Lecture 2 Mechanical Engineering PDF

Mechanical Engineering Assoc. Prof. Tahany William Sadak Production Engineering and Design Department Faculty of Engineering, Beni–Suef University, Beni–Suef, Egypt.  Mechanical Engineering MTE102 Course content 1- Introduction in Mechanical Eng...

Mechanical Engineering Assoc. Prof. Tahany William Sadak Production Engineering and Design Department Faculty of Engineering, Beni–Suef University, Beni–Suef, Egypt.  Mechanical Engineering MTE102 Course content 1- Introduction in Mechanical Engineering. Materials engineering and fundamentals of mechanical engineering,  Mechanical properties and specifications of materials Crystal structure of metals and alloys mechanical testing of metallic materials electrical properties of materials polymer materials  composite materials  Materials Science and Technology MTE103 Credit Hours: 4 (3+2+2)Prerequisite: BAS002 Course content 1- Introduction in Mechanical Engineering. Materials engineering and fundamentals of mechanical engineering,  Mechanical properties and specifications of materials Crystal structure of metals and alloys mechanical testing of metallic materials electrical properties of materials polymer materials  composite materials ‫هندسة المواد وأساسيات الهندسة الميكانيكية‬ ‫‪‬‬ ‫الخواص الميكانيكية للمواد ومواصفاتها‬ ‫‪‬‬ ‫التركيب البللورى للمعادن والسبائك‬ ‫‪‬‬ ‫االختبارات الميكانيكية للمواد المعدنية‬ ‫‪‬‬ ‫الخواص الكهربية للمواد‬ ‫‪‬‬ ‫مواد البووليمر‬ ‫‪‬‬ ‫المواد المركبة‬ ‫‪‬‬ Processing Structure Properties Performance Recyclability The five components of the discipline of materials science and engineering and their interrelationship.  Metals Metals are composed of onecarbon, nitrogen, oxygen) in or more metallic elementsrelatively small amounts.9 (e.g., iron, aluminum,Atoms in metals and their copper, titanium, gold,alloys are arranged in a nickel), and often also nonmetallic elements.  Selection of Materials for Engineering Purposes 1. Availability of the materials, 2. Suitability of the materials for the working conditions in Copper Aluminium Zinc service, and 3. The cost of the materials. Iron Lead  Ceramics Ceramics are compounds between metallic and nonmetallic elements oxides, nitrides, and carbides. For example, common ceramic materials include aluminum oxide (or alumina, Al2O3), silicon dioxide (or silica, SiO2), silicon carbide (SiC), silicon nitride (Si3N4), and, in addition, what some refer to as the traditional ceramics—those composed of clay minerals (e.g., porcelain), as well as cement and glass.  Polymers Polymers include the familiar plastic and rubber materials. Many of them are organic compounds that are chemically based on carbon, hydrogen, and other nonmetallic elements (i.e., O, N, and Si). Some common and familiar polymers are polyethylene (PE), nylon, poly(vinyl chloride) (PVC), polycarbonate (PC), polystyrene (PS), and silicone rubber. Smart Materials Materials that perform a change in their properties (i.e. mechanical, chemical, thermal etc.) as a response to an external stimulus (photochromic materials, shape memory materials and phase change materials); materials that transform an energy input into an another energy form (i.e. photovoltaic and piezoelectric materials).  Nanomaterials The dimensions of these structural entities are on the order of a nanometer (10−9) less than 100 nanometers (nm; equivalent to the diameter of approximately 500 atoms).  Main mechanical properties Elasticity: It is the ability of the material to restore its original dimensions, i.e. no permanent shape remains after the effective load is removed..‫هي قدرة المادة على استعادة أبعادها األصلية أي عدم بقاء تشكل دائم بعد زوال الحمل المؤثر‬Elasticity: ‫ المرونة‬-1 2- Plasticity: It is the ability of the material to have a permanent shape, i.e. the material does not restore its original dimensions after the effective load is removed..‫هي قدرة المادة على أن يكون لها تشكل دائم أي ال تسترجع المادة أبعادها األصلية بعد إزالة الحمل المؤثر‬Plasticity ‫ اللدونة‬-2  3- Ductility: It can be defined as the property that allows the material to undergo a large plastic change under the influence of tensile load, i.e. the ability of the material to pull and its ability to elongate greatly when exposed to tensile load ‫يمكن تعريفها بأنها الخاصية التي تسح للمادة بتغير لدن كبير تحت تأثير حمل الشد أي قدرة‬Ductility : ‫ المطيلية‬-3.‫المادة على السحب و قابليتها لالستطالة الكبيرة عند تعرضها لحمل الشد‬ 4- Brittleness: It is the property that makes the material break before a noticeable change in shape. Ductile is the opposite of brittleness. Ductile materials have a large plasticity when subjected to tensile load, such as copper, while brittle materials break before any change in shape occurs when loaded, such as glass and cast iron ‫ فالممطولية هي عكس القصافة فالمواد المطيلة لها‬.‫هي الخاصية التي تجعل المادة تنكسر قبل تغير ملحوظ في الشكل‬Brittleness : ‫ الهشاشة‬-4 ‫تشكل لدن كبير عند تعرضها لحمل الشد مثل النحاس أما المواد القصفة فتنكسر قبل أن يطرأ عليها أي تغير في الشكل عند التحميل مثل الزجاج و‬.‫حديد الزهر‬  5- Malleability is the ability of a material to undergo large plastic changes under compressive load, i.e. the ability of the material to flatten when hammered without breaking. Malleability is a property similar to ductility, but the load in ductility is tension, while in malleability it is in the case of compression. ‫هي قدرة المادة على أن يحدث لها تغيرات لدنة كبيرة تحت حمل الضغط أي قدرة المادة على التفلطح‬Malleability ‫ الطروقية‬-5.‫ الطروقية خاصية تشبه الممطولية لكن التحميل في الممطولية هو الشد أما في الطروقية فهو في حالة الضغط‬.‫بالطرق دون حدوث كسر‬ 6- Strength: It is the resistance of the material to any effective load, and the resistance to tension if the effective load is a tensile load and the resistance to bending if the load is a bending load. ‫ و المقاومة للشد إذا كان الحمل المؤثر حمل الشد والمقاومة لالنحناء إذا‬،‫هي مقاومة المادة ألي حمل مؤثر‬Strength: ‫ المقاومة‬-6..‫كان الحمل حمل االنحناء‬  Chapter 2 Atomic Structure and Interatomic Bonding FUNDAMENTAL CONCEPTS Each atom consists of a very small nucleus composed of protons and neutrons and is encircled by moving electrons. Both electrons and protons −19 are electrically charged, the charge magnitude being 1.602 × 10 C protons and neutrons have approximately the same −27 mass, 1.67 × 10 kg, which is significantly larger than −31 that of an electron, 9.11 × 10 kg  Atomic number (Z). The atomic number equals the number of electrons This atomic number ranges in integral units from 1 for hydrogen to 92 for uranium,  The atomic mass (A) of a specific atom may be expressed as the sum of the masses of protons and neutrons within the nucleus ‫( لذرة معينة هى مجموع كتل البروتونات والنيوترونات داخل النواة‬A) ‫الكتلة الذرية‬ the number of protons is the same for all atoms of a given element, the number of neutrons (N) may be variable Thus atoms of some elements have two or more different atomic masses, which are called isotopes. A ≅ Z + N 23 6.022 × 10 (Avogadro’s number)  1 amu/atom (or molecule) = 1 g/mol For example, the atomic weight of iron is 55.85 amu/atom, or 55.85 g/mol.  Quantum mechanics One early outgrowth of quantum mechanics was the simplified Bohr atomic model, in which electrons are assumed to revolve around the atomic nucleus in discrete orbitals, and the position of any particular electron is more or less well defined in terms of its orbital. This model of the atom is represented in Figure 2.1. Figure 2.1 Schematic representation of the Bohr atom a wave-mechanical model  Comparison of the (a) Bohr and (b) wave mechanical atom models in terms of electron distribution a wave-mechanical model, in which the electron is Bohr model was eventually considered to exhibit both found to have some significant wave like and particle-like limitations because of characteristics its inability to explain several phenomena involving electrons ‫وقد تم التوصل إلى حل باستخدام نموذج‬ ‫نموذج بور هذا يعاني من بعض القيود المهمة‬ ‫ حيث يُنظر إلى اإللكترون‬،‫ميكانيكي موجي‬ ‫بسبب عدم قدرته على تفسير العديد من‬ ‫على أنه يُظهر خصائص تشبه الموجة‬.‫الظواهر التي تنطوي على اإللكترونات‬ ‫والجسيمات‬ Any Question Any Question