LECTURE 1 - Complete - PROPERTIES OF MATERIALS.pptx
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PROPERTIE S OF MATERIALS MACHINE ELEMENTS LECTURE 1 WHY STUDY MATERIAL PROPERTIES ? WOOD STEEL GOLD INTRODUCTION TO MATERIAL PROPERTIES DEFINITION: Material properties are the characteristics that describe how a material behaves under various conditions INTR...
PROPERTIE S OF MATERIALS MACHINE ELEMENTS LECTURE 1 WHY STUDY MATERIAL PROPERTIES ? WOOD STEEL GOLD INTRODUCTION TO MATERIAL PROPERTIES DEFINITION: Material properties are the characteristics that describe how a material behaves under various conditions INTRODUCTION TO MATERIAL PROPERTIES IMPORTANCE: For engineering design For material selection For predicting material behavior CATEGORI MECHANICAL PROPERTIES ELECTRICAL PROPERTIES ES THERMAL PROPERTIES TIME- DEPENDENT PROPERTY TENSILE YIELD STRENGTH STRENGTH SHEAR PROPORTIONA STRENGTH L LIMIT CATEGORI MECHANICAL MODULUS OF ELASTIC LIMIT PROPERTIES ELASTICITY ELECTRICAL IMPACT DUCTILITY PROPERTIES STRENGTH ES THERMAL HARDNESS MACHINABILITY PROPERTIES TIME- DEPENDENT PROPERTY MECHANICA CATEGORI MECHANICAL L PROPERTIES PROPERTIES ELECTRICAL ELECTRICAL ELECTRICAL PROPERTIES PROPERTIES RESISTIVITY ES THERMAL PROPERTIES TIME- DEPENDENT PROPERTY CATEGORI MECHANICAL PROPERTIES ELECTRICAL PROPERTIES ES THERMAL THERMAL EXPANSION PROPERTIES THERMAL TIME- CONDUCTIVITY DEPENDENT PROPERTY MECHANICA CATEGORI MECHANICAL L PROPERTIES PROPERTIES ELECTRICAL ELECTRICAL PROPERTIES PROPERTIES ES THERMAL THERMAL PROPERTIES PROPERTIES TIME- DEPENDENT CREEP PROPERTY STRESS AND STRAIN STRESS - force per unit area In machine design and elements, stress is equivalent to strength. STRESS AND STRAIN PROBLEM: A steel bar with a cross- sectional area of 2 cm² is subjected to a tensile load of 10 kN. Determine the tensile stress in the bar. TYPES OF STRESS STRESS AND STRAIN STRAIN - the percent change in length MECHANICAL PROPERTY MODULUS OF ELASTICITY (TENSION) The ratio of shear stress to shear strain in the linear-elastic region Also called the Young’s Modulus MECHANICAL PROPERTY MODULUS OF ELASTICITY (TENSION) A steel rod with an initial length of 500 mm is subjected to a tensile load of 20 kN. The cross-sectional area of the rod is 500 mm². If the modulus of elasticity of the steel is 200 GPa, calculate the elongation of the rod. MECHANICAL PROPERTY TENSILE STRENGTH The maximum stress a material can withstand when subjected to stretching before failure Also known as Ultimate Tensile Strength (UTS) Measurement method: Tensile test MECHANICAL PROPERTY TENSILE STRENGTH MECHANICAL PROPERTY TENSILE STRENGTH MECHANICAL PROPERTY YEILD STRENGTH The stress at which a material begins to deform plastically Often used as the maximum allowable stress in structural design MECHANICAL PROPERTY YEILD STRENGTH MECHANICAL PROPERTY PROPORTIONAL LIMIT The maximum stress at which stress is directly proportional to strain. Determines the stress limit for purely elastic behavior MECHANICAL PROPERTY PROPORTIONAL LIMIT MECHANICAL PROPERTY ELASTIC LIMIT The maximum stress a material can withstand without any permanent deformation Indicates the stress limit for fully reversible, elastic deformation MECHANICAL PROPERTY ELASTIC LIMIT MECHANICAL PROPERTY DUCTILIT Y The ability of a material to undergo plastic deformation without fracturing. A property describing how readily a material is drawn into a wire A material with high ductility is ductile, while one with low ductility is brittle. Gold is the most ductile metal. Platinum, silver, and copper are other highly ductile metals. MECHANICAL PROPERTY HARDNE SS A measure of a material's resistance to local plastic deformation, such as indentation or scratching. Relevant for wear resistance, machinability, and surface properties. Common test methods: Rockwell, Brinell, Vickers hardness tests. MECHANICAL PROPERTY HARDNE SS MECHANICAL PROPERTY HARDNE SS MECHANICAL PROPERTY MACHINABILI TY The ease with which a material can be cut, shaped, or formed using manufacturing processes Crucial for efficient and cost-effective manufacturing of components. It is difficult to define measurable properties related to machinability, so machinability is usually reported in comparative terms, relating the performance of a given material with some standard. MECHANICAL PROPERTY MACHINABILI TY The ease with which a material can be cut, shaped, or formed using manufacturing processes Crucial for efficient and cost-effective manufacturing of components. It is difficult to define measurable properties related to machinability, so machinability is usually reported in comparative terms, relating the performance of a given material with some standard. MECHANICAL PROPERTY IMPACT STRENGTH The ability of a material to absorb energy and resist fracture under sudden, high-rate loading (impact) Crucial for applications where materials may be subjected to sudden, high-impact loads, such as in automotive and aerospace industries. MECHANICAL PROPERTY SHEAR STRENGTH Often used as the maximum allowable stress in structural design Important in design of bolts, rivets, and welded joints MECHANICAL PROPERTY SHEAR STRENGTH MECHANICAL PROPERTY SHEAR STRENGTH Often used as the maximum allowable stress in structural design Important in design of bolts, rivets, and welded joints TENSILE YIELD STRENGTH STRENGTH SHEAR PROPORTIONA STRENGTH L LIMIT CATEGORI MECHANICAL MODULUS OF ELASTIC LIMIT PROPERTIES ELASTICITY ELECTRICAL IMPACT DUCTILITY PROPERTIES STRENGTH ES THERMAL HARDNESS MACHINABILITY PROPERTIES TIME- DEPENDENT PROPERTY MECHANICA CATEGORI MECHANICAL L PROPERTIES PROPERTIES ELECTRICAL ELECTRICAL ELECTRICAL PROPERTIES PROPERTIES RESISTIVITY ES THERMAL PROPERTIES TIME- DEPENDENT PROPERTY ELECTRICAL PROPERTY ELECTRICAL RESISTIVITY Electrical Resistivity is a property of material that describes how strongly a material opposes the flow of electric current. The SI unit for resistivity is the ohm-meter (Ω·m) ELECTRICAL PROPERTY ELECTRICAL RESISTIVITY Conductors: Low resistivity (~ 10⁻⁸ to 10⁻⁶ Ω·m) Semiconductors: Medium resistivity (~ 10⁻⁴ to 10⁴ Ω·m) Insulators: High resistivity (> 10⁸ Ω·m) ELECTRICAL PROPERTY ELECTRICAL RESISTIVITY Copper: ~1.68 × 10⁻⁸ Ω·m (at 20°C) Aluminum: ~2.82 × 10⁻⁸ Ω·m (at 20°C) Silicon: ~640 Ω·m (at 20°C) Glass: ~10¹⁰ to 10¹⁴ Ω·m ELECTRICAL PROPERTY OTHER ELECTRICAL PROPERTY Electrical Conductivity Dielectric Strength Electrical Susceptibility Piezoelectricity Ferroelectricity Superconductivity Electron Mobility Capacitance Magnetoresistance MECHANICA CATEGORI MECHANICAL L PROPERTIES PROPERTIES ELECTRICAL ELECTRICAL ELECTRICAL PROPERTIES PROPERTIES RESISTIVITY ES THERMAL PROPERTIES TIME- DEPENDENT PROPERTY CATEGORI MECHANICAL PROPERTIES ELECTRICAL PROPERTIES ES THERMAL THERMAL EXPANSION PROPERTIES THERMAL TIME- CONDUCTIVITY DEPENDENT PROPERTY THERMAL PROPERTY THERMAL EXPANSION Thermal expansion is a property of material that describes how the size of an object changes as its temperature changes. THERMAL PROPERTY THERMAL EXPANSION THERMAL PROPERTY THERMAL CONDUCTIVITY Thermal conductivity is a fundamental property of materials that describes their ability to conduct heat. It's a measure of how quickly heat is transferred through a material when there's a temperature difference across it. THERMAL PROPERTY THERMAL CONDUCTIVITY THERMAL PROPERTY THERMAL CONDUCTIVITY High conductivity: Metals (e.g., copper ~400 W/(m·K)) Medium conductivity: Some ceramics and polymers Low conductivity: Insulators (e.g., air ~0.024 W/(m·K)) CATEGORI MECHANICAL PROPERTIES ELECTRICAL PROPERTIES ES THERMAL THERMAL EXPANSION PROPERTIES THERMAL TIME- CONDUCTIVITY DEPENDENT PROPERTY MECHANICA CATEGORI MECHANICAL L PROPERTIES PROPERTIES ELECTRICAL ELECTRICAL PROPERTIES PROPERTIES ES THERMAL THERMAL PROPERTIES PROPERTIES TIME- DEPENDENT CREEP PROPERTY TIME-DEPENDENT PROPERTY CREEP Creep is a time-dependent deformation that occurs in materials when they are subjected to a constant load, stress or high temperature. It can occur as a result of long-term exposure to high levels of stress that are still below the yield strength of the material It is more severe in materials that are subjected to heat for long periods TIME-DEPENDENT PROPERTY CREEP Crucial in design of turbine blades, nuclear reactors, and other high-temperature components Important in long-term structural integrity of buildings and bridges END OF LECTURE 1
