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首页> 外文期刊>Zeitschrift fur Angewandte Mathematik und Mechanik >Numerical and Experimental Comparison of Bend Fracture Specimens with Shallow and Deep Cracks
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Numerical and Experimental Comparison of Bend Fracture Specimens with Shallow and Deep Cracks

机译：浅，深裂纹弯曲试样的数值与实验比较

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摘要

The effect of crack depth to specimen width ratio (a/W) on CTOD resistance curves of a HSLA steel was studied on SENB specimens with rectangular cross-section of 18 x 36 mm. The experimental results and the elastic-plastic finite-element analyses may be summarized as follows: The boundary value of crack depth ratio between shallow crack behaviour and deep crack behaviour seems to lie between 0.1 and 0.2 (Fig. 1). A comparison of the 2-D finite element results of various crack depth ratios (a/W) showed a fundamental change in the nonlinear stress field at an a/W of approximately 0.15. Specimens with shorter cracks showed yielding to the free surface behind the crack well before the formation of a plastic hinge. Specimens with deeper cracks (a/W = 0.20) developed a plastic hinge before the plastic zone extended from the crack tip to the back surface. The CTOD values at the initiation of ductile tearing and especially their engineering approximation CTOD_(0.2BL) increase considerably with the use of shallow cracked specimens (Fig. 1). The plastic rotation factor was found to be between 0.2 and 0.3 for shallow cracked specimens (Fig. 2). The standard value 0.4 (1) is apparently not adequate for all materials and crack lengths. Figure 3 shows that the BS estimation procedure overpredicts the experimental δ_5 values. With adjusting the plastic rotation factor r_p = 0.20 to 0.25 for shallow; cracked specimens, we get a very good agreement between the two values. Therefore it is very important to have a reasonably accurate estimate of the r_p. The application of δ_5 measurements on the shallow and deep cracked bend specimens offers a simple and quick toughness estimation technique without a need for knowing the material yield strength and any plastic rotation corrections.
机译：在矩形截面为18 x 36 mm的SENB试样上研究了裂纹深度与试样宽度之比（a / W）对HSLA钢CTOD电阻曲线的影响。实验结果和弹塑性有限元分析可总结如下：浅裂纹行为与深裂纹行为之间的裂纹深度比的边界值似乎在0.1到0.2之间（图1）。比较各种裂纹深度比（a / W）的二维有限元结果表明，在a / W约为0.15时，非线性应力场发生了根本变化。裂纹较短的试样在形成塑料铰链之前，就很好地屈服于裂纹后面的自由表面。裂纹较深的试样（A / W = 0.20）在塑性区从裂纹尖端延伸到背面之前形成了塑料铰链。延展性撕裂开始时的CTOD值，尤其是其工程近似值CTOD_（0.2BL），随着使用浅裂样品而显着增加（图1）。发现浅裂纹样品的塑性旋转系数在0.2到0.3之间（图2）。标准值0.4（1）显然不足以适用于所有材料和裂纹长度。图3表明，BS估计过程会过度预测实验δ_5值。调整塑料旋转系数，r_p = 0.20至0.25（对于浅层）；破裂的样本，我们在两个值之间获得了很好的一致性。因此，对r_p进行合理准确的估计非常重要。在浅裂纹和深裂纹弯曲试样上应用δ_5测量可提供一种简单而快速的韧性估算技术，而无需了解材料的屈服强度和任何塑性旋转校正。

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