Question

PART B: Choose any one or two problem(s) from Part B. 5. a) (6 marks) In many applications, the designer has the choice of specifying cast iron, or cast steel for a part For a spoke-type flywlieel (heavy hub and rim, relatively lighter spokes), compare the two materials with respect to: i) manufacturing (cost, ease of manufacture, etc), and ) design (various strength properties, ductility, etc.) b) (1 marks) The bodies and frames of many recently designed vehicles have structural members constructed from closed tubes which have been shaped by hydroforming. These members have complex shapes of varying cross section- 1) Discuss the advantages of using hydroforming for the designers: ü) What construction method(s) would have been used before the introduction of hydroforming? iii) Why would the manufacturing eõgineers specify that an axial-compressive load be applied to the tubes during the hydroforming operation? c) (7 marks) Welding is the preferred attachment method for low alloy steel parts in many applications. However, welding may be difficult, or impossible, with heat-treated, and withi high alloy steels. Discuss the problems and solutions if any) of these two cases.

Answer 1

For A spoke-type Cast-foon flyn el ti whe Cast iron fly wheels are the Cheapest Cost iron flywheel con be given any complex shape without involving mochining operation Cast iron fly-wheel has excellent to ability vibration domp Cost iron has pood Lensile tensile strength compared to The steel Cast iron failure of the machinability is sudden and to top. of Cast iron flywheel is poor wheel Compo ored to steel ffy standard Weight Flyn Materials loc wheel Joon Flywheel (Cost-ison 25-40 pounds Cost goog + iron contains flokkes of gooprite Thot develops oluring the cooling proces

distinctive & These flakes give grogirona gray color when fractured, and they are also a poot of the alloy's physical properties Goog iron flywheels con be used as A stock replacement and in mild builds but should never be amosciated with racing, high horse prever, sticky dong radial tires or engine that operate are beyond 6,000rpm Cost iron has more Compressive strength thon steel properties of Cast iron is that it is brittle, more damping and absorb Vibration and noises * Cast iron is cheaper than steel and has point with the abipity to mord easily low meeting

Ca Atree crociss ast Steel The advantages of cost steel over the cast iron is that they weight the some, usunely around 25-30lbs, the steel unit is significantly stronger. It remains free and therefore sofe at high engine speed and high clutch clamping forces. Steel flywheel operate more effectively with modern high performance cluten friction materials thom do their cast-iron counterparts hos decisive advantage of Carrying minimal weight. → It has high tensile strength and more ductility It is Costlier than ► at Cost iron.

soforming arts Tight dimensional tolerance and (6) Benefit of hydroforming Hydro- is the manufac cturing of follow bodies with complex geometries by means of fluid pressure Extroordinary Design Flexibility Fewer por Lower tooling Cost due to fewer ports - Weight reduction through more efficient section design Improved structural strength Scros and stiffnes * Fewer secondary operations duced Re bock low spring Tighter tolerance (O Before the introduction of hy droforming, Convention of deep drawing been used. (iii) Manufacturing engineers specify that an axial of compuenire . have lond he

opplied to the tubes during the hydroforming operation, so that element of the tubes de form without thinning and tearing is delayed ent of