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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]

In this paper, the intra-day multi-interval rolling-window joint dispatch and pricing of energy and reserve is studied under increasing volatile and uncertain renewable generations. A look-ahead energy-reserve co-optimization model is proposed for the rolling-window dispatch, where possible contingencies and load/renewable forecast errors over the look-ahead window are modeled as several scenario trajectories, while generation, especially its ramp, is jointly scheduled with reserve to minimize the expected system cost considering these scenarios. Based on the proposed model, marginal prices of energy and reserve are derived, which incorporate shadow prices of generators' individual ramping capability limits to eliminate their possible ramping-induced opportunity costs or arbitrages. We prove that under mild conditions, the proposed market design provides dispatch-following incentives to generators without the need for out-of-the-market uplifts, and truthful-bidding incentives of price-taking generators can be guaranteed as well. Some discussions are also made on how to fit the proposed framework into current market practice. These findings are validated in numerical simulations. • A scenario-oriented rolling-window co-optimization model of energy and reserve is proposed. • Marginal prices of energy and reserve are derived, which incorporate shadow prices of generators' ramping limits. • Dispatch-following and truthful-bidding incentives of generators are guaranteed. [ABSTRACT FROM AUTHOR]

• A novel polar mechanical metamaterial with dual deformation features. • The proposed polar mechanical metamaterial has opposite mechanical properties on coaxially opposite surfaces. • The proposed polar mechanical metamaterials are characterized by two-step deformation. • The polarity characteristic spectrum of the mechanical metamaterial is identified. • The theoretical prediction formulas for the load platform of polar mechanical metamaterials are developed. Polarity refers to the phenomenon of an object exhibiting opposite intrinsic properties in opposing directions, which plays a fundamental role in various fields including mechanical diodes, mechanical logic gates, and shock protection. This paper proposes a new mechanical metamaterial with polar and dual deformation characteristics based on a fishbone-like structure to enable a given surface structure to be hard while its opposite side is soft, while also enabling the task of adapting to different load levels on the soft side. The mechanical metamaterial displays double-stress platforms and exhibits a significant difference in mechanical response when loaded on opposite sides. Through numerical simulations, the polarity characteristic spectrum of the mechanical metamaterial is identified. The stress platform with a soft boundary predicted using Euler's instability theory was verified through both numerical simulation and experimentation. The dimensionless parameters for load differences are defined to evaluate the polar characteristics of polar mechanical metamaterials, and design guidelines are provided for achieving significant polar characteristics of polar mechanical metamaterials by discussing the influence of geometrical parameters. The proposed polar mechanical metamaterial introduces a novel design concept applicable to signal transmission, isolation, and energy absorption for different load levels. [Display omitted] [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]

This paper presents a multi-temporal formulation for simulating elastoplastic solids under cyclic loading. We leverage the proper generalized decomposition (PGD) to decompose the displacements into multiple time scales, separating the spatial and intra-cyclic dependence from the inter-cyclic variation. In contrast with the standard incremental approach, which solves the (non-linear and computationally intensive) mechanical balance equations at every time step, the proposed PGD approach allows the mechanical balance equations to be solved exclusively for the small-time intra-cyclic response, while the large-time inter-cyclic response is described by simple scalar algebraic equations. Numerical simulations exhibiting complex cyclic responses, including a 2D problem and an application to a monopile foundation, demonstrate that PGD solutions with a limited number of space–time degrees of freedom may be obtained numerically, only requiring a few modes to accurately capture the reference response. [ABSTRACT FROM AUTHOR]

An integrated attitude and orbit finite-time control based on anti-unwinding twistor representation for flying-around with non-cooperative target is proposed in this paper. Firstly, an integrated attitude and orbit model based on traditional twistor representation is established for non-cooperative flying-around problem with complex initial situation. Secondly, an anti-unwinding representation is proposed to avoid the unwinding phenomenon. Thirdly, a finite-time controller in the framework of the anti-unwinding twistor representation is designed to guarantee the spacecraft to reach the desired state quickly. Finally, the effectiveness of the proposed method is verified by numerical simulations. [ABSTRACT FROM AUTHOR]

Thermal effects on rock mass are involved in many fields, including enhanced oil and gas recovery, unconventional oil and gas development, and nuclear waste deep placement. Temperature change will produce thermal stress in rock mass, leading to thermal cracking. Thermal cracking of shale is frequently involved in these fields. The mechanism of thermal cracking formation in shale is studied in this paper using the method of indoor heating experiment and particle flow method, which discovered that it is difficult to produce obvious thermal cracking in shale matrix, and only a few intercrystalline and intercrystalline fractures and shrinkage fractures of organic matter occur locally. Based on the particle flow method, a shale particle flow model is built that is highly consistent with the macro and micro characteristics of shale, while the systematic calibration method for shale particle flow model microscopic parameters can realize effective calibration of shale particle flow mechanical model microscopic parameters. Using a linked thermodynamic coupling model of shale particle flow based on the mechanical model of shale particle flow, the impacts of heating modes, natural micro cracks, and confining pressures on the thermal cracking evolution of shale were studied. [ABSTRACT FROM AUTHOR]

This paper presents the development of a data-based model predictive control method for a semi-active suspension system with air springs and continuous damping. A continuous damping controller (CDC) has been devised for the system to alter its damping coefficient in real-time, capable of reducing the impact of external road disturbances. In this research, the damping force has been split up into a nominal force and a controllable additional force, allowing the system to be modelled as a linear time-invariant system, despite the inherent nonlinearity of air spring suspension systems. In consideration of such constraints given by the damper, a model predictive controller (MPC) has been devised with the goal of improving ride comfort. Additionally, Gaussian process regression (GPR) has been used to compensate for output estimation errors arising from model parameter uncertainties. The semi-active suspension system also featured a multichamber air spring with three available modes of stiffness. Hence, a stiffness controller has been designed to select an appropriate mode based on the predicted vehicle states given by the MPC using road preview information and a reduced full-car model. The proposed algorithm has been verified using computer simulations. The results showed that compensations for model errors made with GPR significantly improves ride comfort even in the presence of parameter uncertainties. Additionally, both the damping controller and stiffness mode selector were successfully implemented into an actual test vehicle. Vehicle test results showed the proposed algorithm to be robust and effective in enhancing ride comfort and reducing vehicle pitch motion. [ABSTRACT FROM AUTHOR]

Bypass dual throat nozzle (BDTN) is a new kind of fluidic thrust vectoring nozzle that can provide thrust vectoring by controlling self-adaptive flow. In this paper, BDTN-tab is proposed to improve the mixing ability of the nozzle. It is defined as a new kind of BDTN with an outlet modified by a pair of tabs. Under the premise of ensuring the nozzle outlet projected area remains unchanged, the pair of tabs coplanar with the convergent section of the cavity is designed to be. This design takes aerodynamic performance, thrust vectoring performance and mixing ability into account. Conclusions can be drawn through theoretical analysis, design, numerical simulation and wind tunnel experiments: The BDTN-tab can produce a thrust vectoring angle by opening the bypass valve, which can reach an extreme angle of 32°. As the tab angle increases, the thrust coefficient and thrust vectoring angle of the nozzle decrease. However, the vortex intensity at the nozzle outlet increases and can enhance the mixing between primary flow and external flow. [ABSTRACT FROM AUTHOR]

This paper investigates the problem of integrated guidance and control (IGC) law design with impact angle and general field-of-view (FOV) constraints. Firstly, the IGC model for intercepting non-maneuvering moving target is parameterized by state-dependent coefficient matrices. The nominal IGC law for intercepting the target with the desired impact angle is obtained by solving the state-dependent Riccati equation. Secondly, since the relative degrees of the general FOV constraints with respect to the IGC model exceed one, the high-order control barrier functions are constructed. The satisfaction of the FOV constraints is equivalent to ensuring that the superlevel sets defined by the barrier functions are forward invariant, which is converted into affine constraints on the control input. The nominal IGC law is modified in a minimally invasive way by quadratic programming. Then, the proposed method is extended to the case of intercepting maneuvering target by leveraging a relative coordinate frame. Finally, numerical simulations are conducted to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents an improved process for the modeling, model order reduction (MOR), and control design of a flexible flying wing unmanned aerial vehicle based on the linear parameter-varying (LPV) technology. By applying the Lagrangian formulation and doublet lattice method, the aeroservoelastic (ASE) model of the flexible aircraft is first derived and then rewritten as an airspeed-dependent LPV system, which consists of rigid-body states, structural modes, aerodynamic states, etc. This leads to a high-order LPV model, and the stability of the system varies from stable to unstable when the speed of the aircraft exceeds the critical flutter speed. To facilitate the control design, an oblique projection-based MOR method is then adopted to reduce the order of the plant. Different from previous studies, the MOR method is improved to systematically generate a reduced-order LPV model with consistent states for both the stable and unstable dynamics parts. Finally, an output-feedback LPV controller is designed to simultaneously achieve the body freedom flutter suppression and longitudinal attitude control. Numerical simulation results show the effectiveness of the improved LPV-based ASE modeling, order reduction, and control design process for the flexible aircraft. [ABSTRACT FROM AUTHOR]

This paper presents an advanced Volume of Fluid (VOF) method that enables performant three dimensional Direct Numerical Simulations (DNS) of the interaction of two immiscible fluids in a gaseous environment with large topology changes, e.g., binary droplet collisions. One of the challenges associated with the introduction of a third immiscible phase into the VOF method is the reconstruction of the phase boundaries near the triple line in arbitrary arrangements. For this purpose, an efficient method based on a Piecewise Linear Interface Calculation (PLIC) is shown. Moreover, the surface force modeling with the robust Continuous Surface Stress (CSS) model was enhanced to treat such three-phase situations with large topology changes and thin films. A consistent scaling of the fluid properties at the interfaces ensures energy conservation. The implementation of these methods in the multi-phase flow solver Free Surface 3D (FS3D) allowed a successful validation. A qualitative comparison of the morphology in binary collisions of immiscible droplets as well as a quantitative comparison regarding the threshold velocities that distinguish different collision regimes shows excellent agreement with experimental results. These simulations enable the evaluation of experimentally inaccessible data like the contributions of kinetic, surface and dissipative energy of both immiscible liquids during the collision process. Furthermore, the comparison against binary collisions of the same liquids highlights similarities and differences between immiscible and equal droplet collisions. Both can support the modeling of the immiscible liquid interaction in the future. [Display omitted] • Predictive and energy-conserving DNS of immiscible liquids' interaction. • Framework for simulation of large topology changes, thin films and triple lines. • Extension of the VOF method with three-phase PLIC and a modified CSS model. • Implementation into multi-phase solver shows excellent agreement with experiments. • Comparison with single-liquid collisions reveals the dominant liquid phase. [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]

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]