Andra, the French national radioactive waste management agency, is in charge of studying the disposal of high-level and long-lived intermediate-level waste (HLW and ILW-LL) in a deep geological repository. According to the reference concept, it is planned to encapsulate high-level waste in non-alloy P285NH steel overpacks before inserting them into horizontal steel cased micro-tunnels. This work is a part of the study about the long-term behavior of a welded steel overpack subjected to external hydrostatic pressure and several localized loading paths.

Indeed, the main objective of this work is to develop the most suitable model for non-alloy steel P285NH to be used in the prediction of the long-term overpack behavior. Dealing with a ductile steel, elastoplastic constitutive equations accounting for mixed nonlinear isotropic and kinematic hardening strongly coupled with ductile isotropic damage are adopted. They are formulated based on the classical thermodynamics of irreversible processes framework with state variables at the macroscopic scale, (Germain, 1973) (Lemaitre 1985, Saanouni 2012). In this paper, a new coupling formulation between the scalar isotropic ductile damage and the deviatoric and spherical part of the Cauchy stress and elastic strain tensors is proposed. In order to calibrate the developed model on P285NH steel, multiple tensile tests are performed using classical cylindrical specimens, notched specimens and double notched specimens. In the last part, some experimental fields are measured using digital image correlation. Application is made to a simplified overpack represented by thick walled cylinder subject to compressive loading path. A FEM (Finite Element method) crushing operation of an overpack’s cylindrical part has simulated and analysed.

法国国家放射性废物管理机构 Andra 负责研究深地质处置库中高放和长寿命中放废物（HLW 和 ILW-LL）的处置。根据参考概念，计划将高放废物封装在非合金 P285NH 钢外包装中，然后将其插入水平钢套管微型隧道中。这项工作是关于承受外部静水压力和几个局部加载路径的焊接钢外包装的长期行为研究的一部分。

事实上，这项工作的主要目标是为非合金钢 P285NH 开发最合适的模型，用于预测长期外包装行为。处理韧性钢，采用弹塑性本构方程考虑混合非线性各向同性和运动硬化与韧性各向同性损伤强耦合。它们是基于具有宏观尺度状态变量的不可逆过程框架的经典热力学制定的，(Germain, 1973) (Lemaitre 1985, Saanouni 2012)。在本文中，提出了标量各向同性韧性损伤与柯西应力和弹性应变张量的偏球部分之间的新耦合公式。为了在 P285NH 钢上校准开发的模型，使用经典圆柱试样、缺口试样和双缺口试样进行多次拉伸试验。在最后一部分，使用数字图像相关性测量了一些实验场。应用于以受压缩加载路径影响的厚壁圆柱为代表的简化外包装。对外包装圆柱形零件的 FEM（有限元方法）破碎操作进行了模拟和分析。