Quantitative Comparison and Evaluation of Various Notch Machining Methods and How They Affect ASTM E23 and ISO R442 Testing Equipment Results

The differences obtained when conducting Charpy impact tests using an ASTM method E23 specification, versus the ISO type impact tester have been reported with little agreement upon the comparisons. There has also been historically much controversy as far as the proper method of machining the notch into the Charpy specimen. This paper compares the effects of the two different types of impact testing equipment and evaluates machining of the notch by the methods of grinding, broaching and milling with a single toothed fly cutter.

It was determined that results obtained with the ISO type impact machine were elevated by approximately 4%. It was also determined that a slightly lower impact value was obtained with broached specimens. Photomicrographs of typical notch profiles were also obtained.