ISO 148-1: Charpy impact test on metals
The ISO 148-1 standard specifies the Charpy (U-notch and V-notch) impact test on metals for determination of the impact strength. The impact strength of a material is an important characteristic for applications in pipeline construction and shipbuilding.
The test method is also described and determined in ASTM E23. The ISO standard is identical to the European standard (EN ISO 148-1).
Objective Running the test Specimen measurements Temperature controlled tests Automation Testing systems
Objective of the Charpy impact test
The objective of the Charpy impact test to ISO 148-1 is the determination of the impact energy and determination of the impact strength of a metal. The test indicates whether the metal is tough or brittle.
In addition, the tough/brittle transition can be determined based on the temperature.
Impact strength is a material characteristic value. Metals with high impact strength can absorb shock and impact energies without breaking. This type of test is often used in the steel industry during the manufacturing of pipes as well as for the inspection of pipes.
How is an impact test to ISO 148-1 performed?
In a Charpy impact test to ISO 148-1, a notched metal specimen is severed using a pendulum hammer. For the test, the metal specimen is centered on the supports in the pendulum impact tester. The notch is exactly across from the point at which the pendulum hammer strikes the specimen. This impact test is used to determine the absorbed impact energy.
Since the impact energy on metals if often temperature dependent, a test temperature of 23 °C is specified for Charpy impact tests at ambient temperature. Deviating test temperatures are permitted under standard-compliant conditions. Often Charpy impact tests are performed at low temperatures. These temperatures are usually at minus 20 °C and minus 40 °C.
Specimen dimensions to ISO 148-1
The ISO 148-1 standard specifies the dimensions for a so called normal specimen:
- Length: 55 mm
- Width (designation in ISO 148 Series prior to 2016 was “height”): 10 mm
- Thickness (designation in ISO 148 Series prior to 2016 was “width”): 10 mm
If a normal specimen cannot be produced from the material to be tested, the specimen can also have a thickness of 7.5 mm, 5.0 mm or 2.5 mm. These specimens are considered as undersized specimens.
The notch must be placed in the center of the length as a V or U.
Charpy impact tests under temperature conditions
If the Charpy impact test is performed at a test temperature that deviates from ambient temperature, no more than 5 seconds may elapse between removal of the specimen from the temperature conditioning vessel and the impact of the hammer on the specimen. In addition, you must ensure that the temperature of the specimen does not change during transport to the pendulum impact tester. For this purpose, the standard recommends temperature-conditioned, self-centering tongs. For larger specimen batches, an automated testing system can be used for transport and automatic testing of the specimens.
Automated Charpy impact tests
Charpy impact tests can also be automated. An automated solution provides the benefit of eliminating operator influences such as hand temperature or moisture and off-center or angled specimen insertion, which in turn results in high reproducibility of the test results. Automatic alignment of the specimens with the supports and starting the test via the testing system also ensures reliable and reproducible results.
The robotic testing system roboTest I supports the user in the performance of Charpy impact tests to ISO 148-1 or ASTM E23. The system can be used to automatically test up to 450 notched metal specimens in a temperature range of -180 °C to +300 °C. A solid and insulated temperature conditioning unit ensures uniform and accurate specimen temperature.
After the required tempering time has elapsed, the specimens are moved one after the other from the temperature conditioning device to their test position where they are automatically aligned and impacted. The test is performed within 5 seconds of removing the specimen from temperature conditioning unit.
For all robotic testing systems, the autoEdition3 automation software is used for information input and control.
