Evaluation of Notch Geometry Design by Fracture Energy Method for Forgeability Test

以破壞能量法評估可成形性實驗試件之凹槽幾何設計

李榮顯(Rong-Shean Lee) ； 陳彥儒(Yen-Ju Chen)

《中國機械工程學刊》 29卷4期 (2008/08) Pp. 309-316

https://doi.org/10.29979/JCSME.200808.0005

摘要

在測定材料的可成形性時，圓柱壓縮實驗為常採用的實驗方式。但以此方式測試成形性非常良好的材料時，往往無法觀測到材料發生破壞的區域。而應用凹槽設計於圓柱試件上，將可提早使材料發生破壞。凹槽設計能加速破壞的原因，來自於凹槽尖端的應力集中與應變集中效應。因此透過適當的凹槽幾何設計，將可有效的加速材料破壞的發生。在本研究當中，以四個幾何參數來控制凹槽外形，並利用破壞能量準則來探討其效果。透過有限元素模擬可得到試件在變形過程中局部區域的應力、應變值，可用於計算材料至該變形階段累積的破壞能量值。由結果可知，良好的凹槽幾何會造成明顯的應力集中效應，也導致能量值提早到達破壞臨界點，有助於使材料發生破壞。最後，根據本研究結果可歸納出凹槽外形的設計法則，可用於設計不同加速破壞效果的凹槽試件。

並列摘要

Upsetting tests are widely used for forgeability test. When testing materials with high ductility, fracture may not occur on the specimen. Thus, it is necessary to improve the test method. Applying notch designs on upsetting test would accelerate the fracture initiation because of the stress concentration and strain concentration effects on the notch tip. In this research, the concentration effects are examined for different notch geometry parameters, including notch depth, notch tip radius, notch opening angle, and amount of notch. Through 3D finite element simulation, stress, strain and energy accumulation data are observed. The results showed energy accumulated most on the specimen that has high stress concentration effect. Finally, a notch design rule for high energy accumulation is recommended.

並列關鍵字

Notch geometry design ； Forgeability test ； Fracture energy method