6. The S-N curve for steel becomes asymptotic nearly at

1. 1. 10³ cycles

   
   
   

   2. 10⁴ cycles

   
   
   

   3. 10⁶ cycles

   
   
   

   4. 10⁹ cycles

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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7. A small element at the critical section of a component in biaxial state of stress with the two principal stresses being 360 MPa and 140 MPa. The maximum working stress according to distortion energy theory is

1. 1. 220 MPa

   
   
   

   2. 110 MPa

   
   
   

   3. 314 MPa

   
   
   

   4. 330 MPa

   
   
   

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1. View Hint View Answer Discuss in Forum

   According to distorsion energy theorem
   f²₁ + f²₂ - f₁ = (Working stress)²
   Working stress = √(360)² + (140)² - (360 140)
   = 314.32 MOa

   Correct Option: C

   According to distorsion energy theorem
   f²₁ + f²₂ - f₁ = (Working stress)²
   Working stress = √(360)² + (140)² - (360 140)
   = 314.32 MOa

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8. During a high cycle fatigue test, a metallic specimen is subjected to cyclic loading with a mean stress of + 140 MPa, and a minimum stress of – 70 MPa. The R-ratio (minimum stress to maximum stress) for this cycle loading is _______ (round off to one decimal place).

1. 1. 0.1

   
   
   

   2. 0.2

   
   
   

   3. - 0.1

   
   
   

   4. - 0.2

   
   
   

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1. View Hint View Answer Discuss in Forum

   σ_mean = + 140 MPa
   σ_min = – 70 MPa
   

   σmean =	σmax + σmin	= 140
   	2

   
   

   =	σmax - 70	= 140
   	2

   
   ⇒ σ_max = 350 MPa
   Now, minimum stress to maximum stress ratio is,
   

   σmin	=	- 70	= - 0.2
   σmax		350

   Correct Option: D

   Here,
   σ_mean = + 140 MPa
   σ_min = – 70 MPa
   

   σmean =	σmax + σmin	= 140
   	2

   
   

   =	σmax - 70	= 140
   	2

   
   ⇒ σ_max = 350 MPa
   Now, minimum stress to maximum stress ratio is,
   

   σmin	=	- 70	= - 0.2
   σmax		350

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9. Consider the schematic of a riveted lap Joint subjected to tensile load F, as shown below. Let d be the diameter of the rivets, and S_f be the maximum permissible tensile stress in the plates. What should be the minimum value for the thickness of the plates to guard against tensile failure of the plates? Assume the plates to be identical.
   

1. 1. F
      Sf(w - 2d)

   
   
   

   2. F
      Sf w

   
   
   

   3. F
      Sf(w - d)

   
   
   

   4. 2F
      Sf w

   
   
   

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1. View Hint View Answer Discuss in Forum

   Tensile stress Sf =	F
   	Sf (w - 2d)t

   
   

   t =	F
   	Sf (w - 2d)

   Correct Option: A

   Tensile stress Sf =	F
   	Sf (w - 2d)t

   
   

   t =	F
   	Sf (w - 2d)

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