ME 6503-Design of Machine Elements UNIT I 1.Define: Factor of safet
The ratio between maximum stresses to working stress is known as factor of safety safety.. Factor of safety = Maximum stress / Working Working stress !. Define en"#rance limit.
Endurance limit is the maximum value of comletely reversed stress that the standard secimen can sustain an infinite number !"#$% of cycles without failure. 3. $hat is im%act loa"&
&f the time of load alication is less than one third of the lowest natural eriod of vibration of the art' it is called an imact load. '. $hat are the (ario#s %hases of "esign %rocess&
i.(ecog i.( ecognit nition ion of nee need. d. ii. ii.)ef )efini initio tion n of ro roble blem m iii iii.*y .*ynth nthesi esiss iv iv.+ .+naly nalysis sis and ot otimi imi,at ,ation ion v.Evaluation v. Evaluation vi.-resentation 5. $hat are the "ifferent t%es of loa"s that can act on machine com%onents&
a.*teady load. b.ariable b.ariable load. c.*hock load d.&mact load. 6. $hat are the factors affecting en"#rance strength .
Factors affecting endurance strength are i. oad ii. *urface finish iii. *i,e iv. Temerature v. &mact vi. (eliability ). $hat are the t%es of (aria*le stresses&
a.0omletely reversed or cyclic stresses b.Fluctuating stresses c.(eeated stresses +. Differentiate *et,een re%eate" stress an" re(erse" stress.
(eeated stress refers to a stress varying from ,ero to a maximum value of same nature. (eve (e vers rsed ed st stre ress ss of cy cycl clic ic st stre ress ss va vari ries es fr from om one va valu luee of te tens nsio ion n to th thee sa same me va valu luee of comression. . $hat are the t%es of fract#re&
a.)uctile fracture b.1rittle fracture 10. Disting#ish *et,een *rittle fract#re an" "#ctile fract#re.
&n brittle fracture' crack growth is u to a small deth of the material. &n ductile fracture large amount of lastic deformation is resent to a higher deth.
11. Define stress concentration an" stress concentration factor.
*tress concentration is the increase in local stresses at oints of raid change in cross section or discontinuities. *tress concentration factor is the ratio of maximum stress at critical section to the nominal stress 1!. E%lain si/e factor in en"#rance strength .
*i,e factor is used to consider the effect of the si,e on endurance strength. + large si,e ob2ect will have more defects comared to a small one. *o' endurance strength is reduced. &f 3 is the si,e factor' +ctual endurance strength = Theoretical endurance limit x 3 13. E%lain riffith theor. 2r 4tate the con"ition for crac gro,th.
+ crack can roagate if the energy release rate of crack is g reater than crack resistance. 1'. $hat are the mo"es of fract#re&
a.Mode & !4ening mode% 5 )islacement is normal to crack surface. b.Mode && !*liding mode% 5 )islacement is in the lane of the late. c.Mode &&& !Tearing mode% 5 4ut of lane shear. 15. $hat are the factors to *e consi"ere" in the selection of materials for a machine element&
i.(e6uired material roerties ii.Manufacturing ease iii.Material availability iv.0ost 16. $hat are (ario#s theories of fail#re&
i.Maximum rincial stress theory. ii.Maximum shear stress theory. iii.Maximum rincial strain theory. 1).ist o#t the factors in(ol(e" in arri(ing at factor of safet
i.material roerties ii.nature of loads iii.resence of locali,ed stresses iv.mode of failures 1+. i(e some metho"s of re"#cing stress concentration .
i.+voiding shar corners. ii.-roviding fillets. iii.7se of multile holes instead of single hole iv.7ndercutting the shoulder arts. 1. E%lain notch sensiti(it. 4tate the relation *et,een stress concentration factor7 fatig#e stress concentration factor an" notch sensiti(it.
8otch sensitivity !6% is the degree to which the theoretical effect of stress concentration is actually reached. The relation is' 3f = " 9 6 !3t:"% !0. $hat are the factors that effect notch sensiti(it&
i.Material ii.8otch radius iii.*i,e of comonent iv.Tye of loading v.;rain *tructure <". What is the use of ;oodman *oderberg diagrams> They are used to solve the roblems of variable stresses. !! Define machina*ilit
&t is the roerty of the material' which refers to a relative case with which a material can be cut. &t is measured in a number of ways such as comaring the tool life for cutting different material !3. $hat is an 4-N 8#r(e&
+n *: 8 curve has fatigue stress on ? axis and number of loading cycles in @ axis. &t is used to find the fatigue stress value corresonding to a given number of cycles. !'. Define D#ctilit
&t is the roerty of the material enabling it to be drawn into wire' with the alication of tensile force. &t must be both strong and lastic. &t is usually measured in terms of ercentage elongation and reduction in area. !eg% 8i' +l' 0u !5.Define fatig#e
When a material is sub2ected to reeated stress' it fails at stresses below the yield oint stressA such tye of failure of the material is called fatigue. !6. $hat is c#r(e" *eam&
&n curved beam the neutral axis does not coincide with the centroidal axis. !). i(e some eam%le for c#r(e" *eam .
0 frame' crane hook !+. $hat is %rinci%le stress an" %rinci%le %lane&
+ lane which has no shear stress is called rincile lane the corresonding stress is called rincile stress. !. $rite the *en"ing e9#ation.
M/& = E/( = Fs/?. M 5 1ending moment & : Moment of intertia
E : ?oungs modulus ( : (adius of the shaft Fs 5 *hear stress ? : )istance from neutral axis 30. $rite the torsion e9#ation .
T/B = 0C/ = Fs/( T 5 Tor6ue B : -olar moment of intertia 0: (igidity modulus C 5 +ngle of twist 5 ength of the shaft Fs 5 *hear stress ( : (adius of the shaft
UNIT II 1.Define the term critical s%ee" .
The seed' at which the shaft runs so that the additional deflection of the shaft from the axis of rotation becomes infinite' is known as critical or whirling seed. !. Factor is consi"ere" to "esign a shaft&
i.strength ii.stiffness 3.$hat is a shaft&
+ shaft is a rotating machine element'which transmits ower from one oint to another oint. '.$hat are the t%es of shafts&
i.ine shaft ii.*indle iii. *tub shaft iv. 0ounter shaft 5.$hat is e&
+ key is device' which is used for connecting two machine arts for reventing relative motion of rotation with resect to each other. 6.$hat is e&
3ey is a device which is used for connecting tow machine arts for reventing relative motion of rotation with resect to each other. ). $hat are the t%es of es&
i. *addle key ii.Tangent key iii.*unk key iv.(ound key and taer ins. +. o, are s#n e "esigne"&
*unk keys are designed to fit in a sunk key way. Whose bed is arallel to the axis of the shaft. . $hat is the main #se of ,oo"r#ff es&
+ woodruff key is used to transmit small value of tor6ue in automotive and machine tool industries. The keyway in the shaft is milled in a curved shae whereas the key way in the hub is usually straight. 10. ist the (ario#s fail#res occ#rre" in s#n es.
".*hear failure <.0rushing failure 11. $hat is sim%le torsion&
When a shaft is sub2ected to ure torsional moment M' the shaft diameter can be found from torsional shear strength e6uation. *hear strength = "$M/D."dD 1!.$hat is sim%le *en"ing moment&
When a shaft is sub2ect to a ure bending load'the rincial stress induced in the shaft are tension and comression.The maximum stress induced in the shaft can be determined by the theory of simle bending moment relation . 13.$hat are the t%es of rigi"it&
i.Torsional rigidity ii. ateral rigidity. 1'.$hat are the "ifferent meas#res follo,e" to control the lateral "eflection&
i. (educing the san length ii. &ncreasing the number of suorts iii. *electing the cross:section in which the area moment of inertia as in case of hollow shaft. 15.Define the term critical s%ee"&
The seed at which the shaft runs so that the additional deflection of the shaft from the axis of rotation becomes infinite' is known as critical seed. 16. $hat is the f#nction of a co#%ling *et,een t,o shafts&
0oulings are used to connect sections of long transmission shafts and to connect the shaft of a driving machine to the shaft of a driven machine. 1). Un"er ,hat circ#mstances flei*le co#%lings are #se"&
They are used to 2oin the abutting ends of shafts when they are not in exact alignment. They are used to ermit an axial misalignment of the shafts without under absortion of the ower' which the shafts are transmitting. 1+. $hat are the %#r%oses in machiner for ,hich co#%lings are #se"&
".To rovide the connection of shafts of units those are manufactured searately such as motor and generator and to rovide for disconnection for reairs or alterations.
<.To rovide misalignment of the shafts or to introduce mechanical flexibility. D.To reduce the transmission of shock from one shaft to another. .To introduce rotection against over load. 1.$hat are the t%es of ;igi" co#%ling&
i.*leeve' ii.Flange' iii.0lam couling. !0. $hat are the t%es of Flei*le co#%ling&
i.7niversal' ii.4ldhams'iii.-ushed in tye couling. !1.$hat are the main f#nctions of the n#cle
&t is used to transmit axial load from one machine element to other. !!.$hat material #se" for flange co#%ling&
0ast iron !3. Define helical s%rings .
The helical srings are made u of a wire coiled in the form of a helix and is rimarily intended for comressive or tensile load. !'. $hat are the "ifferent t%es of helical s%rings&
The different tyes of helical srings are a.4en coil helical sring b 0losed coil helical sring !5. $hat are the "ifferences *et,een helical torsion s%ring an" tension helical s%rings&
Gelical torsion srings are wound similar to that of tension srings but the ends are shaed to transmit tor6ue. The rimary stress in helical torsion sring is bending stress whereas in tension srings the stresses are torsional shear stresses.
UNIT III 1 o, is a *olt "esignate"&
+ bolt is designated by a letter M followed by nominal diameter and itch in mm. !. $hat factors infl#ence the amo#nt of initial tension&
&.External load ii.Material used iii.1olt diameter 3. $hat is *olt of #niform strength&
+ bolt of uniform strength has e6ual strength at the thread and shank ortion. '. $hat are the ,as to %ro"#ce *olts of #niform strength&
i.(educing shank diameter e6ual to root diameter. ii. )rilling axial hole
5. $hat stresses act on scre, fastenings&
&.&nitial stresses due to screwing u ii.*tresses due to external forces iii.0ombined stresses. 6. $hat are the "ifferent a%%lications of scre,e" fasteners&
The different alications of screwed fasteners are a. For readily connecting disconnecting machine arts with out damage b. The arts can be rigidly connected 0.7sed for transmitting ower ). $hat are the a"(antages of scre,e" fasteners&
The advantages of screwed fasteners are a.They are highly reliable in oeration b.They are convenient to assemble disassemble c.+ wide range of screws can be used for various oerating co nditions d.They are relatively chea to roduce. +.Define %itch.
-itch is defined as the distance from aoint on one thread to the corresonding on the ad2acent thread in the same axis lane. . Define lea".
ead is defined as the distance' which a screw thread advances axially in one rotation of the nut. 10. $hat are the "ifferent t%es of metric threa"&
". 1*W !1ritish standard Whit worth% <. 1*E !1ritish standard End 11. Define ,el"ing.
Welding can be defined as a rocess of 2oining two similar or dissimilar metals with or without alication of ressure along with or without addition of filler material. 1!. $hat are the t%es of ,el"e"
i.1utt 2oint ii.a 2oint iii.T 5 2oint iv.0orner 2oint v.Edge 2oint. 13. $hat are the t,o t%es of stresses are in"#ce" in eccentric loa"ing of loa"e"
".)irect shear stress. <.1ending or torsional shear stress. 1' Define *#tt an" la%
1utt 2ointH The 2oint is made by welding the ends or edges of two lates. a 2ointH
The two lates are overlaing each other for a certain distance. Then welded. *uch welding is called fillet weld. 15.$hen ,ill the e"ge %re%aration nee"&
&f the two lates to be welded have more than $mm thickness' the edge rearation should be carried out. 16. $hat are the t,o t%es of fillet ,el"&
i.ongitudinal or arallel fillet weld ii.Transverse fillet weld 1). 4tate the t,o t%es of eccentric ,el"e" connections.
i.Welded connections sub2ected to moment in a lane of the weld. ii.Welded connections sub2ected to moment in a lane normal to the lane of the weld. 1+. $hat are the %ractical a%%lications of ,el"e"
&t has emloyed in manufacturing of machine frames' automobile bodies' aircraft' and structural works. 1.$hat is Tee-
The two lates are arranged in T shae which means the lates are located at right angles to each other. !0.$hat is corner
Two lates are arranged at right angles such that it forms an angle. !1.$hat are t%es of fillet ,ei"&
i. ongitudinal or arallel fillet weld. &i.Transverse fillet weld. !!.$hen ,ill the ,el" "e%osit *e ,eaer&
When the comonents are made of high carbon steel or alloy steel' the weld becomes weaker. !3.Define eccentricall loa"e" ,el"e"
The external loaded where alied may not ass through the geometric centre in structural 2oints are called as eccentrically loaded 2oints. !'.$hat are the t,o t%es of stress are in"#ce" in eccentric loa"ing of loa"e"
i.)irect shear stress ii.1ending shear stress. !5.4tate the t,o t%es of eccentric ,el"e" connections.
i. Welded connections sub2ected to moment in a lane of the weld. ii. Welded connections sub2ected to moment in a lane normal to the lane of the weld.
UNIT I= 1. $hat is a s%ring&
+ sring is an elastic member' which deflects' or distorts under the action of load and regains its original shae after the load is removed. !. 4tate an t,o f#nctions of s%rings .
i.To measure forces in sring balance' meters and engine indicators. ii.To store energy. 3. $hat are the (ario#s t%es of s%rings&
i.Gelical srings ii.*iral srings iii.eaf srings iv.)isc sring or 1elleville srings '. 8lassif the helical s%rings .
a.0lose 5 coiled or tension helical sring. b.4 en 5coiled or comression helical sring. 5. Define : eaf s%rings
+ leaf sring consists of flat bars of varying lengths clamed together and suorted at both ends' thus acting as a simly suorted beam. 6. Define : >elle(ille 4%rings
They are made in the form of a cone disc to carry a high comressive force. &n order to imrove their load carrying caacity' they may be stacked u together. The ma2or stresses are tensile and comressive. ). $hat is s%ring in"e 8&
The ratio of mean or itch diameter to the diameter of wire for the sring is called the sring index. +. $hat is %itch&
The axial distance between ad2acent coils in uncomressed state. . $hat is soli" length&
The length of a sring under the maximum comression is called its solid length. &t is the roduct of total number of coils and the diameter of wire. s = nt x d Where' nt = total number of coils. 10. $hat are the re9#irements of s%ring ,hile "esigning&
a.*ring must carry the service load without the stress exceeding the safe value. b.The sring rate must be satisfactory for the given alication. 11. $hat are the en" con"itions of s%ring&
a.-lain end. b.-lain and ground end c.*6uared end d.*6uared and ground end.
1!. $hat is *#cling of s%rings&
The helical comression sring behaves like a column and buckles at a comarative small load when the length of the sring is more than times the mean coil diameter. 13. $hat is s#rge in s%rings&
The material is sub2ected to higher stresses' which may cause early fatigue failure. This effect is called as sring surge. 1'. $hat is a laminate" leaf s%ring&
&n order to increase' the load carrying caacity' number of flat lates are laced and below the other. 15. $hat semi ? elli%tical leaf s%rings&
The sring consists of number of leaves' which are held together by 7: clis. The long leaf fastened to the suorted is called master leaf. (emaining leaves are called as graduated leaves. 16. $hat is ni%%ing of laminate" leaf s%ring&
-restressing of leaf srings is obtained by a difference of radii of curvature known as niing. 1). $hat are the (ario#s a%%lication of s%rings&
The srings are used in various alications' they are a.7sed to absorb energy or shocks !e.g. shock absorbers' buffers' e.t.c.% b.To aly forces as in brakes clutches' sring:loaded valves' e.t.c. c.To measure forces as in sring balances and engine indicators d.To store energy as in watches 1+. Define free length.
Free length of the sring is the length of the sring when it is free or unloaded condition. &t is e6ual to the solid length lus the maximum deflection or comression lus clash allowance. f = solid length 9 ?max 9 #."I ?Max 1. Define s%ring in"e.
*ring index !0% is defined as the ratio of the mean diameter of the coil to the diameter of the wire. 0 =)/d !0. Define s%ring rate stiffness.
The sring stiffness or sring constant is defined as the load re6uired er unit deflection of the sring.
3= W/y Where W:load y:deflection !1. Define %itch.
-itch of the sring is defined as the axial distance between the ad2acent coils in uncomressed state. Mathematically -itch = free length/ n:" !!. $hat are the %oints to *e taen into consi"eration ,hile selecting the %itch of the s%ring&
The oints taken into consideration of selecting the itch of the srings are a.The itch of the coil should be such that if the sring is accidentally comressed the stress does not increase the yield oint stress in torsion. b.The sring should not be close u before the maximum service load is reached. !3. Define acti(e t#rns.
+ctive turns of the sring are defined as the number of turns' which imart sring action while loaded. +s load increases the no of active coils decreases. !'. Define inacti(e t#rns.
&nactive turns of the sring is defined as the number of turns which does not contribute to the sring action while loaded. +s load increases number of inactive coils increases from #.I to " turn. !5. $hat are the "ifferent in"s of en" connections for com%ression helical s%rings&
The different kinds of end connection for comression helical srings are a.-lain ends b.;round ends c.*6uared ends d.;round s6uare ends !6. $rite a*o#t the eccentric loa"ing of s%rings&
&f the load acting on the sring does not coincide with the axis of the sring' then sring is said to be have eccentric load. &n eccentric loading the safe load of the sring decreases and the stiffness of the sring is also affected. !). E%lain a*o#t s#rge in s%rings&
When one end of the sring is resting on a rigid suort and the other end is loaded suddenly' all the coils of sring does not deflect e6ually' because some time is re6uired for the roagation of stress along the wire. Thus a wave of comression roagates to the fixed end from where it is reflected back to the deflected end this wave asses through the sring indefinitely. &f the time interval between the load alication and that of the wave to roagate are e6ual' then resonance
will occur. This will result in very high stresses and cause failure. This henomenon is called surge. !+.$hat are the metho"s #se" for eliminating s#rge in s%rings&
The methods used for eliminating surge are a.1y using damers on the center coil so that the wave roagation dies out b.1y using srings having high natural fre6uency. !. $hat are the "isa"(antages of #sing helical s%ring of non-circ#lar ,ires >
a.The 6uality of the sring is not good b.The shae of the wire does not remain constant while forming the helix. &t reduces the energy absorbing caacity of the sring. c.The stress distribution is not favorable as in circular wires. 1ut this effect is negligible where loading is of static nature. 30 $h concentric s%rings are #se"&
a.To get greater sring force with in a given sace b.To insure the oeration of a mechanism in the event of failure of one of the sring 31.$hat is the a"(antage of leaf s%ring o(er helical s%ring&
The advantage of leaf sring over helical sring is that the end of the sring may be guided along a definite ath as it deflects to act a structural member in addition to energy absorbing device. 3!. $rite notes on the master leaf @ gra"#ate" leaf&
The longest leaf of the sring is known as main leaf or master leaf has its ends in the form of an eye through which bolts are assed to secure the sring. The leaf of the sring other than master leaf is called the graduated leaves. 33. $hat is meant * ni% in leaf s%rings&
1y giving greater radius of curvature to the full length leaves than the graduated leaves' before the leaves are assembled to form a sring thus a ga or clearance will be left between the leaves. This initial ga is called ni. 3'. $hat is the a%%lication of leaf s%ring&
The leaf srings are used in automobiles as shock absorbers for giving susension to the automobile and it gives suort to the structure. 35. Define flat s%iral s%ring.
+ flat siral sring is a long thin stri of elastic material wound like a siral. These srings are fre6uently used in watch srings' gramohones' e.t.c
UNIT - = 1.$hat is *earing&
1earing is a stationery machine element which suorts a rotating shafts or axles and confines its motion. !. 8lassif the t%es of *earings.
i. )eending uon the tye of load coming uon the shaftH a.(adial bearing b.Thrust bearings. ii. )eending uon the nature of contactH a.*liding contact b.(olling contact bearings or +ntifriction bearings. 3. $hat are the re9#ire" %ro%erties of *earing materials&
1earing material should have the following roerties. i.Gigh comressive strength ii.ow coefficient of friction iii.Gigh thermal conductivity iv.Gigh resistance to corrosion v.*ufficient fatigue strength vi.&t should be soft with a low modulus of elasticity vii.1earing materials should not get weld easily to the 2ournal material. '. $hat is a
+ 2ournal bearing is a sliding contact bearing which gives lateral suort to the rotating shaft. 5. $hat are the t%es of
".Full 2ournal bearing <.-artial bearing D.Fitted bearing. 6. $hat are the t%es of
".Thick film tye <.Thin film tye D.Gydrostatic bearings .Gydrodynamic bearing. ). $hat is no,n as self ? acting *earing&
The ressure is created within the system due to rotation of the shaft' this tye of bearing is known as self 5 acting bearing. +. $hat is fl,heel&
Flywheel is a machine elements used to minimi,e the fluctuation of seed in a engine.
. $hat is the f#nction of fl,heel&
+ flywheel used in machine serves as a reservoir which stores energy during the eriod when the suly of energy is more than the re6uirement and releases it dulling the eriod when the re6uirement of energy is more than the suly. 10. Define the term Afl#ct#ation of s%ee"B an" Afl#ct#ation of energB .
The ratio of maximum fluctuation of seed to the mean seed is called co efficient of fluctuation of seed. The ratio of fluctuation of energy to the mean energy is called coefficient of fluctuation of energy. 11. 4tate the t%e of stresses in"#ce" in a rim fl,heel&
".Tensile stress due to centrifugal force <.Tensile bending stress caused by the restraint of the arms and D.The shrinkage stresses due to une 6ual rate of cooling of casting. 1!. $hat are the stresses in"#ce" in fl,heel arms&
".Tensile stress due to centrifugal force. <.1ending stress due to tor6ue. D.*tress due to belt tension. 13. o, "oes the f#nction of fl,heel "iffer from that of go(ernor&
+ governor regulates the mean seed of an engine when there are variations in the mean loads. &t automatically controls the suly of working fluid to engine with the varying load condition kees the mean seed with contain limits. &t does not control the seed variation caused by the varying load. + flywheel does not maintain const seed. 1'. $hat is the nat#re of contact in(ol(e" in a *all *earing element&
&nstead of sliding' the contact between the bearing elements is rolling. 15. Define antifriction *earing&
The contact between the bearing elements is rolling' this tye has very small friction. 16. $hat are the t%es of rolling contact *earing&
)eending uon the tye of rolling element' i. 1all bearing ii. (oller bearing )eending uon the load to be carried' i. (adial ii. +ngular contact iii. Trust bearing
1). 4tate the com%onents of rolling contact *earings&
i. 4uter race ii. &nner race iii. (olling element iv. *eerator. 1+. $hat are the se(eral t%es of ra"ial *all *earing&
i. )ee groove ball bearing ii. *elf aligning ball bearing iii. +ngular contact ball bearing iv. Filling notch bearing v. )ouble row bearing. 1. $hat are the t%es of tr#st *all *earings&
i.4ne directional flat race ii. 4ne directional ;rooved race iii. Two directional ;rooved race. !0. $hat is loa" rating&
The load carrying caacity of a rolling element bearing is called load rating. !1. $hat is *asic static loa" rating&
&t is defined as load acting on a non rotating bearing under which ermanent deformation is #.###" times the ball of roller diameter. !!. E%lain the term "namic loa" carring ca%acities of rolling contact *earing&
)ynamic load rating is defined as the radial load in radial bearing that can be carried for a minimum life of one million revolution. !3. ist the t%es of *earing materials&
i. ead base babbit ii. Tin base babbit iii. eaded bron,e iv. 0oer laed alloy v. ;un metal vi. -hoshor bron,e. !'. 4tate the theor of l#*rication&
i. Gydrostatic theory of lubrication. ii. Gydrodynamic theory of lubrication. !5. Define Cinematic (iscosit&
The kinematic viscosity is defined as the ratio of a bsolute viscosity to the density of oil.
