Strength of Materials
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Questions and Answers

What type of material exhibits linear elastic behavior followed by plastic response?

  • Perfectly plastic material
  • Elasto-plastic material (correct)
  • Elastic material
  • Plastic material

    • What happens to the strain when the stress applied on a specimen is increased, in a material that exhibits linear elastic behavior?

  • The strain remains unchanged
  • The strain decreases
  • The strain remains constant
  • The strain increases proportionally (correct)

    • What is the characteristic of a material that exhibits plastic response?

  • The material exhibits a linear stress-strain relationship
  • The material deforms permanently under stress (correct)
  • The material has a high modulus of elasticity
  • The material retains its original shape after the removal of the load

    • What is the typical shape of the stress-strain curve of a plastic material?

    <p>Non-linear</p> Signup and view all the answers

    What is the yield strength of the aluminum alloy in the example?

    <p>150 MPA</p> Signup and view all the answers

    What is the change in gauge length of the rod after applying the tensile load?

    <p>0.1 mm</p> Signup and view all the answers

    What is the definition of elastic materials?

    <p>Materials that have the ability to recover their original shape after removal of the load</p> Signup and view all the answers

    What is the purpose of drawing a stress-strain curve?

    <p>To analyze the behavior of a material under different types of loading</p> Signup and view all the answers

    What is the formula for Young's modulus?

    <p>E = σ / ε</p> Signup and view all the answers

    What is the definition of plastic materials?

    <p>Materials that cannot recover their original shape after removal of the load</p> Signup and view all the answers

    What type of material is concrete?

    <p>Elasto-plastic material</p> Signup and view all the answers

    What is the unit of Young's modulus?

    <p>Pa</p> Signup and view all the answers

    What is the relationship between stress and strain in the elastic region of a stress-strain curve?

    <p>Stress is directly proportional to strain</p> Signup and view all the answers

    What is the effect of increasing Young's modulus on a material?

    <p>It becomes more difficult to deform</p> Signup and view all the answers

    What is Poisson's ratio?

    <p>A measure of a material's ability to deform laterally</p> Signup and view all the answers

    What is the normal strain in the given example?

    <p>0.025/50</p> Signup and view all the answers

    What is the normal stress in the given example?

    <p>8 KN</p> Signup and view all the answers

    What is the change in diameter of the steel bar in the given example?

    <p>0.0015 mm</p> Signup and view all the answers

    What is the primary factor that determines the response of a material to loads?

    <p>Properties of the material</p> Signup and view all the answers

    What is the unit of stress?

    <p>MPa</p> Signup and view all the answers

    What is the formula for calculating stress?

    <p>P / A</p> Signup and view all the answers

    What type of stress occurs when a force is applied parallel to a surface?

    <p>Shear stress</p> Signup and view all the answers

    What is the definition of strain?

    <p>Change in length divided by original length</p> Signup and view all the answers

    What is the dimension of strain?

    <p>Length/Length</p> Signup and view all the answers

    What is the formula for calculating strain?

    <p>ΔL / L</p> Signup and view all the answers

    What is the importance of considering the mechanical properties of building materials?

    <p>To ensure durability and resistance to failure</p> Signup and view all the answers

    What is the term for the ability of a material to resist failure under the action of stresses?

    <p>Strength</p> Signup and view all the answers

    What type of strain is the strain that subsides after the removal of the applied stress?

    <p>Elastic strain</p> Signup and view all the answers

    What is the stress range that does not cause plastic strain?

    <p>Elastic range</p> Signup and view all the answers

    What is the maximum stress that can be applied on a material before it fails?

    <p>Ultimate stress</p> Signup and view all the answers

    What is the ability of a material to endure alternate wet and dry conditions for a long period without considerable deformation and loss of mechanical strength?

    <p>Weathering Resistance</p> Signup and view all the answers

    What is the capacity of a material to allow water to penetrate under pressure?

    <p>Water Permeability</p> Signup and view all the answers

    What is the ability of a water-saturated material to endure repeated freezing and thawing with considerable decrease of mechanical strength?

    <p>Frost Resistance</p> Signup and view all the answers

    What is the increase in stresses by an increase in strain without collapse in the material?

    <p>Strain Hardening</p> Signup and view all the answers

    A material with a stress-strain relation has a modulus of elasticity of 2510^6 Psi, yield strength of 70 ksi, and the slope of hardening portion of the stress-strain diagram is 310^6 psi. What is the strain that corresponds to a stress of 80 ksi?

    <p>3.2%</p> Signup and view all the answers

    A steel rod is subjected to an axial pulling force of 50 kN. Its diameter is 30 mm and it is 3 m long. What is the percentage of elongation of the steel rod?

    <p>1.0%</p> Signup and view all the answers

    What is the primary characteristic of fire resistance in a material?

    <p>Ability to resist high temperature without deformation and loss of strength</p> Signup and view all the answers

    Which property of a material is related to its ability to resist abrasion?

    <p>Abrasive resistance</p> Signup and view all the answers

    What is the unit of the abrasion ratio (N) in the given formula?

    <p>gm/cm2</p> Signup and view all the answers

    What is the term for the ability of a material to resist the action of acids, alkalis, seawater, and gases?

    <p>Chemical resistance</p> Signup and view all the answers

    What is the term for the ability of a material to resist the combined effects of atmospheric and other factors?

    <p>Durability</p> Signup and view all the answers

    What is the term for the property of a material to resist pressing-in or scratch of a sharp object?

    <p>Hardness</p> Signup and view all the answers

    What is the formula for calculating the abrasion ratio (N)?

    <p>N = (m1 - m2)/A</p> Signup and view all the answers

    What is the purpose of calculating the abrasion ratio (N)?

    <p>To determine the abrasive resistance of a material</p> Signup and view all the answers

    What is the term for the ability of a material to resist deformation and substantial loss of strength under high temperature?

    <p>Fire resistance</p> Signup and view all the answers

    Study Notes

    Mechanical Properties of Building Materials

    • Materials deform in response to loads, and their specific response depends on properties, load magnitude and type, and element geometry.
    • Important mechanical properties of building materials include strength, compressive, tensile, bending, impact, hardness, plasticity, elasticity, and abrasion resistance.
    • Strength of materials is the ability to resist failure under stress caused by loads, including compression, tension, bending, and impact.

    Stress and Strain

    • Stress (σ) is the amount of force applied to a unit of area (N/mm²) and is defined as load (P) divided by area (A).
    • Strain (ε) is the amount of deformation per unit length of an object when a load is applied and is defined as change in length (ΔL) divided by original length (L).
    • Strain is dimensionless and has dimensions of [Length]/[Length].

    Types of Stress

    • There are several types of stress, including compression stress, tension stress, shear stress, and torsion stress.

    Classification of Building Materials

    • Materials can be classified according to their nature of deformation:
      • Elastic materials: recover their original shape after removal of the load (e.g. rubber).
      • Plastic materials: cannot recover their original shape after removal of the load (e.g. clay).
      • Elasto-plastic materials: recover part of the changes in their shape after removal of the load (e.g. steel, concrete, and wood).

    Modulus of Elasticity

    • Young's modulus (E) is a measure of the ability to resist deformation and is defined as the proportional constant between normal stress and normal strain.
    • The modulus of elasticity is a measure of a material's stiffness and is calculated as σ / ε.
    • The bigger the modulus of elasticity, the more difficult it is for a material to deform.

    Poisson's Ratio

    • Poisson's ratio (V) is a measure of the lateral strain to the longitudinal strain of a material.
    • Poisson's ratio is calculated as the change in diameter divided by the original diameter.

    Material Properties

    • Weathering resistance is the ability of a material to endure alternate wet and dry conditions without considerable deformation and loss of mechanical strength.
    • Water permeability is the capacity of a material to allow water to penetrate under pressure.
    • Frost resistance is the ability of a water-saturated material to endure repeated freezing and thawing with considerable decrease of mechanical strength.
    • Fire resistance is the ability of a material to resist the action of high temperature without appreciable deformation and substantial loss of strength.
    • Chemical resistance is the ability of a material to withstand the action of acids, alkalis, seawater, and gases.
    • Durability is the ability of a material to resist the combined effects of atmospheric and other factors.
    • Hardness refers to the property of a material to resist pressing-in or scratch of a sharp object.
    • Abrasive resistance refers to the capacity of a material to resist abrasion and is expressed by the abrasion ratio.

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