Charpy impact test method for metallic materials is specified by European EN 10045 standard.
This specification defines terms, dimension and tolerances of test pieces, type of the notch (U or V), test force, verification of impact testing machines etc.
The test consists of breaking by one blow from a swinging pendulum, under conditions defined by standard, a test piece notched in the middle and supported at each end. The energy absorbed is determined in joules. This absorbed energy is a measure of the impact strength of the material.
Charpy impact test method for metallic materials is specified
by European EN 10045 standard. This specification defines
terms, dimension and tolerances of test pieces, type of the
notch (U or V), test force, verification of impact testing
machines etc.
For certain particular metallic materials and applications,
Charpy impact test may be the subject of specific standards
and particular requirements. The test consists of breaking
by one blow from a swinging pendulum, under conditions
defined by standard, a test piece notched in the middle and
supported at each end. The energy absorbed is determined in
joules. This absorbed energy is a measure of the impact
strength of the material.
The designations applicable to this standard are as
indicated in the Table 1 and on the Figure1.
Table 1. Characteristics of test piece and testing
machine
|
Reference (Figure 1)
|
Designation
|
Unit
|
|
1
|
Length of test piece
|
mm
|
|
2
|
Height of test piece
|
mm
|
|
3
|
Width of test piece
|
mm
|
|
4
|
Height below notch
|
mm
|
|
5
|
Angle of notch
|
Degree
|
|
6
|
Radius of curvature of base of notch
|
mm
|
|
7
|
Distance between anvils
|
mm
|
|
8
|
Radius of anvils
|
mm
|
|
9
|
Angle of taper of each anvil
|
Degree
|
|
10
|
Angle of taper of striker
|
Degree
|
|
11
|
Radius of curvature of striker
|
mm
|
|
12
|
Width of striker
|
mm
|
|
-
|
Energy absorbed by breakage KU or KV
|
Joule
|
Figure 1. Charpy impact test
Test pieces
The standard test piece shall be 55 mm long and of square
section with 10 mm sides. In the centre of the length, there
shall be a notch. Two types of notch are specified:
- V notch of 45°, 2 mm deep with a 0,25 mm
radius of curve at the base of notch. If standard test piece
cannot be obtained from the material, a reduced section with
a width of 7,5 mm or 5 mm shall be used, the notch being cut
in one of the narrow faces.
- U notch or keyhole notch, 5 mm deep, with 1 mm
radius of curve at the base of notch. The test pieces shall
be machined all over, except in the case of precision cast
foundry test pieces in which the two faces parallel to the
plane of symmetry of the notch can be unmachined.
The plane of symmetry of the notch shall be perpendicular to
the longitudinal axis of the test piece.
The tolerances of the specified dimensions of the test piece
are given by standard as well. For the standard test piece,
machining tolerance in length is 0.6 mm for both type of
tests, and tolerances in height are 0.11 mm for U and 0.06 mm
for V notch test piece. Tolerances for angle between plane of
symmetry of the notch and longitudinal axis of test piece as
well as for angle between adjacent longitudinal faces of
test piece are ± 2° only.
Comparison of results is only of significance when made
between test pieces of the same form and dimensions.
Machining shall be carried out in such a way that any
alternation of the test piece, for example due to cold
working or heating, is minimized. The notch shall be
carefully prepared so that no grooves, parallel to the base
of the notch, are visible to the naked eye. The test piece
may be marked on any face not in contact with the supports
or anvils and at a point at least 5 mm from the notch to
avoid the effects of cold working due to marking.
Testing machine
The testing machine shall be constructed and installed
rigidly and shall be in accordance with European Standard
10 045 part 2.
Standard test condition shall correspond to nominal machine
energy of 300±10J at the use of a test piece of standard
dimensions. The reported absorbed energy under these conditions
shall be designated by the following symbols:
- KU for a U notch test piece
- KV for a V notch test piece
Testing machines with different striking energies are
permitted, in which case the symbol KU or KV shall be
supplemented by an index denoting the energy of the testing
machine.
For example KV 150 denotes available energy of 150 J, and KU
100 denotes available energy of 100 J. KU 100 = 65 J means
that:
- nominal energy is100 J
- standard U notch test piece is used
- energy absorbed during fracture is 65 J.
For tests on a subsidiary V notch test piece, the KV symbol
shall be supplemented by indices denoting first the
available energy of the testing machine and second the width
of the test piece, e.g.:
- KV 300 / 7,5: available energy 300 J, width of test
piece 7.5 mm
- KV 150 / 5: available energy 150 J, width of test piece 5 mm
- KV 150 / 7,5 = 83 J denotes:
- nominal energy 150 J
- reduced section test piece of width 7,5 mm
- energy absorbed during fracture: 83 J.
The test piece shall lie against the anvils in such a way
that the plane of symmetry of the notch shall be no more than
0.5 mm from the plane of symmetry of the anvils. If the test
temperature is not specified in the product standard, it
shall be about 23°C.
National standards corresponding to EN 10045-2 are DIN 51306
(1983), NFA 03-508 (1985), BS 131 Part 4 (1972) and
international ISO 442 (1965).