Lecture 1 - Properties of Materials PDF

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