Lecture 2: Physical and Mechanical Properties of Materials (PDF)

Lecture.2 Physical and mechanical properties of materials Manufacturing Technology (EIM1101) Dr. Mohamed Taha Eldaly  Reference Book Materials Science and Engineering Nine Edition By William D. Callister, Jr David G. Reth...

Lecture.2 Physical and mechanical properties of materials Manufacturing Technology (EIM1101) Dr. Mohamed Taha Eldaly  Reference Book Materials Science and Engineering Nine Edition By William D. Callister, Jr David G. Rethwisch Some of these materials are from different internet resources. 2  Course outlines Week No.1 Introduction to manufacturing. Week No.9 Metal forming (cont.), sheet metal work. Week No.2 Physical and mechanical properties of materials. Week No.10 Machining operations. Week No.3 Classification of materials, metals, and Week No.11 Tool life and materials their alloys. Week No.12 12th Exam Week No.4 Polymers and composites. Week No.13 Joining operations Week No.5 Metal casting Week No.14 Shaping of plastics Week No.6 Metal casting (cont.), mold and riser Week No.15 Revision. design, die casting Week No.16 Final Exam Week No.7 7th Exam Week No.8 Metal forming (Rolling, Extrusion & Drawing). 3 Physical and mechanical properties of materials  Tensile test  Stiffness  Limit of elasticity  Ductility and tensile strength  Hardness  Toughness  Resilience  Electrical conductivity  Thermal conductivity 4  Physical and mechanical properties of materials (a) Schematic illustration of how a tensile load produces an elongation and positive linear strain. (b) Schematic illustration of how a compressive load produces contraction and a negative linear strain. A standard tensile specimen with circular cross section 5 Physical and mechanical properties of materials Schematic representation of the apparatus used to conduct tensile stress– strain tests. The specimen is elongated by the moving crosshead; load cell and extensometer measure, respectively, the magnitude of the applied load and the elongation. Tensile tests specimen 6  Physical and mechanical properties of materials (d) Schematic representation of torsional deformation (i.e., angle of twist f) produced by an applied torque T. Hooke’s law- relationship between engineering stress and engineering strain for elastic deformation (tension and compression) Schematic stress–strain diagram showing linear elastic deformation for loading and unloading Schematic stress–strain cycles. diagram showing nonlinear elastic behavior and how secant and tangent moduli are 7 determined.  Solved example A piece of copper originally 305 mm long is pulled in tension with a stress of 276 MPa. If the deformation is entirely elastic, what will be the resultant elongation? E= 110x103 MPa 8  Mechanical properties Ductility, as percent elongation Ductility, as percent reduction in area 9  Mechanical properties Resilience Resilience is the capacity of a material to absorb energy when it is deformed elastically and then, upon unloading, to have this energy recovered. Definition of modulus of resilience Modulus of resilience for linear elastic behavior Toughness Toughness is a mechanical term that may be used in several contexts. For one, toughness (or more specifically, fracture toughness) is a property that is indicative of a material’s resistance to fracture when a crack 10  Hardness Measures the materials resistance to indentation or scratching Hardness Value Read Directly From Dial Table Height Indenter Adjustment Test Component Placed on Table Activating lever Direct Reading Hardness Testing Machine (Vickers or Brinell) 11  Hardness Measures the materials resistance to indentation or scratching A square pyramid shaped indenter (point angle 136°) is forced into the specimen. The diagonal length of the indented square is measured. This measurement is taken by a special microscope for accuracy. It is then converted into a Vickers hardness number. 12 Hardness Brinell Hardness Testing Measures the materials resistance to indentation or scratching The Brinell hardness test uses a hardened steel or tungsten carbide ball of 10mm, 5mm or 1mm diameter. The diameter of the indentation is measured, and it is used to indicate the hardness of the material 13 Hardness 14 Electrical Properties Ohm’s Law 15  Electrical Conduction Ohm's Law: V=IR voltage drop (volts = J/C) resistance (Ohms) C = Coulomb current (amps = C/s) Resistivity, : a material property that is independent of sample size and geometry surface area RA  of current flow l current flow path length Conductivity,  1    16  Conductivity: Comparison Room temperature values (Ohm-m)-1 = ( - m)-1 METALS conductors CERAMICS -10 Silver 6.8 x 10 7 Soda-lime glass 10 -10 -11 Copper 6.0 x 10 7 Concrete 10 -9 Iron 1.0 x 10 7 Aluminum oxide Tinitial Tfinal  final l l final initial   l (Tfinal Tinitial ) l initial linear coefficient of thermal expansion (1/K or 1/ºC)  21 Thermal Conductivity: Comparison Material k (W/m-K) Metals Aluminum 247 atomic vibrations Steel 52 and motion of free Tungsten 178 electrons Gold 315 Ceramics increasing k Magnesia (MgO) 38 Alumina (Al2O3) 39 atomic vibrations Soda-lime glass 1.7 Silica (cryst. SiO2) 1.4 Polymers Polypropylene 0.12 Polyethylene 0.46-0.50 vibration/rotation of Polystyrene 0.13 chain molecules Teflon 0.25 22  Material application based on thermal properties Re-entry T Application: Distribution Space Shuttle Orbiter reinf C-C silica tiles nylon felt, silicon rubber (1650ºC) (400-1260ºC) coating (400ºC) Chapter-opening photograph, Chapter 23, Callister 5e (courtesy of the National Aeronautics and Space Fig. 19.2W, Callister 6e. (Fig. 19.2W adapted from L.J. Administration.) Korb, C.A. Morant, R.M. Calland, and C.S. Thatcher, "The Silica tiles (400-1260ºC): Shuttle Orbiter Thermal Protection System", Ceramic Bulletin, No. 11, Nov. 1981, p. 1189.) -- large scale application -- microstructure: ~90% porosity! Si fibers bonded to one another during heat treatment. 100 mm Fig. 19.3W, Callister 5e. (Fig. 19.3W courtesy the Fig. 19.4W, Callister 5e. (Fig. 219.4W courtesy National Aeronautics and Space Administration.) Lockheed Aerospace Ceramics 23 Systems, Sunnyvale, CA.) 23  Recommended internet resources to check https://www.gordonengland.co.uk/hardness/rockwell.htm https://ncalculators.com/mechanical/metal-hardness-calculator.htm https://www.youtube.com/watch?v=67fSwIjYJ-E&ab_channel=labtesting https://www.youtube.com/watch?v=RJXJpeH78iU&ab_channel=Materia lsScience2000 Thank you  24