Sardar Vallabhbhai National Institute of Technology 2012 B.Tech Mechanical Engineering Machine Design-I - Question Paper

SARDAR VALLABHBHAI NATIONAL INSTITUTE OF TECHNOLOGY, SURAT

Mechanical Engineering Department B.Tech - III (Mechanical Engg.) Sem - VI April-May-2012 (End Sem. Examinations)

Subject: Machine Design- I (ME 302)

Time: 2 Hrs    Max. Marks: 50

Instructions: 1. Attempt all questions as per the instructions..

2.    Draw neat sketches, wherever necessary.

3.    Attempt both sections (Section-A, Section-B)

4.    Use of design data book is permitted.

SECTION-A    (;

Q. 1 (A) Write Goodmans equation and state its application to different type of loadings. ((

(B) A 50 mm diameter shaft is made from material having ultimate tensile strength of (( 630 MPa. It is subjected to a torque which fluctuates between 2000 N-m to -800 N-m. Calculate the F.O.S. Assume yield stress for material in reversed bending as 510 N/mm², surface finish factor of 0.67, size factor of 0.87 and fatigue stress concentration factor as 1. Take endurance limit as 0.5 of ultimate strength.

OR

A hot rolled steel shaft is subjected to a torsional moment that varies from 330 Nm clockwise to 110 Nm counter-clockwise and an applied bending moment at a critical section varies from 440 Nm to - 220 Nm. The shaft is of uniform cross-sectioii and no keyvvay is present at the critical section. Determine the required shaft diameter. The material has an ultimate strength of 550 MN/m² and a yield

_______ ...... strength of 410 MN/m².Take endurance limit as 0.5 of ultimate strength, F.O.S. of

2, size factor of 0.85 and surface finish factor of 0.62.

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Q.2 (A) Derive the relation for strength of single and double transverse fillet welded joint. ((

(B) A plate 75 mm wide and 12.5 mm thick is joined with another plate by a single (( transverse weld and a double parallel fillet weld as shown in Fig.. The maximum tensile and shear stresses are 70 MPa and 56 MPa respectively. Find the length of each parallel fillet weld, if the jointjsj;ubjected to both static and fatigue loading

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75 n

l

OR

A bolt subjected to an axial pull oflO kN and a transverse shear force of 5 kN. The yield strength of the bolt material is 300 MPa . Considering a F.O.S. of 2.5.Find the diameter of the bolt, using (i.) Max. normal stress theory, (ii.) Max. shear stress theory,(iii.) Max. principal strain theory,

Q. 3    Write short note on following (ANY TWO)    (I

(1.) Fatigue failure criteria,

(II.) Stress concentration factor,

(111.) Max. Principal Strain Energy Theory,    *

(IV.) Failures of riveted joint. v    p

Q.4

(24)

SECTION B Attempt any TWO (02) from the following

Find out type of fit by calculating the maximum and minimum clearance or interference in the following case - 60H₇f₈ , 50H₈g₇

A spring is provided for spring loaded safety valve shown in fig-4 with following data.

Maximum pressure on the valve = 1 MPa Valve diameter=50 mm Maximum lift of the valve 10 mm Initial compression =30 mm

Shear stress =450 MPa, G=8* 10⁴ MPa. Spring Index=6

Calculate (1.) wire diameter (2.) coil diameter, (3.) Number of turns, (4.) Solid length.

When should we use differential screw? What is the condition of self locking of (4) screw?

Design a bell crank lever shown in fig-5 of rectangular cross section and fulcrum pin to raise the load of 1000N at the at shorter arm. The following allowable    (8)

stresses can be assumed. For lever a,=20 MPa, a_c =100 MPa, fb =10 MPa. And for fulcrum pin at .90 MPa, o_c =100 MPa, t=60 MPa, and Pb=20 MPa.

Attachment: sardar-vallabhbhai-national-institute-of-technology-2012-b-tech-mechanical-engineering-4498-1.jpeg sardar-vallabhbhai-national-institute-of-technology-2012-b-tech-mechanical-engineering-4498-2.jpeg

Earning:   Approval pending.