Crack initiation and propagation in epoxy asphalt concrete in the three-point bending test

2014 ◽  
Vol 15 (3) ◽  
pp. 507-520 ◽  
Author(s):  
Leilei Chen ◽  
Zhendong Qian ◽  
Qing Lu
Keyword(s):  
Crack Initiation ◽  
Asphalt Concrete ◽  
Bending Test ◽  
Crack Initiation And Propagation ◽  
Three Point Bending ◽  
Epoxy Asphalt ◽  
Initiation And Propagation ◽  
Epoxy Asphalt Concrete

Crack Propagation Simulation for Epoxy Asphalt Concrete Pavement

2011 ◽  
Vol 460-461 ◽  
pp. 698-703 ◽  
Author(s):  
Sang Luo ◽  
Zhen Dong Qian ◽  
Chun Chen
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Asphalt Concrete ◽  
Crack Tip ◽  
Concrete Pavement ◽  
J Integral ◽  
Epoxy Asphalt ◽  
Initiation And Propagation ◽  
Asphalt Concrete Pavement ◽  
Epoxy Asphalt Concrete

Crack is one of the major distresses in asphalt pavement. Although epoxy asphalt concrete demonstrates higher distress resistant ability than traditional asphalt concrete, crack initiation and propagation is also inevitable due to traffic and environmental impact. Among the three typical crack modes, the Mode I crack usually appears in epoxy asphalt concrete pavement. In this paper, the model of crack propagation in epoxy asphalt concrete pavement is proposed and simulated through finite element method in conjunction with virtual crack extension approach. The eight-node singularity element was used at the crack-tip. And the node shift/release technique is adopted for modeling propagation of the crack tip. Results show that J-integral is path-independent due to the small plastic zone around the crack tip and suitable to evaluate the fracture behavior for epoxy asphalt concrete pavement. Two inflexions on the curve of J-integral vs. crack length indicate that epoxy asphalt concrete pavement have three phases in crack initiation and propagation: crack initiation, stable crack propagation and unstable crack propagation. Finally, the equation describing the relationship between J-integral and displacement is provided in this paper.

Fatigue Crack Growth Behavior of Threaded Pipe Couplings

2011 ◽  
Author(s):  
Jeroen Van Wittenberghe ◽  
Patrick De Baets ◽  
Wim De Waele
Keyword(s):  
Fatigue Crack ◽  
Fracture Surface ◽  
Crack Initiation ◽  
Crack Growth ◽  
Fatigue Behavior ◽  
Crack Opening ◽  
Bending Test ◽  
Crack Initiation And Propagation ◽  
Accurate Knowledge ◽  
Initiation And Propagation

Threaded couplings are used in various applications to connect steel pipes. To maintain a secure connection, such couplings are preloaded and during service additional dynamic loads can act on the connections. The coupling’s threads act as stress raisers, initiating fatigue cracks, which can cause the connection to fail in time. Accurate knowledge of the fatigue behavior, taking into account crack initiation and propagation is necessary to understand the fatigue mechanisms involved. In this study, the fatigue behavior of tapered couplings with NPT threads is studied. This is done by analyzing the results of an experimental four-point bending test. The fatigue crack propagation is monitored using an optical dynamic 3D displacement measurement device and LVDTs to measure the crack opening. At certain times during the test, the load ratio is changed to apply a number of beach marking cycles. This way a fine line is marked in the fracture surface. These marked crack shapes are used as input for a finite element model. The measured deflection and crack opening are compared to the results of the numerical simulations. Using this methodology a distinction is made between fatigue crack initiation and propagation. By analyzing the fracture surface it was observed that once the crack is initiated, it propagates over a wide segment of the pipe’s circumference and subsequently rapidly penetrates the wall of the pipe. The observed crack growth rates are confirmed by a fracture mechanics analysis. Since the appearing long shallow crack is difficult to detect at an early stage the importance is demonstrated of accurate knowledge of the fatigue behavior of threaded connections in order to define acceptable flaw sizes and inspection intervals.

scholarly journals Hydrogen enhanced cracking studies on Fe–3wt%Si single and bi-crystal microcantilevers

2017 ◽  
Vol 375 (2098) ◽  
pp. 20160410 ◽  
Author(s):  
T. Hajilou ◽  
Y. Deng ◽  
N. Kheradmand ◽  
A. Barnoush
Keyword(s):  
Stress Concentration ◽  
Crack Initiation ◽  
The Other ◽  
Bending Test ◽  
Propagation Path ◽  
Transgranular Fracture ◽  
Post Mortem ◽  
Crack Initiation And Propagation ◽  
Initiation And Propagation

Hydrogen (H) enhanced cracking was studied in Fe–3wt%Si by means of in situ electrochemical microcantilever bending test. It was clearly shown that the presence of H causes hydrogen embrittlement (HE) by triggering crack initiation and propagation at the notch where stress concentration is existing. Additionally, the effect of carbon content and the presence of a grain boundary (GB) in the cantilever were studied. It was shown that in the presence of H the effect of carbon atom on pinning the dislocations is reduced. On the other hand, the presence of a GB, while the chemical composition of material kept constant, will promote the HE. Crack initiation and propagation occur in the presence of H, while the notch blunting was observed for both single and bi-crystalline beams bent in air. Post-mortem analysis of the crack propagation path showed that a transition from transgranular fracture to intragranular fracture mechanism is highly dependent on the position of the stress concentration relative to the GB. This article is part of the themed issue ‘The challenges of hydrogen and metals’.

scholarly journals In Situ Scanning Electron Microscopy Observation of Crack Initiation and Propagation in Hydroxide Films Formed by Steam Coating on Aluminum-Alloy Sheets

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1238
Author(s):  
Hongmei Li ◽  
Naoki Takata ◽  
Makoto Kobashi ◽  
Ai Serizawa
Keyword(s):  
Crack Initiation ◽  
Amorphous Layer ◽  
Image Correlation ◽  
Bending Test ◽  
Al Alloy ◽  
Crack Initiation And Propagation ◽  
Surface Normal ◽  
Initiation And Propagation ◽  
Hydroxide Film

Hydroxide film was formed on 6061 Al-alloy (Al-1.00Mg-0.62Si(wt.%)) sheets by steam coating with the temperature of 220 °C for 24 h. During bending test of the coated specimens, the crack initiation and propagation processes in the hydroxide film were investigated using in situ SEM observations. The hydroxide film formed exhibited a dual-layer structure composed of an inner amorphous layer and an outer polycrystalline γ-AlO(OH)-phase layer. On the compressively strained surface, lateral cracks are preferentially initiated inside the inner amorphous layer, and propagate either inside this layer or on its interface with the outer γ-AlO(OH) layer. Digital image correlation analyses of the in situ observed SEM images suggested that the concentrated tensile strain along the surface normal localized at some parts of the amorphous layer could contribute to the crack initiation. On the tensile-strained surface, a number of cracks were initiated inside the inner amorphous layer along the surface normal and propagate into the outer γ-AlO(OH) layer. No cracks were found along the interface of the amorphous layer with the Al-alloy substrate. As a result, the anticorrosion hydroxide film adhered on the Al sheet after bending deformation. Such strong adhesion contributes to the excellent corrosion resistance of the Al-alloy parts provided by the steam coating.

scholarly journals Modelling the Crack Initiation and Propagation of Notched Rock Beam under the Three-Point Bending Load

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Xun Xi ◽  
Xu Wu ◽  
Qifeng Guo ◽  
Meifeng Cai
Keyword(s):  
Crack Initiation ◽  
Crack Length ◽  
Numerical Method ◽  
Rock Fracture ◽  
Peak Load ◽  
Crack Pattern ◽  
Crack Initiation And Propagation ◽  
Three Point Bending ◽  
Initiation And Propagation ◽  
Rock Beam

Prediction of rock fracture is essential to understand the rock failure mechanism. The three-point bending test has been one of the most popular experiments for the determination of rock fracture parameters. However, the crack initiation and propagation of rock beam with the center notch and offset notch have not been fully understood. This paper develops a numerical method for modelling the notched beam cracking based on nonlocal extended finite element method (i.e., XFEM) and mixed mode rock fracture model. An example is worked out to demonstrate the application of the numerical method and verified with experimental results. The crack length development, crack pattern, crack opening and slipping displacements, and the load-crack mouth of displacement (P-CMOD) curve are obtained. The effects of offset notch location and mechanical properties on the crack length development, P-CMOD curve, and crack pattern are investigated and discussed. It has been found that the peak load of the notched beam nearly linearly increases with the increase of the notch offset ratio. The cracking of rock beam with offset notch is dominated by mode I fracture, but mode II fracture contributes more when crack deflection occurs. The fracture energy significantly affects the peak load, while it has little effect on the prepeak and postpeak slopes in the P-CMOD curve.

A Double-Parameter K~J Fracture Criterion for Epoxy Asphalt Concrete

2010 ◽  
Vol 97-101 ◽  
pp. 809-813
Author(s):  
Zhen Dong Qian ◽  
Sang Luo ◽  
Chun Hong Chen ◽  
Zhi Li ◽  
Lei Lei Chen
Keyword(s):  
Asphalt Concrete ◽  
Fracture Criterion ◽  
Fracture Property ◽  
Three Point Bending ◽  
Long Span ◽  
Epoxy Asphalt ◽  
Influence Of Temperature On ◽  
Cracking Pattern ◽  
Two Parameters ◽  
Epoxy Asphalt Concrete

The epoxy asphalt concrete is extensively used as paving material for long-span steel bridges in China. But mode I crack, which is most prominent cracking pattern for the pavement, often appears on the pavement surface. Therefore, the stress intensity factor K and J-integral were adopted to analyze fracture properties of single-edge notched three-point bending beams. The influence of temperature on the two parameters was studied. The analyses indicate epoxy asphalt concrete exhibits ductile fracture property at 5~25°C and brittle fracture property at -15~5°C. It is also found that fracture property of epoxy asphalt concrete is better than other kinds of bituminous concrete. Finally, a double-parameter K~J fracture criterion is founded for the epoxy asphalt concrete and provides basis for anti-cracking design and repair of cracks of the pavement.

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