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| 1 | A Footpad Structure with Reusable Energy Absorption Capability for Deep Space Exploration Lander:Design and Analysis显示文摘The footpad structure of a deep space exploration lander is a critical system that makes the initial contact with the ground,and thereby plays a crucial role in determining the stability and energy absorption characteristics during the impact process.The conventional footpad is typically designed with an aluminum honeycomb structure that dissipates energy through plastic deformation.Nevertheless,its effectiveness in providing cushioning and energy absorption becomes significantly compromised when the structure is crushed,rendering it unusable for reusable landers in the future.This study presents a methodology for designing and evaluating structural energy absorption systems incorporating recoverable strain constraints of shape memory alloys(SMA).The topological configuration of the energy absorbing structure is derived using an equivalent static load method(ESL),and three lightweight footpad designs featuring honeycomb-like Ni-Ti shape memory alloys structures and having variable stiffness skins are proposed.To verify the accuracy of the numerical modelling,a honeycomb-like structure subjected to compression load is modeled and then compared with experimental results.Moreover,the influence of the configurations and thickness distribution of the proposed structures on their energy absorption performance is comprehensively evaluated using finite element simulations.The results demonstrate that the proposed design approach effectively regulates the strain threshold to maintain the SMA within the constraint of maximum recoverable strain,resulting in a structural energy absorption capacity of 362 J/kg with a crushing force efficiency greater than 63%. | Weiyuan Dou Xiaohang Qiu Zhiwei Xiong Yanzhao Guo Lele Zhang | 2023 | Chinese Journal of Mechanical Engineering2023，36，4： | 0 |
| 2 | Static strength and crashworthiness analysis of a train cowcatcher at a running speed of 160 km/h显示文摘The cowcatcher is one of the unique devices at the front end of the train, which can remove obstacles on the track by crashing before the vehicle body to ensure the safety of the train. When a collision accident happens, the cowcatcher serves as the first energy-absorbing structure to dissipate and guide the collision energy. The design of the existing cowcatcher of multiple units generally focuses on the good ability to remove obstacles, while the secondary function, the crashworthiness of orderly deformation under collision, still needs further research. In this study, a finite element model of structural static load and collision analysis was established under standard EN 15227, with the cowcatcher for 160 km/h train as the prototype. Then the solution and simulation process was accomplished under the environment of ANSYS and LS-DYNA. The analysis results showed that the structural static strength of the current cowcatcher met the requirements of the standard EN 15227, and the longitudinal stiffness was evenly distributed. When removing the obstacles with low mass, the impact force was small and the structure would not produce obvious deformation;when removing the obstacles with large mass, the impact force was large and the shear fracture might occur at the connection of the cowcatcher. | Yanzhao Guo Lele Zhang Weiyuan Dou Yu Zhu Haifeng Zhang | 2023 | High-Speed Railway2023，1，4： | 0 |
| 3 | A Compensation Algorithm for Large Element Characterizing the Damage Evolution Process and Its Application to Structure Collisions显示文摘When simulating the process from elastic–plastic deformation,damage to failure in a metal structure collision,it is necessary to use the large shell element due to the calculation efficiency,but this would affect the accuracy of damage evolution simulation.The compensation algorithm adjusting failure strain according to element size is usually used in the damage model to deal with the problem.In this paper,a new nonlinear compensation algorithm between failure strain and element size was proposed,which was incorporated in the damage model GISSMO(Generalized incremental stress state dependent damage model)to characterize ductile fracture.And associated material parameters were calibrated based on tensile experiments of aluminum alloy specimens with notches.Simulation and experimental results show that the new compensation algorithm significantly reduces the dependence of element size compared with the constant failure strain model and the damage model with the linear compensation algorithm.During the axial splitting process of a circular tubular structure,the new compensation algorithm keeps the failure prediction errors low over the stress states ranging from shear to biaxial tension,and achieves the objective prediction of the damage evolution process.This study demonstrates how the compensation algorithm resolves the contradiction between large element size and fracture prediction accuracy,and this facilitates the use of the damage model in ductile fracture prediction for engineering structures. | Wen Liu Lele Zhang Yifan Ru Geng Chen Weiyuan Dou | 2023 | Chinese Journal of Mechanical Engineering2023，36，1： | 0 |
| 4 | High-performance ZnO humidity sensor synthesized by coprecipitation with PVP as surfactant for human respiration detection显示文摘A high-performance zinc oxide(ZnO)/polyvinylpyrrolidone(PVP)humidity sensor was prepared by simple coprecipitation method with PVP as surfactant.The coprecipitation method has low reaction temperature,little energy consumption and simple preparation,which is suitable for large-scale production.The PVP makes sample’s surface with more hydroxyl and oxygen vacancies than pure ZnO,which can absorb more water molecules and promote the decomposition of water molecules into H3O+to form effective ion conduction.When the molar ratio of PVP to ZnO is 1:1,the ZnO/PVP humidity sensor has low hysteresis(~4.2%),short response/recovery time(9/10 s),excellent stability and high sensitivity with more than 4 orders of magnitude in relative humidity(RH)range from 11%to 95%.Moreover,the ZnO/PVP humidity sensor can distinguish different respiratory states of human body,which has a potential in monitoring and prevention of respiratory diseases. | MAN Jianping GU Weiyuan HU Ziyan DOU Xiaozong ZHANG Hongyan | 2023 | Optoelectronics Letters2023，19，1： | 0 |
| 5 | Fatigue Characterization on a Cast Aluminum Beam of a High-Speed Train Through Numerical Simulation and Experiments显示文摘The cast aluminum beam is a key structure for carrying the body-hung traction motor of a high-speed train;its fatigue property is fundamental for predicting the residual life and service mileage of the structure.To characterize the structural fatigue property,a finite element-based method is developed to compute the stress concentration factor,which is used to obtain the structural fatigue strength reduction factors.A full-scale fatigue test on the cast aluminum beam is designed and implemented for up to ten million cycles,and the corresponding finite element model of the beam is validated using the measured data of the gauges.The results show that the maximum stress concentration occurs at the fillet of the supporting seat,where the structural fatigue strength reduction factor is 2.45 and the calculated fatigue limit is 35.4 MPa.Moreover,no surface cracks are detected using the liquid penetrant test.Both the experimental and simulation results indicate that the cast aluminum beam can satisfy the service life requirements under the designed loading conditions. | Weiyuan Dou Lele Zhang Haifeng Chang Haifeng Zhang Changqing Liu | 2021 | Chinese Journal of Mechanical Engineering2021，34，5： | 0 |
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