Crack-tip behaviors of stationary and growing cracks in Al-Fe-X alloys: Part II. Crack opening profile

1990 ◽  
Vol 21 (1) ◽  
pp. 81-86 ◽  
Author(s):  
Kwai S. Chan
Keyword(s):  
Crack Opening ◽  
Crack Tip ◽  
Growing Cracks

Prediction of the Initial Crack Tip Microstructure in a Single Crystal of CuAlNi

1999 ◽  
Author(s):  
Galyna M. Vasko ◽  
Perry H. Leo ◽  
Thomas W. Shield
Keyword(s):  
Stress Field ◽  
Single Crystal ◽  
Crack Opening ◽  
Crack Tip ◽  
Initial Crack ◽  
Single Edge ◽  
Opening Displacement ◽  
Elastic Crack ◽  
Maximum Work ◽  
Anisotropic Elastic

Abstract The austenite to martensite pseudoelastic transformation induced by the anisotropic elastic crack tip stress field in a single crystal of shape memory alloy is considered. It is proposed that the orientation of the initial austenite-martensite interface that forms can be predicted based on knowledge of the stress field, the crystallography of the transformation and one of two selection criteria. These criteria are based on the work of formation of the martensite in stress field and the crack opening displacement the martensite causes at the crack. Predictions of the criteria are compared to experiments on three single edge notched CuAlNi single crystal specimens. Results indicate that the maximum work criterion accurately predicts the orientation of the austenite-martensite interfaces that initially form near a crack.

Plastic relaxation at a crack tip by asymmetric slip

1988 ◽  
Vol 418 (1854) ◽  
pp. 261-280 ◽  
Keyword(s):  
Slip Band ◽  
Crack Opening ◽  
Crack Tip ◽  
Friction Stress ◽  
Small Scale ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Sharp Crack ◽  
Scale Yielding ◽  
Crack Tip Opening

Relaxation at a sharp crack tip by a single slip band is considered. It is shown that for mixed-mode loading of a plane crack in an isotropic medium there is a unique angle between the slip band and the crack for which the energy release rate (or stress intensity factor) of the crack can be reduced to zero. For such a slip-band calculations are made of the slipband length and the crack-opening displacement as a function of the loading, crack length and friction stress acting on dislocations in the slip band. For small-scale yielding, a simple model is discussed that gives a good approximation to the crack-tip opening displacement and slip-band angle.

scholarly journals Bridged crack - opening outside of the bridged zone and stresses at the material interface

2020 ◽  
pp. 69-77
Author(s):  
Михаил Натанович Перельмутер
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Crack Opening ◽  
Interfacial Crack ◽  
Crack Tip ◽  
Material Interface ◽  
External Loads ◽  
Bridged Crack ◽  
Element Method

Для прямолинейной трещины со связями в концевой области на границе соединения материалов получены выражения для расчета раскрытия трещины вне зоны, занятой связями, и напряжений за вершиной трещины. Рассматривается действие однородных - нормальной и сдвиговой - внешних нагрузок. Размер концевой области трещины не полагается малым по сравнению с длиной трещины. Выполнено сопоставление с результатами, полученными методом граничных элементов. For a straight interfacial crack with bridged zone the expressions for calculating the opening of the crack outside of the bridged zone and stresses ahead of the crack tip are obtained. The action of uniform normal and shear external loads is considered. The size of the crack bridged zone is not considered small compared with the length of the whole crack. A comparison with the results obtained by the boundary element method is presented.

Effect of Underloads on Plasticity-Induced Crack Closure: A Numerical Analysis

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
F. V. Antunes ◽  
L. Paiva ◽  
R. Branco ◽  
L. P. Borrego
Keyword(s):  
Plastic Deformation ◽  
Kinematic Hardening ◽  
Crack Opening ◽  
Compressive Force ◽  
Crack Tip ◽  
Transient Behavior ◽  
Contact Forces ◽  
Local Reduction ◽  
Tip Position ◽  
Loading Parameter

The effect of underloads is mostly quantified by the averaged effect on the fatigue crack growth rate, and the transient behavior is rarely investigated. The objective of this paper is to study the mechanisms behind the effect of underloads, periodic underloads, and underloads combined with overloads. A single underload smashes the material around the crack tip, producing a depression on crack flank and a local reduction of contact forces at the minimum load. The reduction of plastic elongation behind the crack tip has an immediate effect on crack opening level, which rapidly disappears with crack propagation. The smashing associated with the compressive force occurs mainly behind the crack tip position where the underload was applied. The effect of the underload is intimately linked to reversed plastic deformation, which explains its enhanced effect for kinematic hardening. The decrease of load below the minimum baseline load is the main loading parameter. The application of periodic underloads extends the effect of a single underload. The effect of the underload is enhanced by the presence of obstacles in the form of residual plastic deformation, which explains the great effect of underloads applied after overloads.

Assessment of Damage and Fracture Behaviours in a Cast Aluminium Alloy via In Situ Synchrotron Microtomography

2006 ◽  
Vol 519-521 ◽  
pp. 1005-1010 ◽  
Author(s):  
Shin Yamamoto ◽  
Hiroyuki Toda ◽  
L. Qian ◽  
Tomomi Ohgaki ◽  
Masakazu Kobayashi ◽  
...  
Keyword(s):  
Driving Forces ◽  
Crack Opening ◽  
Crack Tip ◽  
Cast Aluminum Alloy ◽  
Cast Aluminum ◽  
Contrast Imaging ◽  
Cracking Behavior ◽  
Damage And Fracture ◽  
Void Initiation

High resolution phase contrast imaging technique has been applied to obtain clear crack images together with the detailed of microstructural features in a cast aluminum alloy. Crack opening/closure, crack extension and damage evolution in the vicinity of a crack-tip is observed three-dimensionally (3-D). 3-D image analysis is performed to evaluate void initiation and growth near the crack-tip. The information on physical displacement of each microstructural feature is provided for analyzing local crack driving forces at crack front. This technique has been identified to provide a unique possibility to quantitatively interpret the 3-D cracking behavior in bulk materials.

Reconstitution of Compact Specimen for Irradiated Reactor Pressure Vessel Steel

2006 ◽  
Author(s):  
Toru Osaki ◽  
Hiroshi Matsuzawa
Keyword(s):  
Fracture Toughness ◽  
Plastic Deformation ◽  
Crack Opening ◽  
Crack Tip ◽  
Reactor Vessel ◽  
Compact Specimen ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Original Size ◽  
Surveillance Specimens

Reconstitution in this paper means to constitute the original size compact specimen, which is made of the insert cut out from tested specimen and tubs welded to the insert. It is a promising technique to secure an adequate number of surveillance specimens for long-term operation of nuclear power plants. The fracture toughness of each reactor vessel of pressurized water reactors in Japan is measured periodically by 1/2T compact surveillance specimens, and is applied to assess the structural integrity of the reactor vessel under pressurized thermal shock loads. [1] This practice should be continued and enhanced if possible, after the full use of originally installed specimens, because its fracture toughness is lower than before. Reconstitution of irradiated 1/2T compact specimens to the original size was studied and demonstrated. Reconstituted specimens were composed of an irradiated material called an insert and un-irradiated tabs welded to the insert. It was demonstrated that the central part of the insert near the crack tip was not annealed by the thermal transient during welding if properly adjusted YAG laser welding was applied. Crack-tip opening and compliance before and after reconstitution were investigated by testing and analysis. Testing and analysis of un-irradiated specimens before reconstitution showed that the plastic deformation expanded to an area wider than 6 mm, the half width of the insert if it was a reconstituted specimen. The material had medium fracture toughness. The reconstituted specimen of the same material showed almost the same fracture toughness, although the weld could not be yielded as the insert, which could affect the crack opening. The crack opening was immune to the change of the deformation far from the crack tip. Correlation between J at 2.5 mm crack extension and plastic deformation width, and the effects of short time annealing of the insert far from the crack tip during welding were studied. Integrating the results, the conditions for reconstituting the 1/2T compact specimen were settled. The reconstituted specimen with irradiated insert designed to meet the conditions showed little change in fracture toughness.

Test for Crack Opening Displacement of Steel Fiber Reinforced Concrete under Three-Point Bending

2010 ◽  
Vol 36 ◽  
pp. 157-161 ◽  
Author(s):  
Tin Gyi Zhang ◽  
Yuan Bao Leng ◽  
Dan Ying Gao
Keyword(s):  
Crack Opening Displacement ◽  
Crack Opening ◽  
Mouth Opening ◽  
Crack Tip ◽  
Crack Mouth Opening Displacement ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Critical Crack Opening ◽  
Crack Tip Opening

Based on the principle of electrical measurement method, the clip gauge was made to measure the crack opening displacement (COD).Through the three-point bending test on the specimens of steel fiber reinforced high strength concrete (SFHSC), the effect of the fiber volume fraction (ρf) upon the critical crack opening displacement (the critical crack tip opening displacement and the critical crack mouth opening displacement) was studied. The result shows that the effect of ρf on mouth-tip ratio (the ratio of critical crack mouth opening displacement to critical crack tip opening displacement) can reflect its effect upon the critical crack opening displacement. According to the geometrical relationship between the initial crack length and the critical crack opening displacement，calculation method for the initial crack length was proposed. Based on the test result, the formula was established for calculating the critical crack tip opening displacement.

Elastic-Plastic Analysis of Crack Opening, Stable Growth and Instability Behavior in Flawed 304 SS Piping

1983 ◽  
Vol 105 (4) ◽  
pp. 290-298 ◽  
Author(s):  
M. D. German ◽  
V. Kumar
Keyword(s):  
Applied Load ◽  
Failure Load ◽  
Crack Opening ◽  
Stress Criterion ◽  
Applied Loading ◽  
Area Of Interest ◽  
Bending Effect ◽  
Stable Growth ◽  
Flaw Type ◽  
Growing Cracks

Crack initiation, stable growth, instability and crack opening behavior in flawed 304 SS piping has been examined within the framework of the engineering approach developed by Kumar, German and Shih [1]. Crack geometries considered include part-through, complete circumferentially cracked pipe subjected to remote tension, and through-wall flawed pipe in tension and in bending. Effect of flaw type and size, pipe diameter and length, and applied loading on the failure load and mechanism is investigated. Results are employed to assess the net section stress criterion based on plastic collapse. Crack opening area of interest in leak rate evaluations is calculated as a function of applied load or pipe end deflection for stationary as well as growing cracks.

Hybrid Measurement of CT and Strain Distribution of Internal Crack Using Synchrotron High-Energy Monochromatic X-Rays

2010 ◽  
Vol 652 ◽  
pp. 202-209
Author(s):  
Keisuke Tanaka ◽  
Takahisa Shobu ◽  
Hiroshi Kimachi
Keyword(s):  
Strain Distribution ◽  
Crack Opening ◽  
Three Dimensional ◽  
Crack Tip ◽  
High Energy ◽  
Internal Crack ◽  
X Rays ◽  
Crack Face ◽  
Dimensional Shape ◽  
Three Dimensional Shape

Using high-energy monochromatic X-rays of energy 66.4keV from the synchrotron radiation source, SPring-8, we have developed a system to perform a hybrid measurement of imaging of cracks and strain distribution around cracks. This system was applied to a fatigue crack made in a round bar made of carbon steel with a diameter of 4 mm. Computed tomography of the specimen gave the three-dimensional shape of a thumb-nail crack. High tensile strain ahead of the crack was measured at the applied maximum stress, while the strain on the crack face was low because of stress relief due to crack opening. The full width at half maximum (FWHM) increased near the crack tip under loading, and then decreased after unloading. The recoverable part of FWHM by unloading was caused by the steep distribution of the applied stress in the vicinity of the crack tip. The FWHM increased by plastic deformation does not change when unloaded. The measured distributions of the lattice strain and FWHM agreed well with those of the elastic and plastic strains calculated by the finite element method, respectively.

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