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maks197457 [2]
3 years ago
6

A ductile hot-rolled steel bar has a minimum yield strength in tension and compression of 350 MPa. Using the distortion-energy a

nd maximum-shear-stress theories, determine the factors of safety for the following plane stress states.
a. σx = 94 MPa, and τxy = -75 MPa
b. σx = 110 MPa, σy = 100 MPa
c. σx = 90 MPa, σy = 20 MPa, τxy =−20 MPa
Engineering
1 answer:
Ratling [72]3 years ago
7 0

Answer:

Explanation:

From  the given question:

Using the distortion energy theory to determine the  factors of safety  FOS can be expressed  by the relation:

\dfrac{Syt}{FOS}= \sqrt{ \sigma x^2+\sigma  y^2-\sigma x \sigma y+3 \tau_{xy^2}}

where; syt = strength in tension and compression = 350 MPa

The maximum shear stress theory  can be expressed as:

\tau_{max} = \dfrac{Syt}{2FOS}

where;

\tau_{max} =\sqrt{ (\dfrac{\sigma x-\sigma  y}{2})^2+ \tau _{xy^2

a. Using distortion - energy theory formula:

\dfrac{350}{FOS}= \sqrt{94^2+0^2-94*0+3 (-75)^2}}

\dfrac{350}{FOS}=160.35

{FOS}=\dfrac{350}{160.35}

FOS = 2.183

USing the maximum-shear stress theory;

\dfrac{350}{2 FOS}  =\sqrt{ (\dfrac{94-0}{2})^2+ (-75)^2

\dfrac{350}{2 FOS}  =88.51

\dfrac{350}{ FOS}  =2 \times 88.51

{ FOS}  =\dfrac{350}{2 \times 88.51}

FOS = 1.977

b. σx = 110 MPa, σy = 100 MPa

Using distortion - energy theory formula:

\dfrac{350}{FOS}= \sqrt{ 110^2+100^2-110*100+3(0)^2}

\dfrac{350}{FOS}= \sqrt{ 12100+10000-11000

\dfrac{350}{FOS}=105.3565

FOS=\dfrac{350}{105.3565}

FOS =3.322

USing the maximum-shear stress theory;

\dfrac{350}{2 FOS}  =\sqrt{ (\dfrac{110-100}{2})^2+ (0)^2

\dfrac{350}{2 FOS}  ={ (\dfrac{110-100}{2})^2

\dfrac{350}{2 FOS}  =25

FOS = 350/2×25

FOS = 350/50

FOS = 70

c. σx = 90 MPa, σy = 20 MPa, τxy =−20 MPa

Using distortion- energy theory formula:

\dfrac{350}{FOS}= \sqrt{ 90^2+20^2-90*20+3(-20)^2}

\dfrac{350}{FOS}= \sqrt{ 8100+400-1800+1200}

\dfrac{350}{FOS}= 88.88

FOS = 350/88.88

FOS = 3.939

USing the maximum-shear stress theory;

\dfrac{350}{2 FOS}  =\sqrt{ (\dfrac{90-20}{2})^2+ (-20)^2

\dfrac{350}{2 FOS}  =\sqrt{ (35)^2+ (-20)^2

\dfrac{350}{2 FOS}  =\sqrt{ 1225+ 400

\dfrac{350}{2 FOS}  =40.31

FOS}  =\dfrac{350}{2*40.31}

FOS = 4.341

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To calculate the heat transfer, Q, we make use of the steady flow eqn:

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h_{i} = specific enthalpy at inlet

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v_{i} = air speed at inlet

p_{s} = specific power input

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Then the above eqn reduces to:

h_{i} + gH + Q = h_{o} + \frac{v_{o}^{2}}{2} + gH + p_{s}

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From the eqn:

P_{o}V_{o} = mRT_{o}

m = \frac{800\times 10^{3}\times 0.157}{287\times 473} = 0.925 kg/s

Now,

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\Delta h = h_{o} - h_{i} = c_{p}\Delta T =c_{p}(T_{o} - T_{i}) = 1.005(200 - 20) = 180.9 kJ/kg

Now, using these values in eqn (1):

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Water is the working fluid in an ideal Rankine cycle. Saturated vapor enters the turbine at 12 MPa, and the condenser pressure i
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Answer:

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h_{out} = w_{in}+h_{in}

h_{out} = 12\,\frac{kJ}{kg} + 191.81\,\frac{kJ}{kg}

h_{out} = 203.81\,\frac{kJ}{kg}

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h_{out} = 2685.4\,\frac{kJ}{kg}

The rate of heat transfer in the boiler is:

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Answer:

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Explanation:

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Inner diameter = 3.0 cm

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2\times 10^{-3} m^3 = \frac{\pi}{4} \times (3\times 10^{-2})^2 \times velocity

V = \frac{20\times 4}{9\times \pi} = 2.83 m/s

Re = \frac{\rho\times V\times D}{\mu}

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Nu = \frac{hL}{k} = 0.0029\times Re^{0.8}\times Pr^{0.3}

Pr= \frac{\mu Cp}{K} = \frac{0.798\times 10^{-3} \times 4180}{0.615} = 5.419

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SOLVING FOR H

WE GET

h = 10,349.06 W/m^2 K

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