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OTS index dtd Jun 1947
T Nt\TION�.L DE:FENSE RESE.J;RCH co: JITTTEE
of
OFFICE OF SCIENTIFIC RESEJJWH . ."1-JD DEVELOPfiE, T
\7.tR :..LET •• LLURGY DIVISION
Progress Report
on
PLnSTIC FLO\! OF ;,r,ur::nm .. ... D1CFl.i'.FT
SHE�T UNDER COi: BIN3:D LO;..Ds-II (Ni.-150)
by
JOHN R. LO\:, JR. JUJD T . ... PR.i.'I'J� PEl'nTSl'LV"Nii. S'f,.,TE COLLEGE
OSRD No. 3 53 Serit.l No. M:-249
DISTRI.Bl!flf?N STATEMENT E: DlstrrbutJon authorized to DoD Components only.
Other requests shall be referred t9:
Best Available Copy Thill document contains information affectin&"
the national defense of the Unit t t within
ct. u. s. c.
of its contents in ny manner to n
person is prohibited by w.
ffNIOAL INFOR OR :VA C, E. , ATION BRANCH
I r:. D '
. CH C EN 'T' r:nR n ' N p_.. )VIN'• � OJ •
'1 G OUND AR ';A D
To: Dr. James B. Conant, Chairman
RESTR CTED
1�pril 19, 1944
National Defense Research Committee of the Office of Scientific Rcsc�rch and Development
From: War Metallurgy Division (Div. 18), NDHC
Subject: Progress Report on 11Plastic Flow of Aluminum i�ircrr.ft Sheet Under Combined Loads-II11 (N,i-150)
I The attached progress report submitted by John R. Low, Jr. ,
Technical Representative on NDRC Research Project NRC-52, has boon approved by represent<:.tives of the War Metallurgy Committee in charee of tho work.
This report describes the results of a stuGy of the effect of specimen size (length and width) on the limiting elongation v�lues in tension and the distribution of these vr�lues as a function of gage length for 0.04011 Alclad 24-SO sheet.
I recommend acceptance as a satisfactory progress report under Contract OEMsr-864 with Pennsylvania State College.
��ncl osure
RESTRICTED
·Respectfully submitted,
<" ( ' -'L(\.'(\n . ' ·- � lZP v J...XYJ.-. CU..J....C...-f'
Clyde Vflllinms, Chief ·
\''iar M:etallurgy Division, NDRC
DISTRIBUTION STATEMENT E: Distribution authorized to
DoD Components only. Other requests shall be referred to:
•
RESTR CTED
This report is pertinent to the problems designated by the Office of the Coordinatbr of Research and Development, Navy Departntent, as NA-150, and to the project designated by �he Vla.r >1etallurg;y• Committee as Nr:RC Research Project NRC·-52 •
The distribution of this report ·is as follows:
Copies No. 1 thru 30 - Dr. Irvin Stewart, ·Executive Secretary, OSRD Copy No. 31- Clyde lilliams, Chief, 1far Metallurgy Division (Div. 18), NDRC
and Chairman, VIar �/etallurgy Committee Copy No. 32 - Office of the Executive Secretary, War Metallurgy Comrn.::..ttee Copy No. 33 - V. H. Schnee, Chairman, Products Research Division,
War , Metallurgy Commit tee ·
Copy No. 34 - R. C. ToDnan, Chairman, Sub-Comnittee for· Division 18, ND�C Copy No. 35 ... Roger A:dams, Member Sub-Committee for Division 18, NDUC Copy No. 36 - J. E. Jackson;· ·Staff ·Aide for Division 18, NDRC Copies No. 37 thru 39 - Har Department Liaison Officer with NDRC
.He<\_dque..rters,. Aimy- Service Forces Copies No. 40 thru 53 - Army Air Forces, Commanding General, Wright Field
·Attn: Inspection Division, Materials & Processes Branch Copy No. 54 - Army Air Forces Board, Orlando, Florida. Attn: Secretary of Board Copy No. 55 - Army Service Forces, Commanding General, Watertown Arsenal
Attn: Colonel H. H. Zornig, Director of Laboratories Copy No. 56 -G. W, Lewis, Director of Aeronautical Research
National Advisory Oommittee for Aeronautics Copy No. 57 - Navy Department', .Bureau of Aeronautics
Attn: Lt� Comdr. Wm. P. Goepfert, Project Liaison Officer. Copy No. 53- J. E. Darn, Technical Representative, NDRC nesearch Project,NRC-h4 Copy No. 59 - John R. Low, Jr.,Technical Representative, NDRC Research Project NRC-52 Copy No. 60 - T. A. Prater, Investigator, NDRC Research Project NJC-5�
Members of the Project Committee
Copy No. 61 - L. L. Wyman, Chairman· Copy No. 62 - E. H. Dix, Jr. Copy No. 63 - E. S. Jenkins
CopJ No. 64 -George Sachs Copy No. 65 F. R. Shanley
Members of the Project Committee NDRC Research Project NaC-43
Copy No. 61 - L. L. Wyman, Chairman Copy No. 66 � Capt. J� P. Awlerter Copy No. 67 - R. Bateman· Copy No. 68 - J. L. B�nnett Copy No. 6'9 - M. Gensa.mer Copy No. 57 -Lt. Comdr. Wm. P. Goepfert Copy No. 70 - R. B. Gray Copy No. 63 - E. S� Jenkins
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Copy No. 71- J. B. Johnson Copy No. 72 - V. N. Krivobok Copy No. 73 - Major B. C. l�ddcn Copy No. 74 - C. F. Nagel Copy No. 75 - Ensign G. 1\f� Onken Copy No. 76 - T, E. Piper Copy· No .• ·77 - A. B. Richards
· Copy No. 7 8 - Lt. B. Rubinstein Copy·No. 79 -Major E. H. Schwartz Copy No, 80 - 0. A. Wheelan
Members of the F.ngincering Conunittee J.ircraft War Production Council, Inc.
Copy No. 81- Boeing ld.rcru.ft Company, Vi. E. Beall 'Copy N-o� 82 - Consolidu.ted- Vultoe hircruft Corp. , Vultee Field Div. , J •• P. Fontaine Copy No. 83 - Db.uglas. J.j.rcraft Company, Inc., : •• E. Raymonq. Copy No. 84- Lo.ckhee d Aircraft Corp., Factory rr;.rr, Mac '.Shor.t·. Copy No. 85 -North American Aviation; Inc. , Gordon Throne Copy No. 86 - Northrop 1\ircraft, Inc. , R. A. D1:1t ton Copy No. 8? - Ryan Aeronautical Company, B. T. Salmon, Chairman
. . . ·· Members. of the Plant Production Section
.Aircraft War Production Ccnincil·� Inc.
Copy No. 8 8 - B.oeing. Aircraft Company, H. o .• vV,es� , ,
Copy No. 89 - Consolidated- Vultee Aircraft GQ!P•, San qi�.�o Div. , H. Bowling Copy No. 90 r Lockh€le d !dpcraft Corp. ,. Fact.ory ":•", ·George H. Prudden Copy No. 91 - ·NQ!'th American l.viation, Inc •. , R • .
E. Dawe Copy No. 92 - Northrop Aircraft, Inc. , Paul .. Buckner ·
Copy No. 93 - Ry�n i:>eronautical Company,. G. E • . �arto·n ,,
. .
. . ··
Members of the Test.ing and. ��
·se
.;irch Panel
1\ircraft War Production Council, Inc •
Copy No •. ·8!1... .- Boeing Aircraft. Company:, V¢. E .• ' Beall Copy No. 94 � �onsQlidated-Vultee Aircraft Corp. ; Vultee F{eld Div. , Harold Boyvey Copy No. 95 - Douglas· Aircraft. Compa�y; Inc.,'. J,,.· B.. Go.ldstein Copy No. 80 - Lockheed Aircraft. -CorP;, , Factory . "B.'', F .• R. Shanley Copy No. 96 - North American .h,.viaticm,. Inc. , L,.. P •
. ppa�ding
Cop-.f No• 73 - .Northrop; J�ircraft, Inc.; �. :E!. Pipe� Copy No. 97 - Ryan Aeronautical· .Comp�ny 1 .. J. C • . Scurlock
� .
Copy No. 9 8 - Aircraft :War Produc·tion Council, .. Jam�s L� Straight Copy No. 99 - Consolidated- Vultee Aircraft Corporation, James Kelley Copy No. 100 - Gurtiss- Wr,ight Corporation, G. H. Cartledge Copy No • . lOl - Curtiss-Wright Corporation, C. C. ·FUr-ncis Copy No. 102- Douglas Aircraft Company, Incorporated, j. C. Buckwalter Copy No. 103 - Douglas J.ircraft Company; Incorporated, ·E . F. Burton Copy No. 104 - Douglas Aircraft Company,. Incorporated, L. l •• Carter Copy No. 105 - Douglas .h.ircraft G.ompa.ny; Incorporated, F. Vi. Conant Copy No. 106 - Douglas Aircraft Company, Incorporated; D. E. Dunlap Copy No. 107 - Douglas .k.ircr�ft Company; Incorporated,. E. H -. � Heinemann Copy No. 108 - Douglq.s h.irc·rt:J.ft Company, Incorp()rated:, .F . . Vi • • Herman Copy No. 109 - Douglas l�.ircrq.�.t Company; Incorporated; J. M, Sc�uma,nn Copy No. 110- Douglas Aircraft Company, Incorporated, . M. G. Simpson Copy No. 111 - General Electric Company, D. Basch Copy No. 112 - Harvard Unive�s:i.ty, P. W. Bridgman . .
Copy No. 113 -..Lockheed 1\irc�aft Corp. , Factory riB", L. H. P<;>tter i.J,F Materiel & Process Unit Representative
•
RESTRI CTED
Copy No. 114 -Northrop Aircraft, Inc., R. R. Nolan . Copy No. 115 - War Production Board, Industrial Processes Branch, Office of
Production Research and Development, Maurice Nelles Copy No. 116 -Copy No. 117 -Copy Nq. 11 8 -
Copy No. 119 -Copy No. 120 -Copy No. 121 -Copy No. 122 -
copy No . 123 -
Copy No. 124 -
Copy No. 125 -
Copy No. 126 -Copy No. 127 -Copy No. 12 8 -Copy No. 129 -Copy No. 130 -Copy No. 131 -
Copy No. 132 -Copy No. 133 -
Copy No. 134 -Copy No. 135 -Copy No. 136 -Copy No. 137 -
Copy No. 13 8 -
Copy No. 139 -Copy No. 140 -
Copy No� 141 -Copy No. 142 -
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Copy No. 145 -Copy No. 146 -Copy No. 147 -Copy No. 14 8 -
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Total number of copies - 150
FOURTH QUARTERLY
PROGRESS REPORT
N.D.R.C. Research r.roject NRC-52
RESTR CTED
Contract No. OEMsr B64
PLASTIC FLm�' OF ALUMINUM AIRCRAFT
SHEET UNDER COM3INSD LOADS-II
November 1, 1943 to February 1, 1944
From: Department of Metallurgy, The Pennsylvania State Col1e�c
Report prepared by: John �. Low, Jr. T. A. Prater
RESTR'ICTED
•
FOURTH QUARTERLY
PROGRESS REPORT
N. D. R. C. Research Project NRC-52 Contract No. OE sr R64
PLASTIC FLOW OF ALUMINUM AIRCRAFT
SHEET UNDER COMBINED LOADS-II
November 1, 1943 to February 1, 1944
From: Department of Metallurgy, The Pennsylvania State College
Report prepared by: John R. Low, Jr. T. A. Prater
ABSTRACT
This report describes the results of A study of the effect
of specimen size (length and width) on the limiting elongation
values in tension and their distribution as a �unction of gage
length for 0.04011 Alclad 24-SO sheet. On the basis of these
results it is proposed to confine future tests on othPr grades
and tempers to two modified tension specimens and the standard
A. S. T. M. sheet specimen. One of the modified tension specimens
will be of sufficient length ( 1211 ) so that the uniform as rell
as the local elongation may be determined. The othor will be
a wide specimen with curved edges so designed as to limit
lateral contraction to a minimum during stretchi ng in the
tension direction.
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•
RESTRI CTED
FOURTH C'UARTERLY
PROGRESS REPORT
N.D.R.C. Research Project NRC-52 Contract No. OEMsr 864
PLASTIC FLO\�r OF ALU.,UNU�.[ AIRCRAFT
�HEET UNDER COMBINED LOADS-II
November 1, 19�3 to February 1, 1944
Fro�: Department of Metallurgy, T�e Pennsylvania State Colle�e
Report prepared by: John R. Low, Jr. T. A. Prater
CONTENTS
P ge
I. Introduction................................... 1
II. Experimental Procedure......................... 2
Specimen Preparation......................... 2
Gripping and Alignment .. · . . . . . . . . . . . . • . . . . . . . . 2
Material ............... . .. . .. . ....... o • • • � . . . 3
III. Effect of Specimen Size........................ 3
Table I. Effect of Specimen Dimensions on Elongation and Lateral Contrection.. 6
Fig. I. Method of Determining Length in Simple Tension from Lateral Contraction Measurements ........... .
Fi�. II. Effect of Specimen Dimensions on Fraction of Reduced Area in Simple
5
Tension ..... . . . ..... . . . .... G • • • • • • • • 7
Fig. III. Effect of 3iaxial Stress Condition in Plane of the Specimen on Elongation to Fracture............. 9
Fig. IV. Effect of Specimen !idth on Local Elongation near Fracture............ 10
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IV.
v.
VI.
Summary . ... ..... . ' • o o • a • • • ., • • .. • � • • • • • • • • • • • • •
Plans for Future Work . . . . . . . . . . . . • . . . • • . . . . . • .
References . . . . . . . . . . . . . . . . a • • • • • • • • • • • • • • • • • • •
Page
11
12
13
•
RESTRI CTED
FOURTH 0UARTERLY
PROGl\ESS REPORT
N.D.R.C • . Rese�rch Project NRC-52 Contract No. OEMsr _64
PLASTIC FLOW OF ALUMINIDA AIRCRAFT
SHEET UNDER COMBINED LOADS-II
November 1, 1943 to February l, 1944
From: Department of Metallurgy, The Pennsylvania Sta.te College
Report prepared by: John R. Low, Jr. T. A. Prater
I. Introduction
T�e purpose of the present investigation is to determine the
plastic behavior of aluminum aircraft sheets for various combinations
of the principal strains in the plane of the sheet. As a part of
this testing program it is necessary to know the effect of
specimen size and shape on the amount of flow which precedes
fracture·in the simple tension test. The results of such a study
will, for example, indicate to what extent ductility values
obtained from a standard sheet tensill. s�ecimen are represent�tive
of those to be expected in stretching sheets of larger dimensions.
Further, the present investigation provides information on the
manner in which the elongation vs. gage length curves are changed
when the deformation is confined to short gage lengths under
conditions of severe lateral restraint.
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"tti
II. Experimental Procedure
Specimen Preparation:
2
The specimens us2d in the investigation varied in width from
�" to 10" and in gage length ·from 111 to 1 2 11, giving length/width
ratios ranging from 0.10 to 17. The edges of the specimen were
milled oarallel and any burrs resulting from this step -vvere
removed with a sharp.$C�aper .. No filing or polishing of the
specimen edges was done. A 100 line per inch grid was then
printed on each specimen employing the 11photo-grid11 technique.
The grid obtained by this process was accurate within �4-.0� over a gage length of 0.01"; �l.O%over a 0.05" gage; and �0.2% over
a 1.011 gage.
Gripping and Alignment:
In some of the tests simple rectan�ular specimens '"i th no
reduced section were employed. Although four different m�thods
of gripping the specimen were tried, it was found that in most
instances specimens of this design fractured in or very close to
the front edge of the grip. Later specimens were milled with a
fillet of 1�-11 radius and e.. shoulder t" ��rider than the gage section
(Fig. 1) • This design proved satisfactory for specimens not
exceeding 511 in width, but for the wider specimens it ·was necessary
to increase the fillet radius to 3" and the shoulder width to l"
greater than the gage section to ensure a fracture within the
section of reduced *idth. All data reoorted are taken from
. .
•
RESTR CTED
3
specimens with a reduced section except where otherwise designated.
The specimens �11 wide were gripped in Te'Tlplin sheet grips
which were held in modified.Robertson shackles. Each was care-
fully'aligned by placing·l'' �age length Tuckerman optical exten
someters on either side of the specimen and .shifting the grips until
the elongation on each side was the same for any given change in
load. The wider specimens were gripped between files and ali_ned
by keeping the specimen_edges perpendicular to the front edges of
the two sets of gripping files. Before testing the distance
between the two sets of. j�ws was .measured at the two ed�es of the
specimen to further check the alignment.
Material:
All of the results herein described apnly to 0.040" Alclad
248-0 sheet �ested in the rolling direction.
III. Effect of Specimen Size
� Photo-elastic studies (l) show that the portion of a tensile
test specimen which is not in simple tension varies ,ri th spE:>cirnen
width and radius of fillet. Dorn and Finch ( 2) , in th8ir 'ork on
magnesium alloys, have found that, if the radius of the fillet is
k�pt equal to the width of the gage section, the portion of the
test specimen not in simple tension extends from the fillet into
the reduced section to a . distance approximately equal to the
specimen idth. In the present tests, the portion of the test
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4
specimen in simple tension ��s taken as that section �hich had a
uniform percentage of lateral contrc?ction. The extent of this
section was determinsd after the completion of the test by
measuring the lateral contraction over a 0. 211 ga.ge length along
the center line of the specimen at convenient intervals. The pr::r-
cent contraction at each point was then calculated from the
-w
o - wf relationship: % contr. - W x 100 where W0 = 0.2n, and
0
Wf
= distance across 20 grid sauares after test. These values
were then plotted against their positions along the gage section
(Fig. 1) and the length with uniform lateral contraction determined
graphically. The percent uniform lateral contraction appears to
be independent of specimen width and varies between 5.0% -and 6.5%. (Table I) It appears that the only effect of snecimen width on
lateral contraction is that the narrower specimens sho ' some
lateral necking in the immediate vicinity of frocture thus prou1cing
greater elongations (and contractions ) over short ga�e lengths near
the fracture. Curve 11blf in Fig. l has been drawn for a specimen
that shows a uniform lateral contr.s.ction lower than that found to
be representative of a condition of simple tension. This "behavj_or
was also exhibited by a specimen 1011 wide with a 111 gage length.
It appears the.t these specirnens are of such shape and dimensions
that equal lateral stresses are set up over an appreciable gage
length resulting in a section of uniform lateral contrPction
although none of the specimen is in simple tension.
� t),. � � <:S
'I
p
·� � '-6
I �
§ .:.;:;:
....
-� _1_
t . t - ---r--L r
00 a, -
/ �� I <r
( . .,. �t/ �_h "o
'fjc!J"
., ---'.---t:-
-0 t•
0 c v
•
..L if. A/clad 24S-O a 2.511 4 75.
0040" Sheel h 2.0 5.0 (no fillels) c 4.5 2.0 d 4.5 �.15
. e IO.S IQO ( R=3'l
0 'n 0-.
/n - '-.n
y/ / ( u
""·
d cV � g
� �i/ If �I\. c:: <3 � � .� '-J
'
s
t
� 2
� � 0 � � �
y·
=H-
�r 0 cb
/ ( � �) I '-englh. in sim p/e len >ion J � r I
e 1+-/ , ---+-. ----
Dis lance along cenfer line Fig. 1 Me/hod of delermining /englh in simple lension from
/a/era/ conlraclion measurernenls
�
\It
m
a
� b
RESTRI CTED
6
TABLE I.
Effect of Specimen DimPnsions on Elong·- tion and
Specimen Dimensions
(inches) L W
2�· 1 2
4� _)" 2
12 � 4
4Q 2
2"� 4�
4� 4i
10-:1. :2 10
Laternl Contraction· ; Uniform Lnteral Elongation Lateral Contre.ction for Zero Contraction at Fracture Ga(e Lenyth
(in/in) (in/in) in/in
.059 . 101 1. 1 1
.059 .076 1.18
.050 .106 1.35
.062 .064 1.52
.056 .057 1.21
.065 .066 1.1 1
.053 .053 1 . .33
All values refer to region in simple tension.
The percentage of the gage section with uniform
Limiting Uniform
Elon�ation (in in)
.165
.159
.160
.198
. 195
.180
.165
lcteral
contraction, i.e., in simple tension, has been pl�tted against
the ratio: L/W, where L = the l�ngth between fillets and W == the
gage width, (cf. Fig. 2). It is seen from this plot thC;t for
the design specimens used in this investigation the length of
the reduced sectiJn must be �t least one-half as gr�at es its
width or there will be no SPcti�n in simple tensi,n. The
fraction in simple tensi�n increased rapidly �s 1/W is incrc�sed
until that ratio reaches a value of Appr�ximRtely 2 after vhich
the increase is c�mparatively sl�w.
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•
•
RESTRICTED
0
�-------
� I --Q: � 1-.--
I . , �
�M-. � 0 ......J cu
a ....... I . � y, cu cu cu I � � I �C\J "b
� I <:::) ,,f-1 � � � � 1-L-(..) .......... j \ � C) �--- -----
-""
� � .... e <=>· li
8 � dU,17 't3Jd/Ud[) �UOfD � 8
7
UO.JFJDJ/UOD fDJaiD7 WJOj,IUn 1.{/.IM 7 JO UO.JI�DJ..:f RESTRICTED
RESTRICTED
8
In Figure 3 elongation hQs been plotted as 8 function of
gage len�th for six specimens. In three of these the entire
length covered by the curves is in simple tension, 8nd in the other
three there is no region in which that condition exists. The
curves fall into two distinct groups with the specimens in simple .
tension exhibiting the greater elongRtion. This effect is most
marked for gage lengths under one to one and one-half inches.
From these curves it is observed th�t elongation to fracture is
not affected by specimen width provided the specimen length is
great enough to permit a state of simple tension. The only
exception to this is a slight lowering of the elongation-gage
length curve in the rBgion of short gage lengths in the cese nf
wide specimens. This minor variati,n is due to the lateral
necking which occurs in the narrower specimens, but is not observed
in those exceeding 211 in width. While the el�ngati�n �v9r
zer: gage length does not seem to be a functinn :)f ·width, the
el0ngation over c�mparatively short gage lengths (i.e., . 05 11 t0
.5011) is increased in the narrower s ecimens because 'If' the
greater gage l8ngth affected by the neck. As sh��n in Fi . 4
this regi0n extends f0r approxirna.tely 1�11 in the �" snecimen
and f-::>r Jnly abc)ut !" in the 1011 specimen.
RESTRI-CTED
� rn (I} � � r;1 �
� .s
14
I 12
I 10
�08 . c::: �
c::: �06 C) � Q llJ 04
I 02
�. �
p
�
'l � � h-
4
I I A/clad 245-0 0040'' Sheel BlilS
000
. !laA
• • •
• • •
• • •
simp) lens ion ':\ -
• - • - • ...
- -� QO" o, ,-gage Venglh ' n simple lens;or,
0 02 04 Q6 08 10 12 14 Gage Lenglh (.;nc hes)
•
I I lf L
I# II
� 4� .J. 1/
*' 12�" 10" !012
,,
10'' I " I� •
10'' 2Jf''
10" I. II 4J2
r.. "" � - a -
.
16 ·/8 20
Effecl of biaxial slress c ondilion tn lhe plane of ff1e spec imen on e l ongalion lo fraclure
Fig. 3
i i i
i I I I I I
I
-
� l'rJ
2." VJ .L � � � ..0
� v
:., � � � � ni �
A/clad 245-0 0040" Sheel
021 �. I I � I\.. ·I . I I L'.. I I I I ' I I Q
roc lure ,,
� wide specimen 12'' long
10" wide specimen tO" long
�Dis lanc e along Cenler Line of Specimen--.
Fig. 4 Ef fecl of specimen wid lh on local elongalion near fi-aclure
•
b
�
� � til \j·
RESTRI CTED
11 IV. SummEry
It has been Lmnd thc-t lateral c··ntre.ctirm measured at
intervals along the spEcimen center line parallel to the
direction of loading is a sensitive measure ·or stress conditions
in the plane of the sheet end can be used to determine the
actual length in · p�re tension, that is; the length of the
specimen �thich is not affected by the fillets or grips.
Within the region of simple tension neither the lateral
contraction nb� the elongation to fr�cture appear to be atfected
by increasing the specimen width or length except that fo-r very
narrow specimens ( less than 2" wide) some lateral necking occurs.
As a result the elongation values �easured in the immediate
vicinity of fracture ( i. e. , over short �age len�ths) are
slightly higher th2n those obtained with wide specimens.
The frection of the specimen length in simple tension may
be plotted as a function of the ratio:· length/width. · When
this is done it is found thet for the 0.04" thick sheets beintS
tested and the particular shape used, this fraction begins to
decrease rapidly as L/W decreases below 2.0 a.nd becomes zero·
in the vicinity of L/W : 0. 5. As the ·fraction of the length
in simple tension decreases the curve for elongation vs . gage
length is·shifted to lower elongatiqn values�
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I·
12
The above observ2 tions e.re bnsed on tests on Alcl:>.d 248-0
specimens 0.0411. thick o.nd vc.rying ·in length from one to twelve
inches and in width from one-half to ten inches.
V. Plans for Future Work
On the basis of these results it is proposed to standardi�e
on two tests in the future: one, a tension test on a specimen
of sufficient length to obtain simple tension conditions over
I
sufficiently long gage lengths to be Qble to evaluate the uniform
elongation (i.e., infinite gage length) as well as the elongation
values for shorter gage lengths; the other, a tension test using
a wide sp�cimen with curved edges ( cf. Third Quarterly Progress
Report) . so d�signed as to l1mit the lateral contraction to a
very small value approaching zero. .
These two tests togethar with the elliptical and spherical
bulge tests of NRC-51 at The Carnegie Institute of Technology
will make it possible to obtain elongation values for a large
variety of combinations of the principal strains. 'I'ests are.
to be in·ade in both the rolling and transverse directions and
in sufficient number to indicate the ra.nge of scatter which
may.be expected.
At the present time 0.04" sheets are on hand in the following
grades: Alclad 248-0, 248-T, and 24SR-T. OthPr alloys and
te�pers are to be included in the testing program as soon as
sheets can be obtained for testing.
•
.
'
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VI. References
l) E. G. Coker and L. N. G. Filon: Photo-elasticity,
Cambridge University Press 1931, pp. 560-578.
2) J. E. Dorn and D. M. Finch: Finel Report on
"Properties and Hea.t Treatment of .MR.�?;nesium Alloys:
Part I The Effect of Size upon Tensile Properties
of Specimens of Magnesium Alloy Sheet" (NA-144).
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