一种结合微束与相场法测定非晶二氧化硅韧性和极限强度的方法
A Combined Microbeam and Phase-Field Approach to Identify the Toughness and Ultimate Strength of Amorphous Silica
AI总结：
本研究结合微束试验与相场计算，提出测定非晶二氧化硅韧性和极限拉伸强度的新方法，可同时获取两类关键力学参数，弥补传统方法的局限。
AI中文摘要：
本研究提出了一种结合微束试验与相场计算的新方法，用于评估非晶二氧化硅（SiO$_2$玻璃）的韧性（以临界能量释放率$G_c$表征）和极限拉伸强度$σ_c$。相场计算无需预先指定明确的断裂面，为脆性断裂研究提供了数值途径，可追踪裂纹的萌生与扩展过程。研究人员通过聚焦离子束（FIB）铣削制备了单缺口微梁，以及全新设计的带有无缺口标距段的骨形微梁，在空气环境中开展弯曲试验，分别探测脆性断裂区和强度控制区的力学行为。两类几何结构均采用耦合相场公式的有限元分析（FEA）进行建模。研究测得$G_c = 5.1$~J/m$^2$（对应临界应力强度因子$K_{IC} = 0.61$~MPa$\cdot$m$^{1/2}$）、材料内禀长度尺度$\ell_c = 9.1$~nm，以及$σ_c = 6.8$~GPa，结果与此前报道的石英玻璃脆性性能一致。通过参数研究，明确了缺口几何形状对微梁断裂响应的影响，以及尺寸测量误差对韧性测定结果的作用。不同于仅能得到$K_{IC}$的传统微力学方法，本研究提出的微梁几何结构与相场结合的方法可同时获取$G_c$和$σ_c$，打通了脆性断裂表征与仅适用于韧性测试技术无法覆盖的强度控制区之间的壁垒。
英文摘要：
This work presents a new approach to evaluating the toughness, described by the critical energy release rate ($G_c$), and ultimate tensile strength ($σ_c$) of amorphous silica (SiO$_2$ glass), combining microbeam tests and phase-field calculations. The latter provides a numerical route to brittle fracture without prescribing explicit fracture surfaces \textit{a priori}, enabling crack initiation and propagation to be tracked. Single-notched microbeams and newly designed bone-shaped microbeams with a notch-free gauge section were fabricated by Focused Ion Beam (FIB) milling nd tested under bending in air, probing the brittle-fracture and strength-controlled regimes, respectively. Both geometries were modeled by Finite Element Analysis (FEA) coupled with a phase-field formulation. We found $G_c = 5.1$~J/m$^2$ (critical stress intensity factor $K_{IC} = 0.61$~MPa$\cdot$m$^{1/2}$), an intrinsic material length scale $\ell_c = 9.1$~nm, and $σ_c = 6.8$~GPa, consistent with previously reported brittle properties of silica glass. Through a parametric study, we show the effect of notch geometry on the fracture response of the microbeams and the impact of dimensional measurement error on the determined toughness. Unlike conventional micromechanical methods that yield only $K_{IC}$, our combined microbeam geometries and phase-field approach simultaneously deliver $G_c$ and $σ_c$, bridging brittle-fracture characterization and the strength-controlled regime inaccessible to toughness-only techniques.
