Li Ran, Wei Wenshu, Chen Rongming, Wu Mengyu, Lai Yuehua
Graduate School, China Coal Research Institute, Beijing, China.
State Key Laboratory of Intelligent Coal Mining and Strata Control, Beijing, China.
Sci Prog. 2024 Jul-Sep;107(3):368504241280872. doi: 10.1177/00368504241280872.
Accurately measuring the mechanical properties of high-strength stainless steels is of great significance for ensuring structural safety, predicting long-term performance and optimizing design. However, the standardized tensile test specimens used to obtain strength properties must be fabricated from bulk materials from an in-service structure or component, result in the loss of structural integrity or a reduction in remaining service life. Small punch tests require only miniscule material samples and are widely used to estimate in-service component material characteristics. This study performed small punch tests on three high-strength stainless steels-X17CrNi15-2, 15-5PH, and PH13-8Mo-to obtain the correlations between the small punch tests and the uniaxial tensile test results for each material. The estimated yield stresses obtained from the small punch tests were distributed within a factor of 1.5 on both sides of the unity line when compared with those obtained from the uniaxial tensile tests; the ultimate strength values estimated from the small punch tests correlated quite well with those obtained from the uniaxial tensile tests. An iterative finite element analysis was subsequently established to simulate the small punch tests and thereby obtain the coefficients for a Ludwik power law correlation representing the true stress-strain properties. The finite element predicted force-deflection curves agreed well with the small punch test results, which were also compared with the predictions obtained from empirical equations proposed in previous studies. Finally, the fracture mechanisms of the small punch test specimens were characterized through scanning electron microscopy, indicating that the dimple fracture mechanism dominated the failure mode. The results of this study are expected to inform the application of small punch test to evaluate in-service high-strength stainless steel materials.
准确测量高强度不锈钢的力学性能对于确保结构安全、预测长期性能和优化设计具有重要意义。然而，用于获取强度性能的标准化拉伸试验试样必须由服役结构或部件的块状材料制成，这会导致结构完整性丧失或剩余使用寿命缩短。小冲孔试验仅需要极小的材料样本，并且被广泛用于评估服役部件的材料特性。本研究对三种高强度不锈钢——X17CrNi15-2、15-5PH和PH13-8Mo——进行了小冲孔试验，以获得每种材料小冲孔试验与单轴拉伸试验结果之间的相关性。与单轴拉伸试验获得的屈服应力相比，从小冲孔试验获得的估计屈服应力在统一线两侧1.5倍的范围内分布；从小冲孔试验估计的极限强度值与单轴拉伸试验获得的极限强度值相关性很好。随后建立了迭代有限元分析来模拟小冲孔试验，从而获得代表真实应力-应变特性的Ludwik幂律相关性的系数。有限元预测的力-位移曲线与小冲孔试验结果吻合良好，还与先前研究中提出的经验方程的预测结果进行了比较。最后，通过扫描电子显微镜对小冲孔试验试样的断裂机制进行了表征，表明韧窝断裂机制主导了失效模式。本研究结果有望为小冲孔试验在评估服役高强度不锈钢材料方面的应用提供参考。
