Mechanical Engineering

Toughness for mild steel under uniaxial tensile loading is given by the shaded portion of the stress-strain diagram as shown in
  • a)
  • b)
  • c)
  • d)
Correct answer is option 'D'. Can you explain this answer?

SAVITA KUMARI answered  •  9 hours ago
Toughness is the ability of material to absorb the energy upto fracture point, i.e. toughness of material is the total area under stress-strain curve.

The material in which large deformation is possible before the absolute failure or rupture is termed as
  • a)
    brittle
  • b)
    elastic
  • c)
    ductile
  • d)
    plastic
Correct answer is option 'C'. Can you explain this answer?

SHANU VERMA answered  •  9 hours ago
Ductility is defined as the ability of the material to deform to a greater extent before the sign of crack, when it is subjected to tensile force. Ductile materials are those materials which deform plastically to a greater extent prior to fracture e.g. mild steel, copper and aluminium.

If the crushing stress in the material of a mild steel column is 3300 kg/cm2. Euler’s formula for crippling load is applicable for slenderness ratio equal to/greater than
  • a)
    40
  • b)
    50
  • c)
    60
  • d)
    80
Correct answer is option 'D'. Can you explain this answer?

SNEHLATA KULDEEP answered  •  9 hours ago
For Euler’s formula to be applicable the critical stress must not exceed the proportional limit.
Now crushing stress in mild steel
= 3300 kg/cm2
= 330 N/mm2
But stress at proportional limit in mild steel
= 250 M/mm2
Euler’s buckling stress


λ = 88.55 ≈ 89
Thus slenderness ratio should be more than or equal to 89 ideally. Option (d) is the most close one.

In electrolux refrigerator. 
  • a)
     ammonia is absorbed in hydrogen 
  • b)
     ammonia is absorbed in water 
  • c)
     ammonia evaporates in hydrogen 
  • d)
     hydrogen evaporates in ammonia
Correct answer is option 'C'. Can you explain this answer?

MANDEEP KAUR answered  •  9 hours ago
Correct Answer :- c
Explanation : In Electrolux refrigerator Ammonia evaporates in hydrogen.
The ammonia liquid leaving the condenser enters the evaporator and evaporates into the hydrogen at the low temperature corresponding to its low partial pressure. The mixture of ammonia and hydrogen passes to the absorber into which is also admitted water from the separator. The water absorbs the ammonia and the hydrogen returns to the evaporator. In the absorber the ammonia therefore passes from the ammonia circuit into water circuit as ammonia in water solution. This strong solution passes to the generator where it is heated and the vapor given off rises to the separator. The water with the vapor is separated out and a weak solution of ammonia is passed back to the absorber, thus completing the water circuit. The ammonia vapor rises from the separator to the condenser where it is condensed and then returned to the evaporator.

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