第1部分:A36钢短裂纹和深裂纹CTOD断裂试样的分析比较裂纹深度与试样宽度之比对裂纹尖端张开位移（CTOD）断裂韧性的影响是将实验室试验结果与实际结构行为联系起来的一个重要考虑因素。实验室试验中最常用的是裂纹深度与试样宽度比（a/W）为0.50的深度裂纹三点弯曲试样。然而，为了评估特定的焊缝微观结构或浅表面裂纹结构的行为，a/W比远小于0的试样。 通常需要50个。实验室试验表明，具有短裂纹（a/W=0.15）的三点弯曲试样在延性起始点之前的临界CTOD值明显大于具有深裂纹（a/W=0.5）的试样。在本研究中，采用有限元分析来比较方形（横截面）三点弯曲试样的弹塑性行为，裂纹深度与试样宽度比（a/W）介于0.50和0.05之间。对a/W比为0.15的试样进行的二维分析显示，变形模式从深层裂纹变形模式发生了根本性变化。 随着塑性铰的发展，塑性区延伸到裂纹后面的自由表面。对于较短的裂纹（a/W=0.10和0.05），塑性区在塑性铰形成之前延伸至裂纹后面的自由表面。对于较长的裂纹（a/W>0.20），在塑性区延伸到裂纹后面的自由表面之前，会形成塑性铰。第2部分:裂纹深度对弹塑性CTOD断裂韧性的影响必须了解裂纹深度（a/W比）对断裂韧性弹塑性测量的潜在影响，以便将实验室试验结果与有缺陷结构部件的行为正确关联。 深裂纹试样（a/W=0.50）被广泛用于提供最严重的裂纹尖端条件，因此是断裂韧性的保守（下限）测量。当CTOD试样中深度裂纹试样不合适或不可能获得时，通常使用短裂纹试样（A/W<0.50）。具体的例子是对焊接件、局部脆性区（LBZ）和带有浅裂纹或短裂纹（尤其是表面缺陷）的在役结构中的特定微观结构进行测试。本研究比较了方形（横截面）三种模型的CTOD结果- 具有短裂纹（a/W=0.15）的点弯曲试样与具有深裂纹（a/W=0.50）的试样的CTOD结果一致。第3部分:短裂纹试样试验的J积分和CTOD参数比较在线性弹性行为不再适用的过渡区广泛使用的两种弹塑性断裂力学（EPFM）试验方法是J积分和裂纹尖端张开位移（CTOD）试验方法。J积分测试程序仅限于延性撕裂开始以上的温度区域，也仅限于试样的裂纹深度- 宽度比（a/W）介于0.50和0.75之间。相比之下，CTOD测试程序可用于测试从脆性到完全韧性的整个温度-韧性转变区域。此外，正在进行广泛的研究，以将CTOD试验程序扩展到短裂纹试样的试验（a/W比约为0.15）。

Part 1: An Analytical Comparison Of Short Crack And Deep Crack CTOD Fracture Specimens Of An A36 SteelThe effect of crack-depth to specimen-width ratio on Crack Tip Opening Displacement (CTOD) fracture toughness is an important consideration in relating the results of laboratory tests to the behavior of actual structures. Deeply cracked, three-point bend specimens with crack-depth to specimen-width ratios (a/W) of 0.50 are most often used in laboratory tests. However, to evaluate specific weld microstructures or the behavior of structures with shallow surface cracks, specimens with a/W ratios much less than 0.50 often are required. Laboratory tests reveal that three-point bend specimens with short cracks (a/W = 0.15) exhibit significantly larger critical CTOD values than specimens with deep cracks (a/W = 0.5) up to the point of ductile initiation.In this study, finite element analyses are employed to compare the elastic-plastic behavior of square (cross-section) three-point bend specimens with crack-depth to specimen- width ratios (a/W) ranging between 0.50 and 0.05. The two-dimensional analysis of the specimen with an a/W ratio of 0.15 reveals a fundamental change in the deformation pattern from the deep crack deformation pattern. The plastic zone extends to the free surface behind the crack concurrent with the development of a plastic hinge. For shorter cracks (a/W = 0.10 and 0.05), the plastic zone extends to the free surface behind the crack prior to the development of a plastic hinge. For longer cracks (a/W > 0.20), a plastic hinge develops before the plastic zone extends to the free surface behind the crack.Part 2: The Effects Of Crack Depth On Elastic-Plastic CTOD Fracture ToughnessThe potential effects of crack depth (a/W ratio) on elastic-plastic measures of fracture toughness must be known to correlate properly the results of laboratory tests with the behavior of flawed structural components. Deep crack specimens (a/W = 0.50) are used extensively to provide the most severe crack-tip conditions and therefore conservative (lower-bound) measures of fracture toughness. A short crack specimen (a/W << 0.50) is frequently employed when a deeply cracked specimen is either inappropriate or impossible to obtain in the CTOD specimen. Specific examples are the testing of particular microstructures in weldments, local brittle zones (LBZ's), and in-service structures with shallow or short cracks, particularly surface flaws. This study compares the CTOD results of square (cross-section) three-point bend specimens with short cracks (a/W = 0.15) to the CTOD results of specimens with deep cracks (a/W = 0.50).Part 3: A Comparison Of The J-Integral And CTOD Parameters For Short Crack Specimen TestingTwo of the elastic-plastic fracture mechanics (EPFM) test methods widely used in the transition region where linear-elastic ---, behavior is no longer applicable are the J-integral and the crack tip opening displacement (CTOD) test methods. The J-integral test procedure is restricted to temperature regions above the initiation of ductile tearing and is also limited to crack-depth to specimen-width ratios (a/W) between 0.50 and 0.75. In contrast, the CTOD test procedure can be used for testing throughout the entire temperature-toughness transition region from brittle to fully ductile behavior. Also, extensive research is being conducted to extend the CTOD test procedure to the testing of short crack specimens (a/W ratios of approximately 0.15).