Fracture Surfaces in 3D Fuse Networks

1995 ◽  
Vol 409 ◽  
Author(s):  
V. I. Räisänen ◽  
M. J. Alava ◽  
R. M. Nieminen
Keyword(s):  
Fracture Surface ◽  
Fracture Process ◽  
Energy Surface ◽  
Minimum Energy ◽  
Quenched Disorder ◽  
Nanometer Scale ◽  
Directed Percolation ◽  
Fracture Surfaces ◽  
Final Fracture ◽  
Roughness Exponent

We study a 3D random fuse network model with computer simulations. The breaking thresholds are distributed randomly, corresponding to quenched disorder. We find for the roughness exponent of the final fracture surface ζ = 0.47 ± 0.19, which is close both the minimum energy surface value and the directed percolation depinning model value in 2+1 dimensions. It is also similar to results from measurements of fracture surfaces at nanometer scale, and from experiments in which the fracture process occurs slowly as in fatique. The traditional measure of damage, the number of broken bonds grows faster than the area effect (nb ˜ L2.28), with no signs of a trivally brittle regime.

Self-affine Fracture Surface Parameters and Their Relationship with Microstructure in a Cast Aluminum Alloy

2002 ◽  
Vol 17 (6) ◽  
pp. 1276-1282 ◽  
Author(s):  
M. Hinojosa ◽  
J. Aldaco
Keyword(s):  
Aluminum Alloy ◽  
Fracture Surface ◽  
The Self ◽  
Cast Aluminum Alloy ◽  
Cast Aluminum ◽  
Force Microscopy ◽  
Fracture Surfaces ◽  
Atomic Force ◽  
Roughness Exponent

The possible role of microstructural features in determining the self-affinity of the fracture surface of a cast aluminum alloy is explored in this work. Fracture surfaces generated both in tension and impact tests were topometrically analyzed by atomic force microscopy, scanning electron microscopy, and stylus profilometry. The roughness exponent exhibited the “universal” value ζ ≈ 0.78, and the correlation length ζ was of the order of the grain size. The brittle intermetallic compounds known to be important in crack initiation did not show any correlation with the self-affine parameters of the resulting fracture surfaces in this particular case.

Microstructure and Self-Affine Fracture Surface Parameters in Steel

2006 ◽  
Vol 509 ◽  
pp. 43-48 ◽  
Author(s):  
J. Niño ◽  
M. Hinojosa ◽  
V. González
Keyword(s):  
Fracture Surface ◽  
Impact Test ◽  
Surface Parameters ◽  
Force Microscopy ◽  
Fracture Surfaces ◽  
Grain Sizes ◽  
Atomic Force ◽  
A Value ◽  
Roughness Exponent ◽  
Microstructural Condition

The fracture surfaces of SAE-1018 steel tension and impact test specimens with different grain sizes are analyzed in order to explore the possible relations between the microstructure and the self-affine fracture surface parameters such as the roughness exponent, ζ, and the correlation length, ξ. The topography of the fracture surfaces was observed and quantified by means of scanning electron microscopy, atomic force microscopy, optical microscopy and optical digitizer. It is confirmed that the fracture surfaces exhibit a self-affine behavior extending over six decades of length scale, from nanometers up to a few millimeters. The roughness exponent exhibits a value of ζ∼0.82 for all the cases regardless of the microstructural condition.

Fatigue Life Properties and Anomalous Macroscopic Fatigue Fracture Surfaces of Low Carbon Steel JIS-SM490B in High-Pressure Hydrogen Gas Environment

2016 ◽  
Author(s):  
Yuhei Ogawa ◽  
Hisao Matsunaga ◽  
Michio Yoshikawa ◽  
Junichiro Yamabe ◽  
Saburo Matsuoka
Keyword(s):  
Fracture Toughness ◽  
Fatigue Life ◽  
Fracture Surface ◽  
Crack Growth ◽  
Fracture Process ◽  
Fracture Morphology ◽  
Hydrogen Gas ◽  
Stage Iii ◽  
Fracture Surfaces ◽  
Stage Stage

Tension-compression fatigue tests using smooth specimens of low carbon steel JIS-SM490B were carried out in air and hydrogen gas environment under the pressure of 0.7 and 115 MPa at room temperature. In 0.7 MPa hydrogen gas, fatigue life curve was nearly equivalent to that in air. On the other hand, in 115 MPa hydrogen gas, fatigue life was significantly degraded in the relatively short fatigue life regime (e.g. Nf < 105). To clarify the effect of hydrogen environment on fracture process, fracture surfaces of these specimens were observed. In general, fatigue fracture process of steels with low or moderate strength is macroscopically divided into 3 stages. In the first stage (stage I), fatigue cracks initiate in some crystalline grains. In the second stage (stage II), the cracks propagate stably on a cycle-by-cycle basis. In the final stage (stage III), a tilted fracture surface, shear-lip, is formed by ductile tearing. In SM490B steel, this general fracture process was confirmed in air and 0.7 MPa hydrogen gas. In contrast, in 115 MPa hydrogen gas, there was no tilted portion in the stage III region, and the fracture surface was totally flat. Observation with scanning electron microscope revealed that dimples were formed by ductile tearing in the tilted fracture region in air and 0.7 MPa hydrogen gas. On the other hand, only a quasi-cleavage fracture surface existed in the final fracture region in 115 MPa hydrogen gas. To understand the cause of this peculiar fracture morphology, we conducted elasto-plastic fracture toughness tests in each environment, and investigated the fracture morphology. As a result of fracture toughness tests, crack growth rate in air and 0.7 MPa hydrogen gas was approximately equal to each other, and both the fracture surfaces were covered by dimples. This fracture morphology was in accordance with that of stage III morphology in fatigue specimen tested in air and 0.7 MPa hydrogen gas. However, in 115 MPa hydrogen gas, the crack growth was significantly accelerated, and the whole fracture surface was covered by quasi-cleavage. In this paper, firstly, the similarity of fracture surface between two test methods, i.e. fatigue test and fracture toughness test, is investigated. And then, the formation mechanism of the flat fracture surface is discussed by paying attention to the crack-growth acceleration in high-pressure hydrogen gas.

Fracture Toughness Testing and its Implications to Engineering Fracture Mechanics Analysis of Energy Pipelines

2018 ◽  
Author(s):  
Sergio Limon ◽  
Peter Martin ◽  
Mike Barnum ◽  
Robert Pilarczyk
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Test Data ◽  
Fracture Mode ◽  
Fracture Process ◽  
Fracture Behavior ◽  
Fracture Initiation ◽  
Fracture Toughness Testing ◽  
Final Fracture ◽  
Toughness Testing

The fracture process of energy pipelines can be described in terms of fracture initiation, stable fracture propagation and final fracture or fracture arrest. Each of these stages, and the final fracture mode (leak or rupture), are directly impacted by the tendency towards brittle or ductile behavior that line pipe steels have the capacity to exhibit. Vintage and modern low carbon steels, such as those used to manufacture energy pipelines, exhibit a temperature-dependent transition from ductile-to-brittle behavior that affects the fracture behavior. There are numerous definitions of fracture toughness in common usage, depending on the stage of the fracture process and the behavior or fracture mode being evaluated. The most commonly used definitions in engineering fracture analysis of pipelines with cracks or long-seam weld defects are related to fracture initiation, stable propagation or final fracture. When choosing fracture toughness test data for use in engineering Fracture Mechanics-based assessments of energy pipelines, it is important to identify the stage of the fracture process and the expected fracture behavior in order to appropriately select test data that represent equivalent conditions. A mismatch between the physical fracture event being modeled and the chosen experimental fracture toughness data can result in unreliable predictions or overly conservative results. This paper presents a description of the physical fracture process, behavior and failure modes that pipelines commonly exhibit as they relate to fracture toughness testing, and their implications when evaluating cracks and cracks-like features in pipelines. Because pipeline operators, and practitioners of engineering Fracture Mechanics analyses, are often faced with the challenge of only having Charpy fracture toughness available, this paper also presents a review of the various correlations of Charpy toughness data to fracture toughness data expressed in terms of KIC or JIC. Considerations with the selection of an appropriate correlation for determining the failure pressure of pipelines in the presence of cracks and long-seam weld anomalies will be discussed.

Research on Anisotropic Fracture Mechanical Behavior of Cortical Bone with Combined Method of Fractal and Gray Level Co-Occurrence Matrix

2021 ◽  
Vol 11 (1) ◽  
pp. 67-75
Author(s):  
Dagang Yin ◽  
Bin Chen ◽  
Huifen Zhou
Keyword(s):  
Mechanical Properties ◽  
Fracture Surface ◽  
Cortical Bone ◽  
Fracture Mechanisms ◽  
Gray Level ◽  
Combined Method ◽  
Characteristic Parameters ◽  
Fracture Surfaces ◽  
Anisotropic Fracture ◽  
Occurrence Matrix

The irregular fracture surface of cortical bone, which is caused by complex multilevel micro-nanostructure, reflects the mechanical properties and fracture mechanisms. It is of great significance to characterize some characteristic parameters from the fracture surfaces of bone. In this research, anisotropic fracture mechanical properties of bovine femoral cortical bone along transverse, longitudinal and radial direction are firstly obtained by three-point bend experiment. Then the fracture routes and fracture surfaces are observed by scanning electron microscope. The observation shows that the formed fracture surfaces, which are caused by different crack routes, are extremely rough and have complex textures. Lastly, the combined method of fractal and gray level co-occurrence matrix are adopted to describe the morphology of fracture surface of cortical bone objectively and quantitatively. It is shown that the fracture surface of cortical bone has obvious fractal characteristics and four statistical texture feature parameters (contrast,angular second moment, correlation and entropy) of GLCM of fracture surfaces can describe a certain fracture texture character. The relationship between the characteristic parameters and macroscopic mechanical properties are established. The quantitative analysis and automatic class identification for the fracture surfaces of cortical bone can be achieved.

Scanning Auger and Xps Studies of Fracture Surfaces of B4C Hot Pressed with Excess Carbon

1989 ◽  
Vol 153 ◽  
Author(s):  
Benjamin M. DeKoven ◽  
Eric A. Ness ◽  
David D. Hawn
Keyword(s):  
Fracture Surface ◽  
Boron Carbide ◽  
Carbon Content ◽  
Low Dose ◽  
Xps Spectra ◽  
Excess Carbon ◽  
Fracture Surfaces ◽  
Four Point Bending ◽  
Hardness Values

AbstractA series of boron carbide materials was hot pressed with 0-7% excess carbon. The strength of each material was determined by four point bending, and found to decrease from about 600MPa to 300MPa as the carbon content increased from 0% to 7%. Diamond indentation yielded hardness values that decreased from 28.3 to 25.OGPa and toughness values that increased from 3.5 to 4.5 MPa√mover the same carbon range. Each sample was fractured in situ in ultrahigh vacuum (UHV) and examined by scanning Auger microanalysis (SAM) and XPS to determine both the elemental and chemical state distributions. For the samples with excess carbon, localized carbonrich regions are observed on fracture surfaces by SAM. XPS reveals a 50% enhancement of excess carbon on the fracture surface compared to the bulk for the sample with 7% excess carbon. A correlation was observed between surface carbon composition and the bulk toughness and hardness. The C(ls) XPS spectra were utilized to determine the nature of carbon in B4C on freshly fractured and Ne+ bombarded surfaces. Two distinct peaks were observed in the C(ls) region. Low dose ion bombardment resulted in a single broad C(ls) peak at the midpoint of the two initial peaks. It can be inferred from this data that there are C-C-C intericosahedral linkages in B4C.

New Computational Procedures for Evaluation of Fracture Surfaces of the Drop Weight Tear Test of the Piping Steel

2011 ◽  
Author(s):  
Pavel Zˇidli´k ◽  
Petr Ferfecki ◽  
Bohumi´r Strnadel
Keyword(s):  
Fracture Surface ◽  
Ductile Fracture ◽  
Unstable Fracture ◽  
Fracture Surfaces ◽  
Drop Weight ◽  
Highly Sensitive ◽  
Drop Weight Tear Test ◽  
Computational Procedures ◽  
New Procedures

Drop weight tear test (DWTT) is one of the standard methods for evaluation of the ductility of large-dimensional structural components, such as pipelines used for gas and/or oil transportation. In general, the pipelines are even used in places with temperatures close to −40 °C, and in such environments, it is necessary to guarantee the resistance of the material used for pipeline against the initiation of unstable fracture. Currently, the percentage portion of the ductile fracture of the DWTT specimen is determined by an expert evaluator. The objective of this paper is to introduce new procedures working on the principle of deterministic, statistical and fractal description of the fracture surface. For the proposed computational procedures, the fracture surface of the test specimen is scanned at the macroscopic level using the 3D-Cam scanner. The newly investigated procedures show highly sensitive to the determination of the percentage portion of the ductile fracture on the tested DWTT specimens. The developed procedures to assess the fracture surfaces of the DWTT specimens contributes to making the results of this test more correct, objective and also increases the reliability and safety of the manufactured pipelines.

scholarly journals The Evaluation of the Fracture Surface in the AW-6060 T6 Aluminium Alloy under a Wide Range of Loads

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 324 ◽  
Author(s):  
Marcin Chybiński ◽  
Łukasz Polus ◽  
Maria Ratajczak ◽  
Piotr Sielicki
Keyword(s):  
Fracture Surface ◽  
Strain Rate ◽  
Aluminium Alloy ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Tensile Loading ◽  
Engineering Structures ◽  
Fracture Surfaces ◽  
Wide Range ◽  
Scanning Electron

The present study focused on the behaviour of the AW-6060 aluminium alloy in peak temper condition T6 under a wide range of loads: tensile loading, projectile and explosion. The alloy is used as a structural component of civil engineering structures exposed to static or dynamic loads. Therefore, it was crucial to determine the material’s behaviour at low and intermediate rates of deformation. Despite the fact that the evaluation of the strain rate sensitivity of the AW-6060 aluminium alloy has already been discussed in literature, the authors of this paper wished to further investigate this topic. They conducted tensile tests and confirmed the thesis that the AW-6060 T6 aluminium alloy has low strain rate sensitivity at room temperature. In addition, the fracture surfaces subjected to different loading (tensile loading, projectile and explosion) were investigated and compared using a scanning electron microscope, because the authors of this paper were trying to develop a new methodology for predicting how samples had been loaded before failure occurred based on scanning electron microscopy (SEM) micrographs. Projectile and explosion tests were performed mainly for the SEM observation of the fracture surfaces. These tests were unconventional and they represent the originality of this research. It was found that the type of loading had an impact on the fracture surface.

Self-Affine Measurements on the Fracture Surface of Plastic Materials by AFM

1999 ◽  
Vol 578 ◽  
Author(s):  
E. Reyes ◽  
C. Guerrero ◽  
V. González ◽  
M. Hinojosa
Keyword(s):  
Plastic Material ◽  
Polymeric Materials ◽  
Operating Conditions ◽  
Average Roughness ◽  
Sem Images ◽  
Fracture Surfaces ◽  
Material Surfaces ◽  
Plastic Materials ◽  
Roughness Exponent ◽  
Good Agreement

AbstractThe self-aff'me behavior of fracture surfaces of polymeric materials was qualitatively and quantitatively studied. SEM images of fracture surfaces of both polypropylene and polystyrene show Chevron marks at several magnifications. In addition, for polystyrene the mirror and Hackle zones were also observed. For quantitative analysis, the average roughness exponent, ζ, of height profiles generated by AFM images, was estimated by applying the variable bandwidth method. Values of ζ=0.788 and ζ=0.810 were obtained for polypropylene and polystyrene, respectively. These results are in very good agreement with the claimed universal exponent of 0.8 reported in the literature for other non-polymeric materials. By choosing the AFM appropriate operating conditions, measurements of roughness on plastic material surfaces could be performed.

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