Explicit integration scheme for a non-isothermal elastoplastic model with convex and nonconvex subloading surfaces

2015 ◽  
Vol 55 (5) ◽  
pp. 943-961 ◽  
Author(s):  
Annan Zhou ◽  
Yue Zhang
Keyword(s):  
Integration Scheme ◽  
Elastoplastic Model ◽  
Explicit Integration

Asymmetric FPSO Roll Response due to the Influence of Lines Arrangement

2012 ◽  
Author(s):  
Marcos Donato Ferreira ◽  
Mauro Costa de Oliveira ◽  
Rafaella Cristina Carvalho ◽  
Sergio Hamilton Sphaier
Keyword(s):  
Integration Scheme ◽  
Impulse Response Functions ◽  
Viscous Effects ◽  
Lumped Mass ◽  
Explicit Integration ◽  
Deep Waters ◽  
Campos Basin ◽  
Motion Responses ◽  
Non Linear ◽  
Ship Hydrodynamic

In the development of the mooring design of FPSOs in spread mooring system (SMS) configuration, it was observed that the utilization of asymmetric riser arrangement in deep waters might lead to an asymmetrical roll response of the FPSO. In particular, concentrating all riser connections on the portside, it could be observed that roll and heave coupling under the influence of the riser dynamics might lead to a much lower roll response associated with waves coming from portside than from the starboard direction. Simulations were carried using an in-house time domain simulator, where the ship hydrodynamic behavior was represented through the use of impulse response functions and the lines dynamic through the use of non-linear finite element method, using an explicit integration scheme and a lumped mass approach. Non-linear viscous effects could be easily associated to the ship and line velocities. Measured motion responses of an actual FPSO in operation in Campos Basin are compared with the computations.

3D Elastic Deformable Object Model for Robot Manipulation Purposes

2014 ◽  
Vol 18 (3) ◽  
pp. 375-382 ◽  
Author(s):  
Khairul Salleh Mohamed Sahari ◽  
◽  
Yew Cheong Hou
Keyword(s):  
The State ◽  
Service Robots ◽  
Robotic Arm ◽  
Service Robot ◽  
Integration Scheme ◽  
Explicit Integration ◽  
Robot Manipulation ◽  
Deformable Object ◽  
Home Service ◽  
Mass Spring

This paper presents a mass-spring model applied to the manipulation of an elastic deformable object for home service robot application. A system is also proposed that is used to fold a piece of rectangular cloth from a specific initial condition using a robot. The cloth is modeled as a three-dimensional object in a two-dimensional quadrangular mesh based on a massspring system, and its state is estimated using an explicit integration scheme that computes the particle position as a function of the internal and external forces acting on the elastic deformable object. The current state of the elastic deformable object under robot manipulation is tracked based on the trajectory of the mass points in the mass-spring system model in a self-developed simulator, which integrates a massspring model and a five-degree-of-freedom articulated robotic arm. To test the reliability of the model, the simulator is used to predict the best possible paths for using the robotic arm to fold a rectangular cloth into two. In the test, the state of the object is derived from the model and then compared with the results of a practical experiment. Based on the test, the error is found to be generally acceptable. Thus, this model can be used as an estimator for the vision-based tracking of the state of an elastic deformable object for manipulation by home service robots.

scholarly journals Three-Dimensional Explicit Finite Element Simulation of Piled-Raft Foundation

2020 ◽  
Vol 26 (3) ◽  
pp. 127-144
Author(s):  
Huda Hussien Ahmed ◽  
Salah R. Al-Zaidee
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Experimental Work ◽  
Element Model ◽  
Integration Scheme ◽  
Explicit Integration ◽  
Element Analysis ◽  
Piled Raft ◽  
Piled Raft Foundation ◽  
Raft Foundation

This paper aims to validate a proposed finite element model to be adopted in predicting displacement and soil stresses of a piled-raft foundation. The proposed model adopts the solid element to simulate the raft, piles, and soil mass. An explicit integration scheme has been used to simulate nonlinear static aspects of the piled-raft foundation and to avoid the computational difficulties associated with the implicit finite element analysis. The validation process is based on comparing the results of the proposed finite element model with those of a scaled-down experimental work achieved by other researchers. Centrifuge apparatus has been used in the experimental work to generate the required stresses to simulate the actual geostatic stress on the site. Comparing between numerical and experimental results indicate that the proposed finite element model is accurate and adequate and it can be used in future work to simulate more complicated practical problems of piled-raft foundations. After its validation, this model was used to investigate the effectiveness of using piled with a raft foundation that subjected to eccentric loading. In this parametric study, the value of eccentricity  was taken equal to , , and . The numerical results indicated that there is a significant decrease in the bearing capacity for unpiled raft foundation compared to the piled raft foundation for the same eccentricity of the applied load.  

scholarly journals Stochastic Lattice Modelling of the Force-Displacement and Cracking Behaviour of the Steel Reinforced Tie

2019 ◽  
Vol 2019 ◽  
pp. 1-17
Author(s):  
Darius Zabulionis ◽  
Ona Lukoševičienė ◽  
Rimantas Kačianauskas ◽  
Liudas Tumonis ◽  
Romualdas Kliukas
Keyword(s):  
Stochastic Process ◽  
Tensile Force ◽  
Gaussian Random Field ◽  
Integration Scheme ◽  
P Value ◽  
Three Dimension ◽  
Two Dimensional ◽  
Explicit Integration ◽  
Deterministic Models ◽  
Force Displacement

The stochastic modelling of the microcracking and the force-displacement behaviour of the tensile steel reinforced tie using the lattice model is presented in the current article. The three-dimension problem of the modelling of the tie is reduced to the two-dimensional so as the main stiffness parameters of the concrete and the reinforcement of the two-dimensional model would be the same as for the three-dimensional. The concrete and steel obey the Hook law. All elastic constants, as well as dimensions of the tie, were assumed as the deterministic quantities except for the critical concrete tensile strains which were treated as a two-dimensional stationary uncorrelated truncated Gaussian random field. The discrete element approach and the explicit integration scheme have been used for the modelling. The estimations of the main parameters of the force-displacement behaviour stochastic process and other statistical indexes were obtained using 72 realization of the force-displacement behaviour of a chosen model. Extra two stochastic realizations of the two different models, as well as three deterministic models, were modelled to compare stochastic and deterministic behaviour of the force-displacement behaviour. The analysis showed that the force-displacement behaviour of the tie under tensile force cannot be treated as a Gaussian stochastic process when the p value is 0.05 at the small displacements and within the interval when the cracking of the concrete is very intensive. However, at the bigger displacements, when the cracking becomes less intensive, the tensile force can be treated as a Gaussian random variable.

Stress Analysis of Variable Ram Blowout Prevention Valves

2021 ◽  
pp. 1-11
Author(s):  
Ajit Achuthan ◽  
Shiyan Jayanath
Keyword(s):  
Finite Element ◽  
Elevated Temperatures ◽  
Performance Criteria ◽  
Integration Scheme ◽  
Material Failure ◽  
Analysis Model ◽  
Explicit Integration ◽  
Element Analysis ◽  
Wellbore Pressure ◽  
Sealing Pressure

Summary Variable ram blowout prevention (VRBOP) valves are elastomeric material-based flow control devices used in offshore oil drilling applications as the primary safety mechanism to respond to high wellbore pressure emergency situations. During their operation, the elastomer deforms and distorts extensively to form a tight seal around the drillpipe. Because of the large deformation and distortion of the elastomer, developing a Lagrangian-based finite element analysis model to simulate the operation of a VRBOP valve is quite challenging. The finite elements of the Lagrangian finite element mesh degrade in quality because they deform with the material when the deformation becomes excessive. This leads to poor convergence of the numerical solution. In this study, we first demonstrate that the numerical convergence issues can be resolved by using a suite of modeling techniques: explicit integration scheme, Ogden second-order hyperelastic constitutive model for the elastomer, and the selection of appropriate values for element sizes and other modeling parameters. After resolving the convergence issues, we used the model to study the sealing efficiency and material failure of a VRBOP valve for two different operating temperatures and drillpipe diameters. The sealing efficiency is studied using two performance criteria: the uniformity of the sealing pressure around the drillpipe and the magnitude of the overall deformation of the elastomer. For the material failure analysis of the elastomer, we used multiple failure criteria. The results of this study provide many new insights that have the potential to improve VRBOP valve design. For instance, results show that elevated temperature improves the sealing efficiency of a VRBOP valve because of the higher flexibility of the elastomer at elevated temperatures. Likewise, the wellbore pressure also improves the sealing efficiency. However, all these improvements in sealing pressure come with the risk of a higher probability of material failure.

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