Using Digital Image Correlation Method in the Strain Field Measurements of Advanced High Strength Steel

• Main Authors: Chien-Wei Liao, 廖建為
• Other Authors: Kuan-Ming Li
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/75890276252681066635

碩士 === 國立臺灣大學 === 機械工程學研究所 === 103 === In recent years, automobile industries have being dedicated to improve the fuel efficiency by using advanced high strength steels in vehicles structural parts. However, increasing the strength steels leads to a limited formability and high tendency to springback. On the other hand, the hot stamping process becomes an effective solution. Because of the transformation of microstructure to martensite during the die-quenching process leading to an ultimate strength up to 1,500 MPa. Forming Limit Curve(FLC) is an important material property for CAE simulations of hot stamping. However, the traditional grid method is not applicate in high temperature environments. Digital Image Correlation (DIC) is a non-contact method for strain measurement. Therefore, this study aim to explore the application of 3D Digital Image Correlation (DIC) method to establish FLC. Advantages of DIC is the simplicity of experiment setup and providing accurate full field strain distribution. In this research, the self-developed DIC code on Matlab is also developed to find the displacement and strain fields. Experiments in this thesis are divided to two parts: using DIC to obtain 3D Forming Limit Curve in room temperature and using DIC to obtain 2D strain field in 800˚C tensile deformation. By using DIC, the FLD of the 590Y and 1180Y high strength steel and the stress-strain curve of the 15B22 coated steel strips in high temperature are established.