Functionally graded materials موضوع علمي جميل ومتجدد

المصدر: Functionally graded materials موضوع علمي جميل ومتجدد
في منتدى : العلوم العامة والبرامج العلمية

Functionally graded materials
Functionally graded materials (FGM's) are a new generation of engineered materials wherein the microstructural details are spatially varied through non-uniform distribution of the reinforcement phase(s), see the figure.
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FGM's is accomplished using reinforcements with different properties, sizes, and shapes, as well as by interchanging the roles of the reinforcement and matrix phases in a continuous manner.
The result is a microstructure that produces continuously or discretely changing thermal and mechanical properties at the macroscopic or continuum scale.
This new concept ofmaterial's microstructureallows, for the first time, to fully integrate the material and structural considerations into the final design of structural components.
Functionally graded materials are ideal for applications involving severe thermal gradients, ranging from thermal structures in advanced aircraft and aerospace engines to computer circuit boards.
The technologically important applications illustrate the utility of functionally graded microstructures in tailoring the response of structural components in a variety of applications involving uniform and gradient thermomechanical loading and biomaterials applications.
Owing to the many variables that control the design of functionally graded microstructures, full exploitation of the FGM's potential requires the development of appropriate modeling strategies for their response to combined thermomechanical loads.​

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Examples of different types of functionally graded microstructures​

Potential applications of FGM's are both diverse and numerous, e.g., FGM sensors and actuators, FGM metal-ceramic armor, FGM thin-walled rotating blades, FGM photo-detectors and FGM dental implant.

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The cross-section of hydroxyl-apatite-glass-titanium functionally graded composite.

Medical application (FGM synthetic Bone)​

 

جزاكم الله كل خير أخي العزيز ... اتمنى من الإخوة ذوي الإختصاص أن تكون لهم مشاركات فعالة في هذا الموضوع القيم ...

 

جزاكم الله خيراً دكتورنا العزيز د./ سعد
موضوع مفيد جداً وجديد
بارك الله فيكم
واسمح لي بهذه الاضافة (مقتبسة من أحد المواقع)​

A functionally graded material (FGM) is a two-component composite characterised by a compositional gradient from one component to the other. In contrast, traditional composites are homogeneous mixtures, and they therefore involve a compromise between the desirable properties of the component materials. Since significant proportions of an FGM contain the pure form of each component, the need for compromise is eliminated. The properties of both components can be fully utilised. For example, the toughness of a metal can be mated with the refractoriness of a ceramic, without any compromise in the toughness of the metal side or the refractoriness of the ceramic side.

Potential Applications of FGMs​

FGMs offer great promise in applications where the operating conditions are severe. For example, wear-resistant linings for handling large heavy abrasive ore particles, rocket heat shields, heat exchanger tubes, thermoelectric generators, heat-engine components, plasma facings for fusion reactors, and electrically insulating metal/ceramic joints. They are also ideal for minimising thermomechanical mismatch in metal-ceramic bonding.

The Origin of FGMs​

The FGM concept originated in Japan in 1984 during the spaceplane project, in the form of a proposed thermal barrier material capable of withstanding a surface temperature of 2000 K and a temperature gradient of 1000 K across a cross section <10 mm. Since 1984, FGM thin films have been comprehensively researched, and are almost a commercial reality.

Bulk FGMs​

However, most of the “extreme environment” applications for FGMs require bulk FGMs, i.e., FGMs with gradient breadth in the order of millimeters to centimeters, and with continuous gradient profiles. Bulk FGMs remain merely a hypothesis. No commercially viable process has yet been developed to make such a material. While the scientific literature abounds in papers on the modeling of the hypothetical properties of bulk FGMs, the few proposed fabrication methods are labour-intensive specialised laboratory techniques, not low-cost commercial processes.

Wear Resistant FGMs​

A low-cost ceramic-metal functionally graded material would be ideal for wear-resistant linings in the mineral processing industry. Such a material would comprise a hard ceramic face on the exposed side, a tough metal face on the rear side that can be bolted or welded to a support frame, and a graded composition from metal to ceramic in between. The gradation would enhance the toughness of the ceramic face and also prevent ceramic-metal debonding. Such a material would uniquely combine the following attributes:
· High abrasion resistance (ceramic face)
· High impact resistance
· Convenience: weldable/boltable to metal supports
There would be little point in developing such a material unless it could compete commercially with the wear-resistant ceramics currently on the market, which range from tens to hundreds of dollars per kilogram, with alumina at the bottom end and imported tungsten carbide at the top end of this range. Unless this can be achieved, the potential benefits of bulk wear-resistant tiles of metal-ceramic FGMs will remain an unrealised possibility.

The Impeller Dry Blending (IDB) Process​

To this end, a controlled-blending process has been developed at Sydney University for the fabrication of functionally graded materials of broad regular gradient. This is known as the impeller dry blending process (IDB). The IDB process is characterised by the following features:
· Low-cost process.
· Rapid throughput rates (hundreds of grams per minute).
· Broad gradients millimetres to centimetres in breadth.
· Regular and continuous (not layered) gradients are achievable with a high level of control over gradient profile.

What is Unique About IDB?

Controlled Segregation​

A number of laboratory reports have been published on fabrication processes for bulk FGMs. These approaches have mostly involved some sort of controlled segregation approach, i.e., separating a mixture of metal and ceramic powders into a graded profile on the basis of density. In controlled segregation, the driving force for gradation is the action of gravity on the difference in true density of the component powders. Segregation is a slow process with poor gradient control because segregation rates depend strongly on the particle size and morphology of the specific raw materials used. To date, most published papers on bulk FGMs have involved a segregation approach, for example, sedimentation forming, slip casting, centrifugal casting, and thixotropic casting.

Controlled Blending​

In controlled blending, the two FGM components are blended during forming and the ratio is continuously varied from 100% component 1 through to 100% component 2 (or variation thereof). This approach potentially offers the unique advantage of being able to produce precisely controllable regular functional gradients independent of the system-inherent issues of powder density and gravitational settling mechanisms. Also, unlike segregation, controlled blending enables very rapid processing rates.

Use of Controlled Blending​

To date, controlled-blending has mostly been used for making FGM thin films. For example, FGM thin films by thermal spraying (blended powder feed), vapour deposition (CVD/PVD blended gas feed), electrophoretic deposition (blended slurries), filter pressing (blended slurries), and blended spray drying.​

:gift:​

 

شكراً لك أخي د. سعد على الموضوع
عذراً لم أستطع المشاركة بالأمس حيث كان المنتدى تحت الصيانة
موضوع جميل ذكرني بموضوع النانو - ولكن الخواص هنا لا تتغير
أتمنى مشاركة ذوي الاختصاص

 

شكرا جزيلا أخي أحمد على هذه الأضافة الجميلة،
انشاءالله تستمر المشاركات في هذا الموضوع
تحياتي وتقدير

 

شكرا جزيلا على المرور الكريم أخي ابو عمر
اتمنى ان تستقطب هذه المواضيع اعضاء جدد
تحياتي وتقديري

 

جزاك الله خيرا اخي د. سعد موضوع ممتع بحق
لكن عندي سؤال حول المعادلة التفاضلية حول non-uniform distribution
اذا موجودة عندك ممكن تضعها بارك الله فيك

 

موضوع جميل وشيق
جزاك الله كل خير
======

 

ما أسعدني بوجودك في هذا الموضوع أخي ابن الخطاب
في الحقيقة كان يوجد صور مع الموضوع وننتظر اكتمال نقل ملفات المنتدى الى السيرفر الجديد لان سؤالك تشرحه الصورة التي تليه مباشرة، سانتظر بضعة ايام واذا لم تتواجد اصور سارفعها مرة اخرى،
ولكني استغل الفرصة في توضيح اضافي:-
بدأت الفكرة مع المهندسين اليابانيين بسبب استخدامهم مواد مؤلفة صفائحية laminate composite في تغليف جناح طائرة والمشكلة ان الفرق في التمدد الحراري بين الصفائح من مواد مختلفة ادى الى انفصال الصفائح عن بعضها، فتم التفكير بالمواد المتدرجة المحتوى graded materials لعبور المشكلة المذكورة.
ولكن الفكرة تطورت الى مواد متدرجة بالمتانة، ثم العزل الكهربائي، وكذلك التدرج من الموائمة البيولوجية الى القوة الميكانيكية (كما يفترض ان تبينها الصورة الأخيرة) وهكذا تطبيقات.
اما التدرج (التفاضل) فيكون فعلا مرسوما على شكل معادلة ولكل حالة وتطبيق له فرضيته ومعادلته الخاصة حسب البحث العلمي
اما التدرج بحد ذاته فقد بدأ على مستوى الدقائق وتطور الى البنية المجهرية وحتى وصل في سنة 2009 الى تدرج على المستوى الذري او الجزيئي من خلال تقنية sputtering. وحاليا طالب دكتوراه عراقي يقوم بهذا في المانيا لكن داهمه مرض سرطان الدم ونتمنى له الشفاء العاجل واكمال بحثه،
ندعو سويا من الله عز وجل رفع الغمة عن هذه الأمة
تحياتي لك أخي العزيز

 

شكرا على مرورك الكريم أخي عمر،
اريدك ان تسلم على اصدقائي في جامعة صلاح الدين الذين تعرفهم، وكذلك طالبتي التي تخرجت وكنت مشرفا على بحثها للدكتوراه في كلية العلوم

 

ممنون لمرورك صديقي العزيز،
وفقك الله لكل خير

 

شكرا أخي عمر على تشجيعك المستمر
سلامي وشكري لـــك وللاخ megypt وللاخ الزعيم الأول وللاخ DNA PROFESSOR

 

شكرا أخي العزيز د.العراقي
مشتاقين لك ولمشاركاتك

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