Manufacturing Technology: Properties of Materials
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Questions and Answers

What is the primary property described by resilience in materials?

  • The ability to withstand shear stress
  • The ability to absorb energy during elastic deformation and recover it upon unloading (correct)
  • The ability to withstand permanent deformation
  • The ability to conduct electricity

    • What is the modulus of resilience associated with?

  • Elastic deformation (correct)
  • Mechanical fatigue
  • Thermal expansion
  • Plastic deformation

    • Using Hooke's law, if a piece of copper with an original length of 305 mm is subjected to a tensile stress of 276 MPa, what principle do we apply to determine its elongation?

  • Compressive modulus
  • Secant modulus
  • Modulus of toughness
  • Elastic modulus (correct)

    • Ductility can be quantified in which of the following ways?

    <p>As percent elongation and percent reduction in area (A)</p> Signup and view all the answers

    What does fracture toughness measure in a material?

    <p>Resistance to fracture when a crack is present (D)</p> Signup and view all the answers

    When considering nonlinear elastic behavior, which moduli are determined?

    <p>Secant and tangent moduli (D)</p> Signup and view all the answers

    Which shape is the indenter used in the Vickers hardness test?

    <p>Square pyramid (A)</p> Signup and view all the answers

    What is the primary measurement taken in the Brinell hardness test?

    <p>Diagonal length of the indented square (B)</p> Signup and view all the answers

    Which materials are typically used for the ball in the Brinell hardness test?

    <p>Hardened steel or tungsten carbide (A)</p> Signup and view all the answers

    How is the Vickers hardness number determined after measuring the indentation?

    <p>Through a conversion calculation from measurements (C)</p> Signup and view all the answers

    Which property is measured by a tensile test?

    <p>Ductility (C)</p> Signup and view all the answers

    What is the primary purpose of measuring hardness in materials?

    <p>To measure resistance to deformation (D)</p> Signup and view all the answers

    What is an indication of a material's resilience?

    <p>The ability to return to its original shape after deformation (C)</p> Signup and view all the answers

    Which property describes the maximum stress that a material can withstand while being stretched or pulled?

    <p>Tensile strength (C)</p> Signup and view all the answers

    In a tensile test, what does the term 'stiffness' refer to?

    <p>The resistance to elastic deformation (C)</p> Signup and view all the answers

    What is the term for the ability of a material to absorb energy and plastically deform without fracturing?

    <p>Toughness (A)</p> Signup and view all the answers

    What does the limit of elasticity signify in materials?

    <p>The stress beyond which a material will deform permanently (A)</p> Signup and view all the answers

    Which property is primarily assessed when evaluating a material's ability to conduct electricity?

    <p>Electrical conductivity (C)</p> Signup and view all the answers

    What is the thermal protection system for the Space Shuttle Orbiter primarily made of?

    <p>Silica tiles (D)</p> Signup and view all the answers

    Which polymer has the highest thermal resistance based on the given properties?

    <p>Teflon (D)</p> Signup and view all the answers

    What is the approximate porosity of the silica tiles used in the Space Shuttle Orbiter?

    <p>90% (C)</p> Signup and view all the answers

    At what temperature do the silica tiles operate effectively?

    <p>400-1260ºC (B)</p> Signup and view all the answers

    Which material is not mentioned as part of the thermal protection system for the Space Shuttle?

    <p>Polystyrene (C)</p> Signup and view all the answers

    What process is used to bond the silica fibers in the thermal protection tiles?

    <p>Heat treatment (A)</p> Signup and view all the answers

    What is the purpose of using high porosity materials like silica tiles in thermal protection?

    <p>To reduce heat transfer (B)</p> Signup and view all the answers

    Which thermal protection material can operate at the highest temperature?

    <p>Reinforced carbon-carbon (C)</p> Signup and view all the answers

    What is the primary use of measuring the diameter of an indentation in materials?

    <p>To indicate the hardness of the material (A)</p> Signup and view all the answers

    What does Ohm's Law express the relationship between?

    <p>Voltage, current, and resistance (D)</p> Signup and view all the answers

    What does resistivity ($ ho$) describe?

    <p>A material property independent of sample size (A)</p> Signup and view all the answers

    Which metal has the highest conductivity based on the provided information?

    <p>Silver (D)</p> Signup and view all the answers

    Which equation correctly relates linear thermal expansion?

    <p>$l_{final} = l_{initial} + eta l_{initial} (T_{final} - T_{initial})$ (A)</p> Signup and view all the answers

    What unit is used to express conductivity ($ au$)?

    <p>Siemens per meter (S/m) (D)</p> Signup and view all the answers

    Which material has the lowest conductivity according to the comparison provided?

    <p>Soda-lime glass (B)</p> Signup and view all the answers

    What does the notation $k$ refer to in thermal conductivity?

    <p>Thermal conductivity (C)</p> Signup and view all the answers

    Flashcards

    Tensile Strength

    The ability of a material to resist deformation under tensile load. Measured by the stress at the elastic limit.

    Stiffness (Modulus of Elasticity)

    The ability of a material to deform elastically under applied stress. Measured by the slope of the stress-strain curve in the elastic region.

    Elastic Limit

    The maximum stress a material can withstand before permanent deformation occurs. Beyond this point, the material will not return to its original shape.

    Ductility

    The ability of a material to deform plastically under tensile load before fracturing. Measured by the strain at fracture.

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    Hardness

    The resistance of a material to indentation or scratching. Measured by the depth of penetration of an indenter.

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    Toughness

    The energy a material can absorb before fracturing. Measured by the area under the stress-strain curve.

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    Resilience

    The ability of a material to absorb energy when deformed elastically. Measured by the area under the stress-strain curve in the elastic region.

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    Electrical Conductivity

    The ability of a material to conduct electrical current. Measured by the electrical conductivity.

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    Fracture Toughness

    Fracture toughness is a material's ability to resist breaking when a crack is present.

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    Vickers Hardness

    Vickers hardness is measured using a square pyramid-shaped indenter. The diagonal length of the indentation is measured and used to calculate the hardness number.

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    Brinell Hardness

    Brinell hardness measures a material's resistance to indentation using a hard steel or tungsten carbide ball. The diameter of the indentation is measured to determine hardness.

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    Hooke's Law

    The relationship between stress (force per unit area) and strain (deformation) in a material that undergoes elastic deformation. It states that stress is directly proportional to strain within the elastic limit.

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    Elongation

    The amount of elongation a material experiences under tension, measured as the change in length divided by the original length.

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    Modulus of Resilience

    The modulus of resilience is the area under the stress-strain curve in the elastic region.

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    Ohm's Law

    A relationship between voltage, current, and resistance in an electrical circuit. It states that the voltage drop across a conductor is directly proportional to the current flowing through it and the resistance of the conductor. Formula: V = IR.

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    Conductivity

    A material property that describes how easily an electrical current can flow through a material. It is the reciprocal of resistivity.

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    Resistivity

    A material property that describes how strongly a material resists the flow of electrical current. It is the reciprocal of conductivity.

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    Thermal Expansion Coefficient

    A measure of how much a material changes in length when its temperature changes. Measured in units of 1/K or 1/ºC.

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    Thermal Conductivity

    The rate at which heat energy is transferred through a material by conduction. Measured in units of W/m-K.

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    Electrical Conduction

    The process by which electrical current flows through a material. It depends on the availability of free electrons and the ease with which they move through the material.

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    Voltage

    The difference in electrical potential between two points in a circuit. It causes the flow of current.

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    Thermal Resistance

    The ability of a material to withstand high temperatures before permanent deformation or failure. Measured by the temperature at which the material starts to soften or melt.

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    Heat Treatment

    The process of using heat to change the structure and properties of a material. This can involve melting, solidification, or other transformations.

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    Melting Point

    The temperature at which a material changes phase, usually from solid to liquid.

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    Re-entry Temperature

    The temperature at which a material starts to soften and deform under load. It's a key indicator of a material's ability to withstand high temperatures.

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    Silica Tiles

    A composite material that has a high thermal resistance and is used in space shuttles to protect them from extreme heat during re-entry.

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    Porous Structure

    A type of material with small interconnected pores or spaces. This structure can improve thermal insulation by trapping air, which is a poor conductor of heat.

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    Bonding

    The process of bonding together fibers or particles to create a stronger and more stable material. This is often done using heat treatment.

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    Study Notes

    Lecture 2: Physical and Mechanical Properties of Materials

    • Topic: Physical and mechanical properties of materials.
    • Course: Manufacturing Technology (EIM1101)
    • Instructor: Dr. Mohamed Taha Eldaly
    • Reference Book: Materials Science and Engineering, Nine Edition, by William D. Callister, Jr. and David G. Rethwisch.
    • Course Outline: Weeks 1-16 cover topics including: introduction to manufacturing, physical and mechanical properties of materials, classification of metals and alloys, polymers and composites, metal casting, metal forming (rolling, extrusion, drawing), machining operations; tool life and materials; joining operations; shaping of plastics; and exams.

    Physical and Mechanical Properties of Materials

    • Tensile Test: A test to determine a material's response to stretching forces.
    • Stiffness: A material's resistance to deformation under stress.
    • Limit of Elasticity: The point on a stress-strain curve beyond which the material will deform permanently.
    • Ductility and Tensile Strength: Measures the material's ability to be stretched before fracturing and its ability to withstand a tensile load.
    • Hardness: A measure of a material's resistance to indentation or scratching.
    • Toughness: A measure of a material's ability to absorb energy before fracturing.
    • Resilience: A measure of a material's ability to absorb energy during elastic deformation and have it recovered upon unloading.
    • Electrical Conductivity: A measure of how easily a material allows electric current to flow through it.
    • Thermal Conductivity: A measure of how easily a material transmits heat.

    Tensile Testing Apparatus

    • Load Cell: Measures the applied load.
    • Extensometer: Measures the elongation of the specimen.
    • Moving Crosshead: Elongates the specimen.

    Hooke's Law and Stress-Strain Diagrams

    • Hooke's Law: Relates engineering stress and engineering strain for elastic deformation.
    • Stress-Strain Diagrams: Illustrate the relationship between stress and strain during loading and unloading cycles, showing both elastic and plastic behaviors, tangent and secant moduli.

    Solved Example (Copper Elongation)

    • Original Length (l₀): 305 mm
    • Stress (σ): 276 MPa
    • Young's Modulus (E): 110 x 10³ MPa
    • Resultant Elongation (Δl): 0.77 mm

    Mechanical Properties (further details)

    • Ductility (percent elongation): Measures the material's ability to deform plastically before fracture, calculated as (lf − li) / li * 100%.
    • Ductility (percent reduction in area): (Ai - Af) / Ai *100%, where Ai is initial area and Af is final area.
    • Brittle vs. Ductile: Classification of materials based on their behavior under stress.

    Hardness Testing

    • Brinell Hardness Test: Uses a hardened steel or tungsten carbide ball to indent the material.
    • Vickers Hardness Test: Uses a square-based pyramid-shaped indenter.
    • Rockwell Hardness Test: Measures the depth of indentation using a diamond or steel cone indenter.

    Electrical Properties

    • Ohm's Law: V = IR (Voltage = Current × Resistance).
    • Resistivity (ρ): A material's intrinsic resistance to current flow, independent of size or shape.
    • Conductivity (σ): Reciprocal of resistivity.

    Thermal Properties

    • Heat Capacity (C): The amount of heat required to raise the temperature of one mole of a substance by one degree.
    • Specific Heat (cp): Heat capacity per unit mass.
    • Modulus of Resilience: Energy absorbed during elastic deformation.
    • Thermal Expansion: Materials change size with temperature changes.
    • Linear coefficient of thermal expansion: Measures the change in length per unit length per degree change in temperature.

    Thermal Conductivity (k):

    • Thermal Conductivity(k): Measures the amount of heat transmitted through a material.

    Material Applications (Space Shuttle Orbiter)

    • Silica Tiles: Large-scale application in the Space Shuttle Orbiter thermal protection system, due to their high temperature resistance.

    Additional Information

    • Units: Ensure you understand the units used for each property (e.g., MPa for stress, J/mol-K for heat capacity).
    • Material Classifications: Metals, Polymers, Ceramics, Semiconductors.
    • The provided URLs are for checking for further study material on these properties.

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

    Description

    This quiz covers physical and mechanical properties of materials as outlined in Manufacturing Technology course EIM1101. Topics include tensile tests, stiffness, and the limit of elasticity. Test your understanding of these fundamental concepts from the reference book by Callister and Rethwisch.

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