scholarly journals Trans-Ply Crack Density Detection by Acousto-Ultrasonics

1988 ◽  
pp. 319-325 ◽  
Author(s):  
John H. Hemann ◽  
Paul Cavano ◽  
Harold Kautz ◽  
Ken Bowles
Keyword(s):  
Crack Density

Degradation of Rocks, Through Cracking Caused by Differential Thermal Expansion, in Relation to Nuclear Waste Repositories

1981 ◽  
Vol 6 ◽  
Author(s):  
J.R. Mclaren ◽  
R.W. Davidge ◽  
I. Titchell ◽  
K. Sincock ◽  
A. Bromley
Keyword(s):  
Thermal Expansion ◽  
Grain Boundary ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Crack Density ◽  
Granitic Rocks ◽  
Multiphase Materials ◽  
Thermal Expansion Behaviour ◽  
Waste Repositories ◽  
Expansion Behaviour

ABSTRACTHeating to temperatures up to 500°C, gives a reduction in Young's modulus and increase in permeability of granitic rocks and it is likely that a major reason is grain boundary cracking. The cracking of grain boundary facets in polycrystalline multiphase materials showing anisotropic thermal expansion behaviour is controlled by several microstructural factors in addition to the intrinsic thermal and elastic properties. Of specific interest are the relative orientations of the two grains meeting at the facet, and the size of the facet; these factors thus introduce two statistical aspects to the problem and these are introduced to give quantitative data on crack density versus temperature. The theory is compared with experimental measurements of Young's modulus and permeability for various rocks as a function of temperature. There is good qualitative agreement, and the additional (mainly microstructural) data required for a quantitative comparison are defined.

Crack Density Evaluation in Carbon Fibre Reinforced Polymers Aged by Thermal Cycling

2016 ◽  
Vol 53 (3) ◽  
pp. 125-143
Author(s):  
S. González ◽  
M. González ◽  
J. Dominguez ◽  
F. Lasagni
Keyword(s):  
Carbon Fibre ◽  
Thermal Cycling ◽  
Crack Density ◽  
Reinforced Polymers ◽  
Carbon Fibre Reinforced Polymers ◽  
Density Evaluation

scholarly journals Effect of carbon anode production parameters on anode cracking

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Salah Amrani ◽  
Duygu Kocaefe ◽  
Yasar Kocaefe ◽  
Dipankar Bhattacharyay ◽  
Mohamed Bouazara ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Crack Density ◽  
Raw Material ◽  
Carbon Anode ◽  
Know How ◽  
Production Parameters ◽  
Environmental Emissions ◽  
Carbon Anodes ◽  
Tomographic Analysis

AbstractCarbon anodes are used in the electrolytic production of aluminum. The quality of anodes is directly related to the production cost, carbon and energy consumption, and environmental emissions. It is desired that the anodes have high density, low porosity/cracks, low electrical resistivity as well as low air and CO2 reactivities. Low resistivity of anodes reduces energy required to produce aluminum during electrolysis. The presence of cracks and pores increases the anode electrical resistivity. Therefore, it is important to know how and when the pores and cracks form during the anode production so that the necessary actions could be taken to prevent their formation. A study was carried out to investigate the effect of different anode production parameters such as anode composition, type of raw material used, time and top-former bellow pressure of vibro-compactor, green anode cooling medium, and heating rate used during baking on the crack formation. The anodes are fabricated at the carbon laboratory of University of Quebec at Chicoutimi (UQAC) and characterized by measuring their properties (density, electrical resistivity, and surface crack density). The anode properties, hence the anode quality, were correlated with the anode production parameters. Also, their tomographic analysis was carried out to visualize and quantify the internal cracks. Graphical abstract

scholarly journals A Unified Abaqus Implementation of the Phase Field Fracture Method Using Only a User Material Subroutine

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1913
Author(s):  
Yousef Navidtehrani ◽  
Covadonga Betegón ◽  
Emilio Martínez-Pañeda
Keyword(s):  
Phase Field ◽  
Crack Nucleation ◽  
Crack Density ◽  
Contact Problems ◽  
Element Mesh ◽  
Robust Implementation ◽  
Current Implementation ◽  
User Material Subroutine ◽  
Complex Crack ◽  
Monolithic Solution

We present a simple and robust implementation of the phase field fracture method in Abaqus. Unlike previous works, only a user material (UMAT) subroutine is used. This is achieved by exploiting the analogy between the phase field balance equation and heat transfer, which avoids the need for a user element mesh and enables taking advantage of Abaqus’ in-built features. A unified theoretical framework and its implementation are presented, suitable for any arbitrary choice of crack density function and fracture driving force. Specifically, the framework is exemplified with the so-called AT1, AT2 and phase field-cohesive zone models (PF-CZM). Both staggered and monolithic solution schemes are handled. We demonstrate the potential and robustness of this new implementation by addressing several paradigmatic 2D and 3D boundary value problems. The numerical examples show how the current implementation can be used to reproduce numerical and experimental results from the literature, and efficiently capture advanced features such as complex crack trajectories, crack nucleation from arbitrary sites and contact problems. The code developed is made freely available.

scholarly journals Optimizing Laser Powder Bed Fusion Parameters for IN-738LC by Response Surface Method

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4879
Author(s):  
Mireia Vilanova ◽  
Rubén Escribano-García ◽  
Teresa Guraya ◽  
Maria San Sebastian
Keyword(s):  
Response Surface ◽  
Response Surface Method ◽  
Process Parameters ◽  
Crack Density ◽  
Processing Parameters ◽  
Optimum Process ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Surface Method

A method to find the optimum process parameters for manufacturing nickel-based superalloy Inconel 738LC by laser powder bed fusion (LPBF) technology is presented. This material is known to form cracks during its processing by LPBF technology; thus, process parameters have to be optimized to get a high quality product. In this work, the objective of the optimization was to obtain samples with fewer pores and cracks. A design of experiments (DoE) technique was implemented to define the reduced set of samples. Each sample was manufactured by LPBF with a specific combination of laser power, laser scan speed, hatch distance and scan strategy parameters. Using the porosity and crack density results obtained from the DoE samples, quadratic models were fitted, which allowed identifying the optimal working point by applying the response surface method (RSM). Finally, five samples with the predicted optimal processing parameters were fabricated. The examination of these samples showed that it was possible to manufacture IN738LC samples free of cracks and with a porosity percentage below 0.1%. Therefore, it was demonstrated that RSM is suitable for obtaining optimum process parameters for IN738LC alloy manufacturing by LPBF technology.

An Overall Approach for Microcrack and Inhomogeneity Toughening in Brittle Solids

1999 ◽  
Vol 15 (2) ◽  
pp. 57-68
Author(s):  
Huang Hsing Pan
Keyword(s):  
Poisson Ratio ◽  
Crack Density ◽  
Mean Field ◽  
Analytic Form ◽  
Density Parameter ◽  
Brittle Solids ◽  
The Matrix ◽  
Microcrack Toughening ◽  
Average Quantity ◽  
The Mean

ABSTRACTBased on the weight function theory and Hutchinson's technique, the analytic form of the toughness change near a crack-tip is derived. The inhomogeneity toughening is treated as an average quantity calculated from the mean-field approach. The solutions are suitable for the composite materials with moderate concentration as compared with Hutchinson's lowest order formula. The composite has the more toughened property if the matrix owns the higher value of the Poisson ratio. The composite with thin-disc inclusions obtains the highest toughening and that with spheres always provides the least effective one. For the microcrack toughening, the variations of the crack shape do not significantly affect the toughness change if the Budiansky and O'Connell crack density parameter is used. The explicit forms for three types of the void toughening and two types of the microcrack toughening are also shown.

Modelling of the damage development in carbon/epoxy laminates subjected to combined seawater ageing and mechanical loading

2016 ◽  
Vol 232 (9) ◽  
pp. 761-768 ◽  
Author(s):  
N Carrere ◽  
N Tual ◽  
T Bonnemains ◽  
E Lolive ◽  
P Davies
Keyword(s):  
Applied Load ◽  
Epoxy Composite ◽  
Damage Model ◽  
Crack Density ◽  
Damage Threshold ◽  
Multiscale Approach ◽  
Damage Development ◽  
Finite Fracture Mechanics ◽  
Physically Based ◽  
Kinetics Of

In this study, a damage model that accounts for the effect of seawater ageing is proposed. The model is based on a failure criterion that takes into account the effect of the ply thickness, while the kinetics of the damage development are based on a Finite Fracture Mechanics approach. The stiffness degradation is identified by a multiscale approach. The parameters of the model are physically based which facilitates the identification and the coupling with the ageing. These and their evolution as a function of the time of immersion in seawater have been identified for a carbon/epoxy composite. The changes in crack density as a function of the applied load for three ageing times are quite well predicted by the model. The model explains why the damage threshold is strongly influenced by the ageing while the kinetics of the crack propagation remain quasi-constant.

scholarly journals Distribution of crack density parameter in Central Betic Cordillera (Southern Spain)

2013 ◽  
Vol 196 (1) ◽  
pp. 22-33 ◽  
Author(s):  
Inmaculada Serrano ◽  
Federico Torcal ◽  
José Morales
Keyword(s):  
Crack Density ◽  
Betic Cordillera ◽  
Southern Spain ◽  
Density Parameter

Multiscale fracture density analysis at Stromboli Volcano, Italy: implications to flank stability

2021 ◽  
Author(s):  
Thomas Alcock ◽  
Sergio Vinciguerra ◽  
Phillip Benson ◽  
Federico Vagnon
Keyword(s):  
Electrical Resistivity ◽  
Wave Velocity ◽  
Rift Zone ◽  
Pulse Generator ◽  
Average Length ◽  
Crack Density ◽  
P Wave ◽  
Fracture Density ◽  
Stromboli Volcano ◽  
P Wave Velocity

<p>Stromboli volcano has experienced four sector collapses over the past 13 thousand years, resulting in the formation of the Sciara del Fuoco (SDF) horseshoe-shaped depression and an inferred NE / SW striking rift zone across the SDF and the western sector of the island. These events have resulted in the formation of steep depressions on the slopes on the volcano where episodes of instability are continuously being observed and recorded. This study aims to quantify the fracture density inside and outside the rift zone to identify potential damaged zones that could reduce the edifice strength and promote fracturing. In order to do so we have carried out a multiscale analysis, by integrating satellite observations, field work and seismic and electrical resistivity analyses on cm scales blocks belonging to 11 lava units from the main volcanic cycles that have built the volcano edifice, ie. Paleostromboli, Nestromboli and Vancori. 0.5 m resolution Pleiades satellite data has been first used to highlight 23635 distinct linear features across the island. Fracture density has been calculated using Fracpaq based on the Mauldon et al (2001) method to determine the average fracture density of a given area on the basis of the average length of drawn segments within a predetermined circular area. 41.8 % of total fracture density is found around intrusions and fissures, with the summit area and the slopes of SDF having the highest average fracture density of 5.279  . Density, porosity, P- wave velocity in dry and wet conditions and electrical resistivity (in wet conditions) were measured  via an ultrasonic pulse generator and acquisition system (Pundit) and an on purpose built measuring quadrupole on cm scale blocks of lavas collected from both within and outside the proposed rift zone to assess the physical state and the crack damage of the different lava units.  Preliminary results show that P-wave velocity between ~ 2.25 km/s < Vp < 5km/s decreases with porosity while there is high variability electrical resistivity with 21.7 < ρ < 590 Ohm * m. This is presumably due to the lavas texture and the variable content of bubble/vesicles porosity and crack damage, that is reflected by an effective overall porosity between 0 and 9 %. Higher porosity is generally mirrored by lower p-wave velocity values. Neostromboli blocks show the most variability in both P-wave velocity and electrical resistivity. Further work will assess crack density throughout optical analyses and systematically investigate the UCS and elastic moduli. This integrated approach is expected to provide a multiscale fracture density and allow to develop further laboratory testing on how slip surfaces can evolve to a flank collapse at Stromboli.</p>

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