Traditional robots comprised of rigid components are usually hard to adapt to different environment and would be dangerous when interacting with humans. Inspired by nature, soft robots exhibit exceptional flexibility and adaptability. However, due to their numerous degrees of freedom, optimizing and controlling soft robots pose challenges. Mechanics-based modeling and numerical simulation offer insights into guiding soft robot design and manufacturing. This article focuses on recent advances in soft robot dynamic simulation, emphasizing structural modeling methods and interactive simulation methods in theoretical calculations. For structural modeling methods, we begin with three-dimensional models, by introducing the static models, deformable frameworks, and differentiable projected dynamics. Moving on to plate and shell models, we explore the classic Kirchhoff-Love plate models and discrete shell models. Then, we delve into simplified models, covering basic model theories such as piecewise constant curvature model, Cosserat rod models, and absolute nodal coordinate methods. We also introduce the central parameter models, which are widely used for physical modeling. Case studies of exemplary works help investigate the advantages and limitations of these simplified models. In the interactive simulation techniques, focusing on the dynamic simulations, we integrate previous sections on the interaction models, discussing external environmental interaction and external field-driven interaction. We address challenges and strategies in the dynamic simulations of soft robots. Our aim is to provide novel dynamic simulation approaches to robotic developers, enhancing simulation accuracy and providing theoretical support for optimized design and online control of soft robots.

Upon charge-discharge cycling, lithium-ion batteries inevitably undergo capacity fading, which is a common and well-acknowledged phenomenon. However, the mechanisms behind this apparent performance degradation are inherently complex. In this review, the mechanical-electrochemical coupling degradation mechanisms of lithium-ion batteries in multi-scale, multi-field, and multi-process are comprehensively reviewed, starting from the particle scale to the electrode scale, with a specific focus on degradation in solid-state batteries. Furthermore, the degradation models used to describe the mechanical-electrochemical coupling degradation behavior of lithium-ion batteries are reviewed. It should be noted that due to the complexity of battery degradation mechanisms and the scarcity of externally measurable parameters, establishing degradation models is challenging, and there is still a considerable research gap. In light of this, a conceptual bidirectional degradation model that integrates physical models and data-driven models is proposed. Serving as links, internal variables with meaningful physical implications should be introduced to establish a comprehensive mapping of "mechanical behavior-internal variables-degradation behavior", to provide a novel approach for objectively and accurately describing and predicting battery degradation behavior.

The corrugated dragonfly wings are always deformed with cambered sections during flight. To study the aerodynamic performance of dragonfly wings in forward flight, two dimensional corrugated airfoils are designed, considering the heights and chordwise location of maximum camber. Then the aerodynamic forces are calculated in Fluent software by the overlapping grid method. Firstly, lift of the corrugated airfoils with positive camber are significantly improved compared with flat airfoil. Both the lift and thrust can be enhanced when the airfoil is well-designed with camber such as m=4 % and p=0.2. Secondly, the lift of cambered airfoils is increased while the trust will be decreased when the torsional angle is enlarged in flapping. Moving the position of maximal camber height to the trailing edge can help to improve the trust at high torsional angle. As a result, the aerodynamic performance of corrugated airfoil can be greatly improved by introducing the camber with well-designed height and position.

Composite pressure structures refer to components made of composite materials designed to withstand pressure, such as hydrogen storage tanks for vehicles, liquid oxygen tanks, and solid rocket engines. These structures possess numerous advantages including lightweight, high strength, and excellent design flexibility, making them widely employed in aerospace, automotive, and petrochemical industries. However, under severe service conditions, the accumulation and propagation of damage in composite pressure structures can easily lead to component failure. Therefore, the development of advanced structural health monitoring technologies is crucial for enhancing their in-service safety. This paper begins by comprehensively comparing the advantages and disadvantages of monitoring methods such as ultrasonic guided waves, acoustic emission, infrared, and fiber optic gratings, focusing particularly on the methods and research progress of structural health monitoring for composite pressure structures. Subsequently, addressing the material characteristics of composite pressure structures, we discuss the application and key challenges of implanted micro/nano-material sensors in monitoring the interfacial and interlaminar properties of fiber/matrix. Finally, we explore the development progress of novel sensing technologies and artificial intelligence methods, and analyze their application prospects in the in-service safety of composite pressure structures.

In order to study the different damage characteristics of the aero-engine fan blades caused by the impact of foreign objects, a finite element model was constructed based on the rate-dependent constitutive model and impact tests were carried out through a light air cannon system to evaluate the damage caused by the foreign objects at different impact positions, using the 304 steel balls of 6 mm, 10 mm and 14 mm sizes as the bullets and a retired aero-engine blade as the target plate. The FOD damage area based on the impact response of the simulation model was compared with the experimental damage area, and high consistency was achieved between the two results in terms of the area size and shape. After that, the effects of impact position, angle and bullet size on the velocity change trend during the impact response were investigated using the constructed model. The results show that the impact resistance of the blade differs greatly at different positions and the bullet size plays a decisive role on the damage area. In addition, the change trend of the remaining velocity of the bullet is different when the damage pattern is different.

To explore the influence of different types of micro-nozzles on the atomization in the transdermal drug delivery, this work takes a converging nozzle and a de Laval nozzle as the research objects. Firstly, the Phase Doppler Particle Analyzer (PDPA) is employed to measure the distributions of velocity and particle size of the droplets from the atomization of the two nozzles. Then, to understand the internal flow conditions, a dynamic pressure sensor is utilized to measure the gas pressure in the nozzle, and the Schlieren imaging is employed to observe the flow in the nozzle. Finally, a skin model is subjected to the impact test of high-speed droplets, where methylene blue solution and Evans blue solution are used as staining agents, and fresh pig ears are adopted as the test objects. The PDPA experiment shows that the atomization of the droplets through the de Laval nozzle is more complete than that through the converging nozzle. The experiment of the internal pressure measurement shows that there is a shock wave in the de Laval nozzle, indicating a supersonic speed at upstream. The Schlieren experimental results directly show that in the de Laval nozzle concerned in this study, the gas flow forms two staggered oblique shock waves, instead of a normal shock wave in the expansion section. The impact test of skin model indicates that the high-speed droplets penetrate through the layer of stratum corneum, which demonstrates the application potential of transdermal delivery of drugs in the aesthetic medicine industry. This work lays the foundation for further investigations of novel means for transdermal drug delivery.

With the development of aerospace technology, large membrane diffraction space telescopes have gained widespread attention and research due to their advantages such as small mass and volume, high optical imaging capability, and ease of folding and unfolding. In this paper, we conduct vibration control research on a large membrane diffraction space telescope and provide a vibration control strategy based on piezoelectric actuators. Firstly, the finite element method is used to establish the dynamic model of the structure. Then, the position of the actuator is studied based on the controllability criterion. The control law is designed based on the fuzzy proportional-derivative (PD) algorithm. Finally, the effectiveness of the proposed method in this paper is verified through numerical simulation. In this paper, the corresponding relationship between the number of piezoelectric actuators and the stability time is studied through numerical simulation, and the robustness of the control law is also investigated.

With the rapid development of aeroengine field, the service environment of hot end turbine blade is becoming increasing severe. In order to improve the heat bearing capacity of blade, the double-walled blade structure is proposed in the industry, which is based on the principle of "outer wall heat bearing, inner wall load bearing". In this paper, aiming at ensuring the structural strength of double-walled blade film hole, a parametric modeling is used to construct the blade shape and the outer wall hole structure, and the influences of hole design parameters on the perimeter structure strength of the cylindrical film hole, the conical expansion hole and the dustpan expansion hole are determined through simulation analysis. Then, according to the parameter input and the corresponding response, a Radial Basis Function (RBF) neural network model is constructed and further optimized through adjusting the weights and thresholds using the genetic algorithm to improve the accuracy of the surrogate model. Finally, the optimal hole designs for three film holes are obtained. Compared with the original cylindrical hole, the perimeter stress is reduced by 25.12 % and 22.54 %, respectively for the conical expansion hole and the dustpan expansion hole.

In the saturation calculation of the two-phase flow in porous media using Sequential Fully Implicit (SFI) method, the topological sorting algorithm can be used to speed up the nonlinear solution procedure by decomposing the discrete global nonlinear system into a sequence of local nonlinear systems. In this article, we employ the breadth first algorithm (BFS) and the depth first search (DFS) method in graph theory to implement the parallel solution of the saturation distributions. For the cocurrent flow, where both bi-phase velocities have the same direction in the whole calculation domain, the grid system is divided into different groups, where based on the BFS algorithm the grids simultaneously participating in the calculation belong to the same group and the topological sorting solving can be performed simultaneously. For the countercurrent flow caused by gravity and capillary forces, the directed cyclic graph (DCG) is constructed according to the potential energy of the grids, and then the Tarjan algorithm for searching the connected components is utilized to find the groups composed of the coupling grids. Treating each group of the coupling grids as one element, a new graph can be constructed to obtain a directed acyclic graph (DAG). Finally, the parallelization for the topological sorting solution of the saturation is achieved.

With the rapid development of the road system and the increase in vehicle velocity in China, the vehicle collision risk of the frame building located on the road sides is also increasing. Ultra-high performance concrete (UHPC) has been increasingly applied to frame structures to improve its service performance due to its ultra-high material fracture energy and tensile strength. The UHPC frame structure is also subject to high vehicle impact risk. In this paper, high-resolution vehicle collision models against the three-layer normal concrete (NC) and ultra-high performance concrete (UHPC) frame structures are established and Ansys/LS-DYNA is used to conduct nonlinear dynamic finite element analysis. The material parameters and the contact algorithm are verified against the previously reported drop-weight impact test of NC and UHPC beams. Based on the high-resolution vehicle collision model, the NC and UHPC frame structures are comprehensively compared in terms of three aspects, i.e., the structural damage, the impact force characteristics and the energy dissipation mechanism. The main conclusions are as follows: (1) The anti-vehicle impact resistance of UHPC frame structure is much higher than that of NC frame structure. The damage of UHPC frame structure only exists in the impacted column, and the concrete in other parts is almost not affected. (2) Under the condition of high vehicle speed (80-120 km/h), the damage mode of NC column is severe punch shear damage accompanied by obvious plastic deformation, and the frame joints exhibit obvious tensile and shear damage. There is no tension area on the back of the UHPC column, which eventually develops into a punch shear failure through the section of the frame column. (3) The internal energy of concrete of NC column is higher than that of UHPC column, resulting in more serious damage of NC column than that of UHPC column. (4) When the vehicle bumper and engine impact the frame column, the first and second peaks of the impact force are produced, respectively. The peak impact force caused by the engine impact is much higher than that of bumper impact. The peak impact force of UHPC column is 22.6 % higher than that of NC column on average, and the maximum impact force difference between UHPC column and NC column is 32.1 %. The results of this paper are beneficial for the rational design of UHPC frame structure for impact resistance and ensure its safe and healthy operation.

In this paper, a semi-analytical model of the double-lap structure of composite laminates considering joint clearance is established to study the influence of geometric variations on the distributions of bolt load and stress field. Firstly, a representative bolt/hole unit is extracted from the typical composite joints, and a local stiffness model of the bolt/hole unit considering random geometrical variation and contact state is established. Secondly, based on Reddy's high order shear deforamtion plate theory, the finite element model of composite laminates is established to extract global structural stiffness matrix. Finally, by combining the local stiffness model of the bolt/hole unit with the global stiffness model of laminates, an assembly mechanical analysis model of multi-bolt composite joints is established that takes into account bolt/hole clearance and hole tensile deformation. The validity and accuracy of the model are verified by comparing it with 3D finite element simulation results. Numerical simulation results with random clearances show that a certain bolt clearance can lead to a more even bolt load distribution, providing theoretical guidance for the hole arrangement design of multi-bolt joints.

Graphene origami metamaterial has characteristics of negative Poisson's ratio, which can effectively improve the buckling resistance of the structure, and has a wide range of application potentials in aerospace and other engineering fields. In this paper, the graphene origami metamaterial beam is taken as the research object. Based on the principle of virtual work, according to the Euler beam theory and von-Karman's nonlinear strain displacement relationship, the nonlinear governing equation of the beam's buckling behavior under the in-plane load is established. The critical load of the buckling behavior of graphene origami metamaterial beam is calculated using the asymptotic numerical method, and the correctness of the theory and the algorithm in this paper is verified by comparing with the results in the published literature. Finally, the influences of graphene origami distribution, content, folding degree and boundary conditions on the nonlinear buckling behavior of graphene origami metamaterial beam structure are analyzed. The results show that the buckling critical load of the structure is the largest under the fixed boundary condition at both ends. The buckling critical load increases with the increase of graphene and graphene content on the surface of the structure, while decreases with the increase of folding degree.

In view of the shortcomings of the finite element method to study the mechanism of flap incision closure, such as long time and strong expertise demand, this paper proposes a rapid prediction method of donor area closure stress and postoperative skin protrusion height based on neural network and finite element simulation. Firstly, a hyperelastic finite element model considering the longitudinal profile structure of the donor tissue was constructed, and mechanical simulation analysis was carried out for the incision closure of different geometric sizes and different tissue thicknesses, and a neural network dataset was established. A simulation test platform for notch closure was established, and digital image correlation (DIC) method was used to verify the reliability of the finite element model. Then, with the dataset of closed simulation results as the input, three models of BP (Back Propagation), RBF (Radial Basis Function) and EBF (Elliptic Basis Function) were trained and optimized, and the prediction model of cut closure was constructed. Finally, the prediction model was used to expand the sample data and the Sobol sensitivity analysis method was used to explore the influence of input parameters on the incision closure. The results showed that the EBF neural network has the best effect and could effectively predict the closure result of incision. The length of the short and long axis of incision have the greatest effect on the closure result, followed by the thickness of skin and the thickness of fat. At the same time, this paper analyzes the effect of different parameters on the closure effect, and provides a reference for the donor area suture surgery.

Piezoelectric composite materials are widely used in underwater acoustic engineering, medicine and ultrasonic testing because of their high electromechanical coupling coefficient and piezoelectric constant, low density and high acoustic impedance. The Hashin-Shtrikman variational principle can predict the bounds of the effective modulus of composite materials, which is beneficial for the optimization of the piezoelectric composites. At present, the Hashin-Shtrikman bounds method for piezoelectric composites is suitable for ellipsoidal inclusions without considering the distribution of inclusions, but is not suitable for non-ellipsoidal inclusions. In this paper, based on the Hashin-Shtrikman variational method, the bounds of the effective modulus of transversely isotropic piezoelectric composites are solved by using the microstructure parameters reflecting the distribution characteristics and the shape of inclusions. This method is suitable for inclusions of any shape. When the ellipsoidal domain shape is the same as the ellipsoidal inclusion shape, this method is consistent with the traditional method for the bounds of Hashi-Shtrikman of piezoelectric composite materials. When the shape of the ellipsoidal domain is different from that of the ellipsoidal inclusion and the inclusion content is low, the bounds of the partial effective modulus obtained by this method are more compact. In addition, the bounds of the effective modulus of the transversely isotropic piezoelectric matrix containing square inclusions are calculated. The results show that the material is transversely isotropic and has little difference with the bounds of the effective modulus of the ellipsoidal inclusion. In this paper, the calculation method of the bounds of piezoelectric composites considering inclusion distribution and inclusion shape is established, which provides reference for the study of piezoelectric composites.

Composite beams have a number of excellent properties such as high strength, light weight, strong corrosion resistance, strong temperature resistance and strong fatigue resistance, and are widely used in engineering such as wind turbine blades, helicopter propellers, etc. Based on the vibration equations of a rotating composite thin-walled beam in the hygrothermal environment, the torsional motion of the beam was studied. The solutions of the eigenvalue equations were derived using the Rayleigh-Ritz method. The influences of temperature, moisture, rotating speed, mounting angle, ply angle and other factors on the frequencies and mode shapes were analyzed. The accuracy of the calculation results was verified using the finite element method. The results show that the first two frequencies decrease with the increase of temperature and humidity. And compared to humidity, temperature has a more significant impact on frequencies. For the conditions of T = 325~425 K and the ply angle of 15°~30°, the influence of temperature on the frequency is slightly smaller. For the ply angle around 0° or 90°, the humidity has little effect on the frequencies. In addition, the frequencies increase as the rotational speed increases or the mounting angle decreases. The ply angle has a significant influence on the frequencies. It is also found that temperature, moisture, rotational speed, ply angle and mounting angle have little effect on the modal shape of the first two modes.

A mesoscopic finite element model of fiber reinforced polymer (FRP)-concrete single shear test is developed considering the roughness of the concrete surface, and taking the concrete as a composite composed of mortar and aggregate. In order to describe the damage failure process of FRP-concrete interface in single shear test, the plastic damage model and linear elastic model are, respectively, used to simulate the mechanical behaviors of the two phases of concrete and FRP. To reveal the influence of concrete surface roughness on the failure process of FRP-concrete single shear test, two-dimensional random rough surfaces with root mean square height of 0.4 mm and 0.8 mm are generated. The results show that the established mesoscopic finite element model can effectively simulate the damage failure process of FRP-concrete interface in the single shear test, and the obtained load-displacement curve and failure mode are in good agreement with the test results. With the increase of the surface roughness of concrete, the effect of mechanical interlocking between epoxy resin and concrete surface increases, and the load-bearing capacity of the FRP-concrete specimen also becomes larger.

The reliability of pin solder joints on vehicle-mounted power module under the combined effects of heat generated by power loss and random vibration caused by road bump was explored. Fatigue life simulations of pin solder joints under electric-thermal-solid coupling were performed using the multi-physics field finite element models. The stress distribution and fatigue damage of the random vibration response were obtained for both elevated and normal temperature conditions. Furthermore, theoretical fatigue lives were also predicted and contrasted using empirical-based Dirlik model and Miner linear cumulative damage rule. The results show that the vibration fatigue life of solder joints decreases significantly considering electric-thermal-solid coupling effect due to the decrease of local constraint rigidity and the increase of vibration stress of solder joints, nevertheless still meets the specified vibration requirement. Finally, the accuracy of analysis results and the reliability of structural design were verified through conducting the vibration failure tests under full-power heating condition.

Subsurface crack initiation is one of the primary damage modes for materials under rolling contact fatigue. A crystal plasticity model combined with the cohesive zone elements is used to simulate the subsurface fatigue crack initiation at original austenite grain boundaries in a high strength steel. Based on the cohesive zone model of damage initiation criterion and fatigue damage evolution law, the damage accumulation with the number of cycles was calculated utilizing the crystal plasticity model in conjunction with the USDFLD subroutine. The fatigue crack initiation in the Voronoi model is simulated, and the effect of the crystal orientation on the crack initiation is investigated. The results indicate that the crack initiation is dominated by the shear stress, and the initiation position is within the range of maximum shear stress. The simulation results are consistent with the experimental observations. The grain orientation has a significant impact on the crack initiation location.

Internal-pressure tube with axial crack under thermal shock would generate thermal stresses, which caused the change of the stress field, as well as the change of the plastic extreme internal pressure. The transient temperature and stress fields in an ultrahigh-pressure polythene reactive tube with defects on the outer wall under thermal shock are simulated by the finite element method. Using the extended finite element method, the contour diagram of stress field near the crack tip during the crack propagation process is obtained. The plastic failure pressure obtained only under the internal pressure is compared with that predicted from the PCORRC criterion, to verify the effectiveness of the finite element model and the adopted damage failure criteria. In the thermal-mechanical coupling field, the transient stress of the elements at the crack front and the ultimate pressure of the reaction tube are analyzed. It shows that the transient temperature has a significant impact on the load-bearing capacity of the structure. Moreover, the self-strengthening effect of the inner wall of the tube under the thermal shock makes the reaction tube with external cracks more prone to plastic failure.

For body-centered cubic (BCC) gradient lattice structure composed of linearly variable cross-section struts, distribution of bending moments was derived. Applied to the Timoshenko beam theory, a parametric theoretical prediction model for the mechanical properties of gradient lattice structure was obtained. Using the hexahedral solid elements, the finite element models of the unit cells and the gradient lattice structure were established. Finite element analyses (FEA) were performed to verify the effectiveness of the theoretical model. For the gradient lattice structure, 3D printing technology was used to fabricate the test samples using 316L metal powders. The quasi-static compression mechanics tests were carried out, and the FEA under the same working condition was also conducted. The results verified the suitability of the Timoshenko beam model to investigate the mechanical characteristics of gradient lattice structure up to the aspect ratio of 10. Finally, the influences of varying aspect ratios, cell sizes, cell numbers, and gradient directions on the mechanical properties of gradient lattice structures were discussed. The results show that the bending moment distribution predicted by the proposed model is more accurate and with much reduced error for the bending struts with linearly variable cross-sections. Using the theoretical prediction model proposed in this paper, the relative errors of the equivalent elastic moduli of the BCC unit cells of variable cross-section and the gradient lattice structure are within 3 % for the aspect ratio range of 3.5~8.7.

The JH2 model is widely used to simulate the dynamic behavior of brittle materials, but there are some issues in its strength criterion and damage definitions. Therefore, an improved JH2 model is proposed in this paper for modeling the rock material under the blasting impact loads. First, the initial yield surface and nonlinear damage scale factor are added to the strength model, the tensile and compressive damages are treated asymmetrically, and the volume plastic strain is introduced into the compression damage. After the implementation of the model into LS-DYNA material subroutine, a series of simulations are carried out for the element tests, split Hopkinson pressure bar (SHPB) dynamic splitting tests, and rock blasting tests. The results show that the improved JH2 model overcomes the limitations of the original JH2 model in damage evolution of tension-compression asymmetry, nonlinear strain hardening behavior, Lode angle effect and volume behavior, which verifies the accuracy and application potential of the improved JH2 model.

The construction of tunnels underpassing existing pipelines is prone to cause pipeline deformation and damage. In order to predict the deformation of pipelines during tunnel underpass construction, and take timely measures to control the pipeline deformation, it is important to propose a pipeline deformation prediction method. Taking a large cross-section river crossing tunnel in Shanghai as the engineering background, a numerical model of shield tunneling underpassing existing pipelines was established. The influences of tunnel diameter, pipeline diameter, net distance between pipelines and tunnels, and pipeline burial depth on pipeline deformation during the tunnel tunneling process were quantitatively studied, and a multi-factor coupling formula was obtained for the influence of tunnel construction on pipeline settlement. After the tunnel underpassing is completed, the settlements of the pipeline and the surface both show a pattern of large in the middle and small on the sides. The maximum settlement of pipeline increases linearly with the increase of the tunnel diameter and the existing pipeline diameter, and decreases linearly with the increase of net distance between pipeline and tunnel. When the pipeline diameter is less than 0.5 m, the impact on the pipeline deformation is relatively small. A fitting formula has been proposed to describe the quantitative relationship between the pipeline settlement and the three influential factors for the estimation of tunnel underpassing pipelines, to provide an intuitive reference for similar projects.

Tornado has the characteristics of small scope of action, short duration and high intensity of action, and is the most frequent and destructive disaster in natural disasters. Due to the danger and the randomness of occurrence of the tornado, the field data is scarce and it is difficult to obtain complete wind field in the field measurement. In view of this, a data fusion method based on neural network model is proposed to realize the fusion of wind field data from different sources. The prediction effectiveness and the generalization ability of the model are verified. On this basis, the tangential velocity field of tornado is predicted. The results show that the average error of the driven model of measured data is more than 35 % in the forecast of tornado with low swirl ratio, while the average error of the driven model with data fusion is less than 14 %, which indicates that the fusion model has better prediction accuracy. In the prediction of tornadoes with high swirl ratio, the average error of the measured data-driven model is about 28 %, while the average error of the data fusion driven model is less than 10 %, indicating that the data fusion model still maintains high precision and has good generalization when predicting high swirl ratio. In the reconstructed fusion model, the vortex core of the low vortex ratio wind field is fractured, and the wind speed in the core area of the high vortex ratio wind field is significantly increased, and the coverage of the near-surface wind speed is also increased. The model can obtain wind field data near the ground and near the vortex core center, and improve the spatial resolution of wind speed in tornado field, providing important support for the improvement of structural wind resistance in tornado environment.

Strut-and-tie model method is one of the standard methods for designing reinforcement in complex reinforced concrete structures. It is very important to construct the strut-and-tie model in complex stress regions using topology optimization. The algorithms of Solid Isotropic Microstructures with Penalization (SIMP) and Evolutionary Structural Optimization (ESO) have been widely used in such studies. These algorithms are optimized for isotropic perforated plates of unit thickness, the essence of which is to seek approximate solutions near the optimal solution. In addition, existing methods rarely consider the effect of different material tension-compression properties on the optimal topology due to the difficulties caused by the unsmooth character of the constitutive curve. A topology optimization algorithm based on a truss-like continuum with bi-modulus materials is proposed to construct the optimal topology of the strut-and-tie model. The density and orientation of the orthogonal trusses at each node are considered as the design variables. The material properties in the tension and compression regions are consistent with the tensile modulus of the reinforcement and the compression modulus of the concrete, respectively. A material substitution scheme is introduced to overcome the non-linearity caused by the bi-modulus, and a correction formula for stiffness matrix is given. The optimization is achieved through an iterative algorithm based on sensitivity information. Numerical examples show that differences in elastic modulus significantly affect the optimal topology. Compared to the density-based optimization methods, the proposed algorithm is able to accurately describe the optimal material distribution field under complex stress states, with the computational efficiency imporved by about 26 %. Besides that, more details of the material distribution can be given. The algorithm is able to improve efficiency and accuracy while giving more design details.

The SiC composite cladding, composed of the monolithic SiC and the SiCf/SiC composite, has emerged as a leading structure for accident tolerant fuel cladding due to its exceptional thermodynamic properties and radiation resistance. Ensuring the structural integrity of the SiC composite cladding is crucial for reactor safety. In this study, the irradiation effects of monolithic SiC and SiCf/SiC composite were considered. Numerical simulation of the thermo-mechanical coupling behaviors of the SiC triplex composite cladding during a loss of coolant accident (LOCA) of the light water reactor after 1 146 days of safe operation was carried out. The distribution and evolution of the first principal stress of the monolithic SiC was obtained and the influencing factors were analyzed. The results show that in the early stage of LOCA, the first principal stress of the monolithic SiC increases rapidly, then slowly increases and finally decreases, with a risk of cracking. The decrease in coolant pressure is an important reason for the initial increase of stress of the monolithic SiC, while the increase in internal pressure and the damage of the SiCf/SiC composite, are the dominated reasons for the later increase of the first principal stress of the interior monolithic SiC layer. In the steady-state condition, there is a significant temperature difference along the radial direction of the cladding. The thermal stress caused by the decrease in the temperature difference in the early stage of LOCA also has a significant impact on the maximum stress of the monolithic SiC. It is feasible to reduce the failure risk of the SiC composite cladding by improving the thermal conductivity of the SiCf/SiC composite.

Debris flow is one of the main geological disasters in mountainous areas, which causes seriously damages to bridges in mountain areas. During the flow process, the debris flow is significantly affected by the water content, leading to possible variation of its constitutive model. In this paper, the factor of water content is introduced into the Herschel-Bulkley model of mud, and a constitutive model of mud flow material under the simultaneous changes of mass water content and shear rate is proposed. The model is compared with the rheological experiment of Chengdu clay mud to verify its correctness. Then, based on the Navier-Stokes equations of two-phase fluid, the material model is applied to the three-dimensional fluid-structure coupling analysis of the impact of the mud flow on the pier column. The applicability of the model was confirmed by comparing the calculation results with the relevant standards and the empirical formulas of impact pressure in the literature.

The aero-engine blade disc works in the harsh environment of high temperature and high speed, which affect the mechanical behavior of the coating contact of the discontinuous blade-disk interfaces and the overall dynamic properties. In this paper, based on the three-dimensional elasticity theory, a contact model based on a multilayer half-space body is developed to investigate the contact responses between rough surfaces of multilayer structures. First, rough surface topography is decomposed into micro, mesoscopic and macro multi-level geometric profiles by explicit expression. Then, based on the Papkovich-Neuber potential function (P-N potential function), Fourier integral transform method and the influence coefficient method, a boundary constraint model for the multilayer contact problem is constrcuted, and is solved using a conjugate gradient algorithm. Finally, the reliability of the model is verified by comparing it with the analytical solution and the finite element results. Furthermore, a parametric study is performed to investigate the influcences of elastic modulus, Poisson's ratio and friction coefficient on the stress and displacement fields. This work provides a feasible and effective approach to study the contact response of rough interfaces of the coating systems.

Chiral metamaterials can achieve unique properties different from those of conventional materials through the design of special structures. The aim of this paper is to discuss the effect of the metamaterial layers on the impact loads in water entry problem. The mechanical properties of ATH (Anti-Tetrachiral Honeycomb) were simulated by nonlinear constitutive model. The effects of the constitutive relationship on water entry process were examined. It is shown that both the plateau stress and the densification strain of the material have large influence on the load of water entry impact. When the plateau stress is high, the material properties are close to those of conventional materials. The decrease of the plateau stress and the increase of the densification strain can prolong the duration of impact loading and reduce the peak impact force applied on the material.

In order to address the problem of low shear strength of shallow slope soils, unconsolidated undrained (UU) triaxial tests were carried out on natural palm fiber reinforced soils to study the effect of different combinations of reinforcement conditions on the strength characteristics of soil and its reinforcement mechanism. Different fiber admixtures of 0.35 %, 0.55 %, 0.75 %, 0.95 % and fiber lengths of 5 mm, 10 mm, 20 mm and 30 mm were investigated. The test results showed that mixing palm fiber into powdered clay soil can significantly improve the strength and deformation resistance of the soil. The ultimate principal stress difference reaches maximum for the fiber admixture of 0.75 % and the fiber length of 20 mm, with the value increased by 172.9 % compared with the plain soil.  The internal friction angle is less influenced, with difference within 3°. From the SEM scanning electron microscopy observation of the palm fibers, it is found that the grooves on the surface of palm fibers can increase the interfacial friction and interlocking effect between fibers and soil particles, thereby improving the shear strength indicators of the soil.

During the construction and operation of tunnels, engineering challenges associated with seepage flow are consistently encountered, such as the damage of support structures or water influx. The main objective of this study is to analyze the hydraulic behavior of supported tunnels constructed in saturated ground, taking into account anisotropy of permeability and the effect of grouting/support on the seepage flow. In the determination, the coordinate transformation and the conformal mapping technique are employed to solve the governing equations, meanwhile, the points matching method is used to address the coordinate conditions of pore pressure and water flux at the rock-support interface. Finally, semi-analytical solutions of pore pressure distribution subjected to steady flow state are obtained, for the surrounding rock and the grouting/support zone. In the verification step, satisfactory agreement is achieved between the proposed analytical solutions and the numerical predictions. Then, in the parametric analyses step, the developed analytical model is applied to investigate the effect of support permeability, anisotropy of rocks' permeability, and the thickness of the grouting/support zone, etc., on the seepage flow and the pore pressure distributions of tunnels.

The labyrinth side weir has a large discharge capacity. It is widely used in flow control, farmland irrigation and drainage systems. In order to study the complex hydraulic characteristics for the triangular labyrinth side weir, the variation law of the discharge and the factors affecting the discharge, in this study we firstly carry out the numerical simulations regarding the hydraulic performance of a labyrinth side weir in 15 working conditions based on FLOW-3D software and RNG k-ε turbulence model. Its purpose is to obtain the hydraulic characteristics such as water surface flow pattern and velocity distribution of the side weir. Secondly, the dimensionless parameters affecting the discharge coefficient Cd of the labyrinth side weir are derived by Buckingham π theorem. Then the change rule between the Cd and the dimensionless parameters is explored. Finally, the calculation formula for discharge is obtained by developing artificial intelligence algorithm Genetic Programming (GP). The results show that the water in the main channel is in tranquil flow. When the weir crest angle θ is small, the secondary flow changes the flow pattern and direction of the water surface. The flow velocity changes sharply at the position close to the side weir, and vortexes occur inside the side weir. With the increase of θ, the water tongue above the side weir changes from symmetric distribution to the right side leakage, and the backflow inside the side weir gradually disappears. Cd decreases with the increase of the upstream Froude number (Fr) and the ratio of the overflow front to the upstream water depth (l/h1), and increases with the increase of the ratio of the weir height to the upstream water depth (p/h1). The greater the θ, the greater the change of Cd. The model evaluation results show that the calculation formula has the determination coefficient R2 = 0.913 and the root mean square error RMSE = 0.045. Moreover, the predicted discharge coefficient Cd has a great fitting consistency with the experimental scatter diagram, with the data points evenly and symmetrically distributed around the fitting line. It shows that the results of GP algorithm are sufficiently accurate and can meet the accuracy requirement of the flow measurement in irrigation district. This work can provide theoretical basis and technical support for the application of labyrinth side weir in practical engineering.

The galloping of iced transmission lines seriously threatens the safety and stability of the operation of the power system. However, due to the randomness of the ice shape and the wind, there is currently no practical way to establish a mathematical model of actual iced conductor galloping. Based on the data-driven sparse recognition algorithm, this paper proposes an identification method for the galloping model of iced quad bundle conductor under random wind loading. Firstly, the dynamic partial differential equation of the iced quad bundle conductor is derived based on Hamilton's principle, and then the Galerkin method is used to obtain the dynamic differential equation of the iced quad bundle conductor. The random wind aerodynamic model generated by the Davenport spectrum and processed by the linear interpolation of the sub-segments is introduced, and then the galloping equation model of iced quad bundle conductor with time-varying wind speed is obtained. Finally, combined with different data processing methods, the sub-segment linear interpolation integral recognition method and the sub-segment linear interpolation differential recognition method are proposed, and applied to the iced quad bundle conductor galloping mean model recognition. Through 100 sets of computer experiments with an average wind speed of 10~30m/s, the recognition accuracy, recognition efficiency and recognition stability of the two methods were explored and compared. The results show that with the change of average wind speed, except for the displacement cubic term, the two methods have good recognition accuracy for the iced quad bundle conductor galloping mean model. From the viewpoints of relative error of response, recognition accuracy and stability, and recognition efficiency, the differential recognition method is better than the integral recognition method, especially for the primary term and the third term coefficients of velocity. The results in this paper can provide reference for the establishment of transmission line galloping model.

Using the "symplectic superposition" method in the Hamiltonian system and based on the theory of elastic thin plates, an analytically study was carried out for the static problem of rectangular thin plates with mixed boundary conditions of constraint on two opposite sides and middle-constraint ends-simplely-supported on the other two sides. Firstly, based on the Hamiltonian system, the symplectic geometry method was used to analytically solve the problem of classical boundary condition of simply supported edges. Then, based on this solution as the basic system, the superposition method was used to solve the case of complex mixed boundary condition of constraint on two opposite sides and middle-constraint ends-simplely-supported on the other two sides. Finally, the correctness and convergence of the proposed method were verified using the finite element numerical simulations. The method presented in this paper has both advantages of the rationality of symplectic geometry and the regularity of superposition method. During the solving process, there is no need to assume the form of the solution in advance, and the analytical solution is obtained directly from the basic equations of elasticity through strict step-by-step derivation. This method has strong generality and can be used in some rectangular plate problems that are difficult to solve analytically using the traditional methods.

The change of water gap in fuel assembly caused by fuel assembly vibration has an important influence on the power fluctuation in the reactor. In order to study the behavior of fuel assembly vibration and water gap variation, fuel assembly vibration analysis model is established according to fuel assembly structure and its vibration characteristics, and fuel assembly vibration analysis software FAVA is developed. Firstly, the fuel assembly vibration analysis model is validated by comparing with the commercial finite element software Abaqus. Secondly, by analyzing the change of water gap caused by fuel assembly vibration, the fuel assembly vibration frequency calculated by FAVA software is compared with the core power fluctuation frequency, which shows that the core power fluctuation is mainly caused by the fuel assembly vibration. Finally, the influence of stiffness change of fuel assembly on the vibration is analyzed.

A shear force sensor is designed and manufactured using a flexible microtubule liquid metal sensor as the stress measurement element. The shear force sensor consists of an elastic PDMS (polydimethylsiloxane) member, a metal support gasket, and a flexible microtubule sensor. The working principle of the shear force sensor and the sensing mechanism of the measuring element are discussed. The shear force sensor is used to measure the shear angle of the PDMS truss members, and the measurement results are compared with the reference values measured by the gray weighted centroid method. The effects of the assemble clearance δ and the microtube arrangement distance L on the measurement accuracy are systematically analyzed. The results show that when the elastic PDMS member is used as the deformation unit, the shear force sensor can work effectively in the shear angle range of 0.004 7 rad~0.038 rad. The measurement error increases with the increase of the assemble clearance δ, and decreases with the increase of the microtubule arrangement distance L. The proposed shear force sensor has the advantages of high sensitivity and strong anti-interference ability, providing a new tool for the measurement of shear force.

In order to enhance the precision of structural damage detection, a two-stage approach consisting of first-localization and second-quantification was proposed, which utilizes the cross-model modal strain energy changes (CMSEC) instead of the conventional modal strain energy changes (MSEC). In contrast to the conventional approach of calculating modal strain energy (MSE) solely based on the damaged mode shapes, in the cross-model modal strain energy (CMSE) method, the energy considering both the pre-damage and post-damage mode shapes is computed simultaneously. Initially, CMSEC was utilized to develop a damage indicator, known as CMSECI, for identifying the damage locations. Once the potential damage elements are selected, CMSEC was then used to establish the sensitivity equations needed for damage quantification. To circumvent any ill-posed equation issues that may arise during the iterative process, a singular-value truncation-based strategy was implemented to solve the equations. By analyzing the mathematical equations, it can be concluded that CMSEC is less susceptible to noise compared to MSEC. The example of a simply supported beam demonstrate that the two-stage CMSEC approach is more effective in accurately detecting and quantifying the structural damage compared to the conventional method. To further demonstrate the superiority of the proposed approach, the Monte Carlo method was employed to provide a macroscopic view of the relative error upper bounds and a detailed examination of relative error distributions.

In order to investigate the performance behaviour of concrete under the coupled effects of fatigue and freeze-thaw, the fatigue phase field method was used to investigate the performance evolution of concrete. The concrete aggregate model with certain area fraction and with interfacial transition zone (ITZ) was obtained by random aggregate placement algorithm. A numerical simulation of the entire process of concrete freeze-thaw fatigue cracking was conducted by introducing a thermo-mechanical coupled fatigue phase field model. The results show that during the freeze-thaw cycles, damage starts at the interface transition zone with the highest stress level at the aggregate corner. Under the condition of freeze-thaw, the damage development in the early stage of freeze-thaw is relatively slow, and the damage starts to develop rapidly in the later period. Under the condition of combined freeze-thaw cycles and fatigue, the durability of concrete is greatly reduced, and the life is only 50 % of that under pure freeze-thaw conditions. With the increase of the cycles of freeze-thaw, the concrete strength, modulus of elasticity gradually decrease, with the decrease rate gradually increasing.

Increasing the outlet flow rate of an atomization nozzle can increase the liquid exit velocity, leading to smaller droplets and enhanced atomization efficiency. In order to suppress the cavitation effects and achieve a larger outlet flow rate, this paper establishes a numerical model of the internal flow field in the nozzle structure to analyze the flow field information such as velocity, liquid phase volume fraction, and turbulence kinetic energy distribution. Based on the mechanism of cavitation generation, several improvement schemes for the nozzle structure are proposed: reducing the nozzle length, adding nozzle chamfers, and decreasing wall surface roughness. These approaches can effectively reduce the cavitation effects, significantly increase the nozzle's outlet flow rate, and improve the atomization performance, providing reference for the optimization of nozzle structures.

Because of its advantages of good development foundation, short design cycle, compact structure and strong fuel adaptability, the aero-derivative gas turbine has been widely used in the field of offshore oil and gas platform, marine power and pipeline transportation, etc. For the aero-derivative gas turbine blades working in high temperature, high pressure and other harsh environments, creep is one of the main failure modes. In order to ensure the operation reliability of the blade, nickel-based alloy with strong creep resistance is usually selected as its constitutive material. The nickel-based alloy has obvious third stage of creep, occupying a relatively high proportion of its whole life. The current creep damage constitutive model is difficult to accurately characterize the failure behavior of the third stage of creep for the nickel-based alloys. In response to the above problem, a creep damage constitutive model which can reasonably describe the third stage of creep of the high temperature materials is proposed in this paper. The model is validated by comparing with the creep experimental data under different temperatures. The proposed model can provide a theoretical guideline for accurate life prediction and reliability design of the high temperature components of aero-derivative gas turbines.

The cracking and damage of electrode composite active materials in lithium-ion batteries have significant negative impact on the battery's capacity and cycling performance. Choosing suitable binders and material formulations to improve the bonding strength of the active materials is crucial for the long-term cyclic use of batteries. However, measuring the fracture strength of composite active materials at the electrode scale is challenging. In this paper we propose a quantitative method for testing the fracture performance of electrode composite active materials based on the peeling experiment of porous current collector electrodes. By comparing the peeling experiments of porous and non-porous current collector electrodes, the peeling strength of the composite active materials is obtained based on different open area ratios of the current collectors. The study further verifies through experiments that the measured peeling strength of the composite active materials is independent of the geometry of the current collector openings. Finally, the peeling strength of graphite negative electrodes prepared with two commercial formulations is measured, yielding reliable results. This experimental method can measure the energy release rate of composite active materials during the stable fracture, characterizing the material's bonding strength, and is of significant importance for the preparation and numerical simulations of related electrode materials.