Yazar "Akbulut, Mustafa" seçeneğine göre listele
Listeleniyor 1 - 5 / 5
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe A Predictive Model for Fatigue Performance in Spot Welded and Bolted Joints(Springer, 2025) Teke, Ibrahim T.; Baykara, Celalettin; Akbulut, Mustafa; Ertas, Ahmet H.This study examines the fatigue behavior of spot-welded and bolted single-lap joints through an integrated framework combining experimental testing, finite element analysis (FEA), and regression modeling. The investigation focuses on how geometric parameters-such as plate width, length, thickness, and overlap length-affect fatigue life under variable loading conditions. Fatigue tests serve as the foundation for developing a predictive model for low-cycle fatigue, while FEA provides detailed insights into stress concentrations at critical regions like weld nuggets and bolt holes. Results show that bolted joints, particularly those using M4 fasteners, exhibit superior fatigue performance due to more uniform stress distribution and reduced localization. Submodel-based FEA confirms these findings, revealing that bolted configurations better disperse stresses compared to the high gradients observed near spot welds. This combined approach enhances fatigue life prediction accuracy and offers practical guidance for optimizing joint geometry in automotive, aerospace, and mechanical engineering applications.Öğe Establishing reduced thermal mathematical model (RTMM) for a space equipment: an integrative review(Emerald Group Publishing Ltd, 2022) Akbulut, Mustafa; Ertas, Ahmet H.Purpose The purpose of this study is to, first, provide an overview of the previously conducted works related to thermal analysis of space equipment, including battery packages, especially lithium (Li)-ion ones. Second, the need for a reduced thermal mathematical model (RTMM) and a procedure devising it is defined. Finally, an experimental steady-state temperature distribution test is conducted to finalize the RTMM study. Design/methodology/approach This study was carried out as part of a development project for thermal analysis of Li-ion battery packages used in a space equipment. The study presents certain stages of the design of the battery pack in parallel with battery technology development. Following a literature review, a numerical thermal analysis is conducted; then interface thermal conductance values are found out by means of the first law of thermodynamics; and the study is completed with the help of an experimental test. Findings The study provides key aspects for a successful battery-package thermal design for a space equipment. Additionally, the study summarizes the experimental results used in the RTMM process and the computed thermal conductance values between node couples. Practical implications Thermal analysis is important and vital in space equipment considering their harsh working conditions and environments. Hence, the study provides a RTMM for the thermal analysis of Li-ion battery packages, instead of a full finite element model, to save computational time and CPU usage. The findings are supported by experimental results. Hence, presented details can be used as guidelines for enterprises having a goal of battery package technology achievement, including design and manufacturing. Originality/value After providing a literature review of studies conducted on satellite subsystems including Li-ion batteries, this study presents a clear, complete and verified process of a RTMM for a Li-ion battery package in aero/space structures design. It presents details of building up a model and calculation methodology through an iterative procedure in which an optimization algorithm known as particle swarm optimization (PSO) was benefitted. In the RTMM, additionally, experimental temperature distributions obtained through thermal vacuum test were presented. It has been shown that the model can be used reliably in designing space equipments.Öğe Investigation on strength loss in buckling of composite columns subjected to fatigue loading(Springer Heidelberg, 2024) Akbulut, Mustafa; Yilmaz, Yasin; Ertas, Ahmet H.In current research, the loss in buckling strength of a composite column has been calculated at various phases of its total fatigue cycles, and a comparison between damaged and undamaged columns has been made. The calculation scheme is built upon a progressive methodology and verified according to the experimental outputs of previous research available in the literature. The buckling loads have been computed numerically for composite columns subjected to partial fatigue loadings corresponding to certain predefined percentages of their total fatigue life. Two axial load magnitudes were used in the fatigue process. Several types of geometric cutouts were considered, as well as the sample with no cutout. It was found that cutouts introduced to the column samples significantly affect the buckling strength of partially fatigued samples. The samples with no cutout can preserve buckling strength for up to 40% of the total fatigue life without undergoing any substantial loss. For the higher fatigue load case, especially for the samples with elliptic and circular cutouts, the buckling strength loss is relatively smaller as compared to the lower fatigue load case (around 50 to 66%). The results were presented and interpreted.Öğe Studying the Connection Between Fatigue Life and Modal Characteristic in Composite Structures Having Geometrical Singularities(Springer, 2025) Akbulut, Mustafa; Ertas, Ahmet H.The relationship between fatigue life and modal parameters, such as natural frequencies, in fiber-reinforced polymer (FRP) composite structures was investigated. A progressive model of fatigue life prediction was utilized to estimate the fatigue life of a composite column subjected to cyclic loading, with modal analysis serving as the primary evaluation method. The methodology involves tracking natural frequency changes to correlate stiffness degradation with fatigue life. Validation of the model was conducted using previously studied composite components with varying geometric configurations. The results demonstrate a proportional decrease in natural frequencies with stiffness degradation, providing a reliable basis for estimating the fatigue life of composite structures.Öğe Topology optimization and fatigue analysis of a lifting hook(Elsevier B.V., 2021) Teke, Ibrahim T.; Akbulut, Mustafa; Ertaş, Ahmet HanifiIn this study, a lifting hook has been redesigned with topology optimization and fatigue analysis has been done. With a density-based method, volume minimization has been achieved. All processes have been realized with the help of finite element method implemented in a commercial software. A standard lifting hook model has been used in the process. After optimization, the standard lifting hook was remodeled with CAD software. Then the new model was analyzed. This process has been repeated for three different models. On the basis of the obtained results, the topology optimization undertaken within the scope of the study demonstrates that it is possible to redesign a lifting hook with reduced weight and at the same time to satisfy the required strength properties.
