Design of Machine Elements

The lowest value of joint efficiency is assumed in the case of

Standardization deals with the characteristics of products that include

The gearbox is produced by

Steels used for welded assemblies are

In a shaft-basis system, the basis is

According to Indian Standards, the total number of tolerance grades are

The shock-absorbing capacity of a bolt can be increased by

The maximum stress concentration factor for a rectangular plate with a transverse hole loaded in tension or compression is

The reliability factor for using 50% reliability in design is

The endurance limit of the component can be increased by

Define the factor of safety. What is its importance in design? What are various factors to be considered in deciding the factor of safety?

What are adaptive design and optimum design? Describe some factors that influence machine design.

Describe various types of loads that machine elements are subjected to and specify the factor of safety used in each case.

Explain notch sensitivity. State the relation between stress concentration factor, fatigue stress concentration factor and notch sensitivity.

Explain briefly a design of shafts subjected to combined bending and torsion.

Name the various standards used in the design of machine elements. Calculate the tolerance, fundamental deviation and limits of sizes for the shaft designated as 70 H8-g5.

Explain briefly the design considerations of welded assemblies. How is the strength of the transverse fillet weld evaluated?

A welded rectangular steel tube is $ 1000 \text{ mm} $ long, has a $ 3 \text{ mm} $ wall, and a $ 60 \text{ mm} $ by $ 90 \text{ mm} $ rectangular cross-section. Assume an allowable shear stress of $ 80 \text{ MPa} $ and a shear modulus of $ 80 \text{ GPa} $.

(a) Estimate the allowable torque $ T $.
(b) Estimate the angle of twist due to the torque.

Mention the utility of the centre bolt, U-clamp, rebound clip and camber in a leaf spring.

Design a leaf spring for the following specifications: Total load $ = 140 \text{ kN} $; Number of springs supporting the load $ = 4 $; Maximum number of leaves $ = 10 $; Span of the spring $ = 1000 \text{ mm} $; Permissible deflection $ = 80 \text{ mm} $. Take Young's modulus, $ E = 200 \text{ kN/mm}^2 $ and allowable stress in spring material as $ 600 \text{ MPa} $.

Explain with sketches the different types of failures and efficiencies of the riveted joints.

Discuss the design procedure for the eccentrically loaded bolted joint.

A band brake's drum rotates counterclockwise at $ 200 \text{ rev/min} $. The drum diameter is $ 400 \text{ mm} $ and the band lining is $ 75 \text{ mm} $ wide. The coefficient of friction is $ 0.20 $. The maximum lining interface pressure is $ 480 \text{ kPa} $.

(a) Find the brake torque, necessary force $ P $, and steady-state power.
(b) Complete the free body diagram of the drum. Find the bearing radial load that a pair of straddle-mounted bearings would have to carry.
(c) What is the lining pressure $ p $ at both ends of the contact arc?

A line shaft is to transmit $ 30 \text{ kW} $ at $ 160 \text{ rpm} $. It is driven by a motor placed directly under it by means of a belt running on a $ 1 \text{ m} $ diameter pulley keyed to the end of the shaft. The tension in the tight side of the belt is $ 2.5 $ times that of the slack side, and the centre of the pulley overhangs $ 150 \text{ mm} $ beyond the centre line of the end bearing. Determine the diameter of the shaft if the allowable shear stress is $ 56 \text{ MPa} $ and the pulley weighs $ 1600 \text{ N} $.

The lowest value of joint efficiency is assumed in the case of

Standardization deals with the characteristics of products that include

The gearbox is produced by

Steels used for welded assemblies are

In a shaft-basis system, the basis is

According to Indian Standards, the total number of tolerance grades are

The shock-absorbing capacity of a bolt can be increased by

The maximum stress concentration factor for a rectangular plate with a transverse hole loaded in tension or compression is

The reliability factor for using 50% reliability in design is

The endurance limit of the component can be increased by

Define the factor of safety. What is its importance in design? What are various factors to be considered in deciding the factor of safety?

What are adaptive design and optimum design? Describe some factors that influence machine design.

Describe various types of loads that machine elements are subjected to and specify the factor of safety used in each case.

Explain notch sensitivity. State the relation between stress concentration factor, fatigue stress concentration factor and notch sensitivity.

Explain briefly a design of shafts subjected to combined bending and torsion.

Name the various standards used in the design of machine elements. Calculate the tolerance, fundamental deviation and limits of sizes for the shaft designated as 70 H8-g5.

Explain briefly the design considerations of welded assemblies. How is the strength of the transverse fillet weld evaluated?

A welded rectangular steel tube is $ 1000 \text{ mm} $ long, has a $ 3 \text{ mm} $ wall, and a $ 60 \text{ mm} $ by $ 90 \text{ mm} $ rectangular cross-section. Assume an allowable shear stress of $ 80 \text{ MPa} $ and a shear modulus of $ 80 \text{ GPa} $.

(a) Estimate the allowable torque $ T $.
(b) Estimate the angle of twist due to the torque.

Mention the utility of the centre bolt, U-clamp, rebound clip and camber in a leaf spring.

Design a leaf spring for the following specifications: Total load $ = 140 \text{ kN} $; Number of springs supporting the load $ = 4 $; Maximum number of leaves $ = 10 $; Span of the spring $ = 1000 \text{ mm} $; Permissible deflection $ = 80 \text{ mm} $. Take Young's modulus, $ E = 200 \text{ kN/mm}^2 $ and allowable stress in spring material as $ 600 \text{ MPa} $.

Explain with sketches the different types of failures and efficiencies of the riveted joints.

Discuss the design procedure for the eccentrically loaded bolted joint.

A band brake's drum rotates counterclockwise at $ 200 \text{ rev/min} $. The drum diameter is $ 400 \text{ mm} $ and the band lining is $ 75 \text{ mm} $ wide. The coefficient of friction is $ 0.20 $. The maximum lining interface pressure is $ 480 \text{ kPa} $.

(a) Find the brake torque, necessary force $ P $, and steady-state power.
(b) Complete the free body diagram of the drum. Find the bearing radial load that a pair of straddle-mounted bearings would have to carry.
(c) What is the lining pressure $ p $ at both ends of the contact arc?

A line shaft is to transmit $ 30 \text{ kW} $ at $ 160 \text{ rpm} $. It is driven by a motor placed directly under it by means of a belt running on a $ 1 \text{ m} $ diameter pulley keyed to the end of the shaft. The tension in the tight side of the belt is $ 2.5 $ times that of the slack side, and the centre of the pulley overhangs $ 150 \text{ mm} $ beyond the centre line of the end bearing. Determine the diameter of the shaft if the allowable shear stress is $ 56 \text{ MPa} $ and the pulley weighs $ 1600 \text{ N} $.

18/8 steel contains

The parts of circular cross-section which are symmetrical about the axis of rotation are made by

The ratio of linear stress to linear strain is called

Two shafts will have equal strength, if

A line joining the centres of rivets and parallel to the edge of the plate is known as

In transverse fillet welded joint, the size of weld is equal to

A spring used to absorb shocks and vibrations is

The material used for lining of friction surfaces of a clutch should have ________ coefficient of friction.

A brake commonly used in motorcars is

The number of starts on the worm for a velocity ratio of 40 should be

State the advantages and disadvantages of hot working of metals. Discuss any two hot working processes.

A steel rod of $ 20 \text{ mm} $ diameter passes centrally through a copper tube of external diameter $ 40 \text{ mm} $ and internal diameter $ 20 \text{ mm} $. The tube is closed at each end with the help of rigid washers (of negligible thickness) which are screwed by the nuts. The nuts are tightened until the compressive load on the copper tube is $ 50 \text{ kN} $. Determine the stresses in the rod and the tube, when the temperature of whole assembly falls by $ 50^\circ\text{C} $. Take $ E_s = 200 \text{ GPa} $; $ E_c = 100 \text{ GPa} $; $ \alpha_s = 12 \times 10^{-6}/^\circ\text{C} $ and $ \alpha_c = 18 \times 10^{-6}/^\circ\text{C} $.

How is the shaft designed when it is subjected to twisting moment only?

A mild steel shaft transmits $ 20 \text{ kW} $ at $ 200 \text{ r.p.m.} $. It carries a central load of $ 900 \text{ N} $ and is simply supported between the bearings $ 2.5 \text{ meters} $ apart. Determine the size of the shaft, if the allowable shear stress is $ 42 \text{ MPa} $ and the maximum tensile or compressive stress is not to exceed $ 56 \text{ MPa} $. What size of the shaft will be required, if it is subjected to gradually applied loads?

Classify the rivet heads according to Indian Standard specifications.

Find the efficiency of the following riveted joints:
(i) Single riveted lap joint of $ 6 \text{ mm} $ plates with $ 20 \text{ mm} $ diameter rivets having a pitch of $ 50 \text{ mm} $.
(ii) Double riveted lap joint of $ 6 \text{ mm} $ plates with $ 20 \text{ mm} $ diameter rivets having a pitch of $ 65 \text{ mm} $.
Assume permissible tensile stress in plate $ = 120 \text{ MPa} $, permissible shearing stress in rivets $ = 90 \text{ MPa} $, permissible crushing stress in rivets $ = 180 \text{ MPa} $.

A bracket, carries a load of $ 10 \text{ kN} $. Find the size of the weld if the allowable shear stress is not to exceed $ 80 \text{ MPa} $.

A $ 125 \times 95 \times 10 \text{ mm} $ angle is joined to a frame by two parallel fillet welds along the edges of $ 150 \text{ mm} $ leg. The angle is subjected to a tensile load of $ 180 \text{ kN} $. Find the lengths of weld if the permissible static load per mm weld length is $ 430 \text{ N} $.

With the help of neat sketches, differentiate between single and multi-plate clutches.

A multiple disc clutch, steel on bronze, is to transmit $ 4.5 \text{ kW} $ at $ 750 \text{ r.p.m.} $. The inner radius of the contact is $ 40 \text{ mm} $ and outer radius of the contact is $ 70 \text{ mm} $. The clutch operates in oil with an expected coefficient of $ 0.1 $. The average allowable pressure is $ 0.35 \text{ N/mm}^2 $. Find:
(i) the total number of steel and bronze discs;
(ii) the actual axial force required;
(iii) the actual average pressure;
(iv) the actual maximum pressure.

Discuss the different types of brakes giving at least one practical application for each.

A double-shoe brake is capable of absorbing a torque of $ 1400 \text{ N-m} $. The diameter of the brake drum is $ 350 \text{ mm} $ and the angle of contact for each shoe is $ 100^\circ $. If the coefficient of friction between the brake drum and lining is $ 0.4 $; find:
(i) the spring force necessary to set the brake;
(ii) the width of the brake shoes, if the bearing pressure on the lining material is not to exceed $ 0.3 \text{ N/mm}^2 $.

A $ 15 \text{ kW} $ and $ 1200 \text{ r.p.m.} $ motor drives a compressor at $ 300 \text{ r.p.m.} $ through a pair of spur gears having $ 20^\circ $ stub teeth. The centre-to-centre distance between the shafts is $ 400 \text{ mm} $. The motor pinion is made of forged steel having an allowable static stress as $ 210 \text{ MPa} $ while the gear is made of cast steel having an allowable static stress as $ 140 \text{ MPa} $. Assuming that the drive operates 8 to 10 hours per day under light shock conditions, find from the standpoint of strength:
(a) Module;
(b) Face width and
(c) Number of teeth and pitch circle diameter of each gear.
Check the gears thus designed from the consideration of wear. The surface endurance limit may be taken as $ 700 \text{ MPa} $.

What are springs? Differentiate between helical springs, conical springs and laminated springs with neat sketches. [Image comparing helical, conical, and leaf springs]

Design a close-coiled helical compression spring for a service load ranging from $ 2250 \text{ N} $ to $ 2750 \text{ N} $. The axial deflection of the spring for the load range is $ 6 \text{ mm} $. Assume a spring index of $ 5 $. The permissible shear stress intensity is $ 420 \text{ MPa} $ and modulus of rigidity $ G = 84 \text{ kN/mm}^2 $. Neglect the effect of stress concentration. Draw a fully dimensioned sketch of the spring, showing details of the finish of the end coils.

18/8 steel contains

The parts of circular cross-section which are symmetrical about the axis of rotation are made by

The ratio of linear stress to linear strain is called

Two shafts will have equal strength, if

A line joining the centres of rivets and parallel to the edge of the plate is known as

In transverse fillet welded joint, the size of weld is equal to

A spring used to absorb shocks and vibrations is

The material used for lining of friction surfaces of a clutch should have ________ coefficient of friction.

A brake commonly used in motorcars is

The number of starts on the worm for a velocity ratio of 40 should be

State the advantages and disadvantages of hot working of metals. Discuss any two hot working processes.

A steel rod of $ 20 \text{ mm} $ diameter passes centrally through a copper tube of external diameter $ 40 \text{ mm} $ and internal diameter $ 20 \text{ mm} $. The tube is closed at each end with the help of rigid washers (of negligible thickness) which are screwed by the nuts. The nuts are tightened until the compressive load on the copper tube is $ 50 \text{ kN} $. Determine the stresses in the rod and the tube, when the temperature of whole assembly falls by $ 50^\circ\text{C} $. Take $ E_s = 200 \text{ GPa} $; $ E_c = 100 \text{ GPa} $; $ \alpha_s = 12 \times 10^{-6}/^\circ\text{C} $ and $ \alpha_c = 18 \times 10^{-6}/^\circ\text{C} $.

How is the shaft designed when it is subjected to twisting moment only?

A mild steel shaft transmits $ 20 \text{ kW} $ at $ 200 \text{ r.p.m.} $. It carries a central load of $ 900 \text{ N} $ and is simply supported between the bearings $ 2.5 \text{ meters} $ apart. Determine the size of the shaft, if the allowable shear stress is $ 42 \text{ MPa} $ and the maximum tensile or compressive stress is not to exceed $ 56 \text{ MPa} $. What size of the shaft will be required, if it is subjected to gradually applied loads?

Classify the rivet heads according to Indian Standard specifications.

Find the efficiency of the following riveted joints:
(i) Single riveted lap joint of $ 6 \text{ mm} $ plates with $ 20 \text{ mm} $ diameter rivets having a pitch of $ 50 \text{ mm} $.
(ii) Double riveted lap joint of $ 6 \text{ mm} $ plates with $ 20 \text{ mm} $ diameter rivets having a pitch of $ 65 \text{ mm} $.
Assume permissible tensile stress in plate $ = 120 \text{ MPa} $, permissible shearing stress in rivets $ = 90 \text{ MPa} $, permissible crushing stress in rivets $ = 180 \text{ MPa} $.

A bracket, carries a load of $ 10 \text{ kN} $. Find the size of the weld if the allowable shear stress is not to exceed $ 80 \text{ MPa} $.

A $ 125 \times 95 \times 10 \text{ mm} $ angle is joined to a frame by two parallel fillet welds along the edges of $ 150 \text{ mm} $ leg. The angle is subjected to a tensile load of $ 180 \text{ kN} $. Find the lengths of weld if the permissible static load per mm weld length is $ 430 \text{ N} $.

With the help of neat sketches, differentiate between single and multi-plate clutches.

A multiple disc clutch, steel on bronze, is to transmit $ 4.5 \text{ kW} $ at $ 750 \text{ r.p.m.} $. The inner radius of the contact is $ 40 \text{ mm} $ and outer radius of the contact is $ 70 \text{ mm} $. The clutch operates in oil with an expected coefficient of $ 0.1 $. The average allowable pressure is $ 0.35 \text{ N/mm}^2 $. Find:
(i) the total number of steel and bronze discs;
(ii) the actual axial force required;
(iii) the actual average pressure;
(iv) the actual maximum pressure.

Discuss the different types of brakes giving at least one practical application for each.

A double-shoe brake is capable of absorbing a torque of $ 1400 \text{ N-m} $. The diameter of the brake drum is $ 350 \text{ mm} $ and the angle of contact for each shoe is $ 100^\circ $. If the coefficient of friction between the brake drum and lining is $ 0.4 $; find:
(i) the spring force necessary to set the brake;
(ii) the width of the brake shoes, if the bearing pressure on the lining material is not to exceed $ 0.3 \text{ N/mm}^2 $.

A $ 15 \text{ kW} $ and $ 1200 \text{ r.p.m.} $ motor drives a compressor at $ 300 \text{ r.p.m.} $ through a pair of spur gears having $ 20^\circ $ stub teeth. The centre-to-centre distance between the shafts is $ 400 \text{ mm} $. The motor pinion is made of forged steel having an allowable static stress as $ 210 \text{ MPa} $ while the gear is made of cast steel having an allowable static stress as $ 140 \text{ MPa} $. Assuming that the drive operates 8 to 10 hours per day under light shock conditions, find from the standpoint of strength:
(a) Module;
(b) Face width and
(c) Number of teeth and pitch circle diameter of each gear.
Check the gears thus designed from the consideration of wear. The surface endurance limit may be taken as $ 700 \text{ MPa} $.

What are springs? Differentiate between helical springs, conical springs and laminated springs with neat sketches. [Image comparing helical, conical, and leaf springs]

Design a close-coiled helical compression spring for a service load ranging from $ 2250 \text{ N} $ to $ 2750 \text{ N} $. The axial deflection of the spring for the load range is $ 6 \text{ mm} $. Assume a spring index of $ 5 $. The permissible shear stress intensity is $ 420 \text{ MPa} $ and modulus of rigidity $ G = 84 \text{ kN/mm}^2 $. Neglect the effect of stress concentration. Draw a fully dimensioned sketch of the spring, showing details of the finish of the end coils.

Which of the following parameters can be obtained by tension test of a standard specimen?

Which of the following is the definition of compliance?

Yield strength is defined as the maximum stress at which a marked increase in elongation occurs without increase in

Relative density of aluminium is roughly _______ of steel.

Which of the following are true for aluminium?

In alloy 4450, 4 represents

Ductile cast iron is

Grey cast iron is formed when

Which of the following are true?

Proof strength is defined as the stress which will produce a permanent extension of how much percentage in the gauge length of the standard test specimen?

Two rods, made of plain carbon steel 40C8 $ (S_{yt}=380 \text{ N/mm}^2) $, are to be connected by means of a cotter joint. The diameter of each rod is $ 50 \text{ mm} $ and the cotter is made from a steel plate of $ 15 \text{ mm} $ thickness. Calculate the dimensions of the socket end making following assumptions:
(a) The yield strength in compression is twice of the tensile yield strength.
(b) The yield strength in shear is 50% of the tensile yield strength. The factor of safety is 6.

A component machined from a plate made of steel 45C8 $ (S_{ut}=630 \text{ N/mm}^2) $ is subjected to a completely reversed axial force of $ 50 \text{ kN} $. The expected reliability is 90% and the factor of safety is 2. The size factor is $ 0.85 $. Determine the plate thickness $ t $ for infinite life, if the notch sensitivity factor is $ 0.8 $.

A welded connection is subjected to an eccentric force of $ 7.5 \text{ kN} $. Determine the size of welds if the permissible shear stress for the weld is $ 100 \text{ N/mm}^2 $. Assume static conditions.

A cylindrical pressure vessel with $ 1 \text{ m} $ inner diameter is subjected to internal steam pressure of $ 1.5 \text{ MPa} $. The permissible stresses for the cylinder plate and the rivets in tension, shear, and compression are $ 80 $, $ 60 $ and $ 120 \text{ N/mm}^2 $ respectively. The efficiency of longitudinal joint can be taken as 80% for the purpose of calculating the plate thickness. The corrosion allowance is $ 2 \text{ mm} $. The efficiency of circumferential lap joint should be at least 62%. Design the circumferential lap joint and calculate:
(a) thickness of the plate;
(b) diameter of the rivets;
(c) number of rivets;
(d) pitch of rivets;
(e) number of rows of rivets;
(f) overlap of the plates.

It is required to design a square key for fixing a gear on a shaft of $ 25 \text{ mm} $ diameter. The shaft is transmitting $ 15 \text{ kW} $ power at $ 720 \text{ r.p.m.} $ to the gear. The key is made of steel 50C4 $ (S_{yt}=460 \text{ N/mm}^2) $ and the factor of safety is 3. For key material, the yield strength in compression can be assumed to be equal to the yield strength in tension. Determine the dimension of the key.

Design a muff coupling to connect two steel shafts transmitting $ 25 \text{ kW} $ power at $ 360 \text{ r.p.m.} $. The shafts and key are made of plain carbon steel 30C8 $ (S_{yt}=S_{yc}=400 \text{ N/mm}^2) $. The sleeve is made of grey cast iron FG200 $ (S_{ut}=200 \text{ N/mm}^2) $. The factor of safety for the shaft and key is 4. For sleeve, the factor of safety is 6 based on ultimate strength.

A hard-drawn steel wire extension spring has a wire diameter of $ 0.9 \text{ mm} $, an outside coil diameter of $ 6.3 \text{ mm} $, hook radii of $ r_1=2.7 \text{ mm} $ and $ 2.3 \text{ mm} $, and an initial tension of $ 5 \text{ N} $. The number of body turns is 12.17. From the given information:
(a) determine the physical parameters of the spring;
(b) check the initial preload stress conditions;
(c) find the factors of safety under a static $ 23 \text{ N} $ load.

The following data is given for an open-type V-belt drive:
Diameter of driving pulley $ = 150 \text{ mm} $
Diameter of driven pulley $ = 300 \text{ mm} $
Centre distance $ = 1 \text{ m} $
Groove angle $ = 40^\circ $
Mass of belt $ = 0.25 \text{ kg/m} $
Maximum permissible tension $ = 750 \text{ N} $
Coefficient of friction $ = 0.2 $
Plot a graph of maximum tension and power transmitted against the belt velocity. Calculate the maximum power transmitted by the belt and the corresponding belt velocity. Neglect power losses.

Which of the following parameters can be obtained by tension test of a standard specimen?

Which of the following is the definition of compliance?

Yield strength is defined as the maximum stress at which a marked increase in elongation occurs without increase in

Relative density of aluminium is roughly _______ of steel.

Which of the following are true for aluminium?

In alloy 4450, 4 represents

Ductile cast iron is

Grey cast iron is formed when

Which of the following are true?

Proof strength is defined as the stress which will produce a permanent extension of how much percentage in the gauge length of the standard test specimen?

Two rods, made of plain carbon steel 40C8 $ (S_{yt}=380 \text{ N/mm}^2) $, are to be connected by means of a cotter joint. The diameter of each rod is $ 50 \text{ mm} $ and the cotter is made from a steel plate of $ 15 \text{ mm} $ thickness. Calculate the dimensions of the socket end making following assumptions:
(a) The yield strength in compression is twice of the tensile yield strength.
(b) The yield strength in shear is 50% of the tensile yield strength. The factor of safety is 6.

A component machined from a plate made of steel 45C8 $ (S_{ut}=630 \text{ N/mm}^2) $ is subjected to a completely reversed axial force of $ 50 \text{ kN} $. The expected reliability is 90% and the factor of safety is 2. The size factor is $ 0.85 $. Determine the plate thickness $ t $ for infinite life, if the notch sensitivity factor is $ 0.8 $.

A welded connection is subjected to an eccentric force of $ 7.5 \text{ kN} $. Determine the size of welds if the permissible shear stress for the weld is $ 100 \text{ N/mm}^2 $. Assume static conditions.

A cylindrical pressure vessel with $ 1 \text{ m} $ inner diameter is subjected to internal steam pressure of $ 1.5 \text{ MPa} $. The permissible stresses for the cylinder plate and the rivets in tension, shear, and compression are $ 80 $, $ 60 $ and $ 120 \text{ N/mm}^2 $ respectively. The efficiency of longitudinal joint can be taken as 80% for the purpose of calculating the plate thickness. The corrosion allowance is $ 2 \text{ mm} $. The efficiency of circumferential lap joint should be at least 62%. Design the circumferential lap joint and calculate:
(a) thickness of the plate;
(b) diameter of the rivets;
(c) number of rivets;
(d) pitch of rivets;
(e) number of rows of rivets;
(f) overlap of the plates.

It is required to design a square key for fixing a gear on a shaft of $ 25 \text{ mm} $ diameter. The shaft is transmitting $ 15 \text{ kW} $ power at $ 720 \text{ r.p.m.} $ to the gear. The key is made of steel 50C4 $ (S_{yt}=460 \text{ N/mm}^2) $ and the factor of safety is 3. For key material, the yield strength in compression can be assumed to be equal to the yield strength in tension. Determine the dimension of the key.

Design a muff coupling to connect two steel shafts transmitting $ 25 \text{ kW} $ power at $ 360 \text{ r.p.m.} $. The shafts and key are made of plain carbon steel 30C8 $ (S_{yt}=S_{yc}=400 \text{ N/mm}^2) $. The sleeve is made of grey cast iron FG200 $ (S_{ut}=200 \text{ N/mm}^2) $. The factor of safety for the shaft and key is 4. For sleeve, the factor of safety is 6 based on ultimate strength.

A hard-drawn steel wire extension spring has a wire diameter of $ 0.9 \text{ mm} $, an outside coil diameter of $ 6.3 \text{ mm} $, hook radii of $ r_1=2.7 \text{ mm} $ and $ 2.3 \text{ mm} $, and an initial tension of $ 5 \text{ N} $. The number of body turns is 12.17. From the given information:
(a) determine the physical parameters of the spring;
(b) check the initial preload stress conditions;
(c) find the factors of safety under a static $ 23 \text{ N} $ load.

The following data is given for an open-type V-belt drive:
Diameter of driving pulley $ = 150 \text{ mm} $
Diameter of driven pulley $ = 300 \text{ mm} $
Centre distance $ = 1 \text{ m} $
Groove angle $ = 40^\circ $
Mass of belt $ = 0.25 \text{ kg/m} $
Maximum permissible tension $ = 750 \text{ N} $
Coefficient of friction $ = 0.2 $
Plot a graph of maximum tension and power transmitted against the belt velocity. Calculate the maximum power transmitted by the belt and the corresponding belt velocity. Neglect power losses.

Steels used for automobile bodies and hoods are

Material used for self-lubricated bearing is

In forged components

When a circular shaft is subjected to torque, the torsional shear stress is

The thermal stresses are caused due to

A stress that varies in sinusoidal manner with respect to time from tensile to compressive (or vice versa) and with zero mean is called

In order to find the endurance limit, the rotating beam specimen is subjected to

In design of screw jack from buckling considerations, the end conditions are assumed as

In the running condition, the net force acting on the drum of centrifugal clutch is equal to

The maximum shear stress in spring wire is induced at

What are the factors to be considered for selection of engineering materials for a machine component? Discuss the important manufacturing considerations in machine design.

How will you select direction of fiber lines in forged components?

The force acting on a bolt consists of two components - an axial pull of $ 12 \text{ kN} $ and a transverse shear force of $ 6 \text{ kN} $. The bolt is made of steel having $ S_{yt}=310 \text{ N/mm}^2 $ and factor of safety is 2.5. Determine the diameter of the bolt using the maximum shear stress theory of failure.

A rotating bar made of steel having $ S_{ut}=620 \text{ N/mm}^2 $ is subjected to completely reversed bending stress. The corrected endurance limit of the bar is $ 310 \text{ N/mm}^2 $. Calculate the fatigue strength of the bar for a life of $ 1,00,000 $ cycles.

A forged steel bar of $ 55 \text{ mm} $ diameter is subjected to a reversed bending stress of $ 260 \text{ N/mm}^2 $. The bar is made of 40C8 steel $ (S_{ut}=610 \text{ N/mm}^2) $. Calculate the life of the bar for a reliability of 90%.

A transmission shaft carries a pulley midway between the two bearings. The bending moment at the pulley varies from $ 200 \text{ N-m} $ to $ 600 \text{ N-m} $, as the torsional moment in the shaft varies from $ 70 \text{ N-m} $ to $ 200 \text{ N-m} $. The frequencies of variation of bending and torsional moments of steel FeE 400 $ (S_{yt}=400 \text{ N/mm}^2 $ and $ S_{ut}=540 \text{ N/mm}^2) $. The corrected endurance limit of the shaft is $ 210 \text{ N/mm}^2 $. Determine the diameter of the shaft using a factor of safety of 2.5.

The layout of a wall crane and the pin-joint connecting the tie-rod to the crane post is shown. The tension in the tie rod is maximum, when the load is at a distance of $ 2 \text{ m} $ from the wall. The tie-rod and the pin are made of steel having $ S_{yt}=250 \text{ N/mm}^2 $ and factor of safety is 3.0. Determine the diameter of the tie rod and the pin.

A gearbox weighing $ 6 \text{ kN} $ is provided with a steel eyebolt for lifting and transporting on the shop floor. The eyebolt is made of 30C8 steel $ (S_{yt}=380 \text{ N/mm}^2) $ and factor of safety is 5. Determine the nominal diameter of the eyebolt having coarse threads if $ d_c=0.8d $ where $ d_c $ and $ d $ are the core and major diameters respectively.

A cylindrical pressure vessel with a $ 0.8 \text{ m} $ inner diameter is subjected to an internal steam pressure of $ 2 \text{ MPa} $. The permissible stresses for cylinder plate and rivets in tension, shear and compression are $ 80 $, $ 60 $ and $ 120 \text{ N/mm}^2 $ respectively. The efficiency of longitudinal joint can be taken as 80% for calculating the plate thickness. The corrosion allowance is $ 2 \text{ mm} $. The efficiency of circumferential lap joint should be at least 62%. Design the circumferential lap joint and calculate the thickness of plate, diameter of the rivets, number of rivets and pitch of rivets.

Steels used for automobile bodies and hoods are

Material used for self-lubricated bearing is

In forged components

When a circular shaft is subjected to torque, the torsional shear stress is

The thermal stresses are caused due to

A stress that varies in sinusoidal manner with respect to time from tensile to compressive (or vice versa) and with zero mean is called

In order to find the endurance limit, the rotating beam specimen is subjected to

In design of screw jack from buckling considerations, the end conditions are assumed as

In the running condition, the net force acting on the drum of centrifugal clutch is equal to

The maximum shear stress in spring wire is induced at

What are the factors to be considered for selection of engineering materials for a machine component? Discuss the important manufacturing considerations in machine design.

How will you select direction of fiber lines in forged components?

The force acting on a bolt consists of two components - an axial pull of $ 12 \text{ kN} $ and a transverse shear force of $ 6 \text{ kN} $. The bolt is made of steel having $ S_{yt}=310 \text{ N/mm}^2 $ and factor of safety is 2.5. Determine the diameter of the bolt using the maximum shear stress theory of failure.

A rotating bar made of steel having $ S_{ut}=620 \text{ N/mm}^2 $ is subjected to completely reversed bending stress. The corrected endurance limit of the bar is $ 310 \text{ N/mm}^2 $. Calculate the fatigue strength of the bar for a life of $ 1,00,000 $ cycles.

A forged steel bar of $ 55 \text{ mm} $ diameter is subjected to a reversed bending stress of $ 260 \text{ N/mm}^2 $. The bar is made of 40C8 steel $ (S_{ut}=610 \text{ N/mm}^2) $. Calculate the life of the bar for a reliability of 90%.

A transmission shaft carries a pulley midway between the two bearings. The bending moment at the pulley varies from $ 200 \text{ N-m} $ to $ 600 \text{ N-m} $, as the torsional moment in the shaft varies from $ 70 \text{ N-m} $ to $ 200 \text{ N-m} $. The frequencies of variation of bending and torsional moments of steel FeE 400 $ (S_{yt}=400 \text{ N/mm}^2 $ and $ S_{ut}=540 \text{ N/mm}^2) $. The corrected endurance limit of the shaft is $ 210 \text{ N/mm}^2 $. Determine the diameter of the shaft using a factor of safety of 2.5.

The layout of a wall crane and the pin-joint connecting the tie-rod to the crane post is shown. The tension in the tie rod is maximum, when the load is at a distance of $ 2 \text{ m} $ from the wall. The tie-rod and the pin are made of steel having $ S_{yt}=250 \text{ N/mm}^2 $ and factor of safety is 3.0. Determine the diameter of the tie rod and the pin.

A gearbox weighing $ 6 \text{ kN} $ is provided with a steel eyebolt for lifting and transporting on the shop floor. The eyebolt is made of 30C8 steel $ (S_{yt}=380 \text{ N/mm}^2) $ and factor of safety is 5. Determine the nominal diameter of the eyebolt having coarse threads if $ d_c=0.8d $ where $ d_c $ and $ d $ are the core and major diameters respectively.

A cylindrical pressure vessel with a $ 0.8 \text{ m} $ inner diameter is subjected to an internal steam pressure of $ 2 \text{ MPa} $. The permissible stresses for cylinder plate and rivets in tension, shear and compression are $ 80 $, $ 60 $ and $ 120 \text{ N/mm}^2 $ respectively. The efficiency of longitudinal joint can be taken as 80% for calculating the plate thickness. The corrosion allowance is $ 2 \text{ mm} $. The efficiency of circumferential lap joint should be at least 62%. Design the circumferential lap joint and calculate the thickness of plate, diameter of the rivets, number of rivets and pitch of rivets.

Give two examples of bearing pressure and crushing stress in the design consideration of machine elements.

A hollow shaft and a solid shaft are of equal weight. The hollow shaft has

If a helical coil spring of stiffness K is cut into two identical half coil springs, the stiffness of each of these half spring will be _________.

Cast iron is widely used for machine frames. Give two reasons.

Give the composition of $ 25Cr_4Mo_2 $.

The resistance of fatigue of a material is measured by

What is the minimum efficiency required for the circumferential boiler joint?

Why are multiple threaded screws not recommended in screw jack?

Suggest suitable coupling for shafts with parallel misalignment.

Name the three stresses induced in belt due to power transmission.

Design a cotter joint, made of 30C8 steel, to support a load of $ 50 \text{ kN} $ which is subjected to slow reversals of direction.

Determine the main dimensions of the longitudinal joints of a boiler whose inner diameter is $ 1.7 \text{ m} $ and pressure of steam is $ 20 \text{ bar} $. The allowable tensile, crushing and shear stresses of mild steel rivet are $ 80 \text{ N/mm}^2 $, $ 120 \text{ N/mm}^2 $ and $ 65 \text{ N/mm}^2 $ respectively. Assume quadruple rivetted, zig-zag butt joint with unequal cover plates.

Determine the size of the welds to support by means of fillet welds of a beam of rectangular cross-section as shown in the figure below if the permissible shear stress in the weld is limited to $ 75 \text{ N/mm}^2 $.

A mild steel shaft has to transmit $ 70 \text{ kW} $ at $ 240 \text{ r.p.m.} $. The allowable shear stress in the shaft material is limited to $ 45 \text{ MPa} $ and the angle of twist is not to exceed $ 1^\circ $ in a length of $ 20 $ times the shaft diameter. Determine the shaft diameter and design a cast iron flange coupling of protected type for the shaft. The shear stress in the coupling bolts is to be limited to $ 30 \text{ MPa} $.

Design a screw jack for lifting a load of $ 20 \text{ kN} $ through a distance of $ 200 \text{ mm} $.

A safety valve of $ 60 \text{ mm} $ diameter is to blow off at a pressure of $ 12 \text{ bar} $. It is held on its seat by a close-coiled helical spring. The maximum lift of the valve is $ 10 \text{ mm} $. Determine main dimensions of a compression spring of spring index 5. Take initial compression of the spring as $ 35 \text{ mm} $. The maximum shear stress in the material of the spring wire is to be limited to $ 500 \text{ N/mm}^2 $. Take $ C=82 \text{ GPa} $.

A crossed belt drive is to transmit $ 10 \text{ kW} $ at $ 1200 \text{ r.p.m.} $ of the smaller pulley which is $ 250 \text{ mm} $ in diameter. The velocity ratio is 2 and centre distance is $ 1.2 \text{ m} $. It is desired to use a $ 6 \text{ mm} $ thick leather belt with coefficient of friction equal to $ 0.25 $. If the permissible stress for the belt material is $ 2 \text{ N/mm}^2 $, determine the width of the belt. Take the mass density of the belt material as $ 1000 \text{ kg/m}^3 $.

A single-disc clutch is required to resist a maximum torque $ 500 \text{ N-m} $. The outer radius of the friction lining is 30% more than the inner radius. The permissible intensity of pressure between the contact surfaces is $ 0.08 \text{ N/mm}^2 $. The coefficient of friction is $ 0.25 $. Eight helical compression springs are used to provide axial force necessary to engage the clutch. If the stiffness of each spring is $ 36 \text{ N/mm} $, determine the size of the friction lining and initial compression in the spring.

Give two examples of bearing pressure and crushing stress in the design consideration of machine elements.

A hollow shaft and a solid shaft are of equal weight. The hollow shaft has

If a helical coil spring of stiffness K is cut into two identical half coil springs, the stiffness of each of these half spring will be _________.

Cast iron is widely used for machine frames. Give two reasons.

Give the composition of $ 25Cr_4Mo_2 $.

The resistance of fatigue of a material is measured by

What is the minimum efficiency required for the circumferential boiler joint?

Why are multiple threaded screws not recommended in screw jack?

Suggest suitable coupling for shafts with parallel misalignment.

Name the three stresses induced in belt due to power transmission.

Design a cotter joint, made of 30C8 steel, to support a load of $ 50 \text{ kN} $ which is subjected to slow reversals of direction.

Determine the main dimensions of the longitudinal joints of a boiler whose inner diameter is $ 1.7 \text{ m} $ and pressure of steam is $ 20 \text{ bar} $. The allowable tensile, crushing and shear stresses of mild steel rivet are $ 80 \text{ N/mm}^2 $, $ 120 \text{ N/mm}^2 $ and $ 65 \text{ N/mm}^2 $ respectively. Assume quadruple rivetted, zig-zag butt joint with unequal cover plates.

Determine the size of the welds to support by means of fillet welds of a beam of rectangular cross-section as shown in the figure below if the permissible shear stress in the weld is limited to $ 75 \text{ N/mm}^2 $.

A mild steel shaft has to transmit $ 70 \text{ kW} $ at $ 240 \text{ r.p.m.} $. The allowable shear stress in the shaft material is limited to $ 45 \text{ MPa} $ and the angle of twist is not to exceed $ 1^\circ $ in a length of $ 20 $ times the shaft diameter. Determine the shaft diameter and design a cast iron flange coupling of protected type for the shaft. The shear stress in the coupling bolts is to be limited to $ 30 \text{ MPa} $.

Design a screw jack for lifting a load of $ 20 \text{ kN} $ through a distance of $ 200 \text{ mm} $.

A safety valve of $ 60 \text{ mm} $ diameter is to blow off at a pressure of $ 12 \text{ bar} $. It is held on its seat by a close-coiled helical spring. The maximum lift of the valve is $ 10 \text{ mm} $. Determine main dimensions of a compression spring of spring index 5. Take initial compression of the spring as $ 35 \text{ mm} $. The maximum shear stress in the material of the spring wire is to be limited to $ 500 \text{ N/mm}^2 $. Take $ C=82 \text{ GPa} $.

A crossed belt drive is to transmit $ 10 \text{ kW} $ at $ 1200 \text{ r.p.m.} $ of the smaller pulley which is $ 250 \text{ mm} $ in diameter. The velocity ratio is 2 and centre distance is $ 1.2 \text{ m} $. It is desired to use a $ 6 \text{ mm} $ thick leather belt with coefficient of friction equal to $ 0.25 $. If the permissible stress for the belt material is $ 2 \text{ N/mm}^2 $, determine the width of the belt. Take the mass density of the belt material as $ 1000 \text{ kg/m}^3 $.

A single-disc clutch is required to resist a maximum torque $ 500 \text{ N-m} $. The outer radius of the friction lining is 30% more than the inner radius. The permissible intensity of pressure between the contact surfaces is $ 0.08 \text{ N/mm}^2 $. The coefficient of friction is $ 0.25 $. Eight helical compression springs are used to provide axial force necessary to engage the clutch. If the stiffness of each spring is $ 36 \text{ N/mm} $, determine the size of the friction lining and initial compression in the spring.