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GUJARAT TECHNOLOGICAL UNIVERSITY
DIPLOMA ENGINEERING – SEMESTER – • EXAMINATION – SUMMER-2015
Subject Code: 3351902 Date:04/05 /2015
Subject Name: DESIGN of MACHINE ELEMENTS
Time: 2:30 pm to 5:00 pm Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make Suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
4. Use of programmable & Communication aids are strictly prohibited.
5. Use of only simple calculator is permitted in Mathematics.
6. English version is authentic.
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Q.1 Answer any seven out of ten. 14
1. State types of design and explain any one .
2. What are the general considerations in machine design .
3. Explain stress concentration.
4. Factors affecting the value of factor of safety.
5. State advantages of standardization.
6. Determine 6 standard spindle speed of the machine having minimum and max. speed are 224 rpm & 710 rpm.
7. State application of cotter joint.
8. State types and application of leaf spring .
9. Mention machine subjected to eccentric loading.
10. Write assumptions made in the design of thin cylinder.
Q.2 (a) Find rod diameter and spigot diameter for cotter joint ifaxial load is 75 KN. , [τ] = 4/5[6t] ,[6t] = 50 N/mm^2 and [6c] = 100 N/mm^2 03
OR
(a) State & explain failures of Riveted joints. 03
(b) Determine rivet diameter to join 12 mm thick m.s. plates bysingle riveted lap joint. The pitch is 70 mm. find shearing efficiency of joint if [τ] = 60 N/mm^2 ,[6t] = 80 N/mm^2 03
OR
(b) Find socket diameter & socket collar diameter for given data in example 2(a) 03
(c) A knuckle joint to connect two m.s. rods of equal diameter having axial tensile load of 15 KN. [τ] = 60 N/mm^2 ,[6t] = 80 N/mm^2 and [6c] = 150 N/mm^2 find basic dimensionswithout considering bending. 04
OR
(c) State & explain standard elements & their location on a welding symbol. 04
(d) Fulcrum pin of a bell crank lever is to be designed where 7000N. load acting on longer arm is to be lifted. The length of arms is 400 mm & 100 mm . [τ] = 50 N/mm^2 ,[6t] = 70 N/mm^2 &[Pb]= 15 N/mm^2. Find diameter and length of fulcrum pin .do not consider bending. 04
OR
(d) A semi elliptical spring with 900 mm span and 55 mm width of leaves is fixed in the centre using 50 mm wide bend. If thickness of eachleaf is 5 mm , find number of leaves to sustain 5500 N load in the centre. [6b]= 490 N/mm^2. Also find deflection of the spring . first 2 leaves arefull length .E=210 N/mm^2 04
Q.3 (a) Find the diameter of the shaft to transmit 80 hp at 150 rpm. [τ] = 63 N/mm^2 03
OR
(a) A solid shaft is subjected to bending moment of 3.46 kN.m and torque of 11.5 kN.m . 6ut =690 Mpa. Ultimate τ = 516 Mpa. Find shaft diameterby equivalent torque if factor of safety is 6. 03
(b) A pulley is fixed on a 100 mm diameter shaft with the help of 100 mm long key. the shaft transmit 6000 N.mtorque with this key. Find dimension of key if 6uc =500 N/mm^2 and Ultimate τ = 250 N/mm^2. Factor of safety is 5. 03
OR
(b) State the design step for muff coupling. 03
(c) State fundamental equation of twisting moment. 04
OR
(c) A valve spring having inner diameter of a coil 40 mm , deflects for 40 mm at the maximum axial load of500 N. Find wire diameter and number of turns for the spring . [τ] = 300 N/mm^2 , spring index =6 and G = 0.82 x 10^5 N/mm^2 04
(d) 20 kN vertical loads are acting at the end of the “C” clamp having a rectangular cross section. The perpendicular distance between the load axis and the neutral axis of the cross section is 150 mm. Find the dimensions of the cross section of the clamp for the permissible stresses of 100 N/mm^2 (h=2b) 04
OR
(d) Write applications, classification and main consideration for design of pressure vessels. 04
Q.4 (a) A cylinder with 150 mm inside diameter and 15 mm plate thickness is subjected to internal pressure of 5 N/mm^2.find hoop stress ,longitudinal stress and max. shear stress in the cylinder. 03
OR
(a) A ram of a hydraulic cylinder having 200 mm internal diameter is subjected to oil pressure of 10 Mpa. If the permissible stress for the cylinder material is 28 Mpa. Find outside diameter of the cylinder. 03
(b) Explain bearing characteristic number & bearing life. 04
OR
(b) Explain antifriction bearing with applications & advantages. 04
(c) A protected type flange coupling has to transmit 40 KW. At 450 rpm . Shaft, key & bolts are made from steel . Considering effect of overload & key way effect .Find shaft diameter, hub diameter, bolt diameter. Assume [τ] = 45 N/mm^2 for shaft & bolt, [6t] = 10 N/mm^2 forhub. 07
Q.5 (a) A circular steel pipe has outer diameter of 60 mm and thickness of 3 mm. If the ,[6t]pipe = 60 N/mm^2, Find the permissible axial load forthe pipe. Also find the diameter of solid round barof same material as pipe for the same load. 04
(b) A deep groove ball bearing having SKF 6309 number is rotating at 1500 rpm. the bearing is subjected to radial load of 8500 N and thrust load of 5500 N. The inner race of the bearing rotate with shaft . find the rating life and average life of the bearing . the dynamic capacity of the bearing is 41500 N and the bearing is in continuous service .Take X= 0.56 & Y=1.3 04
(c) State comparison between knuckle joint & cotter joint 03
(d) State types of stresses on machine elements and explain briefly. 03
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