A screw is said to be a self locking screw, if its efficiency is
Less than 50 %
More than 50 %
Equal to 50 %
None of these
Correct Answer :
A. Less than 50 %
Related Questions
The ball bearings are, usually, made from
Low carbon steel
High carbon steel
Medium carbon steel
High speed steel
The connecting rod bolts are tightened up so that tightening stress
Is just sufficient to hold parts together
Approaches yield point
Is 50% of yield point
Is about yield point divided by safety factor
Stress concentration in static loading is more serious in
Ductile materials
Brittle materials
Equally serious in both cases
Depends on other factors
The stress which vary from a minimum value to a maximum value of the same nature (i.e. tensile or compressive) is called
Repeated stress
Yield stress
Fluctuating stress
Alternating stress
Resilience of a material is important, when it is subjected to
Combined loading
Fatigue
Thermal stresses
Shock loading
The product of the diametral pitch and circular pitch is equal to
1
1/π
π
π × number of teeth
When spring index increases, the value of Wahl's stress factor
Increases linearly
Decreases linearly
Remains same
Increases exponentially
The bearings of medium series have capacity __________ over the light series.
10 to 20 %
20 to 30 %
30 to 40 %
40 to 50 %
The material used for brake lining should have __________ coefficient of friction.
Low
High
Moderate
None of these
The cam follower extensively used in aircraft engines is
Knife edge follower
Flat faced follower
Spherical faced follower
Roller follower
Plastic flow in ductile materials
Increases the seriousness of static loading stress concentration
Lessens the seriousness of static loading stress concentration
Has no effect on it
Depends on other considerations
The effective stress in wire ropes during normal working is equal to the stress due to
Axial load plus stress due to bending
Acceleration/retardation of masses plus stress due to bending
Axial load plus stress due to acceleration/retardation
Bending plus stress due to acceleration/retardation
The cold working of metals is carried out __________ the recrystallisation temperature.
Above
Below
At
None of these
For high speed engines, the cam follower should move with
Uniform velocity
Simple harmonic motion
Uniform acceleration and retardation
Cycloidal motion
The efficiency of a square threaded screw is maximum if the helix angle is equal to (Where φ = Angle of friction)
90° - φ
45° - φ
45° - φ/2
45° + φ/2
Stress concentration is caused due to
Variation in properties of material from point to point in a member
Pitting at points or areas at which loads on a member are applied
Abrupt change of section
All of the above
Silver based solder is used for
Flaring
Brazing
Soft soldering
Fusion welding
In order to avoid tearing of the plate at edge, the distance from the center line of the rivet hole to the nearest edge of the plate in terms of dia. of rivet d should be equal to
d
1.25 d
1.5 d
1.75 d
For maximum power, the velocity of the belt will be
√(T/m)
√(T/2m)
√(T/3m)
None of these
The ratio of endurance limit in shear to the endurance limit in flexure is
0.70
0.25
0.40
0.55
If a material fails below its yield point, failure would be due to
Straining
Fatigue
Creep
Sudden loading
The static tooth load should be __________ the dynamic load.
Equal to
Less than
Greater than
None of these
In a gear, having Involute teeth, the normal to the Involute is a tangent to the
Base circle
Pitch circle
Addendum circle
Dedendum circle
The shock absorbing capacity of a bolt may be increased by
Increasing its shank diameter
Decreasing its shank diameter
Tightening the bolt properly
Making the shank diameter equal to core diameter of thread
In the case of an elastic bar fixed at upper end and loaded by a falling weight at lower end, the shock load produced can be decreased by
Decreasing the cross-section area of bar
Increasing the cross-section area of bar
Remain unaffected with cross-section area
Would depend upon other factors
The rolling contact bearings are known as
Thick lubricated bearings
Plastic bearings
Antifriction bearings
Thin lubricated bearings
Which of the following statement is correct?
A parallel sunk key is a taperless key
A parallel sunk key may be rectangular or square in cross-section
A flat saddle key is a taper key which fits in a key way of the hub and is flat on the shaft
All of the above
According to I.B.R., the factor of safety of riveted joint should not be less than
1
2
3
4
Oil in journal bearing should be applied at the point where load is
Nil or lightest
Maximum
Average
Any one of the above
In a belt drive, if the pulley diameter is doubled keeping the tension and belt width constant, then it will be necessary to
Increase the key length
Increase the key depth
Increase the key width
Decrease the key length