scholarly journals Fracture Mechanism of Brazilian Discs with Multiple Parallel Notches Using PFC2D

2017 ◽  
Author(s):  
Vahab Sarfarazi ◽  
Hadi Haeri ◽  
Mohammad Fatehi
Keyword(s):  
Laboratory Tests ◽  
Numerical Models ◽  
Compressive Loading ◽  
Brazilian Test ◽  
Numerical Results ◽  
Particle Flow Code ◽  
Tensile Crack ◽  
Joint Spacing ◽  
Joint Configuration ◽  
Experimental Laboratory

This study presents crack initiation, propagation and coalescenceat or near pre-existing open cracks in a numericalmodel under Brazilian test. Firstly, Particle Flow Code intwo dimensions (PFC2d) was calibrated with respect to thedata obtained from experimental laboratory tests to ensurethe conformity of the simulated numerical models response.Brazilian discs contain one, two, three, four, and five parallelcentred cracks (45° to the horizontal) under compressiveline loading. Models containing two and three cracks havedifferent joint spacing and joint configuration. In model consistingone flaws, tensile cracks initiated from notch tip andpropagates in direction of compressive loading till coalescewith model edge. By increasing the number of notch, first typeof tensile crack initiated at the tips of outer flaws and coalescedwith model edge. Also second type of tensile cracksinitiates from middle of inner flaws and coalesce with tip ofthe neighbouring flaws. The results show that joint spacingand joint configuration has important effect on the failure patternin model consisting two and three notch. Experimentaland numerical results rendered by other researchers showed agood agreement with the numerical results in the coalescencecharacteristics in cracked model. In addition, crack initiationand coalescence stresses in models were analyzed and comparedwith those in the single-flawed model.

Analysis of TBM Tunnel Behavior in Jointed Rock Mass

2011 ◽  
Vol 90-93 ◽  
pp. 2033-2036 ◽  
Author(s):  
Jin Shan Sun ◽  
Hong Jun Guo ◽  
Wen Bo Lu ◽  
Qing Hui Jiang
Keyword(s):  
Rock Mass ◽  
Numerical Models ◽  
Jointed Rock ◽  
In Situ Stress ◽  
Jointed Rock Mass ◽  
Joint Orientation ◽  
Joint Spacing ◽  
Factors Affecting ◽  
Dip Angle

The factors affecting the TBM tunnel behavior in jointed rock mass is investigated. In the numerical models the concrete segment lining of TBM tunnel is concerned, which is simulated as a tube neglecting the segment joint. And the TBM tunnel construction process is simulate considering the excavation and installing of the segment linings. Some cases are analyzed with different joint orientation, joint spacing, joint strength and tunnel depth. The results show that the shape and areas of loosing zones of the tunnel are influenced by the parameters of joint sets and in-situ stress significantly, such as dip angle, spacing, strength, and the in-situ stress statement. And the stress and deformation of the tunnel lining are influenced by the parameters of joint sets and in-situ stress, too.

scholarly journals Numerical Modeling of a Punch Penetration Test Using the Discrete Element Method

2020 ◽  
Vol 28 (2) ◽  
pp. 1-7
Author(s):  
Rouhollah Basirat ◽  
Jafar Khademi Hamidi
Keyword(s):  
Numerical Modeling ◽  
Discrete Element Method ◽  
Numerical Models ◽  
Confining Pressure ◽  
Discrete Element ◽  
Numerical Results ◽  
Strength Parameter ◽  
Penetration Test ◽  
Strength Parameters ◽  
Element Method

AbstractUnderstanding the brittleness of rock has a crucial importance in rock engineering applications such as the mechanical excavation of rock. In this study, numerical modeling of a punch penetration test is performed using the Discrete Element Method (DEM). The Peak Strength Index (PSI) as a function of the brittleness index was calculated using the axial load and a penetration graph obtained from numerical models. In the first step, the numerical model was verified by experimental results. The results obtained from the numerical modeling showed a good agreement with those obtained from the experimental tests. The propagation path was also simulated using Voronoi meshing. The fracture was created under the indenter in the first step, and then radial fractures were propagated. The effects of confining pressure and strength parameters on the PSI were subsequently investigated. The numerical results showed that the PSI increases with enhancing the confining pressure and the strength parameter of the rock, including cohesion and the friction angle. A new relationship between the strength parameters and PSI was also introduced based on two variable regressions of the numerical results.

Flow Fields Inside Stocked Fish Cages and the Near Environment

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Lars C. Gansel ◽  
Siri Rackebrandt ◽  
Frode Oppedal ◽  
Thomas A. McClimans
Keyword(s):  
Atlantic Salmon ◽  
Water Flow ◽  
Laboratory Tests ◽  
Numerical Models ◽  
Field Measurements ◽  
Flow Patterns ◽  
Fish Swimming ◽  
Swimming Depth ◽  
Starting Point ◽  
Fish Cages

This study explores the average flow field inside and around stocked Atlantic salmon (Salmo salar L.) fish cages. Laboratory tests and field measurements were conducted to study flow patterns around and through fish cages and the effect of fish on the water flow. Currents were measured around an empty and a stocked fish cage in a fjord to verify the results obtained from laboratory tests without fish and to study the effects of fish swimming in the cage. Fluorescein, a nontoxic, fluorescent dye, was released inside a stocked fish cage for visualization of three-dimensional flow patterns inside the cage. Atlantic salmon tend to form a torus shaped school and swim in a circular path, following the net during the daytime. Current measurements around an empty and a stocked fish cage show a strong influence of fish swimming in this circular pattern: while most of the oncoming water mass passes through the empty cage, significantly more water is pushed around the stocked fish cage. Dye experiments show that surface water inside stocked fish cages converges toward the center, where it sinks and spreads out of the cage at the depth of maximum biomass. In order to achieve a circular motion, fish must accelerate toward the center of the cage. This inward-directed force must be balanced by an outward force that pushes the water out of the cage, resulting in a low pressure area in the center of the rotational motion of the fish. Thus, water is pulled from above and below the fish swimming depth. Laboratory tests with empty cages agree well with field measurements around empty fish cages, and give a good starting point for further laboratory tests including the effect of fish-induced currents inside the cage to document the details of the flow patterns inside and adjacent to stocked fish cages. The results of such experiments can be used as benchmarks for numerical models to simulate the water flow in and around net pens, and model the oxygen supply and the spreading of wastes in the near wake of stocked fish farms.

Physics-Based Friction Model With Potential Application in Numerical Models for Tire-Road Traction

2017 ◽  
Author(s):  
Anahita Emami ◽  
Seyedmeysam Khaleghian ◽  
Chuang Su ◽  
Saied Taheri
Keyword(s):  
Theoretical Model ◽  
Friction Coefficient ◽  
Numerical Models ◽  
Surface Profile ◽  
Viscoelastic Behavior ◽  
Numerical Results ◽  
Experimental Results ◽  
Real Contact Area ◽  
Computer Algorithms ◽  
Road Surfaces

Good understanding of friction in tire-road interaction is of critical importance for vehicle dynamic control systems. Most of the friction models proposed to describe the friction coefficient between tire-treads and road surfaces have been developed based on empirical or semi-empirical relations that are not able to include many effective parameters involved in the tire-road interactions. Therefore, these models are just useful in limited conditions similar to the experiments, and do not accurately represent tire-road traction in numerical tire models. However, in last two decades, a few theoretical models have been developed to calculate the tire-road friction coefficient theoretically by considering both viscoelastic behavior of tire tread compounds and multi-scale interactions between tire treads and rough road surfaces. In this article, a novel physics-based model proposed by Persson has been investigated and used to develop computer algorithms for calculation of sliding friction coefficient between a tire tread compound and a rough substrate. The viscoelastic behavior of tread compound and the surface profile of rough counter surface are the inputs of this physics-based theoretical model. The numerical results of the model have been compared with the experimental results obtained from a dynamic friction tester designed and built in the Center for Tire Research (CenTire). Good agreement between numerical results of theoretical model and experimental results has been found at intermediate range of slip velocities considering the effect of adhesion and shearing in the real contact area in addition to hysteresis friction due to internal energy dissipation in the tire tread compound.

GPR laboratory tests and numerical models to characterize cracks in cement concrete specimens, exemplifying damage in rigid pavement

Measurement ◽  
2020 ◽  
Vol 158 ◽  
pp. 107662 ◽  
Author(s):  
Mezgeen A. Rasol ◽  
Vega Pérez-Gracia ◽  
Francisco M. Fernandes ◽  
Jorge C. Pais ◽  
Sonia Santos-Assunçao ◽  
...  
Keyword(s):  
Laboratory Tests ◽  
Numerical Models ◽  
Cement Concrete ◽  
Rigid Pavement

scholarly journals Investigating the Effect of Stepped Scarf Repair Ratio in Repaired CFRP Laminates under Compressive Loading

2020 ◽  
Vol 4 (4) ◽  
pp. 153
Author(s):  
Spyridon Psarras ◽  
Theodoros Loutas ◽  
Magdalini Papanaoum ◽  
Orestis Konstantinos Triantopoulos ◽  
Vasilis Kostopoulos
Keyword(s):  
Numerical Models ◽  
Compressive Loading ◽  
Composite Plates ◽  
Step Length ◽  
Critical Threshold ◽  
Cfrp Laminates ◽  
Threshold Size ◽  
Repair Patch ◽  
Parametric Studies ◽  
Strength And Stiffness

In this work the effectiveness of stepped repairs to damaged fiber reinforced composite materials is investigated by using previously validated numerical models which were compared with tested repaired composite plates. Parametric studies were carried out in order to assess the scarf ratio (i.e., step length to ply thickness ratio) influence on ultimate forces, displacements, stresses and stiffnesses. FE models with repair scarf ratios varying from the value of 20 to the value 60 with a step increase of 10 were developed. The numerical models allowed a direct comparison of the influence that the scarf ratio had to the strength and stiffness restoration of the repaired composite structure. The study verifies that the restoration of the strength of a damaged laminate depends largely on the size of the repair patch. Generally, the bigger the size of a patch, the stronger the repaired structure is, up to a critical threshold size. To maximize the strength restoration, it is advised that the number of steps in each patch are no less than the number of plies on the base laminate.

scholarly journals Influence of Bedding Planes on the Mechanical Characteristics and Fracture Pattern of Transversely Isotropic Rocks in Direct Shear Tests

2018 ◽  
Vol 2018 ◽  
pp. 1-14
Author(s):  
Lei Xia ◽  
Yawu Zeng ◽  
Rong Luo ◽  
Wei Liu
Keyword(s):  
Mechanical Characteristics ◽  
Numerical Models ◽  
Transversely Isotropic ◽  
Bedding Plane ◽  
Particle Flow Code ◽  
Fracture Plane ◽  
Direct Shear ◽  
Geometrical Properties ◽  
Bedding Planes ◽  
Fracture Patterns

Bedding planes are the primary control on the anisotropy of mechanical characteristics and fracture patterns in rock. To analyze the influence of the geometrical properties of bedding planes on the direct shear strength characteristics and fracture patterns of transversely isotropic rocks, numerical models were established using an improved modeling method using Particle Flow Code. The results of the numerical model were in good agreement with those of the physical experiments of an artificial rock mass containing a single bedding plane. The results show that the shear fractures with a range of bedding plane geometries can be divided into two patterns. When the inclination angles of the bedding planes were larger or smaller, a thoroughgoing fracture plane was formed near the preexisting shear fracture plane. On the other hand, the intact rock was broken into many parallel sheets.

Vulnerability Analyses of Structural Insulated Panels with OSB Skins Strengthened by Basalt Fiber Cloth Subjected to Windborne Debris Impact

2018 ◽  
Vol 18 (06) ◽  
pp. 1850088 ◽  
Author(s):  
Qingfei Meng ◽  
Wensu Chen ◽  
Hong Hao
Keyword(s):  
Numerical Model ◽  
Numerical Models ◽  
Basalt Fiber ◽  
Numerical Results ◽  
Dynamic Responses ◽  
Back Side ◽  
Basalt Fibre ◽  
Structural Insulated Panels ◽  
Windborne Debris ◽  
Debris Impact

In this study, numerical simulations are conducted with a verified model to develop damage threshold curves for structural insulated panels (SIPs) with OSB skins strengthened by basalt fiber cloth subjected to windborne debris impact. Numerical models of the SIP with OSB skins strengthened by basalt fibre cloth at the front or back side are developed by using LS-DYNA. The accuracy of the numerical model is verified by comparing numerical results with laboratory testing data. Using the verified numerical model, intensive simulations are conducted to examine the influence of various parameters, including thickness of basalt fiber, location of basalt fiber layer, bonding strength between the basalt fiber cloth and the OSB skin, on the dynamic responses of the SIP. The debris penetration or fracture of the strengthened SIP that creates an opening is defined as failure of the panel in this study. Empirical formulae are derived on the basis of the numerical results to predict the thresholds of penetration velocity and projectile mass that lead to failure of the SIP. The empirical formulae can be straightforwardly used to assess the performance of the SIP with OSB skins strengthened by basalt fiber cloth subjected to windborne debris impact.

Numerical-Experimental Study of the Gas LP Atmospheric Burner

2010 ◽  
Author(s):  
A. Rami´rez-Barro´n ◽  
A. Aguilar-Moreno ◽  
A. Gallegos-Mun˜oz ◽  
J. M. Riesco-A´vila ◽  
S. Marti´nez-Marti´nez ◽  
...  
Keyword(s):  
Experimental Study ◽  
Temperature Distribution ◽  
Numerical Models ◽  
Numerical Results ◽  
Experimental Results ◽  
Thermal Camera

A numerical-experimental study of the gas LP atmospheric burner used in the ceramist furnace is presented. A new design of the burner was proposed to obtain a temperature distribution in the furnace better that the temperature distribution obtained with the actual burner. The experimental study helped to know the temperature and flame distribution in the furnace that permit to achieve the temperature of baking of the ceramic. The experimental results were obtained with a thermal camera and thermocouples placed in the furnace. Numerical models were developed with CFD (Fluent ®) comparing the results with the experimental results to obtain the new design of the burner. The experimental and numerical results permitted to identify the zones with temperature near to the temperature of baking, which is reached in the high and intermediate zones of the furnace. Then it is necessary a recirculation of the hot gases toward the low zone of the furnace.

Sign in / Sign up

Export Citation Format

Share Document