Wide range stress intensity factor expressions for ASTM E 399 standard fracture toughness specimens
Wide range stress intensity factor expressions for ASTM E 399 standard fracture toughness specimens
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DOI：
10.1007/bf00032844
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发表时间：
1976
影响因子：
2.5
通讯作者：
J. Srawley
中科院分区：
文献类型：
--
作者：
J. Srawley
对于两种类型的试样，弯曲和紧凑，前面描述的平面应变断裂韧性的材料，E 399，一个多项式表达式给出的应力强度因子，K的计算，从施加的力，P，和试样尺寸。然而，明确指出，这些表达式不应在相对裂纹长度a/W（0.45至0.55）范围之外使用。虽然这个范围对于E 399来说是足够的，但是相同的试样类型通常用于更宽的a/W范围内的其他目的;例如，在疲劳裂纹扩展的研究中。给出的表达式至少与E 399-74中的表达式一样精确，并且涵盖了更宽的a/W范围：对于三点弯曲试样，a/W范围为0 ~ 1;对于紧凑试样，a/W范围为0.2 ~ 1。由于加载销孔靠近裂纹线，当a/W很小时，应力强度因子对尺寸的微小变化很敏感，因此对于紧凑型试样，该范围必须受到限制。这是与试样的紧凑性固有相关的惩罚。
For each of the two types of specimens, bend and compact, described previously for plane strain fracture toughness of materials, E 399, a polynominal expression is given for calculation of the stress intensity factor, K, from the applied force, P, and the specimen dimensions. It is explicitly stated, however, that these expressions should not be used outside the range of relative crack length, a/W, from 0.45 to 0.55. While this range is sufficient for the purpose of E 399, the same specimen types are often used for other purposes over a much wider range of a/W; for example, in the study of fatigue crack growth. Expressions are presented which are at least as accurate as those in E 399-74, and which cover much wider ranges of a/W: for the three-point bend specimen from 0 to 1; and for the compact specimen from 0.2 to 1. The range has to be restricted for the compact specimen because of the proximity of the loading pin holes to the crackline, which causes the stress intensity factor to be sensitive to small variations in dimensions when a/W is small. This is a penalty inherently associated with the compactness of the specimen.