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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]

Multi-walled carbon nanotubes/polydimethylsiloxane (MWCNTs/PDMS) composites have excellent electromechanical conversion ability which can be applied in the field of intelligent sensing. However, the volume changes and electromechanical response mechanism of MWCNTs/PDMS under dynamic load remain unclear. In this paper, the electromechanical response of MWCNTs/PDMS with different mass ratio of MWCNTs are studied by quasi-static compression, SHPB experiment and finite element numerical simulation. The quasi-static compression results show that volume ratios of MWCNTs/PDMS are decreased with compression strain (0.845 when strain is 0.5), then, the Yeoh hyperelastic constitutive model is established considering volume change. When the mass ratio of MWCNTs is 1 wt%, MWCNTs/PDMS shows the best mechanical properties. The stationary phases of strain rate of MWCNTs/PDMS decrease with increasing of impact velocity, showing obvious viscoelastic mechanical properties. The impact induced voltages of MWCNTs/PDMS are generally larger than PDMS (10∼15 m/s). The flexoelectric effect of MWCNTs/PDMS under impact is further studied based on numerical simulations. The results show that the strain gradients are within 10−2∼10−1 m−1, the related flexoelectric coefficients are within 10−10–10−9 C/m. In summary, this study can further expand the application of MWCNTs/PDMS in the field of intelligent sensing. • The constitutive model of MWCNTs/PDMS composites considering volume change is established. • The impact induced flexoelectric effect of MWCNTs/PDMS is mainly related to strain gradient ∂ ε z z / ∂ x z. • CNTs 1wt% /PDMS composite has the largest flexoelectric coefficients: μ zzzz = 6.447 × 10−9 C/m, μ xxzz = −6.04 × 10−10 C/m, μ xzxz = 1.23 × 10−10 C/m. [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]

Based on a number of numerical investigations into welding simulations, highly non-linear welding-induced residual stresses within high strength S690 welded H-sections have been evaluated successfully, and surface residual stresses along their flange / web junctions have been carefully calibrated against measured data. This modelling technique has been extended to cover residual stresses of cold-formed circular hollow sections recently, and also of cold-formed square hollow sections as described in this paper. Hence, a full presentation on the proposed approach of integrated and coordinated numerical simulations on various mechanical, heat transfer and thermomechanical, and stresses analyses on these cold-formed square hollow sections is described. Subsequent structural analyses of these models on both stocky and slender columns of these cold-formed square hollow sections are then carried out. Structural adequacy of the proposed approach is thoroughly demonstrated through a systematic calibration against various measured data – both temperatures and residual stresses of these sections induced during fabrication, and load-deformation curves of these sections under compression. It should be noted that the proposed approach provides a scientific mechanism to determine directly residual stresses due to transverse bending and longitudinal welding as initial materials imperfections in these high strength S690 cold-formed square hollow sections. With an adoption of the lowest eigenmodes of these columns as their initial geometric imperfections after adjusted with measured or design values of the member out-of-straightness, both the effects of initial materials and of initial geometric imperfections onto the structural performance of these columns are readily quantified separately. [Display omitted] • An integrated and coordinated numerical simulation approach is developed. • Fabrication-induced effects of cold-formed square hollow sections are considered. • Both residual stresses and strains are incorporated into the structural models. • All of the models have been calibrated with measured results of stocky and slender columns. [ABSTRACT FROM AUTHOR]