Search

Normal stress on dikes is one of the most critical parameters for a sound dike design. With more rapidly rising sea levels due to global warming, dikes are seriously threatened by overtopping induced by the combination of wave and storm surge. Compared with wave overtopping on positive freeboard, the curling breaking wave on dikes induced by the combined wave and surge overtopping may destroy the weakly protected dike crest and landward slope. Thus, in order to prevent severe damage to dikes, it is necessary to fully understand the normal stress induced by the combined wave and surge overtopping. In this paper, physical model tests were carried out to study the normal stress on dike induced by the combined wave and surge overtopping. Two characteristics of normal stress on dike were observed. The spatial distribution of normal stress on dike was also analyzed. It was found that the Weibull distribution can be used to effectively describe the statistical distribution of peak normal stresses. Furthermore, by curve fitting of the laboratory measured data, the Weibull factors on the part of the crest and the upper part of the landward slope were obtained.

In this paper, the effect of temperature on rheological properties of magnetorheological (MR) gel is investigated under rotational steady shear and oscillatory dynamic shear. A kind of fluid-like MR gel (MRG) was firstly synthesized by mixing carbonyl iron powder (CIP) with polymer matrix. Then, the relationship between yield stress, normal stress of MRG and shear rate under six temperatures and four magnetic field strengths were studied by rotational shear experiments. The results demonstrate that the dependence of shear stress on temperature displays an opposite tendency in comparison with that of normal stress on temperature. Moreover, maximum yield stress, one of the most important parameter of MR materials, decreases with the increment of temperature. Under oscillatory dynamic shear test, storage and loss moduli and normal stress of MRG all increase with temperature when a magnetic field is applied, which presents a contrary trend in the absence of a magnetic field. Related mechanisms about the alternation of microstructures of MRG were proposed to explain the above-mentioned phenomena. This paper is helpful in fabricating semi-active engineering devices using MR materials as a medium. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the increasing scale and depth of underground engineering, the geological environment that engineering is faced with is becoming more complex. As the weak position of rock mass, the structural surface has a particularly great influence on the mechanical characteristics of the rock mass. In order to obtain the shear strength characteristic of the structural plane and analyze the influence of morphological parameters such as the undulating angle and bulge degree on shearing, taking medium-low permeability tight sandstone as the research object, four kinds of structural plane samples with different undulating angles (10, 20, 30 and 40°) were prepared with a Python and high-precision engraving machine. Direct shear tests under different normal stresses (2, 4, 6 and 8 MPa) and shear rates (0.6, 1.2 and 2.4 mm/min) were performed, and the shear mechanical properties were analyzed. The structural surfaces before and after shearing were scanned using a high-precision three-dimensional scanner, so as to evaluate the roughness of the structural surface and determine the influence from various factors on the shear characteristics. The test results showed that for the structural plane with the same undulating angle, the peak shear stress increased approximately linearly with an increase in normal stress at a 0.6 mm/min shear rate and an increment speed of approximately 0.82, while the peak shear stress negatively correlated with the shear rate at a value of 4 MPa for normal stress. The larger the undulating angle was, the greater the influence of the shear rate (the shear stress decreased by 2.31 MPa at a 40° angle). When the normal stress and the shear rate were fixed, the peak shear stress corresponding to the structural surface gradually increased with the increase in the undulating angle, and the maximum increment was 5.04 MPa at 4 MPa normal stress and a 0.6 mm/min shear rate. An analysis of the morphological characteristics of the structural plane showed that when the undulating angle (40°) and the normal stress (6 and 8 MPa) were larger, the damage of the structural plane became more obvious, the shear point was closer to the tooth valley position, and the mechanical bite force and friction force of the structural plane were better utilized. When the shear rate was lower (0.6 mm/min), the friction characteristics of the shear surface were more visible, the shear was increasingly sufficient, and the corresponding shear strength was also greater. [ABSTRACT FROM AUTHOR]

Two-component particle image velocimetry was employed to measure the influence of surface roughness on a Mach 2 boundary layer. Three surface conditions were examined: a smooth wall, patterned diamond-shaped roughness, and an approximately random realistic roughness. The response of the boundary layer was characterized in ensemble-averaged measurements of the mean velocity and Reynolds stresses. The streamwise development of the mechanical distortions introduced by the diamond-shaped roughness was also explored through observation of roughness-generated shock waves and changes in the boundary-layer profile. Measurements acquired at three streamwise locations are consistent with the trends observed in other studies when scaled by the roughness friction velocity. Ensemble-averaged outer-scaled streamwise velocity profiles showed a velocity deficit in the near-wall region. Inner-scaled boundary-layer profiles showed a downward vertical shift in the scaled velocities of 4.5 and 3 for the diamond roughness and nonuniform/realistic roughness topologies, respectively. These values show similar responses to the results seen in the literature for similar test conditions. The roughness effects were shown to increase in magnitude along the streamwise distance. [ABSTRACT FROM AUTHOR]

The purpose of the NASA Juncture Flow experiment was to acquire high-quality flowfield details deep in the corner of a wing-body junction specifically for the purpose of computational fluid dynamics (CFD) validation. A truncated DLR F6 wing was used along with a flat-sided fuselage with windows that allowed both laser Doppler velocimetry and particle image velocimetry measurements to be made very close to the corner. This paper describes the experiment and its results. It also makes comparisons between the wind-tunnel data and Reynolds-averaged Navier-Stokes CFD results using a new version of a quadratic constitutive relation that was recently developed to improve separated corner-flow predictions. This validation experiment provides useful flowfield data that can be used to test the ability of CFD methods and models to accurately represent separated juncture flow physics. [ABSTRACT FROM AUTHOR]

The cemented soil–pipe pile is an expanded pile that is composed of a high-strength, precast, prestressed pipe pile core and an expanded zone of cemented soil. To investigate the shear behaviours of the cemented soil–pipe pile interface, a series of large-scale direct shear tests on the cemented soil–concrete interface under various cemented soil strengths and different normal stresses were conducted in this research. The results revealed that the shear stress increased approximately linearly with the increase of shear displacement. When the bond limit was reached, the interface slid and the shear stress decreased sharply to the residual stress, after which it remained almost constant. The shear stress increased with the increase of the cemented soil strength and normal stress, while the peak stress was found to be relatively less affected by normal stress. The residual stress was found to be less affected by the cemented soil strength, while it increased dramatically with the increase of normal stress. Based on the test results, the shear process of the cemented soil–concrete interface can be summarised as the bond failure stage and the friction slip stage. [ABSTRACT FROM AUTHOR]

Mg/Al laminate composites were prepared at 400 ℃ for 15 min through single-pass rolling with reduction ratio from 10 to 27%. The bonding mechanism of the initial bonding stage under low pressure was studied. Two critical statuses (beginning bonding and complete bonding) are found at the reduction ratio of 14.5% and 21.75%. In this article, the coincidence of the ratio of external force (normal stress) and internal force (electronic force) at the two critical points shows that electrons overcome the potential barriers of Mg and Al respectively and make them move freely to form metal bonds. The free movement of electrons between two metal interfaces forms a metallic bond, which bonds the two metals. The formation of metallic bonds overcomes the classical barrier to achieve electron free motion. The ratio of σMg to σAl (σMg/σAl) is 0.7340, and the ratio of fMg to fAl (fMg/fAl) is 0.7988, where it can be found that the former agrees well with the latter. The good agreement between theory and experiment proves that overcoming the potential barrier plays an important role in the early bonding stage of bimetal composite plates. [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology & Engineering Geology / Shuiwendizhi Gongchengdizhi is the property of Hydrogeology & Engineering Geology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To investigate the characteristics of the acoustic emission and microseism occurring during rock shear failure, we conducted a series of direct shear tests on the cubic specimens under different normal stress conditions. First, the tested specimen shear strength, deformation characteristics, and crack during rock shear failure are investigated. Then, the waveform, fractal, and spectrum of microseism (MS) are analyzed. The deformation and stress characteristics of the tested specimen during the direct shear test are consistent with those obtained in the previous studies, indicating that the experimental results from our direct shear test are reasonable. In addition, a "quiet period" can be observed in the waveform of MS before the overall shear failure under low normal stress conditions for all the types of specimens. With the increase of normal stress, the relative length of the "quiet period" decreases, especially for the granite specimens, the "quiet period" will disappear. Otherwise, it can be obtained that before the overall fractal dimension exhibit a rapid increase. Furthermore, investigation on the frequency-amplitude distribution of MS indicates that high-amplitude MS signals occur during the rapid stress decreasing stage. Meanwhile, with the increases of the normal stress, more high-amplitude MS signals arise. The distribution of these high-amplitude MS signals changes from punctiform-shaped to bar-shaped and then clustered shape. It is concluded that the "quiet period" of MS waveform, the rapid increase of fractal dimension, and the appearance of high-amplitude MS before the overall shear failure can be taken as the precursor information to the overall shear failure. [ABSTRACT FROM AUTHOR]

Direct numerical simulations (DNS) are performed to study acoustic radiation in a quasi-two-dimensional nozzle with two independent spatially evolving turbulent boundary layers with an edge Mach number of 6. The emphasis of this work is to compare the radiated pressure fluctuations in a geometrically confined environment with those radiated from a single wall in an unconfined setting. The boundary-layer profile of the rms pressure fluctuation scaled by the mean shear stress at the wall is found to be in good agreement with prior flat-plate calculations at similar conditions. However, the normalized rms pressure fluctuation within the freestream region is significantly higher than that in the unconfined case, by a factor that is approximately equal to 2-v. The application of two different compressibility transformations to the computed mean velocity profiles indicates that, in comparison with the van Driest transformation, the Trettel and Larsson transformation provides a better collapse with flat-plate simulations over a broad range of Mach numbers. The DNS data also reveal that, in spite of displaying a strongly non-Gaussian behavior inside the boundary layer, the radiated acoustic fluctuations in all thermodynamic variables have a skewness of approximately 0.3, indicating a minor deviation with respect to Gaussian behavior. Surface pressure fluctuations along the nozzle walls are not significantly impacted by the acoustic waves radiating from the opposite wall. [ABSTRACT FROM AUTHOR]

This work delves into the study of stresses induced in a non-homogeneous pre-stressed nearly incompressible elastic substrate with irregularity as a result of a normal load moving on its rough surface. The irregularity on the free surface of the substrate is considered in the form of parabolic irregularity. The solution methodology features the applicability of perturbation method along with substitution method to obtain the displacement components. The expressions of the induced shear and normal stresses have been established in closed form, and their expressions for special cases of the considered problem have also been deduced, which concur well with the existing literature. The influences of affecting parameters viz., non-homogeneity, frictional coefficient, irregularity factor, irregularity depth, hydrostatic stress and depth of the substrate on shear and normal stresses have been depicted graphically by means of numerical computation. The computational results have been manifested for distinct cases of irregularity zone involving parabolic as well as rectangular irregularities present in the considered geometrical model. It has been figured out that the presence of non-homogeneity in the irregular substrate has significant impact on the developed stresses. • Moving load on irregular non-homogeneous elastic substrate is studied. • Perturbation method is applied for solution procedure. • Expressions of induced shear and normal stresses are established. • Deduced special cases are validated. • Impacts of affecting parameters on induced stresses are depicted. [ABSTRACT FROM AUTHOR]

Strain observation is the most intuitive observation equipment to monitor stress change in the crust. Strain equipment near the epicenter area of the Jiuzhaigou earthquake (JZGEQ) provides a lot of reliable pre-seismic and post-seismic data for the study of stress change. In this study, the load/unload response ratio (LURR) method is used to study the stress state of rocks by calculating the ratio of strain observation during the loading phase and unloading phase. Results show that the LURR method based on strain observation is an effective method to describe the dynamic change of the constitutive relationship of the rocks in the crust. Different from the strain observation, the LURR anomaly evolution process is more continuous regardless of the time series curve or spatial and temporal distribution characteristics. The LURR curves of different stations begin to increase above 1.0 gradually from 6 months to 1 year prior to the occurrence of the JZGEQ, reaching the maximum value in 1–3 months before the JZGEQ, and subsequently return to a low level. The maximum value of the LURR anomalies decreases with the distance from the epicenters. At the same time, the spatial and temporal evolution characteristics of the LURR anomalies show us the process of “extension—enhance—weaken” in the epicenter of JZGEQ and its peripheral area prior to the earthquake. The concentration areas of the aforementioned LURR anomalies are all distributed in the pre-seismic normal stress-loading zone, which indicates that the faults are in the process of decoupling, and microfracture may exist in the stage of rock dilatancy.

Formwork is an essential part of construction engineering, whether for floors or for walls. This research focused on wall formwork, which is used in residential buildings. This study primarily was concerned with reducing the cost of the formwork using optimal sections and optimum casting rates. The methodology of this research consisted of using equations to determine the lateral pressure of concrete on the formwork, to calculate the minimum spacing between the formwork components to obtain an economical and safe design, to calculate the optimum casting rate, which is 1.5 m/h , and to find the optimum lateral pressure. [ABSTRACT FROM AUTHOR]

Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Numerical simulations of the NASA Juncture Flow Experiment are carried out, employing a Reynolds-stress model. A transformation of the length-scale determining variable is suggested for improving the numerical robustness of the model. Results obtained with different unstructured flow solvers on different sets of grids show very good agreement, except for velocity and Reynolds-stress profiles in the vicinity of the predicted separation region. A recently developed length-scale correction and, particularly, prescribing transition on the fuselage and wing increase the predicted size of the separation region, where the variation is on the order of the experimental uncertainty. Detailed comparison of velocity and Reynolds-stress profiles with experimental data reveal a general deficiency of the model in predicting the peak of the streamwise normal stress and the distribution of all Reynolds stresses in the vicinity of the separation region. However, all predicted sizes of the separation region are in fair agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology & Engineering Geology / Shuiwendizhi Gongchengdizhi is the property of Hydrogeology & Engineering Geology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, the dynamic contact characteristics between a piston system and a cylinder block in a spherical pump are studied theoretically and numerically. The theoretical contact model between a piston and a cylinder is established based on its structural and operational properties, to obtain the maximum contact force quantitatively. The effects of different structural parameters and working pressures on the contact force are analyzed and discussed. The relationship between friction coefficient and rotation speed is presented. The contact pairs are modeled numerically using the finite-element method and augmented Lagrange algorithm to obtain both the tangential and normal contact characteristics. Both static and dynamic contact characteristics of the piston are analyzed and discussed. These proposed studies can provide practical suggestions on improving the wear resistance performance and durability of the spherical pump. [ABSTRACT FROM AUTHOR]

In order to study the shear failure characteristics of anchored jointed rock mass, according to the indoor test and particle flow software PFC2D, the shear behavior and internal meso-crack evolution of the anchored rock mass under different normal stresses and different anchoring angles are analyzed. The researches show that: (1) With the increasing of the anchoring angle, the shear strength of the anchored rock mass increases first and then decreases, and when the anchoring angle is 60°, the shear strength is the largest and the anchoring effect is the best. With the higher the normal stress, the higher the shear strength of the anchored jointed rock mass, the better the shear resistance. (2) As the shear displacement increasing, a small number of cracks generated in the early stage near the anchor and joints, through continuous outward expansion, eventually gather a large number of cracks at the joint between the anchor and the joint, where in the crack, the tensile crack is dominant. (3) The anchoring angle and normal stress have a significant influence on crack propagation. With the increasing of normal stress, the number of cracks also shows an increasing trend, and the rock mass damage is more serious. With the change of the anchoring angle, the number of cracks formed when the anchored rock mass is destroyed firstly decreases and then increases, and when the anchoring angle is 60°, the cracks are the least.

The cyclic simple-shear behavior of soil-structure interfaces under different normal stresses is of great significance in theoretical analysis and engineering practices. A series of interface tests between gravel and steel was conducted under different normal stresses using a 3D large-scale simple-shear apparatus, and the influence of normal stress on the cyclic simple-shear behavior of the interface was explored in detail. The normal stress plays a crucial role in the magnitudes of the shear behavior of the interface, including deforming and sliding displacements, shear stress, reversible and irreversible normal displacement, and cyclic shear strength, while it has slight influence on the relationship pattern of shear behavior. Increased normal stress leads to increased deforming displacement at the first few shear cycles, accelerated reduction and decreased stabilized amplitude of deforming displacement. Enhanced normal stress also results in increased shear modulus, decreased shear modulus coefficient at the first a few shear cycles, increased stabilized shear stress and cyclic shear strength of the interface. In addition, larger normal stress results in larger irreversible normal displacement, smaller peak reversible normal displacement, smaller transition tangential displacement and transition stress ratio of the interface. The cyclic shear strength behaves well in accordance with Mohr-Coulomb criteria, regardless of normal stress. Perfect consistency exists in the stress ratio versus tangential displacement response and irreversible normal displacement versus shear work density response, independent of normal stress, and can be described using hyperbolic models. These consistency characteristics will significantly simplify the constitutive modelling of soil-structure interfaces.

Resonators based on micro and nanoelectromechanical systems (MEMS/NEMS) are used in many applications, including biological and gas sensors, magnetic field sensors, RF switches, accelerometers, piezoelectric micro and nanogenerators, and viscosity sensors. The design of these resonators requires analytical models to predict their mechanical behavior and optimize the sensitivity and resolution. However, most of these models are only applied to resonators with rectangular and uniform cross-sections. In this paper, we present the analytical modeling to determine the first bending resonant frequency, out-of-plane deflections, and normal stresses of MEMS/NEMS-based multilayered resonators with variable cross-sections and multiple fixed supports. The proposed modeling is derived using the well-known Rayleigh and Macaulay methods, as well as the Euler-Bernoulli beam theory. This analytical modeling is applied to four multilayered resonators with different clamped supports and non-uniform cross-sections. The results of our analytical modeling agree well with respect to those of finite element method (FEM) models and experimental data reported in the literature. The proposed analytical modeling can be used to estimate the frequency shift of resonators due to variations of their geometric parameters, number of clamped-supports or mechanical properties of the materials. Furthermore, this modeling can be used to obtain optimal designs of resonators that ensure safe operations and enhanced performance for sensors and energy harvesters in telecommunications, automotive sector, aerospace industry, consumer electronics, non-destructive testing, and navigation.

The hydraulic and mechanical coupling characteristics of fracture networks under normal stress and shear stress were studied in this paper. The hydraulic and mechanical coupling model of the fracture network comprehensively considers the normal stress, shear stress, seepage pressure and roughness characteristics. Based on the boundary conditions and reasonable assumptions, COMSOL Multiphysics software was used to develop the hydraulic and mechanical coupling finite element model of the fracture network with different intersection points under normal stress and shear stress, focusing on the study of the effect of normal stress and shear stress on the fracture permeability. The degree of permeability change caused by the normal stress and shear stress is different. The shear stress has a significant influence on the fracture permeability, and when the normal stress is low, the relationship between the fracture permeability and shear stress can be described by a linear relationship. Then, the influence of the number of intersection points in the fracture network on the average fracture width, average water pressure, average seepage velocity and seepage passage of the fractured rock mass was analyzed. The number of intersections in the fracture network has little influence on the average fracture gap width and average water pressure but has a great influence on the flow velocity. The analysis in this paper is very helpful to understand the seepage characteristics in rough fractures under normal stress and shear stress. [ABSTRACT FROM AUTHOR]

Forming limit diagram (FLD) is a useful tool for predicting failure in sheet metal forming processes. Many experimental tests, such as Nakazima test, have been developed to determine the FLDs experimentally. In all these methods the FLDs are determined without considering the effect of normal stress. This paper presents a novel experimental approach based on the Nakazima method to determine the forming limit diagrams under various normal pressures. Both necking and fracture forming limit curves of St12 low carbon steel were obtained experimentally with no, and under 50 MPa compressive normal pressures. The fracture forming limit curves under different normal pressures between 0 and 250 MPa were predicted numerically using ABAQUS/Explicit commercial finite element code and applying VUSDFLD subroutine in order to determine fracture. For this purpose, six phenomenological ductile failure criteria, including Rice-Tracey, Oyane-Sato, Ko-Huh, DF2012, DF2014, and DF2015, were implemented. These criteria were calibrated using the six tests of in-plane shear, uniaxial tensile, circle hole, notched tension, plane stress, and Nakazima stretching. The results from the proposed methods and those from numerical simulations have been compared and the efficiency of each ductile fracture criterion was demonstrated. All the experimental and numerical results indicated that a greater normal stress causes the forming limit curve surface to rise. [ABSTRACT FROM AUTHOR]

We investigate the drying process of monodisperse colloidal film over a wide range of Péclet numbers (Pe) by using the Brownian dynamics simulation. We analyze the detailed process in three aspects; accumulation front, normal stress, and microstructure. The evolution of particle distribution is quantified by tracking the accumulation front. The accumulated particles contribute to the continuous increase of the normal stress at the interface. At the substrate, the normal stress first stays constant and then increases as the accumulation front touches the substrate. We quantitatively analyze the stress development by a scaled normal stress difference between the two boundaries. At all tested Pe, the stress difference increases to the maximum, followed by a decrease during drying. Interestingly, a mismatch is observed between the stress difference maximum and the initial stress increase at the substrate. The microstructural analysis reveals that this mismatch is related to the microstructural development at the substrate. [ABSTRACT FROM AUTHOR]

The impact of normal stress-induced closure on fluid flow and solute transport in a single rock fracture is demonstrated in this study. The fracture is created from a measured surface of a granite rock sample. The Bandis model is used to calculate the fracture closure due to normal stress, and the fluid flow is simulated by solving the Reynold equation. The Lagrangian particle tracking method is applied to modeling the advective transport in the fracture. The results show that the normal stress significantly affects fluid flow and solute transport in rock fractures. It causes fracture closure and creates asperity contact areas, which significantly reduces the effective hydraulic aperture and enhances flow channeling. Consequently, the reduced aperture and enhanced channeling affect travel time distributions. In particular, the enhanced channeling results in enhanced first arriving and tailing behaviors for solute transport. The fracture normal stiffness correlates linearly with the 5th and 95th percentiles of the normalized travel time. The finding from this study may help to better understand the stress-dependent solute transport processes in natural rock fractures.

The normal stress along the shear plane has great effect on the composite intralaminar shear strength. However, the influence mechanism on composite interlaminar shear strength under the normal stress along the shear plane was not truly reflected by the double-notch shear experiment. In this paper, the interlaminar shear strength of composite specimens under different external normal stresses was first obtained using the improved double-notch shear experiment. Furthermore, to research the influence mechanism on interlaminar shear strength under normal stress along the shear plane, the characteristic curve method based on the double-notch shear specimen was studied. Finally, the experimental results analyzed by the characteristic curve method were compared with a range of failure criteria presented in the literature. The experimental data obtained in this study agreed best with the NU theory criterion, with a maximum numerical difference of 4%. And the NU theory criterion can reflect the influence mechanism of the composite interlaminar shear strength best.

Abstract The transportation and capture of particulate suspension in a rough fracture are widely encountered in hydrocarbon exploitation. According to a full review of the literature, traditional studies mainly focus on the placement and settlement of coarse particles such as proppants and lost circulation materials. Furthermore, a fracture is often considered to be equivalent to smooth parallel plates, whereas actual fractures are roughly walled with microconvex and are affected by normal stresses. The particulate suspension transport mechanism in a fracture under different normal stresses is still unclear. This paper proposes an approach to evaluate the permeability impairment caused by size‐exclusion of solid particles in a fracture under different normal stresses. The morphology of fracture flow space under different normal stresses is obtained by using optical scanning and FEM. Furthermore, the unresolved CFD‐DEM method is used to study the mechanism of the capture and migration of the particulate suspension in a fracture. The simulation results are in agreement with the experimental results. Furthermore, the effects of the particle size, particle concentration, injected particle volume, fracture occurrence, and applied pressure on particle invasion are discussed.

The single adhesive joint has many applications in the shipbuilding industry, where it offers the advantage of joining materials (adherents) with different properties and characteristics using an adhesive. However, one disadvantage of this type of joint is the stress concentration at the ends of the joint, which directly affect the adhesive. Another disadvantage is the possible difference between the coefficients of thermal expansion of the adherents of the joint. Through compilation and classification of the formulas found in various publications, this study presents a state-of-the-art review of an adhesive single-lap joint that can be used in marine applications. It will consider the types of materials used as the adhesive and as the adherents, the possibility of varying the thicknesses of the adherents and the thickness of the adhesive, and the recommended design factors for each proposed methodology. This study proposes formulas to estimate the stresses for joints with balanced thicknesses and extrapolates the results for non-balanced joints; also, an equation is derived to calculate the minimum overlap joint length for ship lengthening, allowing the design process to be simplified. The results are expected to facilitate the design of single-lap joints in marine applications, such as reinforcing composite panels and lengthening of hulls and superstructures.

The results of experimental studies on the mechanical properties of cohesive soils associated with the use in the study of the erosion process are presented. The influence of the cohesion strength of cohesive soil on erosion is described. The relationship between the erosionflow velocities and cohesion strength has been obtained.

Copyright of Advanced Engineering Science / Gongcheng Kexue Yu Jishu is the property of Advanced Engineering Science Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We use 3D dynamic rupture simulations to discover a previously un‐described effect of asymmetric topography on the earthquake process. With the Cajon Pass along the San Andreas Fault as an example, we find that asymmetric topography generates an alternating normal stress perturbation around the rupture front, near the free surface. When topography lies to the right of the propagating right‐lateral front, the normal stress perturbation is clamping ahead of the rupture front and unclamping behind. When topography alternates to the left, the perturbation reverses sign. The process is analogous to the normal stress variations on dip‐slip faults. While this effect does not strongly affect rupture propagation and slip in our current parametrization, it requires explanation and exploration. An understanding of the normal stress perturbation due to asymmetric topography will help prevent its misattribution to other sources and lead to a better understanding of the interplay of multiple processes during earthquakes. Plain Language Summary: The San Gabriel and San Bernardino mountains dominate the landscape of southern California, as they both reach high elevations (+3,000 m) and extend laterally for nearly 150 km. Together they form an elongated topographic feature that separates the densely populated Los Angeles metropolitan area from the Mojave Desert. In addition to dominating the landscape, the mountains are also placed asymmetrically with respect to the southern San Andreas Fault (SAF). More specifically, south of the Cajon Pass (CP) the topography lies to the north of the SAF, while north of the CP the topography switches sides and lies to the south of the SAF. This work investigates how the asymmetric configuration of the mountains interacts with earthquake rupture along the SAF. We find that the asymmetric topography produces a pattern of clamping and unclamping of the fault near the ground surface, and this pattern moves along with the propagation of the rupture. In addition, the pattern of clamping and unclamping reverses its sign when the rupture passes through the CP. Our results contribute toward a better understanding of earthquake rupture near the earth's surface in SoCAL and worldwide. Key Points: Asymmetric topography on either side of vertical strike‐slip faults induces shallow dynamic normal stress changes near the rupture frontThe topographically induced normal stress perturbation exhibits a pattern of clamping and unclamping ahead and behind the rupture frontThe sign of the normal stress pattern is reversed when the topography switches sides [ABSTRACT FROM AUTHOR]

The deformational behavior of jointed rock masses is greatly influenced by the geometrical and mechanical characteristics of joints. Shear (ks) and normal (kn) stiffness of joints not only are vital input factors in the dis-continuum numerical analysis but also use to calculate elastic constants of an equivalent continuous material in the finite element numerical modeling. In this study, based on eighty-nine laboratory direct shear tests under constant normal loading (CNL) conditions, the dependency of ks and kn on normal stress (σn) is evaluated by the regression models. All natural and saw-cut discontinuity specimens belong to the meta-sandstone and limestone rock types. The range of the normal stress and ratio of normal stress to joint compressive strength was from 0.34 to 7.5 MPa and 0.01 to 0.24, respectively. The data analysis led to the inevitable outcome; the ks and kn versus σn increased by the power-law and exponential-law relationship, respectively. The shear stiffness not only in a natural joint, in which joint roughness coefficient (JRC) has a direct effect on the stiffness but also in a saw-cut specimens shows a power-law relationship with normal stress. Besides, the normal to shear stiffness ratio ( k n k s ) against the σn exhibit a non-linear trend line; the meta-sandstone bedding and joint show the power and the exponential trend line, respectively; the stiffness ratio ( k n k s ) at lower normal stress (0.5 MPa) were from 1.5 to 5.6, but by increasing the σn up to 7.5 MPa the stiffness ratio raised to 14.4. Considering the effect of normal stress on joint stiffness while choosing the reliable input factors for numerical analysis can avoid conservative analysis. [ABSTRACT FROM AUTHOR]

The hydromechanical properties of single self-propping fractures under stress are of fundamental interest for fractured-rock hydrology and a large number of geotechnical applications. This experimental study investigates fracture closure and hydraulic aperture changes of displaced tensile fractures, aligned tensile fractures, and saw-cut fractures for two types of sandstone (i.e., Flechtinger and Fontainebleau) with contrasting mechanical properties, cycling confining pressure between 5 and 30 MPa. Emphasis is placed on how surface roughness, fracture wall offset, and the mechanical properties of the contact asperities affect the self-propping potential of these fractures under normal stress. A relative fracture wall displacement can significantly increase fracture aperture and hydraulic conductivity, but the degree of increase strongly depends on the fracture surface roughness. For smooth fractures, surface roughness remains scale-independent as long as the fracture area is larger than a roll-off wavelength and thus any further displacement does not affect fracture aperture. For rough tensile fractures, these are self-affine over a larger scale so that an incremental fracture wall offset likely leads to an increase in fracture aperture. X-ray microtomography of the fractures indicates that the contact area ratio of the tensile fractures after the confining pressure cycle inversely correlates with the fracture wall offset yielding values in the range of about 3–25%, depending, first, on the respective surface roughness and, second, on the strength of the asperities in contact. Moreover, the contact asperities mainly occur isolated and tend to be preferentially oriented in the direction perpendicular to the fracture wall displacement which, in turn, may induce flow anisotropy. This, overall, implies that relatively harder sedimentary rocks have a higher self-propping potential for sustainable fluid flow through fractures in comparison to relatively soft rocks when specific conditions regarding surface roughness and fracture wall offset are met. [ABSTRACT FROM AUTHOR]

We report the design of a microcapillary rheometer (μCR) that allows to perform experiments rapidly and in a broad range of shear rates (i.e., from 0.1 to 1000 s−1), using small amounts of material (i.e., just few milligrams). Additionally, multiple measurement parallelization makes it suitable for High-Throughput Rheological Experimentation of polymer melts (HT-Rheo-E).The novel rheometer consists of a set of three cylindrical microcapillaries in which the fluid flows driven by a controlled pressure. A camera, placed at the capillary exit, records the fluid motion to measure its flow rate, from which the fluid viscosity can be determined. The optimization of the setup allowed for reliable and fast viscosity measurements using ca. 10 mg of material. The current work reports the design of the rheometer and validation measurements on several model fluids. The microfabricated μCR is of potential interest for applications in quality control and research where rapid and repeated measurements using limited milligrams of polymer are required, as well as for High-Throughput-Experimentation of complex fluids (e.g., biological systems).

In this paper, the effect of temperature on rheological properties of magnetorheological (MR) gel is investigated under rotational steady shear and oscillatory dynamic shear. A kind of fluid-like MR gel (MRG) was firstly synthesized by mixing carbonyl iron powder (CIP) with polymer matrix. Then, the relationship between yield stress, normal stress of MRG and shear rate under six temperatures and four magnetic field strengths were studied by rotational shear experiments. The results demonstrate that the dependence of shear stress on temperature displays an opposite tendency in comparison with that of normal stress on temperature. Moreover, maximum yield stress, one of the most important parameter of MR materials, decreases with the increment of temperature. Under oscillatory dynamic shear test, storage and loss moduli and normal stress of MRG all increase with temperature when a magnetic field is applied, which presents a contrary trend in the absence of a magnetic field. Related mechanisms about the alternation of microstructures of MRG were proposed to explain the above-mentioned phenomena. This paper is helpful in fabricating semi-active engineering devices using MR materials as a medium.

With the increasing scale and depth of underground engineering, the geological environment that engineering is faced with is becoming more complex. As the weak position of rock mass, the structural surface has a particularly great influence on the mechanical characteristics of the rock mass. In order to obtain the shear strength characteristic of the structural plane and analyze the influence of morphological parameters such as the undulating angle and bulge degree on shearing, taking medium-low permeability tight sandstone as the research object, four kinds of structural plane samples with different undulating angles (10, 20, 30 and 40°) were prepared with a Python and high-precision engraving machine. Direct shear tests under different normal stresses (2, 4, 6 and 8 MPa) and shear rates (0.6, 1.2 and 2.4 mm/min) were performed, and the shear mechanical properties were analyzed. The structural surfaces before and after shearing were scanned using a high-precision three-dimensional scanner, so as to evaluate the roughness of the structural surface and determine the influence from various factors on the shear characteristics. The test results showed that for the structural plane with the same undulating angle, the peak shear stress increased approximately linearly with an increase in normal stress at a 0.6 mm/min shear rate and an increment speed of approximately 0.82, while the peak shear stress negatively correlated with the shear rate at a value of 4 MPa for normal stress. The larger the undulating angle was, the greater the influence of the shear rate (the shear stress decreased by 2.31 MPa at a 40° angle). When the normal stress and the shear rate were fixed, the peak shear stress corresponding to the structural surface gradually increased with the increase in the undulating angle, and the maximum increment was 5.04 MPa at 4 MPa normal stress and a 0.6 mm/min shear rate. An analysis of the morphological characteristics of the structural plane showed that when the undulating angle (40°) and the normal stress (6 and 8 MPa) were larger, the damage of the structural plane became more obvious, the shear point was closer to the tooth valley position, and the mechanical bite force and friction force of the structural plane were better utilized. When the shear rate was lower (0.6 mm/min), the friction characteristics of the shear surface were more visible, the shear was increasingly sufficient, and the corresponding shear strength was also greater.

This paper proposes an empirical equation to evaluate the shear strength of rock mass with nonpersistent joints. A novel specimen preparation method is proposed and is used to created plaster specimens containing nonpersistent joints. Utilizing the proposed method, it is possible to create specimens with nonpersistent closed joints with different roughness levels along different directions. The normal stress applied to embedded nonpersistent joints is the key factor for estimating the joint friction contribution to the shear strength of rock mass with the joints. An analytical equation and an experimental approach are proposed to calculate the normal stress applied to the nonpersistent joints. Seemingly good agreement was found between the normal stress values obtained using the analytical equation and those measured by the experimental approach. To study the effects of four influential parameters, namely rock bridge ratio, material strength, joint roughness, and normal stress, on the shear strength of specimens with a single nonpersistent joint, an experimental layout was designed based on the Taguchi method. The results of the extensive experimental work were then expressed in terms of an empirical equation to calculate the shear strength of specimens embedding a single nonpersistent joint. [ABSTRACT FROM AUTHOR]

Sandwich-structured composites are extensively used in aerospace, transportation, marine, and automotive applications where mechanical performance and weight-saving features are extremely critical. Consequently, analyzing the mechanical properties including the elastic behavior of the sandwich structure is incumbent for the precise application of such composites. This paper deals with the stress analysis of a two-dimensional (2-D) rectangular sandwich-structured composite with the help of a robust numerical model. A finite difference (FD) scheme based on the displacement potential function is developed to investigate the stress-strain behavior of the sandwich structure under different loading conditions. The 2-D mixed-boundary-value elastic problem is solved by implementing special FD formulations inside the domain and at the boundaries. The mathematical intricacy of the interfaces of the sandwich structure is handled by employing modified FD formula structures. Results obtained from the FD model show that the two interfacial regions constitute the critical stress zones, and the material having a higher modulus of elasticity experiences higher stress. The proposed FD model is validated by comparing the FD results for stress distribution and displacement fields with the results obtained from a commercial finite element (FE) package. The comparison between the FE and FD results shows a good agreement which constructively establishes the proposed FD scheme as an accurate and reliable technique for conducting the structural analysis. [ABSTRACT FROM AUTHOR]

The basic principle of the three-dimensional stress state test is deduced based on the relationship between the normal stress and the conventional stress state, and the relationship between the total stress state and the effective stress state is given based on Terzaghi's effective stress principle. On this basis, we made a three-dimensional earth pressure device by using a pedestal obtained by 3D printing technology, 6 micro earth pressure cells, a pore pressure cell and an attitude sensor. Considering the effect on the tested values of the dynamic change in the normal stress direction, the conversion relationship between the absolute test direction and the relative test direction of the test device is deduced, which can be used to dynamically test the three-dimensional total stress state and three-dimensional effective stress state. In addition, a method to calculate the K0 value is proposed based on the earth pressure device comparing with the direct test result by the K0 oedometer and indirect test results by direct shear test and triaxial test in laboratory. Two three-dimensional earth pressure devices are used in a simulation experiment of tailings dam construction, and the results show that with the increase in pore pressure, the calculated errors of the three-dimensional stress state caused by rotation angles will be more noticeable. This study has engineering value for in situ geotechnical testing and soil strength prediction. [ABSTRACT FROM AUTHOR]

We examine the reflection and transmission phenomena of quasi-longitudinal plane (QP) waves in an AlN-ZnO laminated composite structure. The structure is designed under the influence of the initial stresses in which one carrier piezoelectric semiconductor (PSC) half-space is in welded contact with another PSC half-space. The secular equations in the transversely isotropic PSC material are derived from the general dynamic equation, taking the initial stresses into consideration. It is shown that the incident quasi-longitudinal wave (QP-mode) at the interface generates four types of reflected and transmitted waves, namely, QP wave, quasi-transverse (QSV) wave, electric-acoustic (EA) wave, and carrier plane (CP) wave. The algebraic equations are obtained by imposing the boundary conditions on the common interface of the laminated structure. Reflection and transmission coefficients of waves are obtained by implementing Cramer's rule. Profound impacts of the initial stresses and exterior electric biasing field on the reflection and transmission coefficients of waves are investigated and presented graphically. [ABSTRACT FROM AUTHOR]

The connection point between the wall stem and the foundation is often considered as a rigid point. However, this connection may not be fully rigid. This paper evaluates the effect of variation in the rotational stiffness (Sr) and wall height on the behaviour of a retaining wall using finite-element method (FEM). The results of the numerical analysis are presented in the form of displacements, normal and shear stresses as well as the factor of safety considering the rigid and rotational retaining walls. In the case of rotational wall, the plastic points are concentrated in proximity to the connection point between the wall stem and the foundation. However, this concentration fades as the value of Sr increases. Moreover, the factor of safety of retaining wall decreases as the value of wall height increases. [ABSTRACT FROM AUTHOR]

Abstract Femoroacetabular impingement (FAI), together with its two main pathomechanisms, cam and pincer, has become a trending topic since the end of the 1990s. Despite massive academic research, this hip disorder still conceals obscure aspects and unanswered questions that only a question-driven approach may settle. The pathway that leads a FAI asymptomatic morphology through a FAI syndrome to a FAI-related osteoarthritis is little known. Contact mechanics provides a shareable and persuasive perspective: cam FAI is based on shear contact stress at joint level with consequent cartilage wear; pincer FAI, contrariwise, determines normal contact stress between acetabular rim and femoral neck and squeezes the labrum in between, with no cartilage wear for many years from the onset. Pincer prognosis is then far better than cam. As a matter of fact, cartilage wear releases fragments of extracellular matrix which in turn trigger joint inflammation, with consequently worsening lubrication and further enhanced wear. Inflammation pathobiology feeds pathotribology through a vicious loop, finally leading to hip osteoarthritis. The association of cam and pincer, possibly overdiagnosed, is a synergic combination that may damage the joint rapidly and severely. The expectations after FAI surgical correction depend strictly on chondral layer imaging, on time elapsed from the onset of symptoms and on clinic-functional preoperative level. However, preemptive surgical correction is not recommended yet in asymptomatic FAI morphology. Level of evidence V.