金屬薄板液壓膨脹實驗之設備研發與其應用

Abstract

在工業製造上，金屬薄板在成形過程中所受的應力狀態多半為雙軸向應力，如深引伸成形(deep drawing)、張出成形(stretching)、伸緣成形(stretch flange)和應用逐漸成熟之液壓成型(hydroforming)等。因此，能夠精確地描述在此受力狀態下金屬薄板的應力-應變曲線(stress-strain curve)便顯得十分重要。另外，由於近年來電子消費性產品在外殼等部位之尺寸越來越精密且微小，於是了解尺寸效應(size effect)對金屬薄板強度之影響也是必需的研究。 本研究針對本實驗室現有之液壓膨脹實驗(bulge test)專利設備進行實用性方向之改善與後續應用。首先利用油壓缸改善試片夾持力不足之問題，使操作流程更簡單及實用；並使用不同的退火時間與溫度，對純銅金屬薄板進行退火，取得不同晶粒大小之金屬薄板，並利用改進之設備對其進行液壓膨脹實驗，探討尺寸效應對金屬薄板強度之影響，以期建立金屬薄板成形製程設計之依據。

Today, there are increasing applications in the industry involving the deformation of sheet metals, especially thin sheet metals. In the industrial practice, the stress of sheet metals is mostly in the multi-axial state during forming process. Therefore, it is very important to accurately describe the stress-strain curve of the sheet metals in the complex stress state. In addition, because the size of the modern application products is getting smaller than before, the size effect on the strength of sheet metals is becoming significant. This research focused on the development and application of a novel hydraulic bugle test apparatus for obtaining thin sheet metals properties. To investigate the size effect on strength of sheet metals, this apparatus was used with specimens which have different grain size and thickness. Different diameters of upper mold of our apparatus were also used. A complete stress-strain relationship of thin sheet metal concerning size effect were obtained.