BeginnerTopic 11 of 100Materials & Chemical
Impact testing
Charpy test measures toughness and ductile-to-brittle transition.
In depth
Charpy and Izod tests swing a pendulum to break a notched bar, measuring absorbed energy. Ductile-to-brittle transition temperature (DBTT) is key for BCC steels in cold service (e.g. Liberty ships, Titanic steel). FCC metals do not show DBTT.
Key points
- Notch sensitivity
- Fracture surface appearance
- Low-temperature steels with nickel
ExamplePipeline steels are specified with minimum Charpy energy at -20 °C.
Impact tests reveal whether a material will fail suddenly in cold service, which is critical for pressure vessels, ships and bridges.
What is Impact testing?
Charpy test measures toughness and ductile-to-brittle transition.
Why is it important to understand impact testing?
Impact tests reveal whether a material will fail suddenly in cold service, which is critical for pressure vessels, ships and bridges.
What does a Charpy test measure?
The energy absorbed when a notched bar is struck by a pendulum, which indicates toughness at the test temperature.
What is the ductile-to-brittle transition?
A temperature range where the impact energy drops sharply, and steels below this temperature can fracture with little plastic deformation.
How is Impact testing used in practice?
Typical applications include checking that a steel plate has enough toughness at minus 20 degrees for a ship hull, specifying the Charpy energy for a pipeline steel and investigating a brittle fracture in a cold climate structure.
What should I learn before Impact testing?
Study "Tensile testing" first (topic 10 of 100 in Materials & Chemical). It covers the groundwork this topic builds on.
What are the key points of Impact testing?
Notch sensitivity. Fracture surface appearance. Low-temperature steels with nickel.
Can you give an example of Impact testing?
Pipeline steels are specified with minimum Charpy energy at -20 °C.
What comes after Impact testing?
The next topic is "Strengthening mechanisms", which builds directly on this one.
How difficult is Impact testing?
It is classed as Beginner in Materials & Chemical (topic 11 of 100). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.