Identify given parameters and relationships.

Physics

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Answer

125.21 mm\text{125.21 mm}

18.10 kN⋅m\text{18.10 kN}\cdot\text{m}

379.80 kW\text{379.80 kW}

Step-by-step solution

5 steps
  1. Identify given parameters and relationships.

    The given parameters are:

    • Inner diameter of bronze sleeve (and outer diameter of steel shaft), di=ds=80 mm=0.08 md_i = d_s = 80 \, \text{mm} = 0.08 \, \text{m}.
    • Torque carried by bronze sleeve Tb=2TsT_b = 2 T_s.
    • Shear modulus of steel Gs=2.5GbG_s = 2.5 G_b.
    • Maximum allowable shear stress in steel τs,max=60 MPa=60×106 Pa\tau_{s, max} = 60 \, \text{MPa} = 60 \times 10^6 \, \text{Pa}.
    • Maximum allowable shear stress in bronze τb,max=40 MPa=40×106 Pa\tau_{b, max} = 40 \, \text{MPa} = 40 \times 10^6 \, \text{Pa}.
    • Rotation speed N=200 r/minN = 200 \, \text{r/min}.
  2. Calculate the outside diameter of the sleeve (dod_o).

    For a compound shaft, the angle of twist per unit length (θ\theta) is the same for both components:

    TsGsJs=TbGbJb\frac{T_s}{G_s J_s} = \frac{T_b}{G_b J_b}

    Substitute the given relationships Tb=2TsT_b = 2 T_s and Gs=2.5GbG_s = 2.5 G_b:

    Ts2.5GbJs=2TsGbJb\frac{T_s}{2.5 G_b J_s} = \frac{2 T_s}{G_b J_b} 12.5Js=2Jb\frac{1}{2.5 J_s} = \frac{2}{J_b} Jb=5JsJ_b = 5 J_s

    The polar moment of inertia for a solid shaft is J=π32d4J = \frac{\pi}{32} d^4. For a hollow shaft, J=π32(do4−di4)J = \frac{\pi}{32} (d_o^4 - d_i^4).
    For the steel shaft (solid): Js=π32ds4J_s = \frac{\pi}{32} d_s^4.
    For the bronze sleeve (hollow): Jb=π32(do4−di4)J_b = \frac{\pi}{32} (d_o^4 - d_i^4).
    Substitute these into Jb=5JsJ_b = 5 J_s:

    π32(do4−di4)=5π32ds4\frac{\pi}{32} (d_o^4 - d_i^4) = 5 \frac{\pi}{32} d_s^4 do4−di4=5ds4d_o^4 - d_i^4 = 5 d_s^4

    Since di=dsd_i = d_s:

    do4−ds4=5ds4d_o^4 - d_s^4 = 5 d_s^4 do4=6ds4d_o^4 = 6 d_s^4 do=(6)1/4dsd_o = (6)^{1/4} d_s

    Substitute ds=80 mmd_s = 80 \, \text{mm}:

    do=(6)1/4×80 mm≈1.56508×80 mmd_o = (6)^{1/4} \times 80 \, \text{mm} \approx 1.56508 \times 80 \, \text{mm} do≈125.206 mmd_o \approx 125.206 \, \text{mm}

    The outside diameter of the sleeve is 125.21 mm\boxed{\text{125.21 mm}}.

  3. Determine the limiting shear stress and calculate individual torques.

    The shear stress in a shaft is given by τ=TrJ\tau = \frac{Tr}{J}. For the maximum stress, rr is the outermost radius.
    For the steel shaft: τs=Ts(ds/2)Js=Ts(ds/2)π32ds4=16Tsπds3\tau_s = \frac{T_s (d_s/2)}{J_s} = \frac{T_s (d_s/2)}{\frac{\pi}{32} d_s^4} = \frac{16 T_s}{\pi d_s^3}.
    For the bronze sleeve: τb=Tb(do/2)Jb=Tb(do/2)π32(do4−di4)=16Tbdoπ(do4−di4)\tau_b = \frac{T_b (d_o/2)}{J_b} = \frac{T_b (d_o/2)}{\frac{\pi}{32} (d_o^4 - d_i^4)} = \frac{16 T_b d_o}{\pi (d_o^4 - d_i^4)}.
    From Step 2, we know Tb=2TsT_b = 2 T_s, do=(6)1/4dsd_o = (6)^{1/4} d_s, and do4−di4=5ds4d_o^4 - d_i^4 = 5 d_s^4.
    Let's find the ratio of the stresses:

    τbτs=16Tbdoπ(do4−di4)16Tsπds3=Tbdods3Ts(do4−di4)\frac{\tau_b}{\tau_s} = \frac{\frac{16 T_b d_o}{\pi (d_o^4 - d_i^4)}}{\frac{16 T_s}{\pi d_s^3}} = \frac{T_b d_o d_s^3}{T_s (d_o^4 - d_i^4)}

    Substitute the relationships:

    τbτs=(2Ts)((6)1/4ds)ds3Ts(5ds4)=2(6)1/45\frac{\tau_b}{\tau_s} = \frac{(2 T_s) ((6)^{1/4} d_s) d_s^3}{T_s (5 d_s^4)} = \frac{2 (6)^{1/4}}{5} τbτs≈2×1.565085≈0.626032\frac{\tau_b}{\tau_s} \approx \frac{2 \times 1.56508}{5} \approx 0.626032

    So, τb≈0.626032τs\tau_b \approx 0.626032 \tau_s.
    Now, check which material limits the torque:

    • If τs=τs,max=60 MPa\tau_s = \tau_{s, max} = 60 \, \text{MPa}, then τb=0.626032×60 MPa≈37.56 MPa\tau_b = 0.626032 \times 60 \, \text{MPa} \approx 37.56 \, \text{MPa}. This is less than τb,max=40 MPa\tau_{b, max} = 40 \, \text{MPa}, so it is acceptable.
    • If τb=τb,max=40 MPa\tau_b = \tau_{b, max} = 40 \, \text{MPa}, then τs=40 MPa0.626032≈63.89 MPa\tau_s = \frac{40 \, \text{MPa}}{0.626032} \approx 63.89 \, \text{MPa}. This is greater than τs,max=60 MPa\tau_{s, max} = 60 \, \text{MPa}, so it is not acceptable. Therefore, the maximum torque is limited by the steel shaft reaching its maximum allowable shear stress, τs=60 MPa\tau_s = 60 \, \text{MPa}.

    Calculate the torque carried by the steel shaft (TsT_s):

    Ts=πds3τs16=π(0.08 m)3(60×106 Pa)16T_s = \frac{\pi d_s^3 \tau_s}{16} = \frac{\pi (0.08 \, \text{m})^3 (60 \times 10^6 \, \text{Pa})}{16} Ts=π×0.000512 m3×60×106 Pa16=1920π N⋅mT_s = \frac{\pi \times 0.000512 \, \text{m}^3 \times 60 \times 10^6 \, \text{Pa}}{16} = 1920 \pi \, \text{N} \cdot \text{m} Ts≈6031.858 N⋅mT_s \approx 6031.858 \, \text{N} \cdot \text{m}

    Calculate the torque carried by the bronze sleeve (TbT_b):

    Tb=2Ts=2×1920π N⋅m=3840π N⋅mT_b = 2 T_s = 2 \times 1920 \pi \, \text{N} \cdot \text{m} = 3840 \pi \, \text{N} \cdot \text{m} Tb≈12063.716 N⋅mT_b \approx 12063.716 \, \text{N} \cdot \text{m}
  4. Calculate the total torque that may be transmitted (TtotalT_{total}).

    The total torque is the sum of the torques carried by each component:

    Ttotal=Ts+Tb=1920π N⋅m+3840π N⋅m=5760π N⋅mT_{total} = T_s + T_b = 1920 \pi \, \text{N} \cdot \text{m} + 3840 \pi \, \text{N} \cdot \text{m} = 5760 \pi \, \text{N} \cdot \text{m} Ttotal≈18095.574 N⋅mT_{total} \approx 18095.574 \, \text{N} \cdot \text{m}

    The torque that may be transmitted is 18.10 kN⋅m\boxed{\text{18.10 kN}\cdot\text{m}}.

  5. Calculate the power transmitted.

    First, convert the rotation speed from r/min to rad/s:

    N=200 r/min=20060 r/s=103 r/sN = 200 \, \text{r/min} = \frac{200}{60} \, \text{r/s} = \frac{10}{3} \, \text{r/s}

    The angular velocity ω\omega is:

    ω=2πN=2π×103 rad/s=20π3 rad/s\omega = 2 \pi N = 2 \pi \times \frac{10}{3} \, \text{rad/s} = \frac{20 \pi}{3} \, \text{rad/s} ω≈20.94395 rad/s\omega \approx 20.94395 \, \text{rad/s}

    The power transmitted PP is given by P=TtotalωP = T_{total} \omega:

    P=(5760π N⋅m)×(20π3 rad/s)P = (5760 \pi \, \text{N} \cdot \text{m}) \times \left(\frac{20 \pi}{3} \, \text{rad/s}\right) P=5760×20π23 W=1920×20π2 W=38400π2 WP = \frac{5760 \times 20 \pi^2}{3} \, \text{W} = 1920 \times 20 \pi^2 \, \text{W} = 38400 \pi^2 \, \text{W} P≈38400×(3.14159)2 W≈379800.36 WP \approx 38400 \times (3.14159)^2 \, \text{W} \approx 379800.36 \, \text{W} P≈379.80 kWP \approx 379.80 \, \text{kW}

    The power transmitted is 379.80 kW\boxed{\text{379.80 kW}}.

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