The certification of the absorbed energy (low energy) of Charpy V-notch reference test pieces for tests at 20 °C : ERM®-FA013bu.
Date: 2015-07-09
Institutions: Institute for Reference Materials and Measurements
Subjects: approval, metrology, physical sciences, research method, research report, resistance of materials

CERTIFICATION REPORT 

The certification of the absorbed energy (low energy) of 
Charpy V-notch reference test pieces for tests at 20 °C: 
ERM®-FA013bu 

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JRC95787 

EUR 27216 EN 

ISBN 978-92-79-47896-3 (PDF) 
ISSN 1831-9424 (online) 
doi:10.2787/213718 

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Abstract 
This certification report describes the processing and characterisation of ERM®-FA013bu, a batch of Charpy V-notch certified reference test pieces 
certified for the absorbed energy (KV). Sets of five of these test pieces are used for the verification of pendulum impact test machines according to 
ISO 148-2 (Metallic materials - Charpy pendulum impact test – Part 2: Verification of testing machines).  
The absorbed energy (KV) is procedurally defined and refers to the impact energy required to break a V-notched test piece of standardised 
dimensions, as defined in ISO 148-1. The certified value of ERM®- FA013bu is made traceable to the SI, via the SI-traceable certified value of the 
master batch ERM®-FA013ba, by testing samples of ERM®- FA013bu and ERM®-FA013ba under repeatability conditions on an impact pendulum 
verified and calibrated with SI-traceably calibrated tools. The certified value is valid only for strikers with a 2 mm tip radius. The certified value is valid 
at (20 ± 2) °C. 

 
 
 
 
 
 
 
 
 
 
 
 
CERTIFICATION REPORT 

The certification of the absorbed energy (low energy) of 
Charpy V-notch reference test pieces for tests at 20 °C: 
ERM®-FA013bu 

T. Linsinger, A. Dean, G. Roebben 

European Commission, Joint Research Centre 
Institute for Reference Materials and Measurements (IRMM) 
Geel, Belgium 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Disclaimer 

Certain commercial equipment, instruments, and materials are identified in this paper to specify adequately the 
experimental  procedure.  In  no  case  does  such  identification  imply  recommendation  or  endorsement  by  the 
European Commission, nor does it imply that the material or equipment is necessarily the best available for the 
purpose.  

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Summary 

This  certification  report  describes  the  processing  and  characterisation  of  ERM®-
FA013bu,  a  batch  of  Charpy  V-notch  certified  reference  test  pieces  certified  for  the 
absorbed energy (KV). Sets of five of these test pieces are used for the verification of 
pendulum  impact  test  machines  according  to  ISO  148-2  (Metallic  materials  -  Charpy 
pendulum impact test – Part 2: Verification of testing machines [1]).  
The  absorbed  energy  (KV)  is  procedurally  defined  and  refers  to  the  impact  energy 
required  to  break  a  V-notched  test  piece  of  standardised  dimensions,  as  defined  in 
ISO 148-1 [2]. The certified value of ERM®- FA013bu is made traceable to the SI, via 
the SI-traceable certified value of the master batch ERM®-FA013ba, by testing samples 
of  ERM®-  FA013bu  and  ERM®-FA013ba  under  repeatability  conditions  on  an  impact 
pendulum verified and calibrated with SI-traceably calibrated tools. The certified value is 
valid only for strikers with a 2 mm tip radius. The certified value is valid at (20 ± 2) °C. 

The certified value for KV (= energy required to break a V-notched test piece using a 
pendulum  impact  test  machine)  and  the  associated  expanded  uncertainties  (k = 2 
corresponding to a confidence level of about 95 %) calculated for the mean of a set of 
five test pieces, are: 

Steel Charpy V-notch test pieces 

Certified value 2) 
[J] 

Absorbed energy (KV) 1) 

19.7 

Uncertainty 3) 
[J]  

0.8 

1) The absorbed energy (KV) is a method defined measurand. KV is the impact energy required to break a 
V-notched bar of standardised dimensions, as defined in ISO 148-1. The certified value is valid only for 
strikers with a 2 mm tip radius, and in the temperature range of (20 ± 2) °C. 
2) The certified value of ERM®-FA013bu, and its uncertainty, is traceable to the International System 
of  Units  (SI),  via  the  master  batch  ERM®-FA013ba  of  a  similar  nominal  absorbed  energy  by  testing 
samples of ERM®-FA013ba and ERM®-FA013bu under repeatability conditions on an impact pendulum 
verified and calibrated with SI-traceably calibrated tools.  

3)  Estimated  expanded  uncertainty  of  the  mean  KV  of  the  5  specimens  (delivered  as  1  set),  with  a 
coverage factor k = 2, corresponding to a level of confidence of about 95 %, as defined in ISO/IEC Guide 
98-3,  Guide  to  the  expression  of  uncertainty  in  measurement  (GUM:1995).  The  number  of  degrees  of 
freedom of the certified uncertainty is n RM = 57. 

1 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 

 
 
 
 
Table of contents 

Summary ..............................................................................................................1 

Table of contents .................................................................................................3 

Glossary ...............................................................................................................4 

1 

1.1 
1.2 

Introduction ..................................................................................................5 
The Charpy pendulum impact test ................................................................... 5 
The certification concept of Master Batch and Secondary Batch ..................... 6 
1.2.1  Difference between Master and Secondary Batches ................................................. 6 
1.2.2  Certification of a Secondary Batch of Charpy V-notch test pieces ............................. 6 
1.2.3  Uncertainty of the certified value of a Secondary Batch of Charpy V-notch test pieces .. 7 

2  Participants ...................................................................................................7 

3  Processing ....................................................................................................7 
Machining of Charpy test pieces ...................................................................... 7 
Heat treatment of hot-rolled bars ..................................................................... 7 
Final machining of Charpy test pieces ............................................................. 8 
Quality control ................................................................................................. 8 
Packaging and storage .................................................................................... 8 

3.1 
3.2 
3.3 
3.4 
3.5 

4  Homogeneity ................................................................................................8 

5  Stability .........................................................................................................9 

6  Characterisation ......................................................................................... 10 
Characterisation tests .................................................................................... 10 
Data from Master Batch ERM®-FA013ba ....................................................... 11 
Calculation of KVCRM and of uchar .................................................................... 11 

6.1 
6.2 
6.3 

7  Value assignment ....................................................................................... 12 
Certified value, combined and expanded uncertainty ..................................... 12 

7.1 

8  Metrological traceability ............................................................................ 13 

9  Commutability ............................................................................................ 13 

10  Summary of results .................................................................................... 14 

11 

Instructions for use .................................................................................... 14 
11.1 
Intended use ................................................................................................. 14 
11.2  Sample preparation ....................................................................................... 14 
11.3 Pendulum impact tests ...................................................................................... 15 

Acknowledgements ........................................................................................... 15 

References ......................................................................................................... 16 

Annex 1 .............................................................................................................. 17 

Annex 2 .............................................................................................................. 18 

3 

 
 
 
 
 
 
Glossary 
AISI 
ASTM 
BCR 
CRM 
EC 
ERM® 
IMB 
IRMM 
ISO 
JRC 
k 
KV 

KVCRM 

KVMB 
LNE 
MB 
nMB 

nSB  
RSD 
s 
SB 
sh 

sMB  

sSB 

uCRM 
UCRM 
uchar 
uchar,rel 
uh 
ui 
uMB 
uMB,rel 
MBX  

SBX  

D h 

n RM 

American Iron and Steel Institute 
American Society for Testing and Materials 
Community Bureau of Reference 
Certified Reference Material 
European Commission 
European Reference Material 
International Master Batch 
Institute for Reference Materials and Measurements 
International Organization for Standardization 
Joint Research Centre 
Coverage factor 
Absorbed energy = energy required to break a V-notched test piece of 
defined shape and dimensions when tested with a pendulum impact 
testing machine 
Certified KV value of a set of 5 reference test pieces from the 
Secondary Batch 
Certified KV value of the Master Batch test pieces 
Laboratoire national de métrologie et d’essais 
Master Batch 
Number of samples of the Master Batch tested during certification of 
the Secondary Batch 
Number of samples of the Secondary Batch tested for certification  
Relative standard deviation 
Standard deviation 
Secondary Batch 
Standard deviation of the results of the samples tested to assess the 
homogeneity of the Secondary Batch  
Standard deviation of the nMB results of the samples of the Master 
Batch tested for the certification of the Secondary Batch  
Standard deviation of the nSB results of the samples tested for the 
characterisation of the Secondary Batch  
Combined standard uncertainty of KVCRM 
Expanded uncertainty (k = 2, confidence level of about 95 %) of KVCRM 
Standard uncertainty of the result of the characterisation tests 
Relative standard uncertainty of the result of the characterisation tests 
Contribution to uncertainty from homogeneity 
Value of uncertainty from contribution i 
Standard uncertainty of KVMB 
Relative standard uncertainty of KVMB 
Mean KV value of the nMB measurements on samples of the Master 
Batch tested when characterising the Secondary Batch  
Mean KV value of the nSB results of the samples tested for the 
characterisation of the Secondary Batch  
difference between the height of the centre of gravity of the pendulum 
prior to release and at the end of the half-swing during which the test 
sample is broken 
Effective number of degrees of freedom associated with the 
uncertainty of the certified value 

4 

 
 
 
 
 
1 

Introduction 

1.1  The Charpy pendulum impact test 
The Charpy pendulum impact test is designed to assess the resistance of a material 
to  shock  loading.  The  test,  which  consists  of  breaking  a  notched  bar  of  the  test 
material  using  a  hammer  rotating  around  a  fixed  horizontal  axis,  is  schematically 
presented in Figure 1. 

b
b

1
1

2
2

d
d

D h
D h

a
a

3
3

c
c

Figure 1: Schematic presentation of the Charpy pendulum impact test, showing a: the 
horizontal rotation axis of the pendulum, b: the stiff shaft on to which is fixed d: the 
hammer. The hammer is released from a well-defined height (position 1). When the 
hammer  has  reached  maximum  kinetic  energy  (shaft  in  vertical  position  2),  the 
hammer strikes c: the test sample, which is positioned on a support and against the 
pendulum anvils (not shown). The height reached by the hammer after having broken 
the sample (position 3) is recorded. The difference in height between position 1 and 3 
(D h)  corresponds  with  a  difference  in  potential  energy,  and  is  a  measure  of  the 
energy required to break the test sample. 

The energy absorbed by the test sample is very dependent on the impact pendulum 
construction  and  its  dynamic  behaviour.  Methods  to  verify  the  performance  of  an 
impact  pendulum  require  the  use  of  reference  test  pieces  as  described  in  ISO  and 
other international standards [1, 3]. The reference test pieces dealt with in this report 
comply with a V-notched test piece shape of well-defined geometry [1], schematically 
shown in Figure 2. 

anvil
anvil

anvil
anvil

sample
sample

location and direction of impact
location and direction of impact

Figure 2: Schematic drawing of a V-notched Charpy test piece (top-view), indicating 
the place and direction of impact. 

5 

 
 
 
 
 
 
 
1.2  The certification concept of Master Batch and Secondary Batch 

1.2.1  Difference between Master and Secondary Batches 
The  BCR  reports  by  Marchandise  et  al.  [4]  and  Varma  [5]  provide  details  of  the 
certification of BCR “Master Batches” (MB) of Charpy V-notch certified reference test 
pieces.  The  certified  value  of  a  Master  Batch  is  obtained  using  an  international 
laboratory intercomparison.  
This report describes the production of a “Secondary Batch” (SB) of Charpy V-notch 
certified  reference  test  pieces  at  the  Institute  for  Reference  Materials  and 
Measurements  (IRMM)  of  the  European  Commission's  (EC)  Joint  Research  Centre 
(JRC). The work was performed in accordance with procedures described in the BCR 
reports [4] and [5]. The certification of a SB is based on the comparison of a set of 
SB  test  pieces  with  a  set  of  test  pieces  from  the  corresponding  MB  under 
repeatability conditions on a single pendulum.  

The  BCR  reports  [4]  and  [5]  were  published  in  1991  and  1999,  respectively.  Since 
2000, the calculation of the certified value and the estimation of its uncertainty have 
been updated to an approach compliant with the ISO/IEC Guide to the Expression of 
Uncertainty  in  Measurement  [6].  This  revised  approach  was  developed  and 
presented by Ingelbrecht et al. [7, 8], and is summarised below.  

1.2.2  Certification of a Secondary Batch of Charpy V-notch test pieces 
The  certified  absorbed  energy  of  a  SB  of  Charpy  V-notch  reference  test  pieces 
SBX  ) tested 
(KVCRM) is calculated from the mean KV-value of a set of SB-samples (
on  a  single  pendulum.  This  value 
SBX   has  to  be  corrected  for  the  bias  of  this 
particular pendulum. The bias of the pendulum at the moment of testing the samples 
of the SB, is estimated by comparing the mean KV-value of a number of samples of 
the  MB  ( MBX ),  tested  together  with  the  SB  samples  under  repeatability  conditions, 
with the certified value of the MB (KVMB). KVCRM is then calculated as follows [8]: 

=

CRM





MB

MB





SB

Eq. 1 

For  this  approach to  be reliable,  the  pendulum  used for  the tests  on  MB  and  SB  in 

repeatability  conditions,  must  be  well  performing.  In  other  words,  the  ratio 

KV
X

MB

MB

must  be  close  to  1.  IRMM  allows  a  difference  of  5 %  (KVMB ≥  40 J)  or  2 J  (KVMB  < 
MBX ,  corresponding  with  the  level  of  bias  allowed  for 
40 J)  between  KVMB  and 
reference pendulums specified in  ISO 148-3 [9].  

Also,  for  reasons  of  commutability,  a  comparable  response  of  the  pendulum  to  the 
MB  and  SB  samples  is  required.  This  is  the  reason  why  MB  and  SB  samples  are 

made from nominally the same steel. Moreover, it is checked that the ratio 

CRM

 is 

KV
KV

MB

close  to  1.  IRMM  allows  a  difference  of  20 %  (KVMB ≥   40 J)  or  8 J  (KVMB <  40 J) 
between KVCRM and KVMB to ensure that the MB and SB samples have a comparable 
interaction with the pendulum. 

6 

 
 
 
 
(cid:215)
  
 
 
 
 
 
 
1.2.3  Uncertainty of the certified value of a Secondary Batch of Charpy V-notch test 

pieces 

The uncertainty of the certified value of the SB is a combination of the uncertainties 
of the right-hand side factors in Eq. 1. It is clear that the MB-SB approach necessarily 
results in a larger uncertainty of the certified value of SB in comparison with the MB. 
The additional uncertainty depends on the uncertainty of the ratio  MBX /
SBX . The full 
SBX   is  relatively  large.  However, 
measurement  uncertainty  of  the  values  MBX   and 
(repeatability  conditions,  pendulum 
when  all  conditions  mentioned  above 
performance, and commutability between Secondary and Master Batch) are fulfilled, 
then  the  uncertainties  of  the  values 
SBX   have  several  contributions  in 
MBX   and 
common, in particular the uncertainty due to the bias of the pendulum. These shared 
uncertainty  components  do  not  contribute  to  the  uncertainty  of  the  ratio  MBX /
SBX , 
and only the standard deviations of the SB and MB results in the MB-SB comparison 
test  need  to  be  taken  into  account  (see  also  Section  6.3).  Thus,  the  MB-SB 
comparison  approach  can  produce  a  value  for  the  uncertainty  of  KVCRM  that  is 
sufficiently  small  to  meet  the  requirements  of  the  intended  use  of  the  certified 
reference material (CRM).  

2  Participants 
The  processing  of  the  SB  (ERM®-  FA013bu)  test  pieces  was  carried  out  by  the 
Institut  für  Eignungsprüfung  GmbH  (IfEP),  Marl  (DE),  using  AISI4340/1.6565  steel 
delivered  by  Tata  Steel  International  Germany  GmbH.  The  MB  samples  (ERM®-
FA013ba) used in the characterisation of the SB were provided by IRMM, Geel (BE). 
The  homogeneity  of  the  SB  was  evaluated  based  on  data  obtained  at  IfEP  using  a 
pendulum  verified  according 
[1]. 
Characterisation  of  the  SB  was  carried  out  at  IRMM  using  a  pendulum  verified 
according to the criteria imposed by ISO 148-2 [1]. The tests performed were within 
the scope of an ISO/IEC 17025 accreditation (BELAC 268-Test). 
Data  evaluation  was  performed  at  IRMM.  The  certification  project  performed  was 
within the scope of an ISO Guide 34 accreditation (BELAC 268-RM). 

imposed  by 

the  criteria 

ISO 148-2 

to 

3  Processing 
The ERM®- FA013bu test pieces were prepared from bars of  AISI 4340/1.6565 steel 
delivered by Tata Steel International Germany GmbH. Production of the test pieces 
from these bars was performed under the supervision of IfEP (see sections 3.1 - 3.5). 

3.1  Machining of Charpy test pieces 
The broad bars were cut into 65 discs each. 14 discs from one bar were cut into 1624 
Charpy specimens and  machined to the dimensional requirements of ISO 148-3 [9] 
and engraved to ensure identification. 

3.2  Heat treatment of hot-rolled bars 
The heat treatment of the specimens was performed at VTN Witten GmbH (DE) in a 
vacuum-furnace.  1624  specimens  of  the  batch  were  heat-treated  according  to  the 
following procedure: 
Step 1: normalisation treatment at 900 °C for 150 minutes 
Step 2: Cool down in air 
Step 3: hardening at 850°C for 90 minutes 
Step 4: quenching in oil 
Step 5: first tempering at 280 °C for 180 minutes 

7 

 
 
 
Step 6: cool down in air 
Step 7: second tempering at 280 °C for 180 minutes 
Step 8 cool down in air. 
The  specimens  were  distributed  over  3  baskets.  The  baskets  were  stacked  in  the 
furnace  and  each  basket  had  three  thermocouples  to  monitor  the  temperature 
homogeneity. The measured temperatures at all positions were within the tolerance 
of +/- 6 °C as required by IfEP. 

3.3  Final machining of Charpy test pieces 
After heat treatment, the specimens were machined to the final dimensions specified 
in ISO 148-3 [9] by IfEP. During this process the specimen numbers were transferred 
to one of the end faces. Finally the specimens were notched using a milling process. 

3.4  Quality control 
When all samples from the batch were fully machined, a selection of 25 samples was 
made.  The  dimensions  of  the  25  samples  were  checked  on  against  the  criteria 
+
00.0
30.00.55
specified  in  ISO  148-3  [9]  (length 
 mm,  height  10.00  ±  0.06   mm,  width 
10.00  ±  0.07 mm,  notch  angle  45 ± 1°,  height  remaining  at  notch  root  8.00  ± 
0.06 mm,  radius  at  notch  root  0.250  ±  0.025 mm,  distance  between  the  plane  of 
symmetry  of  the  notch  and  the  longitudinal  axis  of  the  test  piece  27.5  ±  0.2 mm). 
None of the samples was outside the ranges specified in ISO 148-3 [9].  

25 samples selected throughout the batch were checked for geometrical compliance 
and  impact  tested  using  a  pendulum  type  Zwick  PSW  750  (nominal  energy  450  J), 
verified in September 2014 according to ISO 148-2 [1]. 
The  tests  were  done  on  September  29,  2014.  The  results  are  reported  in  the 
production  report  of  October  2,  2014  [10].  The  average  KV  of  the  25  samples  was 
19.85  J,  which  is  within  the  desired  energy  range  (15  J  to  25  J).  The  standard 
deviation  of  the  test  results  (s  =  0.67 J,  RSD  =  3.39  %)  was  below  the  1.2  J 
maximum  allowed  by  the  contract.  The  variation  was  checked  again  during  the 
characterisation tests at IRMM (see Section 0). 

3.5  Packaging and storage 
Finally,  the  samples  were  cleaned  and  packed  in  sets  of  5 randomised samples,  in 
oil-filled  and  vacuum  sealed  plastic  bags.  These  oil-filled  bags,  were  packed  in  a 
second sealed plastic bag, and shipped to IRMM. After arrival (October 9, 2014) the 
1595  samples  (or  319  sets)  of  ERM®-FA013bu  were  registered  and  stored  at  room 
temperature, pending distribution. 

4  Homogeneity 
The  test  pieces  are  sampled  from  the  SBs,  which  are  sufficiently,  but  not  perfectly, 
homogeneous.  Therefore,  an  appropriate  homogeneity  contribution  uh  to  the 
uncertainty of the certified value is required. uh is related to sh, the standard deviation 
between the samples in the SB (sample-to-sample heterogeneity), but also depends 
on  the  number  of  samples  over  which  the  KV-value  is  averaged.  ISO 148-2  [1] 
specify that the pendulum verification must be performed using 5 test pieces, which 
is  why  a  CRM-unit  consists  of  a  set  of  5  test  pieces.  The  appropriate  uncertainty 
contribution must be an estimate of the set-to-set heterogeneity, which in the case of 

a set of 5 test pieces can be calculated as

u =
h

s

h
5

. 

8 

 
 
-
 
 
Here,  uh  is  estimated  from  sh,  the  standard  deviation  of  results  obtained  at  IfEP  on 

September 29, 2014 (sh = 0. 67 J). This leads to  

u

h

s
= h
5

=

30.0

J

 (1.51%).  

As is required for a homogeneity test, the samples were randomly selected from the 
whole  batch.  The  number  of  samples  tested  (25)  is  sufficiently  large  to  reflect  the 
homogeneity of the full SB (1595 samples). It can be noted that uh is probably a slight 
overestimation,  since  it  contains  also  the  repeatability  of  the  instrument.  However, 
the latter cannot be separated or separately measured. 

5  Stability 
The stability of the absorbed energy of Charpy V-notch certified reference test pieces 
was first systematically investigated for samples of nominally 120 J by Pauwels et al., 
who  did  not  observe  measurable  changes  of  absorbed  energy  [11].  Additional 
evidence for the stability of the reference test pieces produced from AISI 4340 steel 
of lower energy levels (nominally 15 J, 30 J and 100 J) has been obtained during the 
International  Master  Batch  (IMB)  project  [12].  In  the  IMB-project,  the  stability  of  the 
certified  test  pieces  was  judged  from  the  change  of  the  mean  of  means  of  the 
absorbed energy obtained on 7 reference pendulums over a three year period. None 
of the three regression slopes for the tested energy levels was statistically significant 
at the 5 % probability level. Given the large sample-to-sample heterogeneity and the 
limited  number  of  samples  (5)  in  a  CRM  unit,  the  uncertainty  contribution  from 
instability  is  considered  to  be  insignificant  in  comparison  to  that  of  homogeneity.  A 
dedicated isochronous study (test temperature 18 °C, reference temperature -20 °C) 
was  organised  by  IRMM  by  batches  of  30,  80  and  120  J  from  the  same  steel  was 
organised  by  IRMM  and  showed,  as  expected,  no  change  of  the measured  values. 
Uncertainty  of  stabilities  for  120  months  were  calculated  as  0.7-2.8  J  (1.8-2.4  %). 
These  uncertainties  are  entirely  driven  by  the  measurement  precision  and  it  was 
concluded that no uncertainty contribution for potential change was needed [14]. 

treatment.  Annealing 

The main reason for the microstructural stability of the certified reference test pieces 
is  the  annealing  treatment  to  which  the  samples  were  subjected  after  the 
austenisation 
the 
equilibrium phases are the same as the (meta-)stable phases at ambient temperature 
(a -Fe  and  Fe3C).  The  only  driving  force  for  instability  stems  from  the  difference  in 
solubility  of  interstitial  elements  in  the  a -Fe  matrix,  between  annealing  and  ambient 
temperature.  Relaxation  of  residual  (micro-)stress  by  short-range  diffusion  or  the 
additional  formation  or  growth  of  precipitates  during  the  shelf-life  of  the  certified 
reference test pieces is expected to proceed but slowly.  

temperatures  where 

is  performed  at 

Rather  than  neglecting  the  stability  issue,  efforts  are  spent  to  better  establish  the 
stability of the certified values of batches of Charpy CRMs. Until such further notice, it 
is decided to specify a limited shelf-life. A period of 10 years is chosen, counting from 
the  date  of  the  characterisation  tests  on  the  SB.  Since  batch  ERM®-FA013bu  was 
characterised in February 2015, the  validity of the certificate reaches until February 
2025.  

9 

 
 
 
 
 
 
 
 
Characterisation 

5.1  Characterisation tests 
30 samples from ERM®-FA013bu (sets 5, 100, 152, 188, 242 and 285) were tested 
under  repeatability  conditions  together  with  25  samples  from  MB  ERM®-FA013ba 
(sets  77,  90,  100,  105  and  107),  using  the  Instron  Wolpert  PW 30  (serial  number 
7300  H1527)  machine  of  IRMM,  an  impact  pendulum  yearly  verified  according  to 
procedures described in ISO 148-2 [1].  
Tests  were  performed  on  February  10  (laboratory  temperature  20 ± 1 °C),  in 
accordance  with  ISO 148-1  [2].  The  measurement  sequence  was:  SB-MB-SB-MB-
SB-MB-SB-MB-SB-MB-SB.  The  measured  absorbed  energy  values  were  corrected 
for friction and windage losses.  

After  testing,  all  Charpy  samples  show  'first-strike'  marks:  these  are  the  marks 
caused  by  the  interaction  between  sample  and  anvils  during  the  first  and  intended 
hammer impact. Upon fracture, the broken halve samples loose contact with hammer 
and  anvils  and  follow  one  of  a  variety  of  possible  trajectories,  away  from  the 
pendulum,  depending  on  the  properties  of  both  pendulum  and  test  material.  It  may 
occur  that  samples  show  'second-strike'  marks.  These  are  marks  caused  by  a 
second  impact  of  the  already  broken  halve  samples  back  onto  the  anvils.  This 
phenomenon  has  been  described  by  Schmieder  et  al.  [13].  None  of  the  broken 
FA013bu but three of FA013ba samples showed second-strike marks. These results 
of FA013ba were therefore not included in the further calculations. 
The  accepted  data  obtained  on  individual  test  pieces  are  shown  in  Figure  3  and 
Annex 1.  The results of the measurements are summarised in Table 1.  

The sequence of the samples shows one high value for the master batch (sequence 
number  78).  This  was  flagged  as  outlier  using  the  Grubbs  procedure  but  was 
retained,  as  the  respective  set  of  samples  met  the  specifications  of  ISO  148-3  for 
reference samples (standard deviation < 3 J). 

]
J
[

y
g
r
e
n
e
d
e
b
r
o
s
b
a

35

30

25

20

15

10

5

0

0

20

40

60
test sequence

80

100

120

Master batch
Secondary batch

Figure  3:  Absorbed  energy  values  of  22  test  pieces  of  ERM®-FA013ba,  compared 
with 30 test pieces of ERM®-FA013bu; data are displayed in the actual test sequence 

10 

 
 
 
 
 
 
 
 
 
Table 1: Characterisation measurements of Batch ERM®-FA013bu 

Number of 
test pieces  

Mean value  

Standard 
deviation   

Relative 
standard 
deviation  

nMB , nSB 

SBX  

MBX  , 
[J] 

ERM®-FA013ba (MB) 

ERM®-FA013bu (SB) 

22 

30 

28.47 

19.71 

sMB , sSB 

RSDSB, RSDMB   

[J] 

0.98 

0.74 

[%] 

3.45 

3.74 

The  SB-results  meet  the  ISO 148-3  acceptance  criteria  for  a  batch  of  reference 
materials (sSB < 2 J for KVSB < 40 J).  

5.2  Data from Master Batch ERM®-FA013ba  
To  calculate  KVCRM  for  ERM®-FA013bu  one  needs  KVMB  of  the  MB  used,  i.e. 
ERM®-FA013ba.  Table  2  shows  the  main  MB-data,  taken  from  the  Certificate  of 
Analysis of ERM®-FA013ba (Annex 2). 

Table 2: Data from the certification of Master Batch ERM®-FA013ba 

Certified 
absorbed energy 
of Master Batch 

KVMB (J) 

Standard 
uncertainty of 
KVMB 
uMB (J) 

Relative standard 
uncertainty of 
KVMB 
uMB,rel (%) 

ERM®-FA013ba 

28.46 

0.23 

0.81 

5.3  Calculation of KVCRM and of uchar 
From the data in Tables 2 and 3, and using Eq. 1, one readily obtains that KVCRM = 
19.71  J  (rounding  in  accordance  with  uncertainty;  see  Table  4).  The  uncertainty 
associated  with  the  characterisation  of  the  SB,  uchar,  is  assessed  as  in  Eq.  2  [8], 
which sums the relative uncertainties of the three factors in Eq. 1: 

u

char

=

KV

CRM

u
KV

2
MB
2
MB

+

s

n
SB

2
SB
X

2
SB

+

s

n

MB

2
MB
X

2
MB

Eq. 2 

MBX were  obtained  under  repeatability  conditions.  Therefore, 

SBX   and 
uncertainty  of  the  ratio 
  is  not  affected  by  the  contributions  from 
reproducibility  and  bias  of  the  pendulum  used  to  compare  MB  and  SB.    Table  3 
summarises  the  input  quantities  of  the  uchar  uncertainty  budget,  their  respective 
statistical  properties,  and  shows  how  they  were  combined.  The  effective  number  of 
degrees of freedom (n eff) for uchar is obtained using the Welch-Satterthwaite equation 

SB / X

the 

MB

X

11 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
(cid:215)
(cid:215)
 
 
from  the  combined  uncertainty  (uc)  and  the  individual  uncertainty  contributions  (ui) 
and their respective degrees of freedom (n i) (Eq. 3) [6]. 

=

eff

u
N

∑

=

1

i

4
c
u

4
i

i

Eq. 3

Table 3: Uncertainty budget for uchar for ERM®-FA013bu 

source of 
uncertainty 

measured 
value  

standard 
uncertainty 

probability 
distribution 

relative 
uncertainty 

KVMB  Certification of 

28.46 

(J) 

(J) 

0.23 

normal 

(%) 

0.81 

MB 

comparison of 
SB and MB in 
repeatability 
conditions 

SBX  

MBX

19.71 

0.13 

normal 

0.68 

28.47 

0.21 

normal 

uchar,rel (%) 

uchar (J) 

0.74 

1.29 

0.25 

degrees 
of 
freedom 

14 

29 

21 

53 

6  Value assignment  

6.1  Certified value, combined and expanded uncertainty 
As shown in 5.3, KVCRM = 19.7 J. The uncertainty of the certified value is obtained by 
combining  the  contributions  from  the  characterisation  study,  uchar,  and  from  the 
homogeneity  assessment,  uh,  as  is  summarized  in  the  following  uncertainty  budget 
(Table 4).  

The relevant number of degrees of freedom calculated using the Welch-Satterthwaite 
equation [6], is sufficiently large (n RM = 57) to justify the use of a coverage factor k = 2 
to  expand  the  confidence  level  to  about  95 %.  The  obtained  expanded  uncertainty 
provides  justification  for  the  SB-MB  approach  followed:  UCRM  is  sufficiently  smaller 
(UCRM = 0.8 J) than the verification criterion of 4 J for industrial pendulums [1] or even 
2 J for reference pendulums [9].  

12 

 
 
n
n
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Table 4: Uncertainty budget of KVCRM for ERM®-FA013bu  

source of uncertainty 

relative value ui 
(%) 

uchar 

characterisation of SB 

uh 

homogeneity of SB 

1.29 

1.51 

Combined standard uncertainty, uCRM (%) 

1.98 

Combined standard uncertainty, uCRM (J) 

0.39 

Expanded Uncertainty, k = 2, UCRM (%) 

3.97 

Expanded Uncertainty, k = 2, UCRM (J) 

0.78 

degrees 
of 
freedom 

53 

24 

57 

7  Metrological traceability 
The  certified  property  is  defined  by  the  Charpy  pendulum  impact  test  procedure 
described in ISO 148-1 [2].  

The  certified  value  of  the  MB  ERM®-FA013ba  is  traceable  to  the  SI,  since  it  was 
obtained using an interlaboratory comparison, involving a representative selection of 
qualified 
the  standard 
procedures and using instruments verified and calibrated with SI-traceable calibration 
tools.  

laboratories  performing  the  tests 

in  accordance  with 

The certified value of ERM®-FA013bu is made traceable to the SI-traceable certified 
value  of  the  MB  by  testing  SB  and  MB  samples  in  repeatability  conditions  on  an 
impact pendulum verified and calibrated with SI-traceably calibrated tools. Therefore, 
the certified value of ERM®-FA013bu is traceable to the International System of Units 
(SI)  via  the  corresponding  Master  Batch  ERM®-FA013ba  of  a  similar  nominal 
absorbed energy. Absorbed energy KV is a method-specific value, and can only be 
obtained by following the procedures specified in ISO 148-1 [2].  

8  Commutability 
The  intended  use  of  the  certified  reference  test  pieces  is  the  verification  of  Charpy 
impact pendulums. During the certification of the MB, different pendulums were used, 
each  equipped  with  an  ISO-type  striker  of  2 mm  tip  radius.  Until  further  notice,  the 
certified values are not to be used  when the test pieces are broken with  an ASTM-
type striker of 8 mm tip radius [10]. 

13 

 
 
 
 
 
 
 
 
 
 
9  Summary of results 
The certified value and associated uncertainty are summarized in Table 5. 

Table 5: Certified value and associated uncertainty for ERM®-FA013bu. 

Steel Charpy V-notch test pieces 

Certified value 2) 
[J] 

Absorbed energy (KV) 1) 

19.7 

Uncertainty 3) 
[J]  

0.8 

1) The absorbed energy (KV) is a method defined measurand. KV is the impact energy required to break a 
V-notched bar of standardised dimensions, as defined in ISO 148-1. The certified value is valid only for 
strikers with a 2 mm tip radius, and in the temperature range of (20 ± 2) °C. 
2) The certified value of ERM®-FA013bu, and its uncertainty, is traceable to the International System 
of  Units  (SI),  via  the  master  batch  ERM®-FA013ba  of  a  similar  nominal  absorbed  energy    by  testing 
samples of ERM®-FA013ba and ERM®-FA013bu under repeatability conditions on an impact pendulum 
verified and calibrated with SI-traceable calibrated tools.  

3)  Estimated  expanded  uncertainty  of  the  mean  KV  of  the  5  specimens  (delivered  as  1  set),  with  a 
coverage factor k = 2, corresponding to a level of confidence of about 95 %, as defined in ISO/IEC Guide 
98-3,  Guide  to  the  expression  of  uncertainty  in  measurement  (GUM:1995).  The  number  of  degrees  of 
freedom of the certified uncertainty is n RM = 57. 

10  Instructions for use 

10.1  Intended use 
Samples  of  ERM®-FA013bu  correspond  to  the  ‘certified  reference  test  pieces’  as 
defined  in  ISO 148-3  [9].  Sets  of  five  of  these  certified  reference  test  pieces  are 
intended for the indirect verification of impact testing machines with a striker of 2 mm 
tip radius according to procedures described in detail in ISO 148-2 [1].  

The  indirect  verification  provides  an  assessment  of  the  bias  of  the  user’s  Charpy 
pendulum  impact  machine.  This  bias  assessment  can  be  used  in  the  calculation  of 
the  measurement  uncertainty  of  Charpy  tests  on  the  pendulum  after  indirect 
verification.  Such  uncertainty  calculation  requires  the  certified  value,  the  associated 
uncertainty,  and  in  some  cases  also  the  degrees  of  freedom  of  the  uncertainty,  all 
given on page 1 of the certificate. 

10.2  Sample preparation 
Special  attention  is  drawn  to  the  cleaning  of  the  specimens  prior  to  the  tests.  It  is 
mandatory  to  remove  the  oil  from  the  sample  surface  prior  to  testing,  without 
damaging the edges of the sample. Between the moment of removing the protective 
oil  layer  and  the  actual  test,  corrosion  can  occur.  This  must  be  avoided  by  limiting 
this period of time, while keeping the sample clean. 

14 

 
 
 
 
 
 
 
 
 
 
 
The following procedure is considered a good practice. 

1. 

2.  

First  use  absorbent  cleaning-tissue  to  remove  the  excess  oil.  Pay  particular 
attention to the notch of the sample, but do not use hard (e.g. steel) brushes 
to remove the oil from the notch.  
Before  testing,  bring  the  specimens  to  the  test  temperature  (20  ±  2)  °C.  To 
assure  thermal  equilibrium  is  reached,  move  the  specimens  to  the  test 
laboratory at least 3 h before the tests. 

An  optional  cleaning  step  with  organic  solvents  may  be  inserted  between  1  and  2. 
Please  note  that  the  use  of  ethanol  is  discouraged,  as  it  results  in  a  sticky  residue 
with remaining traces of oil. Any residual solvents shall be removed by wiping with an 
absorbent tissue before proceeding to step 2. 

11.3 Pendulum impact tests 
After  cleaning,  the  5  samples  constituting  a  CRM-unit  need  to  be  broken  with  a 
pendulum impact test machine in accordance with  ISO 148-2 [1] standards. Prior to 
the  tests,  the  anvils  must  be  cleaned.  It  must  be  noted  that  Charpy  test  pieces 
sometimes leave debris  on the Charpy pendulum anvils. Therefore, the anvils must 
be  checked regularly  and  if  debris  is found,  it  must  be removed. The  uncertainty of 
the certified value applies to the mean of the 5 KV-values. 

Acknowledgements 
The authors wish to thank J. Snell, A. Held, R. Koeber, and H. Emons (all IRMM) for 
reviewing of the certification report. 

15 

 
 
 
 
References 

1.  ISO 148-2: Metallic materials - Charpy pendulum impact test - Part 2: Verification 
of testing machines, International Organization for Standardization, Geneva (CH), 
2008 

2.  ISO  148-1:  Metallic  materials  -  Charpy  pendulum  impact  test  -  Part  1:  Test 

method, International Organization for Standardization, Geneva (CH), 2009 

3.  ASTM  E23  -  07ae1  Standard  Test  Methods  for  Notched  Bar  Impact  Testing  of 
Metallic Materials, ASTM International, West Conshohocken, PA (USA), 2007 
4.  Marchandise H., Perez-Sainz A., Colinet E., Certification of the impact toughness 
of V-notch Charpy specimens, in BCR information series, Community Bureau of 
Reference - BCR, Brussels (BE), 1991 

5.  Varma  R.K.,  The  certification  of  two  new  master  batches  of  V-notch  Charpy 
impact toughness specimens in accordance with EN 10045-2: 1992, CRM's 015 
and 415, EUR Report 18947 EN - European Communities, Luxembourg - 1999 - 
ISBN 92-828-2244-3 

6.  ISO/IEC  Guide  98-3:2008,  Uncertainty  of  measurement  -  Part  3:  Guide  to  the 
International 

expression  of  uncertainty 
Organization for Standardization, Geneva (CH), 2008 

in  measurement 

(GUM:1995), 

7.   Ingelbrecht, C. and Pauwels J., EC Reference Materials for Impact Toughness - 
Traceability  and  uncertainty.  Presentation  at  Eurachem  Eurolab  symposium  on 
Reference Materials for Technologies in the New Millennium, Berlin, May 22-23, 
2000. 

8.  Ingelbrecht,  C.,  Pauwels,  J.,  and  Gyppaz,  D.,  Charpy  specimens  from  BCR  for 
machine  verification  according  to  EN  10045-2.  Poster  presentation  at  Charpy 
Centenary Conference, October 2-5, Poitiers (FR), 2001 

9.  ISO 148-3: Metallic materials - Charpy pendulum impact test - Part 3: Preparation 
and  characterization  of  Charpy  V-notch  test  pieces  for  indirect  verification  of 
pendulum  impact  machines,  International  Organization  for  Standardization, 
Geneva (CH), 2008 

10. Production report: Charpy V-notch reference test pieces of 2 J nominal absorbed 
energy ERM-FA013bu, Institut für Eignungsprüfung GmbH, Marl (DE), October 2, 
2014 

11. Pauwels,  J.,  Gyppaz,  D.,  Varma,  R.,  Ingelbrecht,  C.,  European  certification  of 
Charpy  specimens:  reasoning  and  observations,  in  Pendulum  Impact  testing:  A 
Century  of  Progress.  Seattle,  Washington:  American  Society  for  Testing  and 
Materials, 1999  

12. McCowan,  C.N.,  Roebben,  G.,  Yamaguchi,  Y.,  Lefrançois,  S.,  Splett,  J.  D., 
Takagi, S., Lamberty, A., International Comparison of Impact Reference Materials 
(2004), J. ASTM International, Vol. 3(2), 2004 

13. Schmieder, A. K., Purtscher P. T., Vigliotti, D. P., The role of strike marks on the 
reproducibility  of  Charpy  impact  test  results,  in  Pendulum  impact  machines: 
procedures  and  specimens  for  verification,  ASTM  STP  1248,  ed.  Siewert,  T.  A. 
and  Schmieder  A.  K.,  American  Society  for  Testing  and  Materials,  Philadelphia 
(USA), 1995. 

14.  Lamberty, A, Roebben, G, Dean, A, Linsinger T, Study of the stability of Charpy 
V-notch  reference  test  pieces  for  tests  at  20  °C  (ERM®-FA013ba,  ERM®-
FA015v and ERM®-FA016ax) during long-term storage at 18°C, EUR 26348 EN, 
Luxembourg: Publications Office of the European Union, 2015 

16 

 
 
 
 
Annex 1 
Results  of  characterisation  measurements  of  ERM®-FA013bu  as  measured 
according to ISO 148-1 at IRMM, February 10, 2015. 

Master Batch ERM®-FA013ba  

Secondary Batch ERM®-
FA013bu 

KV (J) 

19.68 
19.45 
19.21 
20.04 
18.51 
20.78 
18.77 
18.65 
19.00 
19.12 
20.66 
20.06 
19.35 
20.66 
19.47 
18.83 
19.35 
20.18 
18.07 
19.59 
19.83 
19.90 
20.02 
19.42 
20.25 
20.49 
20.73 
20.61 
20.13 
20.61 

19.71 

0.74 

3.74 

1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
28 
29 
30 

Mean (J) 

Standard deviation 
(J) 
RSD (%) 

KV (J) 

29.54 
27.56 
27.82 
28.48 
28.48 
28.35 
28.87 
28.08 
28.21 
28.21 
27.95 
27.69 
28.74 
27.95 
27.3 
27.43 
jammed 
31.82 
29.67 
28.21 
jammed 
27.89 
28.81 
jammed 
29.21 

28.46 

0.98 

3.45 

17 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Annex 2 

18 

 
 
 
 
 
 
 
 
 
19 

 
 
 
 
 
20 

 
 
 
 
 
 
 
European Commission 

EUR 27216 EN – Joint Research Centre – Institute for Reference Materials and Measurements 
Title:  

The certification of the absorbed energy (low energy) of Charpy V-notch reference test pieces for tests 
at 20 °C: ERM®-FA013bu 
Author(s): T. Linsinger, A. Dean, G. Roebben 
Luxembourg: Publications Office of the European Union 
2015 – 20 pp. – 21.0 x 29.7 cm 
EUR – Scientific and Technical Research series – ISSN 1831-9424 
ISBN 978-92-79-47896-3 
doi:10.2787/213718 

 
 
 
 
 
 
 
As the Commission's in-house science service, the Joint Research Centre's mission is to provide EU policies 
with independent, evidence-based scientific and technical support throughout the whole policy cycle. 

Working in close cooperation with policy Directorates-General, the JRC addresses key societal challenges 
while stimulating innovation through developing new methods, tools and standards, and sharing its know-
how with the Member States, the scientific community and international partners. 

Key policy areas include: environment and climate change; energy and transport; agriculture and food 
security; health and consumer protection; information society and digital agenda; safety and security, 
including nuclear; all supported through a cross-cutting and multi-disciplinary approach. 

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doi:10.2787/213718 

ISBN: 978-92-79-47896-3