Numerical modelling of the crack-pore interaction and damage evolution behaviour of rocklike materials with pre-existing cracks and pores

2020 ◽  
pp. 105678952098387
Author(s):  
PLP Wasantha ◽  
D Bing ◽  
SQ Yang ◽  
T Xu
Keyword(s):  
Principal Stress ◽  
Damage Evolution ◽  
Shear Failure ◽  
Mechanical Response ◽  
Distribution Patterns ◽  
Stress Distributions ◽  
Compressive Stresses ◽  
Major Principal Stress ◽  
The Right ◽  
Macroscopic Failure

The combined effect of pre-existing cracks and pores on the damage evolution behaviour and mechanical properties of rocklike materials under uniaxial compression was numerically studied. Simulations of cracks and pores alone showed that increasing crack length and pore diameter decrease uniaxial compressive strength (UCS) and elastic modulus. Subsequent simulations considered two types of combinations of pre-existing cracks and pores – two cracks either side of a centric pore, and two pores either side of a centric crack – and the distance between cracks and pores was changed. In the case of two cracks at either side of the pore, UCS increased only slightly when the distance between the cracks and pore was increased. This was attributed to the more profound effect of the presence of the pore on UCS, and was confirmed by the progressive crack development characteristics and the major principal stress distribution patterns, which showed that the cracks initiated from the tips of the two pre-existing cracks made little or no contribution to the ultimate macroscopic failure. In contrast, models with two pores at either side of a centric crack showed a marked dependency of UCS on the distance between the pores and the crack. Cracks propagating from pre-existing pores made a greater contribution to the ultimate macroscopic failure when the pores were close to the centric crack and the effect gradually diminished with increasing space between pre-existing pores and the centric crack. Major principal stress distributions showed an asymmetric mobilisation of compressive stresses at the right and left sides of the two pores, favouring macroscopic shear failure when they were close to the centric crack which had led to a lower UCS. Overall, this study presents some critical insights into crack-pore interaction behaviour and the resulting mechanical response of rocklike materials to assist with the design of rock structures.

Load transfer across a mandible during a mastication cycle: The effects of odontogenic tumour

2020 ◽  
Vol 234 (5) ◽  
pp. 486-495
Author(s):  
Abir Dutta ◽  
Kaushik Mukherjee ◽  
Venkata Sundeep Seesala ◽  
Kaushik Dutta ◽  
Ranjan Rashmi Paul ◽  
...  
Keyword(s):  
Principal Stress ◽  
Potential Risk ◽  
Pathological Fracture ◽  
Load Transfer ◽  
The Body ◽  
Patient Specific ◽  
Stress Distributions ◽  
Odontogenic Tumour ◽  
Odontogenic Tumours ◽  
The Right

The extent to which load transfer in a diseased mandible with odontogenic tumour might influence the potential risk of pathological fracture has scarcely been investigated. The study sought to investigate the quantitative deviations in load transfer across healthy and cancer-affected (diseased) mandibles having odontogenic tumours. The effect of size of the tumours (small: 9 mm diameter, large: 19 mm diameter), and variation in bone mechanical (elastic) properties of the mandible on load transfer in cancer-affected mandibles during a mastication cycle have been investigated. Based on patient-specific computed tomography–scan datasets, detailed three-dimensional finite element models of healthy and diseased mandibles were developed. High stresses of 25–30 MPa and strains ∼700 µε were observed in the healthy mandible during the right molar bite. However, marginal deviations were observed in principal stress distributions in the diseased mandibles with small- and large-sized tumours, as compared to the healthy mandible. Maximum principal strains of ∼1474 µε were found in the body region adjacent to the symphysis region for small-sized tumour. Whereas for large-sized tumour, maximum strains of ∼2700 µε were observed in the right buccal regions. Reduction in Young’s modulus due to different stages of odontogenic tumours had a localised effect on the principal stress distributions, but triggered an abrupt increase in the principal tensile strains. It appears that there is a potential risk of pathological fracture for large-sized odontogenic tumour, owing to high tensile stresses and strains.

Experimental and numerical analysis of shear process of a high particle content bonding material

2021 ◽  
pp. 1-26
Author(s):  
Yizhan Yang ◽  
Jiliang Li ◽  
Jiankang Chen
Keyword(s):  
Shear Band ◽  
Damage Evolution ◽  
Shear Failure ◽  
Mechanical Response ◽  
Failure Process ◽  
Compressive Loading ◽  
Adjustment Process ◽  
Particle Content ◽  
High Particle ◽  
Shear Process

Abstract In this study, polymer-bonded sugar (PBS) is used as an substitute material for polymer-bonded explosive (PBX), and the shear failure process of PBS under compressive loading. Firstly, the shear failure process of PBS was analyzed by a series of experiments, and it was found that the shear band appearing on the surface of the specimen was not symmetrical. Further theory analysis showed that it was triggered by the evolution of asymmetric damage caused by internal defects in the material. In addition, through investigating the distribution of experimental scatters, we found that the material undergoes a relatively long period of internal microstructure adjustment before shear failure occurs, this adjustment will undoubtedly affect the evolution of shear band. More importantly, a data density method was used to quantify the adjustment process. Finally, by using finite element simulation, the effects of matrix-particle-interface strength on the mechanical response or damage evolution of the PBS were thoroughly examined. This research has reference significance for understanding the damage evolution process of high particle content composite materials.

Muscular blood flow distribution patterns as a function of running speed in rats

1982 ◽  
Vol 243 (2) ◽  
pp. H296-H306 ◽  
Author(s):  
M. H. Laughlin ◽  
R. B. Armstrong
Keyword(s):  
Blood Flow ◽  
Muscle Blood Flow ◽  
Flow Distribution ◽  
Distribution Patterns ◽  
Left Renal Artery ◽  
Sprague Dawley ◽  
Vastus Intermedius ◽  
Slow Twitch ◽  
The Right ◽  
White Gastrocnemius

Muscle blood flow (BF) was measured using the radiolabeled microsphere technique within and among nine major muscles of rats before exercise and during treadmill walking or running at speeds of 15, 30, 45, 60, and 75 m/min. Measurements were made during exercise after 1 min of steady walking or running. Male Sprague-Dawley rats were chronically instrumented with 2 Silastic catheters, one in the ascending aorta via the right carotid artery for microsphere infusion and one in the left renal artery for arterial reference blood sample withdrawal. The preexercise results demonstrated that 1) BF to deep slow-twitch muscles was three to four times that to peripheral fast muscles (e.g., soleus and gastrocnemius BFs were 138 and 33 ml . min-1 . 100 g-1, respectively); 2) BFs to red portions within mixed muscles were three to four times those to white portions (e.g, red and white gastrocnemius BFs were 54 and 18 ml . min-1 . 100 g-1, respectively; and 3) there was a direct relationship (P less than 0.05) between BFs to muscles and their slow-twitch oxidative fiber populations. The results obtained during exercise demonstrated that 1) at the slowest speed studied (15 m/min) BFs to the red portions of muscles increased, whereas BFs to the white portions of the same muscles decreased; 2) BFs to all muscles (except soleus) were increased during running at 75 m/min when there was a range of flows of 30 ml . 100 g-1 . min-1 (white gastrocnemius) to 321 (vastus intermedius), 3) at all running speeds the increases in BF to muscles were directly related to the fast-twitch, high-oxidative fiber populations of the muscles; and 4) BFs to visceral tissues and fat were decreased during exercise.

scholarly journals Factors Influencing Ore Recovery and Unplanned Dilution in Sublevel Open Stopes. Case study of Shaft No.4 at Konkola Mine, Zambia

2020 ◽  
Vol Special Issue (1) ◽  
Author(s):  
Kalunga Ngoma ◽  
Victor Mutambo
Keyword(s):  
Numerical Modelling ◽  
Principal Stress ◽  
Underground Mining ◽  
Poisson Ratio ◽  
High Stress ◽  
Geological Strength Index ◽  
Total Displacement ◽  
Ground Conditions ◽  
Geological Discontinuities ◽  
Major Principal Stress

Konkola Copper Mine’s Number 4 Shaft is a trackless underground mine applying sublevel open stoping (SLOS) mining method. Number 4 shaft wants to increase ore production from 1 million metric tonnes per annum to 3 million metric tonnes per annum in the next 5 years but ore recovery is 70% or less and dilution is 20% or more. In order to achieve the desired annual target of 3 million metric tonnes ore recovery should be increased from70% to (≥85%) and dilution should be reduced from 20% to (≤10%). Despite being one of the most used underground mining methods, the current SLOS has a challenge of high unplanned dilution. This paper reviews and evaluates parameters that influence recovery and unplanned dilution in sublevel open stopes and applies numerical modelling using PHASE2 software to establish the influence of stress environment on unplanned dilution at the mine. The input parameters for numerical modelling were: Uniaxial Compressive strength (UCS=170MPa), Geological Strength Index (GSI) =55, Young’s Modulus (E) =26000MPa, Hoek-Brown constant (s) =0.0067, Hoek-Brown constant (mi) =20 and Poisson ratio (v) =0.2 major principal stress (σ1) 39MPa, intermediate stress (σ2= 18MPa) and the minor principal stress (σ3= 15MPa). Results obtained from review of mine production records indicate that the main factors that influence unplanned dilution at Number 4 shaft are: poor ground conditions, lack of compliance to recommended stope designs, poor drilling and blasting practices, presence of geological discontinuities, adopted mining sequence of extracting high ore grade first that leads to creation of high stress blocks within the orebody and delayed mucking practice. Results obtained from PHASE 2D model indicate that total displacement of 90mm is recorded in the hangingwall hence influencing stope wall instability that leads to increased unplanned dilution. After stope extraction, it was observed that 60MPa of induced stress developed at the top right corner and 45-50 MPa at the crown pillar and right bottom corner of the stope.

scholarly journals Study on Electric-Magnetic-Acoustic Signal Regularity and Its Correlation during Rock Shear Failure

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Huilin Jia ◽  
Yue Niu ◽  
Xiaofei Liu ◽  
Enyuan Wang
Keyword(s):  
Acoustic Signal ◽  
Damage Evolution ◽  
Shear Failure ◽  
Tracking System ◽  
Correlation Coefficients ◽  
Coupling Model ◽  
Electric Signal ◽  
Rock Materials ◽  
Coal Rock ◽  
Electric Signals

http://mts.hindawi.com/update/) in our Manuscript Tracking System and after you have logged in click on the ORCID link at the top of the page. This link will take you to the ORCID website where you will be able to create an account for yourself. Once you have done so, your new ORCID will be saved in our Manuscript Tracking System automatically."?>During mining activities, the deformation and damage of coal rock materials might result in coal rock dynamic disasters, such as rock burst. It leads to serious casualties and property losses. Generally, the occurrence of dynamic failure of coal and rock are caused by shear failure of coal seam. Geophysics signals are generated and related to damage evolution in this loading process. In this paper, sandstone samples were subjected to shear failure laboratory experiments, and the electric-magnetic-acoustic signal regularity was measured and analyzed comparatively. The results indicated magnetic signals were more correlated with stress and acoustic emission (AE) signals, while the amplitude of electric signal fluctuation was larger when main failure occurred. With the increase of sample size and shear strength, the strength of electric-magnetic-acoustic signals increased. The correlation coefficients between the magnetic signal and stress as well as AE energy were superior to those of electric signals. The coupling model between AE and electric signals was established, which shows good statistical correlation. This study lays the foundations for further interpreting the generation mechanism of the electric signal. It provides a new method to indicate the damage evolution of coal rock materials.

scholarly journals A finite dissipative theory of temporary interfibrillar bridges in the extracellular matrix of ligaments and tendons

2008 ◽  
Vol 6 (39) ◽  
pp. 909-924 ◽  
Author(s):  
P. Ciarletta ◽  
M. Ben Amar
Keyword(s):  
Extracellular Matrix ◽  
Damage Evolution ◽  
Structural Integrity ◽  
Mechanical Response ◽  
Collagen Type I ◽  
State Theory ◽  
Ground Substance ◽  
Type I ◽  
Dissipative Effects ◽  
Rate Dependent

The structural integrity and the biomechanical characteristics of ligaments and tendons result from the interactions between collagenous and non-collagenous proteins (e.g. proteoglycans, PGs) in the extracellular matrix. In this paper, a dissipative theory of temporary interfibrillar bridges in the anisotropic network of collagen type I, embedded in a ground substance, is derived. The glycosaminoglycan chains of decorin are assumed to mediate interactions between fibrils, behaving as viscous structures that transmit deformations outside the collagen molecules. This approach takes into account the dissipative effects of the unfolding preceding fibrillar elongation, together with the slippage of entire fibrils and the strain-rate-dependent damage evolution of the interfibrillar bridges. Thermodynamic consistency is used to derive the constitutive equations, and the transition state theory is applied to model the rearranging properties of the interfibrillar bridges. The constitutive theory is applied to reproduce the hysteretic spectrum of the tissues, demonstrating how PGs determine damage evolution, softening and non-recoverable strains in their cyclic mechanical response. The theoretical predictions are compared with the experimental response of ligaments and tendons from referenced studies. The relevance of the proposed model in mechanobiology research is discussed, together with several applications from medical practice to bioengineering science.

On the Biaxial Mechanical Response of Porcine Tricuspid Valve Leaflets

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Keyvan Amini Khoiy ◽  
Rouzbeh Amini
Keyword(s):  
Tricuspid Valve ◽  
Computational Models ◽  
Mechanical Response ◽  
Ex Vivo ◽  
Biaxial Stress ◽  
Strain Behavior ◽  
Highly Nonlinear ◽  
Rapid Transition ◽  
Biaxial Tensile Testing ◽  
The Right

Located on the right side of the heart, the tricuspid valve (TV) prevents blood backflow from the right ventricle to the right atrium. Similar to other cardiac valves, quantification of TV biaxial mechanical properties is essential in developing accurate computational models. In the current study, for the first time, the biaxial stress–strain behavior of porcine TV was measured ex vivo under different loading protocols using biaxial tensile testing equipment. The results showed a highly nonlinear response including a compliant region followed by a rapid transition to a stiff region for all of the TV leaflets both in the circumferential and in the radial directions. Based on the data analysis, all three leaflets were found to be anisotropic, and they were stiffer in the circumferential direction in comparison to the radial direction. It was also concluded that the posterior leaflet was the most anisotropic leaflet.

scholarly journals MULTIFRACTAL ANALYSIS OF MOUNT St. HELENS SEISMICITY AS A TOOL FOR IDENTIFYING ERUPTIVE ACTIVITY

Fractals ◽  
2006 ◽  
Vol 14 (03) ◽  
pp. 179-186 ◽  
Author(s):  
FILIPPO CARUSO ◽  
SERGIO VINCIGUERRA ◽  
VITO LATORA ◽  
ANDREA RAPISARDA ◽  
STEPHEN MALONE
Keyword(s):  
Time Distribution ◽  
Multifractal Analysis ◽  
Mechanical Response ◽  
Fractal Dimensions ◽  
Distribution Patterns ◽  
Fixed Number ◽  
Short Time Scale ◽  
Eruptive Activity ◽  
Seismic Swarms ◽  
Mount St Helens

We present a multifractal analysis of Mount St. Helens seismic activity during 1980–2002. The seismic time distribution is studied in relation to the eruptive activity, mainly marked by the 1980 major explosive eruptions and by the 1980–1986 dome building eruptions. The spectrum of the generalized fractal dimensions, i.e. Dq versus q, extracted from the data, allows us to identify two main earthquake time distribution patterns. The first one exhibits a multifractal clustering correlated to the intense seismic swarms of the dome building activity. The second one is characterized by an almost constant value of Dq ≈ 1, as for a random uniform distribution. The time evolution of Dq (for q = 0.2), calculated on a fixed number of events window and at different depths, shows that the brittle mechanical response of the shallow layers to rapid magma intrusions, during the eruptive periods, is revealed by sharp changes, acting at a short time scale (order of days), and by the lowest values of Dq (≈ 0.3). Conversely, for deeper earthquakes, characterized by intense seismic swarms, Dq do not show obvious changes during the whole analyzed period, suggesting that the earthquakes, related to the deep magma supply system, are characterized by a minor degree of clustering, which is independent of the eruptive activity.

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