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A concrete cylinder of diameter 150 mm and length 300 mm when subjected to an axial compressive load of 248 kN if result in an increase of diameter by 0.127 mm and an decrease of 0.3 mm compute the value of Poisson ratio and modulus of elasticity.

Physics

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Answer

Poisson’s ratio≈0.847\text{Poisson's ratio} \approx 0.847

Modulus of elasticity≈14.0 GPa\text{Modulus of elasticity} \approx 14.0 \text{ GPa}

Step-by-step solution

6 steps

let's compute the Poisson's ratio and modulus of elasticity.

  1. Convert all given values to SI units (meters and Newtons).

    Original diameter, D=150 mm=0.150 mD = 150 \text{ mm} = 0.150 \text{ m}
    Original length, L=300 mm=0.300 mL = 300 \text{ mm} = 0.300 \text{ m}
    Compressive load, F=248 kN=248×103 NF = 248 \text{ kN} = 248 \times 10^3 \text{ N}
    Increase in diameter, ΔD=0.127 mm=0.127×10−3 m\Delta D = 0.127 \text{ mm} = 0.127 \times 10^{-3} \text{ m}
    Decrease in length, ΔL=0.3 mm=0.3×10−3 m\Delta L = 0.3 \text{ mm} = 0.3 \times 10^{-3} \text{ m}

  2. Calculate the longitudinal strain (ϵL\epsilon_L) and lateral strain (ϵD\epsilon_D).

    Longitudinal strain is the change in length divided by the original length. Since it's a decrease, we use a negative sign for the change in length.

    ϵL=ΔLL=−0.3×10−3 m0.300 m=−0.001\epsilon_L = \frac{\Delta L}{L} = \frac{-0.3 \times 10^{-3} \text{ m}}{0.300 \text{ m}} = -0.001

    Lateral strain is the change in diameter divided by the original diameter. Since it's an increase, it's positive.

    ϵD=ΔDD=0.127×10−3 m0.150 m≈0.00084667\epsilon_D = \frac{\Delta D}{D} = \frac{0.127 \times 10^{-3} \text{ m}}{0.150 \text{ m}} \approx 0.00084667
  3. Compute Poisson's ratio (ν\nu).

    Poisson's ratio is the negative ratio of lateral strain to longitudinal strain.

    ν=−ϵDϵL=−0.00084667−0.001=0.84667\nu = -\frac{\epsilon_D}{\epsilon_L} = -\frac{0.00084667}{-0.001} = 0.84667

    Rounding to three significant figures:

    Poisson’s ratio≈0.847\boxed{\text{Poisson's ratio} \approx 0.847}
  4. Calculate the cross-sectional area (AA) of the cylinder.

    A=πD24=π(0.150 m)24=π×0.0225 m24≈0.017671 m2A = \frac{\pi D^2}{4} = \frac{\pi (0.150 \text{ m})^2}{4} = \frac{\pi \times 0.0225 \text{ m}^2}{4} \approx 0.017671 \text{ m}^2
  5. Calculate the compressive stress (σ\sigma).

    Stress is the force divided by the cross-sectional area.

    σ=FA=248×103 N0.017671 m2≈14033900 Pa\sigma = \frac{F}{A} = \frac{248 \times 10^3 \text{ N}}{0.017671 \text{ m}^2} \approx 14033900 \text{ Pa}
  6. Compute the modulus of elasticity (EE).

    The modulus of elasticity (Young's modulus) is the ratio of stress to the magnitude of longitudinal strain.

    E=σ∣ϵL∣=14033900 Pa0.001=14033900000 PaE = \frac{\sigma}{|\epsilon_L|} = \frac{14033900 \text{ Pa}}{0.001} = 14033900000 \text{ Pa}

    Converting to GigaPascals (GPa):

    E=14.0339 GPaE = 14.0339 \text{ GPa}

    Rounding to three significant figures:

    Modulus of elasticity≈14.0 GPa\boxed{\text{Modulus of elasticity} \approx 14.0 \text{ GPa}}
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