Resilient behavior of coarse granular materials in three-dimensional stress state

2020 ◽  
Vol 57 (9) ◽  
pp. 1280-1293 ◽  
Author(s):  
Chuan Gu ◽  
Xingchi Ye ◽  
Jun Wang ◽  
Yuanqiang Cai ◽  
Zhigang Cao ◽  
...  
Keyword(s):  
Stress State ◽  
Granular Materials ◽  
Resilient Modulus ◽  
Three Dimensional ◽  
Principal Stresses ◽  
Axisymmetric Stress State ◽  
Promotion Effect ◽  
Fines Content ◽  
Cyclic Shear ◽  
Resilient Behavior

The traffic-induced cyclic stresses on the road base and subbase courses are usually in three-dimensional stress state, while so far most laboratory studies have focused on the deformation behavior of base and subbase layers in axisymmetric stress state. This study investigates the three-dimensional resilient behavior of coarse granular base and subbase materials based on a true triaxial apparatus. The factors of effective confining pressure, [Formula: see text], amplitude of cyclic shear stress, qampl, coefficient of cyclic intermediate principal stress, bcyc, and fines content are involved. Test results indicate that the increase of either [Formula: see text] or qampl leads to a nonlinear growth of resilient modulus with a decreasing growth rate. bcyc, which is proposed to represent the coupling of cyclic major and intermediate principal stresses, is found to have a promotion effect on the resilient stiffness, and the promotion effect tends to be enhanced by the increase of qampl. A modified model is established to predict the resilient modulus of coarse granular materials in three-dimensional stress state. There appears to exist a critical value of fines content, at which the variation trend of resilient modulus is changed from increasing to decreasing, and the critical fines content is related to both [Formula: see text] and bcyc.

Resilient behavior of coarse granular materials in three dimensional anisotropic stress state

2020 ◽  
Vol 279 ◽  
pp. 105848
Author(s):  
Chuan Gu ◽  
Xingchi Ye ◽  
Zhigang Cao ◽  
Yuanqiang Cai ◽  
Jun Wang ◽  
...  
Keyword(s):  
Stress State ◽  
Granular Materials ◽  
Three Dimensional ◽  
Anisotropic Stress ◽  
Resilient Behavior

Anisotropic Behavior of Geomaterial under Three-Dimensional Stress States

2010 ◽  
Vol 160-162 ◽  
pp. 1425-1431
Author(s):  
Kun Yong Zhang ◽  
Yan Gang Zhang ◽  
Chi Wang
Keyword(s):  
Stress State ◽  
Principal Stress ◽  
Three Dimensional ◽  
Complex Stress State ◽  
Triaxial Tests ◽  
Induced Anisotropy ◽  
Principal Stresses ◽  
True Triaxial ◽  
Stress Effects ◽  
Stress Induced Anisotropy

Most soil constitutive models were developed based on the traditional triaxial tests with isotropic assumption, in which the load is applied as the major principal stress direction and the other two principal stresses are symmetric. When such isotropic models are applied to practical analysis, stress induced anisotropy under complex stress state and the middle principal stress effects are often neglected, thus there are many disagreements between the calculated results and the infield testing data. To simulate the practical loading process, true triaxial tests were carried out on geomaterial under three-dimensional stress state. It was found that the stress induced anisotropy effects are remarkable and the middle principal stress effects are obvious because of the initial three-dimensional stress state. Such kind of stress-induced anisotropy could have important impact on the numerical analysis results and should be taken into consideration when developing the constitutive model.

scholarly journals Evaluation of additional confinement for three-dimensional geoinclusions under general stress state

2020 ◽  
Vol 57 (3) ◽  
pp. 453-461 ◽  
Author(s):  
Piyush Punetha ◽  
Sanjay Nimbalkar ◽  
Hadi Khabbaz
Keyword(s):  
Stress State ◽  
Plane Strain ◽  
Principal Stress ◽  
Three Dimensional ◽  
Axisymmetric Stress State ◽  
Proposed Model ◽  
Strength And Stiffness ◽  
Semi Empirical ◽  
Minor Principal Stress

Three-dimensional cellular geoinclusions (e.g., geocells, scrap tires) offer all-around confinement to the granular infill materials, thus improving their strength and stiffness. The accurate evaluation of extra confinement offered by these geoinclusions is essential for predicting their performance in the field. The existing models to evaluate the additional confinement are based on either a plane-strain or axisymmetric stress state. However, these geoinclusions are more likely to be subjected to the three-dimensional stresses in actual practice. This note proposes a semi-empirical model to evaluate the additional confinement provided by cellular geoinclusions under the three-dimensional stress state. The proposed model is successfully validated against the experimental data. A parametric study is conducted to investigate the influence of input parameters on additional confinement. Results reveal that the simplification of the three-dimensional stress state into axisymmetric or plane-strain condition has resulted in inaccurate and unreliable results. The extra confinement offered by the geoinclusion shows substantial variation along the intermediate and minor principal stress directions depending on the intermediate principal stress, infill soil, and geoinclusion properties. The magnitude of additional confinement increases with an increase in the geoinclusion modulus. The findings are crucial for accurate assessment of the in situ performance of three-dimensional cellular geoinclusions.

scholarly journals Deformation characteristics of saturated clay in three-dimensional cyclic stress state

2019 ◽  
Vol 56 (12) ◽  
pp. 1789-1802 ◽  
Author(s):  
Chuan Gu ◽  
Yongzheng Wang ◽  
Yuanqiang Cai ◽  
Jun Wang
Keyword(s):  
Stress State ◽  
Three Dimensional ◽  
Cyclic Stress ◽  
Principal Strain ◽  
Principal Stresses ◽  
Cycle Number ◽  
True Triaxial ◽  
Triaxial Apparatus ◽  
Wide Range ◽  
Stress Ratios

The dynamic stress field induced by moving loads is three dimensional, involving the cyclic variation of major, intermediate, and minor principal stresses, while so far very limited laboratory studies have been undertaken on the one-way deformation behavior of saturated clays in three-dimensional stress state. In this study, an advanced true triaxial apparatus, which can apply cyclic major and intermediate principal stresses simultaneously, is employed to carry out a total of 65 one-way cyclic tests on both normally and overconsolidated clays. Four values of overconsolidation ratio (OCR), five values of bcyc, which is termed the coefficient of cyclic intermediate principal stress, and a wide range of cyclic stress ratios (CSR) are tested. Emphasis is put on the effects of bcyc and OCR on the characteristics of permanent major and intermediate principal strains. Test results show that the increase of bcyc significantly reduces the accumulation of major principal strain, and linear relationships are observed between the permanent major principal strain and bcyc for test data with the same CSR, OCR, and cycle number. A critical value of bcyc ≈ 0.5, at which the permanent intermediate principal strain changes from tension to compression, is observed for the remolded clay. Furthermore, an empirical model is proposed, allowing the long-term deformation of saturated clays to be predicted in three-dimensional cyclic stress state.

Comparison of Conventional and Pontic Fixed Partial Dentures Over Implants Using the Finite Element Method: Three-Dimensional Analysis of Cortical and Medullary Bone Stress

2020 ◽  
Vol 46 (3) ◽  
pp. 175-181
Author(s):  
Marcelo Bighetti Toniollo ◽  
Mikaelly dos Santos Sá ◽  
Fernanda Pereira Silva ◽  
Giselle Rodrigues Reis ◽  
Ana Paula Macedo ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Three Dimensional ◽  
The Finite Element Method ◽  
Medullary Bone ◽  
Principal Stresses ◽  
Bone Stress ◽  
Bone Damage ◽  
Rehabilitation System ◽  
Minimum Requirements

Rehabilitation with implant prostheses in posterior areas requires the maximum number of possible implants due to the greater masticatory load of the region. However, the necessary minimum requirements are not always present in full. This project analyzed the minimum principal stresses (TMiP, representative of the compressive stress) to the friable structures, specifically the vestibular face of the cortical bone and the vestibular and internal/lingual face of the medullary bone. The experimental groups were as follows: the regular splinted group (GR), with a conventional infrastructure on 3 regular-length Morse taper implants (4 × 11 mm); and the regular pontic group (GP), with a pontic infrastructure on 2 regular-length Morse taper implants (4 × 11 mm). The results showed that the TMiP of the cortical and medullary bones were greater for the GP in regions surrounding the implants (especially in the cervical and apical areas of the same region) but they did not reach bone damage levels, at least under the loads applied in this study. It was concluded that greater stress observed in the GP demonstrates greater fragility with this modality of rehabilitation; this should draw the professional's attention to possible biomechanical implications. Whenever possible, professionals should give preference to use of a greater number of implants in the rehabilitation system, with a focus on preserving the supporting tissue with the generation of less intense stresses.

The Measurement of Stresses in Composites

1986 ◽  
Vol 1 (2) ◽  
pp. 15-21 ◽  
Author(s):  
J. B. Cohen
Keyword(s):  
Three Dimensional ◽  
Stress System ◽  
Principal Stresses ◽  
Reasonable Time ◽  
Complete Measurement ◽  
Useful Life ◽  
Diffraction Peaks ◽  
The Difference ◽  
Full Investigation ◽  
Hydrostatic Component

AbstractAlthough there is mounting interest in the measurement of stresses in composite materials after fabrication and/or use, few measurements to date have not taken into account the three dimensional nature of the stress system in such materials. Most data give only the net stress, that is, the difference between principal stresses. A procedure for a more complete measurement (in a reasonable time) is developed here, including the separation of macrostresses and microstresses. If time does not permit a full investigation, measurements of the lattice parameters of the component phases provide a simple way to sample the hydrostatic component due to differential thermal contraction. The Barrett-Predecki method of adding filler is particularly promising for stress measurements in those composites whose component phases do not give appropriate diffraction peaks. This procedure could also be used for monitoring stresses during the useful life of such materials.

scholarly journals Effects of Spatially Varying Seismic Ground Motions and Incident Angles on Behavior of Long Tunnels

2018 ◽  
Vol 2018 ◽  
pp. 1-6 ◽  
Author(s):  
Yundong Zhou ◽  
Yongxin Wu ◽  
Ziheng Shangguan ◽  
Zhanbin Wang
Keyword(s):  
Stress State ◽  
Strain Rate ◽  
Ground Motions ◽  
Pure Shear ◽  
Radial Strain ◽  
Complex Stress State ◽  
Asymmetric Effect ◽  
Principal Stresses ◽  
Input Motion ◽  
Spatially Varying

Seismic behavior of long circle tunnels is significantly influenced by the nature of input motion. This study, based on the 3D finite-element method (FEM), evaluates the effects of spatially varying seismic ground motions and uniform input seismic ground motions and their incident angles on the diameter strain rate and tensive/compressive principal stresses under different strata. It is found that (1) the spatially varying seismic ground motions induced larger diameter strain rate (radially deformation) than the uniform input seismic motion, (2) the spatially varying seismic ground motions had an asymmetric effect on the radial strain rate distributions, and (3) the rising incident angles changed the pure shear stress state into a complex stress state for tunnels under specified input motion.

scholarly journals A new stress-based topology optimization approach for finding flexible structures

2021 ◽  
Author(s):  
Martin Noack ◽  
Arnold Kühhorn ◽  
Markus Kober ◽  
Matthias Firl
Keyword(s):  
Topology Optimization ◽  
Stress State ◽  
Design Space ◽  
Flexible Structures ◽  
Optimization Approach ◽  
Principal Stresses ◽  
Output Displacement ◽  
Design Concepts ◽  
Flexible Designs ◽  
Gauss Points

AbstractThis paper presents a new FE-based stress-related topology optimization approach for finding bending governed flexible designs. Thereby, the knowledge about an output displacement or force as well as the detailed mounting position is not necessary for the application. The newly developed objective function makes use of the varying stress distribution in the cross section of flexible structures. Hence, each element of the design space must be evaluated with respect to its stress state. Therefore, the method prefers elements experiencing a bending or shear load over elements which are mainly subjected to membrane stresses. In order to determine the stress state of the elements, we use the principal stresses at the Gauss points. For demonstrating the feasibility of the new topology optimization approach, three academic examples are presented and discussed. As a result, the developed sensitivity-based algorithm is able to find usable flexible design concepts with a nearly discrete 0 − 1 density distribution for these examples.

Turbulent-like velocity fluctuations in two-dimensional granular materials subject to cyclic shear

Soft Matter ◽  
2022 ◽  
Author(s):  
Aile Sun ◽  
Yinqiao Wang ◽  
Yangrui Chen ◽  
Jin Shang ◽  
Jie Zheng ◽  
...  
Keyword(s):  
Experimental Study ◽  
Granular Materials ◽  
Granular Matter ◽  
Two Dimensional ◽  
Friction Coefficients ◽  
Velocity Fluctuations ◽  
Cyclic Shear

We perform a systematic experimental study to investigate the velocity fluctuations in the two-dimensional granular matter of low and high friction coefficients subjected to cyclic shear of a range of...

Deformation distortions of geometric form tube blanks in the process of drilling holes

2021 ◽  
pp. 104-110
Author(s):  
A.N. Isaev ◽  
S.V. Vlaskin ◽  
V.A. Lebedev ◽  
M.D. Gavrilenko
Keyword(s):  
Stress State ◽  
Wall Thickness ◽  
Cross Sections ◽  
Theoretical Studies ◽  
Geometric Form ◽  
Axisymmetric Stress ◽  
Axisymmetric Stress State ◽  
Elastic Plastic ◽  
The Cross

The influence of deviations of the shape of the cross-sections of pipes from roundness on the axisymmetric stress state and taking this factor into account in theoretical studies and methods for solving problems of mandrel drilling in the elastic-plastic mode are considered. The features of the choice of tubular blanks, which help to reduce the unevenness of deformation and increase the accuracy of processing in the process of mandrel drilling, are revealed. Recommendations are given for eliminating the variance in wall thickness of blanks at the stage of their preparation for the mandrel operation.

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