中文摘要：

成形极限图（FLD）反映了板料在各种应变路径下的应变极限，是综合衡量板料成形性能的一个重要指标。在用半球形凸模进行试验时发现，所用凸模直径和试件形状的不同对FLD有影响。采用两种不同直径的凸模和两组不同形状的试件进行了试验，获得了4种情况下的FLD，对比分析了凸模大小和试件形状对试验结果的影响。结果表明：采用直径较大的凸模得出的FLD低于采用小直径的凸模得到的FLD，试件形状对于FLD的左半部影响较大，中间带圆弧形的试件得出的FLD左半部低于中间部分平行的试件得到的FLD，试件形状对右半部FLD没有影响。

英文摘要：

A formation limit diagram （ FLD）, which shows the strain limit of sheet metals under various strain conditions, is an important indicator for assessing sheet metal formation performance. An experiment with hemispheric punches reveals that the difference in their diameters and the specimen shape has some influence on FLD. Two kinds of punches with different diameters and two groups of specimens of different shapes were used in the experiment. Thus the FLDs under four conditions were obtained, and the influence of the size of punch and the spape of specimen on experimental results was contrasted. The results indicate that the FLD obtained from the punch of larger diameter is lower than that from the punch of smaller diameter. The Specimen shape has bigger influence on the left half of FLD, which, when obtained from the specimen with arc in the middle, is lower than that of the FLD from the specimen which is parallel in the middle. The specimen shape has no influemce on the right half.