[PRELIM]_03_Properties of Engineering Materials.pptx
Transcript
Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 PROPERTIES OF ENGINEERING MATERIALS ES 011_Materials Science and Engineering Cagayan State Univers...
Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 PROPERTIES OF ENGINEERING MATERIALS ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Learning Objectives: At the end of this lecture, you should be able to: learn the different properties and characteristics of materials; discuss the stress and strain diagram; and define stress, strain, Hooke’s Law, etc. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 PROPERTIES OF ENGINEERING MATERIALS Materals for Engineering applications are selected so as to perform satisfatorily during service : For Example : o Material for a high-rice building or a highway bridge should prossess adequate strength, rough surface and sufficient rigidity. o A water-retaining structures would be built with a material that is impermeable, crack free, strong and does not react with water. o A road surface needs such materals that show little movement under the impact of load, are water resistant and eassy to repair. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 PROPERTIES OF ENGINEERING MATERIALS : (continued) The common properties of the engineering materials: 1. Physical Properties 2. Mechanical Properties 3. Chemical Properties ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Properties & Characteristics of Engineering Materials 1. Physical Properties – are observable and measurable whose value describes a state of a physical system Examples of Physical Properties: o Mass Density - volumetric mass density or specific mass is the material's mass per unit of volume. (Example: Steel) o Weight Density - material's weight per unit of volume. (Example: Steel) o Dielectric Strength - maximum electric field that a pure material can withstand under ideal conditions without breaking down. o Electrical Resistivity - measures how strongly it resists electric current. A low resistivity indicates a material that readily allows electric current. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Examples of Physical Properties: o Melting point – or liquefaction point of a substance is the temperature at which it changes state from solid to liquid where both phases exist in equilibrium. o Heat Distortion Temperature – or heat distortion temperature (HDT, HDTUL, or DTUL) is the temperature at which a polymer or plastic sample deforms under a specified load. o Refractive Index – or refraction index of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. The refractive index determines how much the path of light is bent, or refracted, when entering a material. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Examples of Physical Properties: o Specific Gravity – also called relative density, ratio of the density of a substance to that of a standard substance. o Thermal Conductivity – measure of its ability to conduct heat or move heat from one location to another. o Coefficient of Expansion – tendency of matter to change its shape, area, volume, and density in response to a change in temperature. Example: Steel – 11.7 x 10^-6 in/in-F or 6.5 x 10^-6 m/m-C o Specific Heat – the quantity of heat required to raise the temperature of one gram of a substance by one Celsius degree ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Properties & Characteristics of Engineering Materials 2. Chemical Properties any qualities that can be established only by changing its chemical identity through chemical reactions specifically in connection with corrosion, caustic embrittlement, presence of alloying elements, etc. o Corrosion – deterioration of a metal as a result of chemical reactions between it and the surrounding environment. o Caustic embrittlement –phenomenon where the material of a boiler such as rivets, bends and joints, which are under stress, becomes brittle due to the accumulation of caustic substances. o Alloying Elements – are added to steels in order to improve specific properties such as strength, wear, and corrosion resistance. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Properties & Characteristics of Engineering Materials 3. Mechanical Properties – define the behavior of materials under the action of external forces called loads. Forces, Load and Stresses o Forces: When body is pulled or pushed, it said to be acted upon by a force. o Load: When a solid body is subjected to external forces called load, the body is deformed and internal force is produced o Stresses: measure of a force acting on a unit area of an imaginary section through a body. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Strength of Materials ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Force Patterns needs to Remember for Onward Discussion ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Concept of Stress and Strain o Material subjected to load or force o Mechanical behaviors of materials. o Response/deformation vs applied load/force. o Mechanical properties (Ex: strength, hardness, ductility, stiffness) o A force is an influence that causes an object to undergo a certain change, either concerning its movement, direction, or geometrical construction. o External forces acting on a rigid body are termed as loads. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Engineering Stress () Stress is the force divided by cross sectional area. Types: 1. Compression 2. Tension 3. Shear ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Engineering Strain, ε Strain is defined as “deformation of a solid due to stress”. It is the amount of deformation which an object experiences compared to its original size and shape. where ε = unitless measure of engineering strain δl= change of length (m, in) lo = initial length (m, in) E = Young's modulus (Modulus of Elasticity) (Pa, psi) ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Typical Engineering Stress-Strain Plot Figure 2.4 Typical engineering stress‑strain plot in a tensile test of a metal. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Tension Tension is the type of loading in which the two sections of material on either side of a plane tend to be pulled apart or elongated. Tensile Stress A force which points away from its point of application. Tensile Strain measure of the deformation of an object under tensile stress and is defined as the fractional change of the object's length when the object experiences tensile stress ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Compression o Applies a load that squeezes the ends of a cylindrical specimen between two plates. o As the specimen is compressed, its height is reduced and its cross-sectional area is increased. Compressive Stress o The force which points towards its point of application. Compressive Strain o change in length per original length due to a compressive force acting on the object. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Shearing Shear involves applying a load parallel to a plane which caused the material on one side of the plane to want to slide across the material on the other side of the plane. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Shear Properties Application of stresses in opposite directions on either side of a thin element Figure 2.8 Shear (a) stress and (b) strain. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Shear Stress and Strain ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Bending Loading by bending involves applying a load in a manner that causes a material to curve and results in compressing the material on one side and stretching it the other. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Torsion Torsion is the application of a force that causes twisting in a material. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Tensile Properties o Elastic limit is the greatest stress the material can withstand without any measurable permanent strain remaining on the complete release of load. o Yield strength is the stress required to produce a small-specified amount of plastic deformation. o Proportional limit is the highest stress at which stress is linearly proportional to strain. o Ultimate tensile strength is an engineering value calculated by dividing the maximum load on a material experienced during a tensile test by the initial cross section of the test sample. o True fracture strength is the load at fracture divided by the cross sectional area of the sample. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Ductility o a measure of the extent to which a material will deform before fracture. o also be expressed as either % elongation or % reduction in area. % Elongation = (Lf- Lo/Lo) * 100 % Reduction = (Ao – Af/ Ao) * 100 where: Lf & Af are the fracture length and cross- sectional area at the point of fracture respectively. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Ductility ability of a metal to be stretched into wires permanently without fracture. o Term used when plastic deformation occurs as a result of tensile load. o Metals that lack ductility will crack or break before bending. o Example is wire drawing (Copper, aluminum, and steel are ductile material) ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Malleability o Ability of a metal to be hammered, rolled, or pressed into various shapes without fracture. o Term used when plastic deformation occurs as a result of compressive load. o Examples are forging & rolling. (Copper, aluminum, and steel are malleable material) ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Brittleness o tendency of a material to fracture without any plastic or little deformation. o opposite of ductility & malleability. o Example: A steel rod is bent easily but a grey cast iron rod breaks when subjected to bent. So, grey cast iron rod is a brittle material. Glass is a most common example. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Stiffness of Materials ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Understanding the differences between the mechanical properties of strength vs. stiffness vs. hardness is foundational in engineering, yet these properties are often confused. o Stiffness tendency for an element to return to its original form after being subjected to a force. o Strength measures how much stress can be applied to an element before it deforms permanently or fractures. o Hardness measures a material’s resistance to surface deformation. For some metals, like steel, hardness and tensile strength are roughly proportional. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Hardness o Hardness is the resistance of a material to localized deformation. o The term can apply to deformation from indentation, scratching, cutting or bending. o In metals, ceramics and most polymers, the deformation considered is plastic deformation of the surface. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Fatigue Properties o Fatigue cracking results from cyclic stresses that are below the ultimate tensile stress, or even the yield stress of the material. o The name “fatigue” is based on the concept that a material becomes “tired” and fails at a stress level below the nominal strength of the material. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Creep, Fatigue, Fracture in Engineering Materials Creep slow and continuous Fracture refers to the Fatigue Changes in the deformation that occur in the breakage of a material into mechanical properties of the material under the dimensions of the material separate parts under the action of cyclical or under a constant stress, action of stress; repeated stress. usually at high temperatures; ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Elasticity & Plasticity o Elasticity is the property by which a material is enabled to RETURN exactly to its original shape on removal of a straining force, a very important property in materials. o Plasticity is the reverse of elasticity; a plastic material will RETAIN exactly the shape it assumes under load when the load is removed. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Elasticity and Plasticity o A material is said to be perfectly elastic, if deformation produced in the object due to the application of external load disappears completely with the removal of the load/stress. o A material is said to be plastic, If deformation is retained after removing the applied stress. o The point of transition from elastic to plastic is termed Elastic limit or yield point which marks the end of elastic behavior and the beginning of plastic behavior ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Elasticity vs Plasticity If the shape and/or size changes, then the change is called deformation and the corresponding force is called deforming force. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Plasticity of Materials ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Elasticity of Materials ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Elastic deformation o Stress – Strain behavior o Hooke’s law stress is linearly proportional to strain. σ = Eε where: E = Modulus of elasticity = stiffness or a material’s resistance to elastic deformation. o Non-permanent Tangent modulus ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Modulus of Elasticity o Within an elastic limit, stress is directly proportional to strain. o This constant is known as Coefficient of Elasticity or Modulus of Elasticity. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Modulus of Elasticity of Some Metallic Materials ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Modulus of elasticity o E may be thought of as stiffness. Greater the E, stiffer the material. With increasing temperature, the E diminishes ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Young’s Modulus ratio of the uniaxial stress over the uniaxial strain in the range of stress in which Hooke's Law holds. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Shear Modulus Bulk Modulus (B) (Modulus of Rigidity) The ratio of shear The ratio of normal stress stress and shear and volumetric strain. OR strain. Pressure applied Fractional change in volume of an object. K= -V (dP/dV) B solids >B liquids >B gas ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 OTHER PROPERTIES OF ENGINEERING MATERIALS ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Other Properties and Characteristics of Materials o Thermal Properties o Magnetic Properties o Optical Properties o Electrical Properties ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 THERMAL PROPERTIES Why Study Thermal Properties of Engineering Materials? o Ceramics engineering material most susceptible to thermal shock (brittle fracture resulting from internal stresses that are established within a ceramic piece as a result of rapid changes in temperature (normally upon cooling). o Thermal shock susceptibility of a ceramic material to this phenomenon is a function of its thermal and mechanical properties (coefficient of thermal expansion, thermal conductivity, modulus of elasticity, and fracture strength). ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Thermal property - response of a material to the application of heat. (Ex: Heat capacity, thermal expansion, and thermal conductivity) o As a solid absorbs energy in the form of heat, its temperature rises and its dimensions increase. o The energy may be transported to cooler regions of the specimen if temperature gradients exist, and, ultimately, the specimen may melt/break. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Heat Capacity o ratio of energy change (energy gained or lost) and the resulting temperature change; o represents the amount of energy required to produce a unit temperature rise; o Solid materials when heated, experience an increase in temperature, signifying that some energy has been absorbed. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Thermal Expansion o tendency of the material to increase in length, area, or volume, changing its size and density, in response to an increase in temperature o Solid materials expand heated and contract cooled. o Coefficient of thermal expansion (constant of proportionality) - fractional change in length of the material proportional to the temperature change. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Values of coefficient of thermal expansion for polymers are typically greater than those for metals, which in turn are greater than those for ceramic materials. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Thermal Conductivity Thermal Conduction transport of thermal energy from high to low temperature regions of a material. o Solid materials, heat is transported by free electrons and by vibrational lattice waves, or phonons. o High thermal conductivities for pure metals due to the large numbers of free electrons which transport thermal energy. o Ceramics and polymers are poor thermal conductors because free-electron concentrations are low and phonon conduction predominates. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Thermal Stresses Thermal stresses induced in a body as a result of changes in temperature. Thermal shock resistance capacity of a material to withstand fracture or undesirable plastic deformation due to thermal stress. For a ceramic body that is rapidly cooled, the resistance to thermal shock depends not only on the magnitude of the temperature change, but also on the mechanical and thermal properties of the material. The thermal shock resistance is best for ceramics that have high fracture strengths and high thermal conductivities, as well as low moduli of elasticity and low coefficients of thermal expansion. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Materials of Importance o One type of thermostat - a device that is used to regulate temperature – uses the phenomenon of thermal expansion - the elongation of a material as it is heated. The heart of this type of thermostat is a bimetallic strip - strips of two metals having different coefficients of thermal expansion are bonded along their lengths. o A change in temperature causes this strip to bend; upon heating, the metal having the greater expansion coefficient elongates more, producing the direction of bending shown in the figure. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Some Applications that Require Dimensional Stability with Temperature Fluctuations o Compensating pendulums and balance wheels for mechanical clocks and watches. o Structural components in optical and laser measuring systems that require dimensional stabilities on the order of a wavelength of light. o Bimetallic strips that are used to actuate microswitches in water heating systems. o Shadow masks on cathode-ray tubes that are used for television and display screens; higher contrast, improved brightness, and sharper definition are possible using low-expansion materials. o Vessels and piping for the storage and piping of liquefied natural gas. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Why Study Magnetic Properties of Engineering Materials? An understanding of the mechanism that explains the permanent magnetic behavior of some materials may allow us to alter and in some cases tailor the magnetic properties. ES 011_Materials Science and Engineering Magnetism - phenomenon APPLIED MAGNETIC FIELD where materials exert an Created by current through a coil: attractive or repulsive force or influence on other materials Applied N turns total magnetic field H L = length of each turn Many modern technological devices rely on current I magnetism and magnetic materials; these Relation for the applied magnetic field, H: include electrical power generators and transformers, electric motors, radio, television, telephones, computers, and NI H current components of sound and video L reproduction systems. applied magnetic field units = (ampere-turns/m) RESPONSE TO A MAGNETIC FIELD Magnetic induction results in the material B = Magnetic Induction (tesla) inside the material current I Magnetic susceptibility, c (dimensionless) B >0 c measures the vacuum = 0 material response permanent magnet! Callister 6e. Applied Magnetic Field (H) 4. Coercivity, Hc : 1. initial (unmagnetized state) Negative H needed to demagnitize! B Hard vs Soft Magnets large coercivity d --good for perm magnets Har d Har --add particles/voids to Soft make domain walls Applied Magnetic hard to move (e.g., Field (H) Adapted from Fig. 20.16, tungsten steel: Callister 6e. (Fig. 20.16 from K.M. Ralls, T.H. Courtney, and Hc = 5900 amp-turn/m) small coercivity--good for elec. motors J. Wulff, Introduction to Materials Science and (e.g., commercial iron 99.95 Fe) Engineering, John Wiley and Sons, Inc., 1976.) ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 MAGNETIC STORAGE Information is stored by magnetizing material. Head can... recording medium --apply magnetic field H & align domains (i.e., magnetize the medium). --detect a change in the recording head magnetization of the Simulation of hard drive Adapted from Fig. 20.18, Callister 6e. medium. courtesy Martin Chen. Reprinted with permission (Fig. 20.18 from J.U. Lemke, MRS Bulletin, Vol. XV, No. 3, p. 31, 1990.) Two media types: from International Business Machines Corporation. --Particulate: needle-shaped --Thin film: CoPtCr or CoCrTa g-Fe2O3. +/- mag. moment alloy. Domains are ~ 10-30nm! along axis. (tape, floppy) (hard drive) Adapted from Fig. 20.20(a), Adapted from Fig. Callister 6e. (Fig. 20.20(a) 20.19, Callister 6e. from M.R. Kim, S. (Fig. 20.19 Guruswamy, and K.E. courtesy P. Rayner ~2.5m ~60nm Johnson, J. Appl. Phys., and N.L. Head, IBM Vol. 74 (7), p. 4646, 1993. ) Corporation.) 9 ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 TRANSFORMERS Transformer cores require the use of soft magnetic materials, which are easily magnetized and demagnetized (and also have relatively high electrical resistivities). ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Why Study Optical Properties of Engineering Materials? Prediction of properties of materials after exposure to electromagnetic radiation is possible when we are familiar with their optical properties and understand the mechanisms responsible for their optical behaviors. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Optical property material’s response to exposure to electromagnetic radiation and, in particular, to visible light describe how light interacts with matter, including how it is absorbed, transmitted, reflected, or refracted. Optical relates to the study or use of light. o encompasses the properties, behaviors, and applications of light, including o both visible and non-visible portions of the electromagnetic spectrum. o refers to anything related to vision or sight. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 ELECTROMAGNETIC SPECTRUM entire distribution of the electromagnetic radiation according to frequency (wave/s) or wavelength. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 ELECTROMAGNETIC SPECTRUM 1. Radio Waves 2. Microwaves Wavelengths : Longest in the spectrum. Wavelengths: Shorter than radio waves Uses: Broadcasting, television. but longer than infrared. Uses: Microwave ovens, telephones, signals, communication, radar. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 ELECTROMAGNETIC SPECTRUM 3. Infrared Radiation 4. Visible Light Wavelengths: Longer than visible light, Wavelengths: Small portion of the shorter than microwaves. spectrum that is visible to the human Uses: Thermal imaging, fires, radiators eye. remote controls, transmits heat from the Colors: Red, orange, yellow, green, blue, sun. indigo, violet. Uses: Vision, optical communication. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 ELECTROMAGNETIC SPECTRUM 5. Ultraviolet Radiation Wavelengths: Shorter than visible light, longer than X-rays. Uses: Germicidal lamps, sterilization, black lights. 6. X-rays Wavelengths: Shorter than ultraviolet light, longer than gamma rays. Uses: Medical imaging, security screening. 7. Gamma Rays Wavelengths: Shortest in the spectrum. Uses: Medical treatment (radiotherapy), industrial imaging, nuclear reactions ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 ULTRAVIOLET RADIATION EXAMPLES ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 XRAYS EXAMPLES ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 GAMMA RAYS EXAMPLES ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 OPTICAL PROPERTIES 1. Reflective 5. Shiny 2. Translucent 6. Luminescent 3. Opaque 7. Fluorescent 4. Transparent 8. Refractive ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 1. Reflective Reflective materials 2. Refractive materials cause a bounce back a significant portion of change in the direction of light as it incident light. passes through, typically due to a change in the material's refractive (Example:) Mirrors are highly reflective, providing clear and specular reflection. index. (Example:) Lenses are refractive optical elements used in eyeglasses, cameras, and telescopes. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 3. Translucent materials allow some 4. Transparent materials allow light to light to pass through, but they scatter or pass through with minimal scattering or diffuse the light, making objects on the other absorption, maintaining clarity and allowing side less distinct or blurred. objects on the other side to be seen clearly. (Example:) Frosted glass is translucent. When light (Example:) Clear glass and certain plastics are passes through it, the transmitted light is scattered, transparent. When light passes through them, the and objects seen through the glass appear blurry. transmitted light is not significantly scattered, and objects are visible with little distortion. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 5. Opaque materials do not allow 6. Shiny Shiny materials reflect light to pass through; they block or absorb it. light specularly, providing a glossy appearance. (Example:) Wood is opaque, preventing light from passing through its bulk. (Example:) Polished metal surfaces are shiny due to specular reflection. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 7. Luminescent materials emit light, 8. Fluorescent materials absorb either through absorption and re-emission short-wavelength light and re-emit it at (fluorescence/ phosphorescence) or by longer wavelengths. another process. (Example:) Fluorescent bulbs contain (Example:) Glow-in-the-dark materials are materials that emit visible light when excited phosphorescent, emitting light after exposure to a by ultraviolet light. light source.) ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Applications of Optical Phenomena Luminescence -- energy is absorbed as a consequence of electron excitations, which is subsequently reemitted as visible light. o When light is reemitted less than 1s after excitation, the phenomenon is called fluorescence. o For longer reemission times, the term phosphorescence is used. Electroluminescence phenomenon by which light is emitted as a result of electron–hole recombination events that are induced in a forward-biased diode. o Light-emitting diode (LED) device experiences electroluminescence ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Photoconductivity LASERS phenomenon by which the electrical conductivity of some o Light Amplification by Stimulated semiconductors may be Emission of Radiation enhanced by photo-induced o Coherent and high-intensity light beams electron transitions and holes are are produced in lasers by stimulated generated electron transitions. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Optical Fibers in Communication Use of fiber-optic technology in modern telecommunications provides for the transmission of information that is interference-free, rapid, and intense. An optical fiber is composed of the following elements: o Core through which the pulses of light propagate. o Cladding, which provides for total internal reflection and containment of the light beam within the core. o Coating, which protects the core and cladding from damage. ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Materials of Importance PHOTOVOLTAIC SOLAR CELL o Cell is made of polycrystalline silicon that has been fabricated to form a p– n junction. o Photons that originate as light from the sun excite electrons into the conduction band on the n side of the junction and create holes on the p side. o These electrons and holes are drawn away from the junction in opposite directions and become part of an external current. ES 011_MATERIALS SCIENCE AND ENGINEERING Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 Why Study Electrical Properties of Engineering Materials? IMPORTANCE when we consider an integrated circuit package, the electrical behaviors of the various materials are diverse. Some need to be highly electrically conductive (e.g., connecting wires), whereas electrical insulativity is required of others (e.g., protective package encapsulation). ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 ELECTRICAL CONDUCTION Ohm's Law: V= IR voltage drop (volts = J/C) resistance (Ohms) C = Coulomb current (amps = C/s) Resistivity, r: -- a material property that is independent of sample size and geometry RA surface area of current flow l current flow Conductivity, s 1 path length 93 ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 ELECTRICAL PROPERTIES Which will have the greater resistance? 2 2 8 D R1 D 2 D2 2 R1 2D R2 2 2 2D D 8 2 Analogous to flow of water in a pipe Resistance depends on sample geometry and size. 94 ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 MEASUREMENT OF R 95 ES 011_Materials Science and Engineering Cagayan State University – College of Engineering and Architecture S.Y. 2024-2025 DEFINITIONS Further definitions J=
