A method used to evaluate the impact toughness or resistance to brittle fractureA sudden and catastrophic failure of a pipeline due to the propagation of a brittle crack. It occurs when the pipeline material experiences low-temperature cond… of materials to ensure pipelines remain crackA fracture or discontinuity in the wall of a pipeline, where the material is separated or broken, potentially compromising the integrity and safety of the pipel… resistant. The "20" refers to the temperature at which the test is conducted, typically -20°C (-4°F).