基于粘塑性统一本构和曲率积分的中厚板热矫直多尺度变形行为研究

Hot straightening is an important finishing process. At present, with the continuous improvement of the sheet strength and the popularity of the controlled cooling process, the plate defects caused during the production process rise sharply. Demands for the regulation of hot straightening process increase quickly. Meanwhile, the effects of straightening process on the microstructure also urgently need to be integrated into the overall plate property control system. However, there is lack of hot straightening model and theory, which can describe and analyze the macro and micro scale deformation behavior finely. According to the unique plastic deformation characteristics of hot plate straightening process, namely the hot deformation under low temperature, small deformation, and cyclic tension-compression loading, we aim to solve two key scientific problems. One is the multiphase materials unified visco-plasticity constitutive expression under cyclic tension-compression loading. Another one is the plate curvature integral during non-isothermal visco-plasticity bending process. Thereby, the plate deformation behavior related to the strain rate, temperature distribution, and microstructural evolution during hot straightening process can be analyzed effectively. Finally, the plate multi-scale deformation behavior and law during hot straightening process can be explored. The integrated prediction and analysis of parameters for the macro, microscopic and microscopic evolution will be realized. It lays theoretical foundation for the shape-property precise regulation and control, and its integration with the overall microstructure and properties control system during the plate hot straightening process.

中厚板热矫直是板材生产过程中一道重要的精整工序。当前随着板材强度的不断提高和控冷工艺的普遍应用，其生产过程中的缺陷水平大幅上升，对热矫直过程的调控要求越来越高；同时矫直过程对板材微观组织性能的影响也使其迫切需要被纳入到板材整体组织性能控制体系中去。然而目前尚缺乏对板材宏微观各尺度变形行为进行精细化描述和分析的热矫直模型及其理论。本课题拟针对热矫直低温热变形、小变形量、循环拉压加载的独特塑性变形特征，通过解决复相材料循环拉压加载过程的粘塑性统一本构表征；板材非等温连续弹-粘塑性反弯过程的曲率积分求解这两大关键科学问题，实现对热矫直过程多尺度变形行为的有效分析。最终探明板材热矫直过程中与应变速率、温度分布和微观结构演化相关的变形行为与变形规律，实现各尺度描述参数的联合预测与分析，为热矫直过程板材形性联合精准调控及其与整体组织性能控制体系的融合奠定理论基础。

中厚板热矫直是板材生产过程中一道重要的精整工序。当前随着板材强度的不断提高和控冷工艺的普遍应用，其生产过程中的缺陷水平大幅上升，对热矫直过程的调控要求越来越高，因此需要对板材热矫直过程中宏微观各尺度的变形行为进行精准的分析和研究。不同于大多数的塑性成形过程，板材热矫直过程是一种具有低温热变形、小变形量、循环拉压加载这些独特变形特征的塑性成形过程，该过程中材料微观组织结构的演化、循环载荷下的粘塑性变形行为及宏观尺度下板材的弯曲特性和曲率形态演化规律等问题都需要建立相应的理论模型进行描述。本项目对中厚板热矫直过程中的多尺度变形行为进行了系统性研究。在材料微观尺度上，设计了能够准确复现热矫直过程的材料循环拉压实验并基于此对各种不同热矫直条件下的材料微观组织形态演化过程进行了分析，建立了能够描述典型中厚板材料热矫直循环拉压加载变形过程的材料粘塑性统一本构模型，实现了中厚板材料矫直循环加载过程中粘塑性变形特性的表征。在板材宏观尺度上，建立了能够准确表达板材截面热-力耦合与材料粘塑性行为的考虑温度和应变速率的截面弯曲数值求解模型及能够进行复杂板形缺陷分析的中厚板动态矫直过程曲率积分模型，获得了精细化描述和分析中厚板热矫直过程热变形行为的宏观力学工具。通过本项目的研究，获得了中厚板宏观形性参数随热矫直过程工艺参数的演变规律及不同热变形条件下的中厚板热矫直过程的微观组织演变规律，较为完整地揭示中厚板热矫直过程中各个尺度的变形行为与变形规律，为热矫直过程的精准调控及其与前后工序的联合分析奠定了基础。