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.

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.

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.

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.

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.

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.

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.

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.

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.

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 combined elastic rimless wheel model is proposed, and the semi-passive walking of the combined elastic rimless wheel is realized by incorporating indirect control of periodic oscillation. The nonlinear behavior of chaos and synchronization is analyzed by observing the gait of the semi-passive walking of the combined elastic rimless wheel. Firstly, the dynamics model of the semi-passive walking of the combined elastic rimless wheel is established to enable stable periodic walking. Secondly, the stability of the limit loop is shown to be sensitive to the initial conditions by analyzing the typical gait of the semi-passive walking of the combined elastic rimless wheel. Finally, the relationship between the oscillation frequency and the system walking frequency and the phase difference between the oscillation frequency and the system walking are analyzed by observing the gait of the semi-passive walking of the combined elastic rimless wheel. Finally, by observing the semi-passive walking gait of the combined elastic rimless wheel, we analyze the relationship between the oscillation frequency and the walking frequency of the system, as well as the possible nonlinear behaviors such as synchronization and chaos between the phase difference of the two frequencies and the number of walking steps. The simulation results show that for the relationship between the oscillation frequency and the walking frequency of the system, the lighter oscillation mass and smaller oscillation amplitude lead to synchronization, and the heavier oscillation mass and larger oscillation amplitude lead to chaos. For the relationship between the phase difference of the two frequencies and the number of walking steps, the lighter oscillation mass and smaller oscillation amplitude lead to chaos.

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.

The evolution mechanism of rock strength is required for improving the accuracy and applicability of strength criteria calculation. Considering the fact that the energy conversion plays a dominant role in the physical process of material, and the effect of the elastic strain energy on the material failure, the influences of the confining pressure, the intermediate principal stress and Poisson's ratio on the strength evolution of rock material are studied. The results show that the rock failure is related to stress state and rock deformation characteristics. Noting that neglecting the influence of Poisson's ratio is the basis for the intermediate principal stress theorem, the confining pressure effect and the intermediate principal stress effect ignore the influence of deformation, which is inconsistent with the experimental results and is also the internal reason for the poor accuracy of the corresponding strength theory. The evolution of rock strength is the result of the combined actions of the confining pressure, the intermediate principal stress, and Poisson's ratio. Based on this, the material failure characteristics, the confining pressure interval, and the condition that the triaxial tensile strength is always larger than the triaxial compressive strength under the hydrostatic condition were studied. It is shown from the theoretical and experimental results that the strength theory, which reflects the effects of confining pressure, intermediate principal stress, and Poisson's ratio, has high computational accuracy and applicability. The results of this paper are of great significance for accurately describing the failure characteristics of rocks and establishing universally applicable strength theories.

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 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.

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.

Reflection of elastic waves at the interface of dipolar gradient elastic solids under the control of external magnetic field is studied in this paper. The microstructural effects become more pronounced as the incident wavelength is close to the characteristic length of microstructure or high frequency. Firstly, the dispersion equation of the elastic wave propagation is derived by the dipolar strain gradient theory and Maxwell electromagnetic theory. Then, the reflected-to-incident amplitude ratios of the P-waveand SV-wave incidences are calculated according to the interface conditions. Finally, the influences of the external magnetic field and the wavelength of the incident wave on the propagation of the reflected wave are discussed based on the numerical results. It is found that the microstructural effect can lead to the generation of new wave modes and the appearance of the dispersion characteristics of the elastic wave, while the external magnetic field only affects the velocity of the elastic wave propagation through the Lorentz force, but does not produce new wave modes and affect the dispersion properties of the elastic wave.

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.

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.

One cast-in-situ slab and four laminated slabs were tested to investigate the influences of the U-shaped bars and the bending height of the prefabricated floor bars in the laminated slabs. The crack development, failure mode, deflection, bearing capacity and steel strain of the test slabs were comparatively analyzed. The results indicate that the bearing capacity and deformation capacity of the laminated slabs with U-shaped bars are similar to those of the cast-in-situ slab, and dowel effects of the U-shaped bars limit the development of cracks along the laminated slope. After cracks appear at the root of the laminated area with 90° bending bars at the bottom of the prefabricated layer, the crack develops quickly along the laminated slope as the load increases, and the unfavorable position appears at the laminated slope, leading to the decrease of the bearing capacity and stiffness of the laminated slabs. The 90° bending bars at the laminated slope position reach the yield strength when the slabs fail, indicating that the bending design schemes in the bottom plate steel bars can make full utilization of the steel bars. Finally, design suggestions are given for the laminated slabs with 90° bending bars in the bottom of the prefabricated layer.

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.

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.

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.

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.