Endurance strength is 100% for a component with
Soderberg and Goodman Equations are concerned with the safety factors in case of
A plate shown in figure subjected to force 60 kN . The stress concentration factor is 2.3 and maximum stress induced is 150 MPa, width of plate required is
w - 20 = 40 ⇒w = 60 mm
Endurance strength in reversals load in steel is found at
Fatigue strength of a machine element may be improved by
For a beam stress concentration factor for static load is 1.35 and stress concentration factor for fatigue load is 1.3. The notch sensitivity for specimen is __________.
Kt = 1.35, kf = 1.3
The design stress for a component subjected to a completely reversible load, is found by applying the factor of safety to
Auto fretting is a
Maximum stress induced at the edge of an elliptical hole of major axis 4 mm and minor axis 1.5 mm in a flat plate, as shown in figure, is
a = major axis
b = minor axis
Maximum stress in the part shown in figure is induced at the section
In designing a shaft for variable loads, the S.N. diagram can be drawn by
A plate having width 120 mm is subjected to a tensile load that has a maximum value of 250 kN and a minimum value of 100 kN. The properties of the plate material are as follows.
Endurance limit stress = 225 MPa
Yield point st!ess = 300 MPa
Factor of safety (N) =.1.5
The thickness of the plate as per Soderberg equation is __________ mm
Width (b) = 120 mm
Wmax = 250 KN, Wmin = 100 KN
Se = 225 MPa, syt = 300 MPa
N = 1.5
Wn= 175 KN
Wr = 75 KN
According to Soderberg equation
t = 11.458 mm
A loaded semi-infinite flat plate is having an elliptical hole in the middle as shown in the figure. The stress concentration factor due to the elliptical hole is?
Stress concentration factor
Kt = 1 + 2 x 2
Kt = 5
A thin spherical pressure vessel with 500 mm inner diameter is welded from steel plates having yield strength, σy = 200 MPa and endurance limit, a. The vessel is subjected to internal pressure which varies from 2 MPa to 6 MPa. Using Soderberg’s equation for fatigue failure and considering a factor of safety of 3, the thickness of the vessel is
Thin spherical pressure vessel
Syt = 200 MPa
Se = 100 MPa, inner diameter d = 500 mm
Internal pressure = 2MPa
Factor of safety (N) = 3
Thickness of the vessel (t) =
Applying Soderberg’s equation
t = 15 mm
Assertion (A): Soderberg relation is used for design against fatigue.
Reason (R): Soderberg relation is based on yield strength of the material whereas all other failure relations for dynamic loading are based on ultimate strength of the material.
For fatigue load we use Soderberg, Gerber, Goodman criteria for the design.
⇒When there is a combination of variable stress with the mean stress, then we use the above three design parameters.
⇒So, both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.
A steel component has a theoretical stress concentration factor of 2.1 and a notch sensitivity of 0.5. Its effect on the endurance strength is
Theoretical stress concentration factor
kt = 2.1
Notch Sensitivity (q) = 0.5
kf = Fatigue stress concentration factor
⇒kf = 1 + q(kt - 1)
= 1 + 0.5(2.1 - 1) = 1 + 0.55 = 1.55
Endurance strength is reduced by 35.5%
Consider the following statements
1. Endurance strength of a component is not affected by its surface finish and notch sensitivity of the material.
2. For ferrous materials like steel, S-N curve becomes asymptotic at cycles.
Which of the statements given above is/are correct?
Statement 1 is wrong, as the endurance strength is affected by its surface finish and notch sensitivity.
⇒If surface finish is poor, then endurance strength will decrease.
⇒If notch sensitivity(q) increases, then it will increase the fatigue stress concentration factor(kf) which will decrease the endurance strength.
The design calculations for members subject to fluctuating loads with the same factor of safety, yield the most conservative estimates when using
In the figure shown, if the line AB represents Goodman criterion of failure, then Soderberg criterion could be represented by line
Which of the following threaded joint will give the minimum stress concentration result?