To date, the complex behaviour of small punch creep test (SPCT) specimens has not been completely understood, making the test hard to numerically model and the data difficult to interpret. This paper presents a novel numerical model able to generate results that match the experimental findings. For the first time, pre-strained uniaxial creep test data of a P91 steel at 600 ∘C have been implemented in a conveniently modified Liu and Murakami creep damage model in order to simulate the effects of the initial localised plasticity on the subsequent creep response of a small punch creep test specimen. Finite element (FE) results, in terms of creep displacement rate and time to failure, obtained by the modified Liu and Murakami model are in good agreement with experimental small punch creep test data. The rupture times obtained by the FE calculations which make use of the non-modified creep damage model are one order of magnitude shorter than those obtained by using the modified constitutive model. Although further investigation is needed, this novel approach has confirmed that the effects of initial localised plasticity, taking place in the early stages of small punch creep test, cannot be neglected. The new results, obtained by using the modified constitutive model, show a significant improvement with respect to those obtained by a ’state of the art’ creep damage constitutive model (the Liu and Murakami constitutive model) both in terms of minimum load-line displacement rate and time to rupture. The new modelling method will potentially lead to improved capability for SPCT data interpretation.

中文翻译：

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P91钢小冲头蠕变试样初始塑性的实验与数值分析

迄今为止，尚未完全了解小冲头蠕变试验 (SPCT) 试样的复杂行为，这使得该试验难以进行数值模拟且数据难以解释。本文提出了一种新的数值模型，能够生成与实验结果相匹配的结果。首次在方便修改的 Liu 和 Murakami 蠕变损伤模型中实现了 P91 钢在 600 ∘C 下的预应变单轴蠕变试验数据，以模拟初始局部塑性对后续蠕变响应的影响。小冲头蠕变试样。有限元 (FE) 结果，在蠕变位移率和失效时间方面，由改进的 Liu 和 Murakami 模型获得，与实验小冲头蠕变试验数据非常吻合。使用非修正蠕变损伤模型的有限元计算获得的破裂时间比使用修正本构模型获得的断裂时间短一个数量级。虽然需要进一步研究，但这种新方法已经证实，在小冲头蠕变试验的早期阶段发生的初始局部塑性的影响不容忽视。通过使用修改后的本构模型获得的新结果与通过“最先进”蠕变损伤本构模型（Liu 和 Murakami 本构模型）获得的结果相比，在最小载荷线位移方面都有显着改进破裂的速度和时间。新的建模方法可能会提高 SPCT 数据解释的能力。