Calibration of pendulum impact testers

Calibrating as per the MSZ EN ISO 148-2 international standard includes the determination of the following metrological parameters:

• reduced pendulum length
• drop height
• reduced mass of hammer
• initial static energy of hammer
• striking speed
• static energy value at the individual points of the scale

For the determination of these metrological parameters, the device is inspected as per the following main categories:

• Inspection of scaffolding
• Inspection of the seats and the test specimen grippers
• Inspection of the pendulum
• Inspection of the indicating structure

WORTH KNOWING...

Impact tests can be distinguished by two different methods, depending on where and how the test specimen is struck.

In a CHARPY SYSTEM impact test, the test specimen, like a two-post bracket, is placed horizontally on the impactor and the pendulum strikes the side opposite the incision.

In an IZOD SYSTEM impact test, the test specimen is fixed to the machine in a vertical position as a rod clamped at one end, the incision facing the direction of impact and the pendulum measuring the impact at the protruding end of the test specimen.

IMAGE 1: Pendulum impact test

A LITTLE THEORY...

Impact test
The results of fracture mechanics tests are used to assess the safety against brittle fracture.
We differentiate four main groups within the fracture mechanics tests:

• Comparative tests with constant state determinants based on the energy required to break a standardized test specimen.
• Examination of the energy required for the fracture as a function of state determinants.
• Determination of the condition determinants required to start or stop a crack.
• Determining characteristics suitable for sizing that reveal the correlation between the external allowable stress and a tolerable crack size at constant and structure-specific state determinants.

The impact test can be used to determine the characteristics included in the first group. That is, the standardized impact-bending test can be used to determine the impact energy (KV, KU).

Impact energy is used to determine the toughness order of tough materials (e.g. stainless steels, core of hardened insert steels…).

Constant state determinants are as follows:
ambient temperature, approx. 20 C.
loading speed:
Velocity of the standardized pendulum
The stressed state is determined by the size of the specimen and the standard incision.

„U” incision test
„V” incision test

Results can only be compared if recorded with the same type of test body.