I

IS 1828( Part 2 ) :2002ISO 7500-2:1996

wP12Fl=l=T fmwbl@kPJTd3-3nimi W’?mwvnw

Indian Standard

IMETALLIC MATERIALS — VERIFICATION OF STATIC

UNIAXIAL TESTING MACHINESPART 2 TENSION CREEP TESTING MACHINES — VERIFICATION OF THE APPLIED LOAD

I

Ics 77.140.10

@ BIS 2002

BUREAU OF INDIAN STANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

.4

March 2002 Price Group 5

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Mechanical Testing of Metals Sectional Committee, MTD 3

NATIONAL FOREWORD

This Indian Standard ( Part 2 ) which is identical with ISO 7500-2:1996 ‘Metallic materials — Verificationof static uniaxial testing machines — Part 2: Tension creep testing machines — Verification of theapplied load’ issued by the International Organization for Standardization ( ISO ) was adopted by theBureau of Indian Standards on the recommendation of the Mechanical Testing of Metals SectionalCommittee ( MTD 3 ) and approval of the Metallurgical Engineering Division Council.

The creep is a property indicating the continuous flow of a metal or alloy when stressed below its yieldpoint or proportional limit. It is more marked at elevated temperatures and is, therefore, important inconnection with metals and alloys for service at high temperature. Creep behaviour of metals andalloys for relevant applications are required to be determined accurately assuch materials may be putto critical uses consisting of constant loading and elevated temperatures.

In order to obtain the results accurately, it is necessary that the machine is calibrated on regularbasis. This will also be necessary for the realizability of the machine towards the reproducibility andrepeatability of the results obtained.

In this adopted standard, some terminology and conventions are, however, not identical to thoseused in Indian Standards. Attention is especially drawn to the following:

a) Wherever the words ‘International Standard’ appear referring to this standard, they should beas read as ‘Indian Standard’.

b) Comma ( , ) has been used as a decimal marker while in Indian Standards, the current practiceis to use a point ( . ) as the decimal marker.

In this adopted standard, reference appears to certain International Standards for which Indian Standardsalso exist. The corresponding Indian Standards which are to be substituted in their place are listedbelow along with their degree of equivalence for the editions indicated:

ISO 376:1987

ISO 7500-1 :1986

do

Identical

International Standard Corresponding Indian Standard Degree of Equivalence

ISO 204:1961 IS 3407 ( Part 1 and Part 2 ) :1983 Technically

Method for creep testing of steel at equivalentelevated temperatures : Part 1Tensile creep testing ( first revision)and Part 2 Tensile creep stressrupture testing ( first revision )

IS 4169:1988 Method for calibrationof force proving instruments used forthe verification of uniaxial testingmachines ( first revision )

IS 1828 ( Part 1 ) :1991 Metallicmaterials — Verification of staticuniaxial testing machines : Part 1Tensile testing machines ( secondrevision )

In reporting the results of a test or analysis made in accordance with this standard, if the final value,observed or calculated, is to be rounded off, it shall be done in accordance with IS 2: 1960 ‘Rules forrounding off numerical values ( revised )’.

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IS 1828 ( Par? 2 ) :2002

ISO 7500-2:1996

‘i

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Indian Standard ,,,]!!,,,,,:,.METALLIC MATERIALS — VERIFICATION OF STATIC

UNIAXIAL TESTING MACHINESPART 2 TENSION CREEP TESTING MACHINES — VERIFICATION OF THE APPLIED LOAD

1 Scope

This part of ISO 7500 specifies the verificationtesting machines used for uniaxial creep testingtension in accordance with ISO 204.

The verification consists of

— a general inspection of the testing machine;

ofin

— a verification of the load applied by the testingmachine.

This part of ISO 7500 applies to dead weight and levertype creep testing machines. The machines with aload measuring systemlj shall beante with ISO 7500-1.

2 Normative references

The followirm standards contain

verified in accord-

movisions which.through refer&ce in this text, cons~tute provisions ofthis part of ISO 7500. At the time of publication, theeditions indicated were valid. All standards are subjectto revision, and parties to agreements based on thispart of ISO 7500 are encouraged to investigate thepossibility of applying the most recent editions of thestandards indicated below. Members of IEC and ISOmaintain registers of currently valid International Stan-dards.

ISC 204:— z), Metallic materials — Uniaxial creeptesting in tension.

ISO 376:1987, Metallic materials — Calibration bfforce proving instruments used for the verification ofuniaxial testing machines.

ISO 7500-1:1986, Metallic materials — Verification ofstatic uniaxial resting machines — Part 1; Tens~letesting machines.

3 Symbols and their meanings

For the purposes of this part of ISO 7500, the symbolsgiven in table 1 shall apply.

---

For the purposes of this part of ISO 7500 the follow-ing types of creep testing machines are recognized:

—

—

—

—

4

deadweight machines, with or without guides(see figures 1 and 2);

overslung or underslung lever machines (seefigures 3,4 and 5);

jockey weight machines, either with overslung orunderslung lever (see figures 6 and 7);

any combination of the types of machines men-tioned above (see figure 8).

General inspection of the testingmachine

The verification of the testing machine shall only becarried out if the machine is in good working order.For this purpose, a general inspection of the machineshall be carried out before verification of the load ap-plied by the machine (see annex A).

1) For the purposes of this part of ISO 7500, a force measuring system comprises load cell plus conditioning plus indicator.

2) To be published. (RevisionoflSO/R204:1961 and lSO/R 206:1961 )

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IS 1828 ( Part 2 ) :2002ISO 7500-2:1996

Table 1 — Symbols and their meanings

.

Symbol Unit Meaning

FN N Maximum capacity of the load range of the testing machine

Fi N Load applied by the testing machine to be verified— for deadweight machines: F, = mg 1)— for lever-type machines: ~ = mgR 1j— for jockey weight machines, the value of Fi is indicated on the scale of the machine

F N True load indicated by the force-proving instrument

F N Arithmetic mean of several measurements of F for the same discrete load

Fmm Frnin N Highest or lowest value of F for the same discrete load

FM N Force exerted by the masses on the scale pan of the machine

Fv N Lower limit of the verified load range

R — Lever ratio used for the verification

b % Relative repeatability error of the testing machine

d N Discrimination threshold

d, N Discrimination threshold corresponding to 20 ‘%. of the maximum force range (FN)

a % Relative discrimination threshold

q Yo Relative accuracy error of the testing machine

1) g = local accelerationdue to gravity,in metres per second squared.

Self alignmentjoint

Specimen

Self alignmentjoint

Specimen

..

Figure 1 — Schematic representation of the Figure 2 — Schematic representation of theoperating principle of a deadweight tensile creep operating principle of a deadweight tensile creep

testing machine (example) testing machine with guides (example)

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IS 1828 ( Part 2 ) :2002

ISO 7500-2:1996

Self alignmentjoint

Specimen

Figure 3 — Schematic representation of the operating principle of an overslung lever tensile creeptesting machine (example)

l’- Self alignmentjoint

LSpecimen

_.“.---

Hgure 4 — Schematic representation of the operating principle of an underslung lever tensile creeptesting machine (example)

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IS 1828 ( Part 2 ) :2002ISO 7500-2:1996

- Self alignmentjoint

= Specimen

Figure 5 — Schematic representation of the operating principle of an overslung double lever tensilecreep testing machine (example)

“.

~“’’’ignmen’

Figure 6 — Schematic representation of the operating principle of an overslung lever tensile creeptesting machine with jockey weight (example)

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IS 1828 (Part 2):2002ISO 7500-2:1996

Seif alignmentjoint

Specimen

Figure 7 — Schematic representation of the operating principie of an underslung doubie iever tensiie creeptesting machine with jockey weight (example)

19

A 1

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Self a(ignmentjoint

Specimen

u

.--.

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Figure 8 — Schematic representation of the operating principie of a tensiie creep testing machine usinga combinaticmof different ioading systems (example)

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IS 1828 ( Part 2 ) :2002ISO 7500-2:1996

. e%

5 Verification of the load applied by thetesting machine

5.1 General

This verification shall be carried out for each of theload ranges used. if the testing machine has severalload ranges, each ranges), shall be regarded as a sep-arate testing machine.

This verification shall be carried out using tensionforce-proving instruments. These instruments shall bein accordance with ISO 376. The class of the force-proving instrument shall be equal to or superior to theclass determined for the creep testing machine.

5.2 Masses

The masses used to apply the forces during verifica-tion shall be the masses normally used during testing,which can be either:

a) known masses with an accuracy equal to or bet-ter than t 0,1 ‘34.; verified at least every 10 years,or;

b) masses dedicated for use with a given creeptesting machine applied in the same sequence asduring the test.

5.3 Determinationof the discriminationthreshold

The discrimination threshold d of the machine is de-fined as the smallest increment of force that can beapplied and detected during the verification procedure.

The discrimination threshold d shall be determined at20 Yo, 60 Y. and 100 Y. of the maximum load FN ofthe force measuring range. If loads of a magnitudeless than 0,2F~ are to be tested (see 5.2), the dis-crimination threshold must additionally be determinedat the lower limit of the provided testing range.

The discrimination threshold d k measured as themagnitude of the force resulting from the smallestmass added to, or removed from, the scale pan of themachine or the load which corresponds to the small-est recordable movement of the jockey weight whichcauses a detectable change at the indicator of theforce-proving instrument.

The relative discrimination threshold a is calculated foreach value of load specified according to the followingformula:

da=— Xloo

F

and shall remain within the limitsthe class of machine considered.

given in table 2 for

The discrimination threshold d shall be expressed innewtons

5.4 Determinationof the lowerlimitofverification

The lower limit of verification Fv shall be specified ac-cording to table 2.

Table 2 — Lower limit of verification

Claaa Fv

0,5 400d1

1 200d1

2 10Odl

NOTE — d, is the discrimination threshold corresponding to

20 ‘Y. of the force measuring range.

NOTE 1 The lower limit of verification of the machine maybe less than the permissible operating range of the equiva-lent grade force-proving instrument used to determine thediscrimination threshold at the 60 Y. and maximum loadconditions.

Consequently, if one wishes to accurately verify the testingmachine load at the lower end of the range as well, it willbe necessaty to employ two measuring instruments, onefor the upper range and a second one having appropriatecapacity for the extreme lower measuring range.

5.5 Testprocedure

Verification shall be carried out for each load range forwhich a grade is sought.

Verification shall not be performed below the lowerlimit Fv for any load range.

5.5.1 Alignment

The force-proving device shall be mounted in the ma-chine with the self-alignment devices normally usedincluded at each end of the loading train.

3) In the case of a deadweight machine, load range means the range over which the machine is to be used; in the case of alever-type machine it is the load range for each separate lever ratio.

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IS 1828 ( Part 2 ) :2002

ISO 7500-2:1996 4

5.5.2 8alancing the lever

It is necessary to balance the loading train to achievea zero loading reading on the force-proving devicewhen it is mounted in the loading train in place of thetest piece. The precise method of balancing is de-pendent upon the design of machine, however ingeneral the procedures given in 5.5.2.1 and 5.5.2.2will be applicable.

In some machines, it is not possible to fully balancethe lever, in which case the minimum force that isapplied to the test piece with no masses on the scalepan shall be recorded on the verification report andtaken into account when calculating the load appliedto the test piece when undertaking a creep test,

5.5.2.1 Overslung lever

The load verification device shall be hung in the load-ing train in place of the test specimen, with the lowerloading bar disconnected immediately below theproving device. The lever shall then be balanced bymovement of the adjustment weight normally at-tached to the machine, or by the addition of an extrabalancing weight. The load indicator of the verificationdevice shall be set to zero before connecting thelower loading bar.

NOTE 2 It must be remembered that the lever will need tobe rebalanced before commencing creep testing.

5.5.2.2 Underslung lever

Because of the geometrical design of underslunglever machines it is seldom possible to balance themass of the lower loading bars, lever and scale pan. Itis therefore necessary to zero the force-proving de-vice with the Iqwer loading bar disconnected, andthen merely to note the load applied when the loadingtrain is reconnected and the system adjusted to bringthe lever to the normal operating position with nomasses placed on the scale pan. If this load is greaterthan that calculated in 5.4 then it shall become thelower limit of verification

5.5.3 Temperature compensation

Sufficient time shall be allowed for the verificationequipment to attain a stable temperature. The tem-perature shall be noted at the beginning and end ofthe application of each series of loads. Where necess-ary, temperature corrections shall be applied to thedeflections of proving devices using the equationsgiven in ISO 376.

5.5.4 Conditioning

In order to condition the system, it is necessary to ex-ercise the creep testing machine and force-proving

device three times between zero force and the maxi-

4

mum load to be measured. Then, the force-provingdevice shall be reset to the zero force position.

5.5.5 Selection of test forces

A series of at least five approximately equispacedloads starting at 20 YO of the force range or the lowerlimit of verification, whichever is greater, shall be ap-plied.

When required, additional loads below 20 % of theload range down to the lower limit of verification(see 5.4) may be applied. One load is to be applied foreach increment of 5 Yo, or portion thereof, of the scaleto be verified below 20 % of the load range.

5.5.6 Application of test loads

For each range, the series of loads shall be applied inascending order and each series shall be repeated togive three series of such loads. After each series ofapplications the load shall be completely removed.

All three series of loads shall be applied with theloading system at the mid point of the normal operat-ing range (zero position). The measurements shall beconducted after the system has been stabilized espe- .

cially for machines with a damping device.

NOTE 3 On an overslung lever or a single underslung levercreep testing machine, this requirement implies that thethree series of loads are applied with the lever in the hori-zontal position.

Further, it has to be ensured that:

—

—

each test load applied will be free of shock andvibration, so that the load will therefore not ex-ceed its nominal value by more than the maxi-mum permissible error for the machine grade inquestion;

in case of lever type machines it has to be veri-fied that the permissible deviation of the leverfrom its horizontal position is exactly marked. Inthe range between these marked inclinations ofthe lever, it shall be checked to ensure that theload is within the permitted limits. This checkshall be carried out for the lowest and highestload of the range at the lower position of thelever. This procedure shall ensure that the devia-tion of the test load from its nominal value duringthe total duration of the creep test is kept withinthe limits of the maximum permissible error forthe machine grade in question.

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IS 1828 ( Part 2 ) :2002ISO 7500-2:1996

5.6 Assessment of the force applied bythemachine

5.6.1 Relative accuracyerror

The relative accuracy error, q, expressed as a percent-

age of the mean value of the true load ~, is given by

the equation

5.6.2 Relative repeatability error

The repeatability error, b, is, for each discrete force,the difference between the highest and lowest valuesmeasured with respect to the mean value of true load.It is given by the equation

Fb=

m.. - ‘rein x ,0.

F

6 Class of the testing machine

.Table 3 gives the maximum permissible values for therelative errors of accuracy and repeatability whichcharacterizes a testing machine in accordance withthe appropriate class.

Table 3 — Characteristics of the classes ofmachine

Classofmachine

0,5

1

2

Maximm

Relativediscrimination

thresholda

0,25

0,5

1

permissiblevalues(%)

Relativeerrorof

repeatability accuracyb 4

0,5 * 0,5

1,0 *lto

2.0 * 2.0

6.1 Levercreeptestingmachines

The grading shall cease to apply below theload that complies with these requirements.

minimum

It is possible for a range to be given several classesbut each class shall satisfy the requirements definedin 5.5.5.

It is permissible to classify a machine for one or sev-eral discrete forces, for each discrete force threemeasurements shall be conducted. The classificationobtained is valid only for the discrete forces verified.

!,:“

d

6.2 Deadweightcreeptestingmachines

Normaiiy the grading will be determined by the accu- ~racies of the masses used to apply the verificationforces and of the mass of the ioad suspension system ‘“beiow the test piece. However, for machines withguides below the test piece which could introduce ‘‘,,friction effects, it is necessary to calibrate the ma- b:

chine using a proving device. The calibration authority :,

shall be satisfied that the axis of loading is through the ;.longitudinal axis to the test piece.

‘.

7 Verification report !

‘3

The verification report shall contain at least the foiiow-ing information:

!a)Gneral information:

/1)

2)

3)

4)

5)

6)

7)

reference to this part of ISO 7500;ij

identification of the testing machine (type,make, serial number);

location of the machine;

method of verification used (see 5.1) and theidentity, class and date of the last calibrationcertificate of the verification equipment used;

the average temperature of the verificationequipment at the time of verification;

date of verification;

name of mark of the verifying se~ice whichperformed the verification.

j

b) Results of verification: ~\

1) for each force-measuring system used, theclass of each range verified and, if requested,the discrete values of relative errors of accu-racy, repeatability;

2) the lever ratio R used for each load range,where applicable;

3) when discrete forces have been verified, theactual forces, the class(es) obtained and, ifrequested, the discrete vaiues of relative er-rors of repeatability;

4) any anomaly found during the general in-spection.

8 Intervalsbetween verifications

The machine shall be verified at intervals not exceed-ing 5 years. However, if the predicted test iife ex-ceeds the date of the expiry of the verificationcertificate, then the machine shall be reverified priorto commencement of the creep test. Any machineshail also be reverified if it has been dismantled formoving or subject to major repair or adjustment

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IS 1828 ( Part 2 ) :2002ISO 7500-2:1996

Annex A(normative)

General inspection of the testing machine

The general inspection of the testing machine, whichshall be carried out before the verification of the ma-chine (see clause 5), shall comprise the following.

A.1 Visual examination

The

a)

visual examination shall verify:

that the machine is in good working order and notadversely affected by certain aspects of its gen-eral condition, such as:

— significant wear of the knife edges, support-ing points, bearings, grips or any defect inthe guiding elements of the pull rods,

— looseness in mounting of columns and fixedcrossheads;

b)

c)

d)

that the lever system isover its operating range;

free to swing smoothly

that the machine is not affected by environmentalconditions (vibration, effect of corrosion, localtemperature variations, etc.);

that the line of action of force. as far as ~ossible.runs through the centres of the knife edges orball seatings of the loading train.

A.2 Inspectionof the structure of themachine

A check shall be made to ensure that the structureand gripping systems will permit the force to be ap-plied axially.

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Bureau of Indian Standards

BIS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promoteharmonious development of the activities of standardization, marking and quality certification of goods andattending to connected matters in the country.

Copyright

BIS has the copyright of all its publications. NOpart of these publications maybe reproduced in any form withoutthe prior permission in writing of BIS. This does not preclude the free use, in the course of implementing thestandard, of necessary details, such as symbols and sizes, type or grade designations. Enquiries relating tocopyright be addressed to the Director (Publications), BIS.

Review of Indian Standards

Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewedperiodically; a standard along with amendments is reaffirmed when such review indicates that no changes areneeded; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standardsshould ascertain that they are in possession of the latest amendments or edition by referring to the latest issueof ‘BIS Catalogue’ and ‘Standards : Monthly Additions’.

This Indian Standard has been developed from DOC: No. MTD 3 ( 4330 ).

Amendments Issued Since Publication

Amend No, Date of Issue Text Affected

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