Hardness Uncertainty EADS HRC 5 Indents (2)
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UNCERTAINTY OF MEASUREMENT FOR HARDNESS This spreadsheet has been drawn up to be inaccordance with the EN ISO speciications co!erin" #rine$$ % Roc'we$$ hardness( I t super sedes !ersion ) in order to o$ $ow the ca$ cu$ ati on *ethod "i!en in the UoM se standards but i s in act consi dered techni ca$ iner ior to issue ) which was *or e consistent wi th t he ISO + and *ore representati!e o actua$ *achine peror*ance( The est i*at e o uncer taint , is app$ icab$ e to a$$ co**on s,ste*s i (e( Roc'we$ $% &i c'ers and #rine$$ and wo app$icab$e to portab$e s,ste*s a$so( The spreadsheet shou$d be copied and co*p$eted or at $east one% idea$$ , ) !a$ues o each ran"e on eac within the $ab( Each sheet shou$d be $abe$ ed with the ran"e and appro- hardness( The ana$,sis r e.uires the o$$owin" inputs t o be *ade /t hese are hi"h$ i"hted i n +reen i n the wor 'ed e-a* Identiication o testin" Machine Certiied !a$ue o reerence b$oc' The units o the hardness sca$e /i(e(HRc% H&120 The per *itt ed to$er ance r o* the ca$ ibration st andar d in unit s o hardness( These are e-tr acted ro* tab$ section o the re$e!ant speciication( These tab$es ha!e been reproduces in the 3T o$er ance tab$es3 sheet o ea*p$e or a #rine$$ *achine at around )42H# the to$erance is 567 )8 o the hardness 9 2(2) : )42 9 4H The reso$ution to which the sca$e can be read% note or ano$"ue sca$es this is not the sca$e di!ision but th sca$e "raduations can be re$iab$ e sub7di!ided b, e,e( This *ust be input in ter*s o the hardness sca$e i the reso$ution or &ic'ers is ta'en as unit o the ; ocu$ar ssca$e% this *ust be e.uated to a correspondin" hardness at the re"ion o interest on the harness sca$e or the assess*ent( Uncer taint , o reer ence b$oc' /ro* certi icate0( The ana$,sis assu*es thi s is .uoted at the <48 conide uncer taint , is a!ai$ ab$e ro* the certi icat e% ta'e the certi ied ran"e o !a$ues and di !ide thi s b, ;(=1 /i(e( t The !a$ues obtained b, 4 i*pressions on the test b$oc' The !a$ues o 4 i *pr essions on a t,pica$ but ho*o"eneous sa*p$ e% prepared t o the nor*a$ i nish and $ at idea$ $, be o hardness in t he sa*e "enera$ re"i on as the test b$oc' / i(e( within the sa*e third o t he hardn the sa*p$e shou$d be re7prepared beore EACH o the i!e indents( The re.uired input !a$ues shou$d be entered into the bo-es that are hi"h$i"hted with a pa$e "reen bac'"ro &a$ues o e-panded uncertaint, are "i!en or a sin"$e test i*pression and the *ean o 1 i*pressions Note> This ana$,sis i s or the Uncertaint, o the test *ethod and does not consider the eect o te*peratu ho*o"eneit,( A$so% the ana$,si s does not consider the e ect o roundin" the ina$ resu$t in accordance with an, speciicti i(e( it is the uncertaint, o the as *easured resu$t based on *achine and *ethod app$ication $i*itations
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Transcript of Hardness Uncertainty EADS HRC 5 Indents (2)
Intro
UNCERTAINTY OF MEASUREMENT FOR HARDNESS
This spreadsheet has been drawn up to be inaccordance with the EN ISO specifications covering Brinell, Vickers and Rockwell hardness. It supersedes version 2 in order to follow the calculation method given in the UoM sections of these standards but is in fact considered technical inferior to issue 2 which was more consistent with the ISO Guide to uncertainty and more representative of actual machine performance.
The estimate of uncertainty is applicable to all common systems i.e. Rockwell, Vickers and Brinell and would also be applicable to portable systems also.
The spreadsheet should be copied and completed for at least one, ideally 2 values of each range on each machine use within the lab. Each sheet should be labeled with the range and approx hardness.
The analysis requires the following inputs to be made (these are highlighted in Green in the worked example attached).
Identification of testing Machine
Certified value of reference block
The units of the hardness scale (i.e.HRc, HV30)
The permitted tolerance from the calibration standard in units of hardness. These are extracted from tables in the calibration section of the relevant specification. These tables have been reproduces in the 'Tolerance tables' sheet of this workbook (for eample for a Brinell machine at around 250HB the tolerance is +/- 2% of the hardness = 0.02 * 250 = 5HB)
The resolution to which the scale can be read, note for anolgue scales this is not the scale division but the level to which the scale graduations can be reliable sub-divided by eye. This must be input in terms of the hardness scale in question. i.e if the resolution for Vickers is taken as unit of the 1 ocular sscale, this must be equated to a corresponding difference in hardness at the region of interest on the harness scale for the assessment.
Uncertainty of reference block (from certificate). The analysis assumes this is quoted at the 95% confidence level. If no uncertainty is available from the certificate, take the certified range of values and divide this by 1.73 (i.e. the root of three)
The values obtained by 5 impressions on the test block
The values of 5 impressions on a typical but homogeneous sample, prepared to the normal finish and flatness by the lab and ideally be of hardness in the same general region as the test block (i.e. within the same third of the hardness scale). Ideally the sample should be re-prepared before EACH of the five indents.
The required input values should be entered into the boxes that are highlighted with a pale green background.
Values of expanded uncertainty are given for a single test impression and the mean of 3 impressions
Note: This analysis is for the Uncertainty of the test method and does not consider the effect of temperature or material non-homogeneity.
Also, the analysis does not consider the effect of rounding the final result in accordance with any specifiction requirement, i.e. it is the uncertainty of the as measured result based on machine and method application limitations
Issue 3 March 2007
HRCTest machine identificationHD-03Certified value of test block41.4UnitsHRC
Resolution scale can be read to0.2in units of hardnessFive determinations on test block Five determinations on typical sample141.6143.8241.2244.8341.4345.0441.4445.0541.0544.6Mean41.344.6Standard Deviation0.2280.498Std uncertainty0.102Uncertainty of Measurement for a Single IndentDistributionDivisorStd UncertStd Unc^2Uncertainty of test block from cert (units)0.3Exp. Uncert20.1500.023Maximum permissible error ( not percentage)1.5Specified2.80.5360.287Repeatability on CRM0.102Normal10.1160.014(includes allowance for t=1.14)scale resolution0.2full range rect3.460.0580.003Repeatability on sample0.498Normal10.5680.322(includes allowance for t=1.14)Sum of squares0.649Combined uncertainty0.805Degrees of freedomCoverage factor
Expanded Uncertainty for a Single Indent1.6E+00HRCUncertainty of Measurement for the Mean of Three IndentsUncertainty of test block from cert0.3Exp. Uncert20.1500.023Maximum permissible error1.5Specified2.80.5360.287Repeatability on CRM0.102Normal10.1160.014scale resolution0.2full range rect3.460.0580.003Repeatability on sample0.228Normal10.2600.068Sum of squares0.394Combined uncertainty0.628Degrees of freedomCoverage factor
Expanded Uncertainty for the Mean of Three Indents1.3E+00HRC
Tolerance tablesBrinellVickersRockwell
