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Mechanical Approach to Fracture Toughness Improvement for High Strength Steel and Its Weld HAZ by Controlling Morphology of Microstructure

通过控制显微组织形态提高高强度钢及其焊接热影响区断裂韧性的机械方法

基本信息

批准号：
07555666
负责人：
TOYODA Masao
金额：
$ 1.15万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1997
项目状态：
已结题

项目摘要

This study discussed the transfer of local stress fields in microstructures to fracture property evaluation of structural steels. Initiation behavior of brittle microcrack in dual-phase steels was mainly focused. The Weibull stress employed in the local approach is available for the evaluation of fracture driving force of each microstructure in dual-phase steels. The idea in this procedure is the integration of local stress in the microstructure responsible for fracture initiation. The local stress in dual-phase steels can be different considerably from a macroscopic stress obtained from the global analysis of specimen. Generally, the high-strength phase bears larger stress than the low-strength phase, which means that fracture property evaluation based on the global stress field is not always reliable. The local stress in the microstructure is affected by the morphology of second phase and matrix. Increase in strength and slenderness of hard phase leads to elevation of fracture driving force of the hard phase. The stresses in low-strength phase can be relaxd to a large extent, provided that the low-strength phase is enclosed by the high-strength phase. These microscopic characteristics of stress fields are important in the fracture control design of structural steels. The Weibull stress is expected as a measure to link between microscopic and macroscopic aspects of fracture.

本研究探讨了结构钢显微组织中局部应力场向断裂性能评价的转移。重点研究了双相钢中脆性微裂纹的萌生行为。局部方法中的Weibull应力可用于双相钢中各微观组织的断裂驱动力的评估。在这个过程中的想法是局部应力的微观结构中负责断裂引发的集成。双相钢中的局部应力可能与从试样的整体分析得到的宏观应力有很大差异。通常，高强度相比低强度相承受更大的应力，这意味着基于全局应力场的断裂性能评估并不总是可靠的。显微组织中的局部应力受第二相和基体形貌的影响。硬质相强度和伸长的增加导致硬质相断裂驱动力的提高。只要低强度相被高强度相包围，低强度相的应力可以得到很大程度的松弛。应力场的这些微观特征在结构钢的断裂控制设计中是重要的。威布尔应力预期作为连接断裂的微观和宏观方面的量度。