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The need for a tight squareness tolerance (90° ±10 min) of adjacent sides of Charpy V-notch impact specimens has been questioned by Quality Assurance personnel in the metals industry. An experiment has been designed to evaluate the effect of the squareness tolerance greater than required in ASTM E23-93a, Standard Test Methods for Notched Bar Impact Testing of Metallic Materials . Material used to manufacture impact standards of low, high and super high energy levels was heat-treated, and the notched surface and surface opposite the notch were machined to 90° +20 min, 90° +40 min and 90° +60 min. The sides adjacent to the notch were held flat and parallel. A control set of samples was machined to meet current squareness requirements given in ASTM E 23. The results were statistically analyzed. The analysis shows when out-of-squareness is ⩾ 20 min, energy ranges, mean energy values and associated standard deviations at the low and high energy levels are statistically different when compared to the same information derived from SRMs.
impact energy, low energy, high energy, super high energy, jamming, squareness tolerance, SRM specimens, spinning and tumbling, statistical analysis, t-Test
Research Engineer, Homer Research Laboratories, Mechanical Test Lab, Bethlehem Steel Corporation, Bethlehem, PA