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Steel Specifications and Compositions Quiz
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Steel Specifications and Compositions Quiz

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Questions and Answers

What is a characteristic feature of ductile materials compared to brittle materials?

  • Ductile materials have a lower toughness than brittle materials.
  • Ductile materials are always stronger than brittle materials.
  • Ductile materials show significant plastic deformation before failure. (correct)
  • Ductile materials fracture at lower stress levels.

    • Which theory of failure primarily accounts for multi-axial stress states?

  • Von Mises theory (correct)
  • Tresca theory
  • Mohr's Circle theory
  • Hooke's Law

    • What is the main variable affecting fatigue strength as represented in the S-N diagram?

  • Fatigue limit
  • Load frequency
  • Mean stress (correct)
  • Material density

    • Which of the following tools is commonly used to design welded pressure vessels?

    <p>ASME code</p> Signup and view all the answers

    In the context of stress concentration, which geometric feature is likely to amplify stress in a shaft?

    <p>An abrupt change in diameter</p> Signup and view all the answers

    What is the main purpose of the factor of safety in mechanical design?

    <p>To account for uncertainties in load and material properties.</p> Signup and view all the answers

    What is a characteristic of fatigue under low cycle conditions?

    <p>It generally leads to failure at relatively low numbers of cycles.</p> Signup and view all the answers

    What is the primary concern when designing threaded fasteners under dynamic loading conditions?

    <p>Initial tension in the bolt.</p> Signup and view all the answers

    What is the yield strength of FeE 250 steel?

    <p>250 MPa</p> Signup and view all the answers

    What percentage of carbon is present in specification 25Cr4Mo2?

    <p>0.25%</p> Signup and view all the answers

    Which element is associated with a factor of 100 in alloy steels?

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

    What is the percentage composition of manganese in 20C12Pb15?

    <p>1.2%</p> Signup and view all the answers

    In high alloy steels, what is the carbon percentage in the specification X15Cr25Ni12?

    <p>0.15%</p> Signup and view all the answers

    Which of the following elements is indicated to enhance strength in medium alloy steels with a factor of 10?

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

    What is the tensile strength specified for Fe 360 steel?

    <p>360 MPa</p> Signup and view all the answers

    How many types of loads can mechanical components be subjected to, according to the content?

    <p>Multiple types simultaneously</p> Signup and view all the answers

    What is the required diameter of the shaft with an ultimate tensile strength of 400 MPa and a factor of safety of 2?

    <p>80 mm</p> Signup and view all the answers

    How does the thickness 't' of a member with a 50 mm hole relate to the maximum allowable stress compared to a solid member?

    <p>It must be significantly lower than the original member's thickness.</p> Signup and view all the answers

    What is the maximum stress experienced in a section of a shaft with a 2.5 mm transverse hole and a bending moment of 1.5 kNm?

    <p>200 MPa</p> Signup and view all the answers

    What effect does the transverse hole have on the section's stress concentration factor and maximum stress?

    <p>It increases the stress concentration factor.</p> Signup and view all the answers

    If the hole was not present in the shaft, what would be the expected factor of safety (FOS) for the same bending moment of 1.5 kNm in a hot rolled carbon steel material?

    <p>2.0</p> Signup and view all the answers

    What is the factor of safety applied for the mild steel shaft in the bending moment scenario?

    <p>3.5</p> Signup and view all the answers

    What is the yield point strength of the mild steel used for the shaft?

    <p>300 MPa</p> Signup and view all the answers

    Which theory is used to determine the maximum torque that causes failure of the shaft?

    <p>Mises von Henky theory</p> Signup and view all the answers

    What is the tensile strength of the plane carbon steel 45C8 used for the crank shaft?

    <p>380 MPa</p> Signup and view all the answers

    What is a key limitation of conventional design equations for stress?

    <p>They assume uniform cross-section without discontinuities.</p> Signup and view all the answers

    What phenomenon occurs due to the presence of discontinuities in a component's cross-section?

    <p>Stress concentration</p> Signup and view all the answers

    In the photo-elasticity technique, what is used to observe stress distribution?

    <p>Photo-elastic model</p> Signup and view all the answers

    What effect is observed near a circular hole in a plate subjected to tensile stress?

    <p>Increase in stress concentration</p> Signup and view all the answers

    What does the maximum principal strain theory indicate about failure?

    <p>Failure occurs when the maximum principal strain equals the strain at yield point.</p> Signup and view all the answers

    In total strain energy theory, what condition leads to failure?

    <p>Total strain energy per unit volume equals the yield strain energy per unit volume.</p> Signup and view all the answers

    What formula represents the failure condition in the maximum principal strain theory?

    <p>$ au_{yp} = au_1 - u au_2$</p> Signup and view all the answers

    Which aspect is not considered in total strain energy theory?

    <p>The total volume of the material.</p> Signup and view all the answers

    Under what condition does failure occur in a bi-axial stress scenario according to principal strain theory?

    <p>$ au_{yp} = au_1 - u au_2$</p> Signup and view all the answers

    What is the significance of Poisson's ratio in determining failure according to the theories of failure?

    <p>It affects the relationship between axial and lateral strains.</p> Signup and view all the answers

    What happens when the total strain energy exceeds the yield point energy according to Haigh's theory?

    <p>The component is likely to fail.</p> Signup and view all the answers

    When determining root diameter of a bolt, what is a key factor that needs to be considered?

    <p>Complex loading conditions experienced by the bolt.</p> Signup and view all the answers

    Study Notes

    Steel Specifications

    • Fe 360 has a tensile strength of 360 MPa.
    • FeE 250 has a yield strength of 250 MPa.

    Plain Carbon Steel Composition

    • 55C4: Carbon 0.55%, Manganese 0.4%.
    • 40C8: Carbon range 0.35-0.45%, Manganese range 0.7-0.9%.

    Free Cutting Steel Composition

    • 25C12S14: Carbon 0.25%, Manganese 1.2%, Sulphur 0.14%.
    • 20C12Pb15: Carbon 0.2%, Manganese 1.2%, Lead 0.15%.
    • Elements like S, Pb, Se, Te may be included based on presence.

    Low & Medium Alloy Steels

    • Total alloying elements must not exceed 10%.
    • Significant alloying elements and their factors include:
      • Cr, Co, Ni, Mn, Si, W: factor 4.
      • Al, Be, V, Pb, Cu, Nb, Ti, Ta, Zr, Mo: factor 10.
      • P, S, N: factor 100.
    • Example:
      • 25Cr4Mo2: Carbon 0.25%, Chromium 1%, Molybdenum 0.2%.
      • 40Ni8Cr8V2: Carbon 0.4%, Nickel 2%, Chromium 2%, Vanadium 0.2%.

    High Alloy Steels

    • Total alloying elements exceed 10%.
    • Example: X15Cr25Ni12 comprises Carbon 0.15%, Chromium 25%, Nickel 12%.

    Principal Stresses and Theories of Failure

    • Mechanical components can be subjected to multiple loading types.
    • Theories of failure include:
      • Maximum principal stress theory.
      • Maximum principal strain theory (St. Venant’s theory).
      • Total strain energy theory (Haigh’s theory).

    Stress Concentration

    • Stress concentration arises from geometric discontinuities or irregularities in components.
    • This leads to localized high stresses, often significantly higher than theoretical predictions.
    • An experimental method for evaluating stress distribution uses photoelasticity, displaying stress distributions around holes.

    Mechanical Design Concepts

    • Ductile vs. brittle fracture descriptions.
    • Key stress-related phenomena: strain energy, toughness, hardness, creep.
    • Load types: axial, bending, torsional.
    • Design applications involving shafts, keys, riveted joints, welded joints, threaded fasteners, and power screws.

    Practical Applications

    • Calculations involving principal stresses, shear stresses, and dimensions of structural elements are critical for design safety.
    • Commonly assessed factors include yield strengths, factors of safety, and maximum torque limits when analyzing structural integrity.

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    Related Documents

    1. Introduction.pdf

    Description

    Test your knowledge on various steel specifications and compositions, including plain carbon steels and alloy steels. This quiz covers tensile and yield strengths, composition percentages, and classification of steels based on alloying elements. Perfect for materials science students and professionals alike.

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