This paper aims to study the dynamic perforation response process, failure mode transition and energy absorbtion characteristics of ultra-high molecular weight polyethylene （UHMWPE）laminates against fragment-simulating projectiles (FSPs).

FE software ANSYS/AUTODYN is employed to establish a numerical model for fragment penetration resistance of UHMWPE laminates, and analyze the failure mode transition and energy absorbtion characteristics of the target plates.

The process can be roughly divided into two stages: the shear plugging stage and stretch deformation stage. The thicker the target plate, the greater the proportion of the shear plugging mode. When the thickness of the target plate is constant, with the increase in fragment penetration velocity, the proportion of the shear plugging mode becomes larger until it reaches a stable level. In the initial small range above the ballistic limit velocity, the energy absorbtion of the target plate is negatively related to the velocity of the projectiles. As the fragment velocity increases, the shear plugging range of the fiber fracturing enlarges, and the energy absorbtion of the targets increases with the velocity of the projectiles.

The effects of the thickness of the face plate, angle of the wall plate and height of the core layer on the anti-explosion performance of carbon fiber reinforced composite trapezoidal corrugated sandwich structures were investigated.

First, based on the 3D Hashin failure criterion, a subroutine module of the damage evolution of fiber reinforced composites is developed using the VUMAT user subroutine interface in ABAQUS. Second, through comparison with experiments in the public literature, the effectiveness of the dynamic response simulation method of carbon fiber reinforced composites based on a development subroutine under explosion impact loading is verified. Finally, a parametric study on the explosion resistance of carbon fiber reinforced composite trapezoidal corrugated plates is carried out based on the numerical method.

The results show that, compared with increasing the thickness of the blast face panel, increasing the thickness of the back blast face panel can improve the explosion resistance of the sandwich plate more obviously; when the folding angle of the core wall plate decreases from 45° to 30°, the explosion resistance increases by 1.3%; when it decreases from 60° to 45°, the explosion resistance increases by 6.3%; and when the core height increases from 8 mm to 20 mm, the explosion resistance increases by 27.7%.

This papers aims to analyze the impact resistance of honeycomb structure with different Poisson's ratio.

Based on the explicit dynamic finite element method, this paper analyzes the dynamic mechanical properties of honeycomb structures with different Poisson's ratios under in-plane impact load, and explores the influence laws of Poisson's ratios on their impact resistance. Three typical honeycomb structures with negative/zero/positive Poisson's ratios (reentrant hexagon, hexagon and semi-reentrant hexagon) are selected, their geometric parameters are changed to give them the same relative density and different Poisson's ratios (-2.76 – +3.63), and their dynamic mechanical properties under low/medium/high-speed dynamic displacement loads are analyzed.

The results show that the zero Poisson's ratio semi-reentrant honeycomb structure has the best structural stability without transverse deformation under compression deformation; without structural instability, the platform stress has little correlation with the Poisson's ratio; and the compact strain and total energy absorbtion increases with the absolute value of the Poisson's ratio. Negative Poisson's ratio honeycomb structures with large t/l and small θ are suitable for applications with high platform stress (strong deformation resistance), and negative Poisson's ratio honeycomb structures with small t/l and small θ are suitable for high total energy absorbtion applications, while zero Poisson's ratio semi-reentrant honeycomb structures are suitable for applications with high platform stress (strong deformation resistance).

The addition of thermoplastic phase materials between the layers of traditional marine composite laminates can effectively improve the impact resistance properties of marine composites. This study carries out experiments to explore the impact damage characteristics of such materials.

The thermoplastic/thermoset interface of laminates is observed with an optical microscope, and the bonding mode of the two-phase materials is analyzed. Composite laminates with different structures are impacted at low velocity with three different energies. The damage morphology of each specimen is observed via ultrasonic C-scan and electron microscopy to obtain the impact response and damage mechanism of each specimen.

The results show that marine composite laminates embedded with PEI film have better damage resistance than carbon fiber laminates. Under 8 J and 12 J of impact energy , the delamination damage is reduced by 19% and 39% respectively, and they showed better integrity after 12 J impact.

In order to improve the explosion and impact resistance of the protective structures of unmanned underwater vehicles (UUVs), autonomous underwater vehicles (AUVs), air bottles, etc., the structural response and failure modes of carbon fiber reinforced plastic (CFRP) cylindrical shells under underwater explosion and high hydrostatic pressure are investigated.

A computational model of CFRP cylindrical shell implosion under the combined action of hydrostatic pressure and impact load is established using ABAQUS software and the coupled Euler-Lagrange (CEL) method. The effectiveness of the numerical simulation method is then verified by comparison with the experimental results. On this basis, the failure modes and parametric effects of CFRP cylindrical shell implosion are obtained.

The underwater implosion of composite cylindrical shells can be divided into three stages: buckling, wall contact and failure propagation. Reducing the length-to-diameter ratio of the CFRP cylindrical shell can improve the impact resistance ability and affect the failure mode of the structure. With the increase in the number of fiber layers, the static water bearing capacity and impact resistance ability of the shell structure increase. With the increase in the impact block velocity, the wall boundary contact and failure propagation of the cylindrical shell become more obvious, matrix fractures occur more frequently and the cracks show an obviously increasing trend in the lengthwise direction of the cylindrical shell.

As composite materials have varied internal structures, an in-depth analysis of the damage mechanisms of their component materials can provide a research foundation for the ultimate strength analysis of composite stiffened panels.

The microscopic, mesoscopic and macroscopic mechanical analyses of marine glass fiber reinforced plastic (GFRP) composite stiffened panels are carried out using a multi-scale approach. Microscopic and mesoscopic representative volume element (RVE) models of chopped strand mat (CSM) and woven roving (WR) materials are established, and the macroscopic equivalent stiffness is obtained by homogenizing the RVE models. The ABAQUS VUMAT subroutine is used to code the progressive damage evolution model of the composite materials to derive the damage evolution mechanism of the microscopic and mesoscopic models respectively. The equivalent strength of macroscopic laminates is also obtained.

The multi-scale approach can be used to accurately evaluate the macroscopic mechanical properties of composite materials, and the ultimate strength of composite stiffened panels is mainly determined by fiber bundle failure.

To tackle the problem of the longitudinal strength of composite superstructures, the finite element analysis method is used to study their longitudinal bending characteristics and design requirements.

First, an analysis is made of the longitudinal strain distribution along the height direction of a simplified hull model with different lengths and the equivalent elastic moduli of superstructure materials, and the quadratic function is used to perform nonlinear fitting. Second, the design requirements of composite superstructures are proposed based on the fitting results and explained in terms of both structural size and material properties. Finally, based on the concept of bending moment effectiveness and national military standards, a superstructure method with different elastic moduli and lengths is proposed that fully participates in longitudinal bending determination.

The results show that glass fiber and carbon fiber reinforced plastic reach the longitudinal strength requirements of superstructures, and composite superstructures longer than 0.3 times the length of the hull should be included in section stiffness checks.

This paper aims to study the elastic wave propagation characteristics and vibration and noise reduction mechanisms of periodic ship sandwich plates.

To this end, the dispersion relation and flexural wave bandgap characteristics of lightweight sandwich plates are numerically investigated using the finite element method in combination with the Bloch theorem. The flexural vibration and sound transmission properties are analyzed to study vibration and sound reduction, and experimental validation is further conducted to verify the numerical results.

Lightweight sandwich plates can yield flexural wave bandgaps in a specific frequency range due to the Bragg scattering effect, resulting in flexural vibration isolation and sound insulation.

This paper aims to study the characteristics and calculation method of the vibration and sound radiation of single ring-stiffened cylindrical shells with porous fiber composite materials installed in the inner wall under acoustic excitation.

Based on the equivalent fluid theory model of Johnson–Champoux–Allard (JCA) and the transfer matrix of the multilayer medium, a theoretical formula of the sound absorption coefficient of multilayer sound absorption structures is derived. The three methods for calculating the vibration and sound radiation of a single ring-stiffened cylindrical shell with porous fiber materials under acoustic excitation, namely acoustic solid modeling of porous media, finite element model combined with theoretical formula and imposition of impedance boundary on sound absorption coefficient, are then verified and compared. Finally, the influences of sound-absorbing material's thickness, backed-air gap, static flow resistance, and material arrangement order on the acoustic absorption performance of the cylindrical shell are investigated.

The results show that laying porous fiber composite materials on the cylindrical shell internally can reduce the vibration and acoustic radiation of cylindrical shell structure. The sound absorption coefficient curve can quickly and effectively predict the resulting trend of the vibration and sound radiation of the cylindrical shell.

The purpose of this paper is to obtain the hydro-acoustic modulus of high-strength polyvinyl chloride (PVC) foam through an inversion algorithm based on the measured underwater acoustic insertion loss values of the composite samples, then improve the calculation accuracy of the insertion loss of the composites.

First, the static elastic modulus of high-strength PVC foam is obtained through mechanical tests such as compression and tension, and then the insertion loss of the sandwich composite is calculated using the transfer-matrix method. The reason for the large difference in the calculated values and the measured values obtained by the acoustic pulse-based tube method is that the input value of the elastic modulus of the core material is low. Based on the measured insertion loss values, the underwater acoustic modulus values of five PVC foam samples are then calculated via genetic algorithm inversion.

The quantitative calculation results indicate that the hydro-acoustic modulus value of high-strength PVC foam is higher than the measured static elastic modulus values. The average ratio of hydro-acoustic modulus to compressive modulus is 1.24, and that to tensile modulus is 1.36.

In order to investigate the influence of joints in composite laminate plates on the vibration transfer characteristics of structures, this study uses power flow based on the finite element method (FEM) and a related visualization technique.

First, a method that describes plate vibration by power flow in solid elements is proven to be feasible, then power flow transmission efficiency is introduced and a method of calculating it in a finite element model is proposed and verified by the admittance power flow method. Finally, two joint simulations of embedded joints and screw joints are obtained, as well as the power flow transmission efficiency curve and typical power flow vector diagram.

The results show significant differences in vibration transmission and power flow transmission efficiency between the two models.

In order to control the first longitudinal vibration mode of propulsion shafting systems, a dynamic vibration absorber with disc spring negative stiffness is proposed and its experimental verification carried out.

A test bench is established for the propulsion shafting system containing a dynamic vibration absorber with negative stiffness. According to the first longitudinal vibration mode of the shafting, a dynamic vibration absorber with negative stiffness integrated into the thrust bearing is developed. Vibration transmission tests under different rotational speeds, static thrusts and negative stiffness are then carried out, and acceleration response data on the thrust bearing foundation and shafting is obtained.

The results show that the developed dynamic vibration absorber with negative stiffness can achieve vibration suppression of 7.8 dB for the thrust bearing foundation in the first longitudinal mode of the propulsion shafting with a mass ratio of 1.6%, and the vibration control effect of the negative stiffness dynamic vibration absorber is maintained at 3.3 dB when the natural frequency changes by 5% and the thrust changes by 40%. The vibration response on the thrust bearing foundation and shafting do not deteriorate even at non-optimal negative stiffness.

In view of the insufficient safety and reliability of the traditional deterministic vibration analysis of ship propulsion shafting system, the vibration response analysis of the shafting system under uncertain excitation conditions is carried out.

Using non-random vibration analysis based on non-probabilistic convex model process, the uncertain excitation and vibration response are described in the form of the upper and lower bounds of the interval to reduce dependence on a large amount of excitation sample data. Compared with the calculation results in the relevant literature, the validity of the program for solving the response bound of the two-degrees-of-freedom (2-DOFs) system is verified, and the uncertain vibration problem of the shafting system is then explored on this basis.

The results show that when the shafting system is excited by [-30 N, 30 N] propeller laterally, a displacement response of the magnitude of about 10^-6 m is generated at the bearing. It is also indicate that the shafting system is excited in a certain interval, so a certain interval response must be produced.

The traditional method of marine propulsion shafting alignment calculation usually ignores the influence of the ship's wake field, causing a large deviation between the computational result of the propeller hydrodynamic force and the real value which results in a decline in alignment accuracy.

Taking a long marine shafting as the research object, a propeller-shafting-hull integrated finite element model and its wake field model are established, and the propeller hydrodynamic force is calculated using the CFD numerical simulation method. The fluid-structure interaction method is used to apply the fluid computing results on the propeller surface for shafting alignment calculation, and the influence law of the propeller hydrodynamic force on the shafting deflection curve and the state parameters of each bearing are obtained. On this basis, in order to solve the problem of excessive load difference between the four bearings at the end of the long marine shafting, a multi-objective optimization algorithm is introduced for alignment calculation.

When the propeller hydrodynamic force is considered, the deflection change of the shafting tail decreases. The closer to the propeller, the greater the influence of the bearing load, and the load value decreases with the increase of the advance coefficient. Comparing the alignment state of the shafting before and after multi-objective optimization, the load difference between the bearings is significantly reduced and the running state of the shafting is improved.

In order to analyze and solve the problem of the fault reconfiguration of shipboard power systems (SPSs), a fault reconstruction model with the optimization objectives of load loss and switching operation times is established, and an improved grey wolf optimization (GWO) algorithm is proposed.

Aiming at the deficiencies of the traditional GWO algorithm, a chaotic tent map is added; a cosine function is used to improve the convergence factor so that it maintains a large value in the initial stage, then decreases slowly and increases the attenuation rate in the later stage; non-dominated ranking and congestion calculation are added to improve the decision-making grey wolf selection strategy; and the grey wolf individual is discretized so that it can be used for reconfiguration.

The example of the network fault reconfiguration of a SPS shows that in the case of load and generator faults, the Pareto solution obtained by the proposed method is smaller than the improved differential evolution (DE) algorithm, improved particle swarm optimization (PSO) algorithm and improved genetic algorithm (GA), and has certain advantages in the optimal number of iterations; that is, its optimization speed.

To meet the efficient thermal management needs of electronic devices such as ships and underwater vehicles, this study focuses on the constructal design of a tree-shaped microchannel disc heat sink with wavy walls.

A design prototype of the heat sink with wavy walls is first proposed. Based on constructal theory, the amplitude and wavelength of the wavy walls are designed under the constraints of fixed heat sink volume and fixed microchannel volume by maximizing the comprehensive performance evaluation criteria (PEC) while considering both heat transfer and flow pressure drop.

The results show that the wavy walls increase the heat transfer surface areas and generate vortices in their cavities, effectively reducing the maximum temperature. When the inlet Reynolds number is fixed at 700, 900 or 1100 respectively, the maximum temperature is reduced by 13.5 K by increasing the amplitude of the wavy walls, while the pressure drop increases significantly; and the maximum temperature is reduced by 4.7 K by reducing the wavelength of the wavy walls, while the pressure drop increases slightly. There are optimal amplitudes that raise the comprehensive performance evaluation criteria to extreme values for given larger wavelengths, while the comprehensive performance evaluation criteria increase monotonously as the amplitude increases for given smaller wavelengths.

This paper carries out an experimental study of a multi-function dirllship model with moonpool structure in towing tank, aiming at analyzing the effects of the moonpool structure on the ship resistance in open and closure condition.

Taking a dirllship as the research object, the ship motion response in regular and irregular waves is investigated. The resistance of the ship in hydrostatic water and waves is measured with tension sensors, and the acceleration characteristics of the bow, midship and stern are analyzed by acceleration sensors.

The results indicate that hull resistance under light load conditions is greater when open moonpool, while hydrostatic water resistance with closed moonpool is greater under design load conditions. The closed moonpool in regular waves reduces stern acceleration by 58.2%, bow resistance by 46.7% and heave response by 41.8%. The peak of resistance at the bow in irregular waves is about ten times higher than that at the stern, and the peak of resistance occurs more often when the moonpool is open at the same time.

To ensure safety and prevent seabed collisions in complex unknown underwater environments, this study proposes a seabed safety domain model and tiered emergency response strategies.

A vertical motion simulation model is established and verified by surpassing the test results, then used to calculate the active and passive safety domain distance of an autonomous underwater vehicle (AUV), thereby establishing a seabed safety domain model. An AUV emergency control system and emergency strategies are then built on the basis of the dynamic safety domain model. The trim and distance from the seabed of the AUV are used to calculate the current and future risk factors. Based on the weighted sum, the comprehensive risk factor is employed to provide the AUV with emergency response strategies.

Lake tests with the AUV sailing at a fixed depth and height show a strong dependency of the comprehensive risk coefficient on seabed height when it is close to the boundary of the AUV's active safety domain. In the opposite case, there is a weak dependency of the comprehensive risk coefficient on seabed height. The results show that the proposed AUV emergency control system can reduce emergency false alarms caused by frequently changing riverbed heights and sailing altitudes close to the seabed. In such cases, reasonable emergency strategies can be realized under complex rough terrain.

Aiming at the current situation in which it is difficult to efficiently evaluate protection probability through traditional lightning rod evaluation methods, an efficient numerical evaluation algorithm is developed on the basis of an electrogeometric model (EGM) and attractive volume to realize the efficient calculation of lightning protection probability at any point in space.

This method first determines the attractive volume boundary of the lightning rod and protection object according to the interception process of the upward and downward leaders. The collection surface and exposure arc of the lightning stroke distance are then calculated, enabling the attractive risk and interception effect of the lightning rod to be quantified. Finally, the attraction and interception characteristics of the lightning rod are integrated to establish a numerical evaluation model of protection probability. To verify the accuracy of this method, the general rule of lightning rod protection probability is analyzed and the results compared with the existing analysis method.

The evaluation results of this method show good agreement with those of classical leader progression model (LPM) theory.

Aiming at the deficiency of the existing line impedance stability network (LISN) in the electromagnetic pulse protection capability, a LISN suitable for the pulse current injection (PCI) test of electrical and electronic equipment is proposed.

Aiming at the characteristics of high peak value and fast rise of the pulse current in PCI testing, the circuit structure and physical structure of the LISN are improved on the existing basis through PSpice time-domain and frequency-domain simulation combined with engineering design requirements, thereby giving it good nanosecond pulse protection performance and impedance stability at the same time. Pulse current protection performance test and impedance curve test experiments are then designed and carried out.

The experimental results show that the improved LISN can attenuate the injected pulse current by 60 times, while the error of its impedance curve is less than 5% compared with the Type 5 μH LISN in GJB 151B-2013.

Changes in attitude caused by sailing motion will lead to changes in the probability density of the radar cross section (RCS) of a ship. As such, it is necessary to master the influence degree of various motion conditions on the probability density of the RCS of a ship under grazing incidence.

Using the quasi-static method, a hydrodynamic and electromagnetic scattering characteristic co-simulation model and calculation process are constructed. A 10 GHz continuous wave at grazing incidence is selected as the radar detection wave threat, and the RCS probability distributions of the ship's body under different statistical times, sea states, speeds, headings and other parameters are compared and analyzed.

A lognormal distribution model is used to simulate the distribution characteristics of the static RCS of the ship model. The probability distribution of the dynamic RCS is basically stable when the statistical time is longer than 250 seconds. There exists a "burr" phenomenon in the dynamic RCS probability distribution curve under low sea states, following waves or beam sea drifting conditions.

Aiming at the problem of too many influencing factors and too little reference data for determining the dimensions of medium-sized cruise ships in the concept phase, a simplified multi-objective optimization method based on the fitting of dimensions and performance is proposed.

First, the dimension relations of medium-sized cruise ships are analyzed and the influence of the latest SOLAS requirements used to determine the optimization range. Second, the influence of cruise ship dimensions on space, resistance, stability and seakeeping are analyzed. Next, based on the principles of genetic algorithms, a multi-objective optimization algorithm with high robustness and high engineering adaptability is determined to establish a multi-objective optimization model for the concept design of medium-sized cruise ships. Finally, the Pareto solution obtained by multi-objective optimization is analyzed to provide initial references for determining the dimensions of the target cruise ship.

Implemented via a genetic algorithm, the optimization program proposed herein is applied in the concept design of a medium-sized cruise ship in order to optimize the initial dimensions, thereby achieving the expected outcome of providing reasonable initial dimensions for cruise ship design.

The purpose of this paper is to solve the vibration equations of a ring-stiffened conical shell using the analytical method, and to investigate the vibration characteristics of a ring-stiffened conical shell theoretically.

First, the ring-stiffened conical shell is processed in segments, and its displacement along the radial, circumferential and normal directions is written in the form of power series solutions respectively. The recurrence relations of the coefficients ahead of the power series are then derived in detail. At the same time, a beam model is used to simulate the influence of the number of ring-stiffeners on the vibration characteristics of the conical shell, and the boundary conditions, displacement, internal force matrices and ring-stiffeners of the conical shell segments are assembled and solved, thereby obtaining the vibration response of the shell under harmonic external excitation. Moreover, a comparison of the calculation results with those obtained by the ANSYS finite element analysis is carried out to verify the validity of the proposed method. Finally, the theoretical method is applied to analyze the vibration characteristics of the ring-stiffened conical shell theoretically.

The results show that installing ring-stiffeners on the conical shell can significantly suppress the vibration of the conical shell, which is manifested by the decrease in response amplitude, the increase in natural frequency, and the decrease in the number of resonance peaks within the same frequency band. Increasing the thickness of the shell can reduce the vibration response amplitude and increase the natural frequency of the ring-stiffened conical shell. In addition, increasing the half cone angle, axis length and the number of ring ribs can also reduce the vibration response amplitude of the ring-stiffened conical shell.

This study aims to explore the law of the critical compression stress of stiffened panels under the influence of in-plane shear load, and whether in-plane shear load combined with lateral pressure will introduce a strong coupling effect.

To this end, nonlinear finite element (FE) software ABAQUS is used to perform numerical simulation analysis under combined loads on a group of FE models. A limit state equation/curve is then derived from the dimensionless calculation results based on the minimum square error method.

The results show that the influence law of in-plane shear load on the critical compression stress of stiffened panels is clarified, and a limit state equation of stiffened panels that considers the effect of shear load is obtained.

The method of rewriting the element node information file to realize parametric modeling is commonly employed in existing structural optimization based on finite element (FE) strength calculation, but it remains difficult to consider variations of the profile number in hull section structure optimization. To this end, a container ship structure optimization method based on FE strength calculation is proposed using an artificial bee colony (ABC) algorithm and parametric FE modeling method.

First, the bee colony algorithm is written on the Matlab platform, and a script file which can generate the geometric model in its CAE module is established based on the ABAQUS kernel in the Python language. A Python script file which can submit the FE calculation and read the results is established. The geometric model is updated by rewriting the solution generated by the algorithm to the corresponding position in the script, then ABAQUS is called in the background and the script files are run in turn. Finally, the calculation results are returned to Matlab for verification, and the parametric geometric modeling and FE analysis are completed.

The feasibility of this method is verified by taking the section structure optimization of a 4600 TEU container ship as an example. It is found that the weight reduction of the container ship cabin structure reaches 18.7%.

It is easy to produce buckling distortion when welding thin plate butt joints, which affects the construction period, cost and performance, but this can be controlled by applying external restraints.

First, a butt welding test of a thin plate under external restraints is carried out, and the out-of-plane deformation is measured by the optical surface scanning method. At the same time, finite element (FE) models in a free state and external restraint state are established, and the thermal mechanical phenomena of the two models are subjected to thermal-elastic-plastic FE analysis (TEP FE). The influence of different external restraint distributions on the welding buckling distortion of the joints is then studied, and reasons for controlling welding buckling distortion are analyzed from the perspective of longitudinal plastic strain and longitudinal contraction force.

The out-of-plane deformation of the corresponding model is in good agreement with the measured results, and milder than the out-of-plane deformation of the model in a free state. When external restraints are applied, the longitudinal plastic strain of the weld and its adjacent metal decreases, and the longitudinal contraction force of the thin plate also decreases.

This study seeks to expand the bandgap frequency band, reduce the bandgap starting frequency and analyze and optimize the bandgap parameters of acoustic metamaterials.

The influence of geometrical and material parameters on the bandgap properties of acoustic metamaterials is analyzed, and a method for maximizing the bandgap width is proposed. The multi-objective optimization problem is converted into a single objective optimization problem by normalizing the bandgap frequency coefficients. Structural material conversion is achieved via the material selection optimization method, and the optimization equations of bandgap parameters are established on the basis of weight-lightening. For chiral acoustic metamaterials, the material properties (density and wave velocity) and geometric parameters (scatterer diameter, ligament thickness and coating thickness) are defined as design variables, and the comprehensive optimization of structural parameters and material selection of acoustic metamaterials based on weight-lightening are implemented.

The optimization results show that the bandgap width increases by 27.7% and the lower bound frequency decreases by 1048 Hz, thereby achieving the goal of expanding the bandgap width based on lightweight acoustic metamaterials. The acoustic transmission analysis of the finite chiral acoustic metamaterial structure is then carried out to verify the effectiveness of the proposed method.

As a new type of pressure-resistant structure, the titanium alloy sandwich cylindrical shell has not yet been studied comprehensively. The topology of the core layer needs to be confirmed using the optimization method. This paper carries out the core topology optimization of titanium alloy pressure- resistant sandwich cylindrical shells.

An unreinforced cylindrical shell with high thickness is selected as the analysis object, and the axisymmetric element is used to calculate the structural stresses via ANSYS. The cylindrical shell is divided into the upper, middle and lower regions along the thickness direction. The structures of the middle region are set as the design variables, and a two-stage topology optimization mathematical model of its core structure is proposed. Based on Matlab, the main control program of the genetic algorithm is established to carry out the core layout optimization of the unreinforced cylindrical shell along the axial direction only and both the axial direction and radial direction respectively.

The optimal core topological form consists of equidistant ribs connecting the inner shell and outer shell vertically.