Magnitude Of Normal Stress Research Articles

UJI KELAYAKAN KONSTRUKSI BALOK PT DAEYUNG DARI APLIKASI SAP2000 MENGGUNAKAN MACHINE LEARNING DENGAN MODEL LINIER REGRESSION

Structural design is one of the important elements in the construction of a building in order to produce a safe, strong and economical building. Especially in the design of upper structures (in the form of floors, beams, columns, walls and roofs). In beam structures, design and feasibility testing regarding dimensions and the use of reinforcement are safe and economical. Based on the allowable normal stress, it can be seen whether the normal stress is feasible or not if a certain input value is entered, so that information on the feasibility of this quantity can be applied directly to the building. Therefore, it is necessary to have a simulation process regarding the feasibility of stress so that the building to be created can meet the criteria for being a safe, strong and economical building. Overall the analysis process uses Machine Learning methods. By using three types of data, namely algorithm training data, validation data and testing data with a comparison percentage of training and testing data of 80%:20%. The training process produces very high accuracy. This can be seen in the R-Squared value of 0.99 while the RMSE is 1.30e-06. Meanwhile, in the data testing process, high accuracy was also obtained, for R-Squared of 1.0 and RMSE 3.87e-16. After the training and testing process has obtained very good results, we proceed to the beam feasibility testing process by entering certain input values, to produce the normal stress magnitude (Mpa) along with the confidence level of each normal stress prediction result.

Seismological Stress Drops for Confined Ruptures Are Invariant to Normal Stress

AbstractSeismic moment and rupture length can be combined to infer stress drop, a key parameter for assessing earthquakes. In natural earthquakes, stress drops are largely depth‐independent, which is surprising given the expected dependence of frictional stress on normal stresses and hence overburden. We have developed a transparent experimental fault that allows direct observation of thousands of slip events, with ruptures that are fully contained within the fault. Surprisingly, the observed stress drops are largely independent of both the magnitude of normal stress and its heterogeneity, capturing the independence seen in nature. However, we observe larger, normal stress‐dependent stress drops when the fault area is reduced, which allows slip events to frequently reach the edge of the interface. We conclude that confined ruptures have normal stress independent stress drops, and thus the depth‐independent stress drops of tectonic earthquakes may be a consequence of their confined nature.

Adhesion of a cylindrical punch with elastic properties that vary radially

The adhesion of a rigid substrate and an adhered straight cylindrical punch with a non-homogeneous elastic modulus is analyzed. The stress distributions are obtained along the interface for various elastic modulus gradients. The calculations are performed in the commercial finite element software Abaqus using a user material (UMAT) subroutine to control the dependence of Young’s modulus on the radial position. The UMAT code is shared in the paper. The results reveal that the decreasing elastic modulus toward the perimeter of the punch can be used to significantly reduce the normal stress magnitudes in the singularity domain, which leads to stronger adhesion. The increase in the adhesion strength is characterized numerically. The effect of Poisson’s ratio is also analyzed.

Using PFC2D to simulate the shear behaviour of joints in hard crystalline rock

Significant uncertainties remain regarding the assessment of the peak shear strength of rock joints. In recent years, Particle Flow Code (PFC) has been used to simulate shear tests of rock joints. Although previous studies showed PFC’s capability to simulate rock joint shear behaviour, it is uncertain how different parameters in PFC should be combined to realistically capture roughness and strength of asperities in contact of actual rock joints. Under low normal stresses, the shear behaviour of well-mated hard crystalline joints is governed by the interaction between asperities of some tenths of a millimetre. This paper investigates the capability of PFC2D to realistically simulate the peak shear strength of hard crystalline rock joints under different constant normal stress magnitudes. The simulated two-dimensional profiles were selected from the digitised joint surface obtained with optical scanning measurements. To realistically capture surface roughness and asperity strength in PFC2D, different values of joint segment length, particle resolution per segment, and bond strength between particles were studied and calibrated while taking into account the laboratory observations. The results of the numerical simulations in the PFC2D environment show that the simulated peak shear strength using the profile containing the steepest asperity is in good agreement with that measured in the laboratory. The joint profile needs to be represented by both a magnitude of segment length that captures the grain size, and at least two particles per segment. The bond strength calibration needs to account for both asperity size and the number of particles in contact during shearing.

Simple shear deformation of sheet metals: finite strain perturbation analysis and high-resolution quasi-in-situ strain measurement

Accurately evaluating the simple shear in sheet metals has proven to be challenging owing to three reasons: a) the detailed shear strain evaluation is different from one publication to another; b) the measured strain is strongly dependent on the employed virtual strain gauge size (LVSG) when digital image correlation (DIC) is utilized; and c) the negligence of the strain perturbation phenomenon (Swift effects) will only result in a rough estimation of the strain–stress behavior. Thus, in this study, a finite strain perturbation analysis according to the configuration of experimental tests was constructed to understand the shear strain–stress evolution, and a high-resolution quasi-in-situ strain measurement technology was developed to capture the localized shear strain with reliable results. Material anisotropy and simple shear specimen geometry were identified as the two major contributors to the Swift effects. Hence, a finite strain perturbed shear kinematics was first proposed, revealing that some specific shear strain estimations led to a certain degree of error (∼12–25%) at large deformation levels. This work demonstrated that the finite element simulation of simple shear tests, performed using the carefully calibrated YLD2004 yield model, can be utilized to reasonably predict perturbation. A Vickers-indentation-based quasi-in-situ strain measurement was further developed to obtain reliable local strain of the shear zone with LVSG =28 μm. The technique was found to provide high-resolution strain detection to satisfy the necessary conditions of accurate strain measurement when a narrow shear band is present. The results yielded a 30% higher von Mises strain under simple shear deformation than that reported in previous publications for a similar DP980 sheet. The said result was also found to be larger than the fracture strain determined through the so-called “hybrid method”. The proposed perturbed shear kinematics was further implemented in the anisotropic elastoplasticity framework to show that the magnitude of normal stresses did not always remain in the second order with respect to the shear stress due to strain perturbation. Thus, the concept of “perturbed” shear stress was designed to consider the effects of perturbation, and the findings signified a 6–13% change in shear stress compared with the commonly used shear stress for tested scenarios.

Fault Sealing Evaluation of a Strike-Slip Fault Based on Normal Stress: A Case Study from Eastern Junggar Basin, NW China

The sealing of a fault zone has been a focus for geological studies in the past decades. The majority of previous studies have focused on the extensional regimes, where the displacement pressure difference between fault rock and reservoir was used to evaluate the fault-sealing property from the basic principle of fault sealing. When considering the displacement pressure difference, the impact of gravity on the fault rock was considered, whereas the impact of horizontal stress was ignored. In this study, we utilize the displacement pressure difference as an index to evaluate the sealing capacity of strike-slip faults, in which both the impacts of gravity and horizontal stress on the fault rocks are all integrated. By calculating the values of σH/σV and σh/σV in the vicinity of fault planes, the coefficient K of compaction impacts on fault rocks between normal stress to fault planes and gravity was then determined. By revealing the quantitative relationship between the displacement pressure of rocks, burial depth and clay content, the displacement pressure difference between fault rocks and reservoirs were calculated. The results suggest that the sealing capacity of a strike-slip fault is not only related to the magnitude of normal stress to the fault plane, but also to the stress regime. The clay content is also an important factor controlling the sealing capacity of strike-slip faults.

Determination of the seismic signatures of landslides in soft soils: A methodology based on a field scale shear box

We present a novel field experimental setup that can be used for studying the characteristics of landslide seismicity. The setup consists of a concrete, filled with soil, cylinder that moves along a surficial soil corridor. The emitted seismic signals are due to soil friction. The cylinder acts as an upscaled sheer-box allowing control over a number of parameters: the magnitude of normal stress on the failure plane, the degree of saturation and the type of soil. This allows for the simulation of soil friction within, or between, different geological layers under different conditions. Results are site specific, but can be easily reproduced for any geological environment. We validate this methodology by comparing the spectral characteristics of the signals emitted by the movement of the cylinder to those induced by a controlled failure of a 2.5 m high vertical face at a nearby site with very similar geology. We find a very good agreement between the two. This methodology can be used as a site investigation tool for the optimization of the deployment geometry of seismic networks for landslide monitoring, as well as to inform machine learning algorithms on automatic detection and classification of recorded signals during seismic monitoring of landslides.

Forearc Basin Stratigraphy Resulting From Syntectonic Sedimentation During Accretionary Wedge Growth: Insights From Sandbox Analog Experiments

AbstractForearc basin stratigraphy is expected to record a detailed history of the deformation and growth pattern of an accretionary wedge. However, the relationship between syntectonic basin sedimentation and growth of a wedge remains poorly understood, including how deformation of the wedge modifies the basin stratigraphy and how syntectonic sedimentation influences deformation of the wedge. This study reproduced accretionary wedges with and without syntectonic sedimentation by analog sandbox experiments. The results show that basin stratigraphy varied with changes of the growth pattern of the accretionary wedge. In the case that wedge growth was dominated by frontal accretion phase, the depositional area migrated trenchward. In contrast, underthrusting phase caused the sediment layers to be tilted landward and the depocenter to migrate landward. A prolonged underthrusting can result in combining a retrowedge basin with a wedge top basin and yield a wide area of accommodation space. The occurrence of two types of basin stratigraphy (trenchward and landward migration of the depocenter) reflects the two different types of deformation (frontal accretion phase and underthrusting phase), and these differences possibly depend on a contrast in strength of the basal shear resistance between the inner and outer parts of the wedge due to temporal and spatial variations of sedimentation on the wedge. A change in the magnitude of normal stress acting on the wedge base likely influenced the mode of deformation of the wedge. These results suggest that forearc basin stratigraphy is influenced by the growth pattern of accretionary wedges, which is itself affected by syntectonic sedimentation.

Моделювання технологічного процесу двоетапної ОЗО циліндричних валів поліграфічного обладнання методом кінцевих елементів

The analysis of the stress-strain state of a two-stage process of finishing and strengthening treatment of the shaft surfaces of the conveyor-coordinating node of the line for the manufacture of integral covers with a wide valve. The process of finishing and hardening consists of two successive steps. First, a regular microrelief is formed on the cylindrical surface of the steel shaft by vibration rolling. Then a partial regular microrelief is applied to the surface with the formed microrelief by diamond smoothing. It looks like longitudinal depressions along the axis of the shaft. Stress-strain analysis was performed using CAD/CAM ANSYS engineering analysis system.In modeling of processes of finishing and strengthening processing such possibilities of system of finite elemental analysis CAD/CAM ANSYS are involved, as the solution of contact problem of plastic deformation of contact of type ‘deforming tool—part’ in plane deformation statement. The distribution of stresses and deformations in the workpiece material during loading and after unloading is obtained. A standard polynomial procedure was used to construct the shape function.A finite element model of a two-stage process of finishing and strengthening processing of shafts of the transport-coordinating node of the line for the manufacture of integral covers with a wide valve is developed. The assumptions were made: the detail, in the course of finite element analysis, is an infinite workpiece; spherical deforming tool — absolutely solid; the technological process of microrelief formation is dynamic. In this regard, in its simulation to simplify the formulation of the problem, it was solved as quasi-dynamic. That is, in the static formulation of the deformation tool, it was not the speed but the displacement that was set.The influence of the force applied to the deforming tool on the depth and magnitude of the occurrence of normal residual stress as well as the dependence of the magnitudes of normal stresses on the directions of their action is established.

Properties of Drained Shear Strength of Expansive Soil Considering Low Stresses and Its Influencing Factors

The shallow failure of most expansive soil slopes undergoing wet–dry cycles occurs during or after long-term rainfall. According to the actual failure state of an expansive soil slope, the conventional direct shear equipment with low normal stresses was used to evaluate the effects of initial dry density, initial moisture content, and number of wet-dry cycle with or without loading on drained shear strength for the compacted expansive soil from Nanning, China. The saturated drained direct shear tests were also performed on the natural expansive soil specimens from Nanning by considering the influence of wet–dry cycles with loading and low normal stresses. Furthermore, consolidated drained triaxial compression tests on compacted specimens were conducted. The test results show that the drained shear strength of expansive soil was primarily affected by the magnitude of normal stresses, and also influenced by the initial moisture content, initial dry density, and number and type of wet–dry cycles. It is more realistic to consider the effect of loading during wet–dry cycles than that without loading. The effective drained shear strength envelopes with low normal stresses were plotted and well fitted by the generalized power function. At low normal stress levels, the drained shear strength still decreased with the increasing number of wet–dry cycles, and the effective cohesion intersects tended to be zero after being subjected to eight wet–dry cycles. This provided a theoretical basis for properly interpreting the shallow failure of expansive soil slopes.

DEM Simulation of Direct Shear: 1. Rupture Under Constant Normal Stress Boundary Conditions

A particle-based distinct element method and its grain-based method are used to generate and simulate a synthetic specimen calibrated to the rupture characteristics of an intact (non-jointed) low-porosity brittle rock deformed in direct shear. The simulations are compared to the laboratory-generated ruptures and used to investigate rupture at various normal stress magnitudes. The fracturing processes leading to shear rupture zone creation and the rupture mechanism are found to be normal stress dependent (progressing from tensile splitting to shear rupture) and show partial confirmation of rupture zone creation in nature and in experiments from other materials. The normal stress dependent change is found to be due to the orientation of the major principal stress and local stress concentrations internal to the synthetic specimens being deformed. The normal stress dependent rupture creation process results in a change to the rupture zone’s geometry, shear stress versus horizontal displacement response, and thus ultimate strength.

절리면 전단거동에서의 법선응력 영향 고찰

Shear behavior of joint plane has been investigated considering the magnitude of normal stresses and initial surface roughness. Shear strength of joint plane has been measured by performing the multi-stage shear test in which applied normal stress level has been increased stepwise. Multi-stage shear test within the specified normal stress range has been repeated and two types of strength parameter variation have been observed: type 1 - both cohesion and friction angle decrease, type 2 - cohesion decrease and friction angle increase. Trends of strength parameter variation for the three rock types, gneiss, granite and shale, have been investigated and the influence of initial roughness of joint plane on the sequential shear strength change for the repeated multi-stage shear tests also has been analyzed.

Parametric and non-parametric statistical approaches to the determination of paleostress from dilatant fractures: Application to an Early Miocene dike swarm in central Japan

Several methods have been proposed for determining paleostress states from orientations of dilatant fractures such as dikes and veins. Recently a stochastic inversion method was invented to objectively estimate the principal stress axes and the stress ratio. Whether a fracture is dilated or not is controlled by the balance of the fluid pressure and the normal stress acting on it. The magnitude of normal stress depends on the fracture orientation, which causes anisotropic orientation distribution of dilatant fractures. The inversion method assumes that the orientation distribution of fractures can be approximated by a Bingham distribution, an exponential probability distribution on the unit sphere, of which symmetric axes are interpreted as the principal stress axes. However, it is unknown if the exponential type of distribution function is suitable or not. Here, we examine the distribution functions and propose two improved methods. One method uses the shifted power-law function as the shape of probability distribution, which is more flexible than the Bingham distribution and is applicable to various shapes of orientation distributions. Furthermore, an index of the driving fluid pressure can be estimated with a confidence interval. The other is a non-parametric (distribution-free) method, which can avoid the a priori assumption on the shape of distribution function without significantly losing accuracy or precision. The new methods were applied to an Early Miocene dike swarm formed during the back-arc opening of the Japan Sea. A normal-faulting stress regime with the minimum principal stress axis trending roughly perpendicular to the arc was obtained from the dikes. A moderately high stress ratio and a high fluid pressure were also estimated.

Experimental Study on Shear Mechanical Characteristics of Cohesionless Granular Material

The direct shear mechanical characteristics of gravel, sand and steel particle were studied systematically using DRS-1 high normal stress direct and residual shear apparatus. The results show that the shear mechanical characteristics of gravel, sand and steel particle is different under different normal stress condition. For steel particle, the curves of shear stress-shear displacement present strain softening regardless of the magnitude of normal stress, and the shear displacement corresponding to the peak shear stress increases with the normal stress. Under low normal stress condition, the volume of fine gravel and steel particle expand, but the fine sand contracts at the beginning of direct shear and then contracts. Under high normal stress condition, the volume of steel particle contracts at the beginning of the direct shear and then contracts, but the fine sand and fine gravel contract throughout the direct shear. The particle breakage has significant effect on the shear strength of fine sand and fine gravel. Under the same high normal stress condition, the volume of fine gravel is greater than that of fine sand, which indicates that the fine gravel is easier to be crushed than the fine sand.

A laboratory fracture shear cell used for simulation of fracture reactivation

Fault reactivation is an unfavourable incident during drilling and production that may occur due to changes in situ stresses and reservoir pressure. Only a few studies, in their analyses, have included the effects of fault geometrical properties—these are important parameters controlling fault slippage and damage around it. In this paper, the significant influence of fracture morphology on the mechanical behaviour of rock fractures was investigated through experimental studies of shearing rock fractures in the lab. The experiments carried out using a fracture shear cell (FSC): the cell that was modified by adding a number of components to an existing true triaxial stress cell (TTSC) and designing a duplex high pressure cylinder that is capable of applying large normal stresses to the sample at a constant rate. A number of artificial blocks made of mortar material were subjected to shear tests using FSC under a wide range of normal stresses and at different shearing directions. The outputs of uniaxial compressive strength and fracture shear tests in the lab were used to plot the failure envelope of the fractured rock mass and discuss the failure mechanism through shearing. Accordingly, a calibrated, numerical discrete element method (DEM) was used to simulate the shear behaviour of fractures previously tested in the lab. The results of lab tests and DEM simulations will be presented and different failure mechanisms that are expected during shearing will be explained. The results show the significant influence of surface roughness on shear strength and extent of damage zone along the fracture. It was found that the shearing response of fractures depends on the magnitude of normal stress, which indicates the importance of having a good knowledge of in-situ stresses when modelling fault reactivation and damage near the fault zones. The results of lab experiments and numerical simulations were compared and good agreements were observed.

Shear strength of geosynthetic composite systems for design of landfill liner and cover slopes

Torsional ring shear tests were performed on composite specimens that simulate the field alignment of municipal solid waste (MSW) landfill liner and cover system components. Simultaneous shearing was provided to each test specimen without forcing failure to occur through a pre-determined plane. Composite liner specimens consisted of a textured geomembrane (GM) underlain by a needle-punched geosynthetic clay liner (GCL) which in turn underlain by a compacted silty clay. Hydrated specimens were sheared at eleven different normal stress levels. Test results revealed that shear strength of the composite liner system can be controlled by different failure modes depending on the magnitude of normal stress and the comparative values of the GCL interface and internal shear strength. Failure following these modes may result in a bilinear or trilinear peak strength envelope and a corresponding stepped residual strength envelope. Composite cover specimens that comprised textured GM placed on unreinforced smooth GM-backed GCL resting on compacted sand were sheared at five different GCL hydration conditions and a normal stress that is usually imposed on MSW landfill cover geosynthetic components. Test results showed that increasing the GCL hydration moves the shearing plane from the GCL smooth GM backing/sand interface to that of the textured GM/hydrated bentonite. Effects of these interactive shear strength behaviors of composite liner and cover system components on the possibility of developing progressive failure in landfill slopes were discussed. Recommendations for designing landfill geosynthetic-lined slopes were subsequently given. Three-dimensional stability analysis of well-documented case history of failed composite system slope was presented to support the introduced results and recommendations.

The mechanics of surficial failure in soil slopes

It is not safe to employ the classical infinite slope failure analysis procedure in which the Coulomb failure criterion is used, because a very large portion of the factor of safety is assigned to the effective cohesion which is not present in the soil. Part of the problem arises from the normal stresses used in the drained direct shear tests, which are high relative to the normal stresses prevailing in surficial failures. The real effective strength envelope is curved, and it is proposed to model it by a power function whose parameter values may be determined from the usual shear tests performed at the normal stress magnitudes usually employed. Based on the factor of safety calculations from the curved failure envelope and observations from field rainfall infiltration experiments, the mechanics of surficial failure of slopes is explained.

Cyclic behaviour of a sand – steel plate interface

This paper presents the results of an experimental study on the mechanical behaviour of an interface between sand and a steel plate. A simple shear type interface apparatus is used. Tests are conducted under a two-way, displacement-controlled cyclic loading condition. The effects of the initial soil density, number of displacement cycles, magnitude of normal stress, and amplitude of tangential displacement on the cyclic response of the interface are investigated. The interface behaviour is presented in terms of the shear stress mobilized on the interface, the changes taking place in sample height, and the components of tangential displacements resulting from soil deformation and from slip between the soil and the steel plate during displacement cycles.Key words: cyclic behaviour, soil–structure interface, simple shear, slip, laboratory testing.

Thermomechanical stability of memory package with LOC structure

The present work attempts to determine an appropriate design of double-sided adhesive tape, which plays a significant role in defining the degree of chip surface damage in a plastic LOC (lead-on-chip) package. Various tape designs were tested to determine their effectiveness in preventing thermal stress-related damage on the chip surface during temperature cycling. The experimental results indicate that the thermomechanical stability of the IC pattern is more influenced by whether the LOC tape is employed along the chip edge than by the size of the tape covering area. Moreover, it was found that chip surface damage associated with LOC tape can be caused by normal stress applied to the chip surface vertically as well as by shear stress, which is known to cause damage. The importance of the normal stress component is verified through a 3-dimensional FEM (finite element method) simulation adopted to define the thermal stress distribution in the present LOC package. The numerical calculation shows that when the tape is designed to cover the chip corner, the magnitude of normal stress reveals a maximum value at the edge of the chip.

Flexural motion due to laser ablation: Influence of force location on the flexural motion

The flexural motion of a multilayer assembly subjected to laser ablation is studied. The assembly consists of thin layers of Inconel alloy (top and bottom layers) and a steel layer (intermediate layer). The assembly resembles a stainless steel sheet with both surfaces coated. The recoil pressure generated during the ablation process results in a loading pressure force acting normal to the assembly surface. The pressure force causes flexural motion in the assembly. In order to secure a sufficiently large flexural displacement, a cantilever arrangement of the assembly is considered. The recoil pressure and the resulting force are formulated and the flexural displacement as well as the resulting stress fields are computed. The influence of the pressure force location at the assembly surface on the flexural motion is examined. It is found that the time occurrence of maximum flexural displacement is the same for all the load locations and the maximum displacement occurs at the free end of the cantilever assembly. The magnitude of normal stresses and shear stress is less than the yielding limit of the substrate material. Moreover, the maximum shear stress is almost three times the maximum normal stress in the assembly.