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首页> 外文期刊>Metallurgical and Materials Transactions, A. Physical Metallurgy and Materials Science >Modeling and measurement of the notched strength of gamma titanium aluminides under monotonic loadin
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Modeling and measurement of the notched strength of gamma titanium aluminides under monotonic loadin

机译：单调加载下γ钛铝化物缺口强度的建模与测量

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A substantial concern with gamma titaniumaluminides is their limited ductility and, inparticular, the consequences of limited ductility atstress concentrators. In this study, the notchedstrength of a cast Ti-47.9Al-2.0Cr-2.0Nb alloy isconsidered under monotonic tensile loading at roomtemperature. Efforts are further focused on the alloy'sbehavior under conditions of plane stress and on caseswhere notch radii are large relative to grain size.Finite element predictions for notched tensilespecimens and the Neuber design criterion are used toquantify relationships between tensile ductility, theability to reduce local stress concentrations throughplastic flow, and ultimate failure loads in the abilityto reduce local stress concentrations through plasticflow, and ultimate failure loads in notched components.Results from the testing of two modeled configurationsare presented, and the numerical models are used tointerpret the test results. Two major issues areaddressed in this work. The first is how much plasticdeformation is needed to blunt stress concentrationsin gamma TiAl components under monotonic loading. Forvalues of elastic stress concentrations commonlyencountered in components, it is demonstrated that atotal strain at failure as low as 1 pct (correspondingto a plastic strain at failure of 0.8 pct) is sufficientto essentially achieve the maximum reduction in stressconcentration due to plastic flow. Second, therelationship between continuum-theory predictions ofnotched component failure (made using uniaxial tensiletest strains at failure) and failure loads observed innotched specimens is explored. It is shown that, onaverage, continuum-theory predictions of notchedstrength based on unnotched specimen strains at failureact as conservative lower bounds on actual results. Itis suspected that the notch strengthening observed ingamma TiAl is due to smaller volumes of highly strainedmaterial (a size effect) in the notched specimens.
机译：γ-钛铝化物的一个主要问题是它们的延展性有限，尤其是延展性有限的应力集中器的后果。在这项研究中，考虑了在室温下单调拉伸载荷下铸造的Ti-47.9Al-2.0Cr-2.0Nb合金的缺口强度。进一步的工作集中在合金在平面应力条件下的行为以及缺口半径相对于晶粒尺寸较大的情况下。缺口拉伸试样的有限元预测和Neuber设计准则用于量化拉伸延展性，降低局部应力的能力之间的关系。通过塑性流动的浓度，以及通过塑性流动减少局部应力集中的极限破坏载荷的能力，以及缺口构件的极限破坏载荷。给出了两种建模配置的测试结果，并使用数值模型来解释测试结果。这项工作解决了两个主要问题。首先是在单调加载下，需要多少塑性变形来钝化γTiAl组件中的应力集中。对于通常在组件中遇到的弹性应力集中的值，证明了低至1 pct的破坏时的总应变（对应于0.8 pct的破坏时的塑性应变）足以基本实现由于塑性流动引起的应力集中的最大降低。其次，探讨了缺口构件破坏的连续理论预测（在破坏时使用单轴拉伸测试应变）与观察到的缺口试样的破坏载荷之间的关系。结果表明，基于断裂时未缺口试样应变的缺口强度的平均连续理论预测可作为实际结果的保守下界。怀疑观察到的TiAl缺口增强是由于缺口样品中较小体积的高应变材料（尺寸效应）引起的。

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