Coupled Eulerian Lagrangian Finite Element Research Articles

Investigation of the peak punch-through capacity of spudcan on sand overlying spatially variable clay

Accurately estimating peak penetration resistance in punch-through sensitive deposits is crucial for managing risks during jack-up rig installations. While offshore clays exhibit significant spatial variability, necessitating consideration of spatial variability in predicting peak penetration resistance. This study investigates the effects of spatial variability of underlying clay on the failure mechanism and magnitude of peak penetration resistance during punch-through incidents. The Modified Linear Estimation Method was used to generate three-dimensional random fields, incorporated into coupled Eulerian Lagrangian finite element analyses to simulate spudcan penetration from the ground surface. Results show that while spatial variability has an insignificant effect on the failure mechanism in the upper sand layer, it significantly alters soil flow in the underlying clay, leading to variations in peak penetration resistance. The peak penetration resistance follows a log-normal distribution, and a relationship was established between the probability of failure and the factor of safety. This study highlights the importance of considering soil spatial variability and demonstrates the significant impact of underlying clay on the failure mechanism and magnitude of peak penetration resistance during punch-through incidents, which might be helpful for the safety management of industry.

Coupled Eulerian-Lagrangian Debris Flow Model with Flexible Barrier

Natural hazards such as large debris flow events can have catastrophic effects on the environment and critical infrastructure, posing a significant threat to human life. Debris flows often exhibit high velocity, high-pressure discharges due to their bulk volume, and the capacity to transport considerable volumes of large rocks, boulders, and woody debris. Although debris flow run-out simulations are commonly performed using hydraulic modelling software, these environments are seldom capable of assessing the interaction between the debris fluid, transported material, and protective structures. In this research, large deformation numerical models are calibrated using input parameters from hydraulic modelling software. Due to the computational cost of the large deformation models involving fluid-solid-structure simulation with flexible net barriers, an equivalent stiffness method is implemented to provide comparable performance through a membrane structure. The Coupled Eulerian-Lagrangian Finite Element method is used to model the impact forces of rocky boulders on the membrane, exhibiting damage characteristics consistent with flexible ring-net protective structures. The Coupled Eulerian-Lagrangian model results highlight the performance of the simplified membrane, as shown through a benchmark simulation of debris flow with boulders.

Digital Filter Design for Force Signals from Eulerian–Lagrangian Analyses of Wave Impact on Bridges

Finite element (FE) models that simulate wave–superstructure interactions with the coupled Eulerian–Lagrangian (CEL) technique provide a viable and economical solution to estimate wave impact forces on bridge superstructures. One of the main drawbacks of CEL FE models is that they produce solutions distorted by numerical artifacts with very high frequencies that make it difficult to quantify the magnitude of hydrodynamic forces on superstructures. This paper investigated digital filter parameters for horizontal forces extracted from CEL FE models. The optimal filter configuration was evaluated by comparing unfiltered and filtered horizontal force signals with experimentally measured values from a reduced-scale superstructure specimen tested at the O.H. Hinsdale Wave Research Laboratory at Oregon State University. It was found that digital filters with cutoff frequencies below the fundamental frequency of the superstructure produced the best results and that optimizing Eulerian–Lagrangian surface interactions significantly improved the quality of the calculated force signals.

Coupled Eulerian-Lagrangian finite element analysis of penetration processes in silty clay for bucket foundation

ABSTRACT Bucket foundations, as an innovative type of offshore wind turbine foundation, have been widely adopted for their cost competitiveness and time effectiveness in construction and installation. For a successful installation, the penetration process prediction is crucial. This paper investigates the penetration process of both thin-walled and thick-walled bucket foundations in silty clay through small-scale experiments. Based on the experimental results, empirical formulas of penetration resistance are modified. Next, a Coupled Eulerian-Lagrangian (CEL) numerical method is validated and used to simulate the sinking process of engineering prototypes. The penetration resistance obtained by the calculated and numerical methods is in good agreement. Additionally, through the 3D CEL analysis, the disturbance of bulkheads and skirts on soil plugs is gained. The Eulerian volume fraction shows that the soil surface within the outer compartments is prone to rise to form a soil plug, which will bring out a sudden sharp increase in the penetration resistance due to the contact of lid and soil, and consequently affect the ultimate installation depth.

Large Displacement Finite Element Modelling of the Screw Driving Sounding Test in Sandy Soil Using the Coupled Eulerian-Lagrangian Method

The Screw Driving Sounding (SDS) is a recently developed in-situ testing method for soil/site characterisation. To better understand the mechanism of testing, it is essential to create a simulation model for the SDS test to assist in better understanding the response and in improving the testing process, not to mention the development of empirical correlations to estimate geotechnical parameters for use in design. Complex problems involving large deformations are usually difficult to solve with the classical finite element (FE) method because large deformations can lead to large mesh distortions and contact problems. In this paper, a computational model using the finite element method is developed to simulate the drilling process involved in SDS tests; the Coupled Eulerian-Lagrangian (CEL) approach is used to deal with large deformation problems. The SDS drilling process in a sandy deposit with defined stress states (i.e., relative density and effective confining pressure) is simulated, and the SDS-derived parameters are monitored. Based on the simulation results, a chart was established to correlate the measured SDS parameter with the internal friction angle for different vertical effective overburden stresses. The derived chart is validated with the results of laboratory tests performed on samples taken from several sites in Christchurch, NZ, adjacent to the locations of the SDS tests. The results show that the CEL FE framework can model complex physical processes encountered during the SDS drilling. Moreover, the developed chart can be used to estimate the friction angle of the sandy soil based on the SDS-measured torque at a given depth.

Study on the effect of entrainment on the behavior of debris flows using a 3D Coupled Eulerian–Lagrangian finite element method

Study on the effect of entrainment on the behavior of debris flows using a 3D Coupled Eulerian–Lagrangian finite element method

Effects of rotation tool-induced heat and material flow behaviour on friction stir lapped Al/steel joint formation and resultant microstructure

Reliable joining of Al/steel via friction stir lap welding (FSLW) is strongly dependent on interfacial macro-/micro-structures. However, how the underlying thermo-mechanical process affects them and how they can be controlled remain unclear. In this study, a 3D coupled Eulerian–Lagrangian finite element model was integrated with a tracer particle technique to simulate the FSLW of Al alloy 5052 and high-strength DP590 steel, to elucidate the role of tool-induced heat and material flow. The results showed that the material flow recirculated near the shoulder and pin, which mainly originated from the advancing side of the Al and the retreating side of the steel. Increasing the rotational velocity intensified the overall material flow, resulting in increased migration on the steel side. Insufficient steel migration around the pin at lower rotational velocities was mainly responsible for the micro-voids and non-bonding defects at the lap interface. The asynchronous convergence of Al and steel flowing from the advancing and retreating sides, respectively, refilled the instantaneous gap, thereby normally bonding the lapped interface behind the pin. The rotational pin affected the hook structure and steel fragment formation through the shearing and squeezing of the steel migration flow. Material inter-migration produced an intercalated structure at the lapped Al/steel interface. The extremely high temperature, approximately above Al 5052 solidus temperature, under the pin bottom caused the formation of a thicker intermetallic compound (IMC), thereby considerably reducing the interfacial strength. Multi-scale mechanical strength assessments indicated that an intercalated interfacial structure with a thickness of Al-rich IMC layer less than ∼1.0 μm was desirable because it exhibited a higher local interfacial strength than the Al matrix.

An efficient strategy for 3D numerical simulation of friction stir welding process of pure copper plates

Copper and its alloys have a wide spectrum of engineering applications such as heat exchangers, hot water tanks or nuclear pressure vessels. Most of these structures are obtained by welding. Unfortunately, the use of conventional arc welding process is affected by several factors such as the thermal conductivity of the alloy being welded, the shielding gas, the joint design, the welding position, and the surface condition and its cleanliness. Friction stir welding process could be an interesting alternative as it can be performed without melting the material, it involves a non-consumable tool, and provides good mechanical properties. To understand in depth both the physical and the thermal mechanisms involved in this process, numerical modelling is essential. The aim of this paper is to propose an efficient simulation strategy based on the coupled Eulerian Lagrangian finite element method. The mass scaling procedure, which is used to decrease the computation time will be presented, as well as its effect on the temperature field distribution and on the down force. This model will then be used for a parametric study in order to improve the friction welding process’s parameters.

Pull-out capacity of an inclined embedded torpedo anchor subjected to combined vertical and horizontal loading

Abstract Whilst the installed torpedo anchors in offshore practice are often characterized with off-verticality, the effect of inclination on the anchor pull-out capacity has seemingly received little attention in the research literature. This paper presents a numerical study on the pullout capacities and failure envelopes of inclined embedded torpedo anchors subjected to combined vertical and horizontal loading. Using Coupled Eulerian–Lagrangian finite element method, effects of load inclination, azimuthal angle of pull-out plane and anchor inclination were sequentially evaluated. It was found the most critical pull-out plane is the one that coincides with anchor plane towards the anchor inclination direction. Its corresponding failure envelope, which can be well fitted by a closed form expression, gives the conservative estimation of anchor pull-out capacities. The comprehensive parametric investigation indicated this conservative failure envelope is mainly affected by anchor inclination and soil’s strength gradient. A series of tables with fitting constant values appropriate for different strength and inclination conditions were furnished. On these bases, a simple design procedure was developed for estimating the ultimate pull-out capacities of inclined embedded torpedo anchors. The outcomes of this work are likely of help for engineers to factor the anchor inclination into the design practice of torpedo anchors.

Development of a Coupled Eulerian-Lagrangian Finite Element Model for Dissimilar Friction Stir Welding

Development of a Coupled Eulerian-Lagrangian Finite Element Model for Dissimilar Friction Stir Welding

Slope stability analysis based on the Coupled Eulerian-Lagrangian finite element method

Slope stability analysis based on the finite element method (FEM) is a powerful tool compared with the limit equilibrium (LEM) methods. However, mesh distortion of the traditional Lagrangian FEM may result in convergence difficulty of numerical simulation, and the obtained factor of safety (FOS) of the slope is not reliable. In this study, a slope stability analysis method based on the Coupled Eulerian-Lagrangian (CEL) numerical strategy with an energy based criterion is proposed. For three examples (a gentle homogeneous slope, a steep homogeneous slope and a slope with thin soft band), the results of the proposed method, the traditional Lagrangian FEM based slope stability method and the LEM method are compared. For the gentle homogeneous slope, both the proposed method and the traditional Lagrangian FEM based slope stability method can obtain credible FOS values, and the shear bands are consistent with the critical slip surface of the LEM method. The FOS value of the steep homogeneous slope is underestimated by the traditional Lagrangian FEM based method as the extreme geometry of the slope amplifies the nonlinearity and causes early termination of finite element modeling. For a slope with a thin soft band, the FOS value obtained using the traditional Lagrangian FEM based method is not valid due to severe mesh distortion. The present method can obtain reliable results for both local failure and global failure for the slope with a thin soft band.

Coupled Eulerian-Lagrangian finite element method for simulating soil-tool interaction

Simulation of soil-tool interaction is challenging due to large deformations of soil around the tool, unconstrained deformation of the free soil surface and the dynamic behaviour of soil-tool interaction at the interface. An application of a coupled Eulerian-Lagrangian finite element (CEL-FE) method to the simulation of soil-tool interaction is presented. By combining the merits of both the Lagrangian and the Eulerian formulations, large deformation and unconstrained deformation of soil and the dynamic behaviour of soil-tool interaction are simultaneously simulated. Firstly, interactions between the soil and vertical tines were simulated. The results showed that the predicted soil deformation and draft force were in reasonable agreement with published data from soil bin tests. Then, in order to further validate the feasibility and effectiveness of the CEL-FE method, interactions between the soil and inclined blades at different operating conditions were simulated. Results showed that the numerically simulated and experimentally measured draft forces exhibited similar trends and average values. In addition, the predicted soil deformation was in general agreement with experimental observations. Finally, an example of simulating soil-mouldboard interaction was given and preliminary results indicated that shape complexity of this tool was not a limitation for applying the CEL-FE method. The proposed CEL-FE method provides new possibilities for simulating soil-tool interaction and it is hoped that this method will help to contribute a better understanding of the soil-tool interaction process thereby improving the design of tillage tools.

Application of the Coupled Eulerian-Lagrangian finite element method on piezocone penetration test in clays

This paper proposed a Coupled Eulerian-Lagrangian (CEL) finite element model to estimate the undrained piezocone resistance and penetration pore pressure in modified Cam clay (MCC). The numerical model is verified through comparison with a series of miniature piezocone penetration test in calibration chamber. The value of cone tip resistance (qc), excess pore pressure at cone face (u1) and cone shoulder (u2) obtained from CEL model are also compared with the analytic closed-form solution of cavity expansion. Consequently, the value of qc is underpredicted by cavity expansion approach, but the predicted value of excess pore pressure for ordinary consolidated clays is in fairly good agreement with the value CEL modeled.

Underwater nearfield blast performance of hydrothermally degraded carbon–epoxy composite structures

An experimental and computational study was conducted to evaluate the dynamic response of weathered biaxial composite plates subjected to near-field explosive/blast loadings. Naval structures are subjected to aggressive marine environments during their service life that can significantly degrade their performance over time. The composite materials in this study are carbon–epoxy composite plates with [0, 90]s and [45, − 45]s layups. The composites were aged rapidly through submersion in 65 $$^{\circ }$$ C seawater for 35 and 70 days, which through Arrhenius’ methodology, simulates approximately 10 and 20 years of operating conditions, respectively. Experiments were performed by clamping the composite plates to an air-backed enclosure inside an underwater blast facility. During the experiments, an RP-503 explosive was submerged, behind the composite specimen, and detonated. Meanwhile, transducers measured the pressure emitted by the explosive, and three high-speed cameras captured the event. Two of the cameras were placed facing the specimen to measure full field displacement, velocities, and strains through a 3D digital image correlation analysis. The third high-speed camera was used to record the explosive’s behavior and bubble-to-specimen interaction. Additional experiments were performed to obtain the non-weathered and weathered material properties as well as the residual strength post the blast experiments. Additionally, a coupled Eulerian–Lagrangian finite element simulation was conducted to complement the experimental findings. Results show that the diffusion of water into the composite material leads to a more prominent blast response as well as the degradation of mechanical properties, especially shear properties which are dominated by the epoxy matrix. Residual strength experiments also show a substantial decrease in the structural integrity post-blast loading for the weathered composites. Lastly, the numerical simulations showed substantial increase in maximum strains with relatively small decreases in mechanical stiffness. Hence, even past the saturation point, incremental changes in material properties can have a significant impact on mechanical performance.

A Coupled Eulerian Lagrangian Finite Element Model of Drilling Titanium and Aluminium Alloys

A Coupled Eulerian Lagrangian Finite Element Model of Drilling Titanium and Aluminium Alloys

Experimental Analysis and Microstructure Modeling of Friction Stir Extrusion of Magnesium Chips

In this work, the feasibility to recycle pure magnesium machining chips is first investigated experimentally with a solid-state recycling technique of friction stir extrusion (FSE). Heat generated from frictions among the stirring chips, die, and mold facilitates the extrusion process. Mechanical tests, optical microscopy (OM), and scanning electron microscopy (SEM) analysis are conducted to evaluate the mechanical and metallurgical properties of extruded wires. Mechanical tests show that almost all recycled specimens can achieve higher strength and elongation than original material of magnesium at room temperature. Due to a refined grain microstructure, good mechanical properties are obtained for samples produced by the rotational speed of 250 rpm and plunge rate of 14 mm/min. A metallo-thermo-mechanical coupled analysis is further conducted to understand the effects of process parameters. The analysis is carried out with a multistep two-dimensional (2D) coupled Eulerian–Lagrangian finite-element (FE) method using abaqus. The material constitutive model considers both work hardening and strain softening. Material grain size evolution is modeled by dynamic recrystallization (DRX) kinetics laws. The deformation process and its consequential microstructural attributes of grain size and microhardness are simulated. Physics principles of the microstructure evolution are discussed based on both experimental and numerical analyses.

Multiphysics modeling and characterization of explosively loaded aluminum blocks

A coupled Eulerian–Lagrangian finite element simulation is made of an aluminum block of dimensions 4 × 2 × 1/2 in (101.6 × 50.8 × 12.7 mm) subjected to an intensive shock load at its top. The shock load was introduced by the detonation of plastic explosives which were attached to the top of the block. The objective is to determine the effect of the shock on the deformation history of the metallic block accounting for strain rate effects. The dynamic response of the block to the high-pressure pulse was simulated by taking into account the resulting elasto-plastic deformation, the solid–fluid interaction and the adiabatic temperature rise. The dynamics of the transient stresses below the loaded surface was captured by our model. Three aspects of the explosive shock load were accordingly examined: (i) the explosive thickness and (ii) the explosive overhang length and thickness upon the resulting deformation pattern. Upon the complete dissipation of the shock, we were able to determine the distribution of the residual stress in the principal directions. Compressive residual stresses were observed in the region at and below the surface of the loaded end. The above predictions were experimentally validated using explosively loaded aluminum blocks. The experimental findings revealed general agreement with the finite element predictions of both the deformation pattern and the residual stresses.

3D analysis of transverse pipe–soil interaction using 2D soil slices

Offshore pipelines are often laid directly on the seabed, particularly in deep water. Cyclic changes in the temperature and pressure of the pipe contents can lead to cyclic growth and contraction of (planned) lateral buckles. This results in severe plastic deformation of the near-surface soil as it is progressively scraped away and accumulated into berms by the lateral sweeping motion of the pipe. Quantifying the resistance offered by the soil is important in design, notably for fatigue calculations. This paper presents a new computational approach for modelling pipe–soil interaction during events dominated by large transverse pipe displacements. The main novelty is that a three-dimensional (3D) structural model of the pipe interacts with a series of discrete two-dimensional (2D) (plane strain) soil domains. Each ‘slice’ of soil is analysed using a coupled Eulerian–Lagrangian finite-element technique, though other large-displacement numerical methods could be employed. The concept is similar to recently developed macro-element approaches, except that the pipe–soil interaction at each (assumed) planar cross-section is captured by a 2D continuum model rather than by a 2D user-defined spring model. This is more efficient than a full 3D analysis of the pipeline and surrounding soil, yet it allows results of comparable accuracy to be obtained. This paper illustrates the new methodology with a simple calculation.

Coupled Eulerian Lagrangian finite element modeling of friction stir welding processes

A 3-dimensional localized finite element model (FEM) is developed to predict likely conditions that result in defect generation during friction stir welding (FSW). The workpiece is modeled using Eulerian formulation, while the tool is modeled using Lagrangian. Coulomb's frictional contact model is adopted to define the tool workpiece interaction, while the welding speed is defined by material inflow and outflow velocities. The numerical results show that the coefficient of friction has a major effect on void formation; the lower the friction coefficient is applied, the larger the void is formed. Furthermore, welding using force control (FC) at lower welding speed results in smaller void size and wider plastic zone, leading to higher quality weld.