We proposed a new type of phase transforming auxetic material (PTAM) by embedding magnets into cellular auxetic material with rotating cubes. To find out the effect of magnets on the mechanics of PTAM, several samples were fabricated and attractive magnets were embedded. Quasi-static uniaxial compression tests were performed and the results show that the phase of the material can be successfully changed by embedding attractive magnets,which means this material exhibits from one phase to two phases.
This paper presents a locking device which achieves in locking the rotary feed structure of a space-borne microwave
radiometer during the launch stage. This locking device employs two shape memory alloy (SMA) wires as the actuating
elements, and uses a self-locking structure to achieve the locking function. To improve the performance and reliability, a
redundant SMA wire and a step structure are employed. To validate the proposed SMA locking device, four prototypes
were fabricated and tested. The result shows that the locking device possesses the advantages of remarkable locking
performances, wide operation electric current and high survival temperature. Based on the test results, the locking device
has a great potential for the application of space rotary structures.
A method to improve low velocity impact resistance of aeroengine composite casing using shape memory alloy’s properties of shape memory(SM) and super-elasticity(SE) is proposed in this study. Firstly, a numerical modeling of SMA reinforced composite laminate under low velocity impact load with impact velocity of 10 m/s is established based on its constitutive model implemented by the VUMAT subroutine of commercial software ABAQUS. Secondly, the responses of SMA composite laminate including stress and deflection distributions were achieved through transient analysis under low velocity impact load. Numerical results show that both peak stress and deflection values of SMA composite laminate are less than that without SMA, which proves that embedding SMA into the composite structure can effectively improve the low velocity impact performance of composite structure. Finally, the influence of SM and SE on low velocity impact resistance is quantitatively investigated. The values of peak stress and deflection of SMA composite based on SM property decrease by 18.28% and 9.43% respectively, compared with those without SMA, instead of 12.87% and 5.19% based on SE. In conclusion, this proposed model described the impact damage of SMA composite structure and turned to be a more beneficial method to enhance the impact resistance by utilizing SM effect.
Spacecrafts require a variety of separation and release devices to accommodate separation from the launch vehicle or
deployment of heat radiation panels, solar arrays and other appendages. In order to overcome drawbacks of the current
release devices, this paper proposes a design scheme of release device with a form of segmented nut and actuated with
SMA (Shape Memory Alloy) wire. In order to validate the release device's function and performance, ground tests
including single device response time tests, synchronous tests of two devices, fatigue life tests were carried out. Tests
results show that the innovative space release device developed in this paper owning the advantages of small size, quick
response, long fatigue life, high simultaneity and auto-reset has a potential use in space engineering.
Rangeland in Inner Mongolia is an arid ecosystem with vulnerability. Anthropogenic activities especially over-grazing
have been believed to be a leading factor shifting the vulnerability into actual degradation in the ecosystem. Net primary
productivity (NPP) is an important indicator for vulnerability monitoring in arid ecosystem. In this study we use the
vegetation photosynthesis model to estimate NPP of rangeland ecosystem in Inner Mongolia. The objective is to examine
the spatial variation of NPP in Inner Mongolia and to highlight vulnerable areas for sustainable development. Several
improvements have been done to the model especially in its parameterization. Land surface temperature required by the
model was estimated from split window algorithm proposed for MODIS thermal band data. Using the MODIS image
data and the ground climate datasets, we applied the improved model to estimate the NPP in 2003 in Inner Mongolia.
Our results showed that mean NPP was 192.03gC m-2 Gr-1 in Inner Mongolia in 2003. Spatial variation of the NPP was
very obvious. Very low NPP was observed in the western parts while relatively high NPP could be seen in the eastern
and northeastern parts. For various type rangelands, temperate alpine meadow is the highest. Although the mean NPP of
temperate steppe is not high, its area is the largest in Inner Mongolia, so it has the highest ratio to total NPP. Comparison
of our NPP with similar studies from conventional methods confirms the accuracy of our estimation.
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