A Shear Band is a narrow zone of intense Shearing strain within a largely unSheared matrix. During the Shear Band formation, relative tangential displacement of blocks of material on two sides of the Band occurs. Width of this region varies from a few to hundreds of microns. Despite the infinitesimal width of the Band, its relative tangential deformation may extend to several centimeters and may even lead to exertion of macroscopic influence on the medium. In this paper, a new method for modeling of Shear Band is presented. A bifurcation analysis is used to detect the onset of localization in an element to determine the geometry of the localized deformation modes. Therefore, a computational procedure is discussed for detecting the onset of localization and determining the localization directions and the Shear Band path. A zero thickness element is utilized to simulate the slip surface in the Shear Band. Plane strain condition is assumed in numerical simulations, and elasto-plastic finite element method is used in analysis. When the onset of localization is detected, the zero thickness element is added to the Shear Band path, which closely reproduces the Shear Band response. The proposed methodology is applied to two numerical examples, and the results are compared with the other existing methods which demonstrate the ability of the method to resolve the geometry of localized failure modes and reproduce the Shear Band response. The first example is a simple Shear problem that includes a rectangular solid with fixed supports in its bottom, subjected to uniform Shear deformation on the upper boundary. The second example is a slope failure problem, which includes a downward displacement applied to the middle of a rigid block on the top of a slope. The Shear Band path and the force-displacement curves are plotted for both examples and have good agreement with the reported results.

The dynamic localization of saturated soil is investigated by considering the influence of higher strain gradient. It is shown that the strain gradient has a significant influence on the evolution of Shear Band in saturated soil and that the width of Shear Band is proportional to the square root of the strain gradient softening coefficient. The numerical simulation is processed to investigate the influences of Shear strain gradient and other factors on the evolution of Shear Band.

The capability of sand constitutive models is remarkably improved by taking into account the effect of soil state in their formulations. In this study, it has been shown that considering the effect of soil state leads to better simulation of soil instability of Shear Banding type. To this aim, constitutive equations of a state dependent sand model are explained first. Consequently, the general conditions of instability and then, the special condition of instability with respect to the model formulation has been obtained. Using the result of a number of plane strain tests, the state dependent model predictions for Shear Band have been compared with experiment results. It has been shown that, predictions obtained from a similar model which neglect the effect of soil state are less favorable.

Subjected to external loads, granular materials experience severe deformation in a narrow zone before their failure. This phenomenon, which is called strain localisation or Shear Band, is of vital importance in assessing the stability of the geotechnical structure, studying the stress-strain behaviour of soil and rock materials, and analysing the interaction of soil and structure. The present study is aimed to investigate the effect of various factors on the pattern and inclination of Shear Band in a general three-dimensional condition of stress using the Discrete Element Method (DEM). Several tests were simulated using a developed version of the TRUBAL program called GRANULE. The GRANULE code was further developed to add the capability of carrying out simulations with different intermediate principal stresses and modelling specimens containing non-spherical particles. The Shear Band was detected by tracking the motion of the particles and plotting the rotation distribution of particles within the sample. The results prove that the Shear Band inclination and its pattern, are greatly affected by intermediate principal stress, particle shape, and confining stress. Moreover, it was observed that the change in the b value plays a key role in the alteration of the 3D configuration of the Shear Band.

Shear Banding is one of the most significant behavioral characteristics of granular soils, which is actually the result of the localization of deformations under loads applied to the soil sample. Many studies have been conducted on the phenomenon of Shear Band formation. However, the comparison of the behavior of soil inside and outside the Shear Band has received less attention. The purpose of this study is to compare the behavior of soil inside and outside the Shear Band in the direct Shear test at macro and micro scales using the two-dimensional discrete element method. To achieve this, the micro-material parameters were first calibrated through the comparison of simulation and experimental results. Then a parametric study was conducted by performing 9 direct Shear tests with different vertical stresses on three soil samples with different relative densities. During the tests, quantities such as Shear stress, porosity, particle rotation, coordination number, and interparticle plastic energy were measured both inside and outside the Shear Band. The results of the present study showed that the particle rotations at the end of the test inside the Shear Band were 5 to 17 times higher than those outside the Shear Band. Furthermore, the results showed that the dissipated energies at the end of the test inside the Shear Band were 12 to 96 times larger than those outside the Shear Band. Moreover, it was found that the coordination numbers at the end of the test inside the Shear Band were on average 3-19% lesser than those outside it.

Background & Aim: The purpose of this study was to evaluate the micro-Shear bond strength of two kinds of resin-based cements with fluoride release with the usage of five adhesive systems to enamel and dentin. Materials & methods: Bovine flat enamel or dentin surfaces were used in this study. Micro cylinders of resin cement with Xeno Cem Plus (XCP) or Panavia Fluoro Cement (PFC) were bonded to enamel or dentin as followed: XCP or PFC as instructions prior to the usage of their own adhesive systems, Xeno CF II+XCP, SE Bond+PFC, or Clearfil Liner Bond II (CLB) + PFC. After the storage in 37°c water for 24 hrs, micro-Shear bond test was applied for all the test groups. The data were statistically analyzed using two-way analysis of variance (ANOVA). After two-way ANOVA, one-way ANOVA and multiple comparisons with Fishers PLSD test were made.Results: Are given as follow (enamel and dentin, mean±SD in MPa); XCP, 13.7±4.0 and 15.5±9.2; PFC, 23.7±10.6 and 15.0±7.3; XCP+XCF II, 35.4±11.5 and 17.1±4.0; PFC+SE, 54.2±9.8 and 41.7±12.0; PFCCLB, 31.39±3.09 and 15.09±4.35. ANOVA (α=0.05) analyze revealed the usage of SE Bond under PFC significantly increased the bond strength to both enamel and dentin. Bonding of Xeno CFII was only improved the bonding to enamel with the application of XCP.Conclusion: Light-cure adhesive systems significantly improve the bonding of current resin cements.

Background & Aim: The goal of many researchers conducted nowadays is to achieve adhesive materials that exhibit good bonding capability, simplified application and easy handling. In this regard, self - etching primer systems were introduced to the market. The aim of this study was to evaluate the micro- Shear bond strength of two new self - etching materials compared to an already established bonding materials. Methods & Materials: Sections of human third molars (1.5 mm) were used in this study. The tooth surfaces were polished with 600 grit SiC paper nder running water and randomly divided into three groups. In group I Clearfil Protect Bond (Kuraray Japan), in group II, Clearfil SE Bond (Kurary Japan) as control group, and in group ill, Clearfil Tri - S Bond (KUrary Japan) were used due to manufacturer's instruction. Hollow tygon tubes (0.7×0.5mm) were placed on the enamel and dentin surfaces and Clearfil AP-X composite was inserted into the tubes. After 40 seconds light curing, the tygon tubes were removed and samples were stored in distilled water for 24 hours. Micro – Shear bond strength was measured (EZ-test, Shimadzu Co., Kyoto, Japan) and the data was statistically analysis by one - way ANOVA and multiple comparison with LSD.Result: Mean bond strength in enamel was 35.76±6.89 mpa in group I; 33.62±5.59 mpa in group II, and 34.65±5.65 mpa in group III. Their difference was not statically significant. Mean bond strength in dentin was 34.47±6.0 mpa in group I, 45.20±10.3 mpa in group II, and 35.99±6.13 mpa in group III. The bond strength in group II was higher than group I and II (P<0.05), and the difference between group I and II was not statistically significant.Conclusion: After 24 hours, the Shear bond strength of two new adhesive systems to enamel was similar to SE Bond, however, SE Bond exhibited a higher bond strength to dentine.