Answer:
0.16 micron per day
Explanation:
Given:
The initial crack length, a₁ = 0.1 micron = 0.1 × 10⁻⁶ m
Initial tensile stress, σ₁ = 120 MPa
Final stress = 30 MPa
now from Griffith's equation, we have
![\sigma=[\frac{G_cE}{\pi\ a}]^\frac{1}{2}](https://tex.z-dn.net/?f=%5Csigma%3D%5B%5Cfrac%7BG_cE%7D%7B%5Cpi%5C%20a%7D%5D%5E%5Cfrac%7B1%7D%7B2%7D)
where,
Gc and E are the material constants
now,
for the initial stage
![120=[\frac{G_cE}{\pi\ (0.1\times10^{-6}}]^\frac{1}{2}](https://tex.z-dn.net/?f=120%3D%5B%5Cfrac%7BG_cE%7D%7B%5Cpi%5C%20%280.1%5Ctimes10%5E%7B-6%7D%7D%5D%5E%5Cfrac%7B1%7D%7B2%7D)
........{1}
and for the final case
![30=[\frac{G_cE}{\pi\ a_2}]^\frac{1}{2}](https://tex.z-dn.net/?f=30%3D%5B%5Cfrac%7BG_cE%7D%7B%5Cpi%5C%20a_2%7D%5D%5E%5Cfrac%7B1%7D%7B2%7D)
............{2}
on dividing 1 by 2, we get
![\frac{120}{30}=[\frac{a_2}{0.1\times10^{-6}}]^\frac{1}{2}](https://tex.z-dn.net/?f=%5Cfrac%7B120%7D%7B30%7D%3D%5B%5Cfrac%7Ba_2%7D%7B0.1%5Ctimes10%5E%7B-6%7D%7D%5D%5E%5Cfrac%7B1%7D%7B2%7D)
or
a₂ = 4² × 0.1 × 10⁻⁶ m
or
a₂ = 1.6 micron
Now,
the change from 0.1 micron to 1.6 micron took place in 10 days
therefore, the rate at which the crack is growing = 
or
average rate of change of crack = 0.16 micron per day
Answer:
The correct option is d ( Neither A nor B)
Explanation:
Technician A made 2 mistakes in his statement.Firstly the tire is self supporting not self sealing.
Secondly, this tire does not provide permanent sealing of punctured area option a is incorrect.
This self-supporting tire after being affected with complete air leakage can temporarily bear the load of the car and avoid rolling over a distance of 80 km at a maximum speed of 55 mph. Here is what technician B suggested incorrectly as the tire after being.Here the technician B suggested incorrectly as the tire after being affected with puncture can not travel at any speed so option B is wrong
Since option a and b are incorrect and c is invalid.
Answer:
Explanation:
Given data in question
mean stress = 50 MPa
amplitude stress = 225 MPa
to find out
maximum stress, stress ratio, magnitude of the stress range.
solution
we will find first maximum stress and minimum stress
and stress will be sum of (maximum +minimum stress) / 2
so for stress 50 MPa and 225 MPa
= 
+ 
/ 2
50 = + / 2 ...........1
and
225 = + / 2 ...........2
from eqution 1 and 2 we get maximum and minimum stress
= 275 MPa ............3
and = -175 MPa ............4
In 2nd part we stress ratio is will compute by ratio of equation 3 and 4
we get ratio = /
ratio = -175 / 227
ratio = -0.64
now in 3rd part magnitude will calculate by subtracting maximum stress - minimum stress i.e.
magnitude = -
magnitude = 275 - (-175) = 450 MPa
Answer:
DESCULPA MAS EU NÃO ENTENDI
