Probabilistic Fault Displacement Hazard Analysis for North Tabriz Fault

The probabilistic fault displacement hazard analysis is one of the new methods in estimating the amount of possible displacement in the area at the hazard of causal fault rupture. In this study, using the probabilistic approach and earthquake method introduced by Youngs et al., 2003, the surface displacement of the North Tabriz fault has been investigated, and the possible displacement in different scenarios has been estimated. By considering the strike-slip mechanism of the North Tabriz fault and using the earthquake method, the probability of displacement due to surface ruptures caused by 1721 and 1780 North Tabriz fault earthquakes has been explored. These events were associated with 50 and 60 km of surface rupture, respectively. The 50–60 km long section of the North Tabriz fault was selected as the source of possible surface rupture. We considered two scenarios according to possible displacements, return periods, and magnitudes which are reported in paleoseismic studies of the North Tabriz fault. As the first scenario, possible displacement, return period, and magnitude was selected between zero to 4.5; 645 years and Mw~7.7, respectively. In the second scenario, possible displacement, return period and magnitude were selected between zero to 7.1, 300 years, and Mw~7.3, respectively. For both mentioned scenarios, the probabilistic displacements for the rate of exceedance 5 % in 50, 475, and 2475 years for the principle possible displacements (on fault) of the North Tabriz fault have been estimated. For the first and second scenarios, the maximum probabilistic displacement of the North Tabriz fault at a rate of 5 % in 50 years is estimated to be 186 and 230 cm. Also, mentioned displacements for 5 % exceedance in 475 years and 2475 years in both return periods of 645 and 300 years, are estimated at 469 and 655 cm.

Dislocation Topological Evolution and Energy Analysis in Misfit Hardening of Spherical Precipitate by the Parametric Dislocation Dynamics Simulation

Interaction of a single dislocation line and a misfit spherical precipitate has been simulated by the Parametric Dislocation Dynamics (PDD) method in this research. The internal stress inside the precipitate is deduced from Eshelby’s inclusion theory, the stress of the dislocation line and outside the precipitate is calculated by Green’s function. The influence of different relative heights of the primary slip plane on dislocation evolution is investigated, while the cross-slip mechanism and annihilation reaction are considered. The simulation results show three kinds of dislocation topological evolution: loop-forming (Orowan loop or prismatic loop), helix-forming, and gradual unpinning. The dislocation nodal force and the velocity vectors are visualized to study dislocation motion tendency. According to the stress–strain curve and the energy curves associated with the dislocation motion, the pinning stress level is strongly influenced by the topological change of dislocation as well as the relative heights of the primary slip plane.

Design of an Anti-Slip Mechanism for Wheels of Step Climbing Robots

This manuscript presents a shape memory alloy (SMA) actuated anti-slip mechanism for the wheels of step climbing robots. The proposed mechanism comprises three kinematic chains considering the Lazy Tong and the bi-stable four-bar mechanism. Chain 1 of the mechanism is used to clamp on the edges of the stairs to avoid slipping. The second chain of the mechanism is used to switch the mechanism between two stable positions, i.e., open position and closed position, of chain 1. For activating the mechanism, the third chain is employed which is based on SMA wire. Furthermore, the mechanism is designed to achieve passive switching from the open position to the closed position. Equations are developed to determine the dimensions of various members. Using those parameters, a 3D model of the proposed mechanism is developed. Stress analysis is performed and the model is found to be safe under a load of 250 N with a factor of safety of 3.025. The mechanism is attached to either side of a wheel of the outer radius of 290 mm. To analyze the kinematics of the mechanism, a three-dimensional model in MSC Adams is developed and studied. The force required by SMA actuator is found to be less than 5 N. The proposed mechanism may be used for various unmanned robotic systems while mitigating step-like obstacles in the path.

First Ever Offshore Deployment of an Inflatable Packer Anchoring System for Rigless Installation of an Insertable Progressive Cavity Pump: A Case Study

An offshore well located in Indonesia required rigless installation of an insertable progressive cavity pump (I-PCP) as a cost-effective solution to restore production while eliminating the need to retrieve the upper completion for extensive maintenance. The well had been previously completed with a conventional progressive cavity pump (PCP) as an integral part of the completion and was placed offline for approximately one year due to mechanical failure of downhole components. Typical I-PCP anchoring methods were not feasible alternatives for this application. A pump-seating nipple (PSN) insertable seal stack could not be used due to the lack of a PSN at the required I-PCP setting depth, and a mechanical J-slot anchoring device could not be deployed because rod conveyance from an offshore barge is subject to constant heave, which results in fluctuating axial loads and rod position, which would pose the risk of prematurely activating a mechanical J-slot anchor during deployment. An inflatable packer anchoring system was selected as a solution to the operational challenges encountered in this application. The system comprises inflatable packer technology, a hydraulically-actuated anchoring slip mechanism, seal cups, and a shearable intake sub. Conveyed on sucker rods, the system provides the required pressure competence to confirm tubing integrity and enable a complete hydraulic setting sequence. The first ever offshore installation of this system proved its optimal functionality by successfully anchoring an I-PCP inside 3-1/2" production tubing riglessly from an offshore barge. The system was set by applying pressure via the tubing-rod annulus, and the well was immediately placed into production. After being shut-in for more than one year, this unique solution provided the well operator with a safe and low-cost alternative to reestablish production while eliminating the need for a workover rig. The objective of this paper is to provide a case study analysis of the first offshore deployment of this technology, discuss its potential for optimizing PCP/I-PCP completion designs, and explain the economic and operational benefits of associated rigless well intervention operations in comparison to current alternative methods.

A comprehensive nonlinear finite element modelling and parametric analysis of reinforced concrete beams

Purpose This study aims to present comprehensive nonlinear material modelling techniques and simulations of reinforced concrete (RC) beams subjected to short-term monotonic static load using the robust and reliable general-purpose finite element (FE) software ANSYS. A parametric study is carried out to analyse the flexural and ductility behaviour of RC beams under various influencing parameters. Design/methodology/approach To develop and validate the numerical FE models, a total of four experimentally tested simply supported RC beams are taken from the available literature and two beams are selected from each author. The concrete, steel reinforcements, bond-slip mechanism, loading and supporting plates are modelled using SOLID65, LINK180, COMBIN39 and SOLID185 elements, respectively. The validated models are then used to conduct parametric FE analysis to investigate the effect of concrete compressive strength, percentage of tensile reinforcement, compression reinforcement ratio, transverse shear reinforcement, bond-slip mechanism, concrete compressive stress-strain constitutive models, beam symmetry and varying overall depth of beam on the ultimate load-carrying capacity and ductility behaviour of RC beams. Findings The developed three-dimensional FE models can able to capture the load and midspan deflections at critical points, the accurate yield point of steel reinforcements, the formation of initial and progressive concrete crack patterns and the complete load-deflection curves of RC beams up to ultimate failure. From the numerical results, it can be concluded that the FE model considering the bond-slip effect with Thorenfeldt’s concrete compressive stress-strain model exhibits a better correlation with the experimental data. Originality/value The ultimate load and deflection results of validated FE models show a maximum deviation of less than 10% and 15%, respectively, as compared to the experimental results. The developed model is also capable of capturing concrete failure modes accurately. Overall, the FE analysis results were found quite acceptable and compared well with the experimental data at all loading stages. It is suggested that the proposed FE model is a practical and reliable tool for analyzing the flexural behaviour of RC members and can be used for performing parametric studies.

Self-diffusion in nanofluids of nonelongated particles in the dilute limit

The dynamic features of a dilute suspension of nanoparticles (nanofluid) are fully modified depending on the dominant particles slip mechanism acting in the suspension. Self-diffusion effects in highly sheared diluted suspensions (entrance conditions and microapplications) can lead to a particles distribution fully different from the bulk one. The reported investigation proposes a model to determine the self-diffusion of three-planes symmetric nonelongated particles inmersed in a sheared Stokes flow. The model is based on the real displacements between any pair of particles and an statistical approach to determine contact kinematic irreversibilities. According to the proposed model, the source of hydrodynamic irreversibility is closely related to the particles shape. This is clearly demonstrated through the application of the model to cubic particles. The main conclusion is that the particles shape plays a significant role in the dynamic behavior of the suspension and, as a result, in the self-diffusion coefficient. The reported results arising from the cubic particles trajectories in a Stokes flow are reasonably close to the ones reported by Brady and Morris (J Fluid Mech, 348:103–139, 1997) for suspensions under high Pe number, and Zarraga and Leighton (Phys Fluids 13(3):565-577, 2001).