ASTM E2899-15
測量拉伸和彎曲狀況下表面裂紋起裂韌度的標準試驗方法

Standard Test Method for Measurement of Initiation Toughness in Surface Cracks Under Tension and Bending

被代替

標準號

ASTM E2899-15

發布

2015年

發布單位

美國材料與試驗協會

替代標準

ASTM E2899-19

當前最新

ASTM E2899-24e1

 

 

引用標準

ASTM C1421 ASTM E1012 ASTM E111 ASTM E1820 ASTM E1823 ASTM E1921 ASTM E399 ASTM E4 ASTM E6 ASTM E647 ASTM E740 ASTM E8/E8M

適用范圍

5.1 Surface cracks are among the most common defects found in structural components. An accurate characterization and understanding of crack-front behavior is necessary to ensure successful operation of a structure containing surface cracks. The testing of laboratory specimens with surface cracks provides a means to understand and quantify surface crack behavior, but the test results must be interpreted correctly to ensure transferability between the laboratory specimen and the structure.

5.2 Transferability refers to the capacity of a fracture mechanics methodology to correlate the crack-tip stress and strain fields of different cracked bodies. Traditionally, the correlation has been based on the presence at fracture of a dominant, asymptotically singular, crack-tip field with amplitude set by the value of a single parameter, such as the stress intensity factor, K_I, or the J-integral. For components and specimens with high crack-tip constraint, the singular crack-tip field dominates over microstructurally significant size scales for loads ranging from globally linear-elastic conditions to moderately large-scale plasticity. For specimens with low crack-tip constraint, a dominant single-parameter crack-tip field exists only at low levels of plasticity. At higher levels of plasticity, the opening mode stress of the low constraint specimen is lower than predicted by the single-parameter, asymptotically singular fields. Therefore, low constraint specimens often exhibit larger fracture toughness than do high constraint specimens. If feasible, users are strongly encouraged to generate high constraint fracture toughness data using methods such as Test Methods E399 or E1820 prior to testing the surface crack geometry.

5.2.1 To address this phenomenon, two-parameter fracture criteria are used to include the influence of crack-tip constraint. Crack-tip constraint has been quantified using various scalar parameters including the T-stress (6, 7, 8), Q (9, 10), stress triaxiality (11, 12), and α_h (13, 14). Fracture toughness in a two-parameter methodology is not a single value, but rather is a curve that defines a critical locus of fracture toughness and constraint values (2). Fig. 2 illustrates a toughness-constraint locus for application of two-parameter fracture mechanics to structures. A structural analysis provides the driving force curve for the configuration of interest, and is plotted with......

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