In a hydrodynamic lubricated bearing
There is a thick film of lubricant between the journal and the bearing
There is a thin film of lubricant between the journal and the bearing
The lubricant is forced between the journal and the bearing, by external pressure
There is no lubricant between the journal and the bearing
Correct Answer :
A. There is a thick film of lubricant between the journal and the bearing
Related Questions
The objective of idler pulley in belt drive is to
Decrease the tendency of belt to slip
Increase the power transmission capacity
Increase the wrap angle and belt tension
All the above objectives
The bending stress in a curved beam is
Zero at the centroidal axis
Zero at the point other than centroidal axis
Maximum at the neutral axis
None of these
The condition for maximum power transmission is that the maximum tension in the flat belt should be equal to
3 Pc
Pc
Pc/3
2 Pc Where, Pc = tension in belt due to centrifugal force
Jam nut is a locking device in which
One smaller nut is tightened over main nut and main nut tightened against smaller one by loosening, creating friction jamming
A slot is cut partly in middle of nut and then slot reduced by tightening a screw
A hard fibre or nylon cotter is recessed in the nut and becomes threaded as the nut is screwed on the bolt causing a tight grip
Through slots are made at top and a cotter pin is passed through these and a hole in the bolt, and cotter spitted and bent in reverse direction at other end
When a material is subjected to fatigue loading, the ratio of the endurance limit to the ultimate tensile strength is
0.20
0.35
0.50
0.65
A machine part subjected to __________ is called a strut.
An axial compressive force
A tangential force
An axial tensile force
Any one of these
Screws used for power transmission should have
Very fine threads
High efficiency
Low efficiency
Strong teeth
A column of length l is fixed at both ends. The equivalent length of the column is
l/2
l/√2
l
2 l
For maximum power, the velocity of the belt will be
√(T/m)
√(T/2m)
√(T/3m)
None of these
18/8 steel contains
18% nickel and 8% chromium
18% chromium and 8% nickel
18% nickel and 8% vanadium
18% vanadium and 8% nickel
For applications involving high stresses in one direction only the following type of thread would be best suited
ISO metric thread
Acme thread
Square thread
Buttress thread
The piston pin bearings in heavy duty diesel engines are
Needle roller bearings
Tapered roller bearings
Spherical roller bearings
Cylindrical roller bearings
The permissible stress for carbon steel under static loading is generally taken as
2000-3000 kg/m²
3000-4000 kg/cm²
4000-4500 kg/cm²
7500-10,000 kg/cm²
If the centre distance of the mating gears having involute teeth is varied within limits, the velocity ratio.
Increases
Decreases
Remains unchanged
None of these
The gears are termed as medium velocity gears, if their peripheral velocity is
1-3 m/s
3-15 m/s
15-30 m/s
30-50 m/s
In a steam engine, the piston rod is usually connected to the crosshead by means of a
Knuckle joint
Cotter joint
Oldham coupling
Universal joint
Residual stress in materials
Acts when external load is applied
Becomes zero when external load is removed
Is independent of external loads
Is always harmful
Silver based solder is used for
Flaring
Brazing
Soft soldering
Fusion welding
The strength of a riveted joint is equal to
Tearing strength of plate (Pt)
Shearing strength of rivet (Ps)
Crushing strength of rivet (Pc)
Least value of Pt Ps and Pc
When a hole of diameter d is punched in a metal of thickness 't', then the force required to punch a hole is equal to (where τu = Ultimate shear strength of the material of the plate)
d.t.τu
πd.t.τu
π/4 × d².τu
π/4 × d² × t.τu
For hardening alloy steels and high speed steels, they are heated to
1100 to 1300°C
1300 to 1500°C
500 to 600°C
700 to 900°C
Rankine Gordon formula for buckling is valid for
Long column
Short column
Short and long column
Very long column
Spring stiffness is
Ratio of coil diameter to wire diameter
Load required to produce unit deflection
Its capability of storing energy
Its ability to absorb shocks
A localised compressive stress at the area of contact between two members is known as
Tensile stress
Bending stress
Bearing stress
Shear stress
According to I.B.R., the efficiency of a double riveted butt joint with double cover straps of equal width should be
45 to 60 %
63 to 70 %
70 to 83 %
80 to 90 %
The endurance or fatigue limit is defined as the maximum value of the stress which a polished standard specimen can withstand without failure, for infinite number of cycles, when subjected to
Static load
Dynamic load
Static as well as dynamic load
Completely reversed load
The cam follower extensively used in aircraft engines is
Knife edge follower
Flat faced follower
Spherical faced follower
Roller follower
Antifriction bearings are
Sleeve bearings
Hydrodynamic bearings
Thin lubricated bearings
None of the above
A tapered key which fits in a key way in the hub and the bottom of which is shaped to fit the curved surface of the shaft, is known as,
Hollow saddle key
Hollow key
Soft key
None of these
Two helical springs of the same material and of equal circular crosssection, length and number of turns, but having radii 80 mm and 40 mm, kept concentrically (smaller radius spring within the larger radius spring), are compressed between two parallel planes with a load W. The inner spring will carry a load equal to
W/2
2W/3
W/9
8W/9