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B: Tech vI semester (Main/Bdck) Examination, May/Jun e-zfJllMechanical Engineering (CommonJor Mech., p & D

, 6MEI Design of M/c Elements - IITime :3 Hours Maximum Marks : 80

Min. Passing Marks : 24

Instructions to Csndidates:Attempt any Jive questions, selecting one ques;tion from each unit. All questionscarry equal marks. (Schematic diagrams must be shown wherever necessarv.Any data you feel missing suitably be osisumed and stated clearly. tlnits Lyqtwntities used/calculated must be stated ctearly.)U s e offo I I ow in g s upp ort ing mat er ial is p erm itt e d dur ing exam in at i o n.in form No. 205)l. Design Data Handbook.

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Unit-I :

Explain stress concenfiarion,:its causes and how it can be mitigated. (6)Determine the diameter ofa circular rod made of ductile material with a fatiguestrength (complete sftess reversal) oe:280Mpa and a tensile yield strengthof 350 MPa. The member is subjected to a varying axial load from 700 kN to- 300 kN. Assume \: 1.8, f.S : Z. : , (10)

-oRWrite soderberg's equation and stateloadings.

a) its application to different type of(6)

b) Determine thethickness of'a 130 mm wide uniforrn plate for safe continuousoperation if the plate is to be subjected to a tensile load that has a maximuinvalue of 240kN and a minimum va'lue of I 00 kN. The properties of the platematerial are as follows:

Endurance limit stress :225Mpa: jirro point stress:300 Mpa. The factorof safety based on yield point stressl: 1,5. (10)

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Unit - II2. a)

- Discuss the'sigqifieance of the fu]itialtightening l,oad and the applied load sofar as bolts ffie concerned. Explain which of the abcve loads must be greaterfqr a properry desigded bolted joint and how eaeh affecJs llp total load on thebolt. (6)

b) A steam engine cyliaderofsize 3ffimmx'4ffimm operates at I .5Nlmm2 pressure.The rylinder head is cormected by means of 8 bolts having yield point stressaf350 MPa and e*d$rance limit of 240 MPa. The bolts are tightened with ar*initial pre load af 1.8 times the steam load. The joint is made leak proof byusing seft copper gasket which renders the effect of extemal laad to be half.Determine the size of bolts, if frctor af safety is 2 and stress concentrationfactor is 3. (10)

ORDesrgn a serewjackfarlifting a load cf 50kN thraugh a height of0-25m. The screw

Iis made ofsteel forwhic*r Ranikine's constants are 330N/mm2 and

,r* forcolumnpin j*inted atboth ends. tlse a'f,actor of safety of 4. The nut i, *ua. of gunmetalfor which d =251f lrnmt. Bearing pressure on the threads is timited tc l0N/rnm2.The nut is fixed in C.t. housing and the screw islturned in the nut by using a tommybar inserted in suitable holes ia the head of the screw. The caefiicient offriction of

' the threads md collar may be taken as O.12.Unit - fiI

3 . a) ,- Discrlsthe meterials and practical applications forthe various types of springs.,(6)

b) A semi-elliptical faminated spring is to carry a'load of 300$Nand consists of.

spring. The spring is to be l.Irn in length and is to be attachedrto the axle bytwo U bclts 75r* apart The leav&s are to k made of silica manganese steei-Assu*ring au allowable stress af 350N/mrn", determine the thiekness for theIeaves end the defFeetion. (r0)

ORa) Uuder what circumstances a fibre rope and a wire rope is used? Whatare ihe

advantages oFa wire rope over fibre rope? t6ib) A V-bott having a lap cf 180 degrees has a cross sectional area *f 2.5 sq. cm

and nms in a groove of includedangle Zs = 41degrees. The density ofthe beltis 0.00S5 kg pet orrr. pm and the maximum stress is limited to 40 kg per sq.'cm, ecefficient'of frietionbeirg 0.15. Find the maximtrm power that can betransmitted if the whAel has a ffiean diameter of 3t) cm and,rens at 1000 rpm.

(10)

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Unit - IV4. a) Explain the phenornenon of interference in involute'gears. What are the

.conditions ts be satisfred in order tc avoid interference?b) A pair of spur gears trangnitting power from a motor to a pump impeller shaft

is to be designed with as small a centre distance as possible. The forged steelpinion (So: 160 MN/m2) is to transmit 4kW at 600 revlmin to a cast steel gear(So :'l00MN/m2) with a transmission ratio af 4% to I and 20" full depthinvolute teeth are to be used. Determine the necessary facewidth and modulefor strength only using the Lewis equation.

(6)

(10)OR

a) Discuss with neat sketches, the various types of worms and worm gears. (6)b) A pair of precision cut helical steel gears on parallel shafts with a centre

distance of 380mm transmits power with a velocity ratio of 4 to 1 . The pinionrotates at 10,000 rev/min. Both gears aremade from the same material, havingS, = I A\MN lm2. The teeth are 20o stub, with a 45o helix angle. The facewidth is 20mm, and the module is I . Determine the maximum power that canbe transmiued safely, considering wear and strength. Both gears have a brinellshardness of400. (10)

Unit - V' vltrl5. a) Explainwe-dgefilmandsqueezefilmjcurnal bearings. (6)

b) A water lubricated lffimm diameter by l00mm long full bearing supports aload of 1300N. The shaft rotates ai 1000 rev/min. The diameter clearance is0-lmm and the water has viscosity 0.0003kg/ms. Assume c:4200Nm/kg"Cand F : t-S$ k#-m;. U-sitg'$qiffisudi and,iBoyal. curves, determine tlrecoefficient offriction, the minimum fihn thickness, the flow of lubricant intopeaiilg the end leakage oflubricant the temperature rise ofoil and the powerIess due to friction. (10)

ORWrite shcrt note an classifications and different types of antifriction bearings.

A single row deep groove ball bearing has a specific dynamic .upur,,r(l|46.3 kN (for 1,000,000 revolutions or 500 hours at 33.3 rev/rnin, thatg}Yo ofa group ofbearings will complete or exceed).

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Ifthe speed of rotation is 1800 rev/min and the actualmdial load appliedtothe bearing is 9 klrl. What is the life in revolutions?

ii) How many hours ofoperation can be expected for the above?mi WhatisJhe uu"rugl" life that can beexpected? (10)

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