Low-Temperature Brittleness Testing

Principle of Low-Temperature Brittleness Testing

The test is conducted by cooling material samples to a given low temperature, followed by the sudden application of force, which is usually an impact or bending force. In materials, plastic deformation is no longer possible at sufficiently low temperatures, and the materials fracture or crack. The temperature at which a given percentage of the specimens fails under the effect of the applied test conditions is defined as the brittle temperature.

Test Procedure

The specimens are kept in low temperature chamber/bath, usually liquid nitrogen, or a refrigerated cooling apparatus, and cooled to the required temperature of the test. The specimen is then conditioned, and then an impact or deformation is applied to it with a calibrated test device. The outcome is normally expressed as the lowest temperature where no failure is observed or the level of temperature at which a specified failure rate is achieved.

Common Standards and Methods

To test low-temperature brittleness, standard procedures are normally carried out using the ASTM D746 testing on plastics and elastomers and the ISO 812 testing of rubber materials. These standards establish the dimensions of the specimens, conditioning durations, impact procedures, and failure levels that guarantee the repeatability and comparability of findings. 

Applications and Industry Use

The application of this testing is common in industries where materials are subjected to cold condition such as in the automobile parts like seals and hoses, aerospace materials, refrigeration systems, and in the oil and gas pipelines. Construction materials that are to be employed in cold areas and outside infrastructure are also necessary. Manufacturers use brittle testing to avoid failures in service, warranty, and manufacture of products that will not be subject to failure in extreme environments.

Importance of Quality Control and Material Selection

A very important element of quality assurance of material to be used in low-temperature service is brittleness testing. Early determination of possible failure temperatures allows manufacturers to choose the right materials, optimize the formulations, and be able to meet safety and performance requirements.