scholarly journals Numerical Analysis of Shear and Particle Crushing Characteristics in Ring Shear System Using the PFC2D

Materials ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 229
Author(s):  
Sueng-Won Jeong ◽  
Kabuyaya Kighuta ◽  
Dong-Eun Lee ◽  
Sung-Sik Park
Keyword(s):  
Shear Stress ◽  
Numerical Analysis ◽  
Normal Stress ◽  
Numerical Results ◽  
Particle Flow Code ◽  
Shear Stresses ◽  
Particle Crushing ◽  
Ring Shear ◽  
Peak Shear Stress ◽  
Residual Shear Stress

The shear and particle crushing characteristics of the failure plane (or shear surface) in catastrophic mass movements are examined with a ring shear apparatus, which is generally employed owing to its suitability for large deformations. Based on results of previous experiments on waste materials from abandoned mine deposits, we employed a simple numerical model based on ring shear testing using the particle flow code (PFC2D). We examined drainage, normal stress, and shear velocity dependent shear characteristics of landslide materials. For shear velocities of 0.1 and 100 mm/s and normal stress (NS) of 25 kPa, the numerical results are in good agreement with those obtained from experimental results. The difference between the experimental and numerical results of the residual shear stress was approximately 0.4 kPa for NS equal to 25 kPa and 0.9 kPa for NS equal to 100 kPa for both drained and undrained condition. In addition, we examined particle crushing effect during shearing using the frictional work concept in PFC. We calculated the work done by friction at both peak and residual shear stresses, and then used the results as crushing criteria in the numerical analysis. The frictional work at peak and the residual shear stresses was ranged from 303 kPa·s to 2579 kPa·s for given drainage and normal stress conditions. These results showed that clump particles were partially crushed at peak shear stress, and further particle crushing with respect to the production of finer in shearing was recorded at residual shear stress at the shearing plane.

scholarly journals A modified X-ray diffraction method to measure residual normal and shear stresses of machined surfaces

2022 ◽  
Author(s):  
Quanshun Luo
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
New Method ◽  
Shear Stresses ◽  
X Ray Diffraction ◽  
Tin Coating ◽  
New Approach ◽  
X Ray ◽  
Residual Shear Stress ◽  
Normal And Shear Stresses

AbstractX-ray diffraction has been widely used in measuring surface residual stresses. A drawback of the conventional d ~ sin2ψ method is the increased uncertainty arising from sin2ψ splitting when a significant residual shear stress co-exists with a residual normal stress. In particular, the conventional method can only be applied to measure the residual normal stress while leaving the residual shear stress unknown. In this paper, we propose a new approach to make simultaneous measurement of both residual normal and shear stresses. Theoretical development of the new approach is described in detail, which includes two linear regressions, $$\frac{{d}_{\psi }+ {d}_{-\psi }}{2}$$ d ψ + d - ψ 2 ~sin2ψ and {dψ-d-ψ} ~ sin(2ψ), to determine the residual normal and shear stresses separately. Several samples were employed to demonstrate the new method, including turning-machined and grinding-machined cylindrical bars of a high strength steel as well as a flat sample of magnetron sputtered TiN coating. The machined samples were determined to have residual compressive normal stresses at both the axial and hoop directions as well as various scales of residual shear stresses. The TiN coating showed a high scale of residual compressive (normal) stress whereas the measured residual shear stress was extremely low. The new method showed significantly increased precision as compared to the conventional d ~ sin2ψ method.

scholarly journals Empirical Studies of Ice Sliding

1979 ◽  
Vol 23 (89) ◽  
pp. 157-170 ◽  
Author(s):  
W. F. Budd ◽  
P. L. Keage ◽  
N. A. Blundy
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Sliding Friction ◽  
Normal Load ◽  
Water Pressure ◽  
Empirical Studies ◽  
Shear Stresses ◽  
Friction Characteristic ◽  
Wide Range ◽  
Static Shear

AbstractAn experimental programme has been carried out for studying temperate-ice sliding over rock surfaces with a wide range of roughnesses, for normal and shear stresses comparable to those expected under real ice masses. The limiting static shear stress for acceleration has been found to be directly proportional to the normal load giving a constant limiting coefficient of static friction characteristic of the surface. For a constant applied normal stress N and shear stress τb, well below the limiting static shear, a steady velocity Vb results which increases approximately proportionally to τb and decreases with increasing N and the roughness of the surface. For high normal stress the velocity becomes approximately proportional to the shear stress cubed and inversely proportional to the normal stress. As the shear stress increases acceleration sets in, which, for different roughness and normal loads, tends to occur for a constant value of the product τbVb. For some surfaces at high normal loads this acceleration was retarded by erosion. For constant-applied-velocity tests a steady shear stress resulted, which tended to become constant with high velocities, and which increased with increasing normal stress but with a reduced coefficient of sliding friction. The relevance of the results to the sliding of real ice masses is discussed with particular reference to the importance of the effect of the relative normal stress, above basal water pressure, to the sliding rate.

Numerical Study of Cruciform Specimens for Biaxial Tensile Tests

2016 ◽  
Author(s):  
Luis F. Puente Medellín ◽  
Antonio Balvantin ◽  
J. A. Diosdado-De la Peña
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Normal Stress ◽  
Sheet Metal ◽  
Numerical Study ◽  
Tensile Tests ◽  
Thickness Reduction ◽  
Shear Stresses ◽  
Normal Stress Distribution ◽  
Biaxial Tensile

This paper presents a numerical study of different geometries of cruciform specimens for biaxial tensile tests. The aim of these specimens is to be used on fixtures for biaxial tests mounted in universal testing machines. For the study, a model of isotropic material for steel sheet metal specimens was considered. Thus, only the mechanical properties of the sheet metal in the rolling direction were considered in the simulations. In this numerical analysis, the normal stress distribution and the consequent shear stress were studied. Additionally, the effect of the inclusion of multiple slots as well as a thickness reduction on the normal and shear stresses were assessed. Hence, a specimen in which a uniform normal stress distribution with zero shear stress, is necessary. The results of the analysis show that a specimen with features, multiple slots and a thickness reduction in the central area, provides a better performance in the simulations than dismissing any of these characteristics. Finally, a specimen model suitable for the mentioned test is proposed according to the obtained numerical results and the feasibility of manufacture of the experimental sample-test.

scholarly journals Study on Failure Characteristics and Acoustic Emission Characteristics of Sandstone Under Variable Angle Shear

2021 ◽  
Author(s):  
Feng Luo ◽  
Peidong Xu ◽  
Yijun Guo ◽  
Yanglong Diao ◽  
Meng Li
Keyword(s):  
Shear Stress ◽  
Acoustic Emission ◽  
Normal Stress ◽  
Failure Process ◽  
Shear Angle ◽  
Shear Cracks ◽  
Failure Characteristics ◽  
Variable Angle ◽  
Secondary Cracks ◽  
Peak Shear Stress

Abstract To study the shear damage and failure characteristics of red sandstone under different normal stress conditions, the failure process of sandstone under three different shear angles (50°, 55°, 60°) were studied by using variable angle shear test device. The shear stress-deformation curves and failure characteristics of sandstone were obtained, and the relationships between shear cracks and acoustic emission impact times, amplitude, peak frequency were established. With the increase of shear angle, the normal stress, shear stress and peak shear stress decrease gradually. The development of micro-cracks in the shear plane appear more earlier. The high frequency signal decreases significantly, which may have a significant corresponding relationship with the rock friction and shear effect. The failure mode of rock changes from plasticity to brittleness. The amplitude changes are concave, and more acoustic emission energy is released at compaction stage and plastic(failure) stage. The rock spalling mainly occur in the penetrating area of main and secondary cracks surrounding the two ends of specimen. The spalling degree was obviously weakened with the increase of shear angle. The results have important guiding value for judging and predicting the instability mechanism of rock engineering.

scholarly journals Coupling between a glacier and a soft bed: I. A relation between effective pressure and local shear stress determined from till elasticity

1999 ◽  
Vol 45 (149) ◽  
pp. 31-40 ◽  
Author(s):  
Neal R. Iverson ◽  
Robert W. Baker ◽  
Roger LeB. Hooke ◽  
Brian Hanson ◽  
Peter Jansson
Keyword(s):  
Shear Stress ◽  
Shear Strain ◽  
Water Pressure ◽  
Shear Stresses ◽  
Effective Pressure ◽  
Interface Shear ◽  
Shear Moduli ◽  
Ring Shear ◽  
Local Shear ◽  
Local Shear Stress

AbstractTo predict the distribution of motion beneath glaciers on soft beds, the strength of the coupling between the ice and the bed and its variation with effective pressure must be known. A record of shear strain, acquired with a tiltmeter emplaced in till beneath Storglaciären, Sweden, indicates that fluctuations in water pressure cause variations in the local shear stress on the bed and that the bed deforms elastically in response to these variations. To estimate the shear stress from the elastic component of the total shear strain, the shear modulus of the till was measured in relaxation tests conducted in the laboratory with a ring-shear device. After accounting for the elastic compliance of the device, these tests yielded shear moduli of about 1000 and 1800 kPa at confining pressures of 85 and 280 kPa, respectively. These values are comparable to those of other granular materials undergoing recoverable shear strains of the same magnitude. The local shear stress on the till, calculated by applying the measured shear moduli to the tilt record, scales with Pe1.7, where Pe is the effective pressure. This relation implies that as Pe decreases at the ice/till interface, shear stresses on the till are reduced and concentrated elsewhere on the bed, perhaps where the till is absent or the glacier is frozen to the bed. When compared with the strength of the till determined from ring-shear tests, this relation also accounts for the lack of permanent deformation at depth in the bed during periods of low Pe and indicates that most basal motion was by sliding or ploughing.

Shear Stress Analysis of Long-Span Steel Bridge Deck Asphalt Pavement Using FEM

2011 ◽  
Vol 304 ◽  
pp. 12-17 ◽  
Author(s):  
Chun Hua Hu ◽  
Jin Qian
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Bridge Deck ◽  
Maximum Shear Stress ◽  
Element Model ◽  
Outer Side ◽  
Shear Stresses ◽  
Steel Bridge ◽  
Long Span ◽  
Peak Shear Stress

Asphalt pavements have been widely used to protect the steel bridge deck against moisture and provide good riding quality. However, various types of distresses especially rutting have been observed frequently in bridge deck asphalt layers. Therefore it is necessary to understand the mechanics behavior of asphalt layer in the steel bridge deck. In this paper, finite element model for bridge deck with asphalt layers have been setup. Then shear stresses have been analyzed in the various cases using finite element method. The results show that the most disadvantage position locates above the diaphragm plate outer side. The shear stress between layers decreases with the increase of the asphalt layer thickness, the peak shear stress increases either. The thin surface layer has its advantage with the requirement of the minimum paving thickness if bonding properly. Comparison with the common pavement structure, the maximum shear stress in the bridge deck pavement could be affected by the type of loading more significant.

scholarly journals Empirical Studies of Ice Sliding

1979 ◽  
Vol 23 (89) ◽  
pp. 157-170 ◽  
Author(s):  
W. F. Budd ◽  
P. L. Keage ◽  
N. A. Blundy
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Sliding Friction ◽  
Normal Load ◽  
Water Pressure ◽  
Empirical Studies ◽  
Shear Stresses ◽  
Friction Characteristic ◽  
Wide Range ◽  
Static Shear

Abstract An experimental programme has been carried out for studying temperate-ice sliding over rock surfaces with a wide range of roughnesses, for normal and shear stresses comparable to those expected under real ice masses. The limiting static shear stress for acceleration has been found to be directly proportional to the normal load giving a constant limiting coefficient of static friction characteristic of the surface. For a constant applied normal stress N and shear stress τ b, well below the limiting static shear, a steady velocity Vb results which increases approximately proportionally to τ b and decreases with increasing N and the roughness of the surface. For high normal stress the velocity becomes approximately proportional to the shear stress cubed and inversely proportional to the normal stress. As the shear stress increases acceleration sets in, which, for different roughness and normal loads, tends to occur for a constant value of the product τ b Vb . For some surfaces at high normal loads this acceleration was retarded by erosion. For constant-applied-velocity tests a steady shear stress resulted, which tended to become constant with high velocities, and which increased with increasing normal stress but with a reduced coefficient of sliding friction. The relevance of the results to the sliding of real ice masses is discussed with particular reference to the importance of the effect of the relative normal stress, above basal water pressure, to the sliding rate.

Fabrication and Characterization of Normal and Shear Stresses Sensitive Tactile Sensors by Using Inclined Micro-cantilevers Covered with Elastomer

2007 ◽  
Vol 1052 ◽  
Author(s):  
Masayuki Sohgawa ◽  
Yu-Ming Huang ◽  
Minoru Noda ◽  
Takeshi Kanashima ◽  
Kaoru Yamashita ◽  
...  
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Tactile Sensor ◽  
Shear Stresses ◽  
Tactile Sensors ◽  
Orthogonal Direction ◽  
Pdms Elastomer ◽  
Control Layer ◽  
Human Support

AbstractThe tactile sensors for human support robots which can detect both normal stress and shear stress and have human-friendly surface have been proposed. Micro-cantilevers adequately inclined by Cr deflection control layer were fabricated by the surface micromachining on SOI wafer. The cantilevers were covered with the PDMS elastomer for human-friendly surface. When the stress is added to the surface of elastomer, the deformation of cantilevers along with elastomer is detected as piezoresistive layer in the cantilevers. The piezoresistive response of the cantilever is analyzed by FEM calculation. The response of the fabricated tactile sensor to normal stress and shear stress was measured by output from this resistance. The tactile sensor with PDMS elastomer can detect both normal stress and shear stress. On the other hand, it hardly has sensitivity to shear stress of orthogonal direction to the cantilever. It means that the tactile sensor can distinguish the direction of shear stress. The sensitivity of tactile sensor vary widely with cantilever pattern and relation between direction of cantilever and crystallite orientation of Si. It is suggested that the sensitivity of tactile sensor can be improved by using FEM estimation and selective ion implantation.

scholarly journals REDUCTION OF RESIDUAL SHEAR STRESS IN THE LOADED CONTACT USING FRICTION HYSTERESIS

2016 ◽  
Vol 14 (2) ◽  
pp. 159 ◽  
Author(s):  
Adrian Kraft ◽  
Roman Pohrt
Keyword(s):  
Shear Stress ◽  
Normal Force ◽  
Shear Stresses ◽  
Tangential Contact ◽  
Absolute Value ◽  
Method Of Dimensionality Reduction ◽  
Final Stress ◽  
External Forces ◽  
Residual Shear Stress ◽  
Special Case

We investigate the tangential contact problem of a spherical indenter at constant normal force. When the indenter is subjected to tangential movement, frictional shear stresses arise at the interface and do not vanish when it is moved backwards. We study the evolution of shear stress when the indenter is moved back and forth at falling amplitude. The method of dimensionality reduction (MDR) is employed for obtaining the distribution of stick and slip zones as well as external forces and the final stress distribution. We find that the shear stress decreases. For the special case of linearly falling amplitude of the movement, we observe uniform peaks in the shear stress. The absolute value of the shear stress peaks is reduced best for a high number of back-and-forth-movements with slowly decreasing amplitude.

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