Currently, civil unmanned aerial vehicles (UAVs) are developing toward being heavier and more maneuverable, leading to a geometric growth in the energy required for ejection, which poses huge challenges to traditional ejection methods. The sixfold pulley range-extending ejector system can convert the cylinder stroke into sixfold rope displacement, greatly improving the launch efficiency and effectively addressing this issue. This study proposes a pulley range-extending internal ballistics calculation method based on rigid equivalent load, verifies it through experiments, and discusses the influence of the reaction of the load system. The main innovations are as follows: (i) realizing effective ejection of large-mass loads through a sixfold pulley block; (ii) establishing a rigid equivalent load model that considers factors, such as friction and pulley rotation, providing input for rigid internal ballistics; and (iii) compared with the traditional finite element simulation method, this method significantly improves computational efficiency and is suitable for rapid iterative optimization in engineering design. This system can be applied to the takeoff and landing of logistics UAVs in mountainous areas without runway conditions, as well as the airdrop system of heavy equipment in emergency rescue scenarios. The ejector scheme with a sixfold range-extending pulley block proposed in this paper provides a reference for the current high-speed and heavy-load ejection.

The anti-penetration performance of a double-arrow honeycomb sandwich structure with negative Poisson’s ratio (NPR) is investigated by using finite element simulation. With the penetration of small-caliber projectiles to nine types of arrowhead NPR honeycomb sandwich structures, the ballistic characteristics are obtained. The change in attitude during projectile penetration is obtained through simulation, and the dynamics simulation model of the projectile penetration double-arrow cell element is established. The simulation results show that when the thickness of the upper and lower layers are kept constant and only the double-arrow angle of the core layer is increased, the ballistic limit of the honeycomb sandwich structure is subsequently reduced. For the same honeycomb sandwich structure, there is a nonlinear relationship between the initial velocity of the bullet and the structural kinetic energy absorption rate. In addition, there is a specific velocity range within which the honeycomb sandwich structure exhibits optimal anti-penetration performance. During the penetration process, the projectile experiences an uneven distribution in the circumferential divection, which generates an asymmetric effect, altering the force environment, and leads to an unstable trajectory in the projectile’s penetration.

In the pursuit of global energy conservation and emissions reductions, utilizing beverage cans as energy-absorbing components offers potential for a sustainable economy. This study examines the impact of foam filling on the crushing behaviors and energy absorption of various types of beverage cans. Quasi-static compression tests were conducted on five geometrically sized cans filled with three densities of polyurethane foam to study their deformation modes and calculate crashworthiness parameters within the effective stroke. Results show that empty beverage cans have lower energy absorption capacities, and deformation modes become less consistent as can size increases. Higher foam density leads to increased total energy absorption, a slight reduction in the effective compression stroke, and a tendency for specific energy absorption to initially increase and then decrease. Regarding crush behavior, smaller cans transition from a diamond mode to a concertina mode, while larger cans exhibit a columnar bending mode. Next, the coupling effect of energy absorption between foam and cans was analyzed so as to reveal the design method of energy-absorbing components. The specific energy absorption of smaller cans filled with polyurethane foam is superior to that of similar empty cans. These findings provide valuable insights for selecting next-generation sustainable energy absorption structures.

Abstract Honeycombs have been used in a wide range of repeatable energy-absorbing elements due to their light weight and high energy absorption capacity. In the engineering environment, honeycombs will produce a shape change effect and rebound under multiple loading and unloading, so it is of great importance to investigate the energy-absorbing properties of honeycombs under the shape change effect for the application of honeycombs. In this study, the deformation process and energy absorption properties of 3D printed honeycombs under multiple loading were obtained through multiple quasi-static compression tests. On this basis, the coupling between shape change effects and honeycomb energy absorption is revealed. It is shown that the number of compressions does not affect the four-stage force-displacement curve characteristics of the honeycombs, but only the energy absorption efficiency of the honeycombs. There is an inverse relationship between the resilience of honeycombs and the energy absorption capacity of honeycombs, and the change of honeycomb stiffness under repeated compression is the direct cause of this relationship. The research results provide a reference for the application of honeycombs in the field of repetitive energy absorption.

To improve the internal ballistic performance of compressed-air ejection devices and achieve continuous launching, it is essential to investigate the dynamic characteristics and transient flow field during the opening and closing of the high-pressure pneumatic pilot-driven on/off valve (HPPV) within the device. A transient fluidsimulation model of the HPPV is established in Fluent using a sliding mesh and 6 Degree of Freedom (DOF) dynamic mesh technology, and experiments are conducted to evaluate the solution accuracy of the model. Meanwhile, the influence of real-gas thermal and wall heat-transfer effects on the simulation model are investigated, and the transient flow field of the HPPV is analyzed during its opening and closing under a high-pressure initial gas source. The maximum tolerance between the results of the HPPV transient fluid-simulation model based on the CFD method and experimental data is 5.87 % under different initial pressures. Both the wall heat transfer and real gas thermal effects impact the accuracy of the transient fluid model for HPPV. Considering these factors leads to a 2 - 3% enhancement in the solving accuracy of the model. The Joule - Thomson effect inside the pilot-valve and control gas chambers is evident. The pilot-valve chamber is susceptible to leakage and sealing failure owing to significant pressure and temperature differences between the two sides of the gas. The temperatures of the chamber for the opening and closing valves are low during the exhaust process, which enables ice to be formed easily inside the chamber.

A high-pressure pneumatic pilot-driven on/off valve (HPPV) that quickly switches an air inlet line on and off was designed to meet the requirements of a compressed air ejection device with high pressure, high flow rate, and continuous ejection. An HPPV multi-physics field simulation model was established using AMESim simulation software based on the bond graph modeling approach that considered mechanical, gas flow, pipe heat exchange, and pilot valve operation, and experiments were conducted to check the simulation model accuracy. The effects of real gas thermodynamics, pipeline heat exchange, and pilot valve operation on the simulation model accuracy and those of different initial parameter conditions on the dynamic characteristics of the HPPV were investigated in the validated simulation model. The results indicated that the tolerance between simulation and experiment was less than 7.3%, so the simulation model was realistic and reliable. In addition, among the different influencing factors, the pipeline heat transfer significantly affected the simulation model accuracy, and the tolerance between the simulation results without considering the pipeline heat exchange and the experimental results exceeded 10%. The real gas thermal effect slightly affected the simulation model accuracy, and the tolerance between the simulation results under the action of each gas state equation was less than 3%. The pilot valve operation affected only the opening and closing moments of the HPPV and had no effect on the simulation model accuracy. The dynamic characteristics of the HPPV were stable and reliable under different initial parameter conditions.

无杆式高压气动弹射器因开口的固有结构决定其存在一定量的泄漏,为此设计并开展样机泄漏测试试验.基于由实验数据拟合的标准干空气热力学状态方程,分别按理想气体和真实气体对比计算泄漏率,并拟合泄漏率随压力、行程变化的经验公式.建立考虑动态泄漏、真实气体效应及真实开阀规律的精确内弹道模型,对考虑和不考虑泄漏两种工况的结果进行对比,并详细分析考虑泄漏的弹射过程中热力学参数与负载运动参数的变化规律,将其与弹射试验数据、流体仿真结果进行对比.研究结果表明:按理想气体计算的泄漏率比真实气体偏小约 4%;泄漏率不超过4%/s;考虑泄漏的精确内弹道模型计算结果与弹射试验数据、流体仿真结果均基本一致,具有较高的计算精度.

The combination of auxetic honeycomb and CNT reinforcement composite is expected to further improve the impact protection performance of sandwich structures. This paper studies the low-velocity impact response of sandwich plates with functionally graded carbon nanotubes reinforced composite (FG-CNTRC) face sheets and negative Poisson’s ratio (NPR) auxetic honeycomb core. The material properties of FG-CNTRC were obtained by the rule of mixture theory. The auxetic honeycomb core is made of Ti-6Al-4V. The governing equations are derived based on the first-order shear deformation theory and Hamilton’s principle. The nonlinear Hertz contact law is used to calculate the impact parameters. The Ritz method with Newmark’s time integration schemes is used to solve the response of the sandwich plates. The (20/−20/20)s, (45/−45/45)s and (70/−70/70)s stacking sequences of FG-CNTRC are considered. The effects of the gradient forms of FG-CNTRC surfaces, volume fractions of CNTs, impact velocities, temperatures, ratio of plate length, width and thickness of surface layers on the value of the plate center displacement, the recovery time of deformation, contact force and contact time of low-velocity impact were analyzed in detail.

This paper reports a low-velocity impact response of the functionally graded carbon nanotubes reinforced composite (FG-CNTRC) laminated plates with negative Poisson’s ratios (NPR) and clamped boundary conditions. The NPR and functionally graded properties are evaluated for the layers in the thickness direction. Reddy’s higher-order shear deformation theory is used to establish the governing equations. The rule of mixture model is used to determine the material properties of FG-CNTRC. The Hertz contact law is used to calculate the contact force. The Newmark’s time integration scheme and Newton–Raphson algorithm are used to obtain the low-velocity impact response. The effects of the gradient forms of FG-CNTRC, temperatures, initial impact velocities, plate thickness, and effective Poisson’s ratios on the low-velocity impact response of laminated plates are carried out and discussed.

无杆式高压气动弹射器因开口的固有结构决定其存在一定量的泄漏，为此设计并开展了样机泄漏测试试验。基于由实验数据拟合的标准干空气热力学状态方程，分别按理想气体和真实气体对比计算泄漏率，并拟合泄漏率随压力、行程变化的经验公式。建立考虑动态泄漏、真实气体效应及真实开阀规律的精确内弹道模型，对考虑和不考虑泄露两种工况的结果进行对比，并详细分析考虑泄露的弹射过程中热力学参数与负载运动参数的变化规律，将其与弹射试验数据、流体仿真结果进行对比。研究结果表明:按理想气体计算的泄漏率比真实气体的偏小约4%；泄漏率不超过4%/s；考虑泄漏的精确内弹道模型计算结果与弹射试验数据、流体仿真结果均基本一致，具有较高的计算精度。

To study the long-term creep behavior prediction of polymethacrylimide (PMI) foams, the gradation loading creep tests were proposed at four different temperatures in this paper. The Stepped Isostress (SSM) and TTSP methods were combined to obtain the master curve under reference stress and temperature. The artificial Neural Networks (ANN) technique was used to build the long-term creep behavior prediction model of PMI materials. The effects of different activation functions, hidden layer structures, and other super parameters on the prediction performance were investigated. The results suggest that the SSM plus TTSP method can be used to construct the master curve, which could predict a larger time scale of material creep behavior based on a short-term test. It is of great significance and feasible to predicts the long-term creep life of materials accurately using advanced artificial intelligence technology. According to the statistical analysis, the logistic type activation function has a more accurate and stable prediction performance on long-term creep behavior prediction of PMI. To avoid overfitting, the number of hidden layers should be as small as possible, and the prediction performance of a single hidden layer structure with 8 neurons is sufficient for long-term creep behavior prediction in the engineering area. The statistical value of the correlation coefficient was greater than 0.995. The application range of advanced artificial intelligence technology in this field can be further expanded in the preceding research, such as in the prediction of long-term creep behavior on the composition level of the material.

The long-term mechanical properties of viscoelastic polymers are among their most important aspects. In the present research, a machine learning approach was proposed for creep properties’ prediction of polyurethane elastomer considering the effect of creep time, creep temperature, creep stress and the hardness of the material. The approaches are based on multilayer perceptron network, random forest and support vector machine regression, respectively. While the genetic algorithm and k-fold cross-validation were used to tune the hyper-parameters. The results showed that the three models all proposed excellent fitting ability for the training set. Moreover, the three models had different prediction capabilities for the testing set by focusing on various changing factors. The correlation coefficient values between the predicted and experimental strains were larger than 0.913 (mostly larger than 0.998) on the testing set when choosing the reasonable model.

The permanent-magnet synchronous motor system will display a variety of chaotic phenomenon when its parameters or external inputs satisfy certain condition, and thus its performance would be deteriorated. Therefore, chaos should be suppressed or eliminated. In this article, a practical method which combines adaptive robust control with a single-layer neural network–based disturbance observer is proposed for elimination of the chaos and high-performance motion control of permanent-magnet synchronous motor. The proposed controller not only accounts for the load torque disturbance but also takes the parametric uncertainties into account. A single-layer neural network–based disturbance observer is designed to estimate the disturbance while an adaptive control law is designed to estimate the parameters respectively. Then, all the estimated values are used in the feedforward cancelation item in the controller via a backstepping technique. Lyapunov’s method is used to prove the stability of the novel control scheme. Sufficient comparative simulation results are obtained to validate the effectiveness of the proposed control strategy.

The low-velocity impact response of the sandwich curved panels with functionally graded carbon-nanotube-reinforced composite (FG-CNTRC) surface and isotropic foam core is discussed in this paper.Five types of stacking arrangements including uniform distribution of FG-CNTRC considering thermal environment were analysed. Using the Hertz contact law and rule of mixture model as well as the Kármán-type equations, the nonlinear formulations were built and solved by the two-step perturbation method. The carbon nanotubes’ volume fraction, the structure size, the original impact velocity, temperature, relative thickness and the influence of gradient forms on the panels’ impact behaviours were analysed. The outcomes show that the stiffness of the non-contact surface has large influence on contact response and various types of FG-CNTRC can be used for different operating conditions providing stiffness or cushion performance.

The low velocity impact analysis of functionally graded carbon nanotubes reinforced composite (FG-CNTRC) spherical shells including the contact force and indentation of the shell surface center was presented. The material properties were set according to the rule of mixture. The fibers and polymeric matrix were temperature-dependent. Timoshenko-Midlin assumption was used to establish the dimensionless nonlinear governing equations of the axis-symmetric transverse isotropy spherical shells. The Hertz contact theory was established to obtain the force and displacement between the spherical shell and impactor. Seven species of comparison analyses including grading profiles and volume fraction were mentioned to investigate the influence on the low velocity impact response of the FG-CNTRC spherical shells. The results revealed that the contact force was determined by the material properties of both contact surface and noncontact surface collectively. Furthermore, the increase of volume fraction can result in the larger contact force and shorter contact time.

This paper studies the high-performance tracking control of electro-hydraulic systems with consideration of both mismatched and matched modeling uncertainties. A continuous integral robust control strategy is proposed based on the backstepping design framework. By introducing a novel error transformation, the mismatched modeling uncertainty can be transmitted to the control input channel, and then, the constructed integral robust structure in the proposed controller can handle it together with the matched modeling uncertainty. The acceleration signal that usually suffers heavy noise contamination is not required in the controller, and the final control input is continuously differentiable, which is benefit for tracking performance improvement and practical controller implementation. The closed-loop system stability is analyzed via the Lyapunov theory, and it reveals that the proposed controller achieves an asymptotic tracking performance with zero steady-state error in the presence of various modeling uncertainties. Comparative experiments are performed to demonstrate the effectiveness of the proposed control strategy.

The concept of critical speed'was proposed for the lubrication status varying with sliding speed.The two-dimensioned efficient analysis models were established to analyze the lubrication performance of high-speed rod-less cylinder seal ring.The primary mapping of'critical speed'was determined in whole speed range and the influence factors such as compression ratios,seal angle and the temperature were revealed.The oil temperature boundary was obtained by calculating friction heat and the coefficient of heat partition.The oil's three-dimensional micro-model based on Gauss distribution function and exponential autocorrelation function was onstructed to describe the geometry morphology of real rough surface.The three-dimensional precision analysis model was established and the precision location of'critical speed'was got.The influence of seal surface texture an lubrication performance was investigated.Results show that the'critical speed'increases with the compression ratios,seal angle and the temperature increasing The influence for'critical speed'is obvious.The isotropic micro-surface texture is more easily to form hydrodynamic lubrication.

A kind of one-side ejection device with two-step cylinder is proposed to increase the effective thrust travel of missile pneumatic launching system.The real gas state equation,Peng-Robinson equation,is used as theoretical basis.The mathematical expressions of pneumatic interior ballistics model are deduced on the basis of P-R’state equation for the two-step cylinder.The interior ballistics equation is solved by using Simulink software,and the one-side launching ejection is built by means of ADAMS.The co-simulation model of device is achieved.The results show that the pressure of first-order lower-chamber rises first and then falls.It can be seen from the calculated result that both the thermodynamic parameters and the missile acceleration obviously fluctuate in the process of cylinder changing,but their influences on missile speed and displacement are very small.To reduce the equipment volume,the air source volume is selected as the objective function.The air source volume optimized by genetic algorithm is decreased by 64.5％,thus improving greatly the mobility of launcher.

To study the impact response of the functionally graded carbon nanotubes reinforced composite (FG-CNTRC) laminates, four types of stacking arrangements were discussed in this paper. The general Kármán type equations, rule of mixture and Hertz contact law were used to formulate the laminate, material and contact behavior, respectively. The effects of different gradient forms, temperature, initial velocity and volume fraction of carbon nanotubes (CNTs) on the impact behavior of the laminates were investigated. The results suggest that the titanium alloy layer has improved the stiffness and strength of the laminates and weakened the influence of the FG-CNTRC. A higher temperature results in a larger center displacement due to the existence of the temperature-dependent materials. In addition, a faster velocity leads to a larger deformation rate of the laminate in the initial stage and also a larger center displacement.