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In this paper, a novel numerical simulation approach based on the finite element method for dynamically modeling the excavation process of shield tunneling is proposed, with the shield-ground interactions well captured. This method is capable of mimicking the alternating modes of advancing and stopping of a shield boring machine during underground construction, with the important effects of the cutterhead rotation and slurry support pressure considered. Under the cutting action, the soil at the excavation face would experience irreversible deformation and damage, such that additional support needs to be provided by the cutterhead blades and slurry to maintain stability. The impacts of key construction parameters are examined, including cutterhead rotary speed, advance rate, and slurry support pressure, on shield tunneling operations and ground responses. The numerical model is rigorously validated against physical model experiments. This work provides useful insights into the mechanistic processes in the stratum during shield tunneling, including the spatiotemporal evolution of ground deformation patterns and stress redistributions. The results offer valuable guidance for optimizing shield tunneling operations and enhancing tunneling safety and efficiency. [ABSTRACT FROM AUTHOR]

Simulation of the failure process of non-intact rock containing initial cracks, voids, and other discontinuities is a research hotspot in rock mechanics and geotechnical engineering. The damage smear method has attracted wide attention due to its ability to realistically depict the complete failure processes of rock from the microscopic to the macroscopic scale. However, when portraying pre-existed discontinuities, the damage smear method suffers from major difficulties such as mesh dependency and stress singularity. To overcome the limitations of current methodology, this paper proposes a novel non-break modeling strategy inspired by the extended finite element method for dealing with embedded discontinuities, in which the discontinuity of the physical fields across crack faces or the void boundary, as well as the stress singularity at the crack tip, can be characterized by introducing appropriate enrichment functions, and the penalty method is used to impose frictional contact constraints. Applications of the combined method of the improved modeling strategy and damage smear analysis to laboratory-scale and engineering-scale numerical examples show a satisfactory approximation with the analytical solution or experimental observations, indicating that the current modeling strategy can further improve computational accuracy while retaining the advantages of the damage smear method. [ABSTRACT FROM AUTHOR]

• A modified GTN model considering the effects of anisotropy and shearing on micropore evolution is introduced. • The constitutive model is compiled into a VUMAT subroutine for numerical simulation to accurately predict the plastic deformation of aluminum alloy sheet. • The parameters in constitutive model are calibrated by inverse FE method and the validity of the modified GTN model is verified through the uniaxial tensile experiment. • A FE model of the mould-sheet coupling system is further developed to improve the forming performance. Traditional GTN meso-damage model, neglecting the effect of anisotropy or shearing on the evolution of microvoid, leads to the lower predictive capabilities of forming defects for aluminum alloy sheets. In this paper, a modified constitutive model of aluminum alloy sheet considering the effect of both anisotropy and shearing is proposed, and the corresponding model parameters are calibrated by inverse finite element method and uniaxial tensile test of the smooth strip sheet without hole. Then, the constitutive equation of the modified model is compiled into a VUMAT subroutine using backward Euler integration algorithm and FORTRAN language to perform subsequent numerical simulation in ABAQUS/Explicit, the validity of the proposed shear-corrected GTN model is also verified through the uniaxial tensile experiment of the strip sheet with a hole in the middle. Finally, finite element (FE) model of the mould-sheet coupling system is developed based on the modified GTN model, and the influence of punching speed, blank holder force, friction coefficient and dwell time on the forming performance of AA5052 aluminum alloy sheet is investigated. The results show that ductile fracture of aluminum alloy sheet is most prone to exist on the upper fillet of part. [ABSTRACT FROM AUTHOR]

The particle sedimentation and phase change in the mushy zone are accompanied by a variety of complex transfer processes involving momentum, heat, and mass. It is very important to investigate the coupling process of particle settling and melting in the mushy zone for revealing the mechanism of the solid-liquid phase change. In this paper, the motion process and heat transfer characteristics of an elliptic particle as well as two particle interactions in the vertical channel were solved by the finite element method with the consideration of coupling of the phase change and motion. The Arbitrary Lagrangian-Euler Method (ALE) was employed to track the interface of the moving particle and fluid. Results show that the elliptical particle settles along the channel's center line vertically under gravity and undergoes phase change simultaneously. Uneven velocity and temperature fields surrounding the particle are generated by sedimentation, resulting in the particle with an irregular shape. When the initial position of the particle deviates from the center line, the particle deflects during the sedimentation and shifts both left and right in the X -direction. The different initial angles of settling also affect the sedimentation velocity and melting rate. When two particles settle simultaneously, they will lead to complex movement and heat transfer due to the interaction between each other. If the arrangement is eccentric, both particles undergo complex deflections during sedimentation, leading to different melting rates for the two particles. [ABSTRACT FROM AUTHOR]

The working environment of industrial fields where the Particulate Reinforced Composites (PRCs) are commonly used is complex. In these harsh environments, PRCs produce some nonlinear strains, such as plastic, thermal, and creep strains, which affect the performance of PRCs to some extent. In addition, the actual structure of PRCs contains a massive amount of inclusions, and the number of inclusions could reach the magnitude of millions or even tens of millions. For the large-scale numerical simulation of PRCs, ordinary displacement finite element requires a large number of meshes, which increases their computational complexity and unsolvability. For real PRCs with random particle distribution, homogenisation theory does not accurately capture the true state of stress concentration in PRCs. The Voronoi cell finite element method (VCFEM) can be a good solution to the drawbacks of the above two numerical simulation methods. The subject of the present work explores a modified complementary energy generalized function that takes the constitutive relationship of nonlinear strain into account, proposing a two-dimensional VCFEM, formulated with plastic, thermal, and creep strain. The simulation results are compared with the computed results of a commercial finite element software Marc to verify the validity and accuracy of the VCFEM. Results of the comparison show that the VCFEM has the advantages of simple meshing and faster computation under the same precision. The VCFEM, considering plastic, thermal, and creep strains proposed in this paper, lays the foundation for future large-scale numerical simulations of PRCs containing a large quantity of inclusion structures and can realistically capture the stress concentration state of PRCs. At the end of the article, the impact of the order of stress function on the calculation results is discussed. [ABSTRACT FROM AUTHOR]

Surface ruptures resulting from seismic faulting have the potential to inflict substantial damage to bridges straddling fault lines; hence, it is imperative to investigate the impact of ground motions documented on either side of fault rupture planes—termed as across-fault ground motion—on the seismic resilience of bridges. In this paper, the object of study is a three-span, simply supported beam bridge traversing a strike-slip fault. Utilizing the LS-DYNA finite element software platform, a sophisticated three-dimensional finite element model of the selected bridge is constructed, meticulously accounting for material damage nonlinearity and structural collision contact nonlinearity. A synthetic across-fault ground motion serves as the excitation for the seismic analysis of the bridge, systematically examining the influence of the fault-crossing angle (FCA), fault sliding rise time, and ground surface permanent rupture displacement on the dynamic response and seismic damage incurred by the simply supported beam bridge. The findings demonstrate that a diminutive fault-crossing angle (FCA) corresponds to an elevated risk of longitudinal beam collapse when a simply supported beam bridge does not intersect a fault vertically. The impact of the fault sliding rise time on the magnitude of seismic response and damage sustained by the simply supported beam bridge is relatively minuscule and can be neglected. Conversely, the ground surface permanent rupture displacement profoundly influences the dynamic response and seismic damage of the bridge. The emergence of fling-step pulses from the development of ground surface permanent rupture displacement amidst seismic activity induces a shift in failure mode-from the designer-intended bending failure to an unforeseen shear failure. • A FE model of a simply-supported beam bridge is established with consideration of material and contact nonlinearity. • The systematic parameter analysis of the simply-supported beam bridge is conducted. • The failure mode and damage process of the simply-supported beam bridge are revealed. • Recommendations for the seismic design of simply-supported beam bridges subjected to strike-slip faulting are drawn. [ABSTRACT FROM AUTHOR]

In order to meet the requirements of outfitting layout and light weight, circular or elliptical holes need to be opened on the web of the hull beam. Excessive opening will lead to stress concentration and reduce the bearing capacity of the beam. For the super-standard openings, the general strengthening method cannot guarantee the ultimate bearing capacity of the beam, and locally increasing the web to form a variable cross-section beam can compensate for the lost bearing capacity. In the present paper, the three-point bending load tests of variable cross-section opening beams and equal cross-section beams are carried out. Combined with the results of nonlinear finite element analysis, the ultimate bearing capacity and failure mode of transverse bending are compared, and it is verified that the ultimate bearing capacity of beams with variable cross-section openings is better than that of beams with equal cross-section. By changing the cross-section size and optimizing the transition form, the variable cross-section perforated beam is further improved and optimized to enhance the ultimate strength. • The three-point bending load tests of variable cross-section opening beams are carried out. • Considering the actual welding deformation, the ultimate strength prediction method of perforated beam is improved. • The variable cross-section perforated beam is optimized to enhance the ultimate strength. [ABSTRACT FROM AUTHOR]