Fracture of B2 Aluminide Single Crystals

1990 ◽  
Vol 213 ◽  
Author(s):  
Kehi-Minn Chang ◽  
R. Darolia ◽  
H.A. Lipsitt
Keyword(s):  
Crystal Lattice ◽  
Single Crystals ◽  
Uniaxial Tension ◽  
Crack Growth ◽  
Cleavage Fracture ◽  
Fracture Behavior ◽  
Cleavage Plane ◽  
Model Based ◽  
Bend Tests ◽  
Crystalline Plane

ABSTRACTSingle crystals of B2 aluminides, including FeAl, NiAl, and CoAl, were tested to investigate their fracture behavior. Specimens were aligned along specific orientations of the crystal lattice. Both uniaxial tension and notched bend tests revealed a cleavage fracture in all crystals. The cleavage occurred along a specific crystalline plane: {100} for FeAl; {110} for NiAl and CoAl. A model based on the ordering energy of unlike atoms is proposed to explain the preferred cleavage plane in these B2 structures. Fracture on transient planes around {115} are observed in NiAl before the crack growth continues on a cleavage plane.

Cleavage Fracture and Dislocation Structures of Ductile L12 Type Ni3Ge Single Crystals

1990 ◽  
Vol 213 ◽  
Author(s):  
H.R.P. Inoue ◽  
C.M. Wayman ◽  
T. Saburi
Keyword(s):  
Electron Microscopy ◽  
Single Crystals ◽  
Cleavage Fracture ◽  
Room Temperature ◽  
Cleavage Plane ◽  
Stacking Faults ◽  
Octahedral Plane ◽  
Slip Bands ◽  
Persistent Slip Bands ◽  
Crack Tips

ABSTRACTFracture and dislocation structures of single crystals of the L12-type compound Ni3Ge deformed in tension-compression at room temperature are investigated by optical and electron microscopy. After considerable plastic deformation, cracks nucleate along primary (111) planes of [245]-oriented single crystals and grow in zigzag manner by connecting one octahedral plane to another. Fracture occurs by brittle cleavage. Similar cleavage fracture also occurs when thin films (whose plane is (111)) prepared from cyclically deformed specimens are further deformed at room temperature. These observations are different from those reported in a previous study where the cleavage plane is claimed to be {001} for single crystals deformed in tensio at room temperature. A number of piled-up dislocations are emitted due to stress concentration at and ahead of crack tips, evidencing that this compound is intrinsically ductile. Superlattice intrinsic stacking faults are observed in front of crack tips along with a moire structure. Although there is argument that such moire structures are formed in persistent slip bands during cyclic deformation of Ni3Al, this is unlikely in the present case. The moire structure observed is believed to be formed by deformation of the thin (111) film.

Fracture Behavior of Ceramics Used in Multilayer Capacitors

1986 ◽  
Vol 72 ◽  
Author(s):  
Theresa L. Baker ◽  
Stephen W. Freiman
Keyword(s):  
Crack Growth ◽  
Fracture Behavior ◽  
Ceramic Materials ◽  
Fatigue Tests ◽  
Internal Stresses ◽  
Crack Growth Behavior ◽  
Multilayer Capacitors ◽  
Materials Used ◽  
Aging Phenomena

AbstractThis study involved the determination of the effects of composition and microstructure on the fracture toughness and susceptibility to environmentally enhanced crack growth of several ceramic materials used in multilayer capacitors. Indentation-fracture procedures were used to measure KIC as well as to assess the possible effects of internal stresses on the fracture behavior of these materials and to correlate dielectric aging phenomena with strength. The environmentally enhanced crack growth behavior of these materials was determined by conducting dynamic fatigue tests in water.

scholarly journals R-curve Evaluation of Copper and Nickel Single Crystals Using Atomistic Simulations

Crystals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 441 ◽  
Author(s):  
Xiao Zhuo ◽  
Jang Kim ◽  
Hyeon Beom
Keyword(s):  
Energy Release Rate ◽  
Single Crystals ◽  
Crack Growth ◽  
Release Rate ◽  
Edge Crack ◽  
Strain Energy ◽  
Critical Strain ◽  
Strain Energy Release Rate ◽  
Strain Energy Release ◽  
Crack Growth Resistance

The technique of molecular statics (MS) simulation was employed to determine the crack growth resistance curve of Cu and Ni single crystals. Copper and Ni single crystal nanoplates with an edge crack subjected to a tensile displacement were simulated. Stress-displacement curves and snapshots of the atomic configuration corresponding to different displacement levels were presented to elucidate the deformation mechanism. It was observed that the edge crack propagated step by step in a brittle manner, and the amount of crack growth at each step was half the lattice parameter. Through an energy consideration, the critical strain energy release rate at the onset of crack propagation and the crack growth resistance were calculated. The crack growth resistance is larger than the critical strain energy release rate because of the crack growth effect.

Fatigue of Drill String Connections

1995 ◽  
Vol 117 (2) ◽  
pp. 126-132 ◽  
Author(s):  
F. P. Brennan
Keyword(s):  
Aspect Ratio ◽  
Crack Growth ◽  
Empirical Model ◽  
Drill String ◽  
Full Scale ◽  
Growth Data ◽  
Service Environment ◽  
Threaded Connections ◽  
Bend Tests ◽  
Full Scale Tests

This paper reports full-scale tests on threaded connections used in drill strings. A concise background is given concerning the in-service environment and loading conditions on the connections. This details some of the reasons particular steels are used in preference to others. Crack growth data is given for ten full-scale axial and rotating bend tests. This is compared with predictions from a dedicated weight function fracture mechanics solution designed for threaded connections. Crack aspect ratio is considered with a view to development of an appropriate empirical model.

scholarly journals Uncertainty Quantification in Small-Timescale Model-Based Fatigue Crack Growth Analysis Using a Stochastic Collocation Method

Metals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 646
Author(s):  
Hesheng Tang ◽  
Xueyuan Guo ◽  
Songtao Xue
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Uncertainty Quantification ◽  
Crack Growth ◽  
Collocation Method ◽  
Life Prediction ◽  
Remaining Useful Life ◽  
Stochastic Collocation ◽  
Stochastic Collocation Method ◽  
Model Based

Due to the uncertainties originating from the underlying physical model, material properties and the measurement data in fatigue crack growth (FCG) processing, the prediction of fatigue crack growth lifetime is still challenging. The objective of this paper was to investigate a methodology for uncertainty quantification in FCG analysis and probabilistic remaining useful life prediction. A small-timescale growth model for the fracture mechanics-based analysis and predicting crack-growth lifetime is studied. A stochastic collocation method is used to alleviate the computational difficulties in the uncertainty quantification in the small-timescale model-based FCG analysis, which is derived from tensor products based on the solution of deterministic FCG problems on sparse grids of collocation point sets in random space. The proposed method is applied to the prediction of fatigue crack growth lifetime of Al7075-T6 alloy plates and verified by fatigue crack-growth experiments. The results show that the proposed method has the advantage of computational efficiency in uncertainty quantification of remaining life prediction of FCG.

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