WordPress.com
Unit –I - INTRODUCTION OF DESIGNDefine: "Design"What is 'Adaptive design '? Where is it used? Give examples.What are the various phase of design process?List some factors that influence machine design.Define: "Optimization"Define Principal plane, principal stressGive examples for curved beamsWhy normal stress theory is not suitable for ductile materials?Define stress concentration and stress concentration factor. ,10 Define: "Factor of safety"How is factor of safety defined for brittle and ductile materials?What are the various factors to be considered in deciding the factor of safety?What are the factors to be considered in the selection of materials for a machine element?Differentiate between static and variable stresses.Define amplitude stress and stress ratio. What is the value of stress ratio for a cyclic stress?What are various theories of failure?What is the use of Goodman &Soderberg diagrams? Differentiate between Endurance limit and Endurance strength.Define endurance limit. What are the factors affecting endurance strength.How do you classify materials for engineering use?What are the factors to be considered for the selection of materials for the design of machine elements?Discuss.Enumerate the most commonly used engineering materials and state at least one important propertyand one application of each.Why are metals in their pure form unsuitable for industrial use?Define ‘mechanical property’ of an engineering material. State any six mechanical properties, givetheir definitions and one example of the material possessing the properties.Define the following properties of a material :Ductility, (ii) Toughness, (iii) Hardness, and (iv) Creep.Distinguish clearly amongst cast iron, wrought iron and steel regarding their constituents and properties.UNIT – II - Design of JointsWhat is a cotter joint? Explain with the help of a neat sketch, how a cotter joint is made ?What are the applications of a cotteredjoint ?Discuss the design procedure of spigot and socket cotter joint.Why gibs are used in a cotter joint? Explain with the help of a neat sketch the use of single and doublegib.Describe the design procedure of a gib and cotter joint.Distinguish between cotter joint and knuckle joint.Sketch two views of a knuckle joint and write the equations showing the strength of joint for the mostprobable modes of failure.Explain the purpose of a turn buckle. Describe its design procedure.Design a cotter joint to connect two mild steel rods for a pull of 30 kN. The maximum permissiblestresses are 55 MPa in tension ; 40 MPa in shear and 70 MPa in crushing. Draw a neat sketch of thejoint designed.Two rod ends of a pump are joined by means of a cotter and spigot and socket at the ends. Design thejoint for an axial load of 100 kN which alternately changes from tensile to compressive. The allowablestresses for the material used are 50 MPa in tension, 40 MPa in shear and 100 MPa in crushing.Two mild steel rods 40 mm diameter are to be connected by a cotter joint. The thickness of the cotteris 12 mm. Calculate the dimensions of the joint, if the maximum permissible stresses are: 46 MPa intension ; 35 MPa in shear and 70 MPa in crushing.The big end of a connecting rod is subjected to a load of 40 kN. The diameter of the circular partadjacent to the strap is 50 mm. Design the joint assuming the permissible tensile stress in the strap as 30 MPa and permissible shearstress in the cotter and gib as 20 MPa.Design a cotter joint to connect a piston rod to the crosshead. The maximum steam pressure on thepiston rod is 35 kN. Assuming that all the parts are made of the same material having the followingpermissible stresses :σ1 = 50 MPa ; τ = 60 MPa and σc= 90 MPa.Design and draw a cotter foundation bolt to take a load of 90 kN. Assume the permissible stresses asfollows :σt= 50 MPa, τ = 60 MPa and σc= 100 MPa.Design a knuckle joint to connect two mild steel bars under a tensile load of 25 kN. The allowablestresses are 65 MPa in tension, 50 MPa in shear and 83 MPa in crushing.A knuckle joint is required to withstand a tensile load of 25 kN. Design the joint if the permissiblestresses are :σt= 56 MPa ; τ = 40 MPa and σc= 70 MPa.The pull in the tie rod of a roof truss is 44 kN. Design a suitable adjustable screw joint. The permissibletensile and shear stresses are 75 MPa and 37.5 MPa respectively. Draw full size two suitable views ofthe joint.What do you understand by the term welded joint? How it differs from riveted joint?Sketch and discuss the various types of welded joints used in pressure vessels. What are the considerationsinvolved?State the basic difference between manual welding, semi-automatic welding and automatic welding.What are the assumptions made in the design of welded joint?Explain joint preparation with particular reference to butt welding of plates by arc welding.Discuss the standard location of elements of a welding symbol.Explain the procedure for designing an axially loaded unsymmetrical welded section.What is an eccentric loaded welded joint ? Discuss the procedure for designing such a joint.A plate 100 mm wide and 10 mm thick is to be welded with another plate by means of transverse weldsat the ends. If the plates are subjected to a load of 70 kN, find the size of weld for static as well as fatigueload. The permissible tensile stress should not exceed 70 MPa. If the plates in Ex. 1, are joined by double parallel fillets and the shear stress is not to exceed 56 MPa,find the length of weld for (a) Static loading, and (b) Dynamic loading. A 125 × 95 × 10 mm angle is joined to a frame by two parallel fillet welds along the edges of 150 mmleg. The angle is subjected to a tensile load of 180 kN. Find the lengths of weld if the permissible staticload per mm weld length is 430 N. A circular steel bar 50 mm diameter and 200 mm long is welded perpendicularly to a steel plate toform a cantilever to be loaded with 5 kN at the free end. Determine the size of the weld, assuming theallowable stress in the weld as 100 MPa.A 65 mm diameter solid shaft is to be welded to a flat plate by a fillet weld around the circumferenceof the shaft. Determine the size of the weld if the torque on the shaft is 3 kN-m. The allowable shearstress in the weld is 70 MPa.A solid rectangular shaft of cross-section 80 mm × 50 mm is welded by a 5 mm fillet weld on all sidesto a flat plate with axis perpendicular to the plate surface. Find the maximum torque that can beapplied to the shaft, if the shear stress in the weld is not to exceed 85 MPa.A low carbon steel plate of 0.7 m width welded to a structure of similar material by means of twoparallel fillet welds of 0.112 m length (each) is subjected to an eccentric load of 4000 N, the line ofaction of which has a distance of 1.5 m from the centre of gravity of the weld group. Design therequired thickness of the plate when the allowable stress of the weld metal is 60 MPa and that of the plate is 40 MPa.A 125 × 95 × 10 mm angle is welded to a frame by two 10 mm fillet welds, as shown in Fig. 10.35.A load of 16 kN is apsplied normal to the gravity axis at a distance of 300 mm from the centre ofgravity of welds. Find maximum shear stress in the welds, assuming each weld to be 100 mm long andparallel to the axis of the angle.UNIT –III - Power screw and Leaf spring Discuss the various types of power threads. Give at least two practical applications for each type.Discuss their relative advantages and disadvantages.Why are square threads preferable to V-threads for power transmission?How does the helix angle influence onthe efficiency of square threaded screw?What do you understand by overhaulingof screw?What is self locking property of threadsand where it is necessary?Show that the efficiency of self lockingscrews is less than 50 percent.In the design of power screws, on whatfactors does the thread bearing pressuredepend? Explain.Why is a separate nut preferable to anintegral nut with the body of a screw jack?Differentiate between differential screwand compound screw.What is the function of a spring? In which type of spring the behaviour is non-linear?Classify springs according to their shapes. Draw neat sketches indicating in each case whether stressesare induced by bending or by torsion.Discuss the materials and practical applications for the various types of springs.The extension springs are in considerably less use than the compression springs. Why?Explain the following terms of the spring :Free length; (ii) Solid height;Spring rate; (iv) Active and inactive coils;(v) Spring index; and (vi) Stress factor.Explain what you understand by A.M. Wahl’s factor and state its importance in the design of helicalsprings?Explain one method of avoiding the tendency of a compression spring to buckle.A compression spring of spring constant K is cut into two springs having equal number of turns andthe two springs are then used in parallel. What is the resulting spring constant of the combination?How does the load carrying capacity of the resulting combination compare with that of the originalspring?Prove that in a spring, using two concentric coil springs made of same material, having same lengthand compressed equally by an axial load, the loads shared by the two springs are directly proportionalto the square of the diameters of the wires of the two springs.What do you understand by full length and graduated leaves of a leaf spring? Write the expression fordetermining the stress and deflection in full length and graduated leaves.What is nipping in a leaf spring? Discuss its role. List the materials commonlyIn a hand vice, the screw has double start square threads of 24 mm outside diameter. If the lever is 200mm long and the maximum force that can be applied at the end of lever is 250 N, find the force withwhich the job is held in the jaws of the vice. Assume a coefficient of friction of 0.12. A square threaded bolt of mean diameter 24 mm and pitch 5 mm is tightened by screwing a nut whosemean diameter of bearing surface is 50 mm. If the coefficient of friction for the nut and bolt is 0.1 andfor the nut and bearing surfaces 0.16, find the force required at the end of a spanner 0.5 m long when the load on the bolt is 10 kN.The spindle of a screw jack has a singlestart square thread with an outsidediameter of 45 mm and a pitch of 10mm. The spindle moves in a fixed nut.The load is carried on a swivel headbut is not free to rotate. The bearingsurface of the swivel head has a meandiameter of 60 mm. The coefficient offriction between the nut and screw is0.12 and that between the swivel headand the spindle is 0.10. Calculate theload which can be raised by efforts of100 N each applied at the end of twolevers each of effective length of 350mm. Also determine the efficiency ofthe lifting arrangement.The cross bar of a planner weighing 12 kN is raised and lowered by means of two square threadedscrews of 38 mm outside diameter and 7 mm pitch. The screw is made of steel and a bronze nut of38 mm thick. A steel collar has 75 mm outside diameter and 38 mm inside diameter. The coefficient offriction at the threads is assumed as 0.11 and at the collar 0.13. Find the force required at a radius of100 mm to raise and lower the load. The lead screw of a lathe has square threads of 24 mm outside diameter and 5 mm pitch. In order todrive the tool carriage, the screw exerts an axial pressure of 2.5 kN. Find the efficiency of the screwand the power required to drive the screw, if it is to rotate at 30 r.p.m. Neglect bearing friction.Assume coefficient of friction of screw threads as 0.12. The lead screw of a lathe has Acme threads of 60 mm outside diameter and 8 mm pitch. It suppliesdrive to a tool carriage which needs an axial force of 2000 N. A collar bearing with inner and outerradius as 30 mm and 60 mm respectively is provided. The coefficient of friction for the screw threadsis 0.12 and for the collar it is 0.10. Find the torque required to drive the screw and the efficiency of thescrewA cross bar of a planer weighing 9 kN is raised and lowered by means of two square threaded screwsof 40 mm outside diameter and 6 mm pitch. The screw is made of steel and nut of phosphor bronzehaving 42 mm height. A steel collar bearing with 30 mm mean radius takes the axial thrust. Thecoefficient of friction at the threads and at the collar may be assumed as 0.14 and 0.10 respectively.Find the force required at a radius of 120 mm of a handwheel to raise and lower the load. Find also theshear stress in the nut material and the bearing pressure on the threads.A machine slide weighing 3000 N is elevated by a double start acme threaded screw at the rate of840 mm/min. If the coefficient of friction be 0.12, calculate the power to drive the slide. The end ofthe screw is carried on a thrust collar of 32 mm inside diameter and 58 mm outside diameter. The pitchof the screw thread is 6 mm and outside diameter of the screw is 40 mm. If the screw is of steel, is itstrong enough to sustain the load? Draw a neat sketch of the system. A sluice valve, used in water pipe lines, consists of a gate raised by the spindle, which is rotated by thehand wheel. The spindle has single start square threads. The nominal diameter of the spindle is 36 mmand the pitch is 6 mm. The friction collar has inner and outer diameters of 32 mm and 50 mm respectively.The coefficient of friction at the threads and the collar are 0.12 and 0.18 respectively. The weight ofthe gate is 7.5 kN and the frictional resistance to open the valve due to water pressure is 2.75 kN.Using uniform wear theory, determine : 1. torque required to raise the gate; and 2. overall efficiency.Design a screw jack for lifting a load of 50 kN through a height of 0.4 m. The screw is made of steeland nut of bronze. Sketch the front sectional view. The following allowable stresses may be assumedFor steel : Compressive stress = 80 MPa ; Shear stress = 45 MPaFor bronze : Tensile stress = 40 MPa ; Bearing stress = 15 MPaShear stress = 25 MPa.The coefficient of friction between the steel and bronze pair is 0.12. The dimensions of the swivelbase may be assumed proportionately. The screw should have square threads. Design the screw, nutand handle. The handle is made of steel having bending stress 150 MPa (allowable).A screw jack carries a load of 22 kN. Assuming the coefficient of friction between screw and nut as0.15, design the screw and nut. Neglect collar friction and column action. The permissible compressiveand shear stresses in the screw should not exceed 42 MPa and 28 MPa respectively. The shear stressin the nut should not exceed 21 MPa. The bearing pressure on the nut is 14 N/mm2. Also determinethe effort required at the handle of 200 mm length in order to raise and lower the load. What will bethe efficiency of screw? Design and draw a screw jack for lifting a safe load of 150 kN through a maximum lift of 350 mm.The elastic strength of the material of the screw may be taken as 240 MPa in compression and 160MPa in shear. The nut is to be made of phosphor bronze for which the elastic strengths in tension,compression and shear are respectively 130, 115 and 100 MPa. Bearing pressure between the threadsof the screw and the nut may be taken as 18 N/mm2. Safe crushing stress for the material of the bodyis 100 MPa. Coefficient of friction for the screw as well as collar may be taken as 0.15.Design a toggle jack to lift a load of 5 kN. The jack is to be so designed that the distance between thecentre lines of nuts varies from 50 to 220 mm. The eight links are symmetrical and 120 mm long. Thelink pins in the base are set 30 mm apart. The links, screw and pins are made from mild steel for whichthe stresses are 90 MPa in tension and 50 MPa in shear. The bearing pressure on the pin is 20 N/mm2.Assume the coefficient of friction between screw and nut as 0.15 and pitch of the square threadedscrew as 6 mm.Design a compression helical spring to carry a load of 500 N with a deflection of 25 mm. The springindex may be taken as 8. Assume the following values for the spring material:Permissible shear stress = 350 MPaModulus of rigidity = 84 kN/mm2whereC = spring index.A helical valve spring is to be designed for an operating load range of approximately 90 to 135 N. Thedeflection of the spring for the load range is 7.5 mm. Assume a spring index of 10. Permissible shearstress for the material of the spring = 480 MPa and its modulus of rigidity = 80 kN/mm2. Design thespring.Design a helical spring for a spring loaded safety valve for the following conditions :Operating pressure = 1 N/mm2Maximum pressure when the valve blows off freely= 1.075 N/mm2Maximum lift of the valve when the pressure is 1.075 N/mm2= 6 mmDiameter of valve seat = 100 mmMaximum shear stress = 400 MPaModulus of rigidity = 86 kN/mm2Spring index = 5.5 A vertical spring loaded valve is required for a compressed air receiver. The valve is to start openingat a pressure of 1 N/mm2 gauge and must be fully open with a lift of 4 mm at a pressure of 1.2 N/mm2gauge. The diameter of the port is 25 mm. Assume the allowable shear stress in steel as 480 MPa andshear modulus as 80 kN/mm2.Design a suitable close coiled round section helical spring having squared ground ends. Also specifyinitial compression and free length of the spring.A railway wagon weighing 50 kN and moving with a speed of 8 km per hour has to be stopped by fourbuffer springs in which the maximum compression allowed is 220 mm. Find the number of turns ineach spring of mean diameter 150 mm. The diameter of spring wire is 25 mm. Take G = 84 kN/mm2.The bumper springs of a railway carriage are to be made of square section wire. The ratio of meandiameter of spring to the side of wire is nearly equal to 6. Two such springs are required to bring to resta carriage weighing 20 kN moving with a velocity of 1.5 m/s with a maximum deflection of 200 mm.A load of 2 kN is dropped axially on a close coiled helical spring, from a height of 250 mm. The springhas 20 effective turns, and it is made of 25 mm diameter wire. The spring index is 8. Find the maximumshear stress induced in the spring and the amount of compression produced. The modulus of rigidityfor the material of the spring wire is 84 kN/mm2.A helical compression spring made of oil tempered carbon steel, is subjected to a load which variesfrom 600 N to 1600 N. The spring index is 6 and the design factor of safety is 1.43. If the yield shearstress is 700 MPa and the endurance stress is 350 MPa, find the size of the spring wire and meandiameter of the spring coil.A carriage spring 800 mm long is required to carry a proof load of 5000 N at the centre. The spring ismade of plates 80 mm wide and 7.5 mm thick. If the maximum permissible stress for the material ofthe plates is not to exceed 190 MPa, determine :The number of plates required, 2. The deflection of the spring, and 3. The radius to which the platesmust be initially bent.The modulus of elasticity may be taken as 205 kN/mm2.A semi-elliptical laminated spring 900 mm long and 55 mm wide is held together at the centre by aband 50 mm wide. If the thickness of each leaf is 5 mm, find the number of leaves required to carry aload of 4500 N. Assume a maximum working stress of 490 MPa.If the two of these leaves extend the full length of the spring, find the deflection of the spring. TheYoung’s modulus for the spring material may be taken as 210 kN/mm2.A semi-elliptical laminated spring is made of 50 mm wide and 3 mm thick plates. The length betweenthe supports is 650 mm and the width of the band is 60 mm. The spring has two full length leaves andfive graduated leaves. If the spring carries a central load of 1600 N, find :Maximum stress in full length and graduated leaves for an initial condition of no stress in the leaves. The maximum stress if the initial stressUNIT –IV -Brakes and clutchesHow does the function of a brake differ from that of a clutch ?A weight is brought to rest by applying brakes to the hoisting drum driven by an electric motor. Howwill you estimate the total energy absorbed by the brake ?What are the thermal considerations in brake design ?What is the significance of pVvalue in brake design ?What are the materials used for brake linings.Discuss the different types of brakes giving atleast one practical application for each.List the important factors upon which the capacity of a brake depends.What is a self-energizing brake ? When a brake becomes self-locking.A single block brake, as shown in Fig. 25.39, has a drum diameter of 720 mm. If the brake sustains225 N-m torque at 500 r.p.m.; find :the required force (P) to apply the brake for clockwise rotation of the drum;the required force (P) to apply the brake for counter clockwise rotation of the drum;the location of the fulcrum to make the brake self-locking for clockwise rotation of the drum; andThe coefficient of friction may be taken as 0.3. The layout and dimensions of a double shoe brake is shown in Fig. 25.40. The diameter of the brakedrum is 300 mm and the contact angle for each shoe is 90°. If the coefficient of friction for the brakelining and the drum is 0.4, find the spring force necessary to transmit a torque of 30 N-m. Alsodetermine the width of the brake shoes, if the bearing pressure on the lining material is not to exceed0.28 N/mm2.The drum of a simple band brake is 450 mm. The band embraces 3/4th of the circumference of thedrum. One end of the band is attached to the fulcrum pin and the other end is attached to a pin B asshown in Fig. 25.41. The band is to be lined with asbestos fabric having a coefficient of friction 0.3.The allowable bearing pressure for the brake lining is 0.21 N/mm2. Design the band shaft, key, leverand fulcrum pin. The material of these parts is mild steel having permissible stresses as follows :σt= σc= 70 MPa, and τ = 56 MPaA band brake as shown in Fig. 25.42, is required to balance a torque of 980 N-m at the drum shaft. Thedrum is to be made of 400 mm diameter and is keyed to the shaft. The band is to be lined with ferodolining having a coefficient of friction 0.25. The maximum pressure between the lining and drum is0.5 N/mm2. Design the steel band, shaft, key on the shaft, brake lever and fulcrum pin. The permissiblestresses for the steel to be used for the shaft, key, band lever and pin are 70 MPa in tension andcompression and 56 MPa in shear.In a band and block brake, the band is lined with 14 blocks, each of which subtends an angle of 20° at thedrum centre. One end of the band is attached to the fulcrum of the brake lever and the other to a pin150 mm from the fulcrum. Find the force required at the end of the lever 1 metre long from the fulcrumto give a torque of 4 kN-m. The diameter of the brake drum is 1 metre and the coefficient of frictionbetween the blocks and the drum is 0.25.A single plate clutch with both sides of the plate effective is required to transmit 25 kW at 1600 r.p.m.The outer diameter of the plate is limited to 300 mm and the intensity of pressure between the platesnot to exceed 0.07 N/mm2. Assuming uniform wear and coefficient of friction 0.3, find the innerdiameter of the plates and the axial force necessary to engage the clutch.Give a complete design analysis of a single plate clutch, with both sides effective, of a vehicle totransmit 22 kW at a speed of 2800 r.p.m. allowing for 25% overload. The pressure intensity is not toexceed 0.08 N/mm2 and the surface speed at the mean radius is not to exceed 2000 m/min. Takecoefficient of friction for the surfaces as 0.35 and the outside diameter of the surfaces is to be 1.5 timesthe inside diameter. The axial thrust is to be provided by 6 springs of about 24 mm coil diameter. Forspring material, the safe shear stress is to be limited to 420 MPa and the modulus of rigidity may betaken as 80 kN/mm2.A multiple disc clutch has three discs on the driving shaft and two on the driven shaft, providing fourpairs of contact surfaces. The outer diameter of the contact surfaces is 250 mm and the inner diameteris 150 mm. Determine the maximum axial intensity of pressure between the discs for transmitting18.75 kW at 500 r.p.m. Assume uniform wear and coefficient of friction as 0.3.A multiple disc clutch employs 3 steel and 2 bronze discs having outer diameter 300 mm and innerdiameter 200 mm. For a coefficient of friction of 0.22, find the axial pressure and the power transmittedat 750 r.p.m., if the normal unit pressure is 0.13 N/mm2.Also find the axial pressure of the unit normal pressure, if this clutch transmits 22 kW at1500 r.p.m. A multiple disc clutch has radial width of the friction material as 1/5th of the maximum radius. Thecoefficient of friction is 0.25. Find the total number of discs required to transmit 60 kW at 3000 r.p.m.The maximum diameter of the clutch is 250 mm and the axial force is limited to 600 N. Also find themean unit pressure on each contact surface. An engine developing 22 kW at 1000 r.p.m. is fitted with a cone clutch having mean diameter of 300mm. The cone has a face angle of 12°. If the normal pressure on the clutch face is not to exceed 0.07N/mm2 and the coefficient of friction is 0.2, determine :the face width of the clutch, andthe axial spring force necessary to engage the clutch.A cone clutch is to be designed to transmit 7.5 kW at 900 r.p.m. The cone has a face angle of 12°. Thewidth of the face is half of the mean radius and the normal pressure between the contact faces is not toexceed 0.09 N/mm2. Assuming uniform wear and the coefficient of friction between the contact facesas 0.2, find the main dimensions of the clutch and the axial force required to engage the clutch.A soft cone clutch has a cone pitch angle of 10°, mean diameter of 300 mm and a face width of 100mm. If the coefficient of friction is 0.2 and has an average pressure of 0.07 N/mm2 for a speed of 500r.p.m., find : (a) the force required to engage the clutch; and (b) the power that can be transmitted.Assume uniform wear.A soft surface cone clutch transmits a torque of 200 N-m at 1250 r.p.m. The larger diameter of theclutch is 350 mm. The cone pitch angle is 7.5° and the face width is 65 mm. If the coefficient offriction is 0.2, find :the axial force required to transmit the torque;the axial force required to engage the clutch;the average normal pressure on the contact surfaces when the maximum torque is being transmitted;and4.the maximum normal pressure assuming uniform wear.UNIT –V- Pressure VesselWhat is the pressure vessel ?Make out a systematic classification of pressure vessels and discuss the role of statutory regulations.How do you distinguish between a thick and thin cylinder?What are the important points to be considered while designing a pressure vessel ?Distinguish between circumferential stress and longitudinal stress in a cylindrical shell, when subjectedto an internal pressure.Show that in case of a thin cylindrical shell subjected to an internal fluid pressure, the tendency toburst lengthwise is twice as great as at a transverse section.When a thin cylinder is subjected to an internal pressure p, the tangential stress should be the criterionfor determining the cylinder wall thickness. Explain.Derive a formula for the thickness of a thin spherical tank subjected to an internal fluid pare the stress distribution in a thin and thick walled pressure vessels.When the wall thickness of a pressure vessel is relatively large, the usual assumptions valid in thincylinders do not hold good for its analysis. Enumerate the important violations. List any two theoriessuggested for the analysis of thick cylinders.Discuss the design procedure for pressure vessels subjected to higher external pressure.Explain the various types of ends used for pressure vessel giving practical applications of each.A steel cylinder of 1 metre diameter is carrying a fluid under a pressure of 10 N/mm2. Calculate thenecessary wall thickness, if the tensile stress is not to exceed 100 MPa. A steam boiler, 1.2 metre in diameter, generates steam at a gauge pressure of 0.7 N/mm2. Assumingthe efficiency of the riveted joints as 75% , find the thickness of the shell. Given that ultimate tensilestress = 385 MPa and factor of safety = 5. Find the thickness of a cast iron cylinder 250 mm in diameter to carry a pressure of 0.7 N/mm2. Takemaximum tensile stress for cast iron as 14 MPa.A pressure vessel has an internal diameter of 1 m and is to be subjected to an internal pressure of 2.75N/mm2 above the atmospheric pressure. Considering it as a thin cylinder and assuming the efficiencyof its riveted joint to be 79%, calculate the plate thickness if the tensile stress in the material is not toexceed 88 MPa.A spherical shell of 800 mm diameter is subjected to an internal pressure of 2 N/mm2. Find thethickness required for the shell if the safe stress is not to exceed 100 MPa. A bronze spherical shell of thickness 15 mm is installed in a chemical plant. The shell is subjected toan internal pressure of 1 N/mm2. Find the diameter of the shell, if the permissible stress for the bronzeis 55 MPa. The efficiency may be taken as 80%. The pressure within the cylinder of a hydraulic press is 8.4 N/mm2. The inside diameter of the cylinderis 25.4 mm. Determine the thickness of the cylinder wall, if the allowable tensile stress is 17.5 MPa.A thick cylindrical shell of internal diameter 150 mm has to withstand an internal fluid pressure of 50N/mm2. Determine its thickness so that the maximum stress in the section does not exceed 150 MPa.A steel tank for shipping gas is to have an inside diameter of 30 mm and a length of 1.2 metres. Thegas pressure is 15 N/mm2. The permissible stress is to be 57.5 MPa. The ram of a hydraulic press 200 mm internal diameter is subjected to an internal pressure of10 N/mm2. If the maximum stress in the material of the wall is not to exceed 28 MPa, find the externaldiameter. The maximum force exerted by a small hydraulic press is 500 kN. The working pressure of the fluidis 20 N/mm2. Determine the diameter of the plunger, operating the table. Also suggest the suitablethickness for the cast steel cylinder in which the plunger operates, if the permissible stress for caststeel is 100 MPa. Find the thickness of the flat end cover plates for a 1 N/mm2 boiler that has a diameter of 600 mm. Thelimiting tensile stress in the boiler shell is 40 MPa.UNIT – VI - Design of ShaftsDistinguish clearly, giving examples between pin, axle and shaft.How the shafts are formed ?Discuss the various types of shafts and the standard sizes of transmissions shafts.What type of stresses are induced in shafts ?How the shaft is designed when it is subjected to twisting moment only ?Define equivalent twisting moment and equivalent bending moment. State when these two terms areused in design of shafts.When the shaft is subjected to fluctuating loads, what will be the equivalent twisting moment andequivalent bending moment ?What do you understand by torsional rigidity and lateral rigidity.A hollow shaft has greater strength and stiffness than solid shaft of equal weight. Explain.Under what circumstances are hollow shafts preferred over solid shafts ? Give any two exampleswhere hollow shafts are used. How are they generally manufactured ?A shaft running at 400 r.p.m. transmits 10 kW. Assuming allowable shear stress in shaft as 40 MPa,find the diameter of the shaft. A hollow steel shaft transmits 600 kW at 500 r.p.m. The maximum shear stress is 62.4 MPa. Find theoutside and inside diameter of the shaft, if the outer diameter is twice of inside diameter, assuming thatthe maximum torque is 20% greater than the mean torque. A hollow shaft for a rotary compressor is to be designed to transmit a maximum torque of 4750 N-m.The shear stress in the shaft is limited to 50 MPa. Determine the inside and outside diameters of theshaft, if the ratio of the inside to the outside diameter is 0.4.A motor car shaft consists of a steel tube 30 mm internal diameter and 4 mm thick. The enginedevelops 10 kW at 2000 r.p.m. Find the maximum shear stress in the tube when the power is transmitted through a 4 : 1 gearing.A cylindrical shaft made of steel of yield strength 700 MPa is subjected to static loads consisting of abending moment of 10 kN-m and a torsional moment of 30 kN-m. Determine the diameter of the shaftusing two different theories of failure and assuming a factor of safety of 2. A line shaft rotating at 200 r.p.m. is to transmit 20 kW. The allowable shear stress for the material ofthe shaft is 42 MPa. If the shaft carries a central load of 900 N and is simply supported betweenbearing 3 metre apart, determine the diameter of the shaft. The maximum tensile or compressive stress is not to exceed 56 MPa.Two 400 mm diameter pulleys are keyed to a simply supported shaft 500 mm apart. Each pulley is 100mm from its support and has horizontal belts, tension ratio being 2.5. If the shear stress is to be limitedto 80 MPa while transmitting 45 kW at 900 r.p.m., find the shaft diameter if it is to be used for theinput-output belts being on the same or opposite sides. A cast gear wheel is driven by a pinion and transmits 100 kW at 375 r.p.m. The gear has 200 machine cutteeth having 20° pressure angle and is mounted at the centre of a 0.4 m long shaft. The gear weighs 2000N and its pitch circle diameter is 1.2 m. Design the gear shaft. Assume that the axes of the gear andpinion lie in the same horizontal plane.Fig. 14.17 shows a shaft from a hand-operated machine. The frictional torque in the journal bearingsat A and B is 15 N-m each. Find the diameter ( d) of the shaft (on which the pulley is mounted) usinmaximum distortion energy criterion. The shaft material is 40 C 8 steel for which the yield stress intension is 380 MPa and the factor of safety is 1.5.A line shaft is to transmit 30 kW at 160 r.p.m. It is driven by a motor placed directly under it by meansof a belt running on a 1 m diameter pulley keyed to the end of the shaft. The tension in the tight sideof the belt is 2.5 times that in the slack side and the centre of the pulley over-hangs 150 mm beyondthe centre line of the end bearing. Determine the diameter of the shaft, if the allowable shear stress is56 MPa and the pulley weighs 1600 N. Determine the diameter of hollow shaft having inside diameter 0.5 times the outside diameter. Thepermissible shear stress is limited to 200 MPa. The shaft carries a 900 mm diameter cast iron pulley.This pulley is driven by another pulley mounted on the shaft placed below it. The belt ends are paralleland vertical. The ratio of tensions in the belt is 3. The pulley on the hollow shaft weighs 800 N andoverhangs the nearest bearing by 250 mm. The pulley is to transmit 35 kW at 400 r.p.m.A horizontal shaft AD supported in bearings at A and B and carrying pulleys at C and D is totransmit 75 kW at 500 r.p.m. from drive pulley D to off-take pulley C, as shown in Fig.An overhang hollow shaft carries a 900 mm diameter pulley, whose centre is 250 mm from the centreof the nearest bearing. The weight of the pulley is 600 N and the angle of lap is 180°. The pulley isdriven by a motor vertically below it. If permissible tension in the belt is 2650 N and if coefficient offriction between the belt and pulley surface is 0.3, estimate, diameters of shaft, when the internaldiameter is 0.6 of the external.Neglect centrifugal tension and assume permissible tensile and shear stresses in the shaft as 84 MP and 68 MPa respectively. [Ans. 65 mm]The shaft, as shown in Fig. 14.20, is driven by pulley B from an electric motor. Another belt drivefrom pulley A is running a compressor. The belt tensions for pulley Aare 1500 N and 600 N. The ratioof belt tensions for pulley B is 3.5.A mild steel shaft transmits 15 kW at 210 r.p.m. It is supported on two bearings 750 mm apart and has two gears keyed to it. The pinion having 24 teeth of 6 mm module is located 100 mm to the left of theright hand bearing and delivers the power horizontally to the right. The gear having 80 teeth of 6 mm module is located 15 mm to the right of the left hand bearing and receives power in a vertical direction from below. Assuming an allowable working shear stress as 53 MPa, and a combined shock and fatigue factor of 1.5 in bending as well as in torsion, determine the diameter of the shaft.A steel shaft 800 mm long transmitting 15 kW at 400 r.p.m. is supported at two bearings at the two ends. A gear wheel having 80 teeth and 500 mm pitch circle diameter is mounted at 200 mm from the left hand side bearing and receives power from a pinion meshing with it. The axis of pinion and gear lie in the horizontal plane. A pulley of 300 mm diameter is mounted at 200 mm from right hand side bearing and is used for transmitting power by a belt. The belt drive is inclined at 30° to the vertical in the forward direction. The belt lap angle is 180 degrees. The coefficient of friction between belt and pulley is 0.3. Design and sketch the arrangement of the shaft assuming the values of safe stresses as :τ = 55 MPa; σt= 80 MPa. Take torsion and bending factor 1.5 and 2 respectively. A machine shaft, supported on bearings having their centres 750 mm apart, transmitted 185 kW at 600 r.p.m. A gear of 200 mm and 20° tooth profile is located 250 mm to the right of left hand bearing and a 450 mm diameter pulley is mounted at 200 mm to right of right hand bearing. The gear is driven by a pinion with a downward tangential force while the pulley drives a horizontal belt having 180° angle of contact. The pulley weighs 1000 N and tension ratio is 3. Find the diameter of the shaft, if the allowable shear stress of the material is 63 MPa. If in the above Exercise, the belt drive is at an angle of 60° to the horizontal and a combined shock and fatigue factor is 1.5 for bending and 1.0 for torque, find the diameter of the shaft. ................
................
In order to avoid copyright disputes, this page is only a partial summary.
To fulfill the demand for quickly locating and searching documents.
It is intelligent file search solution for home and business.
Related searches
- wordpress passing data between pages
- wordpress business templates
- wordpress rss feed not working
- wordpress jquery is not defined
- create wordpress blog
- wordpress roles editor
- wordpress full rss feed
- wordpress rss feed settings
- wordpress rss feed plugin
- wordpress display rss feed
- wordpress rss feed link
- wordpress rss feed to post