UNIVERSITY OF TORONTO

FACULTY OF .PILIFi) SCIENCE AND ENGINEERIN(

FIN A L 1, ;j)til 25, 2019 SeCOfiti \ CtF Iroraiu 1

(IV 209F - EN(;INEERIN; M ATERI A LS

E xaminers— I'.. I). 1Iooton and \. Sa\uira

Duration: 2.5 hours

III

(Print in capital letters) ( LAST) (F! RST)

Stll(ldflt No.:

Only non-procramniahie calculators and rulers are permitted.

Point lorni answers are both acceptable and encouraued. Sketchesdiacrams are also encouraed

to support your answers v here appropriate. Read each question carellil lv helore ansenn. State am additional asswllptions you make as part o \ our answer.

Answer ALL questions in the spaces pros ided. Lse the hacks of pages, ii' extra space i needed. but show clearly on the page ot the question v here the v ork is continued.

Make sure \ our name appears on the test paper.

Student No .:

Question I - True and False ( 15 marks)

True or False. Circle the correct answer.

Cellulose is ihe primary molecule responsible br the strcnath ol wood. I F

ii. So I'm ood coffim ns approximatel 10 '̀ iibcrs. F F

1 1ardaoods exhibitine a rine porous structure are generally more anisotropic F F than hardwoods exhibiting a diffuse porous siructure.

I v. AS MC decreases below the FSP. the strenuth of wood increases. I F

he cambium undergoes repeated cell di\ ision to form new wood and bark. F F

vi. Particle hoard is an anisotropic material. [ F

it. In the blast furnace, iron oxides are chemically oxidized. F F

viii. It takes more energy to reline iron than aluminum. 1 F

I\. If' austenite is quenched to 170 1 C. the amount. ot Mariensite present will F F

increase as time goes on.

Toughness and ductility increase as the wt. C in the steel increases. 1 F

(old-rolling decreases the strength and increases the toughness of steel. F F

Precipitation hardened aluminum allo\ s are well suited for high temperature I F

app1 ic at it n s.

Cup and cone fracture morphology is observed in ductile materials. I F

Stainless steel can undergo pitting corrosion. I I

xv. Polv methyl methacrvlate is a crystalline polymer. F I

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Student No.:

Question 2 — Wood A natomy (10 marks) INc (Iiacrani beIo describes the anatoni of a tree. Define and bricllv describe the 5 missin labels in the diagram. In \ our description rcter to the structure and lunclion ot each of the elements. 10 marks)

Axial (grain) direction

Radial direcuo

od

Tangential direction

Outer bark Inner bark Rays

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tudcnt No.:

Question 3 - \ I icrostructure of Tim her (10 marks) a) Fxpl:iin \\ h "nod is considered to be a natural composite, and how its structure causes it

anisotropic behaviour. marks

Discuss the dil1rences heteen I racheids and Fibres. I l() do these di Iterenees a1!ct the properties of timber? (4 Marks)

C) I Fa piece of wood ith a MU of 5W was dried to an [MC of 12%, in vhicli direction ould the wood experience the greatest dinieiisional chane? What tYpe of deIct "odd

you expect this dry ing to cause? Explain. mith reference to the microstructure of the \\ood. (4 marks)

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Student No.:

Question 4 - \IcchanicaI Behaviour of 'Fitt] her (10 marks)

LO What is the 12 ellCral influence on strength or using a \\ood species with a hi gher density? 2 marks

H What is the iniluence of reducing the numher of knots on the strcnth of 'aood? (2 marks)

C) What are the two kinds ol knots that may he found in vood? Briefly describe each 1'. pe. (4 marks

(1 ) List 2 alternate approaches in designing, a 'a ood frame structure to have sulfic icnt fire resistance to prevent premature collapse. (2 marks )

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Student No.:

Question 5 - Fe-(-' Phase Diagram (25 marks) sing the Fe-C binary phase diagram at the end ol' the exam. ans er the hal lo\\ ing questions:

a) Name the phases present in the diagram and identify their crystal structure 15 marks )

Phase Common Name

-------------

Crystal Structure

(I:

F e C --

Why doesn't martensite appear on the binary Fe-C phase diagram.' (2 mark)

;\ mild steel conta I nIng 0.5OC is cooled very slowly from 1000°C to 300C. Draw and ihc I the ni IL i otI uLtul L U I 000°C 800"C. and ',()W'('. (6 ma rks)

1000°C S0ftC OO°C

d) For each o the temperal ares stale the composition of the phases present in the al by, and their respective weight fraction. (0 marks)

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Studcnt No.:

c) \ hvpoeulcctoid sicI that as s1O\\ ly cooled l'rom 920 'C to 72 C was tound to contain 39 \ t.° o cutectoid fcrnte (u). What is the carbon content ol' the steel? (6 mark)

Student No.:

Question 6 -No n-F(jui I i I) rium \Iicrostructures (10 marks) king the LI F diagram and CCI' diagram pros ided at the end ol the exam. anser the Ibllo\ving:

a) For a steel held initially at 1000 C consider the following cooling schemes and name the resultijig m icrostructure( S ) marks)

Quenched to 200C

ii. Quenched to 4()°C. held for 10 s, and then iuenched to 100 °C

Fxplain \\ liv martensite is often tempered and describe the resulting microstructure. (4 marks)

e ( Discuss the engineering shortcomings of materials v ith metastable structures. (4 marks)

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Student No.:

Question 7 - Corrosion (15 marks) ScN eral hundred laree storace tanks were installed III a major plant eNpansion. Older tanks \ crc

fibricated of carbon steel, and the inner surlices \\ crc coated entirely with a baked phenolic paint. INc old tanks had ser ed \\ ell for many years. but coating damage on the bottom caused product contamination. the new tank bottoms were uperadcd \vith stainless-steel-clad carbon steel har better service and reduced niaintenance. The same phenolic coating, as then applied O\ er the tank \vall surtices as ith the old tanks, and over the eIded unetion v ith the tank bottom. as sho\\ in Figure I he inherently resistance stainless steel bottoms were left uncoated. [he plant operators ere surprised hen leaks developed in the tank walls just abo\ e the \\elded junction alter onl\ a l\ months of ser ice despite their \\ell-inlcntioned tank upgrades.

subsequent in\ estigations re ealed that localited pinhole corrosion had de eloped through the coating. All coatings have dehcts in the form of' pinholes. hol ida\ s and mechanical damace.

On the next page. explain (using, a point form I Miv accelerated corrosion took place on carbon steel despite the presence of' an inner coating. Do not explain \0v the coating !iiled. only lcus on the metal components! \lso. come up v n.h a solution to this problem by suggesting, diffrcnt materials, a different design or both.

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tudnt No.:

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Student No.:

Question 8 - Welding, (10 marks) a) With reards 10 welding. \ hat is the I 1:\t"? What chancs in the parent metal ma\

occur in the 11\t? 1 low would they influence the mechanical properties of the metal? (3 marks)

hI Which ot the lollowinLt two steel al loy s IS more weldable? I low would you improve the weld qualit for the less eldable alloy? (4 marks)

SAF Grade 411 : 0.3% Cr. 0.1% Mo. 0Th C. 0.9% \ln. 0.1 Si S:\ [ Grade 4130: 1.0% Cr. 0.15('/,o Mo. 0.18'!'o C. 0,4% Mn. 0.15% Si

C) I 1o\ does the thickness ol the plate to he welded altects its weldahi!itv? 3 marks)

Student No.:

Question 9 - PoRmer (10 marks) a) In an orLaniLcd point lorm manncr. c'pIain all of the processc or niicroiruetural clliInc

that may he used to increase the strength ot a polymer. Four distincti\elv di l'trent approaches are required to obtain lull marks lur this question. 15 Marks]

\\'hat polymer \ould ou recommend using br a piping application? Rationalize your selection and hih1ight the relationship hct\\cen the structure and the properties of this polymer. 15 Marks

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Studciit No.:

ViJii + IVO Si lXoCr + Mo + %V Cit + %N CE=YoC+ + +

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