Toribio Jesús, Lorenzo Miguel
Fracture & Structural Integrity Research Group, University of Salamanca, E.P.S., Campus Viriato, Avda, Requejo 33, 49002 Zamora, Spain.
Materials (Basel). 2022 Dec 19;15(24):9085. doi: 10.3390/ma15249085.
The main cause of in-service failure of cold drawn wires in aggressive environments is hydrogen embrittlement (HE). The non-uniform plastic strains and residual stresses generated after cold drawing play a significant role in the matter of HE susceptibility of prestressing steels. In this paper, a new and innovative design of the drawing scheme is developed, geared towards the reduction in both manufacturing-induced residual stresses and plastic strains. To achieve this goal, three innovative cold drawing chains (consisting in diverse multi-step dies where multiple diameter reductions are progressively carried out in a single die) are numerically simulated by the finite element (FE) method. From the residual stress and plastic strain fields revealed from FE numerical simulations, hydrogen accumulation for diverse times of exposure is obtained by means of FE simulations of the hydrogen diffusion assisted by stress and strains. Thus, an estimation of the HE susceptibility of the cold drawn wires after each process was obtained. Results reveal that cold drawn wire using multi-step dies exhibits lower stress and strain states nearby the wire surface. This reduction causes a decrease in the hydrogen concentration at the prospective damage zones, thereby improving the performance of the prestressing steel wires in hydrogenating environments promoting HE. Thus, the optimal wire drawing process design is carried out using special dies with several reductions per die.
在侵蚀性环境中，冷拉钢丝服役失效的主要原因是氢脆（HE）。冷拉后产生的不均匀塑性应变和残余应力在预应力钢的氢脆敏感性问题中起着重要作用。本文开发了一种全新的创新拉拔方案设计，旨在减少制造过程中产生的残余应力和塑性应变。为实现这一目标，采用有限元（FE）方法对三种创新的冷拉链条（由不同的多步模具组成，在单个模具中逐步进行多次直径减小）进行了数值模拟。根据有限元数值模拟揭示的残余应力和塑性应变场，通过应力和应变辅助的氢扩散有限元模拟，获得了不同暴露时间下的氢积累情况。由此，得到了每个工艺后冷拉钢丝氢脆敏感性的估计值。结果表明，使用多步模具的冷拉钢丝在钢丝表面附近呈现出较低的应力和应变状态。这种降低导致潜在损伤区域的氢浓度降低，从而提高了预应力钢丝在促进氢脆的氢化环境中的性能。因此，使用每个模具具有多次缩径的特殊模具进行了最佳拉丝工艺设计。
