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Fracture toughness testing with notched round bars.

机译：带缺口圆棒的断裂韧性测试。

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摘要

Current fracture toughness testing is conducted with planar specimens, such as the compact tension C(T) specimen and the single edge bend SE(B) specimen. The crack front in a planar specimen has a constraint condition which varies through the thickness from plane stress on the lateral surfaces to plane strain in the middle of the specimen. This change in constraint makes the geometry of planar specimens three-dimensional; however, two-dimensional analyses based on the assumption of plane stress or plane strain are often performed.; An alternative specimen geometry is the notched round bar (NRB). This axisymmetric geometry has the advantage of constant constraint in the circumferential direction. Additionally, the NRB geometry can be modeled using an axisymmetric formulation--essentially a two-dimensional analysis.; The suitability of the NRB geometry for fracture toughness testing was studied. Notched round bars with finite notch root radii p were tested without fatigue precracking using methodologies similar to those described in ASTM test methods E399, E813, and E1152, and in a draft ASTM test method for transition fracture toughness testing of ferritic steels. Four different materials were tested: 2024T351 aluminum alloy, overaged 2024, a modified A302B steel, and nylon 6/6. Apparent fracture toughness {dollar}Ksb{lcub}Jc{rcub}{dollar} as a function of {dollar}sqrt{lcub}rho{rcub}{dollar} was a linear relation for 2024-T351 and modified A302B. Apparent initiation fracture toughness {dollar}Jsb{lcub}Q{rcub},{dollar} determined from NRB J-R curves, as a function of {dollar}rho{dollar} was a linear relation for overaged 2024 and nylon 6/6. Sharp-crack fracture toughness was determined by extrapolated apparent fracture toughness values to zero {dollar}rho .{dollar} The NRB results compared favorably to the results obtained from precracked C(T) and SE(B) specimens.; In addition to using an innovative approach for determining sharp-crack fracture toughness, two other innovative approaches were used. First, the load separation method was used to determine {dollar}etasb{lcub}pl{rcub}{dollar} for calculating {dollar}Jsb{lcub}pl{rcub}{dollar} from load-displacement test records and inferring crack length without direct measurement. Second, a yield function which included hydrostatic stress effects on yielding in the nonlinear finite element analyses was used.
机译：当前的断裂韧性测试是使用平面试样进行的，例如紧密拉伸C（T）试样和单边弯曲SE（B）试样。平面试样的裂纹前沿具有一个约束条件，其约束条件随厚度的变化而变化，从侧面的平面应力到试样中间的平面应变。这种约束的变化使平面试样的几何形状成为三维；然而，经常基于平面应力或平面应变的假设进行二维分析。可供选择的样品几何形状是带缺口的圆棒（NRB）。这种轴对称的几何形状具有在圆周方向上恒定约束的优点。此外，可以使用轴对称公式对NRB几何进行建模-本质上是二维分析。研究了NRB几何形状对断裂韧性测试的适用性。使用类似于ASTM测试方法E399，E813和E1152中描述的方法，以及用于铁素体钢的过渡断裂韧性测试的ASTM测试方法草案，对具有有限缺口根半径p的缺口圆棒进行了无疲劳预裂纹的测试。测试了四种不同的材料：2024T351铝合金，过时的2024，改良的A302B钢和尼龙6/6。表观断裂韧性{scrrt {lcub} rho {rcub} {dollar}的函数Ksb {lcub} Jc {rcub} {dollar}是2024-T351和改性A302B的线性关系。由NRB J-R曲线确定的表观起始断裂韧性{Jsb {lcub} Q {rcub}，{美元}，作为{rho {dollar}的函数，是过度老化的2024和尼龙6/6的线性关系。通过将表观断裂韧性值外推至零，可以确定出尖锐裂纹的断裂韧性。美元的NRB结果优于从预裂纹的C（T）和SE（B）试样获得的结果。除了使用创新方法确定锋利的断裂韧性外，还使用了另外两种创新方法。首先，采用载荷分离方法确定{dollar} etasb {lcub} pl {rcub} {dollar}，以便根据载荷位移测试记录计算出{dollar} Jsb {lcub} pl {rcub} {dollar}并推断裂纹长度无需直接测量。其次，在非线性有限元分析中使用了包括静水应力对屈服的屈服函数的屈服函数。

著录项

  • 作者

    Wilson, Christopher Dean.;

  • 作者单位

    The University of Tennessee.;

  • 授予单位 The University of Tennessee.;
  • 学科 Applied Mechanics.; Engineering Materials Science.; Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 1997
  • 页码 106 p.
  • 总页数 106
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 应用力学;工程材料学;机械、仪表工业;
  • 关键词

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