Plastic instability of mechanical bulging process, different from the traditional tube hydroforming, is developed for Zircaloy tube based on localized necking criterion. Based on the observation of published experiments of bulging, an elementary analyzed model of plastic deformation is proposed and applied for examining the variation of bulging process and its limitation. The developed model comprises two deformation regions, one is bulged part with friction effect and the other is flattened part but without friction effect. All mentioned process parameters, such as contact friction, material properties (strain hardening exponent and normal anisotropy), and process geometries conditions (tube radius and thickness), are taken into account for in such mechanical bulging model. Plastic instability in bulging is examined using localized necking criterion based on the proposed model. A published experiment was initially used to verify the present model. Then, the effects of process parameters on the variation of bulging limit are investigated. The developed model allowed us to better understand the failure mechanism through the localized necking criterion, and also can be defined as a sign of fracture for a bulged tube. Moreover, a proposal will be made to examine the limitation of bulging for practical needs.

基于局部颈缩判据，为Zircaloy管开发了不同于传统管液压成形的机械鼓胀工艺的塑性不稳定性。在观察已发表的胀形实验的基础上，提出了塑性变形的基本分析模型，并将其用于检验胀形过程的变化及其局限性。所开发的模型包括两个变形区域，一个是具有摩擦效果的凸出部分，另一个是没有摩擦效果的扁平部分。在这种机械膨胀模型中考虑了所有提及的工艺参数，例如接触摩擦，材料特性（应变硬化指数和法向各向异性）以及工艺几何条件（管半径和厚度）。基于所提出的模型，使用局部颈缩准则来检查凸出中的塑性不稳定性。最初使用已发布的实验来验证当前模型。然后，研究了工艺参数对膨胀极限变化的影响。开发的模型使我们能够通过局部颈缩标准更好地了解失效机理，并且还可以将其定义为膨胀管破裂的迹象。此外，将提出一项建议，以检查凸出的实际需求。也可以定义为鼓胀管破裂的迹象。此外，将提出一项建议，以检查凸出的实际需求。也可以定义为鼓胀管破裂的迹象。此外，将提出一项建议，以检查凸出的实际需求。