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
Wahl’s factor is related to the spring index, such that it _______, as the spring index decreases
increases very rapidly
Two helical coil springs with stiffness k1 and k2 respectively are connected in series. The stiffness of an equivalent spring is given by
(k1k2)/( k1+k2)
When a helical compression spring is subjected to an axial compressive load, the stress induced in the wire is
none of the above
When helical compression spring is cut into quarters, the stiffness of the resulting spring will be
quadruple
This type of end connection for compression helical spring can best minimize if not eliminate the possibility of eccentric application of load.
squared and ground ends
This type of screw is primarily used to prevent relative motion between two parts
set screw
This form of screw thread is a modification of square thread and has rounded top and bottom
knuckle thread
Two shafts A and B are made of the same material. The diameter of the shaft A is twice as that of shaft B. The power transmitted by the shaft A will be ……….. of shaft B
eight times
Which of the following loading is considered for the design of axles?
Bending Moment only
The strength of a shaft with a keyway is almost reduced by as much as
25%
A basic shaft is one whose
upper deviation is zero
In designing a connecting rod, it is considered like ………….. for buckling about X-axis.
both ends hinged
When a shaft is subjected to a bending moment M and a twisting moment T, then the equivalent twisting moment is equal to
(M^2 + T^2)^1/2
A type of end fixity where the end of the column is guided so that it cannot sway from side to side, but offers no resistance to rotation of the end.
pinned-end
A transmission shaft subjected to bending loads must be designed on the basis of
maximum normal stress theory
The connecting rod of rectangular cross-section will be equally strong in buckling about X-axis and Y-axis, if
Ixx=4Iyy
