ME6503 Design of Machine Elements Important Questions

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Design of Machine Elements – Important Questions PART – B Design Design the rectang rectangula ularr key for a shaft shaft of 50 50 mm diamet diameter er.. The The shea shearin ring g and and crush crushing ing stresses stresses for the key material are 42 MPa and 70 MPa. Design Design and make make a neat neat dime dimensi nsione oned d sketc sketch h of a muff muff coup couplin ling g hich hich is is used used to to conne connect ct to to steel shafts transmitting 40 k! at "50 rpm. The material for the shafts and key is plain car#on steel for hich alloa#le shear and crushing stresses may #e taken as 40 MPa and $0 MPa respecti%ely. The material for the muff is cast iron for hich the alloa#le shear stress may #e assumed as 15 MPa. Desig Design n a clamp clamp coup coupli ling ng to tran transm smit it "0 k! k! at 100 100 rpm. rpm. The The allo alloa# a#le le shea shearr stress stress for for the shaft and key is 40 MPa and the num#er of #olts connecting the to hal%es are si&. The  permissi#le tensile stress for the #olts is 70 MPa. The coefficient of friction #eteen the muff and the shaft surface may #e taken as 0.". Desig Design n and dra dra a prot protec ecti ti%e %e type type of cast cast iron iron flang flangee coupl couplin ing g for a steel steel shaf shaftt transm transmit ittin ting g 15 k! at 200 rpm and ha%ing an alloa#le shear s tress of 40 MPa. The orking stress in the  #olts should not e&ceed "0 MPa. 'ssume that the same material is used for shaft and key and that the crushing stress is tice the %alue of its shear stress. The ma&imum tor(ue is 25) greater than the full load tor(ue. The shear stress for cast iron is 14 MPa. The shaft shaft and and the the flan flange ge of of a marin marinee engin enginee are to #e #e desig designed ned for flange flange coupli coupling* ng* in hic hich h the flange is forged on the end of the shaft. The folloing particulars are to #e considered in the design+ Poer of the engine , " M!- peed of the engine , 100 rpm- Permissi#le shear stress in  #olts and shaft , /0 MPa- um#er of #olts used , $- Pitch circle diameter of #olts , 1./ & Diameter of shaft. ind+ 1. Diameter of shaft- 2. Diameter of #olts- ". Thickness of flangeand 4. Diameter of flange. Desig Design n a knuc knuckl klee oint oint to tran transm smit it 150k 150k. . The The desi design gn stre stresse ssess may #e #e taken taken as 75 75 MPa MPa in tension* /0 MPa in shear and 150 MPa in compression. Design Design a knuck knuckle le oint oint for a tie tie rod rod of of a circ circula ularr sectio section n to sustain sustain a ma&i ma&imum mum pull pull of 70 k. k. The ultimate strength of the material of the rod against tearing is 420 MPa. The ultimate tensile and shearing strength of the pin material are 510 MPa and "3/ MPa respecti%ely. Determine the tie rod section and pin section. Take factor of safety , /. Determ Determine ine the the leng length th of of the the eld eld run run for for a plat platee of sie 120 mm ide ide and 15 mm mm thick thick to #e #e elded to another plate #y means of+ 1. ' single trans%erse eld- and 2. Dou#le parallel fillet elds hen the oint is su#ected to static and %aria#le loads.

' elded elded oint oint as as shon shon in in figur figuree is su# su#ect ected ed to an eccen eccentric tric load load of 2 k. ind ind the the sie sie of  eld* if the ma&imum shear stress in the eld is 25 MPa.

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' rectangular crosssection #ar is elded to a support #y means of fillet elds as shon in figure. Determine the sie of the elds* if the permissi#le shear stress in the eld is limited to 75 MPa.