ANNA UNIVERSITY CHENNAI
REGULATION 2013
ME6503-DESIGN OF MACHINE ELEMENTS
UNIVERSITY QUESTIONS
UNIT-IV
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PART-A
1. Define surge in a spring?
2. What is nipping of a leaf spring?
3. Define the term fluctuation of energy with reference to flywheels.
4. What is meant by semi elliptical leaf springs?
5. A helical spring of rate 12N/mm is mounted on the top of another spring of rate 8 N/mm. find
the force required to give a deflection of 50mm.
6. What is the purpose of flywheel that is used in an IC engine?
7. What is constant width and constant strength springs?
8. Define spring index.
9. What is Wahl factor and why is it required?
10. What is the objective of the nipping of the leaf spring?
11. Write the advantage of Belleville spring.
12. Write the formula for natural frequency of spring.
13. How does the function of flywheel differ from that of governor?
14. In what respect the flywheel differs from the governor.
15. What type of external forces act on connecting rod?
Part – B
1. A safety valve, 50mm in diameter, is to blow off at a pressure of 1.5 MPa. It is held on its seat by means of a helical compression spring, with an initial compression spring, with an initial compression of 25mm. the maximum lift of valve is 10mm. the spring index can be taken as 6. The spring is made of patented and cold drawn steel wire with ultimate strength of 1500N/mm²and modulus of rigidity of 81370N/mm². The permissible shear stress for thespring wire should be taken as 30% of the ultimate strength. Design the spring and calculate :
(i) Wire diameter;
(ii) Mean coil diameter;
(iii) Number of active turns;
(iv) Total number of turns;
(v) Solid length of spring;
(vi) Free length of spring;
(vii) Pitch of the coil.
2. A helical compression spring is used to absorb the shock. The initial compression of the spring is 30mm and it is further compressed by 50mm while absorbing the shock. The spring is to absorb 250J of energy during the process. The spring index can be taken as 6. The spring is made up of patented and cold drawn steel wore with an ultimate tensile strength of 1500N/mm² and modulus of rigidity of 81 kN/mm². The permissible shear stress for the spring wire should be taken us 30% of the ultimate strength. Design the spring and calculate :
(i) Wire diameter
(ii) Mean coil diameter
(iii) Number of active turns
(iv) Free length &
3. Design a helical spring for a spring loaded safety valve (Ramsbottom safety valve) for the following conditions: Diameter of valve seat = 65mm; Operating pressure = 0.7 N/mm²; Maximum pressure when the valve blows off freely = 0.75 N/mm²; Maximum lift of the valve when the pressure rise from 0.7 to o.75 N/mm² =3.5 mm; Maximum allowable stress= 550MPa; Modulus of rigidity = 84 kN/mm²; Spring index = 6.
4. Design a cast iron flywheel used for a four stroke. I.C engine developing 180 kW at 240r.p.m. The hoop or centrifugal stress developed in the flywheel is 5.2 MPa, the total fluctuation of speed is to be limited to 3% of the mean speed. The work done during the power stroke is 1/3 more than the average work done during the whole cycle. The maximum torque on the shaft is twice the mean torque. The density of cast iron is 7220 kg/m³.
5. A Spring loaded safety valve for a boiler is required to blow off at a pressure 1.5N/mm².The diameter of the valve is 60 mm. Design a suitable compression spring for the safety valve, assuming spring index to be 6 and 25 mm initial compression. The maximum lift of the valve is 15 mm. The shear stress in the spring material is to be limited to 450 Mpa. Take G=0.84 Mpa.
6. A Multi cylinder engine is to run at a constant load of 600 rpm. On drawing the crank effort diagram to scale of 1 mm=250 N-m and 1 mm ,the areas in square mm above and below the mean torque line were measured and found to be in order +160,-172,+168,-191,+197,and -162.The speed is to be kept within ±1% of the mean speed of the engine. Determine the moment of inertia of the flywheel.
7. A Closed coil helical compression spring has plain ends and is to fit over a 25 mm diameter rod. When a compressive force of 100 N is applied to the spring it compressed by 50 mm. If the spring has a perfect wire diameter of 4mm, and the spring material has a maximum allowable shear stress of 180 MN/ and a modulus of rigidity81GN/m2.Determine, a) the mean coil diameter of the spring. (b)The diametrical clearance between the spring and the rod. c) The number of coil in the spring. (d)The solid length of the spring.
8. The areas of the turning moment diagram for one revolution of a multi cylinder engine with reference to the mean turning moment, below and above the line are -32,+408,-267,+333,-310,+226,-374,±260 and -244.The scale for abscissa ordinate are:1mm= and 1mm=650 N-m respectively.The mean speed is 300 rpm with a percentage speed fluctuation of ±1.5%.If the hoop stress in the material of the is not to exceed 5.6 Mpa, determine the suitable diameter and cross section for the flywheel, assuming that the width is equal to 4 times the thickness. The density of the material may be taken as 7200 Kg/.Neglect the effect of the boss and arms.
9. Design a closed coiled helical compression spring for a load range varying from 2.25 KN to 2.75 KN and corresponding axial deflection of 6mm.Spring index is 5.Permissible shear stress is 400 N/ and modulus of rigidity is 80 KN/.
10. The turning moment diagram of an engine has areas above and below the mean torque line of +530,-330, +380,-470,+180,-360,+350 and -280 sq.mm. The scales of the diagram are:Turning moment 1mm=1000 N-m, Crank angle=1mm=.The mean speed is 150 rpm and the total fluctuation of speed is not to exceed 3% of the mean speed. Design a suitable flywheel.
11. A Helical compression spring made of oil tempered carbon steel is subjected to a load which varies from 400 N to 1000N.The spring index is 6 and the design factor of safety is 1.25.If the yield stress in shear is 770 MPa and endurance stress in shear is 350 MPa, find (a) Size of the spring wire, (b) Diameter of the spring, (c) Number of turns of the spring, (d) Free length of the spring. The compression of the spring at the maximum load is 30 mm. The modulus of rigidity for the spring material may be taken as 80 KN/.
12. A Single cylinder double acting steam engine delivers 185 kW at 100 rpm. The maximum fluctuation of energy per revolution is 15% of the energy developed per revolution. The speed variation is limited to 1% either way from the mean. The mean diameters of rim are 2.4m.Design and draw two views of flywheel.
13. Determine the dimensions of an I section connecting rod for a petrol engine from the following data: Diameter of piston=110mm, Mass of reciprocating parts=2Kg, Length of the connecting rod from centre to centre = 325 mm,Stroke length=150mm,R.P.M=1500 with possible over speed of 2500, Compression ratio=4:1, Maximum explosion pressure=2.5 N.
14. The turning moment diagram of a multi – cylinder engine is drawn with a scale of (1mm= 1˚) on the abscissa and (1mm = 250 N-m) on the ordinate. The intercepted areas between the torque developed by the engine and the mean resisting torque of the machine, taken in order from one end are -350, +800, +600, +900, -550, +450 and -650mm². The engine is running at a mean speed of 750rpm and the coefficient of speed fluctuations is limited to 0.02. A rimmed flywheel made of grey cast iron FG 200(p= 7100 kg/m³) is provided. The spokes, hub and shaft are assumed to contribute 10% of the required moment inertia. The rim has rectangular cross section and ratio of width to thickness is 1.5. Determine the dimensions of rim.
15. Design a suitable connection rod for a petrol engine for the following details. Diameter of the piston =100 mm; Weight of reciprocating parts per cylinder =20 N; Connecting rod length =300 mm; Compression ratio =7:1; Maximum explosive pressure = 3N/mm²; Stroke = 140mm; Speed of the engine = 2000 r.p.m.
16. The following data is given for a rimmed flywheel made of grey cast iron FG 200:
Mean radius of the rim = 1.5 m
Thickness of rim = 200 mm
Width of rim = 300 mm
Number of spokes = 6
Cross sectional area of the each spoke = 10000 mm²
Speed of rotation = 720 rpm
Calculate:
(i) The tensile stress in rim at = 30˚ and = 0˚
(ii) The axial stress in each spoke
(iii) The mass density of cast iron FG 200 is 7100 kg/m³
For all the units of DME and other mechanical engineering subjects study materials is uploaded see right side of the page you can download whatever materials you need to study or copy and paste the following link :annaunivstudymaterials.blogspot.com
12. A Single cylinder double acting steam engine delivers 185 kW at 100 rpm. The maximum fluctuation of energy per revolution is 15% of the energy developed per revolution. The speed variation is limited to 1% either way from the mean. The mean diameters of rim are 2.4m.Design and draw two views of flywheel.
13. Determine the dimensions of an I section connecting rod for a petrol engine from the following data: Diameter of piston=110mm, Mass of reciprocating parts=2Kg, Length of the connecting rod from centre to centre = 325 mm,Stroke length=150mm,R.P.M=1500 with possible over speed of 2500, Compression ratio=4:1, Maximum explosion pressure=2.5 N.
14. The turning moment diagram of a multi – cylinder engine is drawn with a scale of (1mm= 1˚) on the abscissa and (1mm = 250 N-m) on the ordinate. The intercepted areas between the torque developed by the engine and the mean resisting torque of the machine, taken in order from one end are -350, +800, +600, +900, -550, +450 and -650mm². The engine is running at a mean speed of 750rpm and the coefficient of speed fluctuations is limited to 0.02. A rimmed flywheel made of grey cast iron FG 200(p= 7100 kg/m³) is provided. The spokes, hub and shaft are assumed to contribute 10% of the required moment inertia. The rim has rectangular cross section and ratio of width to thickness is 1.5. Determine the dimensions of rim.
15. Design a suitable connection rod for a petrol engine for the following details. Diameter of the piston =100 mm; Weight of reciprocating parts per cylinder =20 N; Connecting rod length =300 mm; Compression ratio =7:1; Maximum explosive pressure = 3N/mm²; Stroke = 140mm; Speed of the engine = 2000 r.p.m.
16. The following data is given for a rimmed flywheel made of grey cast iron FG 200:
Mean radius of the rim = 1.5 m
Thickness of rim = 200 mm
Width of rim = 300 mm
Number of spokes = 6
Cross sectional area of the each spoke = 10000 mm²
Speed of rotation = 720 rpm
Calculate:
(i) The tensile stress in rim at = 30˚ and = 0˚
(ii) The axial stress in each spoke
(iii) The mass density of cast iron FG 200 is 7100 kg/m³
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