Evaluation of Fabrication Method for Making Notches for Charpy V-Notch Impact Specimens

The effect of preparing the notches for Charpy V-Notch impact specimens is evaluated. Two methods of preparation are used for this evaluation. They are grinding and broaching. Impact specimens with two energy levels were used: low energy, 15 J (11 ft∙lbf) and high energy, 94 J (69 ft∙lbf). Twenty-four specimens of each level were made with ground notches and with broached notches. Each was tested with a calibrated impact tester. The material used for the specimens was AISI-4340 alloy steel. The notch characteristics were documented by the following methods: notch angles, notch radii, surface conditions, and near-surface microstructure. Other parameters documented for this study were the ligament thickness, specimen width, and specimen length. In addition, test conditions and results are provided as follows: test temperature, absorbed energy, and lateral expansion. Besides tabular data, photographs give views of the notch surface. Evaluation of the results indicated both types of notches gave equally consistent values, but the ground and broached values differed in their averages. Possible causes for this variation were differences in ligament sizes and bottom of notch radii, surface tears and shallow microstructural deformation in the case of the broached notches.