Answer:
B A and C
Explanation:
Given:
Specimen σ
σ
A +450 -150
B +300 -300
C +500 -200
Solution:
Compute the mean stress
σ
= (σ
+ σ
)/2
σ
= (450 + (-150)) / 2
= (450 - 150) / 2
= 300/2
σ
= 150 MPa
σ
= (300 + (-300))/2
= (300 - 300) / 2
= 0/2
σ
= 0 MPa
σ
= (500 + (-200))/2
= (500 - 200) / 2
= 300/2
σ
= 150 MPa
Compute stress amplitude:
σ
= (σ
- σ
)/2
σ
= (450 - (-150)) / 2
= (450 + 150) / 2
= 600/2
σ
= 300 MPa
σ
= (300- (-300)) / 2
= (300 + 300) / 2
= 600/2
σ
= 300 MPa
σ
= (500 - (-200))/2
= (500 + 200) / 2
= 700 / 2
σ
= 350 MPa
From the above results it is concluded that the longest fatigue lifetime is of specimen B because it has the minimum mean stress.
Next, the specimen A has the fatigue lifetime which is shorter than B but longer than specimen C.
In the last comes specimen C which has the shortest fatigue lifetime because it has the higher mean stress and highest stress amplitude.
Answer:
The stress level at which fracture will occur for a critical internal crack length of 6.2mm is 135.78MPa
Explanation:
Given data;
Let,
critical stress required for initiating crack propagation Cc = 112MPa
plain strain fracture toughness = 27.0MPa
surface length of the crack = a
dimensionless parameter = Y.
Half length of the internal crack, a = length of surface crack/2 = 8.8/2 = 4.4mm = 4.4*10-³m
Also for 6.2mm length of surface crack;
Half length of the internal crack = length of surface crack/2 = 6.2/2 = 3.1mm = 3.1*10-³m
The dimensionless parameter
Cc = Kic/(Y*√pia*a)
Y = Kic/(Cc*√pia*a)
Y = 27/(112*√pia*4.4*10-³)
Y = 2.05
Now,
Cc = Kic/(Y*√pia*a)
Cc = 27/(2.05*√pia*3.1*10-³)
Cc = 135.78MPa
The stress level at which fracture will occur for a critical internal crack length of 6.2mm is 135.78MPa
For more understanding, I have provided an attachment to the solution.
Answer:
SI unit of system is superior.
Explanation:
The metric system is used internationally for measurement of unit.This metric system of unit is easier to understand .
Metric system of unit also known as international system of unit.The international system of unit is also represent in short form like SI unit.This unit system is internationally accepted.
So SI unit of system is superior.
Answer:
0.05%
Explanation:
From the question, we have;
The yield strength of the mild steel,
= 43.5 ksi
Young's modulus of elasticity, ∈ = 29,000 ksi
The total strain,
= 0.2% = 0.002
The inelatic strain
is given as follows;
=
-
/∈
Therefore, we have;
= 0.002 - 43.5/(29,000) = 0.0005
Therefore, the inelastic strain,
= 0.0005 = 0.05%
Taking the inelastic strain as the residual strain, we have;
The residual strain = 0.05%