Role of Crack Wake Toughening on Elevated Temperature Crack Growth in a Fiber Reinforced Ceramic Composite

1993 ◽  
Vol 115 (3) ◽  
pp. 273-280 ◽  
Author(s):  
Shantikumar V. Nair ◽  
Tsung-Ju Gwo
Keyword(s):  
Elevated Temperature ◽  
Crack Growth ◽  
Crack Front ◽  
Volume Fraction ◽  
Process Zone ◽  
Stable Crack Growth ◽  
Creep Process ◽  
Failure Behavior ◽  
Matrix Cracks ◽  
Presence And Absence

Theoretical models were developed to predict the nature of the elevated temperature failure behavior in composites containing bridged cracks both for the case where crack front creep is absent (brittle regime) and for the case where a frontal creep process zone is present (ductile regime). The nature of the thermally activated time-dependent bridging of matrix cracks was first briefly reviewed from an earlier study and then applied to the case where crack front creep was present. Stable crack growth was predicted both in the presence and absence of crack front creep after an initial delay period, or initiation, which depends on crack size and wake parameters, such as, fiber diameter, volume fraction and interface properties. The dependence of the initiation time and crack growth rates on flaw size and wake parameters as well as on composite microstructure was derived both for the presence and absence of crack front creep. The implications of the results for elevated temperature composite component design are discussed.

Prediction of creep crack growth from uniaxial creep data

1984 ◽  
Vol 396 (1810) ◽  
pp. 183-197 ◽  
Keyword(s):  
Crack Growth ◽  
Growth Rates ◽  
Process Zone ◽  
Creep Crack Growth ◽  
Creep Process ◽  
Uniaxial Tensile ◽  
Creep Data ◽  
Creep Ductility ◽  
Creep Crack ◽  
Crack Growth Rates

In this paper uniaxial tensile creep data are used in conjunction with fracture mechanics concepts to predict creep crack growth rates in materials having a wide range of creep ductilities. A model is proposed of creep damage accumulation in a process zone ahead of the crack tip. The model allows all stages of creep to be incorporated in an approximate manner and creep ductility to be stress and stress-state sensitive. Good agreement is obtained with experimental crack growth data on a range of low alloy steels, a stainless steel, an aluminium alloy and a nickel-base superalloy. It is found that cracking rate is insensitive to the creep process zone size but inversely proportional to creep ductility. Crack growth rates under plane strain conditions are shown to be about fifty times those for plane stress loading.

A Lumped Energy Model for Crack Growth in Shape-Memory Materials

2015 ◽  
Vol 83 (3) ◽  
Author(s):  
Perry H. Leo ◽  
Thomas W. Shield
Keyword(s):  
Shape Memory ◽  
Crack Length ◽  
Crack Growth ◽  
Martensite Transformation ◽  
Volume Fraction ◽  
Stable Crack Growth ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Martensite Volume Fraction ◽  
Shape Memory Materials

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.

Crack Growth Resistance of Ceramic Composite

1992 ◽  
Vol 287 ◽  
Author(s):  
Seijiro Hayashi ◽  
H. Baba ◽  
A. Suzuki
Keyword(s):  
Crack Growth ◽  
Fracture Process ◽  
Ceramic Composite ◽  
Fracture Process Zone ◽  
Process Zone ◽  
Crack Opening ◽  
Stable Crack Growth ◽  
Beam Specimen ◽  
Opening Displacement ◽  
Element Analysis

ABSTRACTFracture process zone in SiCw/Si3N4 ceramic composite was studied by a hybrid experimental-numerical analysis employing moire interferometry and finite element analysis. A chevron-notched, wedge-loaded double cantilever beam specimen was used to obtain a stable crack growth. The relation between crack closure stress and crack opening displacement which govern fracture process zone was obtained.

Microstructural characterization of a rapidly solidified Al-Fe-V-Si alloy for elevated temperature applications

1988 ◽  
Vol 46 ◽  
pp. 550-551
Author(s):  
R. E. Franck ◽  
J. A. Hawk ◽  
G. J. Shiflet
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Grain Growth ◽  
Volume Fraction ◽  
Microstructural Characterization ◽  
Second Phase ◽  
Microstructural Stability ◽  
Elevated Temperature Strength ◽  
Temperature Applications

Rapid solidification processing (RSP) is one method of producing high strength aluminum alloys for elevated temperature applications. Allied-Signal, Inc. has produced an Al-12.4 Fe-1.2 V-2.3 Si (composition in wt pct) alloy which possesses good microstructural stability up to 425°C. This alloy contains a high volume fraction (37 v/o) of fine nearly spherical, α-Al12(Fe, V)3Si dispersoids. The improved elevated temperature strength and stability of this alloy is due to the slower dispersoid coarsening rate of the silicide particles. Additionally, the high v/o of second phase particles should inhibit recrystallization and grain growth, and thus reduce any loss in strength due to long term, high temperature annealing.The focus of this research is to investigate microstructural changes induced by long term, high temperature static annealing heat-treatments. Annealing treatments for up to 1000 hours were carried out on this alloy at 500°C, 550°C and 600°C. Particle coarsening and/or recrystallization and grain growth would be accelerated in these temperature regimes.

Fracture and Fatigue Resistance of Ultrafine Grain CuCrZr Alloy Produced ECAP

2006 ◽  
Vol 503-504 ◽  
pp. 811-816 ◽  
Author(s):  
Alexei Vinogradov ◽  
Kazuo Kitagawa ◽  
V.I. Kopylov
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Stable Crack Growth ◽  
Ultrafine Grain ◽  
J Integral ◽  
Present Communication ◽  
Angular Pressing ◽  
Fatigue And Fracture ◽  
Anisotropy Of Mechanical Properties

Anisotropy of mechanical properties, fatigue and fracture resistance of precipitation hardened CuCrZr alloy ultrafine (UFG) grained by equal-channel angular pressing (ECAP) is in focus of the present communication. Fracture toughness was estimated in terms of J-integral and the fatigue crack growth rate was quantified. It was found that although the estimated JIC-value appeared lower than that reported in the literature for a reference alloy, the ductility, fracture and crack growth resistance remained satisfactory after ECAP while the tensile strength and fatigue limit improved considerably. The stable crack growth rate did not differ very much for ECAP and reference conventional CuCrZr and no remarkable anisotropy in the stable crack growth was noticed.

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