ratios of the area of cold-worked

worked zone in the centre. The ratios of the area of cold-worked zone to that of the whole section were varied from 0% (=not bent) to 100%. As an example, the shape and the test results for DR-l coupon are shown in Fig.3. Elongation was measured by wire strain gauges of 50mm gauge length. The test results are given in Table 2. Fig.4 shows the specimen ABR-l after the test.