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Öğe A new hybrid approach for reliability-based design optimization of structural components(Carl Hanser Verlag, 2019) Demirci, Emre; Yıldız, Ali RızaReliability-based design optimization (RBDO) is an effective method for structural optimization due to its ability to take into consideration uncertainties in design variables. Performance measure approach (PMA) based methods are commonly utilized to evaluate the probabilistic constraints of RBDO problems. The advanced mean value (AMY) method is a very commonly used due to its simpleness and effectiveness. However, the AMV method sometimes produces unstable and inefficient results for concave and highly nonlinear limit-state functions. In order to improve robustness and efficiency, many methods have been developed, for example, chaos control based and conjugate gradient-based methods. These methods lead to more stable results as compared with the AMV approach but they are inefficient for use in complex and convex limit-state functions. The RBDO of structural components is often a difficult issue due to complicated constraints. In this paper, a novel hybrid approach, referred to as "hybrid gradient analysis (HGA)" is introduced for the evaluation of both convex and concave constraint functions in RBDO. The HGA method combines AMV and conjugate gradient analysis (CGA). The robustness, simpleness and effectiveness of the proposed HGA method are compared with various PMA methods aimed at reliability such as AMV, chaos control (CC), conjugate mean value (CMV), modified chaos control (MCC), hybrid mean value (HMV) and CGA methods by means of several nonlinear convex/concave limit-state functions and structural RBDO problems. Reliability analysis and RBDO results point out that the HGA approach introduced here is more effective and robust than the well-known approaches.Öğe An experimental and numerical investigation of the effects of geometry and spot welds on the crashworthiness of vehicle thin-walled structures(Carl Hanser Verlag, 2018) Demirci, Emre; Yıldız, Ali RızaThis paper aims to develop a new crash box with improved crashworthiness at reduced cost and weight as a base design for use in the automotive industry. Firstly, a baseline crash box model as presently used by the automotive industry was comprehensively examined by numerical crash analysis using Ls-Dyna software.. Considering the initial design geometry, forty-five different crash box designs were developed by making changes in the geometry and wall thickness of the thin walled structures. The effects of the changes in wall thickness and geometry in alternative crash box designs on crash performances such as total energy absorption, peak crush force, mean crush force, specific energy absorption and crush force efficiency were investigated. The optimum crash box design obtained numerically was validated experimentally by means of the drop tower impact system. The numerical crash analysis results clearly agree with the experimental test results. In this study, a new crash box design at a lower cost and performing better in crashes compared with the other forty-six designs has been obtained and can be used in the automotive industry as an energy absorber. The results have revealed that crash box geometry, as well as the number and position of the spot welds and sheet-metal thickness have an important effect on crash performance, weight and cost of the crash boxes.Öğe An investigation of the crash performance of magnesium, aluminum and advanced high strength steels and different cross-sections for vehicle thin walled energy absorbers(Carl Hanser Verlag, 2018) Demirci, Emre; Yildiz, Ali RizaIn this paper, the effect of conventional steel, new generation DP-TRIP steels, AA7108 - AA7003 aluminum alloys, AM60 - AZ31 magnesium alloys and crash-box cross-sections on crash performance of thin-walled energy absorbers are investigated numerically for the lightweight design of vehicle structures. According to finite element analysis results, crash performance parameters such as total energy absorption, specific energy absorption, reaction forces and crush force efficiencies are compared for the above-mentioned materials. The energy absorption capability of steel energy absorbers is better than that of aluminum and magnesium absorbers. On the other hand, the energy absorption capacity per unit mass of energy absorbers made from lightweight materials is higher than that of steel energy absorbers. This advantage of lightweight alloys encourages automobile manufacturers to use them in designing structural vehicle components.Öğe Evaluation of Jute-Glass Ratio Effects on the Mechanical, Thermal, and Morphological Properties of PP Hybrid Composites for Sustainable Automotive Applications(Mdpi, 2025) Ozyer, Tunahan; Demirci, EmreThis study investigates polypropylene (PP)-based biocomposites reinforced with systematically varied jute and glass fiber ratios as sustainable, lightweight alternatives for semi-structural automotive parts. Four formulations (J20/G0, J15/G5, J10/G10, J5/G15) with a constant 20 wt% total fiber were produced by injection molding and characterized through mechanical, thermal, and morphological analyses. Tensile, flexural, and Charpy impact tests showed progressive improvements in strength, stiffness, and energy absorption with increasing glass fiber content, while ductility was maintained or slightly enhanced. SEM revealed a transition from fiber pull-out in jute-rich systems to fiber rupture and stronger matrix adhesion in glass-rich hybrids. Thermal analyses confirmed the benefits of hybridization: heat deflection temperature increased from 75 degrees C (J20/G0) to 103 degrees C (J5/G15), and thermogravimetry indicated improved stability and higher char residue. DSC showed negligible changes in crystallization and melting, confirming that fiber partitioning does not significantly affect PP crystallinity. Benchmarking demonstrated mechanical and thermal performance comparable to acrylonitrile-butadiene-styrene (ABS) and acrylonitrile-styrene-acrylate (ASA), widely used in automotive components. Finally, successful molding of a prototype exterior mirror cap from J20/G0 validated industrial processability. These findings highlight jute-glass hybrid PP composites as promising, sustainable alternatives to conventional engineering plastics for automotive engineering applications.Öğe Experimental and numerical investigation of crashworthiness performance for optimal automobile structures using response surface methodology and oppositional based learning differential evolution algorithm(Walter De Gruyter Gmbh, 2023) Yildirim, Ahmet; Demirci, Emre; Karagoz, Selcuk; Ozcan, Sevket; Yildiz, Ali RizaIn this study, experimental and numerical crash analyses are carried out to reach an optimum bumper beam and energy absorber design for a passenger car. Design parameters have been created to determine the most crash-efficient bumper beam and energy absorber models. The models that are formed by using Taguchi tables are subjected to crash analysis, and the responses are obtained to find an optimal design. Response surface methodology is used to approximate the structural responses in crash analysis, and the optimum bumper beam and energy absorber models are obtained by the differential evolution algorithm. The optimum model is subjected to crash analysis in the Hyperform software without considering the sheet metal forming effect. Besides, the model is analyzed by incorporating forming history into the crash analysis. As a result of the numerical analysis, a new energy absorber and bumper beam model with the better crash performance and weight reduction are obtained.Öğe Güvenilirlik temelli optimizasyon teknikleri ile taşıt elemanlarının tasarımı için yeni yaklaşımların geliştirilmesi(Bursa Teknik Üniversitesi, 2018) Demirci, Emre; Yıldız, Ali RızaMühendislik yapılarının deterministik tasarım optimizasyonunda, tasarım değişkenlerindeki belirsizlikler ihmal edilir ve hesaba katılmaz. Ancak, geometrik boyutlar, malzeme özellikleri, dış yükler, imalat sürecindeki toleranslar ve işletme koşulları gibi unsurlar bir takım belirsizlikler içerirler. Güvenilirlik temelli tasarım optimizasyonu (RBDO), tasarım değişkenlerindeki bu belirsizlikleri dikkate alarak güvenlik ve üretim maliyetleri arasında en iyi dengeyi bulmak için kullanılan bir metodolojidir. Bir RBDO problemi genel olarak iç içe geçmiş iki döngüden oluşan yöntemler ile çözülür. İç döngü güvenilirlik analizi için performans fonksiyonu değerlendirmesi yaparken, dış döngü ise her bir iterasyonda iç döngüyü çağırarak deterministik optimizasyonu gerçekleştirmektedir. Güvenilirlik analizi için performans fonksiyonunun değerlendirilmesinde en yaygın kullanılan iki yaklaşım, güvenilirlik indeksi yaklaşımı (RIA) ve performans ölçümü yaklaşımıdır (PMA). Daha etkin bir yaklaşım olan PMA ile yapılan güvenilirlik analizlerinde olasılıksal kısıt fonksiyonlarının değerlendirilebilmesi için birçok yöntem geliştirilmiştir. Ancak bu yöntemler her problem için doğru sonuca ulaşamamakta veya hesaplama açısından verimsiz olabilmektedirler. Bu tez çalışmasında PMA ile güvenilirlik analizi için, hibrit gradyan analizi (HGA), hibrit eşlenik gradyan analizi (HCGA) ve geliştirilmiş hibrit gradyan analizi (EHGA) adları verilen üç farklı yeni yöntem geliştirilmiştir. Geliştirilen bu yöntemlerin optimum sonuca ulaşmadaki doğruluğu, kararlılığı ve verimliliği, literatürde yaygın olarak kullanılan; geliştirilmiş ortalama değer (AMV) yöntemi, eşlenik ortalama değer (CMV) yöntemi, hibrit ortalama değer (HMV) yöntemi, kaos kontrol (CC) yöntemi, değiştirilmiş kaos kontrol (MCC) yöntemi ve eşlenik gradyan analizi (CGA) yöntemi ile karşılaştırılmıştır. Bu amaçla hem geliştirilen yöntemlerin hem de kıyaslama için kullanılan mevcut yöntemlerin algoritmaları oluşturulmuş ve MATLAB ortamında kodları yazılmıştır. Güvenilirlik analizlerinin karşılaştırılması farklı tipteki performans fonksiyonlarının değerlendirilmesi ile yapılmıştır. RBDO karşılaştırmalarında ise bazı genel mühendislik problemleri ile taşıt yapısal elemanlarının tasarım problemleri ele alınmıştır. Güvenilirlik analizleri ve RBDO sonuçlarına göre problemlerin geneli ele alındığında, geliştirilen yeni yöntemlerin mevcut yöntemlerden daha verimli olduğu ve doğru sonuca daha hızlı bir şekilde yakınsadığı görülmüştür.Öğe IMPROVING THE VEHICLE CRASH SAFETY WITH HIGH PERFORMANCE ENERGY ABSORBERS(TMMOB Makina Mühendisleri Odası, 2015) Yıldız, Ali Rıza; Demirci, EmreDepending on the increasing number of vehicles in recent years, traffic accidents have been increasing significantly. Frontal crash is the most common types of vehicle accidents. In this study, crash performances of the energy absorbers were investigated using finite element method and experimentally. Energy absorbers with different geometry are designed and a new energy absorber which has better crash performance, peak force and cost than initial design is developed. The numerical crash analysis results show that the weight reduction is 0,02 kg and increasing the amount of the specific energy absorption is 170 J/kg for the best design.Öğe Lightweight design of an automobile hinge component using glass fiber polyamide composites(Carl Hanser Verlag, 2018) Güler, Taner; Demirci, Emre; Yıldız, Ali Rıza; Yavuz, UğurIn recent years, there has been a great deal of interest in lightweight vehicle design due to regulations about reducing fuel consumption and emissions. Lightweight design of vehicle components is one of the most important research topics in vehicle design. Developing the optimum structure in the early stages of design process is very important for minimizing the vehicle weight and production costs. In this paper, an automobile hinge component has been developed using PA66 GF60 glass fiber-reinforced polyamide composite materials instead of conventional steel. The automobile hinge component has been conceived using computer aided design software. Topology optimization was made under specific loadings subject to the constraints of finite element method analysis. As a result of this study, optimum dimensions of the component have been obtained and the weight of the component has been reduced via structural topology optimization techniques while satisfying displacement and stress conditions. The results show that composite materials are an important alterative in lightweight vehicle design.Öğe Low-Velocity Stone Impact Simulation of Glass Fiber Reinforced Thermoplastics for Diesel Engine Oil Pans under Different Temperature Conditions(Otomotiv Mühendisleri Derneği, 2025) Türközü, Batuhan; Demirci, EmreAs environmental regulations continue to evolve, lightweight and high-performance materials have gained increasing attention in the automotive industry. While the shift from metallic to polymer-based engine components contributes to improved fuel efficiency and lower emissions, such transitions also require careful assessment of structural durability under real-world conditions. In this study, a thermoplastic oil pan was developed with design features optimized for impact resistance, including longitudinal and transverse ribs, integrated baffles, and reinforced mounting surfaces. A finite element model of the oil pan was developed in Hypermesh and simulated using Altair Radioss to assess its performance under localized stone impacts, which were modeled using a 17?mm diameter, 6?g rigid sphere. Two impact scenarios—targeting ribbed and non-ribbed regions—were evaluated under three temperature conditions: ?40?°C, 23?°C, and 100?°C. Five glass fiber–reinforced thermoplastic composites (PA6-GF30, PA66-GF30, PPA-GF30, PBT-GF30, and PA9T-GF30) were analyzed in terms of energy absorption, maximum local displacement, and damage behavior. The results showed that rib structures effectively reduced crack formation and localized stress, especially at lower temperatures. Performance depends on impact location, so no single material ranks best in all cases; ribbed regions tend to favor PA6/PA66, whereas non-ribbed regions can favor PPA/PBT. Although no physical tests were conducted, the material modeling was supported by experimental data in the literature. This study contributes to the growing body of knowledge on lightweight thermoplastic oil pans and offers a practical methodology for evaluating their impact performance under service-like conditions.Öğe Multi-objective optimization of aluminum foam-filled battery boxes for electric vehicle safety(Latin Amer J Solids Structures, 2025) Yay, Ismail; Demirci, Emre; Ozcan, Ahmet RemziIn this study, a multi-objective optimization methodology is used to assess the crashworthiness of an aluminum foam-filled battery box designed for passenger cars. Unlike most research focusing on axial crushing, this work investigates the less-explored side pole impact scenario in electric vehicle battery boxes. Finite element simulations are conducted to reduce peak crushing force (PCF) and increase specific energy absorption (SEA) compared to the initial design. Key design variables include aluminum foam densities, wall thickness, and cross-sectional dimensions of battery box components. Four surrogate models are evaluated to approximate the simulation results, and the Non-Dominated Sorting Genetic Algorithm (NSGA-II) is employed to achieve optimal outcomes. The results show that the optimized design significantly improves crashworthiness, achieving a 50.71% increase in SEA and an 11.56% reduction in PCF. Foam density plays a crucial role in controlling deformation behavior under impact conditions. These findings offer a new approach to designing battery boxes with enhanced crashworthiness for electric vehicles.Öğe Optimal design of a robot gripper arm using the chaotic animated oat optimizer(Walter De Gruyter Gmbh, 2026) Ozcan, Ahmet Remzi; Demirci, Emre; Mehta, Pranav; Yildiz, Ali RizaThis study presents a modified version of the Animated Oat Algorithm (AOA), enhanced through the integration of chaotic maps, termed the Chaotic Animated Oat Algorithm (CAOA). Inspired by the seed dispersal mechanisms of the oat plant, AOA offers a population-based metaheuristic framework suitable for complex global optimization tasks. The proposed CAOA was evaluated across four real-world engineering optimization problems: pressure vessel design, bolted rim coupling, gear train cost minimization, and robot gripper arm weight reduction. Results demonstrate that CAOA consistently outperforms traditional and state-of-the-art metaheuristics in terms of solution quality, convergence stability, and robustness, affirming its potential for widespread engineering applications.Öğe Optimization of thin-wall structures using hybrid gravitational search and Nelder-Mead algorithm(Carl Hanser Verlag, 2016) Yıldız, Ali Rıza; Kurtulus, Enes; Demirci, Emre; Yıldız, Betül Sultan; Karagöz, SelçukIn literature, a lot of research works have been presented on crashworthiness in order to develop crash performance of vehicles and thin-wall structures. In this research, a new hybrid optimization algorithm based on gravitational search algorithm and Nelder-Mead algorithm is introduced to improve crash performance of vehicles during frontal impact. The results show that the hybrid approach is very effective to develop crash performance of the vehicle components and thin-wall structures.Öğe Taşıtlarda önden çarpışma performansını etkileyen enerji yutucuların optimum tasarımı(Bursa Teknik Üniversitesi, 2014) Demirci, Emre; Yıldız, Ali RızaTrafik kavramı var olduğundan bu yana kara yollarında trafik kazaları meydana gelmekte, alınan tüm önlemlere rağmen trafik kazalarında büyük oranda can ve mal kayıpları yaşanmaktadır. Ölümle sonuçlanan trafik kazalarında meydana gelen artış otomotiv sektörünün yeni arayışlar içine girmesine sebep olmuş, daha güvenli araçların tasarım ve üretimini bir seçenek olmaktan çıkararak zorunlu hale getirmiştir. Türkiye İstatistik Kurumu ve Emniyet Genel Müdürlüğünce hazırlanan trafik kaza istatistikleri raporuna [8] göre ülkemizde 2011 yılında meydana gelen toplam 1.195.172 adet trafik kazasının 131.845 adedi ölüm ve yaralanmalı kaza olup bu kazalarda toplam 3835 ölüm ve 238.074 adet yaralanma meydana gelmiştir. Anılan raporda belirtilen kazaların meydana getirdiği maddi hasarlar ve insan kayıplarının oldukça yüksek olması daha güvenli taşıtlar tasarlamanın önemini göstermektedir. Trafikte en çok karşılaşılan taşıt kaza türlerinden biri önden çarpışmalı kazalardır. Bu tez çalışması kapsamında, önden çarpışmalı kaza durumu için pasif güvenlik sistemlerinden biri olan enerji yutucuların çarpışma performansları incelenmiştir. Bu amaçla, farklı karakteristik özelliklerde enerji yutucular tasarlanmış ve hem nümerik hem de deneysel olarak test edilmiştir. Tasarım ve test çalışmaları kapsamında, başlangıç modeli olarak ele alınan enerji yutucuya göre daha fazla enerji emebilen, reaksiyon kuvvetlerinin ve maliyetlerin azaltıldığı yeni bir enerji yutucu modelinin ortaya konulması hedeflenmiştir. Enerji yutucuların geometrileri ve et kalınlıklarında değişiklikler yapılarak alternatif enerji yutucu modelleri oluşturulmuştur. Çarpışma analizlerinde enerji yutucular taşıttan bağımsız olarak rijit bir duvar ile çarpıştırılmış ve performansı en iyi olan enerji yutucu modeli belirlenmiştir. Anahtar kelimeler: Çarpışma analizi, Enerji yutucu, Optimum tasarımÖğe THE EFFECT OF NOZZLE DIAMETER AND LAYER THICKNESS ON MECHANICAL BEHAVİOUR OF 3D PRINTED PLA LATTICE STRUCTURES UNDER QUASI-STATIC LOADING(2023) Demirci, Emre; Senaysoy, Safa; Tuğcu, Salih EmreLattice structures are widely preferred because they have good properties such as lightness, high energy absorption capacity and strength. Moreover, these lattice structures can be produced by utilizing 3D printer. Therefore, this study aimed to investigate the effect of the mechanical behavior of the different printing parameters on the lattice structures. Firstly, FBCC and FBCCZ lattice structures were printed with various printing parameters such as nozzle diameter of 0.25 mm-0.4 mm and layer thickness of 0.1 mm–0.15 mm. Then, quasi-static compression tests were carried out to determine the mechanical behavior of lattice structures. Force-displacement behavior, equivalent elastic modulus and energy absorption capabilities of lattice structures printed with different parameters were calculated from the results of quasi-static compression test. According to the results, it was observed that the mechanical behavior was significantly affected when the nozzle diameter and layer thickness were changed. It was determined that the strength and energy absorption of the structures printed with a nozzle diameter of 0.25 mm and a layer thickness of 1.5 mm were decreased. In addition, it was observed that the effect of the printing parameters on the mechanical behavior can be different according to the lattice type and lattice rod diameter.Öğe Topography and topology optimization of diesel engine components for light-weight design in the automotive industry(Carl Hanser Verlag, 2019) Yıldız, Ali Rıza; Kilicarpa, Ulas Aytac; Demirci, Emre; Dogan, MesutThis paper focuses on the optimal design of connecting rods and optimal design of a particle sensor system in diesel engines in order to save material, reduce costs and enhance quality. Optimization is very significant for developing better designs and means less material, lower costs and better conditions. Topology and topography optimization are new but likewise very important optimization approaches for the automotive industry. One of the aims of this study is to create an optimal design for connecting rod components and to use these components in diesel engines to comply with new emission regulations. An analysis of the connecting rods of an existing model was conducted using mathematical data obtained from numerical formulas in order to determine if the part was suitable for topology optimization. According to the results obtained from the topology optimization of the existing model, a new design was created. A comparison of the new design with the existing one showed that the mass of the model was reduced by 18%, while all product expectations were me. Another purpose of the study is to provide an optimal design for a particle sensor system and utilize this system in automobiles to achieve the new emission values required by Euro-Norm 6c regulations. Within the scope of this optimization study, a specific particle measurement system foreseen for Renault 1.5 dCi engines was considered and designed optimally. According to the output of the topology and topography optimization methods, the particle sensor system was designed optimally, and the mass of the system was reduced by 26.7%.
