Papers by Dr. Aniket Patil
Compression and tensile strength properties are important input data for constitutive modelling. ... more Compression and tensile strength properties are important input data for constitutive modelling. Still strength properties of ridged ice are not yet sufficiently investigated. During winter 2011 an ...
Exploration and production of hydrocarbons in artic areas demands stronger, lighter and safer off... more Exploration and production of hydrocarbons in artic areas demands stronger, lighter and safer offshore structures. Wind and sea currents are responsible for ice loads on structure. The design of these structures is based on load level which is usually determined by the drift ice features i.e. ice ridges and surrounding level ice fields if icebergs are not dominating in the area. Ridges drift and hit fixed or moored surface structures such as platforms or ships, or they may scour the seabed endangering pipelines and wellheads. Realistic Constitutive models will help to build more accurate numerical analysis of the ice load. It will decrease the capital costs for the offshore structures, resulting in more economic field development for arctic offshore. This literature review paper is focused on existing models used to simulate the constitutive behavior of the ice rubble. In the first chapter of ridge types, their formation and typical geometrical features has been discussed. The secon...
Ocean Engineering
An attempt has been made to predict the ice rubble field load on Norströmsgrund lighthouse by usi... more An attempt has been made to predict the ice rubble field load on Norströmsgrund lighthouse by using Cohesive Element (CE) formulation. Two sub-load events were selected to validate the numerical and material model used in simulation of interaction of the ice rubble field and lighthouse. A literature review of simulation of rubble field structure interaction methods is also included in order to illustrate the knowledge gaps and highlight shortcomings of existing techniques. A description of chosen ice rubble field load events and signal post processing is added. A linear Mohr-Coulomb material model was used for the bulk element. For the cohesive element formulation, a material model was chosen which is based on three irreversible mixed-mode interaction with an arbitrary normalized traction-separation law governed by a load curve. The elastic modulus and fracture toughness for the ice rubble field were scaled using the ice rubble field porosity. A parametric study was conducted, and effects were documented. The numerical model predicted similar values for maximum total force, but average and standard deviation values of total force were higher than measured. The observed load drops in measured force time histories were reproduced with reasonable accuracy in simulated force time histories.
Journal of Cold Regions Engineering, 2021
The repeated passage of ships through an ice infested waters creates a field of broken ice pieces... more The repeated passage of ships through an ice infested waters creates a field of broken ice pieces. The typical size of the broken ice pieces is generally less than 2.0 m. This area may be referred as a brash ice field. The movement of ships and vessels leads to the 2 transportation and accumulation of broken ice pieces in brash ice field. A better understanding of the properties and behaviour of brash ice will improve the estimates of ice load associated with shipping in the brash-ice field. An in-situ test, referred here as "pull-up" test, was performed in the Luleå harbour. An attempt was made to estimate the mechanical and physical properties of brash ice field based on the in-situ test results. The test setup, procedure and test results are described in detail. Furthermore, the test is simulated using the Smoothed Particle Hydrodynamics (SPH) formulation. The purpose of the numerical simulations is to calibrate the numerical and material model of brash ice using the pull-up test measurements. In this numerical model, a discrete mass-spring-dashpot model was used to simulate buoyancy and drag. The continuous surface cap model (CSCM) was used as a material model for the brash ice. The elastic modulus and the fracture energy of brash ice as a material model input were estimated by an ad-hoc scaling formula. The parameters such as void fraction, cohesion and angle of internal friction were altered to see their influence with respect to the test data. The analysis of the in-situ test results and the simulation results provide a preliminary approach to understanding of the brash ice failure process which can be further developed into modelling techniques for marine design and operations.
An attempt has been made to calibrate the material model parameters of the continuous surface cap... more An attempt has been made to calibrate the material model parameters of the continuous surface cap model with data from punch through tests performed in the Northern Gulf of Bothnia. An axisymmetric ...
Friction processes of rubber on ice, steel on ice and ice on ice have been investigated by measur... more Friction processes of rubber on ice, steel on ice and ice on ice have been investigated by measuring contact forces in controlled laboratory experiments. A carefully prepared ice plate was rotated at a constant speed and brought into contact with a ring on which torque and normal load was measured. Replicas of the different types of standardized ice surfaces were studied in microscope. Friction of rubber on ice reached a maximum value at a sliding speed of abt. 100 mm/min. At a temperature of -10°C this maximum friction coefficient decreased with increasing ice surface roughness. Friction of steel on ice increased with decreasing speed and no maximum value was obtained. Ice sliding on ice at low speed resulted in high friction forces when sintering took place.
Ice rubble has highly nonlinear behavior and thus simulate shear properties requires sophisticate... more Ice rubble has highly nonlinear behavior and thus simulate shear properties requires sophisticated constitutive models including a relatively large number of parameters and complicated calibration procedures. An attempt has been made to simulate shear properties of ice rubble. A shear box experiment is chosen from test series performed by Fransson and Sandkvist (1985). In this paper a shear box test is simulated with nonlinear finite element code LS-Dyna. A newly implemented material model in LS-Dyna called continuous surface cap model (CSCM) has been used in this simulation. This model is proposed by Schwer and Murray (1994). For the sake of simplicity, experimental results are compared with Mohr-Coulomb material model. A brief overview of continuous surface cap model is given. Finally, comparisons with experimental results have been made.
Proceedings of the 21st International Conference on Port and Ocean Engineering under Arctic Conditions July 10-14, 2011 Montréal, Canada, 2011
Friction processes of rubber on ice, steel on ice and ice on ice have been investigated by measur... more Friction processes of rubber on ice, steel on ice and ice on ice have been investigated by measuring contact forces in controlled laboratory experiments. A carefully prepared ice plate was rotated at a constant speed and brought into contact with a ring on which torque and normal load was measured. Replicas of the different types of standardized ice surfaces were studied in microscope. Friction of rubber on ice reached a maximum value at a sliding speed of abt. 100 mm/min. At a temperature of-10°C this maximum friction coefficient decreased with increasing ice surface roughness. Friction of steel on ice increased with decreasing speed and no maximum value was obtained. Ice sliding on ice at low speed resulted in high friction forces when sintering took place.
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Papers by Dr. Aniket Patil