All questions of Thin & Thick Cylinders for Civil Engineering (CE) Exam

A thin cylindrical shell of diameter 200 mm, thickness 8 mm is held between two rigid supports as shown in figure. An internal pressure of 5 N/mm2 is applied on the inner surface of the cylinder. The resultant axial stresses developed in the cylinder (μ = 0.35) is _________MPa
(A) 21.0
(B) 22.5
    Correct answer is option ''. Can you explain this answer?

    Neha Joshi answered
    Stresses developed
    σc = = 62.5 N/mm2
    σa = = 31.25 N/mm2
    Due to rigid end supports, axial strain, εa = 0 Say σa′ is axial compressive stress provided by rigid end supports.
    Resultant axial stress, σaR = 31.25 − σa
    Axial strain, εa = = 0
    Or 31.25 − σa′ − 0.35(62.5) = 0
    σa′ = 31.25 − 21.875
    = 9.375 N/mm2
    Resultant axial stress, σaR = 31.25 − 9.375 = 21.875 N/mm2
    Question_Type: 5

    In thin cylinder, circumferential stress is x times longitudinal stress, where x is
    • a)
      0.5
    • b)
      1
    • c)
      2
    • d)
      0.2
    Correct answer is option 'C'. Can you explain this answer?

    Anu Deshpande answered
    Explanation:

    Thin Cylinder:
    - A thin cylinder is a cylindrical structure with a relatively small wall thickness compared to its radius.
    - The wall of a thin cylinder is subjected to both longitudinal stress (along the length of the cylinder) and circumferential stress (around the circumference of the cylinder).

    Circumferential Stress vs Longitudinal Stress:
    - In a thin cylinder, the circumferential stress (σ_c) is related to the longitudinal stress (σ_l) by a factor x.
    - The relationship between circumferential stress and longitudinal stress in a thin cylinder can be expressed as: σ_c = xσ_l.

    Understanding x:
    - The factor x indicates how much greater the circumferential stress is compared to the longitudinal stress in a thin cylinder.
    - For a thin cylinder, x is equal to 2, which means that the circumferential stress is twice the longitudinal stress.
    - Therefore, the correct answer is option 'C' which states that x = 2.

    A bronze cylinder of diameter 200 mm, wall thickness 8 mm is wound with steel wire of diameter 4 mm under initial tension of 20 N/mm2. The wire wound cylinder is subjected to internal pressure p such that resultant hoop and axial stresses developed in the cylinder are the same. What is the magnitude of p? Given Ew = 210 GPa, EC = 105 GPa, νc = 0.35.
    • a)
      4.58 MPa
    • b)
      2.32 MPa
    • c)
      9.16 MPa
    • d)
      3.26 MPa
    Correct answer is option 'A'. Can you explain this answer?

    Zoya Sharma answered
    Σw = 20 N/mm2 dw = 4mm t = 8 mm
    σc = Initial compressive stress in cylinder
    =
    = 7.854 N/mm2 (comp. )
    Say internal pressure = P
    Axial stress, σa′ = = 6.25 P
    Hoop stress = σc
    σCR = (σc′ − 7.854) = 6.25 P, (as given) ⋯ ①
    or σc′ = 6.25 P + 7.854 ⋯ ②
    Using equilibrium and compatibility conditions
    Pd = 2tσc′ +
    From equation ④
    σc′ − νcσ′c = σ′w ×
    or 6.25 P + 7.854 − 0.35 (6.25 P) = 0.5 σw
    or 4.0625 P + 7.854 = 0.5 σw
    σw′ = 8.125 P + 15.708
    Putting the values σw′ and σc′ in equation ③
    P × 200 = 2 × 8 × (6.25p + 7.854) + × (8.125p + 15.708)
    200P = 100P + 125.664 + 6.283(8.125p + 15.708)
    100P = 125.664 + 51.05P + 98.69
    48.95 P = 224.354
    P = 4.58 N/mm2

    A closed pressure vessel of diameter 120 mm, wall thickness 4 mm is subjected to an internal pressure of 6 N/mm2. The normal stress on an element of cylindrical wall at 30° to the longitudinal axis of cylinder is __________MPa
    (A) 78.0
    (B) 79.6
      Correct answer is option ''. Can you explain this answer?

      Avinash Sharma answered
      Element ab is inclined at an angle of 30° to the axis 00 of the cylinder
      Hoop stress,
      σc = = 90 N/mm2
      Axial stress, σa = =45 N/mm2
      Stress on element Normal stress,
      σθ =
      =
      =67.5 + 11.25 = 78. 75 N/mm2
      Question_Type: 5

      A thin cylinder of radius r and thickness t when subjected to an internal hydrostatic pressure P causes a radial displacement u, then the tangential strain caused is
      • a)
        du/dr
      • b)
        1/r du/dr
      • c)
        u/r
      • d)
        2u/r
      Correct answer is option 'C'. Can you explain this answer?

      Neha Joshi answered
      The thin walled pressure vessel expands when it is internally pressurized. This results in three principal strains, the circumferential strain (εc) or tangential strain in two perpendicular plane directions, and the radial strain εr .
      Referring to the figure which shows strain of an element at the surface of the cylinder, we can write.
      εc =
      and εr =
      To determine the amount by which the vessel expands, consider a circumference at radius r and which moves out with a displacementδr. From the definition of normal strain,
      εc =
      here δr = u
      ⇒ εc =
      This is the circumferential strain.

      A thin cylinder 150 mm internal diameter and 2.5 mm thick has its ends closed by rigid plates and is then filled with water under pressure. When an axial pull of 37 kN is applied to the ends, water pressure is observed to fall by 0.1 N/mm2. The Poisson’s ratio will be (Assume E = 140000 N/mm2, K for water = 2200 N/mm2)
      • a)
        0.31
      • b)
        0.28
      • c)
        0.25
      • d)
        0.36
      Correct answer is option 'A'. Can you explain this answer?

      Neha Joshi answered
      Δp = 0.1 N/mm2
      Reduction in volumetric strain of cylinder
      =
      Reduction in volumetric strain of water
      =
      Axial force = 37000 N
      Axial stress =
      =
      = 31.406 N/mm2
      Increase in volumetric strain due to pull
      =
      Or
      =
      Or 1.5(5 − 4ν) +
      = 31.406 (1 − 2ν)
      7.5 − 6ν + 6.3636 = 31.406 − 62.812ν
      Or 56.812 ν = 31.406 − 6.3636 − 7.5
      = 17.5424
      Poisson’s ratio,
      ν = = 0.308

      A thin cylindrical shell made of steel, of diameter 250 mm, wall thickness 6 mm, length 1 m is subjected to internal pressure p such that maximum stress developed in the shell is 120 MPa. If E = 200 GPa and Poisson’s ratio is 0.3. The change in volume of the shell is ___________ cm3
       
      • a)
        55.5
      • b)
        56.5
      • c)
        55.96
      • d)
        none 
      Correct answer is option 'C'. Can you explain this answer?

      Avinash Sharma answered
      Maximum stress,
      σc = = = 120 N/mm2
      P= = 5.76 N/mm2
      E = 200000 N/mm2 , ν = 0.3
      Axial strain,
      εa =
      =
      = 1.2 × 10−4
      Circumferential strain,
      εc =
      =
      = 5.1 × 10−4
      Volumetric strain, εv = 2εc + εa
      = 2 × 5.1 × 10−4 + 1.2 × 10−4
      = 11.4 × 10−4
      Original volume,
      V =
      =
      = 49.0874 × 106 mm3
      Change in volume, δV = εv × V
      = 11.4 × 10−4 × 49.0874 × 106
      = 55960 mm3 = 55.96 cm3
      = 55.96 cc
      Question_Type: 5

      Maximum value of shear stress in thin cylinders is equal to
      • a)
        2 (hoop stress)
      • b)
        0.5 (hoop stress)
      • c)
        Hoop stress
      • d)
        0.25 (hoop stress)
      Correct answer is option 'D'. Can you explain this answer?

      Pk Academy answered
        For a thin-walled cylinder with internal pressure:
        Hoop Stress (σₕ) acts around the circumference. Longitudinal Stress (σ_L) acts along the length, which is half of σₕ, so σ_L = σₕ⁄2.
        Maximum shear stress (τ_max) is calculated as (σₕ - σ_L)⁄2. Substituting σ_L:
        τ_max = (σₕ - σₕ⁄2)⁄2 = σₕ⁄4.
        Thus, the maximum shear stress is 0.25 times the hoop stress.
        Answer:
        d) 0.25 (hoop stress)

           
         

        If the hoop strain and longitudinal strain in case of a thin cylindrical shell are eh and et then volumetric strain is
        • a)
          eh + et
        • b)
          eh + 2et
        • c)
          2 (eh + et)
        • d)
          2eh + et
        Correct answer is option 'D'. Can you explain this answer?

        Amar Desai answered
        Explanation:
        When a thin cylindrical shell undergoes deformation, it experiences hoop strain (eh) and longitudinal strain (et). The volumetric strain is the sum of these two strains and can be calculated as follows:

        Volumetric strain = eh + et

        However, this formula only holds for isotropic materials. In the case of non-isotropic materials, the volumetric strain can be calculated using the following formula:

        Volumetric strain = 2eh + et

        This is because the material may have different properties in the hoop and longitudinal directions, resulting in different levels of deformation in each direction.

        Therefore, in the given question, since we are dealing with a thin cylindrical shell which is a non-isotropic material, the correct answer is option D, which is 2eh - et.

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