论文标题
格里菲斯理论对理想材料的理论强度预测的失败
Failure of Griffith Theory on Prediction of Theoretical Strength of Ideal Materials
论文作者
论文摘要
自从出版以来，格里菲斯理论是最广泛使用的标准，用于根据材料是否包含裂纹来估算材料的理想强度和破裂强度。 Griffith强度极限为〜E/9是理想材料强度的上限。随着制造样品的提高质量和计算建模的力量，人们最近报告了超出格里菲斯理论预测的理想强度的可能性。在这项研究中，基于热力学系统的稳定分析建立了新的强度标准。然后，使用第一原理密度功能理论（DFT）来研究沿[100]，[110]和[111]低索引晶体学方向的单轴拉伸负荷下的四种材料（钻石，C-BN，CU和CEO2）的理想强度。通过比较DFT结果与Griffith理论之间的理想优势，发现Griffith理论在所有四种材料中都失败了。对断裂机制的进一步分析表明，格里菲斯理论的失败是因为理想强度点与创建新表面无关，这违背了格里菲斯的假设，即裂纹一直存在于本质上。故障点对应于传播开始时的裂缝。
Ever since its publication, the Griffith theory is the most widely used criterion for estimating the ideal strength and fracture strength of materials depending on whether the materials contain cracks or not. A Griffith strength limit of ~E/9 is the upper bound for ideal strengths of materials. With the improved quality of fabricated samples and the power of computational modeling, people have recently reported the possibility of exceeding the ideal strength predicted by the Griffith theory. In this study, a new strength criterion was established based on the stable analysis of thermodynamical systems; then first-principles density functional theory (DFT) is used to study the ideal strength of four materials (diamond, c-BN, Cu, and CeO2) under uniaxial tensile loading along the [100], [110], and [111] low-index crystallographic directions. By comparing the ideal strengths between DFT results and the Griffith theory, it is found that the Griffith theory fails in all the four materials. Further analysis of the fracture mechanism demonstrates that the failure of the Griffith theory is because the ideal strength point does not correspond to creating of new surfaces, which is against the Griffith assumption that the crack intrinsically exists all the time; the failure point corresponds to the crack at the start of propagation.
