41. What is a pressure cap in the radiator?

It is a seal in the radiator that maintains the selected pressure in the cooling system when the engine is hot.

42. How does the thermostat work?

When the engine is too cold the thermostat closes the main valve, thus stopping the flow to the radiator. When the engine is too hot, it opens the main valve for normal circulation through the radiator.

43. What are MPFI and TPFC systems?

MPFI stands for multi point fuel injection. In this system fuel in injected into the intake ports which is situated just upstream of each cylinder’s intake valve. These systems are sequential systems, in which injection is timed to coincide with intake stroke of each cylinder.

TPFC stands for transient power fuel control system. In this systems constant choke carburetor is used. The salient feature of this carburetor is that it provides jerk less engine raise. In these systems, throttle valve creates vacuum which opens the slide which controls the air fuel ratio through a tapered jet.

44. What is Poissons Ratio?

Lateral strain / Longintudinal strain.

45. Define: Hardness, Toughness, Resilience and Stiffness.

HARDNESS:- ” Resistance to wear, machining, cutting, scratching, indentation.”

TOUGHNESS:- “The strain energy stored by body upto fracture.”

RESILIENCE:- “The strain energy stored by body upto elastic limit” or “Recoverable/elastic strain energy.”

STIFFNESS:- “Resistance to deformation like elongation, twisting, bending, rotation, deflection.”

46. By which experiment you find hardness of material?

Brinell, Vickers, Rockwell Hardness Test.

47. Mention types of beams? – types of loads?

Types of beam:- Cantilever, Simply supported, Over hanging, Fixed and Continuous beams.

Types of load:- Point, Uniform distributed and Uniform Varying Loads.

48. Difference between direct stress and bending stress?

Direct tensile and compressive stress is setup because of load applied parallel to length of object.

Direct shear stress is setup in section which is parallel to line of action of the shear load.

But Bending stress is setup because of load at right angles to the length of object subjected to bending.

49. Define Torsional rigidity.

Torsional rigidity or stiffness of the shaft is defined as the product of modulus of rigidity ( C ) and polar moment of inertia of the shaft ( J ). Hence mathematically, the torsional rigidity is given as 

Torsional rigidity = C x J.

Torsional rigidity is also defined as the torque required to produce a twist of one radian per unit length of the shaft.

50.  Defined Slenderness ratio?

Slenderness ratio is the ratio of the length of a column and the least radius of gyration of its cross section.

Mechanical Engineering Important Question