scholarly journals Fracture Analysis of α-Quartz Crystals Subjected to Shear Stress

Minerals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 870
Author(s):  
Giovanni Martinelli ◽  
Paolo Plescia ◽  
Emanuela Tempesta ◽  
Enrico Paris ◽  
Francesco Gallucci
Keyword(s):  
Shear Stress ◽  
Amorphous Silica ◽  
Morphological Characteristics ◽  
Fracture Analysis ◽  
Stress Rate ◽  
Quartz Crystals ◽  
Fracture Length ◽  
Total Fracture

This study assesses the correlations between the intensity of stress undergone by crystals and the morphological characteristics of particles and fracturing products. The effects of the fractures on the microstructure of quartz are also studied. Alpha quartz, subjected to shear stress, is quickly crushed according to a fracturing sequence, with a total fracture length that is correlated to the stress rate. The shear stress generates a sequence of macro and microstructural events, in particular localized melting phenomena, never highlighted before on quartz and the formation of different polymorphs, such as cristobalite and tridymite together with amorphous silica.

Optimization of Spacing and Penetration Ratio for Infinite-Conductivity Fractures in Unconventional Reservoirs: A Section-Based Approach

SPE Journal ◽  
2017 ◽  
Vol 22 (06) ◽  
pp. 1877-1892 ◽  
Author(s):  
S.. Liu ◽  
P. P. Valkó
Keyword(s):  
Shale Gas ◽  
Optimization Method ◽  
Limited Range ◽  
Productivity Index ◽  
Optimal Decision ◽  
Fracture Length ◽  
Penetration Ratio ◽  
Feasible Range ◽  
Infinite Conductivity ◽  
Total Fracture

Summary In this paper, we consider the development plan of shale gas or tight oil with multiple multistage fractured laterals in a large square drainage area that we call a “section” (usually 640 acres in the US). We propose a convenient section-based optimization of the fracture array with two integer variables, the number of columns (horizontal laterals) and rows (fractures created in a lateral), to provide some general statements regarding spacing of wells and fractures. The approach is dependent on a reliable and efficient productivity-index (PI) calculation for the boundary-dominated state (BDS). The dimensionless PI is obtained by solving a time-independent eigenvalue problem by use of the finite-element method (FEM) combined with the Richardson extrapolation. The results of the case study demonstrate two decisive factors: the dimensionless total fracture length, related to the total amount of proppant and fracturing fluid available for the section, and the feasible range of actual fracture half-lengths, related to current fracturing-technology limitations. Under the constraint of dimensionless total fracture length, increasing the number of columns (horizontal laterals) increases the total PI but with only diminishing returns, whereas the optimal fracture-penetration ratio decreases somewhat, but is still near unity. When adding the technological constraint of a limited range of fracture half-lengths that can be routinely and reliably created, only a few choices remain admissible, and the optimal decision can be easily made. These general statements for the ideal homogeneous and isotropic formation can serve as a reference in the more-detailed optimization works. In other words, we offer a first-pass method for decision making in early stages when detailed inputs are not yet available. The information derived from the section-based optimization method and the efficient and reliable algorithm for PI calculation should help the design of multistage fracturing in shale-gas or ultralow-permeability oil formations.

scholarly journals Electromagnetic Emissions from Quartz Subjected to Shear Stress: Spectral Signatures and Geophysical Implications

Geosciences ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 140 ◽  
Author(s):  
Giovanni Martinelli ◽  
Paolo Plescia ◽  
Emanuela Tempesta
Keyword(s):  
Shear Stress ◽  
Electromagnetic Waves ◽  
Emission Spectra ◽  
Stress Tests ◽  
Quartz Crystals ◽  
Piston Cylinder ◽  
Fracturing Process ◽  
Electromagnetic Emissions ◽  
As Stress ◽  
Energy Dissipated

Shear tests on quartz rocks and single quartz crystals have been conducted to understand the possible relationship between the intensity of detectable stress in fault areas and the energy released in the form of electromagnetic waves in the range 30 KHz-1 MHz (LF–MF). For these tests, a new type of piston-cylinder has been developed, instrumented to collect the electromagnetic signals generated by the quartz during shear stress tests and that allows energy measurements on electromagnetic emissions (EMR) to be performed. The data obtained indicate that shear-stressed quartz crystals can generate electromagnetic emissions in the LF–MF range. These emissions represent a tiny fraction of the total energy dissipated in the fracturing process. The spectrum of radio emissions consists of continuous radiation and overlapping peaks. For the first time, a characteristic migration of peak frequencies was observed, proportional to the evolution of the fracturing process. In particular, the continuous recording of the radio emission spectra shows a migration of the peaks toward higher frequencies, as stress continues over time and smaller and larger fractures form. This migration could be used to distinguish possible natural signals emitted by quartz in tectonically active environments from possible signals of other geophysical and possibly anthropogenic origin.

Cyclic Fracture Analysis of Semi-Natural Cast Iron Plate with Metallurgical Defects Layer

2010 ◽  
Vol 165 ◽  
pp. 61-65
Author(s):  
Marius Gutauskas ◽  
Jonas Bacevičius ◽  
Mindaugas Kazimieras Leonavičius
Keyword(s):  
Cast Iron ◽  
Cyclic Load ◽  
Fracture Process ◽  
Crack Formation ◽  
Fracture Analysis ◽  
Electronic Microscopy ◽  
Pure Bending ◽  
Iron Plate ◽  
Metallurgical Defects ◽  
Total Fracture

Fatigue fracture of the semi-natural cast iron plate with dross and carbon float defects was analyzed. Crack formation and propagation were traced under the programmable cyclic load of the pure bending. The focuses of the crack and their consistent pattern up to the total fracture were determined. Fracture analysis was performed by using optical and electronic microscopy methods. High-cycle fracture mechanism was established when the number of the cycles exceeded 108. The influence of the microstructure upon fracture process was investigated.

Aluminophosphosilicate Glasses as an Alternative Source for Microporous Materials of Technically Attractive Compositions and Morphological Characteristics

2015 ◽  
Vol 799-800 ◽  
pp. 145-152
Author(s):  
Taufik Aboud
Keyword(s):  
Amorphous Silica ◽  
High Surface ◽  
Morphological Characteristics ◽  
Acid Leaching ◽  
Chemical Durability ◽  
Silica Matrix ◽  
Glassy Matrix ◽  
Microporous Material ◽  
Alternative Source ◽  
Prolonged Heating

The glass-forming area in the system SiO2-P2O5-Al2O3-MgO-Na2O is determined utilizing reagent grade chemicals. The obtained glasses are characterized using FT-IR, DTA, DSC, TMA and SEM. The multicomponent, mixed network glasses exhibiting low coefficients of thermal expansion, fairly high softening temperatures (at Al2O3/P2O5˃1) and good chemical durability, are made of SiO4, AlO4and PO4polymerized tetrahedral units. AlPO4groups incorporated in the network structure increase thermal stability and modify the crystallization behavior, rendering it a slow process requiring high temperatures and / or prolonged heating times. Ceramization is accomplished through a multistage process depending mainly on the AlPO4content which is determined by the Al2O3/P2O5ratio. At Al2O3/P2O5≈1, AlPO4-high cristobalitic form is the first to crystallize in bulk, followed by farringtonite Mg3(PO4)2. At Al2O3/P2O5˃ 2, platy corundum is the main crystallizing phase. Microporous glass-ceramics are obtained via acid leaching of either some or all of the crystallized phases, or through dissolving of the glassy matrix and preserving a network of one or more of the crystalline phases. Selected phases of less chemical durability have been removed, to leave a network of the most chemically resistant phases AlPO4and amorphous silica. On the other hand, the amorphous silica matrix containing Na2O, MgO and P2O5has been leached out in glasses having fibrous corundum as the main crystallizing phase to produce a microporous material with a unique morphology, being made of what looks like a house of cards structure made up of deformed, randomly oriented corundum blades or sheets. Such morphology, is believed to provide a microporous material with an extremely high surface area.

Morphological Effect on Wall Shear Stress in Intracranial Aneurysms

2017 ◽  
Vol 79 (02) ◽  
pp. 108-115 ◽  
Author(s):  
Tian-Lun Qiu ◽  
Guo-Liang Jin ◽  
Hai-Tao Lu ◽  
Wu-Qiao Bao
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Intracranial Aneurysms ◽  
Multivariable Analysis ◽  
Morphological Characteristics ◽  
Parent Artery ◽  
Parent Vessel ◽  
Morphological Effect ◽  
Neck Width ◽  
Wall Shear

Background and Study Aims Both high and low wall shear stress (WSS) play important roles in the development and rupture of intracranial aneurysms (IAs). This study aimed to determine the morphological factors that affect WSS in the IA and the parent artery. Material and Methods We studied a total of 66 IAs with three-dimensional imaging. Computational fluid dynamics (CFD) models were constructed and used to characterize the hemodynamics quantitatively. Aneurysms were grouped according to the mean neck width. The associations among hemodynamics and morphology were analyzed. Results Aspect ratio was correlated to lowest WSS (r = − 0.576), aneurysm-to-parent vessel (A-P) WSS ratio (r = − 0.500), and lowest-parent vessel (L-P) WSS ratio (r = − 0.575). Height-to-width ratio and height were correlated to WSS. Mean aneurysm WSS (p = 0.023), lowest WSS (p < 0.0001), highest-to-lowest WSS ratio (p = 0.004), L-P WSS ratio (p < 0.0001), highest-parent vessel (H-P) WSS ratio (p = 0.008), A-P WSS ratio (p < 0.001), and height (p < 0.001) were different between the two groups of aneurysms that were divided by the relationship between the diameters of the aneurysms and the necks. Multivariable analysis showed that the lowest WSS (p = 0.028) and A-P WSS ratio (p = 0.001) were independently associated with neck width. Conclusion Morphological characteristics are associated with IA and parent vessel WSS. Aneurysms with different neck widths have different hemodynamics. These results could help in understanding the progression of IA and in building predictive models for IA rupture.

scholarly journals Comparative Study on Morphological, Physical and Mechanical Characteristics of L-PBF Based Alsi10mg Parts with Conventional Stir Casted Al-10%Sic Composites

2021 ◽  
Author(s):  
M. Saravana Kumar ◽  
E. Mohan ◽  
S. Robinson ◽  
D. ThivyaPrasad
Keyword(s):  
Fracture Toughness ◽  
Shear Stress ◽  
Tensile Test ◽  
Stress Test ◽  
Morphological Characteristics ◽  
Hardness Test ◽  
Stir Casting ◽  
Fracture Toughness Test ◽  
Double Shear ◽  
Toughness Test

Abstract Stir casting plays a major role in production of Al-SiC10% composites for aero space and automobile applications. However, obtaining the composites with homogenous distribution of the SiC particles, low porosity and without clustering of reinforcement particles were still a major problem faced by the research community. These kinds of casting defects were overcome by the Additive Manufacturing (AM) technology. In this research, AlSi10Mg parts were manufactured by Laser-Powder Bed Fusion (LPBF) method, one of the AM techniques. The mechanical and morphological characteristics of AM samples were compared with the Stir Casted (SC) samples. The influence of print orientation on the mechanical properties was also evaluated. It was found that the AM samples printed along the XY directions shows 26.5% and 8.2%higher fracture toughness and shear strength than AM samples printed along the Z directions. Both AM and SC samples were analyzed for the porosity% using the Optical Microscope (OM). The result shows that the AM sample shows reduced porosity of 1.4%. Mechanical testing such as tensile test, hardness test, fracture toughness test and double shear stress were carried out. The results obtained from the tensile test AM samples show 14.6% higher tensile strength than the SC samples, from the hardness test AM samples show 18.6% higher hardness strength than the SC samples, from the fracture toughness test AM samples show 33.4% higher fracture toughness strength than the SC samples and from the double shear stress test prove that the AM samples show 24.6% higher shear stress than the SC samples. The outcome of this research, it was proved that additive manufactured AlSi10Mgsample shows enhanced mechanical and morphological properties when compared with the conventional stir casting process.

On the Vector-Valued Cauchy Stress 2-Form and Its Stress Rate

2007 ◽  
Author(s):  
H. Murakami
Keyword(s):  
Shear Stress ◽  
Differential Forms ◽  
Shear Loading ◽  
Stress Rate ◽  
Curvilinear Coordinates ◽  
Lie Derivative ◽  
Cauchy Stress ◽  
Exterior Differential ◽  
Correct Definition ◽  
Vector Valued

Using exterior differential forms, basic equations of continuum mechanics are presented in direct notation. To this end, Elie Cartan’s vector-valued Cauchy stress 2-form is introduced. Its Lie derivative along the world line becomes the Truesdell stress rate. In the presentation, the notation adopted by Theodore Frankel (The Geometry of Physics, Cambridge, New York, 1997) is utilized. With the use of exterior differential forms, complicated computations in tensor analyses in curvilinear coordinates are dramatically simplified. As specific examples, the following subjects are presented: (i) Piola transformations of the Cauchy stress 2-form and (ii) simple shear deformation using the Lie derivative of the Cauchy stress 2-form, i.e., the Truesdell stress rate. It is known that under monotonic shear loading, if inappropriate stress-rates are used, shear stress oscillates. With the use of geometrically correct stress-rate, the shear stress monotonically increases. Thereby, the search for an appropriate stress rate reduces to the correct definition of the stress 2-form and the computation of its Lie derivative with respect to velocity.

Fracture Analysis of Pipe Sleeve on Extrusion Flare-Less Pipe Joints for Aircraft Hydraulic Pipe

2011 ◽  
Vol 291-294 ◽  
pp. 1087-1090 ◽  
Author(s):  
Feng Mei Xue ◽  
Fu Guo Li ◽  
Jiang Li ◽  
Wen Jun Yu ◽  
Jian Fei Li
Keyword(s):  
Stainless Steel ◽  
Shear Stress ◽  
Stress Concentration ◽  
High Strength ◽  
Fracture Analysis ◽  
Forming Process ◽  
Fracture Failure ◽  
Δ Ferrite ◽  
Pipe Joints ◽  
Bearing Behavior

The forming process of aircraft hydraulic pipe joints is investigated through experiments and analyses to solve the cracking problem of pipe sleeve on extrusion flare-less pipe joints. It can be concluded that the internal cause of the fracture failure is connected with the content, shape and distribution of δ-ferrite in 0Cr12Mn5Ni4Mo3Al high strength stainless steel, and the external cause is associated with the bearing behavior in the extrusion-bulging process of pipe sleeve. The crack is formed in the criss-crossing section of δ-ferrite on the function of shear stress in the stress concentration position, which belongs to ductile deformed crack. It eventually induces the intergranular fracture of pipe sleeve along the long axis with the expanding of subsequent crack.

An unusual occurrence of quartz and amorphous silica at Carmean, Moneymore, Co. Antrim

1977 ◽  
Vol 114 (5) ◽  
pp. 389-392 ◽  
Author(s):  
J. Preston
Keyword(s):  
Amorphous Silica ◽  
Globular Structure ◽  
Quartz Crystals ◽  
Unusual Occurrence

SummaryCavities in Cretaceous chalk, Co. Antrim, contain spongy silica. SEM photographs show minute doubly terminated quartz crystals trapped in fibrous mats of amorphous silica. The absence of both opal diffraction lines and a globular structure indicate the prior existence of gelatinous silica which prevented settling of the suspended quartz crystals. Drying and shrinkage of the gel produced the spongy deposit.

scholarly journals Design and evaluate of a multilevel laminar shear stress perfusion bioreactor

2020 ◽  
Author(s):  
Songrong Sun ◽  
Shaoxiong Huang ◽  
Xuejia Li ◽  
Xiaoyan Wang ◽  
Yihong Gong ◽  
...  
Keyword(s):  
Tissue Engineering ◽  
Shear Stress ◽  
Field Distribution ◽  
Fluid Shear Stress ◽  
Morphological Characteristics ◽  
Stress Perfusion ◽  
Laminar Shear Stress ◽  
Fluid Shear ◽  
Bioreactor System ◽  
Laminar Shear

Abstract Background: Fluid shear stress affects cell viability and cell differentiation. This study aimed to build a bioreactor for tissue engineering in which the cultured cells are exposed to custom designed multilevel laminar shear stress. Methods: The bioreactor was built based on a multi-layer plate configuration and equipped with an online monitoring system. The diameters of the diversion holes of each layer varied from 0.8mm to 1.4mm. Computational fluid dynamics and tracer liquid imaging velocity measurement were used to study the fluid field distribution. Finally, human umbilical cord mesenchymal stem cells (hUCMSCs) were cultivated in this bioreactor system. Results: The actual flow field distribution was consistent with the simulation results, and the average relative error of the flow velocity was 10.52%. The variation in shear stress of each layer was less than 3.0e-5 Pa, indicating that the flow microenvironment was uniform in each layer. Additionally, the shear stress increased with increasing diameters of the diversion holes. Cell culture experiments of Vero cells and hUCMSCs showed that the system continuously monitored morphological characteristics of the cells. The designed bioreactor achieved the desired proliferation, indicating that the bioreactor provided a suitable microenvironment for cell growth. Conclusion: The fluid shear stress within the bioreactor can be specified as required, and the morphological characteristics of the cells can be monitored in real time. It achieved the proliferation of hUCMSCs. This bioreactor system will facilitate the study of tissue engineering.

Sign in / Sign up

Export Citation Format

Share Document