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1 - Functionally Graded Materials: Processing Techniques and Applications
A Rabieifar V Abouei Mehrizi M Ghanbari HaghighiFunctionally graded materials (FGMs) revealed an immense growth with worldwide demand. This paper describes a brief review of the feasibility of production methods (solid, liquid, and gaseous methods) chosen for FGMs, with the aid of schematic diagrams. Advanced FGM fab أکثرFunctionally graded materials (FGMs) revealed an immense growth with worldwide demand. This paper describes a brief review of the feasibility of production methods (solid, liquid, and gaseous methods) chosen for FGMs, with the aid of schematic diagrams. Advanced FGM fabrication techniques such as additive manufacturing and laser deposition, which have been gaining importance are also explored. The evolution of fabrication techniques is correlated to the industrial requirements along with their merits and limitations. This review article also highlights some advanced engineering applications observed for FGMs. Comparing various fabrication technologies employed for FGMs, centrifugal casting was the most established and economically feasible method that met vast industrial product demands like hybrid and double-graded FGMs. Powder metallurgy was preferred for bulk gradation in spite of their sharp transitions across layers. Advanced FGM fabrication techniques like additive manufacturing, electrochemical gradation, and laser deposition techniques improved critical production parameters like precision, gradation control, etc. Thermal spraying successfully improved the heat insulation performance of FGMs. تفاصيل المقالة -
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2 - Investigation of Additive Manufacturing Process by LMD Method, Affecting Process Parameters on Microstructure and Quality of Deposition Layers
R Hedayatnejad H Sabet S Rahmati A Salemi GolezaniAdditive manufacturing (AM) is a general name used for production methods which have the capabilities of producing components directly from 3D computer aided design (CAD) data by adding material layer-by-layer until a final component is achieved. Included here are powde أکثرAdditive manufacturing (AM) is a general name used for production methods which have the capabilities of producing components directly from 3D computer aided design (CAD) data by adding material layer-by-layer until a final component is achieved. Included here are powder bed technologies, laminated object manufacturing and deposition technologies. These technologies are presently used for various applications in engineering industry as well as other areas of society, such as medicine, aerospace, architecture, cartography, entertainment. Laser metal deposition (LMD) using powder as an additive is an AM process which uses a multi-axis computer numerical control (CNC) machine to guide the laser beam and powder nozzle over the deposition surface. The component is built by depositing adjacent beads layer by layer until the component is completed. LMD has lately gained attention as a manufacturing method which can add features to semi-finished components or as a repair method. LMD introduce a low heat input compared to arc welding methods and is therefore well suited in applications where a low heat input is of an essence. For instance, in repair of sensitive parts where too much heating compromises the integrity of the part. It has been found that the most influential process parameters are the laser power density, scanning speed, powder feeding rate and powder standoff distance and that these parameters has a significant effect on the characteristics of the material such as microstructure تفاصيل المقالة -
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3 - Numerical simulation of multilayer cellular scaffolds with 3D and 1D elements
Hamid Reza khanaki Sadegh Rahmati Mohammad Nikkhoo Mohammad Haghpanahi Javad AkbariIn this paper, an attempt has been made to provide a numerical method for investigating the mechanical properties of multilayer scaffolding. These scaffolds can be used as implants in bone fractures. For this purpose two numerical simulation methods are introduced to pr أکثرIn this paper, an attempt has been made to provide a numerical method for investigating the mechanical properties of multilayer scaffolding. These scaffolds can be used as implants in bone fractures. For this purpose two numerical simulation methods are introduced to predict the elastic properties of multilayer cell scaffolds. These simulations are based on two models: a 3D model with a volumetric element, and a 1D model with a linear element. To compare the results of these models, three types of two- and three-layer titanium alloy scaffolds have been simulated by the two methods. Also, Young's modulus of the scaffolds has been compared with the experimental conclusions of earlier studies. The results confirm that simulations with 1D models are more cost-effective compared to 3D ones. Additionally, because of the more reliable agreement of Young's modulus results of numerical modeling with the linear element (1.8 to 5 times) compared to the volumetric element (11 to 23 times) compared to the experimental findings, the numerical method with the linear elements can be a reliable tool for studying multilayer scaffoldings. تفاصيل المقالة -
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4 - Investigation of Compressive Stresses of Stainless Steel 316L Diamond Lattice Structures Under the Effect of Spherical Connections Produced by SLM Additive Manufacturing
Behnam Ahmadi Roozbahani AliAkbar Lotfi NeyestanakIn this study, the compressive stresses of dodecahedron diamond lattice structures have been investigated. The finite element method has been used for Stress analysis. After the simulation, it was found that more stresses are applied at the junction of the struts of thi أکثرIn this study, the compressive stresses of dodecahedron diamond lattice structures have been investigated. The finite element method has been used for Stress analysis. After the simulation, it was found that more stresses are applied at the junction of the struts of this structure due to the application of compressive force. For this purpose, the connection point of the structure’s struts was strengthened by spherical connections, and a new type of dodecahedron structure was created. The validation and effect of spherical connections in compressive stresses have been evaluated experimentally. Two types of diamond lattice structures are made of stainless steel 316L by the SLM method. The results show that in the same condition, the use of spherical connections with twice the diameter of the structure’s struts helps to strengthen the structure and increase its compressive strength by 18% compared to the simple structure. تفاصيل المقالة -
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5 - Mechanical Properties of Materially and Geometrically Gradient Cellular Structures Manufactured with SLS 3D Printer Applicable as a Bone Implant
Ali Salehi Alireza Daneshmehr Kiyarash AminfarCellular structures are broadly used because of their exclusive properties in tissue engineering. This research proposes a new method, both in design and manufacturing, to engineer their mechanical properties considering gradient material and geometrical features and ev أکثرCellular structures are broadly used because of their exclusive properties in tissue engineering. This research proposes a new method, both in design and manufacturing, to engineer their mechanical properties considering gradient material and geometrical features and evaluate the possibility of using created structures as bone implants. Schwarz-primitive surface has been utilized to design cellular structures with different porosities and unit cell sizes. A total of 18 cellular structures were designed and fabricated using the SLS 3D printer with a new unconventional approach in adjusting the settings of the machine, and their mechanical properties were extracted. The structures' internal properties were evaluated using the FESEM. Comparing the mechanical compressive test results showed that adjustments in material and geometry improved mechanical properties (such as the compressive moduli, compressive strength, and yield strength). For instance, in 3 mm samples, the elastic modulus in material gradient and geometrical gradient structures is 20% and 73 % higher than the minimum values of the uniform structure. FESEM imaging revealed that adjusting the absorbed energy by powders (controlled by laser characteristics) leads to the formation of natural voids with diameters in the range of 6 to 144 μm for the gradient structures. Evaluation of the designed structures showed that 6 of them (4 uniform porosity and 2 geometrically gradient) have mechanical behavior of the desired tissue. The research outcomes can assist in optimizing manufactured parts by SLS 3D printers with internal and external controlled properties to obtain more desirable mechanical characteristics, especially for tissue engineering applications. تفاصيل المقالة -
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6 - Topological Optimization of Brake Pedal for Metal Additive Manufacturing: A Case Study
Batuhan Izgi Meltem Eryildiz Mirigül AltanAdditive Manufacturing (AM) has become popular for rapid prototyping and it is presently widely used in different branches of industry because of its advantages such as freedom of design, mass customization, waste minimization and the ability to manufacture complex shap أکثرAdditive Manufacturing (AM) has become popular for rapid prototyping and it is presently widely used in different branches of industry because of its advantages such as freedom of design, mass customization, waste minimization and the ability to manufacture complex shape. AM is the process of making 3D object from computer model data by depositing of material layer by layer. Topology optimization is iterative modifying the shape and optimizing material within a given designs space for load, boundary condition thus leading to weight reduction of components. Thus, to form lightweight components which have great advantage where energy consumption is minimal, topology optimization is used. Reducing weight and decreasing the material usage while keeping the product functions are the main challenges. Studies on the integration of the topology optimization and additive manufacturing, specifically mass reduction attract considerable attention. The topology optimization process is employed in this case study, to redesign a lightweight automotive brake pedal to show the potential of topology optimized design for additive manufacturing. As a result of this study 54.07% weight reduction was achieved in the total mass. The thermo- mechanical analysis for additive manufacturing showed that the part without topological optimization 108 MPa of stress and 1,099 mm of displacement were obtained and after optimization they were 196,1 MPa and 1,295 mm, respectively. تفاصيل المقالة -
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7 - Different Geometry Design Structures of Tissue Scaffolds for Additive Manufacturing
amirhossein Ehsani sadegh rahmati Mohammad Nikkhoo Shahram Etemadi Haghighi Mohammad HaghpanahiThe design and manufacturing cubic porous scaffolds are a considerable notion in tissue engineering (TE). From Additive manufacturing (AM) perspective, it has attained high appeal in the string of TE during the past decade. In the view of TE, the feasibility of manufact أکثرThe design and manufacturing cubic porous scaffolds are a considerable notion in tissue engineering (TE). From Additive manufacturing (AM) perspective, it has attained high appeal in the string of TE during the past decade. In the view of TE, the feasibility of manufacturing intricate porous scaffolds with high accuracy contrast to prominent producing methods has caused AM the outstanding option for manufacturing scaffold. From design perspective, porous scaffold structures play a crucial task in TE as scaffold design with an adequate geometries provide a route to required strength and porosity. The target of this paper is achieve of best geometry to become an optimum mechanical strength and porosity of TE scaffolds. Hence, the cubic geometry has been chosen for scaffold and Cube, Cylinder and Hexagonal prism geometries have been selected for pore of structures. In addition, for noticing the porosity effects, pore size has been chosen in three size, and a whole of nine scaffolds have been designed. Designed scaffolds were generated using Fused Deposition Modeling (FDM) 3D Printer and dimensional specifications of scaffolds were evaluated by comparing the designed scaffolds with Scanning Electron Microscope (SEM). The samples were subjected to mechanical compression test and the results were verified with the Finite Element Analysis (FEA). The results showed that firstly, as the porosity increases, the compressive strength and modulus of elasticity obviously decreased in all geometry pore scaffolds. Secondly, as the geometry changes in similar porosity, cubic pore scaffold achieved higher compressive strength and modulus of elasticity than cylinder and hexagonal prime. Experimental and FEM validated results proposed a privileged feasible pore geometry of cubic scaffold to be used in design and manufacturing of TE scaffolds. تفاصيل المقالة -
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8 - Feed Stock Fabrication of AISI 4605 Steel for Fused Deposition Modeling and Sintering and Designing of Its Extruder Mechanism
Amir Rahimi Jamal ZamaniFused Deposition Modeling and Sintering (FDMS) is one of the indirect and emerging processes of Additive Manufacturing (AM) for the production of metal parts, which is a combination of AM process and Metal Injection Molding (MIM). This study laboratory made a raw materi أکثرFused Deposition Modeling and Sintering (FDMS) is one of the indirect and emerging processes of Additive Manufacturing (AM) for the production of metal parts, which is a combination of AM process and Metal Injection Molding (MIM). This study laboratory made a raw material (Feed Stock) composing of high percentage of metal powder (particle in nano-scale) and polymeric materials; and then, designed an extruder to simulate melting and extruding process by Computational Fluid Dynamic (CFD). The different variables such as the nozzle diameter (D) of 1, 2, 3 and 4 mm and compression zone length (L2) of 100, 200 and 300 mm were simulated to investigate their impacts on flow rate and required torque to rotate screw. The findings showed that components of feed stock for high physical and mechanical properties of FDMS should account for 55 wt.% of paraffin wax, 25 wt.% of polypropylene, 15 wt.% of carnauba wax and 5 wt.% of stearic acid with optimum percentage of metal powder of 90 wt.%. Also, the optimum value of extruder diameter and compression zone length were 2mm and 200 mm, respectively. تفاصيل المقالة -
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9 - Investigating the Effect of Separation Speed and Image Cross-Section Geometry on The Separation Force in DLP Method using FEP and PP Polymer Membranes
Siavash Moayedi Manizani Jamal Zamani Mohammad Salehi Mohammad Taghi shayestehOne of the most challenging issues in DLP 3D printing is separation. Thus, the capability to employ a variety of polymer membranes can considerably aid in the development of the DLP technology. The primary purpose of this study is to thoroughly explore the characteristi أکثرOne of the most challenging issues in DLP 3D printing is separation. Thus, the capability to employ a variety of polymer membranes can considerably aid in the development of the DLP technology. The primary purpose of this study is to thoroughly explore the characteristics influencing separation force and time on the FEP industrial membrane and the proposed PP membrane. Therefore, the impact of image cross section geometry and separation speed on separation force and separation time is investigated. As a consequence, changing the percentage of surface porosity has a negligible effect on the amount of separation force. According to the findings, reducing the cross-sectional area by 1.36% reduced the separation force by 6.5 times. Moreover, the outcomes are consistent with the mathematical model given. the separation force rose by 230% in the FEP membrane with an increase of 96 times of the speed, whereas the separation time decreased by 18.8 times. For the proposed PP membrane, as the speed increases, the separation force rate increases by 175% and the separation time falls by 29.6 times. The aforementioned findings show that the PP film may be used as a practical and affordable solution with quick separation that can reduce printing time when producing three-dimensional lattice pieces at varying speeds. تفاصيل المقالة -
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10 - فناوری ساخت افزایشی فلزی: مروری برکاربرد های زیست پزشکی
شیدا اسمعیل زادهچاپ سه بعدی فلزی یک روش ساخت لایه لایه است که برای ساخت مدل سه بعدی ساختارهای پیچیده استفاده می شود. این فناوری دارای روش ها، مواد و تجهیزات متعدد است و بسیاری از هزینه های مرتبط با فرآیندهای سنتی، تجهیزات و مهارت های فلزکاری را کنار گذاشته تا با فرآیندی ساده تر و طراح أکثرچاپ سه بعدی فلزی یک روش ساخت لایه لایه است که برای ساخت مدل سه بعدی ساختارهای پیچیده استفاده می شود. این فناوری دارای روش ها، مواد و تجهیزات متعدد است و بسیاری از هزینه های مرتبط با فرآیندهای سنتی، تجهیزات و مهارت های فلزکاری را کنار گذاشته تا با فرآیندی ساده تر و طراحی خلاقانه تر ساخت نمونه را انجام دهد. چاپ سه بعدی به عنوان ساخت افزایشی نیز شناخته شده است. ویژگیهای ساخت افزایشی عبارتند از سفارشیسازی چاپ، هزینه پایین برای تولید نمونه، ارتباط مستقیم با تصویربرداری سهبعدی و امکان تولید نمونه با موادی که زیست سازگار و زیست تخریبپذیر هستند. چاپ سهبعدی در پیشرفت علوم زیست پزشکی بسیار موثر بوده و برای طیف گسترده ای از کاربردهای پزشکی از جمله ساخت انواع ایمپلنت های زیست سازگار با پاسخ مکانیکی مناسب، داربست های زیست تخریب پذیر با سرعت تخریب مهندسی شده، ابزارهای جراحی پزشکی، ابزارهای دندانپزشکی و تجهیزات پزشکی مناسب هستند. این مقاله به بررسی چاپ سه بعدی فلزی، مواد اولیه و روش های مرتبط با آن و کاربردهای زیست پزشکی این فناوری می پردازد. تفاصيل المقالة -
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11 - Fabrication of polycaprolactone and polylactic acid shapeless scaffolds via fused deposition modelling technology
Amirsalar Khandan Saeid EsmaeiliThe porous scaffold provides a temporary environment for bone growth and facilitates cell adhesion, cell growth and differentiation. In the present study, polymeric scaffolds were designed and fabricated via fused deposition modelling (FDM) method for orthopedic defect أکثرThe porous scaffold provides a temporary environment for bone growth and facilitates cell adhesion, cell growth and differentiation. In the present study, polymeric scaffolds were designed and fabricated via fused deposition modelling (FDM) method for orthopedic defect approaches using polycaprolactone (PCL) and polylactic acid (PLA) polymer. The prepared scaffold was coated with Chitosan-Hydroxyapatite (HA) as a reinforcement. The application of PLA, PCL and HA received attention of orthopedic surgeons to accelerate the bone healing. However, the comparison between the compression strength value of these scaffolds required more investigation and advance mechanical testing. In this study, we coat the novel PCL and PLA scaffold with chitosan-HA composite to mimic with humans' body. In the next stage, the mechanical strength and the biological response of the specimen were examined. Then, the morphology and phase characterization of the materials were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD) technique. The apatite formation and weight change test were performed on the porous scaffold which showed proper hydrophilicity. The microstructure of the porous scaffold was simulated using the Abaqus simulation with the extracted data from the experimental work. At the end, it was concluded that the most suitable scaffold was fabricated made of PLA filament and coated with chitosan-hydroxyapatite nanocomposite which can be useful choice for bone tissue engineering. تفاصيل المقالة -
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12 - Numerical Simulation of Homogeneous, Two and Three Lattice Layers Scaffolds with Constant Density
Hamid Khanaki Sadegh Rahmati Mohammad Nikkhoo Mohammad Haghpanahi Javad AkbariAdvances in the additive manufacturing technology have led to the production of complex microstructures with unprecedented accuracy and due todesigning an effective implant is a major scientific challenge in bone tissue regeneration and bone growth. In this research, ti أکثرAdvances in the additive manufacturing technology have led to the production of complex microstructures with unprecedented accuracy and due todesigning an effective implant is a major scientific challenge in bone tissue regeneration and bone growth. In this research, titanium alloy cylindrical scaffolds with three-dimensional architectures have been simulated and compared for curing partial bone deficiencies. The cylindrical networks in the scaffold (outer diameter 15 and length 30 millimeters) were designed in 36 different convergent, two-layer and three-layer types with 50% and 70% porosity. In all the samples, outer layers were denser than the inner layers. Mechanical characteristics of these scaffolds have been determined by simulating uniform compression load. The stress-strain curve of the samples showed that Young’s modulus and yield stress in the scaffolds with constant porosity were related to a unit-cell and the two-layer scaffolds, without changing Young’s modulus, had higher yield stress. This advantage was more significant in high-density scaffolds. تفاصيل المقالة -
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13 - The Recommend of Filler Metal to Increasing the Corrosion Resistance of Gas Pipeline
Esmaeil Jafari Mohammad Sadegh KarimiThe high strength carbon steels such as API X65 is widely used to build the pipelines. In this study, the corrosion behavior welds region of the gas pipeline was studied. For this purpose, Shield Metal Arc Welding (SMAW) was used to evaluate the proposed method. The wel أکثرThe high strength carbon steels such as API X65 is widely used to build the pipelines. In this study, the corrosion behavior welds region of the gas pipeline was studied. For this purpose, Shield Metal Arc Welding (SMAW) was used to evaluate the proposed method. The welding processes were performed with E6010, E6013, and ER70S-6 electrodes as filler metal and welding carried out in 3 passes by a single butt welded method. The corrosion behavior was determined in the gas fluid solution at environment temperature using potentiodynamic polarization test. The microstructure of the base metal, weld zone, and heat-affected zone were investigated with optical microscopy. Results show that the microstructure changes that formed during the welding process were correlated with electrochemical results. And the corrosion performance of the weld joints was influenced by the type of filler metal. As the welded sample with ER70S-6 has high corrosion resistance in comparison to other electrodes. تفاصيل المقالة -
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14 - تأثیر عملیات حرارتی بر ریزساختار، خواص مکانیکی و رفتار خوردگی قطعات فولاد زنگ نزن دو فازی 2209 تولید شده توسط روش تولید افزودنی مبتنی بر سیم و قوس الکتریک
علی ملازاده کشکوئی محمود شریفی تبار مهدی شفیعی آفارانیدر این پژوهش به ساخت دیواره فولاد زنگ نزن دوفازی توسط فرآیند تولید افزودنی مبتنی بر سیم و قوس و بررسی ساختار، ریزساختار، خواص مکانیکی و خوردگی آن پرداخته شده است. نتایج آنالیز پراش اشعه ایکس وجود فازهای فریت و آستنیت در ساختار را نشان داد. بررسی های ریزساختاری نشان دهند أکثردر این پژوهش به ساخت دیواره فولاد زنگ نزن دوفازی توسط فرآیند تولید افزودنی مبتنی بر سیم و قوس و بررسی ساختار، ریزساختار، خواص مکانیکی و خوردگی آن پرداخته شده است. نتایج آنالیز پراش اشعه ایکس وجود فازهای فریت و آستنیت در ساختار را نشان داد. بررسی های ریزساختاری نشان دهنده توزیع غیریکنواخت فازهای فریت و آستنیت در ریزساختار نمونه پس از تولید بود. جهت بررسی خواص مکانیکی دیواره از آزمون کشش و آزمون میکروسختی در مناطق مختلف دیواره استفاده شد. بر اساس نتایج این آزمون ها، مقدار میانگین استحکام تسلیم و استحکام کششی در راستای جوشکاری به ترتیب در حدود 7/2 و 5/5 درصد بیشتر و مقدار قابلیت تغییر طول در حدود 5/4 درصد کمتر از راستای رسوب گذاری بود. عملیات حرارتی پس از تولید در دمای 1000 درجه سلسیوس به مدت 30 دقیقه موجب ریز شدن دانههای فریت و آستنیت، هم محور شدن ساختار، افزایش درصد آستنیت و بهبود میزان سختی ویکرز از مقدار میانگین 318 به 376 شد. سطح شکست تمامی نمونهها حاکی از مکانیزم شکست نرم بود. نتایج آزمون خوردگی نشان داد که عملیات حرارتی موجب افزایش مقاومت به خوردگی فولاد شد. تفاصيل المقالة -
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15 - تأثیر عملیات حرارتی بر خواص مکانیکی، ساختار انجمادی و جدایش آلیاژ اینکونل 625 در فرایند ساخت افزایشی به روش DLMD
محمد گواهیان جهرمی رضا شجاع رضوی حامد نادری سامانی فرید کرمانییکی از فرایندهای بازسازی و ساخت قطعات، رسوبنشانی مستقیم فلزی لیزری است. در این روش بررسی شرایط ذوب توسط لیزر و انجماد آلیاژ بسیار حائز اهمیت است. هدف از این پژوهش بررسی تأثیر پارامترهای اصلی رسوبنشانی روی ریزساختار، فاصله بازوهای دندریتی و جدایش عناصر آلیاژی و همچنین أکثریکی از فرایندهای بازسازی و ساخت قطعات، رسوبنشانی مستقیم فلزی لیزری است. در این روش بررسی شرایط ذوب توسط لیزر و انجماد آلیاژ بسیار حائز اهمیت است. هدف از این پژوهش بررسی تأثیر پارامترهای اصلی رسوبنشانی روی ریزساختار، فاصله بازوهای دندریتی و جدایش عناصر آلیاژی و همچنین ارزیابی خواص مکانیکی اینکونل 625 است. با توجه به بررسی تصویر میکروسکوپی الکترونی روبشی، با حرکت از فصل مشترک به سمت بالای روکش با کاهش نسبت G/R ساختار انجمادی از دندریتی ستونی به دندریتی هممحور تغییر یافت. از فصل مشترک به سمت سطح نمونه نرخ سردشدن افزایش و فاصله بین بازوهای دندریتی کاهش یافت. همچنین با دور شدن از فصل مشترک فاصله بازوی دندریتی افزایش مییابد. با تغییر توان لیزر از 250 به 450 وات نسبت G/R از ℃/〖mm〗^2 08/1252به ℃/〖mm〗^2 34/970کاهش یافت. انجام عملیات حرارتی منجر به یکنواختی عناصر آلیاژی در فاز زمینه شد؛ همچنین با انجام عملیات حرارتی استحکام کششی و ازدیاد طول افزایش و استحکام تسلیم کاهشیافت. تفاصيل المقالة -
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16 - Investigation of additive manufacturing of porous Ti-6Al-4V alloy: Geometry analysis for dental applications
Mohammad Hossein Malekipour Esfahani Fatemeh Safdarian Sharif HeydariThis research is dedicated to reviewing porous titanium alloy structures suitable for biomedical applications. The mechanical properties of porous samples with different structures and porosity were reviewed through a static compression test to identify the type of suit أکثرThis research is dedicated to reviewing porous titanium alloy structures suitable for biomedical applications. The mechanical properties of porous samples with different structures and porosity were reviewed through a static compression test to identify the type of suitable structure. In addition, high porosity is desirable due to the growth of bone tissue in the internal microstructure of the porous bony implant. Samples are normally fabricated made of Ti-6Al-4V alloy and stainless steel using selective laser melting (SLM) as an additive manufacturing process. The samples were prepared with a pore size (200, 400, and 600 µm) and cubic and trabecular topology. The actual weight of all samples was determined, which is important in identifying other characteristics. All the tested samples reached the optimal values of maximum stress and tensile strength. The most appropriate mechanical properties were observed for samples with a pore diameter of 200 μm and a cubic structure. The implants with porosity, pore size, and pore interconnectivity affect the differentiation of bone tissue. تفاصيل المقالة -
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17 - بررسی اثر میزان تخلخل بر انتقال حرارت در قالبهای تزریق پلاستیک ایجادشده به روش ذوب لیزر انتخابی
سید مصطفی میرطبایی افشین جودکی مرتضی طاهرنیاامکان ساخت هندسه پیچیده کانالهای خنککننده منسجم، با روشهای معمول ماشینکاری مقدور نیست، بنابراین با استفاده از فرآیندهای ساخت افزایشی مانند فرآیند ذوب لیزر انتخابی امکان ایجاد کانالها در قالب فراهم میشود. قطعات ایجاد شده به روش ذوب لیزر انتخابی همواره با تخلخل موا أکثرامکان ساخت هندسه پیچیده کانالهای خنککننده منسجم، با روشهای معمول ماشینکاری مقدور نیست، بنابراین با استفاده از فرآیندهای ساخت افزایشی مانند فرآیند ذوب لیزر انتخابی امکان ایجاد کانالها در قالب فراهم میشود. قطعات ایجاد شده به روش ذوب لیزر انتخابی همواره با تخلخل مواجه هستند،که این مقدار تخلخل وابسته به پارامترهای فرآیند متغیر میباشد، از سوی دیگر توانایی ساخت مواد متخلخل توسط فرآیند ذوب لیزر انتخابی باعث شده است این مواد با توجه به خصوصیاتی نظیر چگالی کمتر و انتقال حرارت بهتر در صنایع هوا فضا، خودرو، مصارف پزشکی و مبدلهای حرارتی نظر محققان را جلب کند و با توجه به این¬که تخلخل علاوه بر تاثیر مستقیم بر روی خواص مکانیکی بر روی انتقال حرارت تاثیر میگذارد. در این پژوهش به بررسی اثر تخلخل بر انتقال حرارت در قالب پرداخته شد، ابتدا مدل و قالب طراحی شده است و بهمنظور بررسی اثر تخلخل چهار مدل شبیهسازی با درصد تخلخلهای حجمی 0، 10، 20و30 در نرمافزار انجام و تحلیل گردید. بررسی و تحلیل نتایج نشان میدهد افزایش درصد تخلخل در قالب سبب افزایش سریعتر دما در قالب میشود. علاوه بر آن با افزایش درصد تخلخل در قالب نرخ کاهش دما در قالب بیشتر میشود و عملیات خنک کاری قطعه سریعتر رخ میدهد. بررسی نتایج بیشینه گرادیان حرارتی ماده بدون تخلخل در مقایسه با ماده 30 درصد تخلخل، افزایش 21درصدی گرادیان حرارتی در ماده متخلخل را نشان داده است. علاوه بر آن بیشینه شار حرارتی ماده بدون تخلخل در مقایسه با ماده 30 درصد تخلخل، کاهش22 درصدی شار حرارتی در ماده متخلخل را نتیجه داده است. تفاصيل المقالة
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