scholarly journals Permeability Experiment of Fractured Rock with Rough Surfaces under Different Stress Conditions

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-15 ◽  
Author(s):  
Zilong Zhou ◽  
Jing Zhang ◽  
Xin Cai ◽  
Shanyong Wang ◽  
Xueming Du ◽  
...  
Keyword(s):  
Fracture Surface ◽  
Dynamic Stress ◽  
Rough Surfaces ◽  
Fractured Rock ◽  
Great Influence ◽  
Surface Damage ◽  
Testing System ◽  
Material Transport ◽  
Fracture Surfaces ◽  
Before And After

To investigate the permeability changes and the mechanisms of fractured rock under dynamic and static stresses produced by earthquakes, permeability experiments on fractured rock with rough surfaces under axial dynamic and static stresses were conducted on the MTS815 Rock Mechanics Testing System. Surface asperity was investigated by scanning the specimen surfaces before and after testing. The results show that the roughness of fracture surface has a great influence on the permeability when the axial displacement is not enough to cause the fracture rock to slip. Moreover, the rougher fracture surface leads to severer surface damage as indicated by the more gouge productions. The accumulation of gouge materials on larger roughness fracture surfaces causes a slow drop in permeability. The fracture surfaces experience larger degradations, but it has small weights of gouge materials on fracture surface after testing under axial dynamic stress. The reason is that the gouge material transport and mobilization tend to occur in process of dynamic loading. Therefore, the permeability drops of axial dynamic stress are larger than those of axial static stress.

Locating Al in the DABCO catalyst before and after Al extraction

1990 ◽  
Vol 48 (4) ◽  
pp. 265-267
Author(s):  
Kathleen B. Reuter
Keyword(s):  
Active Site ◽  
Inverse Relationship ◽  
Transverse Direction ◽  
Reaction Rate ◽  
Acid Phosphate ◽  
Fracture Surfaces ◽  
Al Content ◽  
Before And After ◽  
Relationship Of

The reaction rate and efficiency of piperazine to 1,4-diazabicyclo-octane (DABCO) depends on the Si/Al ratio of the MFI topology catalysts. The Al was shown to be the active site, however, in the Si/Al range of 30-200 the reaction rate increases as the Si/Al ratio increases. The objective of this work was to determine the location and concentration of Al to explain this inverse relationship of Al content with reaction rate.Two silicalite catalysts in the form of 1/16 inch SiO2/Al2O3 bonded extrudates were examined: catalyst A with a Si/Al of 83; and catalyst B, the acid/phosphate Al extracted form of catalyst A, with a Si/Al of 175. Five extrudates from each catalyst were fractured in the transverse direction and particles were obtained from the fracture surfaces near the center of the extrudate diameter. Particles were also obtained from the outside surfaces of five extrudates.

Effect of MWCNT doping on the structural and optical properties of PVC/PVDF polymer blend

2017 ◽  
Vol 13 (2) ◽  
pp. 4640-4647
Author(s):  
A. M. Abdelghany ◽  
M.S. Meikhail ◽  
S.I. Badr ◽  
A. S. Momen
Keyword(s):  
Surface Damage ◽  
X Ray Diffraction ◽  
Dopant Content ◽  
Casting Technique ◽  
Transmission Electron ◽  
Dopant Level ◽  
Before And After ◽  
Carbon Nano Tubes ◽  
Small Band ◽  
Vibrational Bands

Thin film samples of pristine polyvinyl chloride (PVC), poly vinyldine fluoride (PVDF) in combination with their blend in addition to samples containing factorial mass fraction of multi wall carbon nano-tubes (MWCNTs) in the dopant level were prepared via routine casting technique using tetrahydrofurane (THF) as a common solvent. X-ray diffraction and transmission electron microscopy (TEM) depict the nano-scale (15-25 nm) of functionalized MWCNTs with no surface damage results from functionalization process.X-ray diffraction (XRD) shows a semi-crystalline nature of PVDF with evidence for more than one phase namely a and b phases. The fraction of b phase was calculated and correlated to the dopant content. FTIR optical absorption spectra revels a preservation of the main vibrational bands before and after addition of MWCNTs in the doping level with a presence of new small band 1151 cm-1 assigned for the interaction and complexation between constituents.

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.

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.

Microstructural and Fractographic Analysis of CuAlNi Shape Memory Alloy before and after Heat Treatment

2020 ◽  
Vol 405 ◽  
pp. 100-106
Author(s):  
Ivana Ivanić ◽  
Mirko Gojić ◽  
Stjepan Kožuh ◽  
Borut Kosec
Keyword(s):  
Heat Treatment ◽  
Shape Memory Alloy ◽  
Fracture Surface ◽  
Shape Memory ◽  
Fractographic Analysis ◽  
Before And After ◽  
Different Temperatures ◽  
The Difference ◽  
Type Of Fracture ◽  
Scanning Electron

The paper presents comparison of microstructure and fracture surface morphology of the CuAlNi shape memory alloy (SMA) after different heat treatment procedures. The investigation was performed on samples in as-cast state and heat treated states (solution annealing at temperatures of 850 °C / 60’ / H2O and 920 °C / 60’ / H2O along with tempering at two different temperature 150 °C / 60’ / H2O and 300 °C / 60’ / H2O). The microstructure of the samples was examined by optical (OM) and scanning electron microscope (SEM) equipped with device for EDS analysis. The obtained fracture surfaces were examined by SEM. Optical and scanning electron microscopy showed martensitic microstructure in all investigated samples. However, the fractographic analysis of samples after tensile testing reveals significant changes in fracture mechanism. In both solution annealed states the results shows transgranular type of fracture, but after tempering at two different temperatures the difference is obvious. After tempering at 150 °C, along with transgranular type of fracture appear some areas with intergranular type of fracture. After tempering at 300 °C, fracture surface reveals completely intergranular type of fracture.

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.

scholarly journals Dynamic Characteristics and Experimental Research of a Two-Span Rotor-Bearing System with Rub-Impact Fault

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Rui Zhu ◽  
Guang-chao Wang ◽  
Qing-peng Han ◽  
An-lei Zhao ◽  
Jian-xing Ren ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Critical Speed ◽  
Great Influence ◽  
Experimental Platform ◽  
Rotating Machine ◽  
Rotor Bearing ◽  
Before And After ◽  
Analysis System ◽  
The Stability ◽  
Bearing System

Rotor rub-impact has a great influence on the stability and safety of a rotating machine. This study develops a dynamic model of a two-span rotor-bearing system with rubbing faults, and numerical simulation is carried out. Moreover, frictional screws are used to simulate a rubbing state by establishing a set of experimental devices that can simulate rotor-stator friction in the rotor system. Through the experimental platform and its analysis system, the rubbing experiment was conducted, and the vibration of the rotor-bearing system before and after the critical speed is observed. Rotors running under normal condition, local slight rubbing, and severe rubbing throughout the entire cycle are simulated. Dynamic trajectories, frequency spectrum diagrams, chart of axis track, and Poincare maps are used to analyze the features of the rotor-bearing system with rub-impact faults under various parameters. The vibration characteristics of rub impact are obtained. Results show that the dynamic characteristics of the rotor-bearing system are affected by the change in velocity and degree of impact friction. The findings are helpful in further understanding the dynamic characteristics of the rub-impact fault of the two-span rotor-bearing system and provide reference for fault diagnosis.

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