Customer
Our client is a research and development centre specialising in the field of materials.
Tested product
Steel Test Pieces
The steel specimen is a characteristic sample of the material to be tested.
The purpose of the impact bending test is to determine the energy required to break the specimen, thus characterising the resilience of the material. The type of impact (force/displacement curve) can also be used to determine certain specific characteristics of the material.
The impact bending test can be performed at room temperature or with a temperature-conditioned specimen. For the same material, the variation of resilience as a function of temperature makes it possible to determine a curve corresponding to the evolution of the strength of this material as a function of its temperature.
Objective
Carry out impact bending tests on Charpy specimens in accordance with the standards NF EN ISO 148-1, NF EN ISO 148-2, NF EN ISO 148-3 and NF EN ISO 14556, with an automatic specimen temperature control system, from -180°C to +600°C.
Problematic issues
The problem with the Impact-Pendulum
- To ensure automated, precise and repeatable positioning of the specimen during the impact
- To ensure that the arm catches up after the impact so that the specimen is not retyped after the first impact (making the test null and void as it is impossible to study the specimen's falls)
- Ensure reliable and easily calibrated force/displacement measurement
- To facilitate the verification and calibration procedures of the pendulum impactor
The problem of the thermal chamber
Impact bending tests are performed according to standards. In the case of temperature tests, these standards impose a strict temperature setting and conditioning of the specimens: temperature regulation, location of the measurement, spacing between the specimens, transfer time between the thermal chamber and the pendulum.
Once the specimen has been heated, it must be installed on the pendulum and tested in less than 5 seconds after leaving the chamber.
Solution and result
Impact-pendulum
The specimen support is equipped with a centring device. This device places the test piece against the supports and ensures centring just before the impact. The test piece is centred by its notch.
The pendulum arm is associated with a motorised arm. This motorised arm follows (without touching it) the pendulum arm during the release and hangs it up on the fly. This motorised arm also allows the pendulum arm to be raised to the desired release height.
The machine is equipped with several control systems to check the geometry of the pendulum, its moment, the response of the load cell, allowing direct checks in accordance with the standard.
Thermal enclosure
LF Technologies has imagined and designed a thermal enclosure with a specimen conveyor. This conveyor makes it possible to respect the spacing between the specimens imposed by the standards.
The thermal chamber is also equipped with a system for transferring the specimen to the pendulum. This transfer system is a "scoop" that positions the specimen in the pendulum. The movements of the "shovel" and the pendulum are synchronised, thus ensuring a very short transfer time (time between the exit of the temperature conditioning and the shock less than 5 seconds).
The thermal chamber allows temperature regulation from -180 to +600°C while ensuring efficient temperature setting and transfer of the test specimens.
