EE2EM Engineering Materials Lecture 1 -- Introduction PDF

EE2EM Engineering Materials Lecture 1 --Introduction Dr Mohammed Honnur vali, PhD, CEng, IntePE Faculty of Engineering and Technology Muscat University [email protected] 1 Module Specifications 2 Module Specifica...

EE2EM Engineering Materials Lecture 1 --Introduction Dr Mohammed Honnur vali, PhD, CEng, IntePE Faculty of Engineering and Technology Muscat University [email protected] 1 Module Specifications 2 Module Specifications Why materials? ✓ Please take a few moments and reflect on what your life would be like without all of the materials that exist in our modern world. ✓ Believe it or not, without these materials we wouldn’t have automobiles, cell phones, the internet, airplanes, nice homes and their furnishings, stylish clothes, nutritious (also “junk”) food, refrigerators, televisions, computers... (and the list goes on). ✓ Virtually every segment of our everyday lives is influenced to one degree or another by materials. ✓ In fact, early civilizations have been designated by the level of their materials development ✓ 1. Stone Age, ✓ 2. Bronze Age, ✓ 3. Iron Age ----Now? Silicon Age? Polymer Age? Materials discipline ✓ Sometimes it is useful to subdivide the discipline of materials into materials science and materials engineering subdisciplines. ✓ Materials science involves investigating the relationships that exist between the structures and properties of materials (i.e., why materials have their properties). ✓ In contrast, materials engineering involves, on the basis of these structure–property correlations, designing or engineering the structure of a material to produce a predetermined set of properties. ✓ From a functional perspective, the role of a materials scientist is to develop or synthesize new materials. whereas a materials engineer is called upon to create new products or systems using existing materials and/or to develop techniques for processing materials. ✓ What is a structure of a material? In short, structure of a material usually relates to the arrangement of its internal components. Iron material in raw shape Iron engineered to a specific shape and structure  Materials discipline Structural elements may be classified on the basis of size and in this regard, there are several levels: Subatomic structure—involves electrons within the individual atoms, their energies and interactions with the nuclei. Atomic structure—relates to the organization of atoms to yield molecules or crystals. Nanostructure—deals with aggregates of atoms that form Atomic structure particles (nanoparticles) that have nanoscale dimensions (less that about 100 nm). Microstructure—those structural elements that are subject to direct observation using some type of microscope (structural features having dimensions between 100 nm and several millimeters). Macrostructure—structural elements that may be viewed with Molecular structure the naked eye (with scale range between several millimeters and on the order of a meter). Macro structure view of iron Microstructure view of iron Nano structure  Materials property and their classification ✓ A property is a material trait in terms of the kind and magnitude of response to a specific imposed stimulus. ✓ Generally, all important properties of solid materials may be grouped into six different categories: mechanical, electrical, thermal, magnetic, optical, and deteriorative. ✓ Mechanical properties—relate deformation to an applied load or force; examples include elastic modulus (stiffness), strength, and resistance to fracture. ✓ Electrical properties—the stimulus is an applied electric field; typical properties include electrical conductivity and dielectric constant. ✓ Thermal properties—are related to changes in temperature or temperature gradients across a material; examples of thermal behavior include thermal expansion and heat capacity. Mechanical properties Electrical properties Thermal properties  Materials property and their classification Magnetic properties—the responses of a material to the application of a magnetic field; common magnetic properties include magnetic susceptibility and magnetization. Optical properties—the stimulus is electromagnetic or light radiation; index of refraction and reflectivity are representative optical properties. Deteriorative characteristics—relate to the chemical reactivity of materials; for example, corrosion resistance of metals. Magnetic properties Light transmission properties Corrosion of iron Material Paradigm ✓ In addition to structure and properties, two other important components are involved in the science and engineering of materials—namely, processing and performance. ✓ With regard to the relationships of these four components, the structure of a material depends on how it is processed. ✓ Furthermore, a material’s performance is a function of its properties. Four components of the materials science and Engineering  Material Paradigm--Example ✓ All these specimens are of the same material, aluminum oxide. ✓ The leftmost one is what we call a single crystal—that is, has a high degree of perfection—which gives rise to its transparency. ✓ The center one is composed of numerous and very small single crystals that are all connected; allow the light to scatter lightly, Which makes the material optically translucent. ✓ Finally, the material on the right consists of many small interconnected crystals making the crystal appear solid and scatter the reflected light at a higher rate thus making the material opaque. ✓ Thus, the structures of these three specimens are different in terms of crystal boundaries and pores, which affect the optical Example transmittance properties. ✓ Furthermore, each material was produced using a different processing technique.  Case study 1 ✓ During World War II, 2,710 Liberty cargo ships were mass-produced by the United States to supply food and materials to the combatants in Europe. ✓ The fracture you are observing is due to brittle fracture rather ductile. ✓ Some of the ships experienced cracks in their ducks and hull. ✓ Three of them catastrophically split in half when cracks formed, grew to critical lengths, and then rapidly propagated completely around the ships’ girths. (See the figure) ✓ What did the investigations tell? 1) When some normally ductile metal alloys are cooled to relatively low temperatures, they become susceptible to brittle fractures. The Liberty ship S.S. Schenectady, which, in 1943, failed 2) Welding of the steel frames were done rather than before leaving the shipyard using riveting method for faster production.  Case study 1 Remedial measures taken to correct these problems included the following: ✓Lowering the ductile-to-brittle temperature of the steel to an acceptable level by improving steel quality (e.g., reducing sulfur and phosphorus impurity contents) ✓ Installing crack-arresting devices such as riveted straps and strong weld seams to stop propagating cracks. ✓Improving welding practices and establishing welding code.  CLASSIFICATION OF MATERIALS Solid materials have been conveniently grouped into three basic categories: (based primarily on chemical makeup and atomic structure) metals, ceramics, and polymers, In addition, there are the composites that are engineered combinations of two or more different materials. Metals ✓ Metals are composed of one or more metallic elements (e.g., iron, aluminium, copper, titanium, gold, nickel), Bar chart of room temperature density values for various metals, ceramics, polymers, and composite ✓ and often also non-metallic elements (e.g., carbon, nitrogen, materials. oxygen) in relatively small amounts. ✓ Atoms in metals and their alloys are arranged in a very orderly manner and are relatively dense in comparison to the ceramics and polymers.  mechanical characteristics stiff and strength Familiar objects made of metals and metal alloys (from left to right): silverware (fork and knife), scissors, coins, a gear, a wedding ring, and a nut and bolt. Bar chart of room temperature stiffness (i.e., elastic modulus) values for various metals, ceramics, polymers, and composite materials. ✓ It can be observed that the metals, ceramics and composites have higher stiffness than the polymers.  mechanical characteristics stiff and strength ✓ It can be observed that the strength of metal and composites comparatively have higher tensile strength than ceramics and polymers. ✓ Metals show high resistance to fracture and that why is they are widely used in structural applications. ✓ Similarly, Metallic materials have large numbers of nonlocalized electrons—that is, these electrons are not bound to particular atoms. (free to move) ✓ As a result they are good conductors of electricity and heat too. ✓ They are not transparent to visible light (i.e. a polished metal surface has a lustrous Bar chart of room temperature strength (i.e., tensile strength) values for various appearance). metals, ceramics, polymers, and composite materials. ✓ In addition, some of the metals (i.e., Fe, Co, and Ni) have desirable magnetic properties.  CLASSIFICATION OF MATERIALS Ceramics ✓ Ceramics are compounds between metallic and non-metallic elements; they are most frequently oxides, nitrides, and carbides. ✓ For example, common ceramic materials include aluminium oxide (or alumina, 𝐴𝐼2 𝑂3 ), silicon dioxide (or silica, 𝑆𝑖𝑂2 ), silicon carbide (SiC), silicon nitride (𝑆𝑖3 𝑁4 ). ✓ In addition, what some refer to as the traditional ceramics—those composed of clay minerals (e.g., porcelain), as well as cement and glass. ✓ With regard to mechanical behavior, ceramic materials are relatively stiff and strong—stiffnesses and strengths are comparable to those of the metals (see earlier figures). ✓ In addition, they are typically very hard. Historically, ceramics have exhibited Common objects made of ceramic materials: extreme brittleness (lack of ductility) and are highly susceptible to fracture scissors, a China teacup, a building brick, a floor tile, and a glass vase. ✓ However, newer ceramics are being engineered to have improved resistance to fracture; these materials are used for cookware, cutlery, and even automobile engine parts. ✓ Regarding optical characteristics, ✓ Furthermore, ceramic materials are typically insulative to the passage of heat ceramics may be transparent, and electricity (i.e., have low electrical conductivities) and are more resistant to translucent, or opaque, and some high temperatures and harsh environments than are metals and polymers. of the oxide ceramics (e.g., 𝐹𝑒3 𝑂4 ) exhibit magnetic behaviour.  CLASSIFICATION OF MATERIALS Polymers ✓ Polymers include the familiar plastic and rubber materials. Many of them are organic compounds that are chemically based on carbon, hydrogen, and other non metallic 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. ✓ These materials typically have low densities, whereas their mechanical characteristics are generally dissimilar to those of the metallic and ceramic materials—they are not as stiff or strong as other type materials discussed earlier. ✓ In addition, many of the polymers are extremely ductile and pliable (i.e., plastic), which means they are easily formed into complex shapes. ✓ In general, they are relatively inert chemically and unreactive in a large Several common objects number of environments. made of polymeric materials: plastic ✓ Furthermore, they have low electrical conductivities and are nonmagnetic. tableware (spoon, fork, and knife), billiard ✓ One major drawback to the polymers is their tendency to soften and/or balls, a bicycle helmet, two dice, a lawn mower wheel (plastic hub and rubber tire), decompose at modest temperatures, which, in some instances, limits their and a plastic milk carton. use.  CLASSIFICATION OF MATERIALS Composites ✓ A composite is composed of two (or more) individual materials that come from the categories previously discussed—metals, ceramics, and polymers. ✓ The design goal of a composite is to achieve a combination of properties that is not displayed by any single material and also to incorporate the best characteristics of each of the component materials. ✓ Furthermore, some naturally occurring materials are composites—for example, wood and bone. ✓ However, most of those we consider in our discussions are synthetic (or human-made) composites. For examples: ✓ One of the most common and familiar composites is fiberglass, in which small glass fibers are embedded within a polymeric material (normally an epoxy or polyester). Fiberglass mat.  Composites The glass fibers are relatively strong and stiff (but also brittle), whereas the polymer is more flexible. Thus, fiberglass is relatively stiff, strong and flexible. In addition, it has a low density (which means less weight too). Another technologically important material is the carbon fiber–reinforced polymer (CFRP) composite—carbon fibers that are embedded within a polymer. These materials are stiffer and stronger than glass fiber–reinforced materials but more expensive. Carbon fibre in automobile. CFRP composites are used in some aircraft and aerospace applications, as well as in high-tech sporting equipment (e.g., bicycles, golf clubs, tennis rackets, skis/snowboards) and recently in automobile bumpers.  ADVANCED MATERIALS ✓ Materials utilized in high-technology (or high-tech) applications are sometimes termed advanced materials. By high technology, I mean a device or product that operates or functions using relatively intricate and sophisticated principles, including electronic equipment (cell phones, DVD players, etc.), computers, fiber-optic systems, high- energy density batteries, energy-conversion systems, and aircraft. ✓ These advanced materials are typically traditional materials whose properties have been enhanced and also newly developed, high-performance materials. Semiconductors ✓ Semiconductors have electrical properties that are intermediate between those of electrical conductors (i.e., metals and metal alloys) and insulators (i.e., ceramics and polymers). ✓ Furthermore, the electrical characteristics of these materials are extremely sensitive to the presence of minute concentrations of impurity atoms, for which the concentrations may be controlled over very small spatial regions. https://youtu.be/c9arR8T0Qts?si=ka9dvhWLFc0gGljv ✓ Semiconductors have made possible the advent of integrated circuitry that has totally revolutionized the electronics and computer industries (not to mention our lives) over the past four decades.  ADVANCED MATERIALS Biomaterials ✓ The length and the quality of our lives are being extended and improved, in part, due to advancements in the ability to replace diseased and injured body parts. ✓ Replacement implants are constructed of biomaterials—nonviable (i.e., non living) materials that are implanted into the body, so that they function in a reliable, safe, and physiologically satisfactory manner, while interacting with living tissue. ✓ That is, biomaterials must be biocompatible— compatible with body tissues and fluids with which they are in contact over acceptable time periods. ✓ Example biomaterial applications include joint (e.g., hip, knee) and heart valve replacements, vascular (blood vessel) grafts, fracture-fixation devices, dental restorations, and generation of new organ tissues.  ADVANCED MATERIALS Smart materials ✓ Basically it’s a material that reacts quickly to a stimulus in a specific manner. ✓ The change in the material can also be reversible, as a change in stimulus can bring the material back to its previous state. ✓ Components of a smart material (or system) include some type of sensor (which detects an input signal) and an actuator (which performs a responsive and adaptive function). ✓ Actuators may be called upon to change shape, position, natural frequency, or mechanical characteristics in response to changes in temperature, electric fields, and/or magnetic fields. ✓ Four types of materials are commonly used for actuators: shape-memory alloys, piezoelectric ceramics, magnetostrictive materials, and electrorheological/magnetorheological fluids. https://youtu.be/Tn6xKhQ61Vs?si=C_zLvYbLyxde_mBj Nanomaterials ✓ One new material class that has fascinating properties and tremendous technological promise is the nanomaterials, which may be any one of the four basic types—metals, ceramics, polymers, or composites. ✓ However, unlike these other materials, they are not distinguished on the basis of their chemistry but rather their size; the nano prefix denotes that the dimensions of these structural entities are on the order of a nanometer (10−9 m)—as a rule, less than 100 nanometers (nm; equivalent to the diameter of approximately 500 atoms). ✓ with the development of scanning probe microscopes, which permit observation of individual atoms and molecules, it has become possible to design and build new structures from their atomic-level constituents, one atom or molecule at a time (i.e., “materials by design”). ✓ This ability to arrange atoms carefully provides opportunities to develop mechanical, electrical, magnetic, and other properties that are not otherwise possible. ✓ We call this the bottom-up approach, and the study of the properties of these materials is termed nanotechnology. ✓ Some of the physical and chemical characteristics exhibited by matter may experience dramatic changes as particle size approaches atomic dimensions. ✓ For example, materials that are opaque in the macroscopic domain may become transparent on the nanoscale; some solids become liquids, chemically stable materials become combustible, and electrical insulators become conductors. https://youtu.be/OFV5hqIXSRI?si=qbx0M7MVvHkXnsOw