Effect of Lateral Cracks on Fracture Toughness Determined by the Surface‐Crack‐in‐Flexure Method
Effect of Lateral Cracks on Fracture Toughness Determined by the Surface‐Crack‐in‐Flexure Method
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通过表面弯曲裂纹法测定横向裂纹对断裂韧性的影响
DOI：
10.1111/j.1151-2916.2002.tb00186.x
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
J. Salem
中科院分区：
文献类型：
--
作者：
G. Quinn;J. Salem
弯曲表面裂纹（SCF）方法使用努普压头在梁试样中产生小的半椭圆形表面预裂纹。横向裂纹会干扰一次中位裂纹，使断裂韧性的测定误差高达10%，特别是对于断裂韧性≤ 3 MPa·m1/2的材料。虽然残余应力损伤区可以用手工打磨或抛光，去除4.5-5倍压痕深度，该量可能不足以完全去除低断裂韧性材料中的横向裂纹。在压入后去除不同量材料的烧结α碳化硅上进行一系列测试。一旦横向裂纹完全消除，SCF结果与根据ASTM C1421标准收集的单边预裂纹梁和人字形缺口梁数据一致。SCF方法的一个简单的补救措施是在断裂前检查外地面是否有横向裂缝的残留物，并在必要时清除更多的材料。
The surface-crack-in-flexure (SCF) method uses a Knoop indenter to create small, semielliptical surface precracks in beam specimens. Lateral cracks may interfere with the primary median crack and cause errors of up to 10% in determination of fracture toughness, particularly for materials for which the fracture toughness is ∼3 MPa·m1/2 or less. Although the residual-stress-damage zone is ground or polished away by hand by removing 4.5–5 times the indentation depth, this amount may not be sufficient to completely remove the lateral cracks in low-fracture-toughness materials. A series of tests were conducted on sintered alpha silicon carbide with different amounts of material removed after indentation. Once the lateral cracks were fully removed, the SCF results concurred with single-edged-precracked-beam and chevron-notched-beam data collected in accordance with ASTM Designation C1421. A simple remedy for the SCF method is to examine the outer ground surface for remnants of lateral cracks before fracture and to remove more material if necessary.