Atomic force microscopy and the mechanism of fatigue crack growth

Jono, Masahiro; Sugeta, Atsushi; Uematsu, Yoshihiko

doi:10.1046/j.1460-2695.2001.00458.x

Cited by 28 publications

(8 citation statements)

References 17 publications

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“…7 (a), the crack grew along slip plane A, and then deflected and propagated along slip plane B, whose Schmid factor is lager than A as mentioned above. Since the crack driving force is too small in the low growth rate region to activate both slip planes A and B, crack tends to grow along one slip plane, especially slip plane B with larger Schmid factor (5) . In this case, slip line B 1 can be recognized in front of the crack tip and the front of slip locates at the point 1.…”

Section: Crack Growth Behaviormentioning

confidence: 99%

“…Figure 8 shows the examples of successive AFM images in square region "β" of Fig. 6 taken at the number of load cycles, N = 3.74×10 5 to 4.0×10 5 , where the sampling interval was 2 000 to 7 000 cycles. In Fig.…”

Section: Crack Growth Behaviormentioning

confidence: 99%

“…In Fig. 8 (c), which was sampled after 4 000 load cycles, crack grew along the slip plane A 3 and deflected toward the slip plane B 5 . Cross slips and crack branching behind the crack tip shown in Fig.…”

Section: Crack Growth Behaviormentioning

confidence: 99%

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Development of Fatigue Testing System for in-situ Observation by an Atomic Force Microscope and Small Fatigue Crack Growth Behavior in α-Brass

Sugeta

Uematsu

Tomita

et al. 2006

JSME Int. J., Ser. A

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A small in-plane bending fatigue testing machine for in-situ observation of small fatigue crack growth behavior by means of an atomic force microscope (AFM) was successfully developed. The multiple layer piezoelectric ceramics were adopted as an actuator in order to miniaturize the fatigue loading facility operating on the stage of an AFM. Small fatigue crack growth test under constant amplitude loading was then carried out on α-brass and successive observation of small fatigue crack growth behavior was performed by the AFM. The fatigue crack tended to grow along one slip direction with the highest Schmid factor, as the crack driving force of a small crack was not large enough to operate other slip directions with lower Schmid factors simultaneously. Frequent crack branching and deflection behavior were also observed during crack growth. It was considered that the constraint of slip deformation due to the cyclic strain hardening was mainly responsible for crack branching and deflection behavior. The intervals of branching or deflection were affected by the difference of mobility among slip planes.

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Section: Crack Growth Behaviormentioning

confidence: 99%

Section: Crack Growth Behaviormentioning

confidence: 99%

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Development of Fatigue Testing System for in-situ Observation by an Atomic Force Microscope and Small Fatigue Crack Growth Behavior in α-Brass

Sugeta

Uematsu

Tomita

et al. 2006

JSME Int. J., Ser. A

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“…In studies of small crack growth in ultra-fine grained aluminium under fatigue loading conditions, Zhang (2000) showed that cracks grew along shear bands emanating from the crack tip. Jono et al (2001) observed short fatigue cracks in a body centred cubic silicon iron growing in a zigzag pattern, following preferred slip planes activated in the crack tip vicinity. In Shen et al (1988), it was demonstrated that grain boundaries can act both as dislocation barriers and as sources for dislocation emission, thus influencing the crack path.…”

Section: Introductionmentioning

confidence: 89%

Growth of a short fatigue crack – A long term simulation using a dislocation technique

Bjerkén

Melin

2009

International Journal of Solids and Structures

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a b s t r a c tIn this study, the growth of a short edge crack during more than 14 000 cycles of fatigue loading is investigated in detail. An edge crack, in a semi-infinite body with no pre-existing obstacles present, is modelled in a boundary element approach by a distribution of dislocation dipoles. The fatigue cycles are fully reversed ðR ¼ À1Þ, and the load range is well below the threshold for long fatigue cracks. The developing local plasticity consists of discrete edge dislocations that are emitted from the crack tip. The movements of discrete dislocations are restricted to slip along preferred slip planes. The present model is restricted to a 2D plane strain problem with a through-thickness crack, assuming no 3D irregularities. A remote load is applied perpendicular to the crack extension line, and the material parameters are those of a BCC crystal structure. The competition between influence of the global loading on and local shielding of the crack tip governs the crack growth. The growth rate increases in discrete steps with short periods of retardation, from approximately the size of Burgers vector, b, up to 25 b per cycle as the length of the crack is tripled. The plastic zone changes from having an elongated, slender form to include a low angle grain boundary, which, eventually, divides into two parts. The crack growth is found to change from constant acceleration to constant growth rate as the event of the low-angle grain boundary split is approached. The results are compared to long crack characteristics, for which linear elastic fracture mechanics and Paris law can be used to predict fatigue crack growth. The exponent in Paris law varies between 1 and 0 in the present study, i.e. smaller than typical values for ductile BCC materials. The ratio between static and cyclic plastic zone sizes is found to increase during crack growth, and the angle of the general plastic zone direction increases, showing a tendency towards long crack values. The characteristics of the simulated crack growth, found in the present study, are typical for below-threshold growth, with slow acceleration, constant growth rate, and, eventually, either arrest or transition to long crack growth behaviour, as reported in the literature.

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“…5 These indicate that the SPMs are very suitable tools for investigating the fracture or degradation mechanisms associated with environmentally induced degradation. The authors and other researchers have already applied an SPM to image fracture surfaces (nano-fractography) 6 and sample surfaces, to correlate the nanoscopic topographies with the fracture mechanisms of fatigue 7,8 and environmentally induced degradation of metallic and non-metallic materials [9][10][11] , of micromaterials including high-strength, high-elastic-modulus fibres 12 and of microelements for micro-electro-mechanical systems. 13 In particular, micromaterials have characteristic dimensions of the order of micrometre, and therefore a nanoscopic observation tool is required instead of a conventional micrometre-order damage evaluation tool such as an SEM.…”

mentioning

confidence: 99%

Nanoscopic fatigue and stress corrosion crack growth behaviour in a high‐strength stainless steel visualized in situ by atomic force microscopy

Minoshima

Oie

Komai

2005

Fatigue Fract Eng Mat Struct

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A B S T R A C T In situ atomic force microscope (AFM) imaging of the fatigue and stress corrosion (SC) crack in a high-strength stainless steel was performed, under both static and dynamic loading. The AFM systems used were (1) a newly developed AFM-based system for analysing the nanoscopic topographies of environmentally induced damage under dynamic loads in a controlled environment and (2) an AFM system having a large sample stage together with a static in-plane loading device. By using these systems, in situ serial clear AFM images of an environmentally induced crack under loading could be obtained in a controlled environment, such as in dry air for the fatigue and in an aqueous solution for the stress corrosion cracking (SCC). The intergranular static SC crack at the free corrosion had a sharp crack tip when it grew straight along a grain boundary. The in situ AFM observations showed that the fatigue crack grew in a steady manner on the order of sub-micrometre. The same result was obtained for the static SC crack under the free corrosion, growing straight along a grain boundary. In these cases, the crack tip opening displacement (CTOD) remained constant. However, as the static SC crack was approaching a triple grain junction, the growth rate became smaller, the CTOD value increased and the hollow ahead of the crack tip became larger. After the crack passed through the triple grain junction, it grew faster with a lower CTOD value; the changes in the CTOD value agreed with those of the crack growth rate. At the cathodic potential, the static SC crack grew in a zigzag path and in an unsteady manner, showing crack growth acceleration and retardation. This unsteady crack growth was considered to be due to the changes in the local hydrogen content near the crack tip. The changes in the CTOD value also agreed with those of the crack growth rate. The CTOD value in the corrosive environment was influenced by the microstructure of the material and the local hydrogen content, showing a larger scatter band, whereas the CTOD value of the fatigue crack in dry air was determined by the applied stress intensity factor, with a smaller scatter band. In addition, the CTOD value in the corrosive environment under both static and dynamic loading was smaller than that of the fatigue crack; the environmentally induced crack had a sharper crack tip than the fatigue crack in dry air.

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Atomic force microscopy and the mechanism of fatigue crack growth

Cited by 28 publications

References 17 publications

Development of Fatigue Testing System for in-situ Observation by an Atomic Force Microscope and Small Fatigue Crack Growth Behavior in α-Brass

Development of Fatigue Testing System for in-situ Observation by an Atomic Force Microscope and Small Fatigue Crack Growth Behavior in α-Brass

Growth of a short fatigue crack – A long term simulation using a dislocation technique

Nanoscopic fatigue and stress corrosion crack growth behaviour in a high‐strength stainless steel visualized in situ by atomic force microscopy

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