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

现代钢筋表面几何结构的引入影响了钢筋的疲劳性能。与光滑钢筋相比，疲劳强度降低，疲劳试验结果的散点增大。到目前为止，还没有全面考虑制造工艺、微观结构、残余应力、表面形状与所得性能之间的关系。这个研究项目旨在弥补这方面的知识差距。钢筋（钢筋或环材）散射疲劳性能不充分或散射疲劳性能强，严重制约了混凝土结构的使用寿命。在制造过程中对钢筋进行特殊的调整，可以显著改善目前钢筋疲劳强度水平低、分散大的现状。为实现这一目标，应全面分析制造过程，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，建立详细的钢筋表面模型，对多相钢筋的相关显微组织部件进行动态和静态性能量化，并对混凝土钢筋的结构/力学行为进行了量化，并对相应的几何形状进行了数值模拟。这将有可能缩小目前在钢筋制造、微观结构和性能之间的关系方面存在的相当大的知识差距，并开发可靠的工具来预测疲劳行为，并在此基础上开发专门定制的钢筋。

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.