• Geotechnical Engineering
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• v.4 no.1
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• pp.17-28
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• 1988

Among several types of element tests to predict soil behalf.iota in a laboratory, the torsion shear apparatus, in which the directions of principal stresses could be rotated during shearing, wra explained. In this study, this torsion shear apparatus was improved so as to be used in tests on clay specimens . And some undrained torsion shear tests u.ere performed on remolded specimens of Ko-consolidated clay to investigate the influence of reorientation of the principal stress directions on the stress-strain behavior The soil behavior by the torsion shear apparatus without torque was compared It.ith that by the conventional triaxial compression tests . The stress path, provided by both vertical loads and torque during torsion shear tests, has much effect on the stress-strain behavior, the pore pressure and the effective principal stress ratio . The rotation angle of the principal stress and the b-value were gradually increased with increasing shear strain, but converged to the values at failure.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.442-451
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• 2008

The evaluation of field degree of consolidation on soft clays has been an important problem in geotechnical areas. Monitoring either settlements or pore water pressures has been widely applied in the filed, but occasionally they have some problems. This study addresses the suggestion and application of another method for evaluating the degree of consolidation using shear wave velocities. A research site where soft clay layers were consolidated by surcharging loads was chosen. Laboratory tests were performed to determine the relation between shear wave velocity and effective stress. Field seismic tests were conducted several times during the consolidation of the clay layers. The tests results show that the shear wave velocity increased significantly as clays consolidated. The shear wave velocities at each field stress states were derived from the laboratory results and the degree of consolidation was evaluated by comparing the shear wave velocities obtained by laboratory and field seismic methods. In most stress states, the degree of consolidation evaluated using the shear wave velocity matched well with that obtained from field settlement record, showing the potential of applying the method using shear waves in the evaluation of field degree of consolidation on soft clay deposits.

• Transactions of Materials Processing
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• v.32 no.2
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• pp.92-99
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• 2023

In this study, shear fracture specimens are designed using finite element analyses for the characterization of ductile fracture criteria of metal sheets. Many recently suggested ductile fracture criteria require experimental fracture data at the shear stress states in the model parameter identification. However, it is challenging to maintain shear stress states in tension-based specimens from the initial yield to the final fracture, and the loading path can be different for the different materials even with the same shear specimen geometries. To account for this issue, two different shear fracture specimens for low ductility/high ductility metal sheets are designed using the sensitivity tests conducted by finite element simulations. Priorly mechanical properties including the Hosford-Coulomb fracture criterion of the aluminum alloy 7075-T6 and DP590 steel sheets are used in the simulations. The results show that shear stress states are well-maintained until the fracture at the fracture initiation points by optimizing the notch geometries of the shear fracture specimens.

• Computational Structural Engineering
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• v.8 no.1
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• pp.137-146
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• 1995

Structural stress under shock or impact load is varied with the lapse of time and the structural stress is called stress wave. Propagating longitudinal stress wave is studied in a 2-dimensional plate. A finite element program for elastic stress wave propagation is developed in order to investigate the shape of stress field at time increment. The longitudinal stress wave is generated by unit step function. According to the finite element analysis results, the longitudinal stress wave propagates to the similar direction of impact load and the front of stress wave propagates with the same speed as analytic solution and the shape of stress field is similar to that of analytic solution. The shear wave is occurred after the longitudinal stress wave and declined at an angle of 45 degrees compared with longitudinal stress wave and the speed of shear wave is about a half of the longitudinal stress wave. The intensity of shear wave is larger than that of longitudinal stress wave.

• Geomechanics and Engineering
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• v.13 no.5
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• pp.743-756
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• 2017

Laboratory investigation reveals that rockfills exhibit significant stress-path-dependent behavior during shearing, therefore realistic prediction of deformation of rockfill structures requires suitable constitutive models to properly reproduce such behavior. This paper evaluates the capability of a strain hardening model proposed by the authors, by comparing simulation results with large-scale triaxial stress-path test results. Despite of its simplicity, the model can simulate essential aspects of the shear behavior of rockfills, including the non-linear stress-strain relationship, the stress-dependence of the stiffness, the non-linear strength behavior, and the shearing contraction and dilatancy. More importantly, the model is shown to predict the markedly different stress-strain and volumetric behavior along various loading paths with fair accuracy. All parameters required for the model can be derived entirely from the results of conventional large triaxial tests with constant confining pressures.

• Tunnel and Underground Space
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• v.4 no.3
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• pp.261-273
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• 1994

Direct shear tests were carried out on the rock joints and artificial discontinuities to investigate the influence of joint roughness on the shear strength and deformation behaviour. Single direct shear testing apparatus used in experiment was designed and manufactured. Its capacity is 200 tons of shear load, 20 tons of normal load and 50$\textrm{cm}^2$ of maximum shear area. Test samples were cement mortar with artificial discontinuity and sandstone with natural joint. Peak shear strength was increased as joint roughness or normal stress was increased, especially, linearly increased with roughness angle in cement mortar. If joint roughness angle was constant at low normal stress, shear strength was not affected by width and height of joint roughness in cement mortar. Peak shear strengths obtained from tests were larger than the values calculated by Barton's equation, and shear stiffness was increased with joint roughness coefficient.

• Korea-Australia Rheology Journal
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• v.14 no.4
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• pp.189-201
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• 2002

The interaction between hydrophobically modified hydroxyethyl cellulose (hmHEC), containing approximately 1 wt% side-alkyl chains of $C_{16}$, and an anionic sodium dodecyl sulphate (SDS) surfactant was investigated. For a semi-dilute solution of 0.5 wt% hmHEC, the previously observed behaviour of a maximum in solution viscosity at intermediate SDS concentrations, followed by a drop at higher SDS concentrations, until above the cmc of surfactant when the solution resembles that of the unsubstituted polymer, was confirmed. Additionally, a two-phase region containing a hydrogel phase and a water-like supernatant was found at low SDS concentrations up to 0.2 wt%, a concentration which is akin to the critical association concentration, cac, of SDS in the presence of hmHEC. Above this concentration, SDS molecules bind strongly to form mixed micellar aggregates with the polymer alkyl side-chains, thus strengthening the network junctions, resulting in the observed increase in viscosity and elastic modulus of the solution. The shear behaviour of this polymer-surfactant complex during steady and step stress experiments was examined In great detail. Between SDS concentrations of 0.2 and 0.25 wt%, the shear viscosity of the hmHEC-polymer complex network undergoes shear-induced thickening, followed by a two-stage shear-induced fracture or break-up of the network. The thickening is thought to be due to structural rearrangement, causing the network of flexible polymers to expand, enabling some polymer hydrophobic groups to be converted from intra- to inter-chain associations. At higher applied stress, a partial local break-up of the network occurs, while at even higher stress, above the critical or network yield stress, a complete fracture of the network into small microgel-like units, Is believed to occur. This second network rupture is progressive with time of shear and no steady state in viscosity was observed even after 300 s. The structure which was reformed after the cessation of shear is found to be significantly different from the original state.

• Animal cells and systems
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• v.8 no.1
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• pp.27-32
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• 2004

Endothellial cells are subjected to hemodynamic shear stress, the dragging force generated by blood flow. Shear stress regulates endothelial cell shape, structure, and function, including gene expression. Since endothelial cells must be anchored to their extracellular matrices(ECM) for their survival and growth, we hypothesized that ECMs are crucial for shear-dependent activation of extracellular signalactivated regulated kinase(ERK) that is important for cell proliferation. Shear stress-dependent activation of ERK was observed in cells plated on two different matrices, fibronectin and vitronectin(the two most physiologically relevant ECM in endothelial cells). We then treated bovine aortic endothelial cells(BAECs) with Arg-Gly-Asp(RGD) peptides that block the functional activation of integrin binding to fibronectin and vitronectin, and a nonfunctional peptide as a control. Treatment of cells with the RGD peptides, but not the control peptide, significantly inhibited ERK activity in a concentration-dependent manner. This supports the idea that integrin adhesion to the ligands, fibronectin and vitronectin, mediates shear stress-dependent activation of ERK. Subsequently, whereas antagonists of vitronectin(LM 609, an antibody for integrin ${\alpha}_{\gamma}$/${\beta}_3$ and XT 199, an antagonist specific for integrin ${\alpha}_{\gamma}$/${\beta}_3$) did not have any effect on shear-dependent activation of ERK, antagonists of fibronectin(a neutralizing antibody for integrin ${\alpha}_5$/${\beta}_1$or ${\alpha}_4$${\beta}_1$ and SM256) had an inhibitory effect. These results clearly demonstrate that mechanoactivation of ERK requires anchoring of endothelial cells to fibronectin through integrins.

• Journal of the Korean GEO-environmental Society
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• v.11 no.11
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• pp.47-54
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• 2010

Nowadays, geosynthetics for reinforcement and protection are widely applied to the waste landfill site. Current research indicates the potential for progressive failure in geosynthetic-soil system depends on the interface shear strength governed by several intrinsic factors such as moisture, normal stress, chemical, etc. In particular, the effect of the acidity and basicity from the leachate is intensively reviewed to assess the chemical reaction mechanism of interface shear strength under the cyclic loading condition. New multi-purpose interface apparatus(M-PIA) has been manufactured and the cyclic direct shear tests using submerged geosynthetics and soils under the different chemical conditions have been performed, consequently, the thickness of interface and shear stress degradation are verified. The basic schematic of the Disturbed State Concept(DSC) is employed to estimate the shear stress degradation in the interface, then, normalized disturbed function is obtained and analyzed to describe the shear stress degradation of geosynthetic-soil interface with chemical influence factors under dynamic condition.

• International Journal of Precision Engineering and Manufacturing
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• v.6 no.3
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• pp.24-28
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• 2005

Stress state of chip formation zone is one of the main problems in metal cutting mechanics. In two-dimensional case this process is usually considered as consistent shears of work material along one of several shear surfaces, separating chip from workpiece. These shear planes are assumed to be trajectories of maximum shear stress forming corresponding slip-line field. This paper suggests a new approach to the constriction of slip-line field, which implies uniform compression in chip formation zone. Based on the given model it has been found that imaginary shear line in orthogonal cutting is close to the trajectory of maximum normal stress and the problem about its determination has been considered as well. It has been shown that there is a second central slip-line field inside chip, which corresponds well to experimental data about stress distribution on tool rake face and tool-chip contact length. The suggested model would be useful in understanding mechanistic problems in machining.