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https://hdl.handle.net/20.500.12587/8657

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Investigation of mechanical and physical properties of PLA and steel-added PLA filament materials used in melted filament manufacturing method
(Gazi Univ, Fac Engineering Architecture, 2024) Er, Ali Osman; Aydınlı, Osman Muhsin
Thermoplastic composite filament materials can be used in the manufacturing method with melted filament, which is among the additive manufacturing methods. Thermoplastic composite filament materials allow obtaining different thermal, chemical, mechanical and surface properties. In this study, PLA filament and PLA-Steel filament materials with approximately 80% by weight of 410L steel powder were compared in terms of impact strength, tensile strength and thermal conductivity properties. As a result of the experiments carried out, the highest impact strength was measured at 14.27 kJ/m2, the highest tensile strength was 41.62 MPa and the highest thermal conductivity was 0.1364 W/mK for PLA material. The highest impact strength was measured at 11.51 kJ/m2, the highest tensile strength was 19.06 MPa and the highest thermal conductivity was 0.2758 W/mK for the steel powder added PLA material. Thus, the impact and tensile strength value of PLA material decreased and the thermal conductivity value increased with the addition of steel powder. Different levels of filling ratio, printing temperature, printing speed and layer thickness printing parameters were used in the production of test specimens. The effects of these pressure parameters on the impact and tensile strength values were investigated. The effects of printing parameters were revealed by the results of ANOVA analysis. In addition, the microstructure of the materials was investigated by scanning electron microscopy.
Inverse Dynamics of Bipedal Gait: The Assumption of the Center of Pressure as an Instantaneous Center of Rotation
(Gazi Univ, 2022) Cellek, Fatih; Kalaycıoğlu, Barış
In the study, an alternative 7-dof dynamical model that can be used in gait analysis of human, bipedal robots and exoskeleton systems is proposed. The dimensions and kinematic data of the model are specified on the basis of anthropometry and kinematic data of real human gait. The 7-link model consists of the trunk, two thighs, two shanks and two feet links. The movement is examined in the sagittal plane and during the single support phase (SSP). Unlike the rotation about a fixed point, it is assumed that the right foot rotates about the center of pressure (COP). The part between the COP and the tip of the toe is considered to be a passive limb which is horizontally on the ground. The effect of this part on dynamic analysis is neglected. The equations of motions are derived by applying Lagrange equations. Using the kinematic data obtained in clinical gait analysis (CGA) conducted by Winter [1], the net joint torques are calculated and then compared with CGA torque data. As a result of the comparisons, it is seen that the curves are overlapped significantly.
İki makine akış tipi öğrenme etkili çizelgelemede ortak teslim tarihinden mutlak sapmaların en küçüklenmesi
(2009) İşler, Mesut Cemil; Çelik, Veli; Toklu, Bilal
Yöneylem araştırmasıyla ilgili pek çok alanda öğrenme etkisinin dikkate alındığı çalışmalar mevcuttur. Buna karşın üretim çizelgelemede bu konuyla ilgili çalışma sayısı az, akış tipinde ise daha azdır. Erken/Geç (E/G) tamamlanma problemi 1990 yılların başına kadar ağırlıklandırılmış mutlak sapma problemi olarak bilinmekteydi. Hem erken hem de geç tamamlanma zamanı çizelgeleme problemlerinde önemli ölçütlerdir. Toplam gecikme ölçütü teslim tarihlerine uyuma ilişkin göstergeleri sağlarken (erken tamamlanan işlere ilişkin sonuçları göz ardı ederek), sadece geç tamamlanan işlerin cezaları ile ilgilenir. Ancak bu eğilim tam zamanında üretim (TZÜ) konusuna olan artan ilgi ile birlikte değişmeye başlamıştır. TZÜ’de erken tamamlanma geç tamamlanma kadar önemlidir. Bu çalışmada iki makine akış tipi ortamlı çizelgelemede ağırlıklı erken/geç tamamlanma performans kriteri ve öğrenme etkili işleme özelliği dikkate alınarak bir tamsayılı programlama modeli önerilmiş ve örnek problemlerle çözüm sonuçları değerlendirilmiştir.
Elektrik ark ve gazaltı kaynağı (MIG) ile birleştirilmiş AISI 1040 çeliğinin mekanik özelliklerine, çeşitli ısıl işlemlerin etkisinin incelenmesi
(2017) Ongun, Alemdar; Uzun, İbrahim; Turgut, Onur Kadir
Bu çalışmada; AISI 1040 çeliği, elektrik ark ve MIG ile kaynatılıp, numuneler üretilmiştir. Kaynaklı ve kaynaksız numuneler tam tavlama, normalizasyon, menevişleme ve gerilim giderme işlemlerine tabi tutulmuşlardır. İşleme tabi tutulan ve herhangi bir ısıl işlem yapılmayan numunelere çekme, üç nokta eğme, çentik darbe ve sertlik testleri yapılmıştır. Numunelerin çekme şekil değiştirmeleri kaynaksız parçaların, kaynaklı parçalara nazaran daha yüksek elde edilmiştir. Kaynaksız ve elektrik ark kaynağı yapılıp, gerilim giderme işlemi görmüş numunelerin akma ve çekme dayanım değerleri birbirlerine yakın elde edilmiştir. Martenzitik yapının dışarıda sert, içeri gittikçe yumuşak bir yapı haline geldiği görülmüştür. Ölçülen sertlik değerlerinin, kaynak dolgu metalinin ortasından başlayıp genelde dışarıya doğru bir artış gösterdiği gözlenmiştir.
Askerî Sistemlerin Yüksek Sıcaklıklara Çıkan Devre Elemanlarının Etkin Olarak Soğutulması
(2019) Demircan, Tolga; Özdemir, Erdem
Birçok askerî sistem ve silahlar elektronik ekipmanlar içermektedir. Bu ekipmanlar çalışmaları sırasında yüksek sıcaklıklara çıkabilmektedir. Bu durum, eğer bu ekipmanlar güvenli çalışma sıcaklıklarına soğutulmaz ise, içerdikleri elektronik devre elemanlarının yanmasına ve tüm askerî sistemin çalışamamasına sebep olabilmektedir. Bundan dolayı, bu çalışmada askerî bir sistemin içerdiği elektronik devre elemanlarının daha etkin bir şekilde soğutulması ele alınmıştır. Bu amaçla, devre elemanlarını temsil eden bir blok şeklinde cismin, askerî sistemlerin ana kartlarının bulunduğu hacmi temsil eden bir kanal hacmi içerisine yerleştirildiği düşünülmüştür. Yüksek sıcaklıklara çıkan bu bloğun, çapraz ve jet akışın birlikte kullanımı ile etkin olarak soğutulduğu varsayılmıştır. Bu amaçla, kanal girişinde sabit hızda bir hava girişi yapılarak, çapraz akış şartları sağlanmıştır. Kanal üst yüzeyinde bulunan bir delikten ise, yine sabit hızda hava girişi yapılmak suretiyle çarpan jet akış koşulları sağlanmıştır. Analizler, çapraz akışın hava giriş koşulları baz alınarak hesaplanan Reynolds sayısının 500, 1000, 1500 ve 2000 değerleri için laminer olarak yapılmıştır. Bu Reynolds sayılarında, jet giriş hava hızının, çapraz akış giriş hava hızına oranı (Vj/Uk) değiştirilerek simülasyonlar tekrarlanmıştır. Sonuç olarak, Reynolds sayısının artışı ile blok yüzeyinden gerçekleşen ısı transferinin arttığı belirlenmiştir. Vj/Uk oranının artması ile ise ikincil jet akışın genel akış yapısı üzerindeki etkisi artmaktadır. Vj/Uk oranı arttıkça, akışkan blok yüzeylerine doğru baskılanmakta ve blok yüzeylerinde oluşan hız ve ısıl sınır tabakalarının bozulmasınca sebep olmaktadır. Bundan dolayı, Vj/Uk oranının artması ile blok yüzeylerinden gerçekleşen ısı transferinin arttığı gözlemlenmiştir.
Binalarda Kullanılan EPS Yalıtım Malzemesinin Farklı Yoğunluklara Göre Isıl İletkenliğinin Deneysel ve Sayısal İncelenmesi
(2018) Tan, Hüsamettin; Doğan, Battal
Binalarda enerji kayıplarının azaltılması günümüzde önemli bir konudur. Bu amaçla enerji kayıplarını azaltmak için uygun ısı yalıtım malzemesinin kullanılması gerekir. Bu çalışmada binalarda kullanılan EPS yalıtım malzemesinin iç yapı görüntüleri kullanılarak elde edilen 2 boyutlu çizimlerin sayısal analiz sonuçlarının deneysel sonuçlar ile karşılaştırması yapılmıştır. Ek olarak farklı yoğunluktaki malzemenin ısıl iletkenliği nasıl etkilediği incelenmiştir. Sonuç olarak her yoğunluk değeri için örnek bir binanın 3 farklı bölgede olması durumunda özgül ısı kaybı belirlenerek farklı yoğunluk değerindeki yalıtım malzemesinin ısıtma ihtiyacını ne oranda etkilediği belirlenmiştir.
Theoretical and experimental investigation of acoustic performance of multi-chamber reactive silencers
(ELSEVIER SCI LTD, 2020) Arslan, Hakan; Ranjbar, Mostafa; Secgin, Erkan; Celik, Veli
The acoustic attenuation and performance analysis for blast flow field inside a silencer is investigated. In this regard, a silencer system is designed to reduce the exhaust noise. The effect of position and the number of the baffles for each design on sound transmission loss have been investigated using theoretical, numerical and experimental studies. Three prototypes are manufactured for the experimental studies. Using the measured results, insertion loss graphics have been obtained. The silencer performances are dependent on the baffle geometry, number and the positions. The experimental results are in a good agreement with the simulation results. It is observed that by considering the same number of baffle numbers but located at various locations, the model which shows the best sound transmission loss performance has also the best insertion loss performance and has the least value of peak sound pressure level. (C) 2019 Elsevier Ltd. All rights reserved.
Long-Term Stability of Ferroelectret Energy Harvesters
(MDPI, 2020) Kayaharman, Muhammed; Das, Taylan; Seviora, Gregory; Saritas, Resul; Abdel-Rahman, Eihab; Yavuz, Mustafa
Cellular polypropylene (PP) has been recently used in energy harvesting applications. In this work, we investigate its viability and long-term stability under various operating conditions. Specifically, the effect of constant stress and stress cycling on output power and long-term stability of ferroelectret energy harvesters is analyzed. Our findings show that after 112 days constant stress significantly increases the piezoelectric charge constant d(33) and output power from 0.51 mu W for a stress-free harvester to 2.71 mu W. It also increases the harvester center frequency from 450 to 700 Hz and decreases its optimal resistance from 7 to 5.5 M Omega.
A Simulation Tool for Kinematics Analysis of a Serial Robot
(SPRINGER INTERNATIONAL PUBLISHING AG, 2020) Kütük, M. Erkan; Dülger, L. Canan; Daş, M. Taylan
Robot programming is a very significant task in the field of robotics. Off-line programming (OLP) is a method performed before robot manipulation. It is the manual editing of the robot code using computer software to simulate the real robotic scenarios. Task sequence planning, short-term production, flexibility during operation and expecting real behaviour of the robots are some of the reasons that make the users prefer OLP. Operations can be visualized in many processes such as welding, cutting, even medical applications. In this study, off-line models are offered including the forward and inverse kinematics of a six Degree-Of-Freedom (DOF) serial robot manipulator (Denso VP-6242G). Robotic Toolbox combined with GUI Development Environment in Matlab (R) is used for the forward kinematics solution. A Matlab (R) Simulink model with Simmechanics blocks is used in the inverse kinematic analysis. Visualization is enriched by 3D Solidworks (R) models of the robot parts. Basic motion examples that can be used in many areas are presented.
The investigation of exergoeconomic, sustainability and environmental analyses in an SI engine fuelled with different ethanol-gasoline blends
(INDERSCIENCE ENTERPRISES LTD, 2020) Doğan, Battal; Erol, Derviş; Kodanlı, Evren
In this study, performance and emission values were obtained under full load by using ethanol-gasoline blends as a fuel at different rates in a spark-ignition engine, and exergy, exergoeconomic and environmental analyses were performed with these values. Exergy of a fuel entering engine and lost exergies through cooling system, exhaust and radiation were calculated. CO, CO2, HC, and NO(X)emissions released from engine into environment were measured, and according to environmental analysis, cost of CO(2)emission was calculated as 393.78 USD/year for E0 fuel and as 306.78 USD/year for E30 fuel at 2,000 rpm. Ethanol-gasoline blends at different rates, environmental damage can be reduced by around 30% on an annual basis. Furthermore, with environmental analysis, lowest engine output power cost was found to be 29.77 USD/MJ in E0 fuel at 2,000 rpm, while highest engine output power cost was found to be 120 USD/MJ in E30 fuel at 4,500 rpm.
Influence of T5 heat treatment on the microstructure and lubricated wear behavior of ternary ZnAl40Cu2 and quaternary ZnAl40Cu2Si2.5 alloysEinfluss der T5 Warmebehandlung auf das Gefuge und das geschmierte Verschleissverhalten von der ternaren ZnAl40Cu2-und der quaternaren ZnAl40Cu2Si2,5-Legierung
(WILEY-V C H VERLAG GMBH, 2020) Bican, O.; Savaskan, T.
A ternary ZnAl40Cu2 and a quaternary ZnAl40Cu2Si2.5 alloys were produced by permanent mold casting and subjected to T5 heat treatment at a temperature of 150 degrees C for 24 hours. The structural, mechanical and lubricated wear properties of these alloys were investigated in the as-cast and heat-treated conditions and the results were compared with those of SAE 65 (CuSn12) plain bearing bronze. Microstructure of the ternary alloy consisted of aluminum-rich alpha, eutectoid conversion product of alpha+eta and epsilon phase located in the interdendritic channels. In addition to these phases, silicon particles were observed in the microstructure of the quaternary alloy. T5 heat treatment caused a considerable amount of reduction in the hardness, tensile strength and wear resistance of ZnAl40-based ternary and quaternary alloys, but improved their ductility and stability. These alloys in the as-cast and heat-treated conditions exhibited lower wear volume or higher wear resistance than SAE 65 bearing bronze. Among the experimental alloys, the optimum mechanical properties and wear performance were obtained from ZnAl40Cu2Si2.5 alloy in both as-cast and heat-treated conditions. Adhesion appeared to be the main wear mechanism for the ZnAl40-based alloys, but abrasion dominated the wear of SAE 65 bronze.
The Effect of Solid Boriding Time on the Structure, Hardness and Corrosion Properties of AISI 5140 Steel
(MAIK NAUKA/INTERPERIODICA/SPRINGER, 2020) Bayca, S. U.; Bican, O.; Yamanel, B.; Hekimoglu, A. P.; Calis, M.
In this study, AISI 5140 steel samples were borided in an electrical furnace at a temperature of 950 degrees C for 4, 6 and 8 h. Structural examinations, hardness measurement and corrosion tests were performed to determine the effect of the boriding time on the microstructure, hardness and corrosion resistance of the steel surface. It was observed that 4 h of boriding treatment resulted in the forming of Fe2B layer on the surface of the AISI 5140 steel. However, when the boriding time exceeded 4 h, FeB phase formed on the surface layer of the steel in addition to the Fe2B phase. It was also observed that both the thickness and hardness of the boride layer increased with the increasing boriding time. The hardness values of the borided sample surface were approximately seven times greater than unborided AISI 5140 steel. The samples subjected to boriding for 4 h showed higher corrosion resistance than the unboriding steel samples. But boriding time of more than 4 h caused a decrease in the corrosion resistance of the AISI 5140 steel.
Effects Of The Boriding Process And Of Quenching And Tempering After Boriding On The Microstructure, Hardness And Wear Of AISI 5140 Steel
(WORLD SCIENTIFIC PUBL CO PTE LTD, 2020) Bican, Osman; Bayca, Salih Uğur; Ocak-Araz, Şule; Yamaneli, Bünyamin; Taniş, Naci Arda
An investigation was made on the effects of the boriding process and of quenching and tempering after boriding on the microstructure, hardness and wear of AISI 5140 steel. In this study, a new boriding agent (Baybora (R)-1) developed for the solid boriding method was used. It was observed that the wear resistance of the borided samples increased by about four times, but the wear resistance of the sample subjected to quenching and tempering after boriding increased by only about two times. Thus, it was determined that quenching and tempering after boriding worsen wear resistance.
Effects of equivalence ratio and CNG addition on engine performance and emissions in a dual sequential ignition engine
(SAGE PUBLICATIONS LTD, 2020) Yontar, Ahmet Alper; Doğu, Yahya
Compared to widening usage of CNG in commercial gasoline engines, insufficient but increasing number of studies have appeared in the open literature during last decades, while engine characteristics need to be quantified in exact numbers for each specific fuel and engine. CNG usage in spark-ignition engine offers many advantages such as high specific power outputs, knock resistance, and low CO(2)emission. Engine performance and emissions are strong functions of equivalence ratio. This study focuses on determination of the effects of equivalence ratio on engine performance and emissions for a unique commercial engine for three fuels of gasoline, CNG, and gasoline-CNG mixture (90%-10%: G9C1). For this aim, the tests and the three-dimensional in-cylinder combustion computational fluid dynamics analyses were employed in quantification of engine characteristics at wide open throttle position. Equivalence ratios were defined between 0.7 and 1.4. The engine's maximum torque speed of 2800 r/min was examined. The tested commercial engine is an intelligent dual sequential ignition engine which has unique features such as diagonally positioned two spark-plugs, dual sequential ignition with variable timing and asymmetrical combustion chamber. This gasoline engine was equipped with an independent CNG port-injection system and a specific engine control unit for CNG. In addition, the engine test system has a concomitant dual fuel delivery system that supplies gas fuel into intake airline while liquid gasoline is injected behind the intake valve. Other than testing the engine, the three-dimensional in-cylinder combustion computational fluid dynamics analyses were performed in Star-CD/es-ice software for the three fuels. The CFD model was built by using renormalization group equations, k-epsilon turbulence model, and G-equation combustion model. Computational fluid dynamics analyses were run for the compression ratio of 10.8:1, equivalence ratio of 1.1, and engine's maximum torque speed of 2800 r/min. Test results show that brake torque for all fuels increases rapidly from the lean blend to the rich blend. The brake-specific fuel consumption for all fuels decreases from phi = 0.7 through the stoichiometric region and then slightly increases up to phi = 1.4. The volumetric efficiencies for three fuels have similar decreasing trend with respect to equivalence ratio. Overall, CNG addition decreases the performance values of torque, brake-specific fuel consumption, volumetric efficiency, brake thermal efficiency, while it decreases emissions of CO2, CO, HC, except NOx. Engine model results show that the maximum in-cylinder pressure is 72 bar at 722 crank angle degree (CAD), 68 bar at 730 CAD, and 60 bar at 735 CAD for gasoline, CNG, and G9C1, respectively. The cumulative heat release for gasoline is 9.09% higher than G9C1, while G9C1 is 15.71% higher than CNG. The CO(2)mass fraction for gasoline is about 22.58% lower than G9C1, while it is 40.32% higher than CNG. The maximum mass fraction value of CO is 0.21, 0.17, and 0.08 for gasoline, CNG, and G9C1, respectively. The CO for G9C1 is overall 60.04% lower than CNG and 67.45% lower than gasoline. At maximum point, HC for G9C1 is 31.43% and 71.43% higher than gasoline and CNG, respectively. CNG has the highest level of NO(x)formation. Maximum NO(x)mass fractions are 0.0098, 0.0070, and 0.0043 for CNG, G9C1, and gasoline, respectively. After the ignition, the flame development is completed at 1.07, 1.18, and 1. 28 ms for gasoline, G9C1, and CNG, respectively. Flame velocities are 28.52, 30.93, and 34.11 m/s for CNG, G9C1, and gasoline, respectively, at 2800 r/min and phi = 1.1. When the time between ignition moment and top dead center moment is considered, the increment rate of flame center temperature is 904.19, 884.10, and 861.77 K/s for CNG, gasoline, and G9C1, respectively. The highest temperature increment rate occurs for CNG.
Stress Analysis of an Arbitrarily-Shaped Structure with an Irregularly-Shaped Hole using Digital Image Correlation
(ELSEVIER, 2020) Kalaycioglu, Baris
Engineering structures commonly have arbitrarily-shaped geometry and contain irregularly-shaped cutouts. The integrity of these structures is significantly influenced by the boundary stresses associated with these cutouts. This paper focuses on the evaluation of the stress of a complicated-shaped structure with an irregularly-shaped hole using a single measured displacement component. Digital Image Correlation (DIC) was utilized herein to record the in-plane displacements of the loaded structure. Considering the complications in providing solely analytical solutions for finite structures or numerical solutions in case of insufficient knowledge of the boundary and loading conditions, this paper demonstrates an effective hybrid technique of experimentally stress analyzing in such situations. Processing only one component of the in-plane displacement information with a stress function provides the full-field stresses, including the edges of the plate. Without the knowledge of the external loading conditions nor the need of physically differentiating the measured displacement to obtain strains, and hence stresses, the proposed hybrid technique simultaneously smoothes the recorded displacement information and evaluates the individual stresses full-field in a strong mechanics foundation (equilibrium and compatibility). To validate and support the proposed hybrid technique based on Airy stress function, the obtained results were compared with the those obtained through thermoelastic stress analysis, finite element analysis, and strain gauges.
Effects of alloy ratio and coating thickness on temperature distribution of thermal barrier coatings
(KOREAN ASSOC CRYSTAL GROWTH, INC, 2020) Öztürk, Can; Demircan, Tolga
Pistons on internal combustion engines that are constantly subjected to high pressure and temperature should be light, resistant to heat, resistant to corrosion and have adequate hardness to work more efficiently and to have longer lifecycles. For this purpose, piston surfaces are coated with thermal barrier that increases resistance against heat and corrosion. In this study, temperature distribution on piston surfaces were numerically analysed for ceramic coating on a piston. For this purpose, it is assumed that 100 mu m NiCrAl coating is applied as bond coat on piston upper surface. This coating was coated with MgZrO3+NiCrAl alloy with different alloy ratios for different coating thicknesses. MgZrO3+NiCrAl alloy thickness was changed between 200 mu m and 600 mu m. For all analysed coating thicknesses, MgZrO3 ratio in the alloy was changed between 100 to 10% and simulations were repeated for different alloy rates. As a result of these analysis, it was determined that as MgZrO3 ratio in the alloy decreased, piston upper surface temperature decreased as well. For all alloy ratios, maximum temperature was observed on piston upper surface. Additionally, it was determined that as piston upper surface coating thickness increased, piston upper surface temperature increased as well.
Experimental investigation of effects of single and mixed alternative fuels (gasoline, CNG, LPG, acetone, naphthalene, and boron derivatives) on a commercial i-DSI engine
(TAYLOR & FRANCIS INC, 2020) Dogu, Yahya; Yontar, Ahmet Alper; Kantaroglu, Emrah
A commercial i-DSI (Intelligent-Dual Sequential Ignition) engine is tested to investigate performance and emissions for single fuels and alternative fuels mixed into gasoline. The novelty of the study is the first time testing of the unconventional mixture of boron derivatives and quantification and comparison of real engine characteristics for 11 different fuels for the same commercial engine. Tested single fuels are gasoline (G100), CNG (CNG100), and LPG (LPG100). While the engine runs with gasoline, gaseous fuels are injected into the intake line at a mass rate of 10% CNG (CNG10) and 5% LPG (LPG5). The engine is also tested by adding 25-50% acetone (A25-A50) and 50% naphthalene (N50) into gasoline. Tests are also performed by mixing boron derivatives of borax-pentahydrate (BP), anhydrous-borax (AB), and boric-acid (BA) into gasoline. Tested fuels worsen engine performance compared to gasoline, except for brake specific fuel consumption (BSFC). There is a positive change in emissions for tested fuels compared to gasoline, except that NOx increases 4-5 times for CNG and LPG. One of the important findings is that, for boron-gasoline mixtures, the torque reduces by 4.0% for BP, 4.4% for AB, and 4.4% for BA. The volumetric efficiency decreases by 6.3% for BP, 7.3% for AB, and 8.5% for BA. The BSFC decreases 5.8% for BP, increases 0.4% for AB and decreases 15.2% for BA. Boron derivatives dissolved in gasoline diversely affect combustion and give some advantage in particular for BA and BP in terms of BSFC. In addition, boron-gasoline reduces the formation of HC and NOx.
A Study of Cloth Seal Leakage Performance Based on Geometry and Pressure Load
(MDPI, 2020) Gorgun, Erdem; Aksit, Mahmut Faruk; Dogu, Yahya
Metal cloth seals have been used increasingly in gas turbines due to their flexibility and superior leakage performance. Leakage performance of a metal cloth seal depends on operating conditions, slot and geometric dimensions. These parameters need to be investigated for the best leakage performance. In this study, pressure drop and critical geometric parameters of typical cloth seal form are investigated with an experimental setup. Slot depth, cloth width, sealing gap, shim thickness, surface roughness, pressure drop, offset and mismatch are selected parameters for the screening experiments. Sixteen experiments were conducted following a two-level Resolution IV fractional factorial experiment design for eight parameters. The results indicated that strong parameters for the leakage performance are pressure drop, cloth width, slot depth and offset. Leakage rate is increased with an increase in slot depth, gap, shim thickness, pressure drop and mismatch. During screening experiments, the experiment with minimum flow rate has 86% lower leakage rate than the experiment with maximum flow rate. For main experiments, a Box-Behnken experiment design is applied to analyze nonlinear effects of four strong parameters on the leakage rate. A closed-form equation is derived based on the data and presented in this study.
The Numerical and Experimental Investigation of the Change of the Thermal Conductivity of Expanded Polystyrene at Different Temperatures and Densities
(Hindawi Ltd, 2019) Dogan, Battal; Tan, Husamettin
The determination of the thermal conductivity of insulation materials depending on which parameters in the application as well as the production is very important. In this direction, the parameters affecting thermal conductivity should be determined to improve the efficiency of the insulation materials. It is also a fact that expanded polystyrene blocks have different thermal conductivities at the same density value depending on the production process. In this study, it was determined, experimentally and numerically, that the thermal conductivity of expanded polystyrene material at different densities is dependent on which parameters and changes in temperature. Expanded polystyrene materials consist of blocks of 30x30cm with density of 16, 21, and 25kg/m(3) and a thickness of 20mm. Thermal conductivity measurements were performed in FOX 314 (Laser Comp., USA) operating in accordance with ISO 8301 and EN 12667 standards. The measurements were made for expanded polystyrene blocks at the average temperatures of 10 degrees C, 20 degrees C, 30 degrees C, and 40 degrees C. The numerical study has three stages as the acquisition of electron microscope images (SEM) of expanded polystyrene blocks, modeling of internal structure geometry with CAD program, and realization of solutions with a finite element-based ANSYS program. Findings from experimental and numerical studies and the parameters affecting thermal conductivity were determined. Finally, it is thought that numerical methods can be used to obtain a preliminary idea for EPS material in determining thermal conductivity by comparing the findings of experimental and numerical studies.
Design of a robot-assisted exoskeleton for passive wrist and forearm rehabilitation
(Copernicus Gesellschaft Mbh, 2019) Kutuk, Mehmet Erkan; Dulger, Lale Canan; Das, Memik Taylan
This paper presents a new exoskeleton design for wrist and forearm rehabilitation. The contribution of this study is to offer a methodology which shows how to adapt a serial manipulator that reduces the number of actuators used on exoskeleton design for the rehabilitation. The system offered is a combination of end-effectorand exoskeleton-based devices. The passive exoskeleton is attached to the end effector of the manipulator, which provides motion for the purpose of rehabilitation process. The Denso VP 6-Axis Articulated Robot is used to control motion of the exoskeleton during the rehabilitation process. The exoskeleton is designed to be used for both wrist and forearm motions. The desired moving capabilities of the exoskeleton are flexion-extension (FE) and adduction-abduction (AA) motions for the wrist and pronation-supination (PS) motion for the forearm. The anatomical structure of a human limb is taken as a constraint during the design. The joints on the exoskeleton can be locked or unlocked manually in order to restrict or enable the movements. The parts of the exoskeleton include mechanical stoppers to prevent the excessive motion. One passive degree of freedom (DOF) is added in order to prevent misalignment problems between the axes of FE and AA motions. Kinematic feedback of the experiments is performed by using a wireless motion tracker assembled on the exoskeleton. The results proved that motion transmission from robot to exoskeleton is satisfactorily achieved. Instead of different exoskeletons in which each axis is driven and controlled separately, one serial robot with adaptable passive exoskeletons is adequate to facilitate rehabilitation exercises.

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