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nikdorinn [45]
3 years ago
10

Primary Creep: slope (creep rate) decreases with time

Engineering
1 answer:
Igoryamba3 years ago
5 0

Answer:

true

Explanation:

Creep is known as the time dependent deformation of structure due to constant load acting on the body.

Creep is generally seen at high temperature.

Due to creep the length of the structure increases which is not fit for serviceability purpose.

When time passes structure gain strength as the structure strength increases with time so creep tends to decrease.

When we talk about Creep rate for new structure the creep will be more than the old structure i.e. the creep rate decreases with time.

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For some metal alloy, a true stress of 345 MPa (50040 psi) produces a plastic true strain of 0.02. How much will a specimen of t
Strike441 [17]

Answer:

the elongation of the metal alloy is 21.998 mm

Explanation:

Given the data in the question;

K = σT/ (εT)ⁿ

given that metal alloy true stress σT = 345 Mpa, plastic true strain εT = 0.02,

strain-hardening exponent n = 0.22

we substitute

K = 345 / 0.02^{0.22

K = 815.8165 Mpa

next, we determine the true strain

(εT) = (σT/ K)^1/n

given that σT = 412 MPa

we substitute

(εT) = (412 / 815.8165 )^(1/0.22)

(εT) = 0.04481 mm

Now, we calculate the instantaneous length

l_i = l_0e^{ET

given that l_0 = 480 mm

we substitute

l_i =480mm × e^{0.04481

l_i =  501.998 mm

Now we find the elongation;

Elongation = l_i - l_0

we substitute

Elongation = 501.998 mm - 480 mm

Elongation = 21.998 mm

Therefore, the elongation of the metal alloy is 21.998 mm

6 0
2 years ago
wo companies, Ajax Co. and Boho Inc., were negotiating a merger. In the course of the negotiations, an Ajax representative told
boyakko [2]

Answer:

Yes

Explanation:

If the Ajax representative fails to correct the previous statement this can cause misrepresentation.

4 0
2 years ago
What is an example of an innovation in logistics?
Scorpion4ik [409]

Answer:

geolocation technologies, drones, automated transportation vehicles

Explanation:

3 0
2 years ago
Reference Parameters (returning multiple values): Write a C++ function that converts standard time to military time. Inputs incl
valkas [14]

Answer:

Code is given as below:

Explanation:

#include <iostream>

using namespace std;

//function prototype declaration

void MilitaryTime(int, int, char, int &, int &);

int main()

{

    //declare required variables

    int SHour, SMin, MHour, MMin;

    char AorP;

    //promt and read the hours from the user

    cout<<"Enter hours in standard time : ";

    cin>>SHour;

    //check the hours are valid are not

    while(SHour<0 || SHour>12)

    {

         cout<<"Invalid hours for standard time. "

             <<"Try again..."<<endl;

         cout<<"Enter hours in standard time : ";

         cin>>SHour;

    }

    //promt and read the minutes from the user

    cout<<"Enter minutes in standard time : ";

    cin>>SMin;

    //check the minutes are valid are not

    while(SMin<0 || SMin>59)

    {

         cout<<"Invalid minutes for standard time. "

             <<"Try again..."<<endl;

         cout<<"Enter minutes in standard time : ";

         cin>>SMin;

    }

    //promt and read the am or pm from the user

    cout<<"Enter standard time meridiem (a for AM p for PM): ";

    cin>>AorP;

    //check the meridiem is valid are not

    while(!(AorP=='a' || AorP=='p' || AorP=='A' || AorP=='P'))

    {

         cout<<"Invalid meridiem for standard time. "

             <<"Try again..."<<endl;

         cout<<"Enter standard time meridiem (a for AM p for PM): ";

         cin>>AorP;

    }

    //call function to calculate the military time

    MilitaryTime(SHour, SMin, AorP, MHour, MMin);

    //fill zeros and display standard time

    cout.width(2);

    cout.fill('0');

    cout<<SHour<<":";

    cout.width(2);

    cout.fill('0');

    cout<<SMin;

    if(AorP=='a' || AorP=='A')

         cout<<" am = ";

    else

         cout<<" pm = ";

    //fill zeros and display military time

    cout.width(2);

    cout.fill('0');

    cout<<MHour;

    cout.width(2);

    cout.fill('0');

    cout<<MMin<<endl;

    system("PAUSE");

    return 0;

}

//function to calculate the military time with reference parameters

void MilitaryTime(int SHour, int SMin, char AorP, int &MHour, int &MMin)

{

    //check the meredium is am or pm

    //and calculate hours

    if(AorP=='a' || AorP=='A')

    {

         if(SHour==12)

             MHour = 0;

         else

             MHour = SHour;

    }

    else

         MHour = SHour+12;

    MMin = SMin;

5 0
3 years ago
A 50 Hz, four pole turbo-generator rated 100 MVA, 11 kV has an inertia constant of 8.0 MJ/MVA. (a) Find the stored energy in the
raketka [301]

Given Information:

Frequency = f = 60 Hz

Complex rated power = G = 100 MVA

Intertia constant = H = 8 MJ/MVA

Mechanical power = Pmech = 80 MW

Electrical power = Pelec = 50 MW

Number of poles = P = 4

No. of cycles = 10

Required Information:

(a) stored energy = ?

(b) rotor acceleration = ?

(c) change in torque angle = ?

(c) rotor speed = ?

Answer:

(a) stored energy = 800 Mj

(b) rotor acceleration = 337.46 elec deg/s²

(c) change in torque angle (in elec deg) = 6.75 elec deg

(c) change in torque angle (in rmp/s) = 28.12 rpm/s

(c) rotor speed = 1505.62 rpm

Explanation:

(a) Find the stored energy in the rotor at synchronous speed.

The stored energy is given by

E = G \times H

Where G represents complex rated power and H is the inertia constant of turbo-generator.

E = 100 \times 8 \\\\E = 800 \: MJ

(b) If the mechanical input is suddenly raised to 80 MW for an electrical load of 50 MW, find rotor acceleration, neglecting mechanical and electrical losses.

The rotor acceleration is given by

$ P_a = P_{mech} - P_{elec} = M \frac{d^2 \delta}{dt^2}  $

Where M is given by

$ M = \frac{E}{180 \times f} $

$ M = \frac{800}{180 \times 50} $

M = 0.0889 \: MJ \cdot s/ elec \: \: deg

So, the rotor acceleration is

$ P_a = 80 - 50 = 0.0889 \frac{d^2 \delta}{dt^2}  $

$  30 = 0.0889 \frac{d^2 \delta}{dt^2}  $

$   \frac{d^2 \delta}{dt^2} = \frac{30}{0.0889}  $

$   \frac{d^2 \delta}{dt^2} = 337.46 \:\: elec \: deg/s^2 $

(c) If the acceleration calculated in part(b) is maintained for 10 cycles, find the change in torque angle and rotor speed in revolutions per minute at the end of this period.

The change in torque angle is given by

$ \Delta  \delta = \frac{1}{2} \cdot \frac{d^2 \delta}{dt^2}\cdot (t)^2 $

Where t is given by

1 \: cycle = 1/f = 1/50 \\\\10 \: cycles = 10/50 = 0.2  \\\\t = 0.2 \: sec

So,

$ \Delta  \delta = \frac{1}{2} \cdot 337.46 \cdot (0.2)^2 $

$ \Delta  \delta = 6.75 \: elec \: deg

The change in torque in rpm/s is given by

$ \Delta  \delta = \frac{337.46 \cdot 60}{2 \cdot 360\circ  }   $

$ \Delta  \delta =28.12 \: \: rpm/s $

The rotor speed in revolutions per minute at the end of this period (10 cycles) is given by

$ Rotor \: speed = \frac{120 \cdot f}{P}  + (\Delta  \delta)\cdot t  $

Where P is the number of poles of the turbo-generator.

$ Rotor \: speed = \frac{120 \cdot 50}{4}  + (28.12)\cdot 0.2  $

$ Rotor \: speed = 1500  + 5.62  $

$ Rotor \: speed = 1505.62 \:\: rpm

4 0
3 years ago
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