Machine Design 1 Elements 3 Flashcards
Hooke’s law holds good up to
elastic limit
The ratio of the ultimate stress or yield stress of a material to the design stress is known as
factor of safety
The modulus of rigidity for mild steel is approximately equal to
80 GPa
The ratio of linear stress to linear strain is called
Modulus of elasticity
The Young’s modulus for mild steel is approximately equal to
210 GPa
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
πdtSu
A localised compressive stress at the area of contact between two members is known as
bearing stress
The stress in the bar when load is applied suddenly is …………. as compared to the stress induced due to gradually applied load
double
The yield strength for shear is reduced by as much as ………. of the yield strength
40%
It is the property of a material that is usually measured in terms of percentage elongation and percentage reduction in area.
none of the above
It is the amount by which the actual size of the shaft is less than the actual size of the mating hole in an assembly.
clearance
In torsion, the maximum stress happens at
the outermost fiber
Guest’s theory is used for
ductile materials
A stress which varies from a minimum value to a maximum value of the same nature (i.e. tensile or compressive) is called
varying stress
When a material is subjected to fatigue loading, the ratio of its ultimate tensile strength to its endurance limit is
0.50
Failure of a material is called fatigue when it fails
below the yield point
The resistance to fatigue of a material is measured by
endurance limit
It is an external load whose line of action is parallel but does not coincide with the centroidal axis of a machine component.
eccentric load
A square-threaded jack has a lead angle of λ. The jack will be self-locking when the coefficient of friction (f) is
f > tan λ
When helical compression spring is cut into halves, the stiffness of the resulting spring will be
double
To ensure self -locking in a screw jack, it is essential that the helix angle is
smaller than friction angle
A screw is said to be self -locking screw, if its efficiency is
less than 50%
The ratio of the load on a spring to its corresponding axial deflection
spring scale
Which of the following thread is not used for power transmission in either direction?
Buttress thread