The certification of the absorbed energy (150 J nominal) of Charpy V-notch reference test pieces for tests at 20 °C : ERM-FA415ai : certification report.
Date: 2019-04-02
Institutions: Joint Research Centre
Subjects: Community certification, evaluation method, metal product, research report, resistance of materials, testing

CERTIFICATION REPORT 

 The certification of the absorbed energy  
(150 J nominal) of Charpy V-notch reference test pieces for 
tests at 20 °C: ERM®-FA415ai 

EUR 29712 EN 

 
 
  
 
 
 
 
 
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EUR 29712 EN 

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Abstract 

This certification report describes the processing and characterisation of ERM®-FA415ai, 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 operationally 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®-FA415ai is made traceable to the SI, via the SI-traceable certified value of the master batch          
ERM®-FA415s, by testing samples pieces of ERM®-FA415ai and ERM®-FA415s 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  
(150 J nominal) of Charpy V-notch reference test pieces for 
tests at 20 °C: ERM®-FA415ai 

F. Vanderveken, A. Dean, G. Roebben 

European Commission, Joint Research Centre 
Directorate F – Health, Consumers and Reference Materials 
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 

report  describes 

This  certification 
the  processing  and  characterisation  of  
ERM®-FA415ai,  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  operationally  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®-FA415ai is made traceable to the SI, via the 
SI-traceable  certified  value  of  the  master  batch  ERM®-FA415s,  by  testing  samples 
pieces  of  ERM®-FA415ai  and  ERM®-FA415s  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  uncertainty  (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] 

Uncertainty 3) 
[J]  

Absorbed energy (KV) 1) 

148 

5 

1) The absorbed energy (KV) is an operationally-defined measurand. KV is the impact energy required to 
break a V-notched test piece 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)  Certified  values  are  values  that  fulfil  the  highest  standards  of  accuracy.  The  certified  value  of  
ERM®-FA415ai  and  its  uncertainty  are  traceable  to  the  International  System  of  Units  (SI),  via  the 
master  batch  ERM®-FA415s  of  a  similar  nominal  absorbed  energy  by  testing  test  pieces  of  ERM®-
FA415ai  and  ERM®-FA415s  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  test  pieces  (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 = 39. 

1 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 

 
 
 
 
Table of contents 

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

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

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

1 

Introduction ............................................................................................ 5 

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

3  Processing .............................................................................................. 7 

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

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

6  Characterisation ..................................................................................... 9 

7  Value assignment ................................................................................. 12 

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

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

10 

Instructions for use .............................................................................. 13 

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

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

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

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

3 

 
 
 
 
 
Glossary 
AISI 
ASTM 
BCR 
BELAC 
CRM 
EC 
ERM® 
IEC 
IfEP 
IMB 
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 i 
n RM 

American Iron and Steel Institute 
American Society for Testing and Materials 
Community Bureau of Reference 
Belgian accreditation body 
Certified Reference Material 
European Commission 
European Reference Material 
International Electrotechnical Commission 
Institut für Eignungsprüfung GmbH 
International Master Batch 
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 test pieces of the Master Batch tested during certification of the 
Secondary Batch 
Number of test pieces of the Secondary Batch tested for certification  
Relative standard deviation 
Standard deviation 
Secondary Batch 
Standard deviation of the results of the test pieces tested to assess the 
homogeneity of the Secondary Batch  
Standard deviation of the nMB results of the test pieces of the Master Batch 
tested for the certification of the Secondary Batch  
Standard deviation of the nSB results of the test pieces 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 test pieces of the Master Batch 
tested when characterising the Secondary Batch  
Mean KV value of the nSB results of the test pieces 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 test piece is 
broken 
Degrees of freedom for uncertainty component i 
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 test piece 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  piece,  which  is  positioned  on  a  support  and  against  the 
pendulum anvils (not shown). The height reached by the hammer after having broken 
the  test  piece  (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 piece. 

The  energy  absorbed  by  the  test  piece  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 and the position of the anvils. 

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  Directorate  F  –  Health,  Consumers  and 
Reference  Materials  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-test pieces (
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  test 
pieces of the SB, is estimated by comparing the mean KV-value of a number of test 
pieces  of the  MB  ( MBX ), tested  together  with  the  SB  test  pieces  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. Procedures at the JRC allow a difference of 5 % (KVMB ≥ 40 J) or 
2 J  (KVMB  <  40 J)  between  KVMB  and 
MBX ,  corresponding  with  the  level  of  bias 
allowed for reference pendulums specified in  ISO 148-3 [9].  

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

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

CRM

 is 

KV
KV

MB

close to 1. Procedures at the JRC allow a difference of 20 % (KVMB ≥  40 J) or 10 J 
(KVMB <  40 J)  between  KVCRM  and  KVMB  to  ensure  that  the  MB  and  SB  test  pieces 
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 
measurement  uncertainty  of  the  values  MBX   and 
SBX   is  relatively  large.  However, 
(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 
SBX , 
uncertainty  components  do  not  contribute  to  the  uncertainty  of  the  ratio  MBX /
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®-FA415ai) test pieces was carried out by the Institut 
für Eignungsprüfung GmbH (IfEP), using ASTM 565 XM-32 steel delivered by Aubert 
& Duval (FR). The MB test pieces (ERM®-FA415s) used in the characterisation of the 
SB  were  provided  by  JRC,  Directorate  F  (Health,  Consumers  and  Reference 
Materials),  Geel  (BE).  The  homogeneity  of  the  SB  was  evaluated  based  on  data 
obtained at EC-JRC using a pendulum verified according to the criteria imposed by 
ISO 148-2 [1]. Characterisation of the SB was carried out at JRC 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  JRC.  The  certification  project  performed  was 
within the scope of an ISO Guide 34 accreditation (BELAC 268-RM). 

3  Processing 
The ERM®-FA415ai test pieces were prepared from bars of ASTM 565 XM-32 steel 
produced by Aubert & Duval (FR). Machining 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 
10 bars were cut into 990 Charpy test pieces but not yet 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 test pieces was performed at VTN Witten GmbH (DE) in a 
vacuum-furnace.  990  test  pieces  of  the  batch  were  heat-treated  according  to  the 
following procedure: 

Step 1: solution heat  treatment at 1040 °C for 30 minutes 
Step 2: quenching with nitrogen (8 bar) 
Step 3: first tempering at 695 °C for 120 minutes 
Step 4: cool down with nitrogen (8 bar) 
Step 5: second tempering at 660 °C for 120 minutes 
Step 6: cool down with nitrogen (8 bar) 

7 

 
 
 
 
The  test  pieces  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 test pieces were machined to the final dimensions specified 
in ISO 148-3 [9] by IfEP. During this process the test piece numbers were transferred 
to one of the end faces. Finally the test pieces were notched using a milling process. 

3.4  Quality control 
When all test pieces from the batch were fully machined, a selection of 25 test pieces 
was  made.  The  dimensions  of  the  25  test  pieces  were  checked  against  the  criteria 
+
00.0
30.00.55
 mm,  height  10.00  ±  0.06 mm,  width 
specified  in  ISO  148-3  [9]  (length 
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 test pieces was outside the ranges specified in ISO 148-3 [9].  

From the whole batch 62 test pieces were randomly selected and impact tested using 
a pendulum type Zwick PSW 750 (nominal energy 450 J), verified in 2014 according 
to ISO 148-2 [1]. 
The tests were performed on 10/03/2015. The results are reported in the production 
report  of  IfEP  [10].  The  average  KV  of  the  62  test  pieces  was  150.82  J,  which  is 
within the desired energy range (142.5 J - 157.5 J). The standard deviation of the test 
results  (s  =  5.31 J,  RSD  =  3.52 %)  was  above  the  3.3%  maximum  allowed  by  the 
contract,  but  lower  than  the  maximum  level  of  5%  allowed  by  ISO  148-3.  The 
variation was checked again during the characterisation tests at JRC (see Section 6). 

3.5  Packaging and storage 
Finally, the test pieces were cleaned and packed in sets of 5 randomised test pieces, 
in oil-filled and vacuum  sealed plastic bags. These oil-filled bags, were packed in a 
second  sealed  plastic  bag,  and  shipped  to the JRC  Geel.  After  arrival  (12/03/2015) 
the  925  test  pieces  (or  185  sets)  of  ERM®-FA415ai  were  registered  and  stored  at 
room temperature, pending distribution. 

4  Homogeneity 
The test pieces are sampled from the SBs, which should be sufficiently, but are never 
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 test pieces in the SB (test piece-to-test piece heterogeneity), 
but also depends on the number of test pieces over which the KV-value is averaged. 
ISO 148-2 [1] specifies 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 results obtained at EC-JRC on 

06/07/2016 (sh = 3.78 J). This leads to  

=

u

h

=

s

h
5

 1.69 J (1.11 %).  

As  is  required for  a  homogeneity  test, the  test  pieces  were  randomly  selected from 
the whole batch. The number of test pieces tested (30) is sufficiently large to reflect 
the homogeneity of the full SB (925 test pieces). 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 test pieces 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 test piece-to-test piece heterogeneity and 
the limited number of test pieces (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  the  JRC  using  batches  of  30,  80  and  120  J  from  the same  steel 
and  showed,  as  expected,  no  change  of  the  measured  values.  Uncertainty  of 
stabilities  for  120  months  were  calculated  as  0.7  J  -  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 [13]. 

treatment.  Annealing 

The main reason for the microstructural stability of the certified reference test pieces 
is  the  annealing  treatment  to  which  the  test  pieces  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®-FA415ai  was 
characterised on 06/07/2016, the validity of the certificate reaches until 7/2026.  

6  Characterisation 

6.1  Characterisation tests 
30 test pieces from ERM®-FA415ai (sets 7, 35, 87, 104, 138, 178) were tested under 
repeatability conditions together with 25 test pieces from MB ERM®-FA415s (sets 41, 
136,  163,  192,  219),  using  the Wolpert  PW30  machine  of  the  JRC,  Directorate  F  – 

9 

 
 
 
 
 
Health,  Consumers  and  Reference  Materials,  an  impact  pendulum  yearly  verified 
according to procedures described in ISO 148-2 [1].  
Tests  were  performed  on  06/07/2016  (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  test  pieces  show  'first-strike'  marks:  these  are  the  marks 
caused by the interaction between test piece and anvils during the first and intended 
hammer  impact.  Upon  fracture,  the  broken  halve  test  pieces  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  test  pieces  show  'second-strike'  marks.  These  are  marks  caused  by  a 
second  impact  of  the  already  broken  halve  test  pieces  back  onto  the  anvils.  This 
phenomenon has been described by Schmieder et al. [14]. None of the broken ERM-
FA415ai and none of ERM-FA415s test pieces showed second-strike marks.  

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.  

]
J
[

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

190

180

170

160

150

140

130

120

110

0

20

40
60
test sequence

80

100

Master batch
Secondary batch

Figure 3: Absorbed energy values of 30 test pieces of ERM®-FA415ai, compared 
with 25 test pieces of ERM®-FA415s; data are displayed in the actual test sequence. 

Table 1: Characterisation measurements of Batch ERM®-FA415ai 

Number of 
test pieces  

Mean value  

Standard 
deviation   

Relative 
standard 
deviation  

nMB , nSB 

SBX  

MBX  , 
[J] 

ERM®-FA415s (MB) 

ERM®-FA415ai (SB) 

25 

30 

162.01 

152.58 

10 

sMB , sSB 

RSDSB, RSDMB   

[J] 

4.95 

3.78 

[%] 

3.05 

2.47 

 
 
 
 
 
 
 
 
 
 
 
 
The  SB-results  meet  the  ISO 148-3  acceptance  criteria  for  a  batch  of  reference 
materials (sSB ≤ 2 J for KVSB < 40 J or ≤ 5 % for KVSB ≥ 40 J). 

6.2  Data from Master Batch ERM®-FA415s  
To  calculate  KVCRM  for  ERM®-FA415ai  one  needs  KVMB  of  the  MB  used,  i.e. 
ERM®-FA415s.  Table  2  shows  the  main  MB-data,  taken  from  the  Certificate  of 
Analysis of ERM®-FA415s (Annex 2). 

Table 2: Data from the certification of Master Batch ERM®-FA415s 

Certified 
absorbed energy 
of Master Batch 

Standard 
uncertainty of 
KVMB 

Relative standard 
uncertainty of 
KVMB 

KVMB (J) 

ERM®-FA415s 

157.3  

uMB (J) 

1.40 

uMB,rel (%) 

0.89 

6.3  Calculation of KVCRM and of uchar 
From  the  data  in  Table  1  and  Table  2,  and  using  Eq.  1,  one  readily  obtains  that 
KVCRM  =  148  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 

X

MB

SB / X

SBX  and  MBX were obtained under repeatability conditions. Therefore, the 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  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

11 

 
 
 
 
 
 
(cid:215)
(cid:215)
 
 
n
n
 
 
 
 
 
Table 3: Uncertainty budget for uchar for ERM®-FA415ai 

source of 
uncertainty 

measured 
value  

standard 
uncertainty 

probability 
distribution 

relative 
uncertainty 

KVMB  Certification of 

157.3  

(J) 

(J) 

1.4 

normal 

(%) 

0.89 

MB 

comparison of 
SB and MB in 
repeatability 
conditions 

SBX  

MBX

152.58 

0.69 

normal 

0.45 

162.01 

0.99 

normal 

uchar,rel (%) 

uchar (J) 

0.61 

1.17 

1.73 

degrees 
of 
freedom 

6 

29 

24 

16 

7  Value assignment  

7.1  Certified value, combined and expanded uncertainty 
As shown in 6.3, KVCRM = 148 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 = 39) 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 = 3.22% or  5 J) than the verification criterion of 4 J for KV < 40 J or 10 % for 
KV ≥40 J for industrial pendulums [1] or even 2 J for KV < 40 J or 5 % for KV ≥40 J  
for reference pendulums [9].  

Table 4: Uncertainty budget of KVCRM for ERM®-FA415ai 

source of uncertainty 

relative value ui 
(%) 

uchar 

characterisation of SB 

uh 

homogeneity of SB 

1.17 

1.11 

Combined standard uncertainty, uCRM (%) 

1.61 

Combined standard uncertainty, uCRM (J) 

2.39 

Expanded Uncertainty, k = 2, UCRM (%) 

3.22 

Expanded Uncertainty, k = 2, UCRM (J) 

5 

degrees 
of 
freedom 

16 

29 

39 

12 

 
 
 
 
 
 
 
 
 
 
 
 
8  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®-FA415s  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®-FA415ai is made traceable to the SI-traceable certified 
value  of  the  MB  by  testing  SB  and  MB  test  pieces  in  repeatability  conditions  on  an 
impact pendulum verified and calibrated with SI-traceably calibrated tools. Therefore, 
the certified value of ERM®-FA415ai is traceable to the International System of Units 
(SI) via the corresponding Master Batch ERM®-FA415s of a similar nominal absorbed 
energy. Absorbed energy KV is an operationally-defined measurand, and can only be 
obtained by following the procedures specified in ISO 148-1 [2].  

9  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]. 

10  Instructions for use 

10.1  Intended use 
Test  pieces  of  ERM®-FA415ai  are  ‘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  test  pieces  prior  to  the  tests.  It  is 
mandatory  to  remove  the  oil  from  the  test  piece  surface  prior  to  testing,  without 
damaging  the  edges  of  the  test  piece.  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 test piece clean. 

The following cleaning and conditioning procedure is considered to be good practice. 

1.  First  use  absorbent  cleaning-tissue  to  remove  the  excess  oil.  Pay  particular 
attention  to  the  notch  of  the  test  piece,  but  do  not  use  hard  (e.g.  steel) 
brushes to remove the oil from the notch. 

13 

 
 
 
 
 
 
 
2.  Apply  a  second  cleaning  step  with  organic  solvents.  Any  residual  solvents 
shall  be  removed  by  wiping  with  an  absorbent  tissue  before  proceeding  to 
step 3. 

3.  Once  samples  are  degreased,  only  manipulate  the  samples  wearing  clean 
gloves.  This  is  to  prevent  development  of  corrosion  between  the  time  of 
cleaning and the actual test. 

4.  Before  testing,  bring  the  test  pieces  to  the  test  temperature  (20  ±  2)  °C.  To 
assure  thermal  equilibrium  is  reached,  move  the  test  pieces  to  the  test 
laboratory at least 3 h before the tests. 

10.3   Pendulum impact tests 
After  cleaning,  the  5  test  pieces  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. 

14 

 
 
 
 
Acknowledgements 
The authors wish to thank K. Busschots, A. Held, R. Koeber and D. Florian (all JRC, 
Directorate  F-Health,  Consumers  and  Reference  Materials)  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 

in  measurement 

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

(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 piecesf 150 J nominal absorbed 
energy  ERM-FA415ai,  Institut  für  Eignungsprüfung  GmbH,  Marl  (DE),  12  March 
2015 

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. 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 

14. 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. 

16 

 
 
 
 
Annex 1 
Results  of  characterisation  measurements  of  ERM®-FA415ai  and  ERM®-FA415s  as 
measured according to ISO 148-1 at JRC Geel 06/07/2016. 

Master Batch ERM®-FA415s   Secondary Batch ERM®-FA415ai 

KV (J) 

155.06 
155.06 
151.26 
148.03 
154.09 
154.67 
151.16 
149.89 
145.98 
157.21 
148.13 
157.69 
149.01 
150.48 
153.70 
150.87 
153.01 
153.21 
147.45 
150.87 
153.11 
157.40 
146.67 
155.16 
155.94 
146.18 
156.82 
153.60 
160.03 
155.55 

152.58 

 3.78 

2.48 

KV (J) 

170.87 
156.72 
167.30 
162.65 
167.01 
166.82 
157.99 
157.11 
171.64 
159.35 
155.26 
163.14 
154.38 
164.69 
156.72 
165.17 
155.16 
167.50 
160.90 
163.82 
159.25 
164.01 
163.53 
157.69 
161.68 

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 (%) 

162.01 

 4.95 

3.05 

17 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Annex 2 

18 

 
 
 
 
 
 
 
 
 
 
 
19 

 
 
 
 
 
20 

 
 
 
 
European Commission 

EUR 29712 EN – Joint Research Centre – Directorate F – Health, Consumers and Reference Materials 
Title:   CERTIFICATION REPORT: The certification of the absorbed energy (150 J nominal) of Charpy V-notch 

reference test pieces for tests at 20 °C: ERM®-FA415ai 

Author(s): F. Vanderveken, A. Dean, G. Roebben 
Luxembourg: Publications Office of the European Union 
2019 – 20 pp. – 21.0 x 29.7 cm 
EUR – Scientific and Technical Research series – ISSN 1831-9424 
ISBN 978-92-76-01627-4 
doi: 10.2760/21196 

 
 
 
 
 
 
 
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. 

K
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doi: 10.2760/21196 

ISBN: 978-92-76-01627-4