PERIYAR CENTENARY POLYTECHNIC COLLEGE PERIYAR NAGAR - VALLAM - 613 403 - THANJAVUR. DEPARTMENT OF MECHANICAL ENGINEERING QUESTION BANK Sub : Design of Machine Elementss Year / Sem: III/ V Sub Code : MEB 540 UNIT-I 1.Define any five mechanical properties metals with atleast one example. 2.Explain how alloy steels are designated with an example. 3.What is free cutting steel? How it is designed? 4. How is plain carbon steel designated according to BIS? 5.Name the type of steel with its composition designated as XXT 72 W 18 Cr 14 V1 6.What are the factors to be considered for the selection of materials for the design of machine elements? 7.Write down any five factors affecting the selection of materials. 8.How is malleable cast iron designated? Explain with an example. 9.Describe different types of cast iron. 10.How are the engineering materials classified? Give two examples of each. 11. Name the type of steele with its composition designed as X15 Cr 16 Ni 12 12.Name the type of steel with its composition, given the designed as 30 cr 20 si 2 Ni 1. 13. Define factor of safety for ductile and brittle materials. 14.Write the procedure for designing machine elements. 15.What is meant by working stress and how is it calculated from the ultimate stress or yield stress of a material? 16.What do you understand by the term Factor of safety in design? List any four important factors that influence the magnitude of factor of safety. 17. Briefly explain the various steps for designing machine elements. 18. What is the different between ultimate stress and working stress? 19 What is an eye bolt? Give its applications. 20. A mild steel rod supports a tensile load of 50 KN. If the stress in the rod is limited to 100 N/mm 2, determine the size of the rod When the cross section is (i) Circular (ii) Square (iii) rectangle with width = 3x thickness. 21.A steel rod of 100mm 2 Cross- sectional area is made up of stands (threads of rope) 1mm in diameter having an allowable tensile stress of 168 N/mm 2 and an ultimate strength of 130 KN. The factor of
safety is 8. If 10 strands are broken along a pitch of the lay of strands, is the rope fit for further use, Why? 22.A knuckle joint is subjected to a pull of 80kn. If the maximum permissible tensile stress in the rods is 100N/mm 2 and the permissible shear in the pin is 80N/mm 2,Calculate the diameter of the rods of the pin. 23. A hydraulic press exerts a total load of 4MN which is carried by two steel rods of 2.5 m long supporting the upper head of the press. It the safe stree is 85 Mpa and E= 210 kn/mm 2, Calculate (i) The diameter of rods. (ii) Extension in each rod. 24.Design a sleeve and cotter joint to withstand a tensile load of 60KN. All parts of the joint are made of the same material and the permissible stresses are given below. f t = 60 N/mm 2 ; f c =125N/mm 2 ; f s = 70N/mm 2 25. A casting weighting 30 KN is lifted by means of an eye bolt of 30mm nominal diameter. The bolt extends 40mm into the casting. Determine direct tensile and shear stresses in the threaded portion of the bolt. 26.A square tie bar 20mm x 20mm in section carries a load. It is attached to a bracket by means of 6 bolts. Calculate the dia of the bolt if the maximum stress in the bar is 150 N/mm 2 and in the bolt is 75 N/mm 2 27. In a steam engine cylinder of 300mm diameter the maximum pressure across the piston 0.65N/mm 2. Determine the diameter of the piston rod, if the maximum tensile or compressive stress on the piston is limited to 40N/mm 2. 28. Two Plates of 16 mm thick are joined by a double riveted lap joint. The rivets are 25mm in diameter. Find the crushing stress induced between the plate and the rivet if the maximum tensile load on the joint is 48 Kn. 29. The crank pin of a high speed stationary engine is subjected to a maximum steam pressure of 35 KN. The allowable bearing pressure is 7N/mm 2. Assuming the bearing length of the pin is 1.2 times the diameter of the pin, determine the dimensions of the pin. 30.A gudgeon pin of uniform circular section is used to connect the piston and the connecting rod of an IC engine. If the maximum pressure on the piston is 1.5 N/mm 2 and the diameter of the piston is 80mm, determine the diameter of the pin against shear failure. Permissible shear stress for the pin material is 30 N/mm 2
31. Calculate the force required to punch a circular blank 60mm diameter in plate 5mm thick. The ultimate shear stress of the plate is 350 N/mm 2. 32. Design a sleeve and cotter joint to withstand a tensile load of 60KN. All parts of the joint are made of the same material and the permissible stresses are given below. f t = 60N/mm 2 ; f c = 125N/mm 2 ; f s = 70N/mm 2 33. A casting weighing 30 KN is lifted by means of an eye bolt of 30mm nominal diameter. The bolt extends 40mm into the casting. Determine direct tensile and shear stresses in the threaded portion of the bolt. UNIT-II 1.What are types of failures in keys? 2.Sketch a woodruff key? Mention its applications. 3.Draw a feather key and give its dimensions in terms of shaft dia d. 5.Classify the different types of couplings. 6. A hollow shaft transmits 600kw at 500rpm. The maximum shear stress is 60N/mm 2.. Find the outside and inside diameter of the shaft, If the outer diameter is twice that of inside diameter. Assume maximum Torque is 20% great that the mean torque. 7.A Pair of wheels of a railway wagon carries a load of 50Kn on each axle box, acting at a distance of 100mm outside the wheel base. The gauge of the rails is 1.4m. Find the diameter of the axle between the wheels, if the permissible stress is 100N/mm 2. 8.A shaft made of mild steel is required to transmit 100kw at 300rpm. The supported length of the shaft is 3m. It carries 2 pulleys each weighing 1500N, supported at a distance of 1m from each ends respectively. Assume the safe value of stress as 60N/mm 2. Determine the diameter of the shaft. 9.A rectangular key 40mm length is required to transmit 10 KW at 900rpm. Determine the size of the key, If the permissible shear stress and crushing stress are limited to 65N/mm 2 respectively, Assume that the shaft and key are made of the same material. 10.Design a protective type flange coupling to connect two shafts to transmit 7.5kw at 720rpm. The permissible shear stress for the shaft, bolts and key materials is 33N/mm 2, Permissible crushing strength for bolt and key material is 60N/mm 2 and permissible shear stress for cast iron is 15N/mm 2. 11.A shaft is transmitting 97.5 KW at 180 Rpm. If the allowable shear stress in the material is 60 Mpa, find the suitable diameter for the shaft. The shaft is not to twist more than 1º in a length of 3m. Take G=80 Gpa. 12. A 15 KW 960 rpm motor has a mild steel shaft of 40mm diameter and the extension being 75mm. The permissible shear and crushing stresses for the mild steel are 56 Mpa and 112 Mpa. Design the key.
13.A shaft 30mm dia is transmitting power at a maximum shear stress of 80Mpa. If a pulley is connected to the shaft by means of key. find the dimension of the key so that the stress in the key is not to exceed 50 Mpa and the length of the key is 4 times the width of the key. 14. A flange coupling has to transmit 110kw at 200rpm. The allowable shear stress of the material is 40MPa and the safe stress may be taken as 30Mpa for the bolts. Assuming the maximum torque to be 15 percent greater than mean, determine the diameter of shaft, dia of the bolt, number of bolt and pitch circle dia of bolt. 15.A line shaft is driven by means of a motor placed vertically below it. The pulley on the line shaft is 1.5m in diameter and has belt tension 5.4Kn and 1.8KN on t he tight side and slack side of the belt respectively. Both these tensions may be assumed to be vertical. If the pulley be overhang from the shaft, the distance of the centre line of the pulley from the centre line of the bearing being 400mm. Find the diameter of the shaft. Assuming maximum allowable shear stress of 42Mpa. 16.A mild steel shaft transmits 20 KW at 200 rpm. It carries a central load of 1000N and is simply supported between the bearing 2 m apart. Determine the size of the shaft, if the allowable shear stress is 42 Mpa and the maximum tensile or compressive stress is not to exceed 56 Mpa. What size of the shaft is required if it is subjected to gradually applied load? UNIT-III 1.Select a flat belt from manufacturer s catalogue to transmit power of 15KW at 1200RPM. The speed of the driven pulley is 450 RPM. Max centre distance between the shaft is 2m. Assume steady load. 2.Select the crossed flat belt drive from the manufacturer s catalogue to transmit a power of 25KW at 960RPM. The speed of the drive pulley is 500RPM. Centre distance between shafts is 1.5m. Apply intermittent load. 3.Design V-belt to the following specification. Power to be transmitted =75Kw Speed of driving wheel =1440 rpm Speed of driven wheel =400 rpm Diameter of driving wheel=300mm Centre distance = 2500 mm Small pulley factor, K d = 1.14
Service factor,=1.3 Correction factor for length, K t = 1.07 4.Design a V-belt drive and calculate the actual tensions from the following data. dia of driven pulley = 600 mm dia of driving pulley = 200 mm Centre distance between pulleys = 1000mm (approximately) Speed of driven pulley=400 Rpm Speed of driving pulley = 1200 Rpm Power transmitted = 10 KW (Don,t convert to w) Service-heavy duty -16 hours/day. 5. A belt drive consists of two V-belts in parallel on grooved pulley of the same size.the angle of groove is 30º.The cross-sectional area of each belt is 750mm 2 and co-efficient of friction is 0.12. The density of belt material is 1.2Mg/m 3 and the maximum stress in the material is 7MN/m 2. Calculate the power that can be transmitted between pulley of 300mm diameter rotating at 1500Rpm. Find also the shaft speed in speed in rpm at which the power transmitted would be maximum. 6.Write short notes on belt materials. 7.Sketch and name the different types of belts used in engineering field. 8.Draw the sketch and note the specifications. A design a fabric belt to transmit 11KW at 420RPM of an engine to a line shaft at 20 RPS. Engine Pulley diameter is 550mm and the centre distance is 2m. Assume co-efficient of friction µ = 0.2 and number of plies =6. 9. Leather belt drive transmits 15KW power. The centre distance between the pulleys is twice the diameter of the big pulley. The speeds of big and small pulleys are 480 rpm and 1440rpm respectively. The belt should operate at a velocity of 20m/sec approximately and the stresses in the belt should not exceed 2.25 N/mm 2. The density of leather is 0.95 gm/cc and the co-efficient of friction is 0.35. The thickness of the belt is 5mm. Calculate i) The diameters of pulleys ii) The length and width of belt iii) The belt tensions. 10.A leather belt 9mm thick transmits 26KW from a pulley one metre diameter running at 300rpm. The friction co-efficient between belt and pulley surface is 0.28 and the belt material weighs 9.3 x10 3 N/m 3. The angle of lap is 165º. If the stress in the belt is limited to 3N/mm 2. Determine the width of belt. 11. A power of 60ke at 750 rpm is to transmitted from an electric motor to a Compressor shaft at 300rpm by V belt. The approximate larger pulley diameter is 1500 mm. The approximate centre distance is 1650 mm. Cross sectional area is 350 mm 2 and density is 1000 kg/m 3, having an allowable tensile stress of 2 Mpa is allowable for use. Overload factor is 1.5. a=34º, µ = 0.28.
12.Design a V-belt and calculate the actual belt tensions and average stress from the following data. dia driven pulley = 500 mm dia of driven puley = 150 mm Centre distance between pulleys = 925 mm Speed of driven pulleys =300rpm Speed of driving pulleys = 1000 rpm Power transmitted = 7.5 KW Service factor, K s = 1.3 Co-efficient of friction, µ= 0.3 13. Sketch open belt drive and crossed belt drive. Write the formula for length of belt in open belt and crossed belt drives. 14.Sketch the cross- section of a V-belt and label its important parts. 15. How are the V-belts designated? 16.Design a flat belt drive to transmit 22.5 KW at 740 RPM to an aluminium rolling machine.. The speed ratio is 3. The distance between pulleys is 3m. Diameter pulley is 1.2m. Use manufacture s data. 17. Load correction factor, K s = 1.5 18. Design a fabric belt to transmit 11KW at 420RPM of an engine to a line shaft at 20 RPS. Engine pulley diameter is 550mm and the centre distance is 2m. Assume co-efficient of friction µ= 0.2 and number of plies =6. 19. A leather belt 9mm thick transmits 26KW from a pulley one metre diameter running at 300rpm. The friction co-efficient between belt and pulley surface is 0.28 and the belt material weighs 9.3 10 3 N/m 3. The angle of lap is 165º..If the stress in the belt is limited to 3N/mm 2. Determine the width of belt. UNIT-IV 1.Design a journal bearing for a centrifugal pump from the following:- Load on the journal =20KN. Speed of journal =900 rpm. Diameter of journal =100mm. L/D=1.6. Type of oil used is SAE 10 for which the absolute viscosity at 55ºC=17 CP. Ambient temp 15.5ºC.Maximum bearing pressure=1.5n/mm 2. Heat dizzipation co-efficient =1332 J/S/m 2 /ºC. Calculate the mass of lubricatinf oil required for artificial cooling, if rise in temp of oil is limited to 10ºC. ATake specific head of oil as 1710 J/kg k. 2.A journal bearing 300mm long and 150mm dia carries a radial load of 9KN at 1200 rpm. The power lost in friction is 6KW. Viscosity of oil at room temperature is 0.018 Pa s. Find the diametral clearance, 3.A journal bearing 75mm long supports a load of 7500N on a 50mm diameter journal running at 750rpm. The diametral clearance is 0.0693mm. determine the viscosity of oil if the operation temp. of the bearing surface is limited to 77ºC. The ambient temp=21ºc. Heat dissipating co-effcient =210W/m 2 / ºC.
4. An 80mm long journal bearing supports a load of 2800N on a 50mm diameter shaft. The bearing clearance of 0.05mm and the viscosity of the oil is 0.021 kg/m-s at the operating temperature. If the bearing is capable of dissipating 80J/s, determine the maximum safe speed. 5.State and explain the different properties of materials used for sliding contact bearings. 6. A journal bearing is proposed for a centrifugal pump. The diameter of the journal is 150mm and the load on it is 40KN and its speed is 900 rpm. Design and given the complete calculations for the bearing. 7.Design a suitable journal bearing a centrifugal pump form the following data: Load on the bearing = 13.25 KN Dia of the journal = 80 mm Speed = 1440 rpm Bearing characteristic number = 30x10-6 Permissible bearing pressure = 0.7 to 1.4 N/mm 2 Average atmospheric temp = 30º C Calculate the cooling requirements using lasche s equation. Use Mckee s equation for calculating the friction co-efficient. Assume L/D=2. Average temp. of oil, t º = 75º C.Co-efficient of head dissipation, K = 0.2730C/m 2 /w for heavily Constructed bearing. Temperature rise, t º =6º C 8.The load on a 100mm fully hydro dynamic bearing is 900nN. Speed of journal is 320rpm. Take l/d=1,c/d=0.0011. Temperature is 65º C. Minimum oil film thickness =0.022 (i) Select an oil that will closely accord with the stated conditions. For the selected oil, determine (ii) Power lost in friction (iii) Oil flow through the bearing (iv) Amount of leakage (v) temperature rise of oil when it passes through the bearing and (vi) maximum Oil pressure. 9. Define bearing. How are bearings Classified? 10.Mwention the types of bearing and their applications. 11.Define a journal bearing. State the factors to be considered in the selection of bearing type. 12.Define radial clearance and diametral clearance ratio. 13.Explain the following terms:- (i) Diametral clearance (ii) Minimum film thickness 14.What are the commonly used materials for sliding contact bearings? Explain any three important physical characteristics of good bearing material. 15.What are the advantages of Ball and Roller bearings over journal bearings? 16.Why are rolling contact bearings called anti-friction bearings? 17.Write short notes on thrust ball bearing. 18.Where are the angular contact and self aligning ball bearings used? Draw neat sketches of these bearings. 19.What are the standard dimensions and designations of ball bearings? 20.Write short notes on needle and tapered bearings of ball bearings? 21.Explain self aligning ball bearing with a neat sketch. 22.Explain self aligning ball bearing with neat sketch. 23.Write short notes on (i) Single row bearing (ii) Double row bearing (iii) Spherical bearing (iv) Needle bearing (v) Taper bearing. 24. Describe radial and thrust ball bearing. 25. What are the materials used for balls and rollers? 26.Write short notes on needle bearing with a sketch 27.Sketch (i) needle bearing (ii) Taper bearing
28.Explain how a ball bearing is designated with an example. 29. A 150mm diameter shaft supporting a load of 10KN has a speed of 1500RPM. The shaft runs in a bearing whose length is 1.5 times the shaft diameter. If the diametral clearance of the bearing is 0.15mm and the absolute viscosity of the oil at the operating temperature is 0.011kg/m-s. find the power wasted in friction. 30.A load on the journal bearing is 150KN due to turbine shaft at 300mm diameter running at 1800RPM. Determine the following:- i)length of the bearing if the allowable bearing pressure is 1.6 N/mm 2. ii) Amount of head to be removed by the lubricant/min of the bearing, if temperature of bearing is 60ºC and viscosity of oil is 0.02 kg/ms and t he bearing clearance is 0.25mm. UNIT-V 1.A hand lever is mounted on a shaft. The maximum force of 150N is applied by the worker. The distance between the centre of the shaft to the point of load is 1m. Determine the diameter of the solid shaft, If the permissible shear stress is limited to 20N/mm 2. Determine the section of the lever near the boss, if the permissible stress is limited to 85N/mm 2. Assume rectangular cross-section with sides in the ratio 1:2 2.Design a hand lever of rectangular section subjected to a maximum load of 250N at the end of moment arms of 1.2m. The thickness of the lever is constant and is equal to 0.375 times the width of lever near the boss., Permissible shear stress for the shaft material is 40N/mm 2 and the permissible bending stress for the lever material is 80N/mm 2 3. A foot lever is 1000mm from centre of shaft to point of applications of load of 900N. Calculate the diameter of the shaft, if the permissible shear stress for the shaft material is 75N/mm 2. Determine the dimension of the key if the safe shear stress for the key material is 80N/mm 2. Find the diamension of rectangular arm of the foot lever at 100mm from the centre of the shaft. Assume width of the lever near the boss as 3 times the thickness.allowable bending stress is 70N/mm 2. 4.A pinion runs at 600 rpm drives a gear at a speed ratio of 4:1. Allowable static stress of point and gear material is 85N/mm 2. Pinion has 16 teeth of module 8mm. Teeth are 20º F.D system. Face width 90mm. Find the power transmitted 5.A cranked lever has the following dimension. Length of the handle = 400mm, Length of the lever arm= 500mm, Overhang of the Journal=200mm. If the lever is operated by a single person exerting a maximum forces of 500N at a distance of 1/3 rd length of the handle from its free end. Find (i)diameter of the handle (ii) Cross section of the lever arm which is rectangular b= 2t. (iii) diameter of the journal. The permissible bending stress for the lever material may taken as 50Mpa and shear stress for the shaft material may taken as 50MPa and shear stress for the shaft material is 42MPa. 6.Design a cranked lever having a length of handle as 0.5m,length of lever arm as 0.45m and overhang of the journal as 0.1m. The lever is used for operating hoisting which and is operated by two persons exerting a maximum force of 500N at a distance of 0.4 times the length of the handle from free end. The bending stress in lever should not exceed 50N/mm 2 and shear stress in lever should not exceed 50N/mm 2. Shear stress in the should not exceed 40N/mm 2.
7.It is desired to transmit 10KW from a motor shaft running at 1440 rpm to alow speed reduction of 3:1. The teeth are 14 1/2º involute with 25 teeth on the pinion. The starting torque is 30% higher than the running torque. Both the pinion and gear are made of steel heat treated. Design a suitable spur gear drive to satisfy the above condition y=0.0124-0.684/tp for 141/2º involve gear. Assume module=6. Allowable static stress, f º =210MPa. 8.Explain the different types of lever with sketches. 9. State the different types of lever, and their application in engineering practice. 10. Explain the first, second and third type of lever. 11. Discuss the design procedure of hand lever. 12. Explain t he design procedure of foot lever. 13. Discuss the design procedure of cranked lever. 14. Mention four important types of gears, the materials used and any two of their applications. 15.lllustrate any five terms used in spur gear terminology. 16.What are the materials used for gears? 17.What are speed reducers? Give the applications of speed reducers. 18.Write short notes on speed reducer. 19.What are the components of speed reducer. 20. A gear drive is required to transmit a maximum power of 25 KW. The velocity ratio is 1:2 and rpm of the pinion is 200. The approximate centre distance between the shafts may be taken as 600mm. The teeth has 20º stub in volute profiles. The material used for the gear is C.I. Find the module, face width and number of teeth on each gear. Check your design for dynamic and wear loads. Assume the following: 1) medium shock load and 8-10 hrs/day service. 2) face width, b =3 x circular pitch 3) Velocity factor, C V = 3/3+V Where V-Pitch line velocity (m/sec) 4) Deformation factor, C=260KN/m 5) Fatigue stress factor, K= 1.42 N/mm 2 *******