National Magnetic Confinement Nuclear Fusion Energy Development Research Project. 2022YFE03120001 National Atomic Energy Agency Nuclear Materials Technology Innovation Center. ICNM-2023-ZH-07
Lead-cooled fast reactor is a promising reactor type of the fourth-generation reactors. In the design of the cladding material, it is necessary to pay attention to the compatibility of the cladding material with the molten Pb-Bi alloy, and its resistance to liquid metal corrosion, especially, the properties of structural materials will be significantly degraded by the synergistic action of corrosive molten Pb-Bi alloy and external stress. The Small Punch Test (SPT) is a testing method, that uses a small size sample to assess the changes in the mechanical properties of a structural material in service conditions. This method can extract samples directly from the structural material in use without compromising its integrity. Therefore, the SPT is very suitable for situations where the number of materials under study is limited or where materials in service are studied. This paper briefly introduces the SPT technique, summarizes the research on the correlation between the SPT and the standard size test at home and abroad, expounds the research on mechanical properties of key materials by using small punch technique, especially expounds the application of SPT in the study of liquid metal embrittlement effect (LME) of structural materials. The results can provide technical methods and theoretical support for the application of small punch technique in the study of liquid Pb-Bi alloy induced embrittlement of engineering materials.
Keywords：small punch test (SPT)
;
structural material
;
mechanical property
;
liquid metal embrittlement (LME)
HE Yajie, CHEN Lingzhi, RUAN Zhangshun, FU Xiaogang, JI Cheng, LONG Bin. Progress of Small Punch Test Technique and Its Application in Detecting Embrittlement Effect of Molten Lead-bismuth on Metallic Materials. Journal of Chinese Society for Corrosion and Protection[J], 2024, 44(3): 567-575 DOI:10.11902/1005.4537.2023.207
其中，TCVN是使用有2 mm V形缺口的10 mm × 10 mm × 55 mm标准试样进行的Charpy冲击实验得到的韧脆转变温度，TSPT是使用10 mm × 10 mm × 0.5 mm样品进行小冲杆实验得到的韧脆转变温度，比例因子α取决于小样品的几何形状、材料类别、拟合程序和TCVN的定义标准，一些学者研究得到α的值在0.32~0.45之间[20,21]。Altstadt等[22]使用SPT研究了辐照后钢的韧脆转变温度，结果表明SPT实验可以作为监测RPV钢辐照脆化的辅助技术，辐照后材料的关系式比例因子取值也在未辐照材料的α值范围内，即根据 式(1)可以有效地估计DBTT的变化，拟合数据得到下式：
Fig.4
SEM fracture images of a SPF test on a Ti-6Al-4V specimen: (a) macro fracture of SPT test sample, (b) fatigue fringe of uniaxial strain fatigue test sample, (c, d) fracture strip of SPT test sample[26]
Fig.8
Load-displacement curves (a) and fracture images (b, c, d) of T91 steel in oxygen saturated LBE at 300oC under the loading rates of 0.05 mm/min (b1, b2), 0.005 mm/min (c1, c2) and 0.0005 mm/min (d1, d2)[4]
Fig.9
SPT curves of T91 steel at 250oC (a) and 300oC (d), and fracture surface morphologies (b, c, e, f) for DNO2 (b), D0.5O2 (c) and D4O2 (e) oxidized at 300oC, and for DAO2 oxidized at 250oC (f)[32]
Effect of specimen thickness and punch diameter in evaluation of small punch test parameters toward characterization of mechanical properties of Cr-Mo steels
Small specimen mechanical testing is an exciting and rapidly developing field in which fundamental deformation behaviours can be observed from experiments performed on comparatively small amounts of material. These methods are particularly useful when there is limited source material to facilitate a sufficient number of standard specimen tests, if any at all. Such situations include the development of new materials or when performing routine maintenance/inspection studies of in-service components, requiring that material conditions are updated with service exposure. The potentially more challenging loading conditions and complex stress states experienced by small specimens, in comparison with standard specimen geometries, has led to a tendency for these methods to be used in ranking studies rather than for fundamental material parameter determination. Classifying a specimen as ‘small’ can be subjective, and in the present work the focus is to review testing methods that utilise specimens with characteristic dimensions of less than 50 mm. By doing this, observations made here will be relevant to industrial service monitoring problems, wherein small samples of material are extracted and tested from operational components in such a way that structural integrity is not compromised. Whilst recently the majority of small specimen test techniques development have focused on the determination of creep behaviour/properties as well as sub-size tensile testing, attention is given here to small specimen testing methods for determining specific tensile, fatigue, fracture and crack growth properties. These areas are currently underrepresented in published reviews. The suitability of specimens and methods is discussed here, along with associated advantages and disadvantages.
WangZ X, ShiH J, LuJ, et al.
Small punch testing for assessing the fracture properties of the reactor vessel steel with different thicknesses
... [4]Load-displacement curves (a) and fracture images (b, c, d) of T91 steel in oxygen saturated LBE at 300<sup>o</sup>C under the loading rates of 0.05 mm/min (b1, b2), 0.005 mm/min (c1, c2) and 0.0005 mm/min (d1, d2)<sup>[<xref ref-type="bibr" rid="R4">4</xref>]</sup>Fig.8
... [5]Load-displacement curves of unirradiated and neutron-irradiated T91 steel at 200<sup>o</sup>C<sup>[<xref ref-type="bibr" rid="R5">5</xref>]</sup>Fig.5
... SPT标准贯入实验常用试样有圆形、方形和矩形，尺寸范围分别为：直径3~8 mm，厚0.05~0.5 mm；10 mm × 10 mm，厚0.25~0.5 mm；10 mm × 4 mm，厚0.25~0.5 mm[8].试样厚度对SPT得到的载荷-位移曲线有显著影响.相比于较厚的试样，较薄的试样曲线显示出较不明显的线弹性阶段、较小的最大载荷和较低的延展性.薄样品在实验过程中经历更多的弹性弯曲，而厚样品经历更为显著的塑性变形[8].因此，需要规定一个试样厚度范围，以获得材料唯一的SPT载荷-位移曲线[9,11,12]，标准化技术可以解决样品厚度不同导致的问题.标准化有两种方式，第一种方式是使初始刚度、屈服载荷、峰值载荷分别与规定试样厚度标准化，得到幂律标定关系[13]；第二种方式，使用具体表达式，将载荷-位移曲线标准化为0.5 mm厚度样品对应的曲线[14].值得注意的是，两种方式在文献中使用的材料和测试装置之外的有效性必须得到验证.Wang等[15]通过理论模型得到厚度对断裂应变和断裂韧性的影响：断裂应变和断裂韧性随试样厚度的增加而增加. ...
Effect of specimen thickness and punch diameter in evaluation of small punch test parameters toward characterization of mechanical properties of Cr-Mo steels
Application of ball punch tests to evaluating fracture mode transition in ferritic steels
1
1991
... 其中，TCVN是使用有2 mm V形缺口的10 mm × 10 mm × 55 mm标准试样进行的Charpy冲击实验得到的韧脆转变温度，TSPT是使用10 mm × 10 mm × 0.5 mm样品进行小冲杆实验得到的韧脆转变温度，比例因子α取决于小样品的几何形状、材料类别、拟合程序和TCVN的定义标准，一些学者研究得到α的值在0.32~0.45之间[20,21].Altstadt等[22]使用SPT研究了辐照后钢的韧脆转变温度，结果表明SPT实验可以作为监测RPV钢辐照脆化的辅助技术，辐照后材料的关系式比例因子取值也在未辐照材料的α值范围内，即根据 式(1)可以有效地估计DBTT的变化，拟合数据得到下式： ...
Assessment of the constitutive properties from small ball punch test: experiment and modeling
1
2004
... 其中，TCVN是使用有2 mm V形缺口的10 mm × 10 mm × 55 mm标准试样进行的Charpy冲击实验得到的韧脆转变温度，TSPT是使用10 mm × 10 mm × 0.5 mm样品进行小冲杆实验得到的韧脆转变温度，比例因子α取决于小样品的几何形状、材料类别、拟合程序和TCVN的定义标准，一些学者研究得到α的值在0.32~0.45之间[20,21].Altstadt等[22]使用SPT研究了辐照后钢的韧脆转变温度，结果表明SPT实验可以作为监测RPV钢辐照脆化的辅助技术，辐照后材料的关系式比例因子取值也在未辐照材料的α值范围内，即根据 式(1)可以有效地估计DBTT的变化，拟合数据得到下式： ...
Use of the small punch test for the estimation of ductile-to-brittle transition temperature shift of irradiated steels
1
2021
... 其中，TCVN是使用有2 mm V形缺口的10 mm × 10 mm × 55 mm标准试样进行的Charpy冲击实验得到的韧脆转变温度，TSPT是使用10 mm × 10 mm × 0.5 mm样品进行小冲杆实验得到的韧脆转变温度，比例因子α取决于小样品的几何形状、材料类别、拟合程序和TCVN的定义标准，一些学者研究得到α的值在0.32~0.45之间[20,21].Altstadt等[22]使用SPT研究了辐照后钢的韧脆转变温度，结果表明SPT实验可以作为监测RPV钢辐照脆化的辅助技术，辐照后材料的关系式比例因子取值也在未辐照材料的α值范围内，即根据 式(1)可以有效地估计DBTT的变化，拟合数据得到下式： ...
... [26]SEM fracture images of a SPF test on a Ti-6Al-4V specimen: (a) macro fracture of SPT test sample, (b) fatigue fringe of uniaxial strain fatigue test sample, (c, d) fracture strip of SPT test sample<sup>[<xref ref-type="bibr" rid="R26">26</xref>]</sup>Fig.4
Load-displacement curves of SPT samples of T91 steel treated at 300<sup>o</sup>C in air (a) and LBE (b)<sup>[<xref ref-type="bibr" rid="R29">29</xref>]</sup>Fig.7
Load-displacement curves of SPT samples of T91 steel treated at 300<sup>o</sup>C in air (a) and LBE (b)<sup>[<xref ref-type="bibr" rid="R29">29</xref>]</sup>Fig.7
... [29]Load-displacement curves of SPT samples of T91 steel treated at 300<sup>o</sup>C in air (a) and LBE (b)<sup>[<xref ref-type="bibr" rid="R29">29</xref>]</sup>Fig.7
SPT curves of T91 steel at 250<sup>o</sup>C (a) and 300<sup>o</sup>C (d), and fracture surface morphologies (b, c, e, f) for DNO2 (b), D0.5O2 (c) and D4O2 (e) oxidized at 300<sup>o</sup>C, and for DAO2 oxidized at 250<sup>o</sup>C (f)<sup>[<xref ref-type="bibr" rid="R32">32</xref>]</sup>Fig.9
