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Micromechanical Simulation of Initiation and Propagation of Cleavage Cracks in the Ductile-brittle Transition Region

韧脆转变区解理裂纹萌生和扩展的微观力学模拟

基本信息

批准号：
269292404
负责人：
Privatdozent Dr.-Ing. Geralf Hütter
金额：
--
依托单位：
Institut für Mechanik und Fluiddynamik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/269292404?language=en
关键词：
Micromechanical Simulation Initiation Propagation Cleavage

项目摘要

With decreasing temperature typical engineering materials like the most steels become more and more brittle. The reason is the transition of the microscopic failure mode from ductile growth of micro-voids to transgranular cleavage of grains. The drop of the macroscopic fracture toughness caused by the transition from the ductile to the brittle mechanism is a severe problem in engineering applications of body-centered cubic metals since crack-like defects formed during manufacturing or in operation may reduce strength and life-time of a component significantly. In the ductile-brittle transition region the measured fracture toughness values of single crystals and poly-crystals differ by several orders. To the knowledge of the authors no model can explain this discrepancy yet. It is the aim of the present research project to contribute significantly to the understanding of this phenomenon. For this purpose a micromechanical FEM model shall be developed which resolves the microstructure of a ferritic steel at the crack tip discretely in form of particles (segregations, inclusions) and grains. Within different stages of extension of the model the effects of the relevant submechanisms like debonding of particles, fracture of particles, dislocation pile-up at grain boundaries and particles and incompatibility of cleavage planes of neighboring grains shall be investigated and quantified. On this basis the microstructure shall be optimized to increase the fracture toughness.

随着温度的降低，典型的工程材料（如大多数钢）变得越来越脆。其原因是微观破坏模式由孔洞的韧性增长向晶粒的穿晶解理转变。体心立方金属在制造或使用过程中形成的裂纹状缺陷会显著降低构件的强度和寿命，因此由韧性向脆性转变所引起的宏观断裂韧性下降是体心立方金属工程应用中的一个严重问题。在韧脆转变区，单晶和多晶的断裂韧性值相差几个数量级。据作者所知，还没有模型可以解释这种差异。本研究项目的目的是为理解这一现象做出重大贡献。为此，应开发微观力学FEM模型，该模型以颗粒（偏析、夹杂物）和晶粒的形式离散地解析裂纹尖端铁素体钢的微观结构。在模型扩展的不同阶段，应研究并量化相关子机制的影响，如颗粒脱粘、颗粒断裂、晶界和颗粒处的位错堆积以及相邻颗粒解理面的不相容性。在此基础上，优化组织结构，提高断裂韧性。