Parametric design strategy of a novel cylindrical negative Poisson’s ratio jounce bumper for ideal uniaxial compression load-displacement curve

A cylindrical negative Poisson’s ratio (CNPR) structure based on two-dimensional double-arrow negative Poisson’s ratio (NPR) structure was introduced in this paper. The CNPR structure has excellent stiffness, damping and energy absorption performances, and can be applied as spring, damper and energy absorbing components. In this study, the CNPR structure was used as a jounce bumper in vehicle suspension, and the load-displacement curve of NPR jounce bumper was discussed. Moreover, the influences of structural parameters and materials on the load-displacement curve of NPR jounce bumper were specifically researched. It came to the conclusion that only the numbers of cells and layers impact the hardening displacement of NPR jounce bumper. And all parameters significantly affect the structure stiffness at different displacement periods. On the other hand, the load-displacement curve of NPR jounce bumper should be in an ideal region which is difficult to be achieved applying mathematical optimization method. Therefore, a parametric design strategy of NPR jounce bumper was proposed according to the parametric analysis results. The design strategy had two main steps: design of hardening displacement and design of stiffness. The analysis results proved that the proposed method is reliable and is also meaningful for relevant structure design problem.     

4D printing of personalized shape memory polymer vascular stents with negative Poisson’s ratio structure: A preliminary study

Four-dimensional(4D) printing, integrates transformation information into three-dimensional(3D)-printed structures, which means that 3D-printed structures are able to change their shapes, properties, or functionalities over time. Here, two types of shape memory personalized vascular stents with negative Poisson's ratio structure are developed via 4D printing. The genetic algorithm is used to optimize the structure. Axial compression tests, radial compression tests and three-point bending tests are carried out to study the mechanical properties of the stents. In addition, fluid-structure interaction and stress distribution during the shape recovery process are investigated based on finite element method. The shape memory behaviors of the stents are excellent and in vitro feasibility tests demonstrate that the stents can expand the simulated narrow blood vessel rapidly. Therefore, 4D printed shape memory stents with negative Poisson's ratio structure are highly promising for the treatment of vascular stenosis.     

Performance analysis and design of self-air-cooling reciprocating compressor’s cooling system

Science China Technological Sciences - The cooling system, as an important part of high-pressure compressor, has always been a key technical bottleneck for its miniaturization. A new type...     

World’s first spaceflight on-orbit demonstration of a flexible solar array system based on shape memory polymer composites

With a 10% reversible compressive strain in more than 10 deformation cycles, the shape memory polymer composites(SMPCs)could be used for deployable structure and releasing mechanism. In this paper, without traditional electro-explosive devices or motors/controllers, the deployable SMPC flexible solar array system(SMPC-FSAS) is studied, developed, ground-based tested,and finally on-orbit validated. The epoxy-based SMPC is used for the rolling-out variable-stiffness beams as a structural frame as well as an actuator for the flexible blanket solar array. The releasing mechanism is primarily made of the cyanate-based SMPC,which has a high locking stiffness to withstand 50 g gravitational acceleration and a large unlocking displacement of 10 mm. The systematical mechanical and thermal qualification tests of the SMPC-FSAS flight hardware were performed, including sinusoidal sweeping vibration, shocking, acceleration, thermal equilibrium, thermal vacuum cycling, and thermal cycling test. The locking function of the SMPC releasing mechanisms was in normal when launching aboard the SJ20 Geostationary Satellite on 27 Dec., 2019. The SMPC-FSAS flight hardware successfully unlocked and deployed on 5 Jan., 2020 on geostationary orbit. The triggering signal of limit switches returned to ground at the 139 s upon heating, which indicated the successful unlocking function of SMPC releasing mechanisms. A pair of epoxy-based SMPC rolled variable-stiffness tubes, which clapped the flexible blanket solar array, slowly deployed and finally approached an approximate 100% shape recovery ratio within 60 s upon heating. The study and on-orbit successful validation of the SMPC-FSAS flight hardware could accelerate the related study and associated productions to be used for the next-generation releasing mechanisms as well as space deployable structures, such as new releasing mechanisms with low-shocking, testability and reusability, and ultra-large space deployable solar arrays.     

Fault detection of excavator’s hydraulic system based on dynamic principal component analysis

In order to improve reliability of the excavator＇s hydraulic system, a fault detection approach based on dynamic principal component analysis（PCA） was proposed. Dynamic PCA is an extension of PCA, which can effectively extract the dynamic relations among process variables. With this approach, normal samples were used as training data to develop a dynamic PCA model in the first step. Secondly, the dynamic PCA model decomposed the testing data into projections to the principal component subspace（PCS） and residual subspace（RS）. Thirdly, T2 statistic and Q statistic performed as indexes of fault detection in PCS and RS, respectively. Several simulated faults were introduced to validate the approach. The results show that the dynamic PCA model developed is able to detect overall faults by using T2 statistic and Q statistic. By simulation analysis, the proposed approach achieves an accuracy of 95% for 20 test sample sets, which shows that the fault detection approach can be effectively applied to the excavator＇s hydraulic system.     

GIS-based 3D limit equilibrium analysis for design optimization of a 600 m high slope in an open pit mine

1. Introduction An economical and safe plan of slope angle is an important issue for the slope designing of an open pit mine. In the practice of geotechnical engineering, a two-dimensional (2D) limit equilibrium method is gen- erally employed to calculate the safety factor against failure for a slope. Assuming a plane-strain condition, the safety factor is commonly assessed through a 2D idealization of the slope, for example, an “equivalent” plane-strain problem is postulated and analyzed […     

Prediction of a V-8 diesel engine’s structural radiated noise and research of important parameters’ effects on the engine’s acoustic behaviors

Based on the coupled boundary element method-finite element method(BEM-FEM)method and the acoustic transfer vector(ATV)technology,BEM/FEM model is proposed for a V-type eight cylinders engine acoustic radiation simulating analysis under semi-anechoic condition.Acoustic radiation power,field points sound pressure level and panel contributions are calculated by acoustic radiation response analysis.Additionally,based on the engine acoustic performance,different acoustic behaviors of engine are studied by changing engine materials,oil pan structures as well as geometry parameters.The acoustic performance of this engine is predicted and the influence of material,structural and geometry parameters on engine radiated noise are generalized.The principle will guide the design and optimization of the engine prototype in further work.     

Modeling and simulation of induction motor drive system to investigate and mitigate of PWM inverter’s adverse effects

Applied high-frequency(HF)switching devicescan cause electromagnetic interferences(EMI)in pow-er electronic converter.It is necessary for an electro-magnetic compatibility(EMC)design to prospect andconsider its possible EMI levels.AC motor drive systems i…     

The foundation and analysis of polarized magnetic system’s unified mathematical model in aerospace electromagnetic relay

Polarized magnetic system has a series of features, such as small volume, light weight, low power consumption, high sensitivity, quick movement and so on, widely used in the products of the military aerospace electromagnetic relay. The typical polarized magnetic system has mainly four structures and its simplified equivalent magnetic circuits model is the base of the design of the electromagnetic relay with permanent magnet. In the past, the analysis method that people used was difficult to build the unified mathematical models, which divided the work gap magnetic flux into "permanent magnet flux" and "electromagnetic flux". Based on the analysis method of the work gap magnetic voltage, this paper founds the unified mathematical model of the polarized magnetic system and divides the attractive torque into permanent magnet torque, polarized torque and electromagnetic torque through the energy balance formula. It analyses the influence of permanent magnet sizes on permanent magnet torque, polarized torque and electromagnetic torque through the energy balance formula and the conclusions can direct the design of aerospace electromagnetic relay with permanent magnet.     

Schedule optimization to improve trunk-local bus transfer efficiency in small conurbations: A case study of New York’s capital region

Fostering the use of transit has been broadly accepted as an effective way to improve social equity and reduce the externalities caused by transportation. In the great body of transit literature, many have focused on the improvement of transfer efficiency. However, investigation on transit transfer efficiency is still lacking for medium sized cities or suburban areas that have sprawled from city centers. The special features associated with such an urban form lead to unique travel patterns and bus operations. This work develops a process to improve bus transfer efficiency for small conurbations considering their special characteristics. A case study of New York's Capital District is used to illustrate the proposed method. Results show that the transfer waiting time can be remarkably shortened. The proposed method can be widely adapted to other transit systems in small conurbations.     

Time to change the energy conservation direction of China’s steel industry: From upgrading the technology level to increasing scrap ratio

A new energy intensity(EI) index for steel production—energy intensity at specific scrap ratio(EISR) index—is developed in this study to provide a method for analyzing the EI difference of steel production through a case-study analysis for China and Japan. The real cause of EI change of China's key steel enterprises from 2006–2014 is also studied by using the EISR index.Result shows significant technology progress decreases the EI of China's key steel enterprises by 16% from 2006 to 2014, but the final drop of comparable EI was only 12.3% due to the continued decreased scrap ratio(SR). From 2006 to 2014, the main cause of EI gap between China's key steel enterprises and Japan's steel industry changed from gap in technological level to difference in SR. In factor analysis that assumed Japanese share of electric arc furnace production(23.2%) and SR(33.3%) in 2014 in China, the EI of China's key steel enterprises decreased to 612 kgce/t(kilogram standard coal/t)(primary energy consumption),which is almost same as Japan's data. The key task of energy conservation in China's key steel enterprises in the future should be changed from upgrading the technology level to increase the SR of steel production.     

Simulation and analysis of a Truck Model’s ride comfort based on fuzzy adaptive control theory

With the development of national highroad and theincreasing of transportation of passenger and cargo,au-tomobile’s handing stability,ride comfort and securityare demanded highly,and vehicle with air suspensionis used widely.By EC technical development,au…     

Methodology for estimating probability of dynamical system’s failure for concrete gravity dam简

Methodology for the reliability analysis of hydraulic gravity dam is the key technology in current hydropower construction.Reliability analysis for the dynamical dam safety should be divided into two phases：failure mode identification and the calculation of the failure probability.Both of them are studied based on the mathematical statistics and structure reliability theory considering two kinds of uncertainty characters（earthquake variability and material randomness）.Firstly,failure mode identification method is established based on the dynamical limit state system and verified through example of Koyna Dam so that the statistical law of progressive failure process in dam body are revealed; Secondly,for the calculation of the failure probability,mathematical model and formula are established according to the characteristics of gravity dam,which include three levels,that is element failure,path failure and system failure.A case study is presented to show the practical application of theoretical method and results of these methods.