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.

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.

Erosional Process of Cohesive Sediments

1985 ◽  
Vol 17 (6-7) ◽  
pp. 891-901 ◽  
Author(s):  
T. Kusuda ◽  
T. Umita ◽  
K. Koga ◽  
T. Futawatari ◽  
Y. Awaya
Keyword(s):  
Shear Stress ◽  
Solid Fraction ◽  
Velocity Gradient ◽  
Shear Stresses ◽  
Cohesive Sediments ◽  
Erosion Process ◽  
Absolute Value ◽  
Constant Shear ◽  
Yield Value ◽  
Simulation Based

Tests on erosion of the cohesive sediments in the Chikugo estuary in Japan were conducted. The results indicate that the decrease in the rate of erosion at constant shear stresses is caused rapidly 20 to 30 minutes after the start of tests and that tue decrease is caused by the increase in the solid fraction and the yield value of the seaiment remaining uneroded due to shear stress. In order to simulate the erosion process of sediments, a model in which the increase in the yield value of sediment is assumed to be proportional to the integration value of the absolute value of the sediment velocity gradient with respect to time was developed. The simulation based on this model is shown to be available to estimate the amount of sediments eroded in the erosional process of cohesive sediments.

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.

Tire Treadwear — A Comprehensive Evaluation of the Factors: Generic Type, Aspect Ratio, Tread Pattern, and Tread Composition Part IV: Laboratory Measurement of Mechanical Properties and Mechanical Actions of Tires Relating to Treadwear

1986 ◽  
Vol 14 (4) ◽  
pp. 264-291
Author(s):  
K. L. Oblizajek ◽  
A. G. Veith
Keyword(s):  
Mechanical Properties ◽  
Shear Stress ◽  
Contact Zone ◽  
Flexural Rigidity ◽  
Comprehensive Evaluation ◽  
Shear Stiffness ◽  
Shear Stresses ◽  
Lateral Shear ◽  
Band Bending ◽  
Tread Rubber

Abstract Treadwear is explained by specific mechanical properties and actions of tires. Rubber shear stresses in the contact zone between the tire and the road become large at large slip angles. When normal stresses are insufficient to prevent sliding at the rear of the footprint, wear occurs at a rate that depends on test severity. Two experimental approaches are described to relate treadwear to tire characteristics. The first uses transducers imbedded in a simulated road surface to obtain direct measurements of contact stresses on the loaded, freely-rolling, steered tires. The second approach is developed with the aid of a simple carcass, tread-band, tread-rubber tire model. Various tire structural configurations; characterized by carcass spring rate, edgewise flexural band stiffness, and tread rubber shear stiffness; are simulated and lateral shear stress response in the contact zone is determined. Tires featuring high band stiffness and low carcass stiffness generate lower lateral shear stress levels. Furthermore, coupling of tread-rubber stiffness and band flexural rigidity are important in determining level of shear stresses. Laboratory measurements with the described apparatus produced values of tread-band bending and carcass lateral stiffness for several tire constructions. Good correlation is shown between treadwear and a broad range of tire stiffness and test course severities.

Finite Element Analysis of Tire/Rim Interface Forces Under Braking and Cornering Loads

1992 ◽  
Vol 20 (2) ◽  
pp. 83-105 ◽  
Author(s):  
J. P. Jeusette ◽  
M. Theves
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Contact Pressure ◽  
Element Model ◽  
Shear Stresses ◽  
Detailed Knowledge ◽  
Stress Distributions ◽  
Element Analysis ◽  
Plane Shear ◽  
Normal Contact

Abstract During vehicle braking and cornering, the tire's footprint region may see high normal contact pressures and in-plane shear stresses. The corresponding resultant forces and moments are transferred to the wheel. The optimal design of the tire bead area and the wheel requires a detailed knowledge of the contact pressure and shear stress distributions at the tire/rim interface. In this study, the forces and moments obtained from the simulation of a vehicle in stationary braking/cornering conditions are applied to a quasi-static braking/cornering tire finite element model. Detailed contact pressure and shear stress distributions at the tire/rim interface are computed for heavy braking and cornering maneuvers.

Determination of the transverse shear stress in layered composites

2020 ◽  
Vol 86 (2) ◽  
pp. 44-53
Author(s):  
Yu. I. Dudarkov ◽  
M. V. Limonin
Keyword(s):  
Shear Stress ◽  
Transverse Shear ◽  
Composite Beam ◽  
Layered Composite ◽  
Equivalent Model ◽  
Shear Stresses ◽  
Transverse Shear Stress ◽  
Layered Composites ◽  
Laminate Composites ◽  
Transverse Shear Stresses

An engineering approach to estimation of the transverse shear stresses in layered composites is developed. The technique is based on the well-known D. I. Zhuravsky equation for shear stresses in an isotropic beam upon transverse bending. In general, application of this equation to a composite beam is incorrect due to the heterogeneity of the composite structure. According to the proposed method, at the first stage of its implementation, a transition to the equivalent model of a homogeneous beam is made, for which the Zhuravsky formula is valid. The transition is carried out by changing the shape of the cross section of the beam, provided that the bending stiffness and generalized elastic modulus remain the same. The calculated shear stresses in the equivalent beam are then converted to the stress values in the original composite beam from the equilibrium condition. The main equations and definitions of the method as well as the analytical equation for estimation of the transverse shear stress in a composite beam are presented. The method is verified by comparing the analytical solution and the results of the numerical solution of the problem by finite element method (FEM). It is shown that laminate stacking sequence has a significant impact both on the character and on the value of the transverse shear stress distribution. The limits of the applicability of the developed technique attributed to the conditions of the validity of the hypothesis of straight normal are considered. It is noted that under this hypothesis the shear stresses do not depend on the layer shear modulus, which explains the absence of this parameter in the obtained equation. The classical theory of laminate composites is based on the similar assumptions, which gives ground to use this equation for an approximate estimation of the transverse shear stresses in in a layered composite package.

scholarly journals Assessing Machine Learning versus a Mathematical Model to Estimate the Transverse Shear Stress Distribution in a Rectangular Channel

Mathematics ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 596
Author(s):  
Babak Lashkar-Ara ◽  
Niloofar Kalantari ◽  
Zohreh Sheikh Khozani ◽  
Amir Mosavi
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Fuzzy Inference ◽  
Rectangular Channel ◽  
Tsallis Entropy ◽  
Shear Stress Distribution ◽  
Data Series ◽  
Shear Stresses ◽  
Inference System ◽  
Aspect Ratios

One of the most important subjects of hydraulic engineering is the reliable estimation of the transverse distribution in the rectangular channel of bed and wall shear stresses. This study makes use of the Tsallis entropy, genetic programming (GP) and adaptive neuro-fuzzy inference system (ANFIS) methods to assess the shear stress distribution (SSD) in the rectangular channel. To evaluate the results of the Tsallis entropy, GP and ANFIS models, laboratory observations were used in which shear stress was measured using an optimized Preston tube. This is then used to measure the SSD in various aspect ratios in the rectangular channel. To investigate the shear stress percentage, 10 data series with a total of 112 different data for were used. The results of the sensitivity analysis show that the most influential parameter for the SSD in smooth rectangular channel is the dimensionless parameter B/H, Where the transverse coordinate is B, and the flow depth is H. With the parameters (b/B), (B/H) for the bed and (z/H), (B/H) for the wall as inputs, the modeling of the GP was better than the other one. Based on the analysis, it can be concluded that the use of GP and ANFIS algorithms is more effective in estimating shear stress in smooth rectangular channels than the Tsallis entropy-based equations.

scholarly journals Studying dynamic stress effects on the behaviour of THP-1 cells by microfluidic channels

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Semra Zuhal Birol ◽  
Rana Fucucuoglu ◽  
Sertac Cadirci ◽  
Ayca Sayi-Yazgan ◽  
Levent Trabzon
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Vascular System ◽  
Circulatory System ◽  
Disease Process ◽  
Microfluidic Channels ◽  
Shear Stresses ◽  
Stress Effects ◽  
Adhesion Behavior ◽  
Cycling System

AbstractAtherosclerosis is a long-term disease process of the vascular system that is characterized by the formation of atherosclerotic plaques, which are inflammatory regions on medium and large-sized arteries. There are many factors contributing to plaque formation, such as changes in shear stress levels, rupture of endothelial cells, accumulation of lipids, and recruitment of leukocytes. Shear stress is one of the main factors that regulates the homeostasis of the circulatory system; therefore, sudden and chronic changes in shear stress may cause severe pathological conditions. In this study, microfluidic channels with cavitations were designed to mimic the shape of the atherosclerotic blood vessel, where the shear stress and pressure difference depend on design of the microchannels. Changes in the inflammatory-related molecules ICAM-1 and IL-8 were investigated in THP-1 cells in response to applied shear stresses in an continuous cycling system through microfluidic channels with periodic cavitations. ICAM-1 mRNA expression and IL-8 release were analyzed by qRT-PCR and ELISA, respectively. Additionally, the adhesion behavior of sheared THP-1 cells to endothelial cells was examined by fluorescence microscopy. The results showed that 15 Pa shear stress significantly increases expression of ICAM-1 gene and IL-8 release in THP-1 cells, whereas it decreases the adhesion between THP-1 cells and endothelial cells.

scholarly journals A Monotonic Smeared Truss Model to Predict the Envelope Shear Stress—Shear Strain Curve for Reinforced Concrete Panel Elements under Cyclic Shear

2021 ◽  
Vol 2 (1) ◽  
pp. 174-194
Author(s):  
Luís Bernardo ◽  
Saffana Sadieh
Keyword(s):  
Shear Stress ◽  
Reinforced Concrete ◽  
Shear Strain ◽  
Peak Load ◽  
Strain Curve ◽  
Fiber Reinforced Polymers ◽  
Shear Stresses ◽  
Cyclic Shear ◽  
Concrete Panels ◽  
Truss Model

In previous studies, a smeared truss model based on a refinement of the rotating-angle softened truss model (RA-STM) was proposed to predict the full response of structural concrete panel elements under in-plane monotonic loading. This model, called the “efficient RA-STM procedure”, was validated against the experimental results of reinforced and prestressed concrete panels, steel fiber concrete panels, and reinforced concrete panels externally strengthened with fiber-reinforced polymers. The model incorporates equilibrium and compatibility equations, as well as appropriate smeared constitutive laws of the materials. Besides, it incorporates an efficient algorithm for the calculation procedure to compute the solution points without using the classical trial-and-error technique, providing high numerical efficiency and stability. In this study, the efficient RA-STM procedure is adapted and checked against some experimental data related to reinforced concrete (RC) panels tested under in-plane cyclic shear until failure and found in the literature. Being a monotonic model, the predictions from the model are compared with the experimental envelopes of the hysteretic shear stress–shear strain loops. It is shown that the predictions for the shape (at least until the peak load is reached) and for key shear stresses (namely, cracking, yielding, and maximum shear stresses) of the envelope shear stress–shear strain curves are in reasonably good agreement with the experimental ones. From the obtained results, the efficient RA-STM procedure can be considered as a reliable model to predict some important features of the response of RC panels under cyclic shear, at least for a precheck analysis or predesign.

Field evidence of resuspension in a mine tailings pond

2001 ◽  
Vol 38 (4) ◽  
pp. 796-808 ◽  
Author(s):  
Celestina Adu-Wusu ◽  
Ernest K Yanful ◽  
Mohammed H Mian
Keyword(s):  
Shear Stress ◽  
Mine Tailings ◽  
Critical Shear Stress ◽  
Field Measurements ◽  
Shear Stresses ◽  
Wind Speeds ◽  
Tailings Pond ◽  
Field Evidence ◽  
Water Cover ◽  
Solubility Of Oxygen

Flooding of tailings under shallow water covers is an effective method of decommissioning potentially acid generating mine tailings. The low diffusivity and solubility of oxygen in water are attractive features of this technology. However, wind-induced waves can resuspend flooded tailings and expose them to greater contact with dissolved oxygen, thereby increasing the potential for oxidation and acid generation. Field measurements of wind activity and waves under different water cover depths and associated resuspension for a mine tailings pond in Ontario are presented and discussed. The results show that wind speeds greater than 8 m/s above water covers that are shallower than 1 m create waves of height greater than 10 cm and bottom shear stresses greater than 0.2 Pa. Under these conditions the critical shear stress of the mine tailings was exceeded, resulting in erosion and subsequent resuspension.Key words: mine tailings, water cover, wind-induced waves, resuspension, wind speed, shear stress.

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