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    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, Cem
    The 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.
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    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, Cem
    Purpose 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.
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    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, Naghdali
    Pressure 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.
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    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, Naghdali
    The 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.
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    Effect of Inhomogeneity Constant on Equivalent Stresses in Elastic Analysis of Hollow Cylinder Made from Functionally Graded Material
    (Gazi Univ, 2020) Boga, Cem
    In this study, the determination of the equivalent stresses required for the elastic analysis of a hollow cylinder made of functional graded material (FGM) subjected to internal and external pressures was determined quickly and accurately, and its evaluation was discussed. The Poisson's ratio is thought to be constant. The functional grading for the modulus of elasticity varies radially along the thickness of the cylinder and depending on a simple power law function. Radial, tangential (hoop) and equivalent stresses with radial displacements in the cylinder are determined rapidly by modeling both analytically and by the finite element method (FEM) numerically. Outcomes of both methods were compared and found to be in harmony. At the same time, differently from previous studies in my paper, the influence of the inhomogeneity constant of the material on equivalent stresses was investigated and the results are presented in graphical form.
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    Effects of ultrasonic welding parameters for solar collector applications
    (Carl Hanser Verlag, 2019) Yeniyil, Emre; Boga, Cem; Esme, Ugur
    Today, ultrasonic welding is used in many different areas due to ease of application compared to other welding methods. Computer, electric, automotive and aerospace industries are the leading areas for these applications. With its ability to easily join materials like Al, Cu, Ni, ultrasonic welding has become a preferred method for use in the welding of solar collectors which are components in solar energy systems. The system parameters for welding solar collectors must of course be adjusted according to the properties of the materials used so that the heat transfer between specimens is not affected. In this study, the selective coated plate and the heat carrier pipes of solar collectors were welded using ultrasonic seam welding, and the optimum welding parameters were determined according to the Cu-DHP copper alloy used. For this purpose, copper specimens were welded using welding speeds of 4, 8, 12 and 16 m x min(-1) and amplitudes of 4, 5 and 6 mu m, while pressure and frequency values were fixed. The shear strength values of these welded specimens were calculated, and images of the weld areas were obtained with the help of a scanning electron microscope. Through hardness measurements made on the interfacial region of the welds, it was concluded that optimal welding performance was obtained at an amplitude of 4 mu m and a welding speed of 12 m x min(-1). At these parameters, a mean shear strength value of 0.1386 MPa and a mean hardness value of 112 HV were measured.
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    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, Naghdali
    Shape 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.
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    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, Burcak
    Among 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.
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    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, Cem
    PurposeThis 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.
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    Investigation of mechanical and fracture behavior of pure and carbon fiber reinforced ABS samples processed by fused filament fabrication process
    (Emerald Group Publishing Ltd, 2021) Boga, Cem
    Purpose Acrylonitrile butadiene styrene (ABS), as a light and high strength thermoplastic polymer, has found extensive applications in different industries. Fused filament fabrication, known as three-dimensional (3D) printing technique is considered a rapid prototyping technique that is frequently applied for production of samples of ABS material. Therefore, the purpose of this study is to investigate the mechanical and fracture behavior of such materials and the techniques to improve such properties. Design/methodology/approach Experimental and numerical analyses have been conducted to investigate the effects of internal architecture and chopped carbon fiber (CF) fillers on the mechanical properties and mixed mode fracture behavior of the ABS samples made by 3D printing technique. Four different filling types at 70% filling ratios have been used to produce tensile and special fracture test samples with pure and CF filled ABS filaments (CF-ABS) using 3D process. A special fixture has been developed to apply mixed mode loading on fracture samples, and finite element analyses have been conducted to determine the geometric function of such samples at different loading angles. Findings It has been determined that the printing pattern has a significant effect on the mechanical properties of the sample. The addition of 15% CF to pure ABS resulted in a significant increase in tensile strength of 46.02% for line filling type and 15.04% for hexagon filling type. It has been determined that as the loading angle increases from 0 degrees to 90 degrees, the KIC value decreases. The addition of 15% CF increased the K-IC values for hexagonal and line filling type by 64.14% and 12.5%, respectively. Originality/value The damage that will occur in ABS samples produced in 3D printers depends on the type, amount, filling speed, filling type, filling ratio, filling direction and mechanical properties of the additives. All these features are clearly dependent on the production method. Even if the same additive is used, the production method difference shows different microstructural parameters, especially different mechanical properties.
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    INVESTIGATION OF MECHANICAL AND METALLOGRAPHIC PROPERTIES OF TWO DIFFERENT ALUMINUM ALLOYS JOINED WITH FRICTION STIR WELDING METHOD USING DIFFERENT WELDING PARAMETERS
    (Yildiz Technical Univ, 2020) Ocalir, Seref; Esme, Ugur; Boga, Cem; Kulekci, Mustafa Kemal
    In this study two aluminum alloy materials of EN AW-5083-H111 and EN AW-6082-T651 were joined with Friction Stir Welding considering the parameters as the tool shoulder diameter, spindle speed and feed rate. The mechanical properties of the weld joints such as yield strength, tensile strength and micro-hardness and metallographic properties were investigated comparatively with the use of these welding parameters. The yield strength of the weld joints were determined to be between 136-217 MPa while the tensile strengths were between 159-230 MPa and the percent elongations were between 2.28-5.44 %. The hardness values measured in weld areas were higher in the EN AW-6082 base metal side compared with EN AW-5083 base metal side.
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    Investigation on the effects of printing pattern on the load carrying capacity of 3D printed U-notched samples
    (Springer, 2022) Seyedzavvar, Mirsadegh; Boga, Cem
    The 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.
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    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, Mirsadegh
    ContextThe 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.
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    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, Touraj
    PurposeThis 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.
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    Proper estimation of surface roughness using hybrid intelligence based on artificial neural network and genetic algorithm
    (Elsevier Sci Ltd, 2021) Boga, Cem; Koroglu, Tahsin
    The surface roughness is a crucial index that is commonly used in the machining process to evaluate the final product quality. This paper investigates the effect of different machining parameters on the surface roughness of the high-strength carbon fiber composite plate, manufactured by utilizing the vacuum infusion process, under dry end milling conditions. Besides, a hybrid intelligence approach consisting of artificial neural network (ANN) whose parameters are tuned by genetic algorithm (GA) is introduced for accurate estimation of surface rough-ness. To construct a database for the ANN, the experimental milling tests have been carried out according to the Taguchi optimization method with the design of a mixed orthogonal array L-32 (2(1) x 4(2)). The influence of the machining parameters such as cutting tools, feed rate, and spindle speed on surface roughness have been examined by using analysis of variance (ANOVA). The analyses reveal that the cutting tool and the feed rate are the most effective factors in the surface roughness of the composite material. It is also determined that the experiment with A1B2C1 combination (TiAlN coated cutting tool, 5000 rpm spindle speed, and 250 mm/rev feed rate) gives the optimal result. The proposed hybrid ANN-GA algorithm provides a good prediction correlation ratio (R = 0.96177) indicating that the estimated and the measured surface roughness values are remarkably close to each other. The mean square error (MSE) specifying the accuracy and adequacy of the network model is obtained as 0.074 during the 33th iteration of the GA.
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    STRESS ANALYSIS OF FUNCTIONALLY GRADED BEAMS DUE TO THERMAL LOADING
    (Taylors Univ Sdn Bhd, 2020) Boga, Cem; Selek, Onur
    In this paper, axial stress analysis of a functionally graded beam (FGB) was performed analytically and numerically under thermal loading. In these analyses, three different FGBs were used. Material properties of these FGBs are varied depending on the power law function along the z axis while Poisson ratio was assumed to be constant along the z-axis. Analytical formulas were given for axial stress analysis along z axis. FGBs were analysed numerically using the ANSYS program. Analytical and numerical results of axial stresses were compared and observed to be in consistence with each other. Then, the effect of different FGB types on axial stress was investigated under thermal loading. After analytical and numerical calculations, it was concluded that the FGM type consisting of Ti-(6Al4V)/Al2O3 metal ceramic pair had the lowest axial stress values. The results are given in graphs.