Influence of microstructure and residual stresses on the fatigue behaviour of ribbed rebar rods

现代钢筋表面几何形状的引入影响了其疲劳性能。与光滑钢筋相比，疲劳强度降低，疲劳试验结果的分散性增大。到目前为止，还没有对制造工艺、微观结构、残余应力、表面形状和所得性能之间的关系进行整体考虑。本研究项目旨在填补这一知识空白。钢筋（钢筋或环形材料）的疲劳性能不足或分散性很强，严重限制了混凝土结构的使用寿命。在制造过程中对钢筋进行特定的适配可以显著改善目前钢筋疲劳强度水平低且分散性大的现状。为了实现这一点，应全面分析制造工艺，确定与钢筋复杂表面几何形状相匹配的残余应力的方法，通过数值模拟描述残余应力的形成，创建钢筋的详细表面模型，多相钢筋的相关微观结构部分在动态和静态性能方面量化，以及混凝土钢筋的结构/力学行为，以及对其所有量化的影响和相应的几何形状的数值模拟。这应该能够缩小目前钢筋在制造、微观结构和性能之间关系方面存在的相当大的知识差距，并开发可靠的疲劳行为预测工具，并在此基础上开发专门的工具。定制钢筋。

The introduction of modern surface geometry for steel rebar has affected its fatigue behaviour. In comparison with smooth reinforcing steel, fatigue strength has decreased while the scatter of the results of fatigue tests has increased. A holistic consideration of the relationships between the manufacturing process, microstructure, residual stress, surface form and the resulting properties has not been made up to now. This research project aims to close this gap in knowledge.Reinforcing steel (rebar or ring material) with inadequate or strongly scattering fatigue behaviour severely restricts the service life of the concrete structure. A specific adaption of the reinforcing steel during the manufacturing process could significantly improve the current low level and large scatter of the fatigue strength of the reinforcing steel. To achieve this, the manufacturing process should be comprehensively analysed, the methods for determining residual stress matched to the complicated surface geometry of the reinforcing steel, the formation of residual stresses described by numerical simulations, detailed surface models of reinforcing steel created, the relevant microstructural parts of multi-phase reinforcing steel quantified with regard to dynamic and static properties, and the structural/mechanical behaviour of concrete reinforcement steel with all quantified effects thereon and the corresponding geometry numerically simulated. This should make it possible to close the considerable gaps in knowledge that currently exist for reinforcing steel with regard to the relationship between manufacturing, microstructure and properties, and to develop reliable tools for the prediction of fatigue behaviour and, based on this, to develop specifically tailored rebar.