先進高強度鋼在不同應變率下力學行為之研究──實驗與模擬

Investigate on Mechanical Behavior of Advanced High Strength Steel Under Various Strain Rates -Experiment and Numerical Simulation

隨著材料科技之進步，各類先進高強度鋼（advanced high strength steel, AHSS）已陸續開發，由於其兼具了較高的強度和延展性等優點，因此常被用於耐撞結構元件設計。為了評估此一結構承受動態荷重時的力學行為，掌握鋼片在不同應變率下的行為是十分重要的。本研究針對DP590與DP980兩種先進高強度鋼的力學行為進行了研究，擬靜態與中應變率試驗是利用MTS高速伺服式油壓試驗機進行，高應變率的實驗則是採用了分離式霍普金森拉桿試驗機（split Hopkinson tensile bar, SHTB）進行試驗。其次，本研究亦針動態拉伸試驗所得到之資料，分別進行了Cowper-Symonds以及Johnson-Cook兩種材料組成律係數的分析與計算，並結合商用非線性有限元素分析程式，針對實驗設置與條件進行模擬，比較了應用不同組成律所得結果與實驗之間差異。 With the progresses in materials science and technology, many kinds of advanced high strength steel (AHSS) have been gradually developed. Because of AHSS with both advantages of high strength and ductility, it is often used for structural elements crashworthiness design. In order to precisely evaluate the mechanical behavior of steel structures under various dynamic loads. It is paramount to understand the behavior of stress-strain for steel pieces under various strain rates testing. In this study, two kinds of dual phase steel (DP590 and DP980) at different strain rates were investigated. Quasi-Static and intermediate strain rates tests were carried out using an MTS high-speed servo-hydraulic machine, whereas used split Hopkinson tensile bar (SHTB) was used for tensile testing at high strain rates. Then, these materials properties were investigated to calculate the parameters of Cowper-Symonds and Johnson-Cook constitutive model. Furthermore, authors used commercial finite element analysis software LS-DYNA to perform some calculations based on the experimental setup and compared these results with stress-strain curves obtained from the tests.