Ice Failure Research Articles

Microstructure-sensitive crystal plasticity and phase-field modeling of deformation and fracture in polycrystalline ice

The formation of crevasses in Greenland and Antarctica is primarily driven by the brittle failure of ice at low strain rates. Understanding this phenomenon requires exploring the effect of microstructural heterogeneity and anisotropic elastoplastic deformation on the fracture behavior of ice. Here, we have developed a microstructure-sensitive coupled crystal plasticity and phase-field model. This model allows us to study the plastic deformation, damage initiation and propagation under various strain rates in hexagonal open-packed polycrystalline ice, the prevailing phase on Earth. By employing a Bayesian optimization method, we derived the material parameters for the micromechanical model based on experimental results. The modeling results reveal that the activation of basal dislocations results in a brittle to ductile transition in ice at a low strain rate of 10-7s-1 under tension. At higher strain rates, the intrinsic plastic anisotropy of ice leads to heterogeneous deformation among grains and stress concentration near grain boundaries, triggering crack initiation and exacerbating the brittleness of ice. Under compression, cracks usually do not propagate throughout the specimen due to a significant decrease in stress around the crack tip upon propagation. Moreover, we found that the formation of the shear-induced basal texture at the bottom of ice layers and along glacier valley sides intensifies the brittleness of ice. This study provides insights into the micromechanical deformation and fracture mechanisms of ice, elucidating the intricate process of crevasse development in polar ice sheets.

Constraining Ocean and Ice Shell Thickness on Miranda from Surface Geological Structures and Stress Modeling

Images from the Voyager 2 mission revealed the small Uranian satellite Miranda to be a complex, dynamic world. This is exemplified by signs of recent geological activity, including an extensive fault system and the mysterious coronae. This has led to speculation that Miranda may have been tectonically active within the geologically recent past and could have hosted a subsurface liquid water ocean at the time. In this work, we aim to constrain the thickness ranges for the ice shell and potential subsurface ocean on Miranda. Here, we present the results for our geological mapping of craters, ridges, and furrows on the surface. We also present the results for our comparison of the geographic distribution of these features to the predicted geographic distribution of maximum tidal stress based on stress models. We model eccentricity tidal stress, ice shell thickening stress, true polar wander stress, and obliquity tidal stress and compare the predicted surface stress pattern for each to what pattern can be inferred from the surface geology. Our results show that a thin crust (≤30 km) is most likely to result in sufficient stress magnitude to cause brittle failure of ice on Miranda’s surface. Our results also suggest the plausible existence of a ≥100 km thick ocean on Miranda within the last 100–500 million yr. This has implications for the dynamical history of Miranda and its status as a potential ocean world.

Research into mechanical modeling based on characteristics of the fracture mechanics of ice cutting for scientific drilling in polar regions

Abstract. Scientific drilling in polar regions plays a crucial role in obtaining ice cores and using them to understand climate change and to study the dynamics of polar ice sheets and their impact on global environmental changes (sea level, ocean current cycle, atmospheric circulation, etc.). Mechanical rotary cutting is a widely used drilling method that drives the cutter to rotate to cut and drill through ice layers. It is necessary to conduct in-depth research on the brittle fracture behavior of ice and mechanical model and to analyze the factors and specific mechanisms (cutter's angle, rotation speed of the drill bit, and cutting depth) affecting cutting force for the rational design of ice core drill systems, improving the efficiency of ice core drilling and ensuring the drilling process runs smoothly. Therefore, in this paper, the process of ice cutting was observed, the fracture mechanics characteristics of the ice cutting process were analyzed, the formation process of ice chips was divided into three stages, and a mathematical model for the cutting force was established based on the observation results. The paper describes the damage conditions of ice failure and points out the factors and specific laws influencing cutting force. Furthermore, the cutting force generated under various experimental conditions was tested. Based on specified real-time variation curves of cutting force, the characteristics of cutting force were analyzed during the cutting and drilling process. Based on comparison to results of the average cutting force, the influence mechanism of various parameters acting on the cutting force was obtained. This proves the correctness of the mathematical model of the cutting force and provides a theoretical reference for the calculation of the cutting force during ice cutting and drilling in polar regions.

Numerical Simulation of Extreme Ice Loads on Complex Pile Legs of Offshore Substation Structures

The sea ice failure mode and ice force amplitude depend on the structural form at the point of interaction, but the impacts of ice load when interacting with marine engineering structures with additional attachments are not yet clear. This study conducts numerical simulations using the discrete element method to investigate the interaction between sea ice and cable pipes attached to offshore substation structures. Various operating conditions such as ice velocity, ice thickness, and ice attack angle are selected to simulate the interaction between sea ice and such structures, clarifying the variations in the sea ice failure mode and ice force amplitude. The results indicate that crushing failure mainly occurs when sea ice interacts with such structures, and the presence of cable pipes does not alter the sea ice failure mode at the legs of offshore substation structures. The preliminary action of sea ice with cable pipes effectively reduces the ice load on the structure, and the minimum ice force amplitude occurs at an ice attack angle of 90°, with the ice force amplitude increasing with the ice thickness but showing no clear correlation with the ice velocity. The findings of this study provide a reference for the ice-resistant design of offshore substation structures in cold regions.

The Dynamic Failure Behaviour of High-Pressure Zones during Medium-Scale Ice Indentation Tests

Results from medium-scale ice-crushing dynamic tests are presented in this paper based on a series of indentation experiments on confined ice samples using spherical indenters to simulate high-pressure zones (hpzs) with areas on the order of 103–104 mm2. The effects of ice temperature, interaction speed, indenter size and structural compliance on failure behaviour and associated structural dynamics have been studied. Observed failure behaviour consisted of a combination of continuous crushing extrusion and intermittent spalling, both of which were highly dependent on test conditions. Overall, the effects of the studied conditions on ice failure behaviour and associated interaction dynamics were found to be similar to the results reported from previous small-scale experiments, suggesting scale independence of the mechanisms that dominate ice failure behaviour. In general, warmer ice and smaller contact areas are associated with continuous extrusion with intermittent spalling, resulting in smoother peak pressures, while colder ice and larger contact areas tend to result in fracture-dominated behaviour with sharp peaks and substantial load drops. Ice temperature was also found to significantly influence interaction dynamics, with colder ice showing larger amplitude and longer duration dynamic activity, and higher peak pressures. Interaction speed was observed to primarily affect dynamic aspects of ice–structure interactions, with faster tests leading to higher failure frequencies. Similarly, structural compliance was found to mainly impact failure frequency, as well as the extent of load drops, with compliant structures tending to produce more significant load drops following failure. Overall, these experiments have helped enhance our understanding of compressive ice failure and contribute to improved models for dynamic ice–structure interactions.

Discrete Element Analysis of Ice-Induced Vibrations of Offshore Wind Turbines in Level Ice

Self-excited vibrations of offshore structures interacting with sea ice, characterized by low frequency and high amplitudes, pose significant hazards to offshore wind turbines (OWTs) in cold seas. This study employs the discrete element method (DEM) with a parallel bonding model to investigate the interaction between sea ice and OWTs. Two bond-failure models are compared, with the results showing that the model considering stiffness softening and fracture energy provides better alignment with field data in the Bohai Sea. The DEM is employed to analyze the ice-induced vibration of OWTs under varying ice velocities, revealing that brittle failure of sea ice occurs at higher ice speeds, leading to random structure vibration. At slower ice speeds, both brittle and ductile sea ice failure modes result in self-excited vibrations. This suggests a strong connection between self-excited vibration and the brittle-ductile failure of sea ice, influenced by the relative speeds between ice and the structure. This study employs the DEM to elucidate the mechanism of self-excited vibrations in OWTs from the perspective of brittle-ductile sea ice failure. The results show that the DEM model accurately describes the brittle-ductile transition in sea ice failure, and that the structural motion aligns well with field measurements.

Effects of polypropylene and basalt fibers on tensile and compressive mechanical properties of fiber-reinforced ice composites

As an environmentally friendly and low-cost construction material, ice has a rich historical usage and has been gaining significance in cold-zone engineering constructions. However, the low tensile strength and brittle damage characteristics limit the potential applications of ice. Incorporating fibers in ice has been recognized as an effective method to improve the mechanical properties. This research aims to investigate the effects of polypropylene fibers (PF) and basalt fibers (BF) on the mechanical properties of fiber-reinforced ice composites. To do so, approximately 200 PF- and/or BF-reinforced ice specimens with varying fiber contents (0 %, 2 %, 4 %, 6 %, 8 %) were produced and subjected to splitting tensile and uniaxial compressive tests at −10 °C. Besides, the synergistic effect of hybrid fiber-reinforced ice on tensile mechanical properties was further investigated. The experimental results demonstrate that the addition of fibers transforms the brittle failure of ice into ductile failure, and both BF and PF improve the tensile and compressive mechanical properties of ice composites in strength and ductility as functions of fiber contents. The tensile mechanical properties of hybrid fiber-reinforced ice exhibit both negative and positive synergistic effects. Furthermore, the research established the tensile and compressive strength formulas of PF- or BF-reinforced ice composites with different fiber contents, and the calculated results correlated well with the tested ones.

A Multi-Yield-Surface Plasticity State-Based Peridynamics Model and its Applications to Simulations of Ice-Structure Interactions

Due to complex mesoscopic and the distinct macroscopic evolution characteristics of ice, especially for its brittle-to-ductile transition in dynamic response, it is still a challenging task to build an accurate ice constitutive model to predict ice loads during ship-ice collision. To address this, we incorporate the conventional multi-yield-surface plasticity model with the state-based peridynamics to simulate the stress and crack formation of ice under impact. Additionally, we take into account of the effects of inhomogeneous temperature distribution, strain rate, and pressure sensitivity. By doing so, we can successfully predict material failure of isotropic freshwater ice,iceberg ice, and columnar saline ice. Particularly, the proposed ice constitutive model is validated through several benchmark tests, and proved its applicability to model ice fragmentation under impacts, including drop tower tests and ballistic problems. Our results show that the proposed approach provides good computational performance to simulate ship-ice collision.

An example of numerical ice tank based on DEM simulation and physical model testing

The determination of ice loads on polar ships and offshore structures is of great significance for ice-resistant design, safe operation, and structural integrity management in ice-infested waters. The physical model testing carried out in ice tank/basin is usually an important technical approach to evaluate the ice loads, however, the high cost and time consumption make it difficult to perform multiple repetitions or large number of trials for this purpose. Recently, the rapid development of high-performance computation techniques provides a usable alternative where the numerical methods represented by the discrete element method (DEM) have made remarkable contributions to the ice load predictions. On basis of DEM simulation validated by physical model testing, numerical ice tank can be developed as an effective supplement to its counterpart. In this paper, such an example of numerical ice tank adopting GPU computational mechanism and DEM modelling algorithm was established with respect to the small ice model basin of China Ship Scientific Research Center (CSSRC-SIMB). The numerical ice tank was calibrated and further optimized with physical model tests on typical structures of vertical cylinder and inclined flat plate in level ice sheets by making agreements of both globe value and time history of the ice loads. Then it was practiced for modelling the tests of Wass bow advancing in level ice performed in SIMB separately. It is demonstrated by the comparisons of ice failure details and ice loads that the numerical ice tank can precisely simulate the ice-structure interactions and determine the ice loads under the same initial conditions of physical model testing. In the end, the advantages as well as the challenges of the numerical ice tank are discussed.

Propeller-Ice Contact modelling with Peridynamics

Ice loads pose a significant threat to ice-class propellers in frozen waters, making it crucial to analyse the magnitude of ice loads. However, the complex mechanical properties of ice and its failure process make it challenging to investigate the correlation between ice-propeller contact phenomena and ice loads. This paper uses a PC3 class propeller blade to study the propeller-ice contact process. This study involves developing ice failure and propeller blade models based on ordinary and non-ordinary state-based peridynamics theory and validating them using experimental. Convergence analysis was performed before blade ice loads evaluation. Additionally, we investigate the effect of the pitch angle on the ice-milling process.

An efficient computational framework for hailstone impacts on composite plates utilizing a semi-empirical viscoplastic contact law

The dynamic response of composite structures under impact loading conditions is a complex problem which is attracting substantial attention. Specifically, the case of hailstone impact introduces additional challenges that are urging to be encountered. Hence, the main goal of this paper is to present the development and validation of a computationally efficient impact model that encompasses a novel semi-empirical viscoplastic contact law for crushable ice impactors together with a new time domain spectral shear plate finite element formulation including nonlinear effects due to large displacements and rotations. The new viscoplastic contact law, which provides the coupling between the hailstone impactor and the targeted composite plate, is derived from analytical expressions and observations based on experiments and high-fidelity finite element simulations which utilize a fully integrated ice failure material model. High-velocity spherical hailstone impact experiments on woven glass/epoxy composite plate target structures are conducted using a high pressure pre-charged gas gun Obtained results are validated against high fidelity finite element models and experimental measurements. The results demonstrate the adequacy of the proposed contact law to capture the impact loading, as well as the accuracy, computational efficiency and additional benefits of the presented computational framework compared to other well-established numerical tools.

Mechanism of Phase-Locked Ice Crushing against Offshore Structures

This paper addresses a detailed analysis of the ice–structure interaction process of the phase-locked ice crushing (PLC) against offshore structures. Directly measured ice load, structure response data, and in situ observation from the field measurements on the Molikpaq lighthouse and jacket platform were used in the study. This paper summarizes a new ductile damage-collapse (DDC) failure mechanism for the PLC process. The DDC mechanism shows that the ice failure is a discrete ductile crushing process rather than a ductile–brittle transition process. The analysis identifies that the ice has a failure length in PLC and this failure length plays an important role in understanding the interaction. It reveals that PLC can occur on most vertical-sided offshore structures when the velocity of the ice sheet falls within the range of the failure length divided by the natural period of the structure. This paper proposes that this relationship between ice failure length and the natural period of the structure can be used as one of the PLC occurrence conditions. The DDC failure mechanism provides a basis for another technical route to solve the PLC problem.

Microphone recording of flexural waves for estimation of lake ice thickness

In this study we took an intentionally low-tech approach, aiming to estimate key physical parameters of lake ice using a single, inexpensive microphone. We consider this approach highly relevant to the issue of transport safety and the relatively high number of accidents involving breakthrough failure of thin ice underlines the importance of this topic. We conducted a range of experiments on three frozen lakes in the Tromsø region of Northern Norway and found that the monochromatic air-coupled flexural wave was a robust feature of impulsively excited frozen lakes. Ice thickness was estimated via a closed form solution that only depends on the measured monochromatic frequency of the air-coupled flexural wave and a set of assumed physical parameters for the ice, air and water. We discuss the impact of uncertainty in the assumed parameters on estimated ice thickness and bearing capacity, finding the uncertainty to be quite small, particularly when physical observation of ice type or drilled thickness are available to constrain the assumed Young's modulus of the ice. Ice thicknesses estimated from air-coupled flexural waves were typically within 5–10% of ice thickness measured in holes drilled in the vicinity of the microphone for both artificial sources including hammer strikes, jumping and tapping with ice skates and natural ice quakes. The thickness estimates were also similarly accurate whether the microphone was resting on the ice, placed on land along the shoreline or handheld. We also showed that it is possible to record the dispersive ice flexural wave using a microphone, particularly when it was resting on the ice surface. Since thickness was constrained by the air-coupled flexural wave, we were able to estimate the propagation distance, corresponding to the horizontal offset between source and microphone, by inversion of the time dispersed arrival of the chirp signal corresponding to the ice flexural wave. We also demonstrated that a microphone can record inharmonic monochromatic overtones of the air-coupled flexural wave, that were linked to the geometry and boundary conditions of the frozen lakes using finite element modal analysis. This study leads us to conclude that a simple microphone can be a powerful tool giving a surprising amount of information on the lake-ice system. Using a microphone to record air-coupled flexural waves appears to be a promising additional tool for evaluation of ice conditions, convenient enough that it could substantially increase the availability of timely and accurate information on ice thickness and thereby contribute to safer travel on floating ice.

Peak loads during dynamic ice-structure interaction caused by rapid ice strengthening at near-zero relative velocity

A series of ice penetration tests with a rigid structure, with controlled oscillation, and with a single-degree-of-freedom structure were performed to investigate the peak load-velocity dependence for ethanol-doped model ice during a test campaign at the Aalto Ice and Wave Tank. For the rigid structure and controlled-oscillation tests, the ice drift speed ranged between 1 and 150 mm s−1. In the controlled-oscillation tests, amplitudes of oscillation between 0.40 and 15.90 mm and frequencies of oscillation between 0.143 and 4 Hz were prescribed such that the relative velocity between ice and structure never became negative. A constant ice drift deceleration experiment with a single-degree-of-freedom structure was performed to investigate the development of frequency lock-in and intermittent crushing in the model ice and compare the results with the rigid structure and controlled-oscillation tests. It was found that the peak load-velocity dependence identified in the rigid structure tests was not always uniquely defined as identified in the controlled-oscillation tests because the loading history affected the peak load at ice failure. A rapid strengthening of the ice developed at low relative velocity and carried over to high relative velocity until the ice failure dissipated the strengthening effect. The strengthening effect, observed in the rigid structure and controlled-oscillation tests, was also observed during frequency lock-in and intermittent crushing in the single-degree-of-freedom structure test. The observations in the present study indicate that the so-called velocity and compliance effects in ice-structure interaction originate from the same strengthening effect. It then follows that peak loads on compliant structures cannot exceed peak loads on rigid structures in the same ice conditions, with the only difference being that the peak loads on compliant structures occur at apparently higher far-field ice drift speeds due to the change in relative velocity.

A Data-Driven Model for Ice-Breaking Resistance of Structure Based on Non-Smooth Discrete Element Method and Artificial Neural Network Method

In this paper, a data-driven model based on the Non-smooth Discrete Element Method (NDEM) and Artificial Neural Network Method (ANN) is proposed for the computation of the ice-breaking resistance of the structure. The idea of so-called “meta-modelling”, which means establishing an Artificial Neural Network (ANN) model based on a pre-computed ice failure database to avoid the time-consuming direct resolving of the ice fracture process, was integrated in the non-smooth discrete element method (NDEM). The developed model was validated by simulating the ice-breaking process of the cone structure, and the computational results match well with the experimental ones in the literature. After that, the effects of various parameters on the ice-breaking resistance were analyzed by the developed model. It was found that the factors that have great influence on the resistance of cone structure in level ice condition are the cone angle, navigation velocity and ice thickness.

ОПРЕДЕЛЕНИЕ НАГРУЗКИ С УЧЕТОМ ЛЕДОВОГО ВОРОТНИКА В ГИДРОТЕХНИЧЕСКОМ СТРОИТЕЛЬСТВЕ

Ice loads, due to large absolute values and diversity, are most important for the calculation of Arctic marine and river structures. The cost of the structure being designed may change several times with a change in the design ice load; therefore, determining the ice load of a given probability is an important task. Some ice formations can significantly change the value of the ice load, but they are not present in the normative documents and standards. Ice collars can be described as thicker ice around heat-conducting structures, which can lead to an increase in loads. However, there is not any method for calculation of ice collar influence on the loads present in the current documents. Ice collar is the reason for thicker ice at the structure-ice contact surface, which lead to an increase in the contact area and can lead to a change in the mechanism of ice failure. In some cases, the presence of an ice collar leads to an increase in the horizontal ice load from the level ice on the structure. The method of discrete elements is considered to solve the problem of the influence of the ice collar on the ice loads. This method allows a time-dependent description of the entire process of destruction of the ice collar. Two-dimension settings are used in vertical and horizontal planes. The relative ice load depending on the thickness of the ice and freezing-degree-days are obtained.

A tri-axial ice model for simulating ice-stiffened panel impact: Experiments and numerical modeling

The interaction of ice with a polar ship is complex, which may involve several ice failure mechanisms such as local crushing, tensile, cracking, bending, shearing, sliding and the ship structures could attain permanent deformations. A reasonable modeling of ice behavior is, therefore, critical to the analysis of ship-ice interactions. This paper reports an experimental and numerical study on the behavior of stiffened panels subject to the impact of a wedge-shaped ice block/indenter. The tested stiffened panel was mounted to a Falling Weight Impact Tester, and measurements were taken to help understand the dynamic responses of the structure and the ice, and also the permanent deformations. Finite element analyses using ABAQUS/EXPLICIT were also performed for the lab tests. The proposed ice model features a multi-surface yield function, empirical failure criteria for a few ice failure modes, and a representation of the remaining load carrying capacity of crushed ice. This ice model is implemented in a user-defined subroutine VUMAT and uses the cohesive element in a numerical solution. The predicted and measured impact force and structural deformation compared very well with the tests, indicating that the proposed ice model coded in VUMAT is reasonable. A series of parametric studies was then carried out to identify the key parameters of this new ice model that would have major effects on the prediction of ice impacts. The paper intends to provide test data that may be useful in understanding the complex ice-ship interaction and to introduce a numerical solution with a new ice model that improves the simulation of high-energy ice-ship impacts.

Dynamic ice loads for offshore wind support structure design

For offshore wind farms which are planned in sub-arctic regions like the Baltic Sea and Bohai Bay, support structure design has to account for load effects from dynamic ice-structure interaction. There is relatively high uncertainty related to dynamic ice loads as little to no load- and response data of offshore wind turbines exposed to drifting ice exists. In the present study the potential for the development of ice-induced vibrations for an offshore wind turbine on monopile foundation is experimentally investigated. The experiments aimed to reproduce at scale the interaction of an idling and operational 14 MW turbine with ice representative of 50-year return period Southern Baltic Sea conditions. A real-time hybrid test setup was used to allow the incorporation of the specific modal properties of an offshore wind turbine at the ice action point, as well as virtual wind loading. The experiments showed that all known regimes of ice-induced vibrations develop depending on the magnitude of the ice drift speed. At low speed this is intermittent crushing and at intermediate speeds is ‘frequency lock-in’ in the second global bending mode of the turbine. For high ice speeds continuous brittle crushing was found. A new finding is the development of an interaction regime with a strongly amplified non-harmonic first-mode response of the structure, combined with higher modes after moments of global ice failure. The regime develops between speeds where intermittent crushing and frequency lock-in in the second global bending mode develop. The development of this regime can be related to the specific modal properties of the wind turbine, for which the second and third global bending mode can be easily excited at the ice action point. Preliminary numerical simulations with a phenomenological ice model coupled to a full wind turbine model show that intermittent crushing and the new regime result in the largest bending moments for a large part of the support structure. Frequency lock-in and continuous brittle crushing result in significantly smaller bending moments throughout the structure.

Ship wave patterns on floating ice sheets

This paper aims to explore the response of a floating icesheet to a load moving in a curved path. We investigate the effect of turning on the wave patterns and strain distribution, and explore scenarios where turning increases the wave amplitude and strain in the ice, possibly leading to crack formation, fracturing and eventual ice failure. The mathematical model used here is the linearized system of differential equations introduced in Dinvay et al. (J. Fluid Mech. 876:122–149, 2019). The equations are solved using the Fourier transform in space, and the Laplace transform in time. The model is tested against existing results for comparison, and several cases of load trajectories involving turning and decelerating are tested.

Discrete Element Method Approach to Modeling Mechanical Properties of Three-Dimensional Ice Beams

The mechanical properties of ice were numerically studied using the discrete element method (DEM). For ice beam simulations, an open-source DEM library was used. The uniaxial compression test and three-point bending test for modeled ice particles with a bond model were simulated. The mechanical properties of ice were dependent on the parameters of the contact model and the bond model. The bond model was applied to simulate the failure of ice. To model the Young’s modulus, flexural strength, and compressive strength of ice, the relationship with the model parameters of the contact and bonding models was investigated, and equations proposed. Real ice in the Bohai Sea was modeled using the proposed relational equations, and its mechanical properties were predicted. Simulated mechanical properties were compared with measured data in the Bohai Sea.