【作者】 林兵；

【导师】 陆光闾；

【作者基本信息】 上海交通大学 ， 固体力学， 2007， 博士

【摘要】 预应力钢丝(钢绞线)广泛地应用于预应力混凝土结构中。本论文主要通过数值计算和试验方法研究了应力(包括外部施加应力和残余应力)对预应力钢丝的断裂性能和腐蚀的影响,其内容主要包括下面三个方面:1.残余应力对开裂预应力钢丝断裂性能的影响预应力钢丝在冷拔时产生的拉残余应力对其断裂性能会产生有害影响。在本论文中利用有限元分析,断裂发生的微观力学模型和J-Q理论,定性地研究了纵向残余应力对开裂预应力钢丝断裂性能的影响,并与不考虑残余应力时的情况进行了比较,结果表明:拉残余应力可以通过改变裂尖约束来减少了预应力钢丝的断裂韧度。2.外部施加应力对预应力钢丝临界氯离子浓度的影响一方面当混凝土中的氯离子浓度达到其临界值时,钢筋表面的钝化膜便会破坏,从而导致钢筋发生腐蚀;另一方面当作用于预应力钢丝的外部施加应力超过弹性极限时,预应力钢丝便会发生塑性变形。为了评价预应力钢丝的塑性变形对其临界氯离子浓度的影响,采用恒电流阳极极化技术作为加速试验方法,调查了具有不同氯离子浓度的饱和氢氧化钙溶液中受轴向拉力作用的预应力钢丝的坑成核电位。试验结果表明:当预应力钢丝中的应力超过弹性极限时,其临界氯离子浓度值比其应力低于弹性极限时的小,而造成这种现象的主要原因是由于塑性变形不但降低了碱性环境下影响钝化膜形成的预应力钢丝的电极电位,而且增强了预应力钢丝坑蚀的敏感性。3.外部施加应力对预应力钢丝氢脆敏感性的影响氢脆是预应力钢丝的主要腐蚀形式之一,而预应力钢丝中的应力水平对其氢脆的敏感性有直接的影响。通过实施耦合扩散的弹塑性有限元分析,来获得平面应变条件下带有凹口的预应力钢丝中氢浓度的分布。结果表明外部施加应力对预应力钢丝中氢浓度的分布会产生影响,而且外部施加应力存在一个“临界值”,当超过此值时,预应力钢丝中的氢浓度随应力的增加而急剧增加。更多还原

【Abstract】 Prestressing steel wires（steel strands） are widely used in prestressed concrete structures. In this paper, the effects of stresses （including applied stresses and residual stresses） on the fracture behavior and corrosion of prestressing steel wires are investigated by numerical calculation and experimental method. The main contents are listed as follows:1.The effect of residual stresses on the fracture behavior of cracked prestressing steel wiresResidual stresses,generated by cold-drawn operations in prestressing steel wires,may have detrimental effects on the fracture behavior of the prestressing steel wires. Using finite element analysis,micromechanical models of fracture initiation and J-Q theory,this paper focuses on the qualitative effect of the longitudinal residual stresses on the fracture behavior of cracked prestressing steel wires,and the results have been compared with those obtained from the steel wires without residual stresses. It has been concluded that the tensile residual stresses can reduce the fracture toughness of prestressing steel wires by altering crack-tip constraint.2.The effect of applied stresses on the critical chloride concentrations of prestressing steel wiresOn the one hand,the presence of sufficient chloride ions in concrete causes breakdown of the passive films on the steel surface and leads to corrosion of the steel,on the other hand,when the applied stress exceeds the elastic limit,the plastic deformation of the prestressing steel wire is produced. To evaluate the effect of the plastic deformation on the critical chloride concentration of prestressing steel wires,the pit nucleation potential of the prestressing steel wire has been investigated by galvanostatic polarization technique as accelerated experiment method in saturated Ca（OH）₂ solutions. The experimental results indicated that,when the stress exceeds the elastic limit,the critical chloride concentration of prestressing steel wires is lower than that when the stress is within the elastic limit. This could be attributed to the plastic deformation decreased the electrode potential of prestressing steel wires, which can affect the formation of passive films in the alkaline environment, and enhanced the pitting corrosion susceptibility.3 . The effect of applied stresses on the hydrogen embrittlement susceptibility of prestressing steel wiresHydrogen embrittlement is one of the main corrosion forms of prestressing steel wires,and the stress level in prestressing steel wires has a direct effect on hydrogen embrittlement susceptibility. Coupled diffusion elastic-plastic finite element analysis was implemented in order to obtain the hydrogen concentration distribution in the notched prestressing steel wire under plane strain conditions. The results showed that applied stress has an effect on the hydrogen concentration distribution,and the applied stress has a“critical value”. When the applied stress exceeds this value,the hydrogen concentration in the prestressing steel wire will sharply increase following the stress.更多还原