X-direction Stress Research Articles

Effect of prefabricated flaw angle on the mechanical properties and failure characteristics of stratified cemented tailings backfill

The process of exposing stratified cemented tailings backfill (SCTB) underground is prone to damage due to blasting disturbances. To investigate the effect of flaws on the mechanical properties and failure characteristics of exposed SCTB, prefabricated flaws were used to simulate blasting damage. In this study, a uniaxial compression test, based on the digital image correlation (DIC) method, was used to investigate the mechanical characteristics of SCTB under different flaw dip angles. Additionally, the Particle Flow Code program was used to analyze the propagation of secondary cracks. The results show that: (1) With an increase in the flaw angle, the uniaxial compressive strength (UCS) of SCTB samples exhibit an initial decrease followed by an increase, and the elastic modulus of SCTB samples exhibit an increase. (2) When the flaw angle is between 0° and 45°, wing cracks and resistance tensile cracks mainly develop at the end of the flaw. For flaw angles between 60° and 75°, coplanar secondary cracks form at the end of the flaw and penetrate the stratified surface. (3) There are three main forms of crack propagation at the stratified surface: cracks passing through the stratified surface without deflecting, cracks deflecting at the stratified surface, and cracks that do not penetrate the stratified surface. (4) When cracks pass through the stratified surface without deflecting, the X-direction stress on both sides of the stratified surface changes synergistically, resulting in a large stress value. When the crack propagation direction deflects at the stratified surface, the X-direction stress differs on both sides, with smaller stress observed on the side away from the flaw. The larger the deflection angle of the crack propagation, the smaller the X-direction stress on the side away from the flaw. These results provide a basis for the stability evaluation and strength design of SCTB with flaws.

Thermal effect on the transient behavior of a piezomagnetic half-space subjected to dynamic anti-plane load

Considering the importance of understanding the propagation of transient waves in the piezomagnetic solids, the thermal effect on the transient behavior of a piezomagnetic half-space subjected to dynamic anti-plane load is investigated analytically in this paper. Using one-sided, two-sided Laplace transformation and Cagniard–de Hoop (CH) technique, an efficient and accurate analytical derivation for the solution of the anti-plane displacement, shear stress, magnetic potential, and induction in Laplace domain is presented. The study shows that the thermal stresses developed in x-axis and y-axis directions have significant influence on the transient response of the half-space. The magnetic induction B x increases obviously when the thermal stress is applied in x-axis direction, while it decreases when the thermal stress is applied in y-axis direction. Approaching time of magnetic induction B x and B y will become longer with higher thermal stress in x-axis direction. With the growth of the thermal stress in x-direction, contribution from the electromagnetic–elastic head (EH) wave increases, while the contribution from the shear elastic (SE) wave and the static value of shear stress decrease.

A Theory of Slope Shear Scouring and the Failure Mechanism of PFC3D on a Gangue Slope

In this paper, scouring shear failure theory is optimized based on the gangue slope near the thermal power field in Baiguo Town, Panzhou City, Guizhou Province. Based on the particle flow PFC (particle flow code) 3D fluid–solid coupling method, the scouring failure mechanism of ditch no. 5 of the gangue slope is comprehensively analyzed from the perspectives of the failure mode, displacement, motion track, and stress–strain. We consider the scouring shear theory in respect of (c, φ); this theory is dominated by two types of scouring intensity factors and can effectively explain the internal mechanisms of gully formation. The rainfall scouring failure of gangue slopes can be divided into four stages: (1) integral splash erosion and local pitting at the bottom of the slope; (2) erosion diversion and pitting in the slope; (3) the tributary–slope crest extension schist erosion stage; and (4) integral gully erosion and the landslide stage. The failure process is not only characterized by discontinuous failure but also occurs in the order of bottom–middle–branch–top. A three-section stepped effect is observed during the process in which the gangue is scoured and destroyed, which fully verifies the intermittent characteristics of the scouring and destruction of gangue slopes. During the whole process, the maximum displacement is concentrated at the top of the slope, and its proportions are as follows: top of the slope > tributary > middle of the slope > foot of the slope. The peak displacement of the slope crest in the horizontal Y-direction accounts for 41.76%, and that in the Z-direction accounts for 45.84%. Scouring deposits can be divided into the arc erosion deposit mode and the sector erosion deposit mode. Mainstream gullies primarily control whether deposits are characterized as arc or straight erosion deposits. The later stage of the second phase of scouring is the incubation period of the tributary gully. The large accumulation makes the stress at the bottom of the slope increase sharply, and the fluctuation value is between 2 and 6.8 MPa. The generation of the branch notch is mainly determined by X-direction stress, and 8.6 MPa is the critical stress. In efforts to prevent and control rainfall and landslide, the slope foot area should be preferentially protected, and the soil mass in the slope should be reduced to prevent the maximum energy fluctuation caused by scouring, so as to prevent significant displacement damage of the slope top.

ANALISIS SIFAT MEKANIK KOMPOSIT LAMINA BERPENGUAT SERAT KACA WOVEN DENGAN MATRIKS UNSATURATED POLYESTER 2504 APT

Polymer composites has anisotropic properties, if it receives stress from outside it will increase deformation in all directions. This study aims to determine the effect of composites lamina made from woven glass fibers on 2504 APT unsaturated polyester on tensile and flexural strength. The research methodology used is as follows: the process of making composites using the Hand-Lay Up method, the matrix volume fraction Vfm = 69, 39%, the fiber volume fraction Vfs = 30, 38%. The research parameters observed are the x-direction stress (sx) and the y-axis direction strees, (sy). The results obtained are the y-axis, (sy) = 0.8% greater than the x-axis. The flexural strength of the x-axis direction, (sbx) = 57,7% greater than the y-axis direction. The difference in the value of the tensile strength occurs in the number of different fiber bonds, while the flexural strength of the y direction occurs in the fiber lamina which increases more.

Experimental Study of Remotely Triggered Rockburst Induced by a Tunnel Axial Dynamic Disturbance Under True-Triaxial Conditions

During deep underground excavation, dynamic ejection failure of a highly stressed rock mass near an excavated boundary is easily triggered by a dynamic disturbance in the tunnel axial direction, induced by blasting on the tunnel face. Such a dynamic ejection failure is usually called remotely triggered rockburst, and it poses a threat to underground construction. To clarify the characteristics of remotely triggered rockburst, the development of remotely triggered rockbursts of granite rock specimens was investigated using an improved true-triaxial test system. Experimental results show that with increasing static Z-direction stress (i.e., in situ tangential stress on the cross section of the tunnel), rockburst is triggered more easily and the kinetic energy of ejected fragments increases. Under other constant static stresses and dynamic disturbance, with increasing horizontal stress including X-direction stress (i.e., in situ axial stress) or Y-direction stress (i.e., in situ radial stress on the cross section of the tunnel), rockburst is more difficult to trigger and the kinetic energy of the ejected fragments decreases. Under constant static stresses, once the amplitude and frequency of the dynamic loading exceed their thresholds, the rockburst intensity increases rapidly and the rockburst can be triggered much more easily with small increments of the amplitude and frequency. Furthermore, Z-direction strain increases during the dynamic disturbance process, indicating that the ultimate energy-storage capacity of the specimen decreases with increasing damage. When the elastic strain energy is greater than the ultimate energy-storage capacity of the damaged specimen, part of the residual elastic energy is converted into kinetic energy of the ejected fragments.

Stress distribution of IGZO TFTs under mechanical rolling using finite element method for flexible applications

The stress analysis of IGZO TFT in structures, dielectrics, and rolling curvatures using finite element method is proposed. The inverted-coplanar with SiOx has the smallest stress for mechanical rolling. The local extreme stress would also induce film cracks or peeling at the corner. For example, inverted-coplanar structure has the maximum stress at the corner of IGZO/Al with −0.65GPa (x-direction stress), −0.22GPa (y-direction stress), and −0.21GPa (shear stress). The stress of IGZO TFT with high PPI under mechanical rolling is also discussed.

Bar와 Beam 구조물의 기본적인 유한요소 모델의 수치해석

The finite element analysis (FEA) is a numerical technique to find solutions of field problems. A field problem is approximated by differential equations or integral expressions. In a finite element, the field quantity is allowed to have a simple spatial variation in terms of linear or polynomial functions. This paper represents a review and an accuracy-study of the finite element method comparing the FEA results with the exact solution. The exact solutions were calculated by solid mechanics and FEA using matrix stiffness method. For this study, simple bar and cantilever models were considered to evaluate four types of basic elements - constant strain triangle (CST), linear strain triangle (LST), bi-linear-rectangle(Q4),and quadratic-rectangle(Q8). The bar model was subjected to uniaxial loading whereas in case of the cantilever model moment loading was used. In the uniaxial loading case, all basic element results of the displacement and stress in x-direction agreed well with the exact solutions. In the moment loading case, the displacement in y-direction using LST and Q8 elements were acceptable compared to the exact solution, but CST and Q4 elements had to be improved by the mesh refinement.

Structure of a macroporous silica film as an interlayer of a laminated glass

A macroporous silica film (MSF) was introduced as a buffer layer of material between a silicate glass (SG) layer and a polyurethane (PU) layer to form a new aeronautic laminated glass. Structure simulations of MSF were performed using the ANSYS software. Pore models, porosity factor models, and thickness models were established. X-direction stress, Y-direction stress, and equivalent stress of the models were determined. Simulation results indicate that the pore can effectively depress shear stress on the MSF–PU interface. Moreover, maximum X-direction stress, maximum compressive stress, and maximum equivalent stress on the MSF–PU interface all decrease rapidly and then increase slowly by increasing film thickness.

Numerical investigation of dynamic crack branching under biaxial loading

Dynamic crack growth and branching of a running crack under various biaxial loading conditions in homogeneous and heterogeneous brittle or quasi-brittle materials is investigated numerically using RFPA2D (two-dimensional rock failure process analysis)-Dynamic program which is fully parallelized with OpenMP directives on Windows. Six 2D models were set up to examine the effect of biaxial dynamic loading and heterogeneity on crack growth. The numerical simulation vividly depicts the whole evolution of crack and captured the crack path and the angles between branches. The path of crack propagation for homogenous materials is straight trajectory while for heterogeneous materials is curved. Increasing the ratio of the loading stress in x-direction to the stress in y-direction, the macroscopic angles between branches become larger. Some parasitic small cracks are also observed in simulation. For heterogeneous brittle and quasi-brittle materials coalescence of the microcracks is the mechanism of dynamic crack growth and branching. The crack tip propagation velocity is determined by material properties and independent of loading conditions.

Microscopic Mechanics of Debris Accumulation Body with Expansive Fine Grain and PFC Numerical Simulation

To study the influence mechanism of the excavation stability of the debris accumulation body by the expansive fine grain, it has used by Particle Flow Code, based on indoor test, the fine-grain expansive effect has divided into fine-grain intensity attenuation and volume expansion, and it has linear decreased down from the surface on the accumulation body. Based on the contrastive analysis between simulated result and traditional finite element, the Particle Flow Code is more accurate and true. The analysis result has suggested that when consider the expansive action, the damage model is changed into surface sliding from part slump, and the X-direction stress added 20kPa in the interior of the accumulation body, and the whole sliding force added 30% more or less. At present, the field excavation situation is consistent with the calculation result.

Finite Element Method Analysis of the Deformation of Human Red Blood Cells

An erythrocyte and a spherocyte are subjected to aspiration pressure with a micropipette and analyzed by the finite element method (FEM). The comparison of the erythrocyte and the spherocyte indicates that the y-direction displacement of the erythrocyte was larger than that of the spherocyte under the same aspiration pressure. The x-direction stress distributions show that it is easier to change the shape of the erythrocyte model than that of the spherocyte model because a force in the opposite direction appears in the erythrocyte. This force seems to move the erythrocyte membrane to its center. The results indicate that the shape of the erythrocyte membrane changes partially under aspiration pressure at the point of contact with the micropipette and aspiration pressure. The results also indicate that the shape of the spherocyte membrane changes under aspiration pressure, but not only at a point of contact with the micropipette and the area subject to aspiration pressure; the entire spherocyte membrane seem to change the shape.

Mechanical properties of woven banana fibre reinforced epoxy composites

In this paper, the experiments of tensile and flexural (three-point bending) tests were carried out using natural fibre with composite materials (Musaceae/epoxy). Three samples prepared from woven banana fibre composites of different geometries were used in this research. From the results obtained, it was found that the maximum value of stress in x-direction is 14.14 MN/m 2, meanwhile the maximum value of stress in y-direction is 3.398 MN/m 2. For the Young’s modulus, the value of 0.976 GN/m 2 in x-direction and 0.863 GN/m 2 in y-direction were computed. As for the case of three-point bending (flexural), the maximum load applied is 36.25 N to get the deflection of woven banana fibre specimen beam of 0.5 mm. The maximum stress and Young’s modulus in x-direction was recorded to be 26.181 MN/m 2 and 2.685 GN/m 2, respectively. Statistical analysis using ANOVA-one way has showed that the differences of results obtained from those three samples are not significant, which confirm a very stable mechanical behaviour of the composites under different tests. This shows the importance of this product and allows many researchers to develop an adequate system for producing a good quality of woven banana fibre composite which maybe used for household utilities.

Self-similar solution of the unsteady mixed convection flow in the stagnation point region of a rotating sphere

An analysis is performed to present a new self-similar solution of unsteady mixed convection boundary layer flow in the forward stagnation point region of a rotating sphere where the free stream velocity and the angular velocity of the rotating sphere vary continuously with time. It is shown that a self-similar solution is possible when the free stream velocity varies inversely with time. Both constant wall temperature and constant heat flux conditions have been considered in the present study. The system of ordinary differential equations governing the flow have been solved numerically using an implicit finite difference scheme in combination with a quasilinearization technique. It is observed that the surface shear stresses and the surface heat transfer parameters increase with the acceleration and rotation parameters. For a certain value of the acceleration parameter, the surface shear stress in x-direction vanishes and due to further reduction in the value of the acceleration parameter, reverse flow occurs in the x–component of the velocity profiles. The effect of buoyancy parameter is to increase the surface heat transfer rate for buoyancy assisting flow and to decrease it for buoyancy opposing flow. For a fixed buoyancy force, heating by constant heat flux yields a higher value of surface heat transfer rate than heating by constant wall temperature.

Self-similar solution of the unsteady flow in the stagnation point region of a rotating sphere with a magnetic field

The unsteady flow and heat transfer of a viscous incompressible electrically conducting fluid in the forward stagnation point region of a rotating sphere in the presence of a magnetic field are investigated in this study. The unsteadiness in the flow field is caused by the velocity at the edge of the boundary layer and the angular velocity of the rotating sphere, both varying continuously with time. The system of ordinary differential equations governing the flow is solved numerically. For some particular cases, an analytical solution is also obtained. It is found that the surface shear stresses in x- and y-directions and the surface heat transfer increase with the acceleration, the magnetic and the rotation parameters whether the magnetic field is fixed relative to the fluid or body, except that the surface shear stress in x-direction and the surface heat transfer decrease with increasing the magnetic parameter when the magnetic field is fixed relative to the body. For a certain value of the acceleration parameter, the surface shear stress in the x-direction vanishes while the surface shear stress in the y-direction and the surface heat transfer remain finite. Also, below a certain value of the acceleration parameter, reverse flow occurs in the x-component of the velocity profile.

Development of flow and heat transfer of a viscous fluid in the stagnation-point region of a three-dimensional body with a magnetic field

The development of flow and heat transfer of a viscous electrically conducting fluid in the stagnation point region of a three-dimensional body with an applied magnetic field is studied when the external stream is set into an impulsive motion from rest and at the same time the surface temperature is suddenly raised from that of the surrounding fluid. This analysis includes both short time solution (Rayleigh-type of solution) and the steady-state solution as time tends to infinity (Falkner-Skan type of solution). The unsteady three-dimensional boundary layer equations represented by a system of parabolic partial differential equations are solved numerically using an implicit finite-difference scheme. For certain particular cases analytical solutions are obtained. In the absence of the magnetic field, the reverse flow occurs in the transverse component of the velocity in a certain portion of the saddle-point region (−1≦c<−0.4, wherec=b/a is the ratio of the velocity gradients in they- andx-directions at the edge of the boundary layer). The magnetic field delays or prevents the reverse flow. The surface shear stresses in the principal and transverse directions and the surface heat transfer increase with the magnetic field both in nodal point (0≦c≦1) and saddle point (−1≦c<0) regions. For a fixed magnetic field, the surface shear stress inx-direction and the surface heat transfer increase with time in nodal and saddle point regions, but the surface shear stress in the transverse direction increases with time for 0<c≦1 and decreases with increasing time for −1≦c<0.