A load calibration technique based on the plastic deformation of a ring specimen is described. The method is applicable to any size press at loads up to full capacity. The method consists of determining the true flow stress of a heat of material by compression of small ring specimens on a calibrated test machine and treating the geometric change of the ring mathematically. Larger rings from the same heat of material are then deformed in large industrial presses or smaller testing machines which are to be calibrated. The geometric changes in the ring specimen and the previously determined flow stress are treated by the same mathematical analysis to determine the deformation pressure and thus the deformation load. A comparison is made of the calibration from the ring cell with other calibrations already determined on a mechanical crank press and a hydraulic extrusion press. The ring cell is shown to yield highly accurate load information.

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