IS 12872: Metallic Materials – Calibration of Extensometers Used in Uniaxial Testing

2011·1.1 MB·English

by  Bureau of Indian Standards

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IS 12872 (2011): Metallic Materials – Calibration of
Extensometers Used in Uniaxial Testing [MTD 3: Mechanical
Testing of Metals]
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Satyanarayan Gangaram Pitroda
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IS 12872 : 1990 .
IS0 9513 : 1989
Indian Standard

METALLIC MATERIALS - VER~IFICATION OF
/-\
I \ ! EXTENSOMETERS USED IN UNIAXIAL TESTING
.&
UDC 62C).172.2.067.45:53.069.6

0 BIS 1990
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:
w I BUREAU OF INDIAN STANDARDS
\
MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG
NEW DELHI 110002

tsuguA 0991 Price Group 4
IS 12872 : 1990
IS0 9513 : 1989
Indian Standard
CILLATEM SLAIRETAM - NOITACIFIREV OF
SRETEMOSNETXE USED NI LAIXAINU GNITSET
NATIONAL FOREWORD
This Indian Standard, which is identical with IS0 9513: 1989’ttietallic materials -Verification of
extensometers used in uniaxial testin9: Issued by the International Organization for Standardizatron
(ISO), was adopted by the Bureau of In&an Standards on 20 April 1990 on the recommendatron of the
Mechanical Testing of Metals Sectional Committee (MTD 3) and approval of the Metallurgical
Engineering Division Council.
In the adopted standard certain conventions are not identical with those used in Indian Standards.
Attention is specrally drawn to the following:
a) Wherever the words’lnternational Standard’ a,ppear referring tothis standard, they should
be read as ‘Indian Standard’.
b) Comma (,) has been used as a decimal marker while in Indian Standards the current
practice is to use point (.),as the decimal marker.
As in the Original Standard, this Page is Intentionally Left Blank
IS 12872 :: 1990
IS0 9513 : 1989
1 scope spindles and a device for measuring accurately the change in
length produced. The variations in length can be measured, for
This International Standard specifies a method for the static example. using an interferometer or gauge blocks and a corn
verification of extensometers used in uniaxial testing. parator or a screw micrometer. The gauge blocks and com-
parator or micrometer used shall be calibrated by a method
The term “extensometer” is understood to mean the displace- which is traceable to the international unit (SII of length and
ment measuring device and the system for indicating or record- their accuracy shall be known. The error of the calibration ap
ing this displacement. paratus shall not be greater than one-third of the permissible
error of the extensometer (see table 2).
2 Symbols and their meanings The resolution of the calibration apparatus shall be as given tn
table 2.
Symbols used throughout this International Standard and their
meanings are given in table 1.
5 Procedure
Table 1 - Symbols and their meanings
5.1 Position of the extensometer
Symbol Meaning Unit
The extensometer shall be placed in the calibration apparatus in
4 Nominal value of gauge length of mm the same position and orientation in which it is used during
extensometer uniaxial testing so as to avoid errors due to loss of equilibriurn
Lk Measured value of gauge length of mm or deformation of any part of the extensometer.
extensometer
The extensometer shall be attached in the same way ai duyg
E mar Maximum limrt of verification rang e mm uniaxial testing.
p-ml” Minimum limit of verification range mm
‘i Displacement mdlcated by extensometer Pm 5.2 Temperature at which the verification is
‘t True displacement given by calrbration Pm made
apparatus
In general, the verification of the extensometer shall be carried
q1.e Relative gauge length error % out at a temperature stable to within + 2 OC; ihis temperatute
4 Relative bias error of extensometer 96 shall be within the range between 18 “C and 28 OC.
r Resolution of extensometer Pm
For extensometers used for uniaxial testing at temperatures out
side the range specified above, it’ is recommended that the
verification be carried out at or near the test temperature, if
3 Principle facilities exist.
The verification of an extensometer involves a comparison of The extensometershall be placed near the calibration apparatlls
the readings given by the extensometer with known variations or mounted on it for a sufficient length of time prior to Its
in length provided by a calibration apparatus. verification so that the parts of the extensometer and of the
calibration apparatus which are in contact shall attain the same
temperature.
4 Cahbration apparatus
5.3 Accuracy of gauge length of the
The calibration apparatus which allows a known displacement, extensometer
I,, to be applied to the extensometer may consist of a rigid
frame with suitable coaxial spindles or other fixtures to which The gauge length of the extensometer car) be measured directly
the extensometer can be attached. The calibration apparatus or indirectly. The following Indirect method is given as WI
shall comprise a mechanism for moving at Least one of the axial example.
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IS 12872 : 1990
IS0 9513 : 1989
ehT retemosnetxe is placed no a tfos latem tset eceip ni hcus a 2.5.5 ehT noitacifirev stsisnoc first fo eno seires fo ta tsae:
yaw taht eht blades ro stniop fo eht retemosnetxe evael rieht 01 ,stnemerusaem ,,I distributed yletamixorppa ylneve -hguorht
mark. ecnO eht retemosnetxe is ,devomer eht ecnatsid be- tuo eht noitacifirev egnar fo eht .retemosnetxe ehT -netxe
neewt eht marks no eht tset eceip is .derusaem retemos is devoiner dna neht placed back no eht noitarbilac ap-
.sutarap A dnoces seires fo stnemerusaem is neht edam ni eht
ehT evitaler error no eht eguag ,htgnel ,,c ,e detaluclac from eht emas rennam sa eht .tsrif For hcae seires fo stnemerusaem eht
gniwollof alumrof llahs ton deecxe eht seulav nevig ni elbat 2 : evisseccus snoitairav ni htgnel llahs be fo eht emas epyt
.e.i( rehtie sesaercni ro .)sesaerced
Depending no eht detcepxe esu fo eht ,retemosnetxe eht owt
seires fo stnemerusaem era edam rof sesaercni nI htgnel ro rof
sesaerced ni htgnel ro rof .htob
nI eht esac fo na retemosnetxe gnivah lareves eguag ,shtgnel
eht noitacifirev llahs be carried tuo rof hcae eguag .htgnel For hcae tnemerusaem ,tniop eht evitaler bias error s1 uclac
detal ees( .12.6.5
5.4 Range of verification
5.6 Determination of the characteristics of the
ehT noitacifirev egnar llahs be denifed yb eht resu ot revoc eht
extensometer
gnirusaem egnar required ot emmreted a nevig lairetam prop-
.ytre ehT mumlxam dna minimum limits ,,,E dna ,,,,,E fo eht
noitacifirev egnar llahs be hcus taht 1.65 noituloseR
ehT ,noituloser r, is eht tsellams ytitnauq hcihw nac be daer no
eht .tnemurtsni ehT seulav fo eht noituloser fo eht -netxe
retemos llahs be ni ecnadrocca htiw eht seulav nevig ni elbat .2
fI lareves segnar era specified yb eht ,resu hcae eno llahs be
2.6.5 Relative bias error
verified. nA elpmaxe fo noitacifirev segnar is nevig ni xenna .A
ehT segnar fo noitacifirev llahs be deton ni eht noitacifirev
The evitaler bias ,rorre qr, rof a nevig ,tnemecalpsid ,I is
.troper
detaluclac from eht alumrof
5.5 Verification procedure
5.5.1 When eht erutarepmet sah stabilized, it is nemmocer
ded ,taht erofeb ,noitacifirev eht retemosnetxe be dednetxe ta
tsael eciwt yb eht noitacifirev sutarappa revo eht noitacifirev 6 Classification of the extensometer
egnar fo eht .retemosnetxe fI possible, eht tnemecalpsid is
nekat ot a ylthgils evitagen eulav dna denruter ot .orez Where elbaT 2 gives eht mumixam permissible seulav rof eht evitaler
appropriate, eht retemosnetxe is teser ot .orez eguag htgnel ,rorre eht noituloser dna eht evitaler bias .rorre

Table 2 - Classification of extensometers
Calibration apparatus
mumixaM( )seulav
mumixaM _I__ ~~
Class
evitaler error mumixaM Maximum Absolute
of no the gauge percentage absolute noituloseR bias
extensometer
length of reading error error
‘IL&$ r/l, Ii - 1,
% % urn
5.0 t 5.0 0.25 + s,1 0.25 + 0.5
f 1.0 0-50 ;? 0,3 O-50 _t 0.1
2 + 2.0 1.0 i 0.6 1.0 ? 2.0
1
)1 revehcIhW eulav is eht .retaerg

,
-l_.-_l I. .- __---l_-.
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IS 12872 : 1990
IS0 9513 : 1989
7 Frequency of verification 2) identification of the extensometer (type, make,
serial number and mounting positron);
The time between two verifications depends on the type of
extensometer, the maintenance standard and the number of 3) type and reference number of calibration apparatus;
times the extensometer has been used. Under normal con-
ditions, it is recommended that verification be carried out at 4) temperature at which the verification was carried
out:
intervals of approximately 12 months. In no case shall the inter-
val exceed 18 months.
5) nature of variations of length for which the venfr-
cation was carried out, i.e. either for increases and/or
If a test is expected to last more than 18 months, the exten-
for decreases in length;
someter shall be verified before and after the test.
6) date of verification;
The extensometer shall be verified if it undergoes any major
repairs or adjustments.
7) name or mark of the service which carried out the
verification;
8 Verification report
8) date of expiry of the verificatron report
The venfication report shall contain at least the following infor- b) Results of the verification :
mation
I) class of each range of the extensometer;
:
a) General information
2) the individual values of the relative bias errors, if
1) reference to this International Standard; requested.

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IS 12872 : 1990
IS0 9513 : 1989
Annex A
(informative)
Example of verification ranges of an extensometer
50%
I
0,5% ,
0,05 %
:
First verification range 0.05 % to 0.5 %
Second verification range : 0.5 % to 5 % I of the nominal value of the extensometer travel
:
Third verification range 5 % to 50 % I

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