A 200 × 100 × 50 mm3 steel block is subjected to a hydro-static stres...
Given,
dimension of steel block = 200×100×50mm3
σ = 15 MPa
E = 200 GPa, μ = 0.3
Bulk modulus,
E=3K(1-2μ)⇒200=3K(1-2×0.3)
K = 166.67GPa
ΔV = 90mm3
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A 200 × 100 × 50 mm3 steel block is subjected to a hydro-static stres...
To find the change in volume of the steel block, we can use the equation:
ΔV/V = -3βΔP
Where:
ΔV is the change in volume
V is the initial volume
β is the volumetric strain
ΔP is the change in hydrostatic stress
Given:
Initial dimensions of the block:
Length (L) = 200 mm
Width (W) = 100 mm
Height (H) = 50 mm
Hydrostatic stress (P) = 15 MPa = 15 N/mm²
Young’s modulus (E) = 200 GPa = 200 × 10^3 N/mm²
Poisson’s ratio (ν) = 0.3
Let's calculate the volumetric strain (β):
β = -ν(ΔL/L + ΔW/W + ΔH/H)
Since the block is subjected to a hydrostatic stress, the strain in each direction is the same. Therefore, ΔL = ΔW = ΔH.
Plugging in the values, we have:
β = -0.3(ΔL/L + ΔL/W + ΔL/H)
β = -0.3(3ΔL/L)
β = -0.9(ΔL/L)
Now, we can substitute the values into the equation to find the change in volume:
ΔV/V = -3βΔP
ΔV/(200 × 100 × 50) = -3(-0.9(ΔL/L))(15)
ΔV/(200 × 100 × 50) = 40.5(ΔL/L)
ΔV/(200 × 100 × 50) = 40.5(ΔL/200)
ΔV/(200 × 100 × 50) = 0.2025(ΔL)
Since ΔL = ΔW = ΔH, we can assume ΔL = ΔW = ΔH = Δx.
Therefore,
ΔV/(200 × 100 × 50) = 0.2025(Δx)
Simplifying further,
ΔV = 0.2025(Δx)(200 × 100 × 50)
ΔV = 0.405(Δx)(10^6)
The change in volume is given by ΔV = (Δx)^3.
So, (Δx)^3 = 0.405(Δx)(10^6)
Simplifying further,
(Δx)^2 = 0.405(10^6)
Δx = √(0.405(10^6))
Δx ≈ 900
Therefore, the change in volume of the steel block is approximately 900 mm³.
Hence, the correct answer is option 'B' (90).