failure, and thinning of the sheet metal during deformation. Experiments were carried out using selective input parameters based on the results of FE simulations. The comparison between FE simulations and experiments revealed that the developed model could predict the thinning of the sheet metals with over 93 % accuracy. Additionally, a good agreement between the experimentally deformed sheet configurations with those resulting from finite element simulations has been observed. © Author(s) 2022.Öğe Optimizing parameters for additive manufacturing: a study on the vibrational performance of 3D printed cantilever beams using material extrusion(Emerald Group Publishing Ltd, 2024) Ekerer, Sabri Can; Boga, Cem; Seyedzavvar, Mirsadegh; Koroglu, Tahsin; Farsadi, TourajPurposeThis study aims to investigate the impact of different printing parameters on the free vibration characteristics of 3D printed cantilever beams. Through a comprehensive analysis of material extrusion (ME) variables such as extrusion rate, printing pattern and layer thickness, the study seeks to enhance the understanding of how these parameters influence the vibrational properties, particularly the natural frequency, of printed components.Design/methodology/approachThe experimental design involves conducting a series of experiments using a central composite design approach to gather data on the vibrational response of ABS cantilever beams under diverse ME parameters. These parameters are systematically varied across different levels, facilitating a thorough exploration of their effects on the vibrational behavior of the printed specimens. The collected data are then used to develop a predictive model leveraging a hybrid artificial neural network (ANN)/ particle swarm optimization (PSO) approach, which combines the strengths of ANN in modeling complex relationships and PSO in optimizing model parameters.FindingsThe developed ANN/PSO hybrid model demonstrates high accuracy in predicting the natural frequency of 3D printed cantilever beams, with a correlation ratio (R) of 0.9846 when tested against experimental data. Through iterative fine-tuning with PSO, the model achieves a low mean square error (MSE) of 1.1353e-5, underscoring its precision in estimating the vibrational characteristics of printed specimens. Furthermore, the model's transformation into a regression model enables the derivation of surface response characteristics governing the vibration properties of 3D printed objects in response to input parameters, facilitating the identification of optimal parameter configurations for maximizing vibration characteristics in 3D printed products.Originality/valueThis study introduces a novel predictive model that combines ANNs with PSO to analyze the vibrational behavior of 3D printed ABS cantilever beams produced under various ME parameters. By integrating these advanced methodologies, the research offers a pioneering approach to precisely estimating the natural frequency of 3D printed objects, contributing to the advancement of predictive modeling in additive manufacturing.Öğe Prediction of white layer formation in ?-WEDM process of NiTi shape memory superalloy: FEM with experimental verification(Springer Science and Business Media Deutschland GmbH, 2021) Ilkhchi, Reza Najati; Akar, Samet; Meshri, Hassan Ali M.; Seyedzavvar, MirsadeghMicroscopic changes in the surface of nickel-titanium (nitinol) shape memory alloys (SMAs) in micro-wire electro-discharge machining (?-WEDM) due to the formation of a resolidified layer on the machined surface, called white layer, are one of the main drawbacks in the processing of such alloys. Since these changes significantly affect the shape memory and elastic recovery characteristics of these alloys, reduction of the white layer thickness (WLT) based on the selection of optimum process parameters is essential to raise the quality of the machined parts. In this regard, a finite element model (FEM) has been developed to simulate the effects of ?-WEDM process parameters, including discharge current, pulse on-time, pulse off-time, and servo voltage, on the heat distributing in Ni55.8Ti SMA to predict the WLT. The flushing efficiency of electric discharges and the effect of flow regime of the dielectric fluid on the heat distribution in the workpiece and the formation of the WLT are analyzed. Experimental data are used to verify the accuracy of the FEM. The results show that the developed model can predict the WLT in ?-WEDM process of Ni55.8Ti SMA with an average error of 14%. The effects of discharge parameters on the formation of the WLT are discussed in details based on the results of the FEM. © 2021, The Author(s), under exclusive licence to Springer-Verlag London Ltd. part of Springer Nature.
