UNCLASSIFIED

AD NUMBER

AD092961

NEW LIMITATION CHANGE

TOApproved for public release, distributionunlimited

FROMDistribution authorized to U.S. Gov't.agencies and their contractors;Administrative/Operational Use; JAN 1956.Other requests shall be referred to AirForce Aeronautical Systems Division,Wright-Patterson AFB, OH 45433.

AUTHORITY

afal ltr, 27 dec 1979

THIS PAGE IS UNCLASSIFIED

UNCLASSIFIIED

armed Services Technical nformat :ionllgencyReproduced by

DOCUMENT SERVICE CENT ERKNOTT BUILDING, DAYTON, 2, OHIONI

This document is the property of the United SLates Government. It is 1 furnished for the du-ration of the contract and shall be returned when no longer required, or toapon recall by ASTIAto the following address: Armed Services Technical Infor'rmatlon Agency,Document Service Center, Knott Building, Dayton 2, Ohio.

NOTICE: WHEN GOVERNMENT OR OTHER DRAWINGS, SPECIFICATION4S OR OTHER DATAMWMUD FOR ANY PURPOSE OTHER THAN INGVRMN CRCRMN OEAIN ONNECTION WITH A DE 3FFIN1TELY RELATED)NO RESPNSBIT, P NRu REN OPERATION, THE U. S. GOVERNMENT fTEIEREBY INCURASNO RESPONSNBIL Yr NOR ANY OBLIGATION WHATSOEVER; AND THE A -FACT THAT TH AGOVENBM'r MAY HAVE FORMULATED, FURNISHED, OR IN ANY WA16M SUPPLIED THESAI'D DRAWINGS, SPECIFICATIONS, OR OTHER DATA IS NOT TO BE RE( WARDED BYI MPLICATION OR OIDHERWISE AS IN ANY MANNER LICENSING THE HOO iDER OR -ANY OTHERPERSON OR CORPORATION, OR CONVEYING ANY RIGHTS OR PERMISSI#X ON TO MANUFACTURE,

USE OR SELL ANY PATENTED) INVENTION THLAT MAY I N A E RLTDTEEO

N C A A IN ANY WAY BE RELATED THERETO.i.-U.NCLjASSIFI ED

WADC TECHNICAL REPORT 54-391

\kaPPLEMENT 1

INVESTIGATION ON NOTCH SENSITIVITY OFHEAT-RESISTANT ALLOYS AT ELEVATED TEMPERATURES

Supplement 1 - Apparent Volume Increase Due to Triaxial Stresses

CAPT. W. E. DIRKES

MATERIALS LABORATORY

JANUARY 1956

WRIGHT AIR DEVELOPMENT CENTER

WADC TECHNICAL REPORT 54-391

SUPPLEMENT 1

INVESTIGATION ON NOTCH SENSITIVITY OF

HEAT-RESISTANT ALLOYS AT ELEVATED TEMPERATURESSupplement 1 - Apparent Volume Increase Due to Triaxial Stresses

-CAPT. W. E. DIRKES

MATERIALS LABORATORY

JANUARY 1956

PROJECT No. 7360

WRIGHT AIR DEVELOPMENT CENTER

AIR RESEARCH AND DEVELOPMENT COMMANDUNITED STATES AIR FORCE

WRIGHT-PATTERSON AIR FORCE BASE, OHIO

rr 'ntP.r .ithn Frtc' %00 - ' nrtl l C,6

FOREWORD

This report was prepared by the Metals Branch and was initiatedunder Project No. 7360, 'Materials Analysis and Evaluation Techniques".Task No. 73605, 'Design and Evaluation Data for Structural Metals'.formerly RDO No. 605-227 sR-3a, wHigh Temperature Alloys', and wasadministered under the direction of the Materials Laboratory, Directorateof Research, Wright Air Development Center, with Capt. W. E. Dirkes actingas project engineer.

This report covers period of work from July 1954 to November 1954.

WADO TR 54-391Supplement 1

ABSTRACT

The volume of structural metals is generally considered to remainconstant even with extremely high stresses applied. Some data recentlypublished indicate significant changes in volume under stress-rupturetest conditions for specimens having stres gradients. More recent analysisof the same data and specimens together with additional measurements fromthese specimens show that significant volume changes did not actuallyoccur, but that plane cross-sections of specimens did not always remainplane when subjected to stress gradients.

PUBLICATION REVIEW

This report has been reviewed and is approved.

FOR THE COM44ANDE~s

M. R. WHITMORETechnical DirectorMateria 1s LaboratoryDirectorate of Research

WADC TR 54-391Supplement 1 iii

TABLE 0F CONTENTS

Page

I1 PURPOSE . . . . . .... . . . . ...... . • a • • * • 1

II. GENERAL CONSIDERATIONS .. .. .... . . . . . . . . . 1

III. FACTUAL DATA . .... . . . . . . . . . . . . 1

IV. COCUSIONS • . . . . . . ..3... .. . . .

LIST OF TABLES

TABLE

I. APPARENT VOWME OhANGE IN NOTCHED STRESS-RUPTUBESPXDIMES o. . .- a,. . .. . .o - . 4

LIST OF FIGURES

FIGURE

1 Undeformed and Deformed Notch Contours for 0.010Inch Radius Notch . . . .. . . • .. . . . . . • * • * • .5

2 Stress Versus Rupture-Time Curves for Plain andNotched Bars of S-816 Alloy .......... .... . 6

3 Stress Versus Rupture Time for Inconel 'X9 Type550 Alloy at 1350 F . . . . . . . . . . . . . . . . 7

4 Stress Versus Rupture Time for Inconel OXI Type550 Alloy at 16oo F . . . . . . . . . . . . . . . . .. . 8

5 Change of Shape of Plane Cross-Sections as Indicated byDeformation of Scribed Lines .......... .. . 9

WADC TR 54-391 ivSupplement 1

INVESTIGATION ON NOTCH SENSITIVITY OHEAT-RESISTANT ALLOYS ;T =VATED T EPERATURES

SUPPLEMN 1 - APPAREWT VO11RAE INCREASE DUE TO TRIAXIAL STRESSES

I PURPOSE

WADC Technical Report 54-391 reported apparent volume increases innotched stress rupture specimens approaching 10 percent of the originalvolume of the notched section for a single specimen of S-816 heat resis-tant alloy. A series of measurements was subsequently undertaken todetermine whether or not a volume increase occurred.

II GFE'A C0O15IDRRATIONS.

Mechanics of materials are based upon a number of fundamental assum-tions, one of which is that the volume of structural materialst even underextremely large loads, remains practically constant, Indications of ±t 1percent change in volume would not upset previous theories of fracture.The 10 percent volume increase of notched sections of stress-rupture testspecimens reported in WADC Technical Report 54-391 cannot be considered tobe due to errors in measurement. Some more fundamental reason must beinvolved in this observation. Volume increase of this magnitude, if proven,would be of great interest to personnel investigating time dependentcharacteristics of materials.

III FACTUAL DATA

Figure 21 from WADC Technical Report 54-391 reproduced herein asFigure 1 ihows the notch contours of a notch before and after time-deformationat elevated temperature. Three notches were contained on a single axialload specimen for which Figure 1 was prepared so the test conditions wereidentical for each notch. Ibot radii of 0.005, 0.010 and 0.060 inchesindicated volume increases of 9.2, 11.7 and 7.8 percent, respectively, whencomputed from the data published. Similar notch contour measurements weremade on specimens of 3-816 and Inconel X-550 subjected to stress-rupturetest conditions. Measurements were made on notched portions of unbrokentest specimens with a shop microscope. Measurements were made on four sides

WADC TE 54-391Supplement 1

of some specimens. Complete notch contours were determined. The stres-rupture characteristics of the materials under consideration are reproducedfrom Figures 4, 5 and 7 of WADC Technical Report 54-391 as Figures 2, 3and 4 of this report to show the comparative test conditions for eachspecimen used for volume determinations.

Volume determinations were obtained by measuring notch contour areaswith a planimeter, computing equivalent radii and calculating the volumeof the related right circular cylinder. Results were checked by dividingeach notch into a series of rings and repeating the calculations. Inaddition, results were checked by using the volume calculation procedureoutlined in WADG Technical Report 54-391. The results of the calculationsare contained in Table I, which also lists the nominal stress and time torupture for each specimen. Correlation of the data in Table I and locationson the stress-rupture plots of Figures 2, 3 and 4 show that the apparentvolume increases reported are not a function of stress, time or notchsensitivity. However, rather large deformations are indicated for 3-816,and practically none for Inconel X-550. The amount of apparent volumeincrease corresponds to the relative ductility of the two materials.Waspalloy with ductility between that of S-816 and Inconel X-550 was foundto have apparent volume increases in the range of 1.5 to 3.0 percent.

The apparent volume increases noted would naturally suggest corres-pmding density decreases. Density measurements of S-816 resulted in avalue of 8.67 for the untested material and 8.73 for the notched section ofspecimen S-20 after test. The lack of confirmation of volume change bydensity measurements indicates that some mechanism other than volume increasemust be operating to provide the indications obtained in WADC TechnicalReport 54-391.

The method of computation of volume assumes that plane cross-sectionsof notched specimens remain plane when the specimen is deformed. The datapresented indicate the possibility that originally plane sections, subjectedto stress gradients which extend above the elastic stress limit, do notremain plane. In order to check this possibility, a notched specimen ofS-816 alloy was ground flat parallel to the axis on two sides to obtain anotched flat specimen 0.14 inches thick, Lines perpendicular to the specimenaxis were scribed across the notched section and the specimen was subjectedto 50,000 psi nominal axial stress for 50 hours at 13500F. Figure 5 showsthe deformation of the originally straight grid lines. Considerabledeviation of the plane sections represented by the scribed lines is evident,even at locations considerably removed from the notch root.

WAEC TR 54-391 2Supplement 1

The stress distribution in notched bar specimens is not linear, andas materials are stressed such that the highest stresses reach the inelasticrange defined by the stress-strain curve, the strains would be expected todistribute non-linearly. A detailed analysis of this stress condition forcreep tests is presented in WADC Technical Report 54-175, Part 2&

IV CONCLJSIONS

Supplementary data obtained after the release of WADC Technical Report54-391 indicate that no appreciable volume change occurred in the testmaterials under the experimental conditions used. The measurements whichwere taken indicating an apparent volume increase are believed to becorrect, but a proper interpretation of the data is believed to be thatoriginally plain sections of notched specimens of ductile material maydistort appreciably when partially plastic load conditions are inosed.The amount of deformation of plain sections is related to the ductilityof the material as well as the stress gradients imposed.

WADC TR 54-391 3Supplement 1

TABLE I

APPARENT VOWNE CHAIE IN NOTCHESTRESS-RUPTURE SPCIMMS

Specimen Tezperature Stress Rupture Notch Volume Change,Number °F PSI Time, Hours Radius Percent

s-17 1350 50,000 89.1 D .005 9.2

s-17 1350 50,000 89.1 D .010 11.7

317 1350 50,000 89.1 D .060 7.8

S-20 16oo 27,000 14.6 .o6o 8.1

3-27 1500 30,000 79.8 .o6o 7.7

1-13 1350 6o,ooo 30.1 .005 1.5

1-13 1350 60.000 30.1 .045 NIL

1-13 1350 6o,ooo 30,1 .100 NIL

1-18 16oo 18,000 358.7 .045 NIL

1-22 1350 35,000 197.4 .045 NIL

1-22 1350 35,000 197.4 .100 NIL

1-25 1350 65,000 42.-4 .100 NIL

1-27 1350 40,000 157.1 .100 NIL

1-34 16oo 25,000 64.6 .045 NIL

1-57 1350 40,000 138.5 .020 3-0

WADC TR 54-391 4Supplement 1

06mw 0

crz

.n 0

4- U,

> z D0

zE 0

E 00 zLL

0In- L

- - 2

op m in2

4.-.w

dip 0

z

0 In

0t Ia: LiN D

0

4PuI '93UOJS! IDIP08

WAMl TR 54~-391 5Supplemnt 1

U.

0____ 0

0 4n

C w_ x0

0

Sn z4=1 4

.04. I~ I0 I.P=* 0 .i0

U..

EF w

N IL. 0~

2~

IxCD w

~.0

"i CL

U- U

wC 0)

woI--

0000 0 0 0 0

Isd 0001 'SSSLh4S LL

WADC TR 54-391 6Supplement I.

tL0

0 I0i')

c *.1i - v 04.. V

00

00 00-U

(0

0 0

.C 0

100,

0.holl w

0.

V) U)

w

/ _ r.

_ _ _ _ _ _ _ _ _ _ _0 w0~C D

Isd 0001 'SsajS.'sL

WADC TR 54~-391 7Supplement I

0L0

0004-4 4-~00

L) o U

0.00E 0

o 00 0 0

c 0't 0

.2 w

>-

w

Uw

0~0

it w

x -D

!Sd~~ 0010SJWAX R 54391SupplmenC9

FIGURE 5 CHANGE OF SHAPE OF PLANK CROSS-SWTIONtS AS INDICATmDBY D~7OMA(TION OF SCRIBED 1NM.

WADC TR 54-391 9Supplement 1