45733395 Tension Test Report

8/13/2019 45733395 Tension Test Report

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T.C. ZMR INSTITUTE OF TECHNOLOGY

FACULTY OF ENGINEERING

DEPARTMENT OF MECHANICAL ENGINEERING

ME 409

Mechanical Engineering Laboratory

TENSION TEST

zge A.

2009, December !

ZMR

. Ob"ec#$%e

The objectives of this lab are:

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to perform tension tests on aluminum/steel to gain an appreciation of tensile

testing euipment an! proce!ures

to e"amine the resulting stress#strain curve to gain an appreciation of the

tensile behavior of the teste! material an! to i!entify/calculate the significant

mechanical properties of the teste! material

to compare the physical tensile#failure characteristics of the metal

. A&&'r'#()

$ 1%0 &' capacity electro#mechanically operate! universal tension/compression

loa! frame (ill be use! to test the tensile specimens) The applie! loa! on the

specimen is !etermine! in!irectly from a tensile loa! cell)

$ caliper (ill be use! to measure the !imensions of the test specimens)

The elongation of the loa!e! test specimen (ill be !etermine! in!irectly by

using an e"tensometer)

$ computer !ata#acuisition system (ill be use! to generate loa! an!!isplacement !ata)

. M'#er$'*)*0*+ $luminum or +04 stainless steel)

2. A+'*)$) - Re)(*#)E/CELTALESANDCALCULATIONS

T'b*e

Sample CodeGauge Length

(Go)Wo

(mm)to(mm) Wf(mm) tf(mm) Lf(mm)

Aluminum al-2 41,15

12,43 3,98 10,58 1,25

214,5

12,45 3,99 10,78 1,29

12,5 3,97 10,41 1,23

mean values 12,46 3,98 10,59 1,25667

Reduced section(f,mm)

au!e"en!t#

(f,mm)Ao

(mm2)Af

(mm2) e,ma$

100 50,56 49,5908 13,3081 92,9324

'. De#erm$+'#$-+ - #1e #e+)$*e )#re+#1 3 4(5The ultimate tensile strength ,-T. u is the ma"imum loa! sustaine! by the

specimen !ivi!e! by the original specimen cross#sectional area) $s can be easily

seen in 2igure 1 the ma"imum point of the Engineering stress#strain curve for $l

correspon!s to u399 M5a an! this is the ultimate tensile strength of $l)


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Figure 1 Engineering stress-strain curve of Al

F$(re 2 E+$+eer$+ )#re))6)#r'$+ c(r%e '+7 )#-8e %er)() e+$+eer$+ )#r'$+

b. C'*c(*'#$-+ - #1e m'$m(m *-'7 3Pm'5.u35ma"$099 M5a35ma"49%906 mm5ma"34*06%9 '

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c. C'*c(*'#$-+ - #1e M-7(*() - E*')#$c$# 3E5.7n the early ,lo( strain portion of the curve many materials obey 8oo&es la(

to a reasonable appro"imation so that stress is proportional to strain (ith the

constant of proportionality being the mo!ulus of elasticity or oungs mo!ulus

!enote! E:

e3E);e

Figure 3 calculation of modulus elasticityE!

$s can be seen in

7 specifie! t(o points on the elastic region (hich are not at either the top or

bottom an! these points are ,00011%< %04*== an! ,0000+=9=< 1*19%0) $lso 7

use e"cel to !ra( a linear line of these specifie! !ata region the line euation is y 3

41%9" # 01196 y is the engineering stress an! " is engineering strain) The slope ofthis line is >!" its value gives us the Mo!ulus of Elasticity E)

!y!"341%9

E341%9 M5a

2urthermore Mo!ulus of Elasticity E can be calculate! from the t(o specifie!

points from the relation given belo(

E31#;1#;

?ith this relation (e fin! a closer value of E that (as calculate! from the slope

of the line)

E31#;1#;3%04*==#1*19%000011%#0000+=9=

E3410+0 M5a

7 thin& the first metho! is more reliable because the line inclu!es much more

than t(o !ata points)

@0#strainA location on the strain a"is is the " value (hen y30 in the euation of line

y 3 41%9" # 01196)

7f y300 3 41%9" # 01196

"364B10#* is the @0#strainA location)

7. De#erm$+'#$-+:c'*c(*'#$-+ - #1e $e*7 )#re+#1, 4Y, -r A*2or most engineering materials the curve (ill have an initial linear elastic

region as in 2igure 4in (hich !eformation is reversible an! time in!epen!ent) The

slope in this region is oungs mo!ulus E) -nloa!ing the specimen at point C in

2igure 4the portion CC D is linear an! is essentially parallel to the original line C A)

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The horiFontal !istance C D is calle! the permanent set correspon!ing to the stress

at C) This is the basis for the construction of the arbitrary yiel! strength) To

!etermine the yiel! strength a straight line CC @ is !ra(n parallel to the initial elastic

line C but !isplace! from it by an arbitrary value of permanent strain) The

permanent strain commonly use! is 0)0 percent of the original gage length) The

intersection of this line (ith the curve !etermines the stress value calle! the yiel!

strength) 7n reporting the yiel! strength the amount of permanent set shoul! be

specifie!) The arbitrary yiel! strength is use! especially for those materials not

e"hibiting a natural yiel! point such as nonferrous metals< but it is not limite! to

these) 5lastic behavior is some(hat time#!epen!ent particularly at high

temperatures) $lso at high temperatures a small amount of time#!epen!ent

reversible strain may be !etectable in!icative of anelastic behavior)

Figure " #eneral Stress- Strain $iagram

0.2; OFFSETMETHOD

Figure % &ield Strengt'

$s can be easily seen from 2igure %the iel! .trength y 3=4 M5a )

The stress#strain curve !oes not remain linear all the (ay to the yiel! point)

The proportional elastic limit ,5EL sho(n in 2igure 4is the point (here the curve

starts to !eviate from a straight line) The elastic limit ,freuently in!istinguishable

from 5EL can be seen in 2igure 4is the point on the curve beyon! (hich plastic

!eformation is present after release of the loa!) 7f the stress is increase! further the

stress#strain curve !eparts more an! more from the straight line) This curve is typical

of that of many !uctile metals li&e $l that (e use! in our e"periment)

e. C'*c(*'#$-+ - #1e &erce+# re7(c#$-+ - 're', ;RA

The GH$ is given by

GH$3100)$0#$f$0

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GH$3100)49%906#1++06149%906

GH$3=+=G

. S8e#c1 - #1e r'c#(re )(r'ce) - 7(c#$*e m'#er$'*)

As can be seen in 2igure *,it shows the macroscopic differences between two ductile specimens (a,b)

and the brittle specimen (c).

Figure ( fracture mec'anisms

Figure ) se*uence and events in nec+ing and fracture of a tensile test s,ecimen .a/ early stage of nec+ing0 ./ small voidsegin to form 2it'in t'e nec+ed region0 .c/ voids coalesce ,roducing an internal crac+0 .d/ rest of cross section egins fail

at t'e ,eri,'ery y s'earing0 .e/ final fracture surfaces +no2n cu, and cone fracture!

On the microscopic level, ductile fracture surfaces also appear rough and irregular. The

surface consists of many microvoids and dimples.2igure 6and 2igure 9demonstrate the

microscopic qualities of ductile fracture surfaces.

Figure ductile fracture surfaces

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Figure 4ductile fracture surfaces

=

45733395 Tension Test Report

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