Fracture Resistance and Stable Crack-Growth Behavior of 8-mol%-Yttria-Stabilized Zirconia

We construct an energy-based model to study crack growth behavior in a shape-memory alloy that undergoes a stress-induced austenite to martensite transformation. The total energy, which is the sum of the elastic energy of the specimen and loading device, the surface energy of the crack, and the energy associated with transforming austenite to martensite, depends on the applied extension, the crack length, and the martensite volume fraction. The crack length and martensite volume fraction are coupled through a transformation criteria at the crack tip. By tracking the progression of equilibrium cracks as extension increases, we show that the transformation leads to a regime of stable crack growth followed by unstable growth. These results are in agreement with experiments on both single crystal and polycrystal shape-memory alloys.

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An Experimental Study of the Crack Growth Behavior of 16MnR Pressure Vessel Steel

Journal of Pressure Vessel Technology ◽

10.1115/1.3008034 ◽

2008 ◽

Vol 131 (2) ◽

Cited By ~ 14

Author(s):

Xiaogui Wang ◽

Zengliang Gao ◽

Tianwen Zhao ◽

Yanyao Jiang

Keyword(s):

Growth Rate ◽

Crack Growth Rate ◽

Crack Growth ◽

Stable Crack Growth ◽

Growth Behavior ◽

Crack Growth Behavior ◽

Pressure Vessel Steel ◽

Constant Amplitude ◽

Vessel Steel ◽

R Ratio

An experimental investigation was conducted on the crack growth behavior of a pressure vessel steel, 16MnR, in ambient air. Standard compact tension specimens were subjected to Mode I loading with several R-ratios and loading amplitudes. Three circular notch sizes ranging from very sharp notch to blunt notch were used. In addition to constant amplitude loading, experiments were conducted to study the influences of overload and loading sequence on crack growth. The results show that the R-ratio has an insignificant influence on the crack growth of the material. The size of the notch together with the R-ratio and loading amplitude has a great influence on the early crack growth from the notch. A single tensile overload during a constant amplitude loading experiment retards the crack growth significantly. Right after the application of an overload, the crack growth rate is higher than that of the stable crack growth observed in the constant amplitude loading. The crack growth rate decreases and reaches a minimum value before it gradually increases and reaches the stable crack growth curve. In high-low sequence loading with the maximum load in the second step lower than that of the first loading step, the preceding higher constant amplitude loading results in a significant crack growth retardation in the second loading step. This phenomenon is similar to the effect of a single tensile overload on the constant amplitude loading. An existing model making use of the stress intensity factor is discussed with respect to its capability to describe the observed crack growth behavior with the influence of overload and sequence loading.

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