Constitutive relations between dynamic physical parameters near a tip of the propagating slip zone during stick-slip shear failure

1987 ◽  
Vol 144 (1-3) ◽  
pp. 109-125 ◽  
Author(s):  
Mitiyasu Ohnaka ◽  
Yasuto Kuwahara ◽  
Kiyohiko Yamamoto
Keyword(s):  
Shear Failure ◽  
Constitutive Relations ◽  
Slip Zone ◽  
Physical Parameters ◽  
Stick Slip

scholarly journals FEM Study of a Steel Corrugated Web Plate Girder Subjected to Fire

2021 ◽  
Vol 26 (2) ◽  
pp. 201-218
Author(s):  
D. Sokołowski ◽  
M. Kamiński
Keyword(s):  
High Strength Steel ◽  
Constitutive Relations ◽  
High Strength ◽  
Experimental Tests ◽  
Physical Parameters ◽  
Bottom Flange ◽  
Gas Temperature ◽  
Temperature Dependent ◽  
Corrugated Web ◽  
Plate Girder

Abstract The main aim of this work is a computational nonlinear analysis of a high strength steel corrugated-web plate girder with a very detailed and realistic mesh including vertical ribs, all the fillet welds and supporting areas. The analysis is carried out to verify mechanical structural response under transient fire temperature conditions accounting for an efficiency and accuracy of three various transient coupled thermo-elastic models. All the resulting stress distributions, deformation modes and their time variations, critical loads and eigenfrequencies as well as failure times are compared in all these models. Nonlinearities include material, geometrical and contact phenomena up to the temperature fluctuations together with temperature-dependent constitutive relations for high strength steel. They result partially from steady state and transient experimental tests or from the additional designing rules included in Eurocodes. A fire scenario includes an application of the normative fire gas temperature curve on the bottom flange of the entire girder for a period of 180 minutes. It is computed using sequentially coupled thermo-elastic Finite Element Method analyses. These account for heat conductivity, radiation and convection. The FEM model consists of a combination of 3D hexahedral and tetrahedral solid finite elements and uses temperature-dependent material and physical parameters, whose values are taken after the experiments presented in Eurocodes. Numerical results presented here demonstrate a fundamental role of the lower flange in carrying fire loads according to this scenario and show a contribution of the ribs and of the welds to the strength of the entire structure.

scholarly journals Investigations of Coal-Rock Parting-Coal Structure (CRCS) Slip and Instability by Excavation

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Guang-Jian Liu ◽  
Heng Zhang ◽  
Ya-Wei Zhu ◽  
Wen-Hao Cao ◽  
Xian-Jun Ji ◽  
...  
Keyword(s):  
Shear Failure ◽  
P Wave ◽  
Shear Behaviour ◽  
Failure Zone ◽  
Stick Slip ◽  
Coal Structure ◽  
P Wave Velocity ◽  
Splitting Failure ◽  
Shear And Tensile Cracks ◽  
Coal Rock

Slip and instability of coal-rock parting-coal structure (CRCS) subjected to excavation disturbance can easily induce coal-rock dynamic phenomena in deep coal mines. In this paper, the failure characteristics and influencing factors of CRCS slip and instability were investigated by theoretical analysis, numerical simulations, and field observations. The following main results are addressed: (1) the slip and instability of CRCS induced by excavation are due to stress release, and the damage of the rock parting is partitioned into three parts: shear failure zone, slipping zone, and splitting failure zone from inside to outside with slip; (2) the slip and instability process of CRCS is accompanied by initiation, expansion, and intersection of shear and tensile cracks. The development of the cracks is dominated by shear behaviour, while the tensile crack is the main factor affecting fracture and instability of CRCS; and (3) slip and instability of CRCS are characterized by stick-slip first and then stable slip, accompanied with high P-wave velocity and rockburst danger coefficient based on microseismic tomography.

Oxidative weathering deterioration of black shale and its bedding shear failure modeling

2021 ◽  
Author(s):  
Chunwei Sun ◽  
Marc-Henri Derron ◽  
Michel Jaboyedoff ◽  
Xiyong Wu
Keyword(s):  
Black Shale ◽  
Chemical Weathering ◽  
Shear Failure ◽  
Theoretical Models ◽  
Slip Zone ◽  
Iron Sulfate ◽  
Failure Modeling ◽  
Rock Structure ◽  
Degradation Models ◽  
Deterioration Mechanism

<p>This work investigated the oxidative weathering deterioration of black shale along a bedding slip zone and how it affects the bedding shear failure in the Xujiaping landslide, southern Sichuan Province in China. Many dissolved pits were found on the limestone, and part of the black shale in the slip zone is mud-like and clastic, showing local shear failure, which can be one of the main reasons of slope instabiliy. The microstructure of black shale under oxidative weathering condition was observed by scaning electron microscopy (SEM), characterized by dissolved pores, weathering crust (iron sulfate) of pyrite crystals, and the filling gypsum crystal in the bedding foliation. The deterioration mechanism was expanded: (i) rock-forming and carbonate minerals were especially prone to dissolution by sulfuric acid from black shale oxidation in the slip zone, and (ii) volume expansion due to the crystallization force of precipitated minerals caused further fracture expansion and deformation. Therefore, two theoretical models were developed that use stoichiometric calculations of pyrite and calcite to determine the dissolution rate and the rock structure after chemical weathering; and establish a rock structure model characterized by foliation weakening of gypsum crystallization. In order to analyze the landslide failure, discrete element method (DEM) is used to analyze the black shale shear failure mechanism of the two degradation models after oxidative weathering. It will be useful to better understand how these oxidative weathering deterioration contribute to bedding shear failure in natural hazards.</p>

scholarly journals Suppression of drill-string stick–slip vibration by sliding mode control: Numerical and experimental studies

2018 ◽  
Vol 29 (5) ◽  
pp. 805-825 ◽  
Author(s):  
VAHID VAZIRI ◽  
MARCIN KAPITANIAK ◽  
MARIAN WIERCIGROCH
Keyword(s):  
Mathematical Model ◽  
Sliding Mode Control ◽  
Close Agreement ◽  
Sliding Mode ◽  
Drill String ◽  
Numerical Results ◽  
Physical Parameters ◽  
Parameter Uncertainties ◽  
Stick Slip ◽  
Mode Control

We investigate experimentally and numerically suppression of drill-string torsional vibration while drilling by using a sliding mode control. The experiments are conducted on the novel experimental drill-string dynamics rig developed at the University of Aberdeen (Wiercigroch, M., 2010, Modelling and Analysis of BHA and Drill-string Vibrations) and using commercial Polycrystalline Diamond Compact (PDC) drill-bits and rock-samples. A mathematical model of the experimental setup, which takes into account the dynamics of the drill-string and the driving motor, is constructed. Physical parameters of the experimental rig are identified in order to calibrate the mathematical model and consequently to ensure robust predictions and a close agreement between experimental and numerical results for stick–slip vibration is shown. Then, a sliding mode control method is employed to suppress stick–slip vibration. A special attention is paid to prove the Lyapunov stability of the controller in presence of model parameter uncertainties by defining a robust Lyapunov function. Again experimental and numerical results for the control cases are in a close agreement. Stick–slip vibration is eliminated and a significant reduction in vibration amplitude has been observed when using the sliding controller.

scholarly journals Multi-degree-of-freedom systems with a Coulomb friction contact: analytical boundaries of motion regimes

2021 ◽  
Author(s):  
Luca Marino ◽  
Alice Cicirello
Keyword(s):  
Ad Hoc ◽  
Harmonic Excitation ◽  
Degree Of Freedom ◽  
Physical Parameters ◽  
Dimensional Parameter ◽  
Stick Slip ◽  
State Response ◽  
Mdof Systems ◽  
Two Degree Of Freedom

AbstractThis paper proposes an approach for the determination of the analytical boundaries of continuous, stick-slip and no motion regimes for the steady-state response of a multi-degree-of-freedom (MDOF) system with a single Coulomb contact to harmonic excitation. While these boundaries have been previously investigated for single-degree-of-freedom (SDOF) systems, they are mostly unexplored for MDOF systems. Closed-form expressions of the boundaries of motion regimes are derived and validated numerically for two-degree-of-freedom (2DOF) systems. Different configurations are observed by changing the mass in contact and by connecting the rubbing wall to: (i) the ground, (ii) the base or (iii) the other mass. A procedure for extending these results to systems with more than 2DOFs is also proposed for (i)–(ii) and validated numerically in the case of a 5DOF system with a ground-fixed contact. The boundary between continuous and stick-slip regimes is obtained as an extension of Den Hartog’s formulation for SDOF systems with Coulomb damping (Trans Am Soc Mech Eng 53: 107–115, 1931). The boundary between motion and no motion regimes is derived with an ad hoc procedure, based on the comparison between the overall dynamic load and the friction force acting on the mass in contact. The boundaries are finally represented in a two-dimensional parameter space, showing that the shape and the extension of the regions associated with the three motion regimes can change significantly when different physical parameters and contact configurations are considered.

Mechanisms of Microstructural Rearrangement on Two-Dimensional Aggregates under Compressive Stress

2011 ◽  
Vol 312-315 ◽  
pp. 682-687 ◽  
Author(s):  
Sarunya Promkotra
Keyword(s):  
Large Scale ◽  
Shear Failure ◽  
Elastic Stress ◽  
Tensile Failure ◽  
Small Scale ◽  
Two Dimensional ◽  
Stick Slip ◽  
Elastic And Plastic Deformations ◽  
Elastic Loading ◽  
Air Liquid Interface

Two-dimensional (2D) colloidal aggregates of polystyrene microspheres 4 μm were experimentally modeled to study the rearranged mechanisms and compression behaviors at the air-liquid interface. The aggregated models occurred due to the interaction forces between particles. The combination of mechanical testing technique and the digital video microscopy had been developed to quantitatively analyze the compressive deformation of 2D aggregates. When the compressive forces were applied to the cluster, these forces were transmitted trough the aggregated network during compression. Solid-like mechanical properties of 2D aggregated cluster were examined. Deformation mechanisms occurred within the aggregated network which presented the particle rearrangements during yield. Elastic deformation had undergone the compressive elastic stress of the elastic loading. Rearrangement mechanisms found generally were rolling-hinge, sliding mechanisms and tensile failure for a small-scale deformation. Shear failure and stick-slip mechanisms caused a large-scale plastic deformation. However, across the yield point, the tensile failures were dominated. Rearrangement mechanisms of particles affected both elastic and plastic deformations.

On Constitutive Relations for Friction From Thermodynamics and Dynamics

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Michael D. Bryant
Keyword(s):  
Friction Coefficient ◽  
Entropy Production ◽  
Internal Energy ◽  
Coefficient Of Friction ◽  
Slip Velocity ◽  
Constitutive Relations ◽  
Thermodynamic Quantities ◽  
Stick Slip ◽  
Friction Forces ◽  
Kinetic Coefficients

Constitutive and dynamic relations for friction coefficient are presented. A first thrust combines the laws of thermodynamics to relate heat, energy, matter, entropy, and work of forces. The equation sums multiple terms—each with a differential of a variable multiplied by a coefficient—to zero. Thermodynamic considerations suggest that two variables, internal energy and entropy production, must depend on the others. Linear independence of differentials renders equations that yield thermodynamic quantities, properties, and forces as functions of internal energy and entropy production. When applied to a tribocontrol volume, constitutive laws for normal and friction forces, and coefficient of friction are derived and specialized for static and kinetic coefficients of friction. A second thrust formulates dynamics of sliding, with friction coefficient and slip velocity as state variables. Differential equations derived via Newton's laws for velocity and the degradation entropy generation (DEG) theorem for friction coefficient model changes to the sliding interface induced by friction dissipation. The solution suggests that the transition from static to kinetic coefficient of friction with respect to slip velocity for lubricant starved sliding is a property of the motion dynamics of sliding interacting with the dynamics of change of the surface morphology. Finally, sliding with stick-slip was simulated to compare this model to others.

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