4. Readthearticlecarefullyandanswerthefollowingquestions.

   1. Whatobjectshavebecomethetargetsofscrapmetalthieves?

   2. Whatpartsofthecountrysufferfromcriminalsmost?

   3. Whatmakesthetrendofscrapmetaltheftdangerous?

   4. Whyisthesituationturningintoanissueofagreatconcern?

   5. WhatdoesCCTVstandfor?

   6. Whatdoesthelastsentenceofthearticleimply?

4.Matchtheitalicizedadjectiveswiththeirdefinitions.

a)___________________________veryunusualorremarkable

TheEconomist

b)______________________ableorlikelytoshatterviolentlyorburstapartc)______________________________________________easilysetonfire

4. ___________________notcontrolledorsupervisedbyregulationsorlaws

5. _________________placeswhicharefarawayfromlargetownsorcities

6. ______________________________ableorlikelytocauseharmorinjuryg)__________________________________producingagreatdealofprofith)_______________________________________notregularorpermanent

i) _____ _____________havingaconsistencylikethatofwateroroil,i.e.,flowingfreelybutofconstantvolume.

Self-assessmentvi1.Translatethearticleusingadictionary.PayattentiontotheNon-Finiteformsoftheverb.

ConventionalEngineeringMaterials

Therearemorethan50,000materialsavailabletoengineersforthedesignandmanufacturingofproductsforvariousapplications.Thesematerialsrangefromordinarymaterials(e.g.,copper,castiron,brass),whichhavebeenavailableforseveralhundredyears,tothe

morerecentlydeveloped,advancedmaterials(e.g.,composites,ceramics,andhigh-performancesteels).Duetothewidechoiceofmaterials,today’sengineersareposedwithabigchallengefortherightselectionofamaterialandtherightselectionofamanufacturingprocessforanapplication.Itisdifficulttostudyallofthesematerialsindividually;therefore,abroadclassificationisnecessaryforsimplificationandcharacterization.

Thesematerials,dependingontheirmajorcharacteristics(e.g.,stiffness,strength,density,andmeltingtemperature),canbebroadlydividedintofourmaincategories:(1)metals,(2)plastics,(3)ceramics,and(4)composites.Eachclasscontainslargenumberofmaterialswitharangeofpropertieswhichtosomeextentresultsinanoverlapofpropertieswithotherclasses.

Themaximumoperatingtemperatureinmetalsdoesnotdegradethematerialthewayitdegradestheplasticsandcomposites.Metalsgenerallytendtotemperandageathightemperatures,thusalteringthemicrostructureofthemetals.Duetosuchmicrostructuralchanges,modulusandstrengthvaluesgenerallydrop.Themaximumtemperatureisthetemperatureatwhichthematerialretainsitsstrengthandstiffnessvaluestoatleast90%oftheoriginalvalues.

Metalshavebeenthedominatingmaterialsinthepastforstructuralapplications.Theyprovidethelargestdesignandprocessinghistorytotheengineers.Thecommonmetalsareiron,aluminum,copper,magnesium,zinc,lead,nickel,andtitanium.Instructuralapplications,alloysaremorefrequentlyusedthanpuremetals.Alloysareformedbymixingdifferentmaterials,sometimesincludingnonmetallicelements.Alloysofferbetterpropertiesthanpuremetals.Forexample,castironisbrittleandeasytocorrode,buttheadditionoflessthan1%carboninironmakesit

tougher,andtheadditionofchromiummakesitcorrosion-resistant.Throughtheprincipleofalloying,thousandsofnewmetalsarecreated.

Metalsare,ingeneral,heavyascomparedtoplasticsandcomposites.Onlyaluminum,magnesium,andberylliumprovidedensitiesclosetoplastics.Steelis4to

7timesheavierthanplasticmaterials;aluminumis1.2to2timesheavierthanplastics.Metalsgenerallyrequireseveralmachiningoperationstoobtainthefinalproduct.Theyprovidethelargestdesignandprocessinghistorytotheengineers.

SanjayK.Mazumdar,Ph.D.COMPOSITESMANUFACTURING