In-situ heating and cooling of Charpy test specimens

This paper presents an innovative approach to CVN and MCVN testing: the specimens are heated and cooled on the test machine itself. This approach is not only cost-effective but is technically superior to methods requiring transfer of the test specimen to the test machine from a thermal conditioning bath because the specimen is very accurately centered and is thermally conditioned up to the moment of impact. The system developed is capable of thermally conditioning both CVN and MCVN specimens over the temperature range of -180 degreesC less than or equal to T less than or equal to 315 degreesC. Advanced systems are under development which will extend this temperature range. This paper presents data obtained using the in-situ heating and cooling system and compares the results with specimens which were heated and cooled using a liquid bath transfer approach. Specimens instrumented with embedded thermocouples were used to characterize the heat loss during bath transfer and to compare with the uniform temperature field produced by the in-situ system. Measurements are also presented which show a factor-of-two improvement in specimen alignment can be easily achieved with the in-situ system centering tool.