This work objectively proposes and describes the development project of a Charpy Pendulum Testing Machine, which is a low-cost tool designed for the academic environment. The tool has been developed to be used in laboratories that perform mechanical tests of impact and also as a result of an important partnership between students and researchers from UMC and EPUSP.

1. Impact Instrumentation for educational purposes
Carlos H. D. Felisbino1
, Celso F. B. A. S. Lima1
, Douglas P. de Souza1
, Felipe G. Wynne1
, João R. Storto1
, Gustavo
M. Calixto2
IEEE Member, Jorge R. B. Garay1,2
IEEE Member
{carlosfelisbino, celsofb, douglasps, felipegw, joaors, jorgegaray}@umc.br, calixto@lsi.usp.br
1
Mogi das Cruzes University - UMC, São Paulo, SP, Brazil
2
Polytechnic School of the University of São Paulo - EPUSP
Abstract — This work objectively proposes and describes the
development project of a Charpy Pendulum Testing Machine,
which is a low-cost tool designed for the academic environment.
The tool has been developed to be used in laboratories that
perform mechanical tests of impact and also as a result of an
important partnership between students and researchers from
UMC and EPUSP.
Keywords — Instrumentation, education, Impact Test,
Materials, Charpy.
I. INTRODUCTION
Nowadays, there is a large demand for the development of
tools that assist the study, in laboratory, of new materials to be
used in engineering classes, as well as in tests and production
of products and materials. When studying materials, the urge
to know physical and mechanical features of these materials,
as well as to simulate application scenarios and classify them
regarding their function and properties, demands the use of
precision equipments, which are expensive, to perform tests,
and, between these, we can mention the Charpy Test.
Testing machines of Charpy dynamic impact that are
available in the marked are known for their effectiveness and
accuracy when in operation, however, as this tool is very
expensive, its use is restrict to research institutes and
industries that are able to pay for it, thus making it difficult for
academic environments with less resources. When studying
materials that are used in engineering, choosing the right type
to elaborate a project is very important and the final quality
depends on it; so, it is fundamental for the researchers and
students to know that they can count on the required tools to
help make this choice.
Studies using impact tools have started with low precision
versions, and techniques have been improved only after the
manufacturing period [1].
Although other impact tools can be considered as efficient
as Charpy, this one has been evaluated as high efficient and
has been quickly adopted by test laboratories, institutes and
research centers. Charpy test has been developed to determine
the energy that is absorbed by the material at the moment of
impact, simulating the real comportment of the tested
material's ductile-fragile fracture. The gravitational potential
energy absorbed by the tested material after the impact is
calculated by the initial height variation in which the hammer
has been positioned with the height reached after the fracture
of the specimen [2].
At the engineering and applications field, every project
must contain hardware elements that must be made of
materials that have been previously studied, tested and
compared to other materials, thus verifying if their mechanical
features are suitable for their application and purpose.
This work briefly and objectively describes the project and
evaluation of a low-cost Charpy Pendulum Testing Machine.
The tool has been suited to the limited space of academic
laboratories, but still maintaining its adequacy to current
standards for the production of tools used in impact tests.
This work is organized as following topics: In section II, is
presented an tool description. In section III, an Tool Details
and finally at section IV are the conclusion.
II. TOOL DESCRIPTION
Instrumentation projects require a formal and strict study
of each element and component that will be part of the tool.
The detailing and experience must generate specifications of
new components and useful models for new projects of low-
cost impact instrumentation.
The designed tool can be basically defined by four levels:
Processing, Sensing, Actuation and Control. The control level
is probably the most important and its role is to receive the
signs that are emitted by sensors, process them and quickly
generate the actuator action. Final flux and result can be
observed in a computer in order to be analyzed or can be
directly analyzed and processed by software. The equipment
expected performance is based on the following standards:
ABNT NBR ISO 148-1:2013, which describes the Charpy
pendulum impact test method [3], and ABNT NBR ISO 148-
2:2013, which describes the verification of the Charpy
pendulum impact testing machine [4].
III. TOOL DETAILS
Equipment components have been dimensioned based on
the efforts made in each one of the structures, as well as on the
easiness to obtain them in national market. The tool has been
projected using CAD and its components are described on
figure 1:
Figure 1: CAD project of the Charpy Testing Tool

2. Structure components, indicated on table 1, have been
mostly built using SAE 1020 steel. The cleaver has been made
using VC131 steel, and jambs using SAE 8640 steel. They
have all been thermally treated to ensure resistance and
durability. On protections, polycarbonate plates have been
used, which, besides their high mechanical resistance, make
the test visualization easier.
Table 1: Components
No. Piece No. Piece
1 Hammer 12 Protection
2 Cleaver 13 Structure
3 Coupling 14 Base
4 Rod 15 Jamb bracket
5 Coupling trigger 16 Jamb
6 Suspension bracket 17 Reducer
7 Crown 18 Steering wheel
8 Bushing 19 Chain
9 Angle limiter 20 Encoder bushing
10 Encoder bracket 21 Rod holder
11 Pinion
To ensure the control of the test variables, facilitate data
collection and precisely measure the energy involved in the
process, an Arduino prototyping board has been chosen, which
keeps the project at its low-cost goal and makes it accessible
to complementary researches.
In the project automation, besides using the micro
controller, a heat sensor has been also used to control test
accuracy at the range of 23±5 ºC. An incremental encoder of
600 pulses per rotation has been also implemented to measure
the angular displacement of the hammer, allowing to calculate
the energy that has been absorbed by the specimen. A LCD
display shows information and results to the equipment
operator.
The calculation of the energy that has been absorbed by
the analyzed material has been done based on the following
equation (1), where the strength (F) and length (L) of the rod
present fixed values in function of the project and angles (α e
β) are calculated from positions that are indicated by the
encoder.
IV. RESULTS AND DISCUSSION
The designed tool (figure 2) has been dimensioned to
produce 150J of energy, thus allowing tests using SAE 1045
steel, material that has been chosen for validation tests. Tests
using this material have been performed and they have
presented results with recurring errors inside of the values that
are indicated in the standard that describes the verification of
the Charpy testing machines.
Figure 2: Final version of Charpy tool
On table 2, it is possible to observe the values obtained in
validation tests, which have been compared to the calibrated
commercial tool that is made available by the Materials
(Metallurgical Engineering and Materials Laboratory)
laboratory of the Polytechnic School of the University of São
Paulo.
Tests
Number Temp (o
C). E. (J) Loss (J) C.E. (J)
1 21 23,73 8,22 15,53
2 21 23,73 8,22 15,53
3 21 18,37 7,68 10,17
4 21 20,34 8,76 12,14
5 21 21,68 7,81 13,48
6 21 19,02 8,13 10,82
7 21 21,01 8,61 12,81
Average 21 21,13 8,2 12,92
A large number of tests than the ones described on table 2
has been performed with the tool, obtained an average of
21,13 (J) for Loss, 8,20 (J) and 12,92(J) of adjusted power.
The results highlight the success of the project when validated
by standards NBR ISO 148-1:2013 and NBR ISO 148-2:2013,
as well as the tool low cost (US$700), equal to one-tenth of
the average values of equipments that are sold in national
market.
REFERENCES
1. FRANÇOIS, D., PINEAU, A. From Charpy to present impact testing.
2002. Ed. Elsevier Science and Esis , primeira edição. Oxford - UK,
Reino Unido.
2. SOUZA, Sérgio Augusto. Ensaios mecânicos de materiais metálicos.
1982. Editora Blucher, quinta edição. São Paulo - SP, Brasil, 2011.
Páginas 79 - 101.
3. ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR ISO
148-1:2013. Materiais metálicos - Ensaio de impacto por pêndulo
Charpy - Parte 1: Método de ensaio. Rio de Janeiro, 2013. Páginas 1 - 26
ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR ISO
148-2:2013. Materiais metálicos - Ensaio de impacto por pêndulo
Charpy – Parte 2: Verificação da máquina de ensaio. Rio de Janeiro,
2013. Páginas 1 – 44.