DESIGN OF MACHINE MEMBERS I ASSIGNMENT

Transcription

1 SHRI VISHNU ENGINEERING COLLEGE FOR WOMEN DESIGN OF MACHINE MEMBERS I ASSIGNMENT UNIT I 1 a). Draw stress strain diagram for the ductile and brittle material and compare them? show the salient points on it and b). A steel rope of cross sectional area 100sq.mm is made up of strands 1mm in diameter having an allowable tensile stress, of 168MPa and an ultimate load of 130KN. The rope is used with factor of safety of 8. If 10 strands are broken along a pitch of lay of the strands, is the rope fit for further use? 2.a). Explain the manufacturing considerations in design? b). A belt is required to transmit 19KW from a pulley running at a mean speed of 20m/sec, the angle of contact between the belt and pulley is 1600, and the coefficient of friction is The safe working stress for the belts is 3MPa and the thickness of the belt is 6mm. determine the width of the belt required. 3. a). What are the basic requirements of machine elements? Explain b). A bolt is subjected to a direct tensile load of 20KN and shear load of 15KN. Suggest the suitable size of the bolt according to various theories of elastic failure, if the yield stress in simple tension is 360MPa. A factor of safety of 3 should be used. Take poisons ratio as a). State the application of cotter joint? Explain various types of failure to be considered in designing a cotter joint. Write down strength equation for each failure, along with necessary diagrams. b). Calculate the diameter of the wrought iron rod which is to be under a compressive load of 350 KN in order that the allowable unit stress may not exceed one fourth of the elastic limit which is 210 MPa 5 (a) Explain the need in computing endurance limit of given component. (b) A pulley is keyed to a shaft midway between two anti- friction bearings. The bending moment at the pulley varies from 250 kn-mm to 750 kn-mm and the torsional moment in the shaft varies from 100 kn-mm to 300 kn-mm. The frequency of the variation of the load is same as the shaft speed. The shaft is made of a cold drawn steel having an ultimate strength of 550 N/mm2 and yield strength of 450 N/mm2. Determine the required diameter for an infinite life. The stress concentration factor for the key way in bending and torsion may be taken as 1.8 and 1.5 respectively. The factor of safety is 2.0. Take size factor =0.85 and surface finish factor= (a) Define factor of safety under static and fluctuating loads. (b) A steel connecting rod is subjected to a completely reversed axial load of 16 kn. Suggest the suitable diameter of the rod using a factor of safety 2. The ultimate tensile strength of the material is N/mm2, and yield strength 9300 N/mm2. Neglect column action and the effect of stress concentration.

2 7. (a) A punching press is required to punch a maximum hole size of 30 mm diameter in a material having ultimate shear strength of 350 N/mm2. If the thickness of the sheet is 6 mm, design the screw and the nut. (b) An eye bolt is to be used for lifting a load of 100 kn. Find the nominal diameter of the bolt, if the tensile stress is not to exceed 130 N/mm2 8. A round shaft is made of cold finished steel is subjected to a variable torque whose maximum values is 700 N-m. For a factor of safety of 1.5 on the Soderberg criterion, determine the diameter of the shaft if: (a) The torque is reversed (b) The torque varies from zero to maximum and (c) The torque varies from 300 N-m to a maximum. 9. (a) Define the terms: i. Stress area ii. Pitch iii. Major diameter related to screw fastenings: (b) The base of a pillar crane is fastened to the foundation by 12 bolts spaced equally on a bolt circle of diameter 2 m. The diameter of the pillar base is 2.5 m. Determine the size of bolts when the crane carries a load of 150 kn at a distance of 6 m from the centre of the base. The allowable stress for the bolt material is 170 N/mm A steam engine of effective diameter 400 mm is subjected to a steam pressure of 2 N/mm 2. The cylinder cover is connected by means of 6 bolts having yield strength of 450 N/mm 2 and endurance limit of 275 N/mm 2. The bolts are tightened with an initial preload of 2.5 times that of steam force. A soft copper gasket is used to make a leak proof joint. The stress concentration factor is 2.5 Determine the size of the bolts. 11. (a) Define factor of safety under static and fluctuating loads. (b) A steel connecting rod is subjected to a completely reversed axial load of 16 kn. Suggest the suitable diameter of the rod using a factor of safety 2. The ultimate tensile strength of the material is N/mm2, and yield strength 9300 N/mm2. Neglect column action and the effect of stress concentration. 12. (a) Explain the situation where the flexible couplings are selected? (b) Design a protective type flange coupling for the following requirements. Power to be transmitted is 15 kw at 1440 rpm. Flange material is Cast Iron. Shafts and keys are made of medium steel. Assuming appropriate factors, calculate the dimensions of coupling. UNIT II 1. a). Show the relationship between Goodman s, Soderberg s and Modified Goodman s lines and explain b). The life of a machine component under heavy test load was 10 hours. The life under combined loading was 18 hours of which 9.8 hours was at heavy load and 8.2 hours was at the normal load. Find the expected life under the normal operating load.

3 2. A part with a machined surface is subjected to a reversed bending stress of 600 MPa for 10% of time, a reversed bending stress of 500Mpa for 40% of time and a reversed bending stress of 400Mpa for 50% of time. Determine the expected life of the part in cycles. 3. a). What is notch sensitivity? Explain b). A steel connecting rod is subjected to a completely reversed axial load of 100KN. Suggest the suitable size of the rod using a factor of safety 2. The ultimate strength of thr material is 1100 MPa and Yield strength 930 MPa. The value of A factor for correction for type of loading may be taken as 0.85 and size factor as Neglect the column action and effect of stress concentration. 4. a). Explain the methods to reduce stress concentration with neat diagrams b). A 50 mm diameter shaft made from carbon steel hardened to 180 BHN is subjected to a torque which fluctuates between 2000Nm to -800Nm. Calculate the factor of safety by soderberg method. 5. (a) What is caulking and why is it necessary? (b) A double riveted lap joint is made between 20 mm thick plates. The rivet diameter and pitch are 30 mm and 80 mm respectively. If the ultimate stresses are 450 N/mm2 in tension and 350 N/mm2 in shear and 540 N/mm2 in crushing, find the minimum force per meter, which will rupture the joint. If the above joint is subjected to a load such that the factor of safety is 3, find out the actual stresses developed in the plates and the rivets 6. (a) Describe various types of keys. (b) Design and draw a sleeve and cotter joint to connect two rods to transmit maximum tensile load of 100 kn. Assume sleeve, cotter and rods are made of same material and design stresses in the material are 75 N/mm2 in tension, 150 in crushing and 45 N/mm2 in shear. 7. (a) Explain the various factors to be considered for factor of safety in machine design. (b) Explain Indian Standard systems of limits and fits. 8. (a) Classify the keys and state their applications. (b) A gear is fastened by means of sunk key to the shaft subjected to the torsion only. i. Find the ratio of sectional areas of shaft and key, for equality of strength of the key and shaft ii. Find the length of the key of 20 mm width on 70 mm diameter shaft. The permissible shear stress for the key and the shaft materials is 50 and 60N/mm2 respectively 9. Design a shaft coupling to transmit 100 kw at 1230 rpm. The permissible stresses for the coupling and key are 75, 45 and 120 N/mm2 in tension, shear and compression respectively. Draw freehand sketch of the coupling showing important dimensions 10. (a) A punching press is required to punch a maximum hole size of 30 mm diameter in a material having ultimate shear strength of 350 N/mm2. If the thickness of the sheet is 6 mm, design the screw and the nut. (b) An eye bolt is to be used for lifting a load of 100 kn. Find the nominal diameter of the bolt, if the tensile stress is not to exceed 130 N/mm2.

4 11. (a) Explain the details of shaft design based on: i. Torsional rigidity ii. Lateral rigidity. (b) A centrifugal circulating pump for a steam turbine condenser is to be connected to a motor through a short shaft and a pair of flexible couplings. The pump delivers liters/minute at 1000 rpm against a dynamic head of 10 m. The pump efficiency is 75%. Assuming a permissible shear stress of 65 N/mm2, determine the diameter of the shaft required UNIT III 1. a). What are the regions of replacing riveted joint by welded joint in modern equipment? Explain b). A double riveted double strap butt joint is used to connect two plates, each of 12mm thickness, by means of 16mm diameter rivets having a pitch of 48mm. The rivets and plates are made of steel. The permissible stresses in tension, shear and compression are 80 N/MM2, 60 N/MM2 and 120 N/MM2 respectively. Determine the efficiency of the joint 2. a). What are the different types of riveted joints? Draw any two types of riveted joints? b). A double riveted double strap butt joint is used to connect two plates, each of 12mm thickness, by means of 16mm diameter rivets having a pitch of 48mm. the rivets and plates are made of steel. The permissible stresses in tension, shear and compression are 80, 60 and 120 N/MM2 respectively. Determine the efficiency of the joint 3. a). Derive strength equation of the butt joint. b). A spherical gas tank is made of 10mm steel plate hemispheres butt welded together. The tank is 15m in diameter. Determine the allowable internal pressure to which the tank may be subjected if the permissible stress be limited to 84MPa. 4. a). Explain the basic procedure for design of longitudinal butt-joint and circumferential lap joint for cylindrical boiler shell b). A cylindrical pressure vessel with 1m inside diameter is subjected to internal steam pressure of 1.5 MPa. The permissible stresses for the cylinder plate and the rivets in tension, shear and compression are 80, 60 and 120 N/MM2 respectively. The efficiency of longitudinal joint can be taken as 80% for the purpose of calculating the plate thickness. The efficiency of circumferential lap joint should be at least 62%. Design the circumferential lap joint? 5. (a) Describe the various factors considered in the design of machine members. (b) The maximum tension in the lower link of a potter governor is 750 N and maximum stress in the link is 30 N/mm2. If the link is of rectangular cross section having the length is of twice its width, determine its length and width. 6. (a) Differentiate between a helical torsion spring and a spiral spring. (b) A close coiled helical compression springs of 12 active coils has a spring stiffness

5 of P0. It is cut in to two springs having 5 and 7 turns. Determine spring stiffnesses of resulting springs. 7. (a) List out functions of springs with suitable examples. (b) A helical spring is to support a load of 2 kn. The spring is guided by a rod of 55 mm diameter. The spring undergoes a deection of 42 mm under the load. Determine the diameter of the wire and the number of turns required. Use C-60 steel with a factor of safety of 2.5. Assume suitable necessary data: 8. (a) Define the terms i. pitch ii. Nominal diameter iii. Root diameter corresponding to bolted joints. (b) A anged bearing is fastened to a frame by means of 6 bolts spaced equally on 550 mm bolt circle. The diameter of bearing ange is 750mm and a load of 200 kn acts at a distance 350 mm from the frame. Determine the size of the bolts, assuming tensile stress as 120 N/mm2 for the bolts. 9. (a) Enumerate the common materials used in engineering design? (b) Explain how can the properties of materials be improved for any two materials. 10. (a) Differentiate between a at key and feather key. (b) A square key is to be used to key a gear to a 50 mm diameter shaft. The length of the hub of the gear is 80 mm. Both shaft and key are made of same material, having an allowable shear stress of 65 N/mm2. What are the minimum dimensions of the key if 300 N-m of torque is to be transmitted. 11. (a) Describe various types of keys. (b) Design and draw a sleeve and cotter joint to connect two rods to transmit maximum tensile load of 100 kn. Assume sleeve, cotter and rods are made of same material and design stresses in the material are 75 N/mm2 in tension, 150 in crushing and 45 N/mm2 in shear. 12. (a) Explain various factors effecting endurance limit in the case of a ductile material. (b) Determine the diameter of a circular rod made of ductile material with a fatigue strength (completely stress reversal) _e = 280 N/mm2 and a tensile yield strength of 550 N/mm2. The member is subjected to a varying axial load from 1050 kn to kn. Assume Kt=1.7 and F.S=1.25 UNIT IV 1.a). Draw the profile of ISO Metric screw thread? mark and Explain the silent points on it b). A cylinder head of steam engine is held in position by M20 bolts. The effective diameter of cylinder is 300 mm and steam pressure 1.5N/MM 2. Assume that the bolts are not stressed initially, fined the number of bolts required, if the tensile stress in the bolt is not to exceed 50N/MM 2 2.a). What are the different types of locking devices? Explain any two with neat sketches?

6 b).prove that the maximum principle stress in the tie rods of the turnbuckle is 1.2 times of the direct tensile stress 3. a). What are the different types of set screws? Draw any three set screws with neat sketches? Give their applications b). A cylinder head is connected to the cylinder flange by means of 16bolts. The inner diameter of the cylinder is 400 mm. the maximum pressure inside the cylinder is limited to 1.25N/MM2+. The bolts are made of plain carbon steel 30CB( Syt=400N/MM2) and factor of safety is 5.5. Neglecting the effect of initial tightening. Determine the size of bolts 4. a). What do you understand by bolt of uniform strength? Explain b). A M27 bolt has an effective length of 600mm and is subjected to an impact load which is equivalent to a load of 1000N acting through a free distance of 5mm. determine the unit stress in a standard bolt and is a bolt of uniform strength. What size hole must be drilled in a bolt to make it a bolt of uniform strength? Assume the modulus of elasticity to be 210GPa. 5. Design a cast iron protective type ange coupling to transmit 16 kw at 900 rpm from an electric motor to a compressor. The service factor may be assumed as 1.5. The following permissible stresses may be used: Shear stress for shaft, bolt and key material is 60 N/mm2, Crushing stress for bolt and key is 70 N/mm2, Shear stress for cast iron is 10 N/mm2. Draw a neat sketch of the coupling. 6. Design a bushed-pin type flexible coupling for connecting the shafts of an electric motor, and centrifugal pump. The shaft diameters are 50 and 40 mm respectively. The power to be transmitted is 75 kw at 850 rpm. Take the bearing pressure on the rubber bush as 0.75 N/mm2, normal stress for pins as 65 N/mm2, shear and crushing stresses for the key as 55 N/mm2 and 95 N/mm2 respectively 7. A machine shaft supported on bearings having their centers 750mm apart, transmits 185 kw at 700 r.p.m. A gear of 200 mm and 200 pressure angle is located 250mm to the right of the left hand bearing and a 450 mm diameter pulley is mounted at 200 mm to the right of left hand bearing. The gear is driven by a pinion with a downward tangential force, while the pulley drives a horizontal belt having 1800 angle of contact. The pulley weighs 1 kn and tension ratio is 3. Find the diameter of the shaft, if the allowable shear stress of the material is 65 N/mm2. 8. (a) What is a knuckle joint? where it is used? (b) Design a knuckle joint to transmit 140 kn force, with permissible stresses in tension, shear and compression are 75 N/mm2, 60 N/mm2 150 N/mm2 respectively 9. (a) What is riveted joint? Explain the necessity of riveted joint in pressure vessels. (b) A double riveted lap joint is made between 18 mm thick plates. The rivet diameter and pitch are 30 mm and 80 mm respectively. If the ultimate stresses are 200 N/mm2 in tension, 160 N/mm2 in shear and 420 N/mm2 in crushing, find the minimum force per pitch which will rupture the joint. If the joint is subjected to a load such that the factor of safety is1.5, find out the actual stresses developed in the plates and the rivets.

7 10. A Power is transmitted to a shaft supported on bearings, 1000mm apart, by a belt drive, running on a 550 mm pulley, which overhangs the right bearing by 300 mm. Power is transmitted from the shaft through a belt drive, running on a 350 mm pulley, located mid-way between the bearings.the belt drives are at right angle to each other, and the ratio of belt tensions is 3.5 with the maximum tension in both the belts being limited to 4 kn. Determine the diameter of the shaft, assuming permissible stress as 65 N/mm2. Indicate the assumptions made, if any. Draw the BM & S.F diagrams. 11. (a) Under what circumstances concentric springs are preferred? (b) A load of 2 kn is dropped axially on a close coiled helical compression spring from a height of 260 mm. The spring has 16 active coils. Take wire diameter as 20 mm, spring index as 8. Determine the deection and stress induced in the spring. Take G= 0.84 _ 105 N/mm (a) Classify the rivet heads according to Indian Standard Specification. (b) A double riveted double cover butt joint in plates 20 mm thick is made with 25 mm diameter rivets at 100 mm pitch. The permissible stresses are Pt = 120 N/mm2, Ps = 100 N/mm2, and Pc = 150 N/mm2. Find the efficiency of the joint, taking the strength of the rivet in double shear as twice than that of single shear UNIT V 1. a). What are the different keys? Draw any four keys with neat sketches b). The standard cross section for a flat key, which is fitted on a 50mm diameter shaft is 16X10mm. The key is transmitting 475 N-M torque from the shaft to the hub. The key is made of commercial steel (Syt=Syc=230 N/mm2). Determine the length of the key, if the factor of safety is 3 2). Two rods are connected by means of a cotter joint. The inside diameter of the socket and outside diameter of the socket collar are 50 and 100 mm respectively. The rods are subjected to a tensile force of 50Kn,. The cotter is made of steel 30C8 (Syt=400 N/MM2). And the factor of safety is 4. The width of the cotter is five times of thickness. Calculate a). width and thickness of the cotter on the basis of shear failure and b). width and thickness of the cotter on the basis of bending failure 3. Two rods, made of steel 40C8 (Syt=380 N/MM2), are to be connected by means of a cotter joint. The diameter of each rod is 50mm and the cotter is made from a steel plate of 15mm thickness. Calculate the dimensions of the socket end making following assumptions: a). The yield strength in compression is twice the tensile yield strength b). the yield strength in shear is 50% of the tensile yield strength 4. Two rods, subjected to tensile force of 30KN, are connected by means of knuckle joint. The thickness of each eye of the fork at the end of one is 25mm, while the thickness of eye end of the other rod is 50mm. The knuckle pin is made of steel 30C8 (Syt=400 N/MM2) and factor of safety is 5. Calculate a. the diameter of the pin on the basis of shear strength and on the basis of bending strength the factor of safety is 6

8 5. (a) Under what circumstances concentric springs are preferred? (b) A load of 2 kn is dropped axially on a close coiled helical compression spring from a height of 260 mm. The spring has 16 active coils. Take wire diameter as 20 mm, spring index as 8. Determine the deflection and stress induced in the spring. Take G= 0.84 _ 105 N/mm2. 6. (a) What are the applications of a cotter joint? (b) Describe the design procedure of a gib and cotter joint. 7. (a) Explain the effect of the following factors on the type of fatigue failure. i. Stress distribution ii. Manner of loading iii. Strain rate (b) Find the diameter of a shaft made of Manganese steel having the ultimate tensile strength as 6 N/mm2 and yield stress as 4.4 N/mm2. The shaft is subjected to completely reversed axial load of 100 kn. Neglect stress concentration factor and assume surface _nish factor as 0.8 and size factor as (a) Develop an expression for the maximum shear stress induced in all around circular _llet weld subjected to Torsion. (b) A plate 100 mm wide and 10 mm thick is to be welded with another plate by means of transverse welds at the ends. If the plates are subjected to a load of 70 kn, _nd the size of weld for static as well as fatigue load. The permissible tensile stress should not exceed 70 N/mm2. 9. A rail carriage weighing 250 kn and running at 1.5 m/s is brought to rest by four buffer springs of close coiled helical type during connection with another carriage which is already at rest. The mean coil diameter is 6 times the wire diameter. The deflection of each spring is 220mm, to bring the carriage to rest. Safe shear stress for the spring material is 400N/mm2. Calculate the maximum load on the spring, diameter of wire and coil, number of turns and free length of spring. Assume the ends of spring are squared and ground. Take G = 0.8_104N/mm2 10. (a) Why the compression springs are predominantly used compared to the extension springs? (b) A spring for spring balance is to elongate 100 mm, when subjected to a load of 200 N. Assume that the mean diameter of the coil is to be 5 times the diameter of the wire and the maximum stress to be induced is limited to 400 N/mm 2. Determine the diameter for the wire, for the coil and the number of coils required and length of spring. Modulus of rigidity (G) is N/mm (a) Classify different types of riveted joints and rivets. (b) A low carbon steel plate of 75 mm width welded to a structure of similar material by means of two parallel fillet welds of 120 mm length each is subjected to an eccentric load of 50 kn, the line of action of which has a distance of 110 mm from the center of gravity of the weld group. Design the required thickness of the plate when the allowable stress of the weld metal is 70 N/mm2 and that of the plate is 50 N/mm (a) Explain the classification of engineering materials based on their properties and applications.

9 (b) Differentiate between High speed steel and spring steel UNIT VI 1. A rotating shaft, 15 mm in diameter, is made of plain carbon steel FeE400 (Syt=400 N/mm2).It is subjected to axial tensile force of 3kN, steady torsional moment of 65 N-m and maximum bending moment of 50 N-m. Calculate the factor of safety based on (i)maximum principal stress theory and (ii) Maximum shear stress theory. 2. A propeller shaft is required to transmit 45kW power at 500 rpm. It is a hollow shaft, having inside diameter 0.6 times of outside diameter. It is made of plain carbon steel and the permissible shear stress is 84 N/mm2. Calculate the inside and outside diameters of the shaft. 3. a). What are the methods of making hollow shafts? Explain any two methods b). A rotating shaft, 50 mm diameter, is made of plain carbon steel 40C8 (Syt=380 N/mm2). It is subjected to a steady torsional moment of 225 n-m and maximum bending moment of 850Nm. Calculate the factor of safety based on a) Maximum principle stress theory b). Maximum shear stress theory 4. a). Under what circumstances the hollow shaft preferred over solid shafts? Explain b). A line shaft transmits 25 KW power at 200rpm by means of a vertical belt drive. The diameter of the belt pulley is 1 m and the pulley over hangs 150mm beyond the centre line of the end bearing. The belt tensions act vertically downwards. The tension on the tight side of the belt is 2.5 times on the slack side. The shaft is made of plain carbon steel 40C8 (Syt=380 N/mm2) and factor of safety is 2.5. The mass of the pulley is 25kgs. Determine the diameter of the shaft. 5. (a) Describe the purpose of gib in cotter joint? What are the applications of cotter joints? (b) Design and draw a cotter joint to support a load varying from 3 kn in compression to 4 kn in tension. The material used is carbon steel for which the following allowable stresses may be used. The load is applied statistically. Tensile stress = compressive stress = 500 N/mm2, shear stress = 350 N/mm2 and crushing stress = 900 N/mm2. 6. (a) Differentiate between torsional rigidity design and lateral rigidity design of shafts. (b) A shaft receives 20 kw power at 240 r.p.m through a 500 mm belt pulley, mounted centrally between two bearings, 600 mm apart and transmits it through a 250 mm gear, overhanging the right bearing by 250 mm. The belt drive is horizontal, and the gear drives, with a downward tangential force. The ratio of belt tension is 2.5. Determine the shaft diameter, assuming permissible normal stress as 80 N/mm2. 7. (a) What is an engineering design? Explain its importance for any system design. (b) Explain the stages in the design of machine members pertaining to manufacturing industry.

10 8. (a) Explain what do you understand by A.M. Wahls factor and state its importance in the design of helical springs. (b) A helical coil spring is to be subjected to loads ranging from 350 to 425 N. The axial compression of the spring over the above load range is approximately 8 mm. Assuming a spring index of approximately 5, determine i. The size of wire ii. The outside diameter of the spring and iii. The number of active coils. Assume necessary data 9. (a) Define stress concentration factor? What are the different methods to reduce the stress concentration factor? (b) A steel connecting rod is subjected to a completely reversed axial load of 10kN. Suggest suitable size of the rod using a factor of safety 2. The Ultimate strength of the material is 11 kn/mm2 and yield strength is 9.3 kn/ mm2. The value of A, factor for correction for type of loading may be taken as 0.85 and size factor as Neglect the column action and the effect of stress concentration 10. (a) Explain the terms i. Caulking ii. Fullering (b) Two plates of 6 mm thick are connected to a triple riveted lap joint of zig-zag pattern. Calculate the rivet diameter, rivet pitch and distance between rows of rivets for the joint. Also state the mode of failure of the joint. The safe working stresses are as follows. _t = 100 N/mm2; _ = 80 N/mm2; _c =150 N/mm (a) State the advantages and drawbacks of cast iron as an engineering material. (b) A cast iron pulley transmits 16 kw at 1440 rpm. The diameter of the pulley is 1.5 m and it has four straight arms of elliptical cross section, in which the major axis is three times the minor axis. Determine the dimensions of the arm, if the allowable bending stress is 20N/mm (a) Derive an expression for the maximum load in a bolt when a bracket with circular base is bolted to a wall by means of 8 bolts. (b) A steam engine cylinder of size 350 _ 350 mm operates at 3 N/mm2 pressure. The cylinder head is connected by means of 12 bolts having yield stress of 450 N/mm2 and the endurance limit of 365 n/mm2 by using gasket, which renders the effect of external load to be half. Determine the size of bolts, if factor of safety is 2.5 and stress concentration factor is 0.5 UNIT VII 1. Design a split muff coupling to transmit 50KW power at 120 rpm. The shafts, key and clamping bolts are made of plain carbon steel 30C8 (Syt=400 N/MM2). The yield strength in compression is 150% of tensile yield strength. The factor of safety for shafts, keys and bolts is 5. The number of clamping bolts is 8. The coefficient of friction between sleeve halves and shaft is 0.3 specify the dimensions of its components.

11 2. Design a rigid type of flange coupling to connect two shafts. The input shaft transmits 37.5KW power at 180 rpm to the output shaft through the coupling. The service factor for the application is 1.5, i.e. the design torque is 1.5 times of rated torque. Select suitable materials for various parts of the coupling and specify the dimensions of its components 3. A rigid flange coupling is used to transmit 15 kw power at 720 rpm between two shafts. The shafts, keys and bolts are made of plain carbon steel 30C8 (Syt=400N/mm2) and the factor of safety is 3. The flanges are made of grey cast iron of grade FG200 (Sut=200N/mm2) and the factor of safety is 6.The keys have square cross section. Design the coupling and specify the dimensions of its parts. 4. Design a muff coupling which is used to connect two steel shafts transmitting 25 kw power at 360 rpm. The shafts and key are made of plain carbon steel 30C8 (Syt=Syc=400 N/mm2). The sleeve is made of grey cast iron FG 200 (Sut=200 N/mm2). The factor of safety for the shafts and key is 4. For sleeve, the factor of safety is 6 based on ultimate strength. 5. (a) What do you understand by the term welded joint? How it differs from riveted joint? (b) Determine the length of the weld run for a plate size 120 mm wide and 15 mm thick to be welded to another plate by means of i. A single transverse weld and ii. Double parallel _llet welds when the joint is subjected to variable loads. 6. (a) Derive an expression for the maximum load in a bolt when a bracket with circular base is bolted to a wall by means of six bolts. (b) A anged bearing for a horizontal shaft is fastened to a frame by means of 6 bolts, equally spaced on 200 mm pitch circle diameter. A 100 kn force acts at a distance of 50 mm from the frame. The diameter of the ange is 270 mm. Determine the size of the bolts, if the tensile stress for the bolt material is 80 N/mm2. 7. Design a clamp coupling for a shaft diameter of 60 mm. The torsional moment to be transmitted by this coupling taking in to account over loading as 160 N-m. The number of bolts used are 6 and the allowable stress in the material of the bolt is limited to 75 N/mm2. The coefficient of friction between the shaft and mu material is 0.25.Draw sectional elevation of the designed clamp coupling 8. (a) What is the difference between a shaft and an axle? How the shafts are classified? (b) Determine the diameter of the hollow shaft having inside diameter 0.5 times the outside diameter. The permissible shear stress is limited to 250 N/mm2. The shaft carries a 800 mm diameter cast iron pulley. This pulley is driven by another pulley mounted on the shaft placed below it. The belt ends are parallel and vertical. The ratio of tensions in the belt is 3. The pulley on the hollow shaft weighs 900 N and overhangs the nearest bearing by 250 mm. The pulley is to transmit 35 kw power at 500 rpm. 9. (a) Write the significance of stresses and stress concentration considerations in manufacturing design. (b) What is meant by preferred numbers and explain their use in engineering design?

12 10. (a) Define the terms, i. equivalent bending moment, and ii. equivalent twisting moment. (b) A hollow shaft of 0.6 m outside diameter and 0.3m inside diameter is used to drive a propeller of a marine vessel. The shaft is mounted on bearings 8 m apart and it transmits 6 MW at 250 rpm. The maximum axial propeller thrust is 600 kn and the shaft weighs 70 kn. Determine: i. The maximum shear stress developed in the shaft and ii. The angular twist between the bearings 11. (a) What is the function of key and what types of stresses are induced in a key? (b) A 75 mm diameter shaft has a key 20 _ 20 mm. The shaft material has yield strength of 350 N/mm2. Assume shear stress as half of the tensile strength and factor of safety as 2. The shaft _ts in to a cast iron hub for which the working stress in compression is 175 N/mm2. Determine the length of the key in the hub to carry the torque of the solid shaft UNIT VIII 1. Design a cantilever leaf spring to absorb 800Nm of energy without exceeding a deflection of 150mm and the permissible stress 875Mpa. The length of the spring is 600mm and the modulus of elasticity is 210GPa.The length of the spring is 600mm and the modulus of elasticity is 210GPa 2. A load narrow gauge car weighing 1,500Kg and moving at a velocity of 1.30 m/sec is brought to rest by a bumper consisting of two helical steel springs of square section in which the mean diameter of the coil is 6 times the side of the square section. In bringing the car to rest the springs are to be compressed 200mm. the value of shear stress is not to exceed 360 MPa. Determine the following a). Maximum load of each spring, b). side of the square section of wire, c). mean diameter of the coils and d. number of active coils. Assume G= 80GPa. 3. A semi-elliptical automobile spring 1.45m long carries a total load of 9kN.The spring is composed of 10 leaves two of which are full length, each 60mm wide. Determine the necessary thickness and the resultant stress to give a deflection of 63mm. E=210GPa. 4. A helical spring made of square steel wire is to absorb 360 Nm of energy while being compressed 150mm. The coils shall have a mean diameter of seven times the side of the square and the maximum induced stress is to be not more than 420MPa. Take G as 84X103Mpa and determine the size for the wire, the mean diameter of the coil and the number of active turns required. Consider the effect of stress concentration. 5. A shaft is supported by two bearings placed 1m apart. A 600 mm diameter pulley is mounted at a distance of 300 mm to the right of left hand bearing and this drives a pulley directly below it with the help of belt having maximum tension of 2.25 kn. Another pulley 400 mm diameter is placed 200 mm to the left of right hand bearing and is driven with the help of electric motor and belt, which is placed horizontally to the right. The angle of contact for both the pulleys is 1800 and = Determine the suitable diameter for a solid shaft, allowing

13 working stress of 63 N/mm2 in tension and 42 N/mm2 in shear for the material of the shaft. Assume that the torque on one pulley is equal to that on the other pulley 6. (a) Differentiate between nominal size and basic size. (b) Explain preferred numbers in engineering design. 7. (a) Write the procedure for designing a lozenge joint. (b) Two lengths of mild steel tie rod having width 300 mm are to be connected by means of Lozenge joint with two cover plates to withstand a tensile load of 200 kn. Completely design the joint, if the permissible stresses are 100 N/mm2 in tension, 70 N/mm2 in shear and 160 N/mm2 in crushing. Draw a neat sketch of the joint. 8. (a) Give the classification of couplings. (b) Design and draw a mu_ coupling to transmit 90 kw power at 108 rpm. The shaft and key are made of the same material having allowable shear stress of 63 N/mm2 and compressive stress of 100 N/mm2. The flange is made of cast iron with allowable shear stress as 35 N/mm2. 9. It is required to connect two co-axial shafts by a split mu_ coupling. The power transmitted is 30 kw at 160 rpm. Assume that there are total of 12 clamping bolts distributed equally on two sides of the mu_ and they can be stressed to a tensile stress of 80 N/mm2. The permissible shearing stress in the shaft and key is 35 N/mm2. Determine the dimensions of the mu_ and diameter of clamping bolts. Assume coefficient of friction between mu_ and shaft is (a) Discuss the influence of various factors in the design of machine members subjected to variable load. (b) A leaf spring an automobile is subjected to cyclic stresses. The average stress is 250 N/mm2, Variable stress is 525 N/mm2, ultimate stress is 590 N/mm2, yield point stress is 450 N/mm2, and endurance limit is 250 N/mm2. Estimate, under what factor of safety the spring is working, by Goodman's and Soderberg formulae. 11. A concentric spring for an air craft engine valve is to exert a maximum force of 8 kn under an axial deflection of 50 mm. Both the springs have same free length, same solid length and are subjected to equal maximum shear stress of 560 N/mm2. If the spring index for both the springs is 5, find (a) The load shared by each spring, (b) The main dimensions of both the springs and (c) The number of active coils of each spring. Assume G = 0.8 _ 105 N/mm2 and diametral clearance to be equal to the difference between the wire diameters. 12. Design a bush pin flexible coupling for connecting a motor shaft to a pump shaft for the service conditions: Power to be transmitted is 70 kw, speed of the motor shaft is 1440 rpm, diameter of the motor shaft is 60 mm, diameter of the pump shaft is 45 mm. The bearing pressure in the rubber bush and allowable stress in the pins are to be limited to 0.5 N/mm2 and 35 N/mm2