question bank machine design a: numerical problems: problems on pin… 603-machine design.pdf ·...

Department of Mechanical Engineering, NSEC of 25

QUESTION BANK

MACHINE DESIGN

A: Numerical Problems:

Problems on Pin, Cotter and Knuckle Joints:

1. Two rods, made of plane carbon steel 30C8 (fyt = 400 N/mm2), are to be connected by

means of a cotter joint. The diameter of each rod is 40 mm. Assuming yield strength in

compression = 1.5 fyt, yield strength in shear = 0.5 fyt and factor of safety = 5,

calculate:

a) Inside diameter of socket,

b) Outside diameter of socket, and

c) Diameter of socket collar.

2. Design a sleeve and cotter joint to resist a tensile load of 60 kN. All parts of the joint

are made of same material with the following allowable stresses:

ft = 60 N/mm2; fs = 70 N/mm

2; and fc = 125 N/mm

2.

3. Design a gib and cotter joint with two gibs to resist a safe tensile load of 50 kN. The

material of the gibs, cotter and rods is same for which the allowable safe stresses are :

fc = 60 N/mm2, ft = 25 N/mm

2 and fs = 20 N/mm

2.

4. Design a cotter joint for fastening the piston rod to the cross head of the engine having

cylinder diameter 0.24 m and steam pressure is 0.7 N/mm2. The thickness of the cotter

is to be 0.3 times piston rod diameter at the point where the cotter is located.

Allowable stresses in tension, shear and compression are 50 N/mm2; 40 N/mm

2 and 80

N/mm2 respectively.

5. A cotter foundation bolt is subjected to a maximum pull of 45 kN. The bolt and the

cotter are made of steel FeE300(fyt = 300 N/mm2) and the factor of safety is 5. The

yield strength in compression can be assumed to be twice of the tensile yield strength.

The thickness of the cotter is one-fourth of the diameter of enlarged end of the bolt.

Calculate:

a) The diameter of the bolt,

b) The diameter of the enlarged end of the bolt,

c) The thickness and the width of the cotter, and

d) The compressive stress between the cotter and the bolt. Is it safe?

6. Two round tie rods of a roof truss are connected by means of a coupling joint. The

maximum pull in the rod is 50 kN. Assuming that the allowable stress in tension,

compression and shear as 70 N/mm2; 80 N/mm

2 and 30 N/mm

2 respectively, design

the joint. How much would be the rods drawn together for one turn of the coupler?


7. An eye is forged at one end of the half of the tie rod and a fork at the end of the other

half. A knuckle pin is passed through the holes of the fork and the eye. The pull in the

tie rod is 150 kN. Allowable stresses in tension and shear are 65 N/mm2 and 30

N/mm2 respectively. Take the allowable bearing pressure on the pin as 10 N/mm

2.

Design the joint completely. Draw the elevation and plan in section of the designed

joint.

8. Design the suspension link of a structure, which is subjected to a load of 160 kN. The

allowable stresses in tension, shearing and crushing are 100 N/mm2; 75 N/mm

2 and

150 N/mm2 respectively. The width of the link is 50 mm.

9. Design a cotter joint to connect a piston rod to the crosshead. The maximum steam

pressure on the piston rod is 35 kN. Assuming that all the parts are made of the same

material having the following permissible stress: σt = 50 MPa ; τ = 60 MPa; and σc =

90 MPa

10. The big end of a connecting rod is subjected to a load of 40 KN. The diameter of the

circular part adjacent to the strap is 50 mm. Design the joint assuming the permissible

tensile stress in the strap as 30 Mpa and the permissible shear stress in the cotter and

jib as 20 Mpa.

Problems on screw joints and power screws:

1. A steam engine cylinder of 0.30m diameter is supplied with steam at 1.5 N/mm2. The

cylinder cover is fastened by means of 8 bolts of size M20. The joint is made leak

proof by means of suitable gaskets. Find the stress produced in the bolts.

2. A mild steel cover plate is to be designed for an inspection hole in the shell of a

pressure vessel. The hole is 0.12m in diameter and the pressure inside the vessel is 6

N/mm2. Design the cover plates along with the bolts. Assume allowable tensile stress

for mild steel as 60 N/mm2 and for bolt material as 40 N/mm

2.

3. A steam engine cylinder has an effective diameter of 200 mm. It is subjected to a

maximum steam pressure of 1.75 N/mm2. Calculate the number and size of studs

required to fix the cylinder cover on to the cylinder flange assuming the permissible

stress in the studs as 30 N/mm2. The pitch circle diameter of the studs is 320 mm. Also

check the circumferential pitch of the studs so as to give a leak proof joint.

4. A screw press is to exert a force of 40 kN. The unsupported length of the screw is 400

mm. Nominal diameter of the screw is 50 mm. The screw has square threads with

pitch equal to 10 mm. The material of the screw and nut are medium carbon steel and

cast iron respectively. For the steel take ultimate crushing stress as 320 N/mm2, yield


stress in tension and compression as 200 N/mm2 and that in shear as 120 N/mm

2.

Allowable shear stress for cast iron is 20 N/mm2 and allowable bearing stress between

screw and nut is 12 N/mm2. Young’s modulus for steel = 210×10

3 N/mm

2. Determine

the factor of safety of screw against failure. Find the dimensions of the nut. What is

the efficiency of the arrangement? Take co-efficient of friction between steel and cast

iron as 0.13.

5. Design a screw jack for lifting a safe load of 150 kN through a maximum lift of 350

mm. The elastic strength of the material of the screw may be taken as 240 N/mm2, in

tension and compression and 160 N/mm2 in shear. The nut is to be made of phosphor

bronze for which the elastic strengths in tension, compression and shear are 130, 115

and 100 N/mm2 respectively. Safe crushing stress for the material of the body is 100

N/mm2. The co-efficient of friction for the screw as well as collar may be taken as

0.15. The factor of safety for both screw and nut may be taken as 2. The design should

include the design of (i) screw, (ii) nut and (iii) cup and handle. Also find out the

efficiency of the screw jack.

You can take the help of the following standard chart for basic dimensions of the

square threads in “mm”.

Nominal diameter of

bolt (mm).

40 42 44 46 48 50 52 55 58 60

Core diameter of bolt

(mm).

33 35 37 38 40 42 44 46 49 51

Pitch of the bolt (mm). 7 7 7 8 8 8 8 9 9 9

Problems on Riveted and Welded joints:

1. A triple riveted lap joint with zig-zag riveting is to be designed to connect two plates

of 6 mm thickness. Determine the diameter of the rivets, pitch of rivets and the

distance between the rows of rivet. Indicate how the joint will fail. Assume ft = 120

N/mm2; fs = 100 N/mm

2 and fc = 150 N/mm

2.

2. Design the longitudinal and circumferential joint for a boiler whose diameter is 2.4 m

and is subjected to a pressure of 1N/mm2. The longitudinal joint is a triple riveted butt

joint with an efficiency of about 85% and the circumferential joint is a double riveted

lap joint with an efficiency of about 70%. The pitch in the outer rows of the rivets is to

be double than in the inner rows and the width of the cover plates is unequal. The

allowable stresses are: ft = 77 N/mm2; fs = 56 N/mm

2; and fc = 120 N/mm

2.

Assume that the resistance of rivets in double shear is 1.875 times that of single shear.

Draw the complete joint.

3. A triple riveted butt joint with equal double cover plates (zig-zag riveting) is used for

the longitudinal joint of a Lancashire boiler of 2.5m internal diameter. The working

steam pressure is 1.12 N/mm2 and the efficiency of the joint is 85%. Calculate the


plate thickness for mild steel of 460 N/mm2 ultimate tensile strength. Assume the ratio

of tensile to shear stresses as (7/6) and the factor of safety as 4. The resistance of the

rivets in double shear is to be taken as 1.875 times that of single shear. Design a

suitable circumferential joint also.

4. Two mild steel tie bars, for a bridge structure are to be joined by means of a butt joint

with double straps. The thickness of the tie bar is 12 mm and carries a tensile load of

400 kN. Design the joint completely taking the allowable stresses as ft = 100 N/mm2; fs

= 75 N/mm2; and fc = 150 N/mm

2.

5. A bracket is riveted to a column by 6 rivets of equal size as shown in Fig.10. It carries

a load of 100 kN at a distance of 250 mm from the column. If the maximum shear

stress in the rivet is limited to 63 N/mm2, find the diameter of the rivet.

Fig.10

6. A bracket is attached to a horizontal column by means of three identical rivets as

shown in Fig.11. The maximum permissible shear stress for the rivet is 60 N/mm2.

(i) Which rivet is subjected to maximum shear force?

(ii) What is the magnitude of maximum shear force?

(iii) Determine the diameter of rivet.


Fig.11

7. A steel plate, 80 mm wide and 10 mm thick, is joined to another steel plate by means

of a single transverse and double parallel fillet welds as shown in Fig.14. The strength

of the welded joint should be equal to the strength of the plates to be joined. The

permissible tensile and shear stresses for the weld material and the plates are 100 and

70 N/mm2 respectively. Find the length of each parallel fillet weld. Assume that the

tensile force passes through the centre of gravity of three welds.

Fig.14

8. The fillet welds of equal legs are used to fabricate a ‘T’ as shown in Fig.15(a) and (b),

where ‘s’ is the leg size and ‘l’ is the length of the weld.

Locate the plane of maximum shear stress in each of the following loading patterns.

(i) Load parallel to the weld (neglect eccentricity), and

(ii) Load at right angles to the weld (transverse load).

Find also the ratio of these limiting loads.


Fig.15(a) Fig.15(b)

9. A 65 mm diameter solid shaft is to be welded to a flat plate by a fillet weld around the

circumference of the shaft. Determine the size of the weld if the torque on the shaft is

3 KN-m. The allowable shear stress in the weld is 70 Mpa.

10. A solid rectangular shaft of cross section 80 mm X 50 mm is welded by a 5 mm fillet

weld on all sides to a flat plate with axis perpendicular to the plate surface. Find the

maximum torque that can be applied to the shaft, if the shear stress in the weld is not

to exceed 85 Mpa.

Problems on Shafts and Couplings:

1. A solid steel shaft is supported on two bearings 1.8 m apart and rotates at 250 r.p.m. A

20° involute gear D, 300 mm pitch circle diameter is keyed to the shaft at a distance of

150 mm to the left of the right hand bearing. Two pulleys B and C are mounted on the

shaft at distances of 600 mm and 1350 mm respectively to the right of the left-hand

bearing. The diameters of the pulleys B and C are 750 mm and 600 mm respectively.

30 kW is supplied to the gear, out of which 20 kW is taken-off at the pulley C and 10

kW from pulley B. The tangential force acting on the gear is vertically downward. The

drive from B is vertically downward while from C the drive is downward (front) at an

angle of 60° to the horizontal. In both cases the belt tension ratio is 2 and the angle of

lap is 180°. The combined fatigue and shock factors for torsion and bending may be

taken as 1.5 and 2 respectively.

Design the shaft taking allowable stresses in tension and shear as 84 N/mm2 and 42

N/mm2 respectively.

2. A steel shaft 800 mm long transmitting 15 kW at 400 r.p.m. is supported at two

bearings at the two ends. A gear wheel having 80 teeth and 500 mm pitch circle

diameter is mounted at 200 mm from the left hand side bearing and receives power

from a pinion meshing with it. The axis of the pinion and gear lie in the horizontal

plane and the tangential force on the gear is acting vertically downward. A pulley of

300 mm diameter is mounted at 200 mm from the right hand side bearing and is used

for transmitting power by a belt. The belt drive is inclined at 30° to the vertical (down)

in the forward direction. The belt lap angle is 180° and the co-efficient of friction

between the belt and pulley is 0.3. Design and sketch the arrangement of the shaft

assuming the values of safe stresses as: fs = 55 N/mm2 ; ft = 80 N/mm

2. Take torsion

and bending factor as 1.5 and 2.0 respectively. Pressure angle of the gear is 20°. Also

assume the permissible angle of twist is 0.18° / metre length and the modulus of

rigidity for the shaft material is 79300 N/mm2.

3. Consider the forces acting on the intermediate shaft shown in Fig.18 of problem 3.

The maximum permissible radial deflection at any gear is limited to ( 0.01m ), where


m is the module. The module of the two spur gears is 10 mm and the modulus of

elasticity of the shaft material is 207000 N/mm2. The shaft can be assumed to be

simply supported at the bearings. Determine the radial deflections at gears A and B

and find out the shaft diameter on the basis of lateral rigidity.

4. Design and draw a muff coupling which is used to connect two steel shafts

transmitting 25 kW power at 360 r.p.m. The shafts and keys are made of plain carbon

steel 30C8 ( fyt = fyc = 400 N/mm2). The sleeve is made of grey cast iron FG200 ( fut =

200 N/mm2). The factor of safety for the shafts and keys is 4. For sleeve the factor of

safety is 6 based on ultimate strength

5. A protected type flange coupling is used to transmit 15 kW power at 200 r.p.m. The

design torque is 125% of the rated torque. The shafts, keys and bolts are made of plain

carbon steel 40C8 (fyt = 380 N/mm2) and the factor of safety is 5. The yield strength in

compression can be taken as 150% of the tensile yield strength and the yield strength

in shear is 50% as that of tension. The flanges are made of grey cast iron of grade

FG200 (fut = 200 N/mm2) and the factor of safety is 6. The keys have square cross-

section. Design the coupling and specify the dimensions of its parts.

6. It is required to design a split-muff coupling to transmit 50 kW power at 120 r.p.m.

The shafts, keys and coupling bolts are made of plain carbon steel 30C8 (fyt = 400

N/mm2). The yield strength in compression is 150% of tensile yield strength. The

factor of safety for shafts, and bolts is 5. The number of clamping bolts is 8. The co-

efficient of friction between sleeve halves and the shaft is 0.3.

a) Calculate the diameter of input and output shafts.

b) Specify length and outer diameter of sleeve halves.

c) Find out the diameter of the clamping bolts assuming that the power is transmitted

by friction.

d) Specify bolt diameter using standard emperical relations.

e) Specify the size of key and check the dimensions for shear and compression

criteria.

7. A line shaft is to transmit 30 kW at 160 r.pm. It is driven by a motor placed directly

under it by means of a belt running on a 1 m diameter pulley keyed to the end of the

shaft. The tension in the tight side of the belt is 2.5 times that in the slack side and the

centre of the pulley over-hangs 150 mm beyond the centre line of the ned bearing.

Determine the diameter of the shaft, if the allowable shear stress is 56 Mpa and the

pulley weights 1600 N.

Problems on Belt drives:

1. Design an open flat belt drive to transmit 120 kW for a system consisting of two

pulleys of diameters 0.9m and 1.2m, centre distance of 3.6m, a belt speed of 20 m/sec,

co-efficient of friction 0.3, a slip of 1.2% at each pulley and 5% friction loss at each

shaft and of 20% overload. Take the density of the belt material is 1 gm/c.c., width of


the belt is 25 times the thickness and allowable tensile stress in the belt material is 2.5

N/mm2.

2. A blower is driven by an electric motor through a belt drive. The motor runs at 450

r.p.m. For this power transmission, a flat belt of 8 mm thickness and 250 mm width is

used. The diameter of the motor pulley is 350 mm and that of the blower pulley is

1350 mm. The centre distance between these pulleys is 1850 mm and an open belt

configuration is adopted. The pulleys are made of cast iron. The co-efficient of friction

between the belt and pulley is 0.35 and the permissible stress for the belt material can

be taken as 2.5 N/mm2. The mass of the belt is 2 kg/m length. Find the maximum

power transmitted without belt slipping in any one of the pulley.

3. A 25 kW, 900 r.p.m. motor drives a centrifugal pump at 290 r.p.m. by means of a

leather belt. The pulleys are of cast iron and are 1.2 metre centre distance. The pulleys

of diameter less than 150 mm should not be used. The co-efficient of friction between

the leather belt and the cast iron pulley is 0.35, and the belt weighs 0.9 gm/cm

width/cm length. The maximum permissible tension per cm width of the belt is 100 N.

The drive is to be designed for 20% overload.

Determine the pulley diameters, the required width and the length of the belt. Also,

find the initial tension with which the belt is to be mounted on the pulleys.

4. An overhung cast iron pulley transmits 7.5 kW at 400 r.p.m. The belt drive is vertical

and the angle of wrap may be taken as 180°. The co-efficient of friction between the

belt and pulley is 0.25. Determine:

(i) Diameter of the pulley taking the density of cast iron is 7200 Kg/m3.

(ii) Width of the belt assuming thickness of 10 mm and the density of belt material

as 1000 kg/m3.

(iii) Diameter of the shaft, if the distance of the pulley centre line from the nearest

bearing is 300 mm.

(iv) Dimensions of the key for securing the pulley on to the shaft.

(v) Size of the arm six in number.

The section of the arm may be taken as elliptical, the major axis being twice the minor

axis. The following stresses may be taken for the design purposes:

Shaft and key : Tension and compression ---- 80 N/mm2.

Shear ---- 50 N/mm2.

Belt : Tension ---- 2.5 N/mm2.

Pulley rim : Tension ---- 4.5 N/mm2.

Pulley arms : Tension ---- 15 N/mm2.

5. Two shafts whose centres are 1 m apart are connected by a V- belt drive. The driving

pulley is supplied with 125 kW and has an effective diameter of 0.3 m. It runs at 1000

r.p.m while the driven pulley runs at 375 r.p.m. The angle of groove on the pulleys is

40°. Permissible tension in 400 mm2 cross-sectional area belt is 2.1 N/mm

2. The

material of the belt weighs 1.11 gm/c.c. They driven pulley is overhung, the distance

of the centre from the nearest bearing being 200 mm. The co-efficient of friction


between belt and pulley rim is 0.28. Estimate: (i) The number of bolts required, and

(ii) Diameter of the driven pulley shaft, if permissible shear stress is 42 N/mm2.

6. Power of 80 kW at 750 r.p.m. is to be transmitted from an electric motor to a

compressor shaft at 300 r.p.m. by V-belts. The approximate larger pulley diameter is

1500 mm. The approximate centre distance is 1650 mm, and overload factor is to be

taken as 1.5. Give a complete design of the belt drive. A belt with cross-sectional area

of 3.5 cm2 and weighing 0.001 kg/cm

3 and having an allowable tensile strength 2

N/mm2 is available for use. The coefficient of friction between the belt and the pulley

may be taken as 0.28. The driven pulley is overhung to the extent of 300 mm from the

nearest bearing and is mounted on a shaft having permissible shear stress of 40 N/mm2

with the help of a key.

Also design the shaft and key used in the belt drive.

Problems on Springs:

1. Design and draw a valve spring of a petrol engine for the following operating

conditions:

Spring load when the valve is open = 400 N.

Spring load when the valve is closed = 250 N.

Maximum inside diameter of the spring = 25 mm.

Length of the spring when the valve is open = 40 mm.

Length of the spring when the valve is closed = 50 mm.

Maximum permissible shear stress = 400 N/mm2.

Modulus of rigidity = 80 kN/mm2.

2. Design a helical spring for a spring loaded safety valve for the following conditions:

Operating pressure = 1 N/mm2.

Maximum pressure when the valve is blows off freely = 1.075 N/mm2.

Maximum lift of the valve when the pressure is 1.075 N/mm2 = 6 mm.

Diameter of the valve seat = 100 mm.

Maximum shear stress = 400 N/mm2.

Modulus of rigidity = 86 × 103 N/mm

2.

Spring index = 5.5.

3. A semi-elliptical laminated spring 900 mm long and 55 mm wide is held together at

the centre by a band 50 mm wide. If the thickness of each leaf is 5 mm, find the

number of leaves required to carry a load of 4500 N. Assume a maximum working

stress of 490 N/mm2.

If the two of these leaves extend the full length of the spring, find the deflection the

spring. The Young’s modulus for the spring material may be taken as 210 N/ mm2.

Department of Mechanical Engineering, NSEC of

25

4. A semi-elliptical laminated spring is to carry a load of 5000 N and consists of 8 leaves

46 mm wide, two of the leaves being of full length. The spring is to be made 1000 mm

between the eyes and is held at the centre by a 60 mm wide band. Assuming that the

spring is initially stressed so as to induce an equal stress of 500 N/mm2 when fully

loaded. Design the spring giving (i) thickness of the leaves, (ii) eye diameter, (iii)

length of leaves, (iv) maximum deflection and camber.

Assume E =2.1 × 105 N/mm

2.

5. A semi-elliptical laminated vehicle spring to carry a load of 6000 N is to consist of

seven leaves 65 mm wide, two of the leaves extending the full length of the spring.

The spring is to be 1.1 m in length and attached to the axle by two U-bolts 80 mm

apart. The bolts hold the central portion of the spring so rigidly that they may be

considered equivalent to a band having a width equal to the distance between the bolts.

Assume a design stress for spring material as 350 N/mm2. Determine:

(i) Thickness of leaves,

(ii) Deflection of spring,

(iii) Diameter of eye,

(iv) Length of leaves, and

(v) Radius to which leaves should be initially bent.

The standard thickness of leaves are: 5, 6, 6.5, 7, 7.5, 8, 9, 10, 11 etc. in mm.

6. A semi-elliptical spring has ten leaves in all, with the two full length leaves extending

625 mm. It is 62.5 mm wide and 6.25 mm thick. Design a helical spring with mean

diameter of coil 100 mm which will have approximately the same induced stress and

deflection for any load. The Young’s modulus for the material of the semi-elliptical

spring may be taken as 200 N/mm2and modulus of rigidity for the material of the

helical spring is 80 kN/mm2.

Problems on Pressure Vessels and Pipes:

1. The hydraulic cylinder 400 mm bore operates at a maximum pressure of 5 N/mm2.

The piston rod is connected to the load and the cylinder to the frame through hinged

joints. Design:

(i) Cylinder,

(ii) Piston rod,

(iii) Hinge pin, and

(iv) Flat end cover.

The allowable tensile stress for the cast steel cylinder and end cover is 80 N/mm2 and

for piston rod is 60 N/mm2 and shear stress for the hinge pin is 45 N/mm

2.

2. The hydraulic press, having a working pressure of water as 16 N/mm2 and exerting a

force of 80 kN is required to press materials up to a maximum size of 800 mm × 800


25

mm and 800 mm high, the stroke length is 80 mm. Design the following parts of the

press:

(i) Ram, (ii) Cylinder, (iii) Pillars and (iv) Gland.

3. Design a circular flanged pipe joint for a cast iron pipe with internal diameter 200 mm

is subjected to a fluid pressure of 0.7 N/mm2. The flange is connected by means of

eight bolts. The pitch circle diameter of the bolts is 290 mm. Take the allowable

tensile stress in the pipe material is 14 N/mm2 and in the bolts is 60 N/mm

2.

4. Design an oval flanged pipe joint for pipes of internal diameter 50 mm subjected to a

fluid pressure of 7 N/mm2. The maximum tensile stress in the pipe material is not to

exceed 21 N/mm2 and in the bolts 28 N/mm

2.

5. The pressure within the cylinder of a hydraulic press is 8.4 N/sq. mm. The inside

diameter of the cylinder is 25.4 mm. Determine the thickness of the cylinder wall, if

the allowable tensile stress is 17.5 Mpa.

B: Multi-Choice Questions:

1. Guest’s theory of failure is applicable for following type of materials

(a) brittle

(b) ductile

(c) elastic

(d) plastic

(e) tough

2. Rankine’s theory of failure is applicable for following type of materials

a) brittle

b) ductile

c) elastic

d) plastic

e) tough

3. Resilience of a material is important, when it is subjected to

a) combined loading

b) fatigue

c) thermal stresses

d) wear and tear

e) shock loading.

4. The shear modulus of resilience of a material is proportional to

(a) shear stress (fs)

(b) fs2

(c) fs3

(d) fs1/2

(e) fs3/2


25

5. If a load W is applied instantaneously on a bar; then the stress induced in the bar will

a) be independent of ratio of mass of load W to mass of bar (γ)

b) increase with increase in γ

c) decrease with decrease in γ

d) depend on other considerations

e) none of the above.

6. In most of the machine members, the damping capacity of the material should be

a) low

b) zero

c) high

d) could be anything


7. Basic shaft is one

a) whose upper deviation is zero

b) whose lower deviation is zero

c) whose lower as well as upper deviations are zero

d) does not exist


8. Basic hole is one

a) whose upper deviation is zero

b) whose lower deviation is zero

c) whose lower as well as upper deviations are zero

d) does not exist


9. Standard tolerance unit (i) =

a) 0.55D1/3

+ 0.01D (where D = diameter in mm)

b) 0.45D1/3

+ 0.001D

c) 0.55D1/3

+ 0.001D

d) 0.45D1/3

+ 0.01D


10. I.S. specifies following total number of grades of tolerances

a) 18

b) 16

c) 20

d) 22

e) 14.

11. A bolt

a) has a head on one end and a nut fitted to the other

b) has head at one end and other end fits into a tapped hole in the other part to be

joined

c) has both ends threaded

d) is provided with pointed threads

e) requires no nut.

12. If d is the diameter of bolt hole then for a flanged pipe joint to be leak proof, the

circumferential pitch of the bolts should be


25

a) 10√d

b) 10√d to 15√d

c) 15√d to 20√d

d) 20√d to 30√d

e) 30√d to 40√d.

13. Maximum principal stress theory is applicable for

a) ductile materials

b) brittle materials

c) elastic materials

d) all of the above


14. A stud



joined


d) has pointed threads

e) requires locking nut.

15. Maximum shear stress theory is applicable for

a) ductile materials

b) brittle materials

c) elastic materials

d) all of the above


16. A tap bolt



joined


d) has pointed threads

e) requires locking devices.

17. The included angle in unified of American National threads is

a) 60°

b) 55°

c) 47.5°

d) 29°


18. The included angle in Acme threads is

a) 60°

b) 55°

c) 47.5°

d) 29°


19. The function of a washer is to


25

a) provide cushioning effect

b) provide bearing are

c) absorb shocks and vibrations

d) provide smooth surface in place of rough surface

e) act as a locking device.

20. Cap screws are

a) similar to small size tap bolts except that a greater variety of shapes of heads are

available

b) slotted for a screw driver and generally used with a nut

c) used to prevent relative motion between parts

d) provided with detachable caps

e) similar to studs.

21. An allen bolt is

a) self locking bolt

b) same as stud

c) provided with hexagonal depression in head

d) used in high speed components

e) provided with countersunk head.

22. Ball bearing type screws are found in following application

a) screw jack

b) aeroplane engines

c) crane

d) steering mechanism

e) bench vice.

23. Set screws are


available



d) similar to studs


24. The designation M 33 × 2 of a bolt means

a) metric threads of 33 nos. in 2 cm.

b) metric threads with cross-section of 33 mm2

c) metric threads of 33 mm pitch diameter and 2 mm pitch

d) bolt of 33 mm nominal diameter having 2 threads per cm


25. Machine screws are


available



d) similar to studs


26. Rivets are generally specified by


25

a) thickness of plates to be riveted

b) length of rivet

c) diameter of head

d) nominal diameter

e) all of the above.

27. The edge of a boiler plate are bevelled to an angle of

a) 30°

b) 45°

c) 60°

d) 80°

e) 85°

28. If the tearing efficiency of a riveted joint is 75%, then the ratio of diameter of rivet to

the pitch is equal to

a) 0.2

b) 0.25

c) 0.50

d) 0.60

e) 0.75.

29. Jam nut is a locking device in which

a) one smaller nut is tightened over main nut and main nut tightened against one by

loosening, creating friction jamming

b) a slot is cut partly in middle of nut and then slot reduced by tightening a screw

(c) 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

(d) through slots are made at top and a cotter-pin is passed through these and a hole in

the bolt, and cotter splitted and bent in reverse direction at other end

(e) none of the above.

30. A key capable of tilting in a recess milled out in a shaft is known as

a) wood-ruff key

b) feather key

c) flat saddle key

d) gib head key

e) hollow saddle key.

31. Eye bolts are used for

a) foundation purposes

b) locking devices

c) absorbing shocks and vibrations

d) transmission of power

e) lifting and transportation of heavy machines and cubicles.

32. Elastic nut is a locking device in which




c) a hard fibre or nylon cotter is recessed in the nut and becomes threaded as the nut



25

d) through slots are made at top and a cotter-pin is passed through these and a hole in



33. Applications in which stresses are encountered in one direction only uses following

type of threads

a) metric

b) buttress

c) acme

d) square

e) BSW.

34. A bench vice has following type of threads

a) metric

b) buttress

c) acme

d) square

e) BSW.

35. The valve rod in a steam engine is connected to an eccentric rod by

a) cotter joint

b) bolted joint

c) knuckle joint

d) universal coupling

e) oldham coupling.

36. Split nut is a locking device in which









37. A tube has the following advantage over pipe

a) lighter and easier to handle

b) greater shock absorption

c) smoother inside walls

d) all of the above


38. The strap end of a connecting rod of steam engine is joined by

a) gib and cotter joint

b) sleeve and cotter joint

c) spigot socket cotter joint

d) knuckle joint

e) universal coupling.

39. Castle nut is a locking device in which


25









40. Which of the following pipe joints would be suitable for pipes carrying steam

a) flanged

b) threaded

c) bell and spigot

d) expansion

e) compression.

41. Spring index is

a) ratio of coil diameter to wire diameter

b) load required to produce unit deflection

c) its capability of storing energy

d) indication of quality of spring

e) nothing.

42. Form coefficient of spring is




d) concerned with strength of wire of spring

e) nothing.

43. Spring stiffness is




d) its ability to absorb shocks


44. If a spring is cut down into two halves, the stiffness of cut springs will be

a) half

b) same

c) double

d) unpredictable


45. Belt slip may occur due to

a) heavy load

b) loose belt

c) driving pulley too small

d) all of the above


46. Aircraft body is usually fabricated by


25

a) welding

b) pre-casting

c) riveting

d) casting

e) non-conventional methods.

47. If the two springs are in parallel then their overall stiffness will be

a) half

b) same

c) double

d) unpredictable


48. In V-belt drive, belt touches

a) at bottom

b) at sides only

c) both at bottom and sides

d) could touch anywhere


49. In cross or regular lay ropes

a) direction of twist of wires in strands is opposite to the direction of twist of strands

b) direction of twist of wires and strands are same

c) wires in two adjacent strands are twisted in opposite direction

d) wires are not twisted


50. In parallel lay rope






51. In composite or reverse laid ropes






52. When a bolt is subjected to shock loading, the resilience of the bolt should be

considered in order to prevent breakage at

a) shank

b) head

c) in the middle

d) at the thread

e) anywhere in the bolt.

53. The shock absorbing capacity of a bolt can be increased by

a) tightening it properly

b) increasing shank diameter


25

c) grinding the shank

d) using washer

e) making shank diameter equal to core diameter of the thread.

54. Lowest value of riveted joint efficiency is assumed in the case of

a) single riveted butt joint

b) single riveted lap joint

c) double riveted butt joint

d) double riveted lap joint

e) diamond joint.

55. The stress concentration in a riveted joint with unequal width cover plates as

compared to one with equal width cover plates will be

a) less

b) more

c) equal

d) depends on size of plate and diameter of rivet


56. According to I.B.R., the following type of joint is preferred for longitudinal joint

a) lap joint

b) butt joint

c) welded joint

d) any one of the above


57. Feather keys are generally

a) tight in shaft and loose in hub

b) loose in shaft and tight in hub

c) tight in both shaft and hub

d) loose in both shaft and hub


58. According to I.B.R., the following type of joint is preferred for circumferential joint

a) lap joint

b) butt joint

c) welded joint

d) any one of the above


59. Which key transmits power through frictional resistance only

a) wood-ruff key

b) kennedy key

c) sunk key

d) saddle key

e) feather key.

60. For designing thick cylinders, following equation is used

a) Barlow’s

b) Birnie’s

c) Lame’s

d) Clavarino’s


25


61. Oldham’s coupling is used to connect two shafts which

a) have lateral misalignment

b) whose axes intersect at a small angle

c) are in exact alignment

d) is the simplest type of rigid coupling


62. In the flange coupling the two flanges are coupled together by means of bolts fitted in

a) reamed holes

b) threaded holes

c) gasket holes

d) cast holes


63. Following type of pipe joint is mostly used for pipes carrying water at low pressures

a) socket

b) nipple

c) union

d) compression

e) expansion.

64. Muff coupling is used to join two shafts which






65. Multiple threaded screws

a) increase the efficiency

b) increase the mechanical advantage

c) increase the self-locking feature

d) decrease the efficiency

e) increase the load lifting capacity.

66. Use of large thread angles in lifting machine would result in

a) lower mechanical advantage

b) higher mechanical advantage

c) no change in mechanical advantage

d) lifting the load easily

e) lowering the load easily.

67. Universal coupling is used to join two shafts which






68. The maximum efficiency of a screw jack having square threads and friction angle of

30° will be


25

a) 11%

b) 20%

c) 30%

d) 33%

e) 50%.

69. If α is the helix angle of threads and φ is the angle of friction, then the lifting screw

will be self locking when

a) = φ

b) > φ

c) < φ

d) = 2φ

e) there is no such correlation.

70. Splined shaft is used in applications

a) in which stress concentration due to deep key-way is to be avoided

b) high torque is to be transmitted

c) high r.p.m.

d) calling for axial relative movement between shaft and hub

e) involving locking devices.

71. The Wahl stress factor K for springs of spring index C = D/d = (Mean dia. of coil)

/(wire dia.) is given by

a) (4C-1)/(4C-2) + 0.615/C

b) (C-4)/(4C-4) + 0.615/C

c) (4C-4)/(4C-1) + 0.615/C

d) (4C-1)/(4C-4) + 0.615/C

e) (4C-1)/(C-4) + 0.615/C

72. The spring rate of conical and volute springs, with increase in load

a) remains constant

b) decreases

c) increases

d) increases after the largest active coil starts to “bottom”

e) depends on other considerations.

73. Concentric helical springs should be

a) wound in same direction

b) wound with opposite hand helices

c) could be wound in any direction

d) direction of winding depends on the load to be carried


74. For a shaft subjected to a torque T and bending moment M, the equivalent twisting

moment is

a) {( M2 + T

2 )/2}1/2

b) ( M2 - T

2 )

c) M/2 + ( M2 + T

2 )

1/2

d) ( M2 + T

2 )

1/2

e) {(M/2)2 + T

2 }1/2

75. Stretching in a belt can be controlled by


25

a) decreasing belt length

b) increasing centre distance

c) increasing pulley diameter

d) reducing belt velocity

e) reducing stress in the belt.

76. Centrifugal tension in belts

a) reduces power transmission

b) increases power transmission

c) does not affect power transmission

d) increases power transmission at high speed and decreases it at lower speed

e) unpredictable.

77. If F1 and F2 be the tight and slack side tensions in the belt, then initial tension will be

equal to

a) F1 - F2

b) F1 + F2

c) (F1 + F2 )/2

d) (√F1 + √F2 )2

e) {(√F1 + √F2 )/2}2 .

78. if F, g and w represent the tension, acceleration due to gravity and mass per unit length

of belt respectively, then maximum permissible speed of belt is given by

a) √(Fg / 3w)

b) √(3Fg / w)

c) √(2Fg / 3w)

d) √(Fg / w)

e) √(3Fg / 2w).

79. If If F1, F2 and Fc be the tight side, slack side and centrifugal tensions in a belt, and µ

and θ be the co-efficient of friction between belt and pulley, and angle of contact, then

a) F1/ F2 = eµθ

b) (F1 + Fc)/( (F2 + Fc) = eµθ

c) (F1 + F2) = 4Fc

d) (F1 - Fc)/( (F2 - Fc) = (eµθ

-1)/ eµθ

e) (F1 - Fc)/( (F2 - Fc) = eµθ

80. In replacing the V-belts, a complete set of new belts is used instead of replacing a

single damaged belt because

a) belts are available in set

b) only one belt can’t be fitted with other used belts

c) the new belt would carry more than its share and would have a short life

d) such an arrangement would cause heavy vibration

e) one belt can’t be replaced.

81. A pressure vessel is said to be thin cylinder, if the ratio of wall thickness of the shell

to its diameter is

a) Equal to 1/10

b) Less than 1/10

c) More than 1/10

d) None of these


25

82. In case of pressure vessel s having open ends, the fluid pressure induces

a) Longitudinal stress

b) Circumferential stress

c) Shear stress

d) None of these

e) Both b and c

83. Longitudinal stress is …… of the Circumferential stress

a) 1/2

b) 1/3

c) 2/3

d) 3/4

84. The Design of pressure vessel is based on

a) Longitudinal stress

b) Hoop stress

c) Longitudinal and Hoop stress

d) None of these

85. A thin spherical shell of internal diameter d subjected to an internal pressure p. If t

σ

is the tensile stress for the shell material, then the thickness of the shell is equal to

a) .

t

p d

σ

b) .

2t

p d

σ

c) .

3t

p d

σ

d) .

4t

p d

σ

86. In a thick cylinder shell, the maximum radial stress at the outer surfaces of the shell is

a) 0

b) P

c) –p

d) 2p

87. For high pressure oil and gas cylinders, the thickness of the cylinder is determined by

a) Lame’s equation

b) Clavarino’s equation

c) Barlow’s equation

d) Birnie’s equation

88. According to Indian standards, the diameter of rivet hole for a 24 mm diameter of

rivet, should be

a) 23 mm

b) 24 mm

c) 25 mm

d) 26 mm

89. The centre to centre distance between two consecutive rivets in a row, is called


25

a) Back pitch

b) Marginal pitch

c) Gauge line

d) Pitch line

90. For a parallel load on a fillet weld of equal legs, the plane of maximum shear occurs at

a) 22.5°

b) 30°

c) 45°

d) 60°

91. The standard length of shat is

a) 5 m

b) 6 m

c) 7 m

d) All of the above

e) None of the above

92. A screw is said to be self locking, if its efficiency

a) Less than 50%

b) More than 50%

c) Equal to 50%

d) None of these

93. A screw is said to be self locking, if its efficiency

a) Less than 50%

b) More than 50%

c) Equal to 50%

d) None of these

94. Multiple thread are used to secure

a) Low efficiency

b) High efficiency

c) High load lifting capacity

d) High mechanical advantage

95. Screws are used for power transmission should have

a) Low efficiency

b) High efficiency

c) Very fine threads

d) Strong teeth

96. The groove angle of the pulley for V-belt drive is usually

a) 20 – 25 degree

b) 25 – 32 degree

c) 32 - 38 degree

d) 38 - 45 degree

97. A V-belt designated by A-914-50 denotes

a) A standard belt

b) An oversize belt

c) An undersize belt

d) None of these


25

98. The wire ropes make contact at

a) Bottom of groove of the pulley

b) Side of groove of the pulley

c) Side and bottom of groove of the pulley

d) Any where in the of groove of the pulley

99. The V-belts are particularly suitable for …….. drives

a) Short

b) Long

c) Medium

d) None of these

100. The spring mostly used in gramophones is

a) Helical spring

b) Conical spring

c) Laminated spring

d) Flat spiral spring

question bank machine design a: numerical problems: problems on pin… 603-machine design.pdf ·...

Documents