Question

3. What is impact strength, and how is it measured? 4. Why is impact strength an important property in cutting tools? 5. Cemented carbide tools are made by a powder metallurgy method? What is powder matallurgy? lem? See equation 22.1. 21. Why does a TiN-coated tool consume les HSS under exactly the same cutting conditio 22. For what work material are CBN tools m ww2

Answer 1

3. What is impact Test :: Under certain situations, a ductile material fails in brittle manner in the service and such a failure is charecterized by low absorption energ8 - The susceptibility of materials for brittle failures under the exsistence of these factors is determined by some type of tests which apply fast loads like “Inpact Tests" There are various factors which contribute to Boittle type of failure i triaxial state of stress (li) Low Temperature di's High Strain rate ow) Rapid loading. Impact Telt measurment:. Charpy & I zod impact tests are widely - ued across the world.

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0 Champi geometry @î zoid Geomet ty l-55 m (Sample) a notch at Centre d=75 mm (Sample). a norch at less mm forom one end. uso included augle amm depth 0.28mm root radius Ametrica (USA) amm depth uso included angle 0.25 mm routradine & behind notch waded for Sunnot purposes - Great Britain - square or circelian crosscetion - fcantiliverloading in front of notch.

a pendulum te used mop Chan) potential energy is caled Charp! behind noth .1 301 5 loob 132mm. mm 28mm Cantiliver U U Shape hoteh . & Key hole notes v norbich : intron of - notch : We use a dial quage to measuree energy absorbeda : Velocity 3-6 mle Tmax: o ( 14 20 "V has more stress . max & notch is made to know amount of energy for fracture rather than e Shape change

(4) Basically the function of cutting is to cut the specified part from a specimen by wear & friction between the tool å sample surface → In cutting tools we also used very rapid movement so if the tool bit is ductile (soft) Then this tool bit also gets eroded or wears off So, to prevent this hard materials are used for tool bit. y As discurred above for brittle materials under rapid loads impact toughness should be very high. Ex: Take Drill bit rotates at Thousends RPM Ord Abrasive cutting too) alio same. 5) Cemented Carbides are belilally very hand and has very strong bonding (covalent),* So to produce a tool out of cemented carbide is very difficult by conventional Casting because these carbides has very nigh melting points. So, we opt for powder metallurgy route. where we get the powders by precipitation 000) by milling cater compaction followed by sintening. This process gives the best surface finish tham casting so powder - metallingy route is Best