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SVENSSON JOSEF
1 3 4 6 1 1 3 7
Building Science A C S S 4 0 0
22 02 2012
John Begg
E3
CW2 Lab Report
Svensson, Josef
Szelag, Marlena 133685081
Ten, Stanislav 133184171
Wang, Xu 136072501
Woods, Nicholas 133795461
E3
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YoungsModulusofElasticity
BySvenssonJosef,SzelagMarlena,TenStanislav,WangXu,WoodsNicholas
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Contents:
1. Objectivespg.32. Procedurepg.33. Observationspg.34. Resultspg.45. Discussion pg.66. Conclusion pg.107. References pg.118. Bibliography pg.119. CertificatesofAttendance
andSignedDeclaration pg.12
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Objective:TodetermineEforsoftwood(ParanaPine)andonehardwood(Mahogany[Keruing])usingathreepointbendingjig.
TodetermineEforoneferrousmetal(LowCarbonSteel0.3%)andonenonferrous(Brass60/40)usingaanelectronicextensometer.
Procedure:AsLabSheet.
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Observations:TogetYoungsModulus,E,formetals,suchasBrassandMildSteel,thetestinvolvesloadingthespecimenintensionandmeasuringtheresultingextension.Duringtheexperiment,therewasnovisiblechange.Themetalsamplestestedintension,didnotchangevisiblyinanyway,normadeanysound.
SincemetalshaveahighYoungsmoduli,largeforcesmustbeappliedtoproducemeasurableextensionsinsmallspecimens,howevernoneofthemodificationswerenoticeableaswedidnotgopasttheYoungsmodulus,thereforenotcausinganyvisibledeformation.
YoungsModulus,E,fortimberismeasuredbycarryingoutthetestincompressionmodeusingtestingmachinefittedwithathreepointbendingjig.Inthiscase,howeverthechangesweredetectible,asthetimbersamplesdidslightlybendundertheappliedloadandsprungbackwhentheloadwasremoved.
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Results:
60/40Brass87x25.74600=F=1639.4N0.0180.002=x=0.016mm1639.4/pix(7.97/2)^20.016/50=102690Nmm^2102690x10^6=102690000000Pa=102.69GPaYoung'smodulusof70/30BrasshasYoung'smoduluswithavalueof100GPa.Ourcalculatedvalueisthereforerelativelycorrect.
0.3%CarbonSteelMildsteel(110x80)(110x22)=F=6380N0.040.01=x=0.03mm6380/pix(7.97/2)^20.03/50=213138.99Nmm^2213139x10^6=213139000000Pa=213.139GPaTheYoung'smodulusofourmildsteelisapproximately213GPa,thevaluethatwearegivenaccordingtothetableis210whichisthereforerelativelycorrect.
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TimberParanaPine(120^3/419.637.63^3)340/3.96 =4254Nmm^24254110^6=4254000000Pa
=4254MPa
TimberMahogany(120^3/4x20.08x7.55^3)290/2=7248Nmm^27248x1x10^6=7248000000Pa=7248MPa
Material Published value CalculatedvalueMildsteel 210GPa 213.139GPaBrass 100GPa 102.69GPa
Mahogany 010000MPa 7249MPa
Pine 1120020000MPa 4253MPa
Toconclude,inmosttheresultsfromtheexperimentpresenteduswithaYoung'sModulusclosetothegivenvaluesforthematerials.Thefindingspresentediswith3GPaincaseofthetestedmetalsandtimberpublishedvaluescouldonlybefoundinthetermsofMPa.Mega=1x10^6Giga=1x10^9
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Discussion:
Question1:CompareyourresultswithpublishedvaluesofE.Comment.
Material Published value CalculatedvalueMildsteel 210GPa 213.139GPaBrass 100GPa 102.69GPa
Mahogany 010000MPa 7249MPa
Pine 1120020000MPa 4253MPa
ThetableaboveshowsthevaluesofEthatwegotfromourexperimentandtheprovidedvaluesthatarequotedonvariousinternetandbooksourcesastowhattheactualvalueis(Kermani1999,andMatbase).
Thetableshowsthatthemildsteelandbrassvaluesarerelativelyclose,withonlyasmallvariationfromthepublishedvalues,howeverthetimbermaterialsofParanaPineandMahoganyseemtobeoutbyalargeamount,pineinparticular.Thiscanindicatethatthemetalshavelessvariationinqualityofthematerial,asthesamplestestedwasclosetotheindustrystandardsone,whereasthePinematerialmayhavebeenanolderorweakerdespitebeingofthesameorigin.
WehavedoublecheckedtheEvaluesfortimbertomakesurethatourvalueswerecorrectandhaveresearchedseveralotherwebsitesthatmayprovideuswiththepublishedvaluesofE,inallcasesParanapinewasoutbyalargeamountwhereasmahoganyfellwithintheapproximaterange,showingthatthesamplethatwehadwouldnothavemettheindustrystandardsastheEvalueisconsiderablylessthanthosethathavebeenpublished.
ThepublishedvalueofBrassthatwehaveusedwasintheexperimenthandbook,thegivenvaluewasgivenfor70/30brass,meaningthatitwas70%copperand30%zinc,whereasoursamplewas60/40.DuetocopperhavinghigherYoungsmodulusthanzinc,thatwouldmeanthattheoreticallyourvalueof60/40shouldhavebeenlowerthanthatof70/30,itwasinfacthigher,butstilllikelywithinarationalmarginoferror,ourvaluesmayhavebeendifferentduetoerrorincalculationoftheareaorcalculationofthegradientofthegraphthatwewereprovidedwith.
Insummary,thevaluesthatwehaveattainedhavebeenrelativelyclosetothepublishedvalueswiththeexceptionoftheParanapine,itmayhavebeenduetofaultysampleorotherunknownvariationthatcausedtheEvaluetobeconsiderablylowerthanthepublishedvaluesfoundontheinternet.
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Question2:Distinguishbetweencomponentstiffnessandmaterialstiffness.
Stiffnesscanbedescribedastheabilityofamaterialtomaintainitsshapewhenacteduponaload(CraneandFurness1997p.92)anddependsontheYoungsmodulusofthematerial,howtheloadisperformingonitandbythegeometricalshapeofthespecificpieceofthatmaterial.
Thecomponentstiffnesswillchangedependingontheshape,size,lengthandapplicationofthematerial.IllustratedinFigure1itisevidentthatasthesampleismodified,itisabletowithstandmoreload.However,thecomponentstiffnessdoesnotonlydependontheyoungsmodulusofthematerialusedbutalsoonhowthematerialisloadedwhetherthroughtensionorbending.
Figure1:Showingthreebeamswithequalcrosssectionarea.(CraneandFurness1997p.94)
Therefore,duringthedesignstage,componentstiffnesscanbeimprovedamaterialcanbeusedtodeflectundermoreloadsbeforedeformingpermanently,whereasitisimpossibletochangethematerialsinheritedstiffnessalsoknownastheYoungsmodulus,whichisuniquetoallmaterials.Forexample,changingthecarboncontentcanimprovethestiffnessofamaterial,allowingittowithstandmoreweightthroughreinforcementofmoleculesbutthecomponentstiffnesscanbechangedwithoutmodificationonmolecularlevelbyjustvaryingthesizeorlengthofthesamematerial.AmaterialwithalowEvaluethatbysomereasonispreferredoveranothermaterial,byaestheticreasonsorotherproperties,cantherebyhaveitsstructuraldesignmodifiedsoitcanovercomeitsdisadvantagesofhavingalowmaterialstiffness.Forinstanceatimberjoistofaspecifictimbercanbeproduceswithdifferentdimensionstobeabletowithstanddifferentload.Thestiffnessofthetimberitselfwillnotchangebutthemanipulationofthegeometricalshapewillhavechangedthetimberjoistscomponentstiffness.
Question3:Onthebasisofresults,whichmetalismostsuitableforstructuralapplications?Explainwhy
Onthestressstraindiagramofourexperimentresults,itshowsastraightlinebetweenstressandstrain.Itmeansanincreasestressoccursaproportionateincreasestrain.This
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factisknownasHookesLaw.Itcanbeexpressedmathematicallyas=E.TheconstantofproportionalityEistheYoungsmodulus(Hibbeler,2011)p.156.Youngsmodulusisameasurementofmaterialsstiffnessorresistancetoelasticdeformationunderload(WilliamD.Callister,2010).Hence,thehigherEvalue,thestifferthematerial.Inthetable6.1somemetalsyoungsmodulusispresented.
(WilliamD.Callister,2010)p.157
Onthebasisofourexperimentresults,theYoung'sModulusofcarbonsteelis213.139GPa.ItismuchhigherthantheYoung'sModulusofbrass,whichis102.69GPa.Inotherwords,thecarbonsteelisrelativelyastiffermaterial.Astiffmaterialmeansitchangesitsshapeonlyslightlyunderelasticloads(UniversityofCambridge,DepartmentofEngineering,2002).Inrealitythestructuralapplicationsarerequiredtobeasstiffaspossible,sothatitisabletowithstandtheloadsappliedtobuildings.
Furthermore,carbonsteelalsoisahighlyductilematerial.Itmeansitisabletoreturntoitsoriginaldimensionwhenthestressisreleasedwithinitselasticlimit.Ifthestresscarriesonbeyondtheelasticlimit,itwillnotbeabletoreturntoitsoriginaldimensionwhenthestressisreleased,butitwillnotbefracturedimmediately(Leslie,2007).
Inconclusion,carbonsteelhashighstiffness,highductilityandelasticlimit.Thesepropertiesmeettherequirementsofstructuralapplicationsneedsaswellasitcanbeusedtocalculatetheloadbearingcapabilities.Thereforeitcanbeusedpreciselyandeconomically.Thatiswhycarbonsteelisthemostsuitableforstructuralapplicationsofthemetalstested.
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Conclusion:Inconclusion,theseseriesofexperimentstofindoutyoungmodulusofvariousmaterialshelpedustounderstandthateachmaterialhasadifferentloadbearingcapacitybeforeitbeginsdeformingpermanently.Asaresult,itiswisetoselectmaterialsappropriateforthespecificstructurebeforebeginningconstruction.Ifweknowwhatthetotalsumofallloadswouldbeonthebuilding,wecanuseappropriatematerials,suchasusingmetalswithhighcarbonpercentageforthebuildingswhichareexpectedtosustainbigloadstomakesurethatthebuildingdoesnotcollapseasaresultofmaterialdeformation,whichcanoccuraftertheEvaluehasbeenreached.
Wehavealsodiscoveredthecomponentandmaterialstiffness,andidentifiedthedifferencesinboth,whereascomponentstiffnesscanbeimprovedthroughmodificationofsizeofthesampleorlength,thematerialstiffnessremainsthesameunlessthematerialitselfismodifiedinawayourswere,suchasthebrassbeingcombinationofcopperandzinc,changingthe%wouldhaveadirectimpactupontheyoungsmodulus.
Theexperimentalsoshowedthateverymaterialhasauniqueyoungsmoduli,notallmetalshavethesameEvalue,nordoalltimber.Insomecasescombiningthematerialssuchasthebrassbeingcombinationofcopperandzinc,theyoungsmoduluswasactuallylowerthanthosematerialswouldhavehadindividually,despitetheloweryoungsmodulus,itislikelythatthecomponentstiffnessofthematerialwasgreaterthaniftheyweretestedindividually.
Wehavealsoworkedwithwhatappearedtobeafaultysample,asthequotedbookvalueofEwasconsiderablyhigherthanwhatwehadattained;thissortofexperimentisusefulindeterminingwhetherthematerialprovidedbythesupplierisingoodenoughconditiontobeusedfortheplannedconstruction;decreasingthechanceofaccidentsorcollapseofthebuilding.
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References:CraneF.A.A.andFurnessJ.(1997)SelectionandUseofEngineeringMaterials,3rdEd,ElsevierScience&TechnologyBooks
KermaniA.(1999)StructuralTimberDesign,Cambridge:Blackwellscience
LESLIE,J.A.A.T.(2007).Designtech:Buildingscienceforarchitects..1stEdition.Oxford:ElsevierLtd.
MatbaseMECHANICAL,PHYSICALANDENVIRONMENTALPROPERTIESOFMATERIALS,[online]Availablefrom:http://www.matbase.com/material/wood/
WILLIAMD.CALLISTER,J.D.G.R.(2010).Materialsscienceandengineering:anintroduction.8thEdition.USA:JohnWiley&Sons,Inc.
Bibliography:
HIBBELER,R.C.(2011).MechanicsofMaterials.8thEdition.USA:PearsonPrenticeHall
UniversityofCambridge,DepartmentofEngineering,(2002).PropertyInformationYoung'sModulusandSpecificStiffness[online]Availablefrom:[Accessed30Jan2012]
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AnisotropyofTimber
BySvenssonJosef,SzelagMarlena,TenStanislav,WangXu,WoodsNicholas
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Contents:
1. Objectivespg.192. Procedurepg.193. Observationspg.204. Resultspg.225. Discussionpg.286. Conclusion pg.337. References pg.34 8. Bibliography pg.349. CertificatesofAttendance pg.35
AndSignedDeclaration
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Objectives: Samplesofstraightgrainpine,plywoodandchipboard,at0,45and90aregiventoexaminehowtheyareaffecteddifferentlywhencompressionforceisapplied.Forthemaininvestigationweareaimingtoestablishtherelationshipbetweenstrengthandgraindirection.Twospecimensofeachmaterialateachorientationweretested.
Procedure:AsLabSheet.
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Observation:Duringtheexperiment,wehavetestedstraightgrainedtimber,plywoodandchipboardinturns,withcutsparallel,45degreesandperpendiculartothegrainineachofthesamples.Thedifferentsampleshaveallexperiencedsomesortofvisibledamage,insomecasesitwasseveresuchastheexamplefallingapartcompletelybutinmosttherewerevisiblecracksandloudcreakingwhenthepressurewasappliedonthem.
StraightGrainedtimberwasthefirstsamplestested,slightcreakingcouldbeheardduringtheapplicationoftheweightanddeformationofthesampleshasbecomeevidentafterweremovedthesamples.
Theplywoodsampleshaveexperiencedconsiderablymoredamagethanthetimber,althoughthedamagewasnotapparentuntilweveremovedthepressurefromthesamples,audiblecreakingcouldbeheardassamplesbeganbreakingasaresultoftheload.
Figure2:Plywoodaftercompression,Fromrighttoleft:04590
Figure3showshowthechipboardhasbeenaffectedbythepressure,inthecaseonfarright,thesamplehascrackednoticeably,whereasthesamplesthathaveparallelandthe45degreecuthavenotexperiencedasdrasticofachangeintermsofdamage.Duringtheexperiment,loudaudiblecreakingcouldbeheard,butlikeinthecaseofPlywood,visibledamagewasnotapparentuntilafterthe
Figure1:StraightGrainedTimber(BritishColumbianPine)aftercompression.Fromrighttoleft:04590
Figure3Chipboardaftercompression,Fromrighttoleft:04590
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sampleshavebeenremoved.
Duetoourinexperiencewithusingthisparticulartestingequipmentwefailedtocorrectlyadjusttheequipmentbetweensamplesonafewoccasionswhichledtoinconclusivedataasaresult.Thesesampleswerereplacedwithsamplesofthesamepropertiesandthetestingwasredone.Allresultspresentedbelowarefromsamplestestedcorrectly.
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Results:FailureStress=FailureLoad/OriginalCrosssectionalarea
FailureStress/Area=FailureLoad
TabulateddimensionsandresultsforAnisotropyofTimber.StraightGrainedTimber(BritishColumbianPine).
Timberat0
1. Area:14.9915.31=229.5mm75.1229.4969=17,235N(FailureLoad)
2. Area:14.8715.13=225.0mm59.8225=13455N
Timberat45
1. Area:15.7615.03=236.9mm13.1236.9=3103.39N
2. Area:15.6615.16=237.4mm21.3237.4=5056.74N
Timberat90
1. Area:15.4715.23=235.6mm7.2235.6=1696.32N
2. Area:15.1015.68=236.8mm6236.8=1420.60N
Table1
TimberStraightGrainedTimber[BritishColumbianPine]
Width(mm)
Thickness(mm)
Originalcrosssectionalarea(mm)
Maximumload(N)
FailureStress(N/mm)
FailureLoad(N)
At0degrees 14.99 15.31 229.5 17,244 75.1 17,235
At0 14.87 15.13 225.0 13,458 59.8 13,455
At45 15.76 15.03 236.9 3,107 13.1 3,103
At45 15.66 15.16 237.4 5,064 21.3 5,057
At90 15.47 15.23 235.6 1,702 7.2 1,696
At90 15.10 15.68 236.8 1,413 6.0 1,421
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Resultsinaverage,calculatedfromtableabove
Table2
Graph1:ShowingThefailurestressofBritishColumbiaPinesamplestested
TabulateddimensionsandresultsforAnisotropyofTimber.Plywood.
Plywoodat0
1. Area:14.6715.16=222.40mm30.3222.4=6738.7N
2. Area:15.1214.50=219.24mm39.9219.24=8747.7N
75,10
13,107,20
59,80
21,30
6,000
10
20
30
40
50
60
70
80
Failu
reStress(N/m
m)
Graindirection
BrittishColumbiaPine sample1 sample2
0 degree 45degeree 90degree
TimberStraightGrainedTimber[BritishColumbianPine]
Width(mm)
Thickness(mm)
Crosssectionalarea(mm)
MaximumLoad(N)
FailureStress(N/mm)
FailureLoad(N)
At0 14.93 15.22 227.3 15,351 67.45 15,345
At45 15.71 15.1 237.2 4,086 17.2 4,080
At90 15.29 15.46 236.4 1,558 6.6 1,559
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Plywoodat45
1. Area:14.6514.77=216.38mm10.1216.38=2185.4N
2. Area:14.7214.65=215.70mm9.9215.7=2135.4N
Plywoodat90
1. Area:14.9814.91=223.40mm29.5223.4=6590.3N
2. Area:14.9814.62=219.00mm28.4219=6219.6N
Table3
Resultsinaverage,calculatedfromtableabove
Table4
Plywood Width(mm)
Thickness(mm)
Originalcrosssectionalarea(mm)
Maximumload(N)
FailureStress(N/mm)
FailureLoad(N)
At0degrees 14.67 15.16 222.4 6,733 30.3 6,739
At0 15.12 14.50 219.2 8,757 39.9 8,748
At45 14.65 14.77 216.4 2,183 10.1 2,185
At45 14.72 14.65 215.7 2,127 9.9 2,135
At90 14.98 14.91 223.4 6,587 29.5 6,590
At90 14.98 14.62 219.0 6,222 28.4 6,220
Plywood Width(mm)
Thickness(mm)
Crosssectionalarea(mm)
MaximumLoad(N)
FailureStress(N/mm)
FailureLoad(N)
At0 14.9 14.83 221.0 7,745 35.1 7,744At45 14.69 14.71 216.1 2,155 10 2,160At90 14.98 14.77 221.3 6,405 29 6,405
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Graph2:ShowingThefailurestressofPlywoodsamplestested
TabulateddimensionsandresultsforAnisotropyofTimber.Chipboard.
Chipboardat0
1. Area17.6917.80=314.90mm19.9314.9=6267N
2. Area17.7017.66=312.60mm20312.6=6252N
Chipboardat45
1. 17.7517.74=314.90mm19.3314.9=6078N
2. 17.7317.62=312.40mm19312.4=5937N
30,30
10,10
29,50
39,30
9,90
28,40
0
5
10
15
20
25
30
35
40
45
Failu
reStress(N/m
m)
Graindirection
Plywood sample1 sample2
0 degree 45degeree 90degree
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Chipboardat90
1. 17.9617.69=317.70mm18.9317.7=6005N
2. 17.6817.84=315.40mm17.7315.4=5583N
Table5
Resultsinaverage,calculatedfromtableabove
Table6
Chipboard Width(mm)
Thickness(mm)
Originalcrosssectionalarea(mm)
Maximumload(N)
FailureStress(N/mm)
FailureLoad(N)
At0degrees 17.69 17.80 314.9 6,216 19.9 6,267
At0 17.70 17.66 312.6 6,241 20.0 6,252
At45 17.75 17.74 314.9 6,080 19.3 6,078
At45 17.73 17.62 312.4 5,933 19.0 5,937
At90 17.96 17.69 317.7 5,998 18.9 6,005
At90 17.68 17.84 315.4 5,574 17.7 5,583
Chipboard Width(mm)
Thickness(mm)
Crosssectionalarea(mm)
MaximumLoad(N)
FailureStress(N/mm)
FailureLoad(N)
At0 17.7 17.73 313.8 6,251 19.95 6,260
At45 17.74 17.68 313.6 6,007 19.15 6,008
At90 17.82 17.77 316.7 5,786 18.3 5,794
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Graph3:ShowingThefailurestressofChipboardsamplestested
19,90
19,30
18,90
20,00
19,00
17,70
17,5
18
18,5
19
19,5
20
20,5
Failu
reStress(N/m
m)
Graindirection
Chipboardsample1 sample2
0 degree 45degeree 90degree
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Discussion:
Question1:Explainthevariationincompressivestrengthoftimberwithtestdirection.Anisotropyisthestateorqualityofhavingdifferentpropertiesalongdifferentaxes.Theanisotropyoftimbercanbetestedusingacompressiontest;thisconsistsoftwoplatescompressingtogethertotellustheboundsatwhichamaterialcantakebeforeeventuallyfailing.Wecanthenunderstandthematerialsstructuralpropertiesanditscompressivestrength.Compressivestrengthistheabilitytosupporttheforcesexertedontoamaterialatdifferentdegrees.Thematerialthenreachesalimittowhichitcanwithstandandthenbucklesundertheload.Atalternatedegreesamaterialhasdifferentcapacitiesatwhichitisabletosupportacompressiveload.
Timberisanaturalmaterial,whichhasuniquecharacteristicsandstructuralproperties;thisisduetothenatureofthegrain.Thegraingivesthetimberitsstrength.Tounderstandthis,thenatureofthegrainwassubjecttoacompressivestrengthtest,twiceat0paralleltothegrain,twiceat45,andtwiceat90perpendiculartothegrain.Inordertotryandachievearoughaveragethetestwascarriedouttwice,thisalsocatersforfailedtests.
Wecanclearlyseefromtheresultspresentedearlierthattestdirectionproducesdifferentresults.Itshowsusclearlythattestingparalleltothegrainiswherethetimberhasmostofitsstructuralproperties.Overthetworesultsofeachspecimenwecanalsounderstandthata90degreesturnofthetestdirectioncandecreasethestructuralpropertiesbyanaverageof13,794N.Thecompressivestrengthoftimberat0isgreaterthantimberat90tothegrain.Thevariationincompressivestrengthcouldbeduetothecellalignmentinthetimber.Thegrainismadeupoftimbercells,towhich90%ofthesearealignedvertically.Sowhenthespecimeniscompressedtheverticallyalignedtimbercellsresistthebendingmoment,actinglikeawebofasteelbeam.Theverticalcellsrequiremoreforcetocompresswhereaswhenthespecimenisrotated90thecellsareverticallyalignedmakingthemeasytocompressandeventuallycausingthematerialtobuckleundertheload.Oncethegrainisrotatedto45and90theresistancedecreases.Thisissincecovalentbondingispresentalongthedirectionofthemicrofibersintimber,whilsthydrogenbondsisactiveinbetweenthemicrofibers.Thusitwillrequirelessforcetobreakthebondingbetweenthecellwallsiftheforceisappliedperpendiculartothefibredirectiontheniftheforceisappliedalongthegraindirection.
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Question2:Itisnotpossibletocomparemeaningfullythemagnitudesofthefailurestressesforthedifferentmaterials.Whyisthis?
Itisnotpossiblesincewoodcomesfromalivingorganism.Therewillbedifferentpropertiesofdifferentsamplesdependingonthespecifictreethatthespecificpieceoftimberoriginatesfrom,independentofwhatgrainangleitiscut.Thereforeseeminglyidenticaltestpiecescanhavedifferentproperties.Anumberofcontributingfactorswilldeterminetheindividualpropertiesofthetestedsamplessuchasdensity,knots,otherdefectsandgrowthrate.Alsowhenusedinconstructionandstructurestimberisusedindifferentsizes,temperaturesandenvironmentsthenthosepresentinthisexperiment.Thiswillhavevaryingeffectonthepropertiesofthematerialsused.Evenifweassumethatallthesamplestestedwereofequalmoisturecontentandstoredinthesameenvironmenttherearefactorsthatcanhaveanimpactonthepropertiesofthematerials.
Thedensityoftimbervariesnotonlybythemoisturecontentandtemperatureofthesamplebutcanalsobedependentontheamountoflatewoodandearlywoodinasample.Sincetreesgrowindifferentratesatdifferentstagesitaffectsthepropertiesofthewood.Strengthanddensitywillbelowestatthelowercenterofatreeandwillincreaseslightlyupwardsandoutwards(Desch&Dinwoodie1996).Theoriginofthetreewillalsoaffectthepropertiesofaspecificpieceoftimber.Twosamplesofidenticalsizethatarecutinthesameangletothegraincanhaveslightlydifferentpropertiesdependingonwhereonthetreetheyoriginatefromaswellasfromwhichtree.
Sinceknotsareanirregularityinthegrainandaffecttheangleofthegrainsitwillhaveanimpactonthestrengthofthematerial.Knotsvaryinsizeandcanoccuranywhereinapieceoftimberandtheeffectswillthereforevary.Iftheknotforinstanceispositionedontheedgeofapieceitwillhaveadifferentimpactonthepropertiesofthepiecethenifitispositionedinthecenterofthepiece.Itisthereforedifficulttoquantifytheeffectofknotsinspecificpiecesoftimber(Desch&Dinwoodie1996).
Thepropertiesofplywoodandchipboardalsodepend,inthesamewayastimberpieces,greatlyonthespecificpiecesoftimberusedandnotonlyonthepropertiesoftheadhesiveorresinused.Sincebothplywoodandchipboardiscomposedofdifferentpiecesoftimberofdifferentkind,factorssuchasknotsandirregularitiesindensityhaveasmallereffectonthemechanicalpropertiesofthesematerials.Butthepropertiesoftheusedtimberwillreflectonthepropertiesonthemanufacturedplywoodorchipboard.Youcouldintheorycalculatethestrengthpropertyofplywoodwithdetailedinformationofthetimberpiecesandadhesiveused.(Illston1995).
Sinceonlytwopiecesofeachgrainandcutanglewastesteditisnotpossibletodrawameaningfulconclusionsbasedonthetestsperformed.Andasseeninthegraphspresented
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earliertherearevaryingdifferencebetweenthetwosamplestested.Anumberoftimberpiecesfromdifferentoriginandsuppliersofthesamekindandstandardwouldhavebeennecessarytobetterindicatethevariationsofthesamekindsofwood.
Gradingoftimbernowadaysisdonewithstructuralsizedpiecesoftimbertobetterdeterminethepropertiesofdifferenttimbersinthewaytheywillperforminstructures.Thereforetheresultsintheexperimentwillbedifferentcomparedtostructuralsizedtesting.
Inadditiontomeasuringthetestsamplesitcouldhavebeeninterestingtoweighthemtodeterminethedensityoftheindividualsamplesofthesamegrainandcutangletoidentifyanydifferences.Ifalargeramountofsamples,orlargerpieces,wastestedandweighedperhapssomeabnormalitiescouldhavebeenidentifiedandmoreaccuratelyindicativeresultscouldhavebeenpresentedforthedifferentpiecesoftimber.
Question3:Comparethevariationinpropertiesfortimber,plywoodandchipboardandoutlinethesignificancefortheuseofthesematerials.Asstatedpreviously,wehavebeengiventimber,plywoodandchipboardsamplestotestthemintermsofcompressionresistance,andanalysethem.
Timberasanaturalsourcehasclearlyvisibledifferencesthanplywoodandchipboard.Asshowninthetable1,timbercutparalleltothegraincanwithstandmuchmoreload(average15,351N)andittakesmoreFailureload(average15,345N)thancutat45or90.ItsbeenfoundthattheTensileandCompressionstrengthsisreachingmaximumatparallelpositiontothegrain,andminimumatperpendicular.Tocomparethistotheplywoodandchipboardresults,Timberhasthebestcompressionresistancecutparalleltothegrainthananyofthematerialatdifferentangles.Totakethesefactorsunderconsideration,Timberishighlyanisotropic,whichmeanhasdifferentpropertiesindifferentdirections.
LookingattheTable4,whereplywoodresultsareaveraged,itcanbeassumedthatthismaterialcanbeslightlyanisotropic,whileitsmaximumloadisvisiblydecreasedwherethesampleswerecutat45,thanat0and90.
ComparingtheconclusionsabovetotheTable6,wherethechipboardresultsaretabulated,thismaterialisnotanisotropic,asithasthesamepropertiesindependentontheanglecut.
Beingatimberbasedmaterial,plywoodhastheabilitytoaccommodatetheoccasionalshorttermoverload;uptotwicethedesignload.Thismeans,thatwhenloadingisapplied
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forashortterm,anelasticresponseispresent.Longtermloadingcancausecreep,whichfollowonfailureofthematerial.
Particleboard isareconstitutedwoodpanelproductmanufacturedfromwoodparticles. Itcanalsobemanufacturedusingwoodflakesorstrands.
Amatof individualwoodparticles iscoated inadhesiveresinandpressedtogether intoafinishedpanel.Asthewoodfibresintheparticlesarerandomlyoriented,thefinishedpanelhasuniformpropertiesineachdirection.
Thismeans, that thepropertiesof thematerial,dependson its contents. Looking at thetable6,chipboardhassimilarmaximum loadand failure loadat thedifferentangles. It ispossibletogetthechipboardresistanttomoisture,ifadequateresinisusedtomanufacturethematerial.
Althoughtimbersmechanicalpropertiesarefixedbythegrowthcycle,plywoodandchipboardspropertiesarefixedbyresinbywhichtheywereglued,andwhichtimberpartstheyaremadeof.Examiningclosureanatureoftimer,betweenhardwoodsandsoftwoods,thereisadifferenceinstructure,butnotinmechanicalproperties.
Durability
Whileitisunlikelyincoolerenvironments,particleboardisstillsusceptibletofungiandtermites;howeveramoisturecontentofover18%wouldneedtobeachieved.Particleboardflooringisthemostcommonapplicationtoencountermoistconditionsandfungusresistantandtermiteresistantflooringisavailabletohelppreventdeterioration.
Particleboardwillperformsatisfactorilyinareasofhighhumidityandcanalsoaccommodatetheoccasionalwaterspillagebutitisnotdesignedtobecontinuallywet.
Particleboardshouldbeconditionedtohumidityleveloftheenvironmentitwillbeusedin,withanormalmoisturecontentrangeof1012%
Thedurabilityofplywoodwillinpartdependonthebondqualityusedinmanufacturing.Althoughtheuseofadurableadhesiveprovidesabondoflongtermeffectiveness,itdoesnotguaranteethattheveneersbeingbondedtogetherwillhaveanylongtermdurability.
Asstructuralplywoodismanufacturedfromarangeofhardwoodandsoftwoodspecies,itmaynotbedurableinexposedweathersituationssomustbetreatedwithpreservativetoensureitsfullservicelifecanbereached.
Uses
Plywoodisnotrecommendedforfullyexposedhorizontalapplicationslikedeckingbecauseseverecheckingcanoccur,butitisagoodsubstrateformembranesinthisapplication.Faceveneersarealsopronetocrackingifleftunprotectedinunsuitableweatherconditions.
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Doors,ExteriorStairs,ExternalCladding,Flooring,Framing,InteriorRailsandBalustrades,InteriorStairs,InternalPanelling,InternalPanelling,TimberJoineryProductsandTimberPortalFramesareexamplesofpotentialuses.
Timberisoneofthemostversatilematerialsforbothinternalandexternaluses.Whethermanufacturedfromsolidorengineeredtimber,therearemanyoptionsinfinishesthatwillnotcompromiseonstrengthandstructuralperformance.
Materialswhichwehavebeengiventotestandanalysearemostlyusedinnonforce,orlittleforceappliedobjects.Timberandtimberlikesuppliesareknownofitsstrength,durability,flexibilityandeasyworkability.HoweverChipboardismainlyusedasafloorboard,itisalsostrongandnaturalmaterial.
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Conclusion:Inconclusion,asdiscussedabove,timberishighlyanisotropic,duetoitsnaturalstructure.Itshowsgreatcompressivestrengthparalleltothegrainandleastperpendiculartothegrain.
Thefailurestressoftimberisinconclusivetocomparesince,evenifthepiecestestedderivedfromthesametree,eachindividualpieceofthetimberhastheirownpropertiessuchasgrainangle,cellstructureanddensityetc.allofthesefactorsaffectthestrengthofthetimber.Forthevarietiesofthecharacteristicoftimberitisusedwidelyinourlifesuchasstructuralbeams,flooring,furniture,frameetc.
Plywoodandchipboardaremanufacturedproducts.Plywoodisproducedbymeansofcrossbindingtimberveneers,thereforethecompressivestrengthparalleltothegrainandperpendiculartothegrainareapproximatelyequal.Thefailurestressdependsonthetypeofadhesiveusedandqualityoftheveneers.Itcanbeusedasconstructionstructurematerial,fordecorationorgeneralpurposeaccordingtothedifferenceofbondingperformance.
Chipboardhassimilarmaximumloadandfailureloadatthedifferentangles,asitisproducedbypressingthewoodparticlesbondedtogetherwithadhesiveandithasuniformpropertiesineachdirection.Thepropertiesofchipboardwillvarybecauseitdependsonthesizeofthechip,densityoftheboardandthetypeoftheresinused.Chipboardismostlyusedasflooringandforfurniturepurposes.
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References:DeschH.E.&DinwoodieJ.M.(1996)Timber,Structure,Properties,ConversionandUse,SeventhEd,London:Macmillan
IllstonJ.M.(1994)ConstructionMaterials,TheirNatureandBehavior,SecondEd,Suffolk:E&FSpon
Bibliography:FindlayW.P.K(1975)Timber,PropertiesandUses,London:CrosbyLockwoodstaples
MerrittF.RickettsJ.(2000)BuildingDesignandConstructionHandbookSixthEd,McGrawHill
WoodSolutions(2011)[online]Availablefrom:http://www.woodsolutions.com.au/WoodProductCategories/[Accessed10022012]
CA1youngs in progressTimber in progress)
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