等压幕墙等压性能及检测方法的研究

等压幕墙是近年来出现的一种新的幕墙形式,已广泛应用到工程中。等压幕墙的主要应用形式为开敞式的金属幕墙、陶板幕墙,根据"雨幕等压原理"进行设计,但国内没有相关的性能评价和试验检测。本文在研究国外检测标准的基础上,进行了等压幕墙等压性能评价和检测方法的研究。

等压幕墙等压性能及评价方法的研究

本文介绍了等压幕墙的发展及其国内外应用的情况。分析了压力均衡原理及其在建筑幕墙上的应用,进而总结了影响空腔压力的因素,为等压幕墙的设计提供了技术支持。最后提出了等压幕墙等压性能检测方法和性能要求。

Effects of second phases on mechanical properties and martensitic transformations of ECAPed TiNi and Ti-Mo based shape memory alloys

TiNi and Ti-based shape memory alloys were processed by equal channel angular pressing （ECAP） at 673-773 K along Bc route to obtain ultrafine grains for increasing the strength of parent phase and improving the functional properties. The effects of both thermodynamically stable and metastable second phases on the mechanical properties and martensitic transformations of these alloys were investigated. It is found that thermodynamically stable Ti2Ni phase has no effect on martensitic transformation and superelasticity of Ti-rich TiNi alloy, thermodynamically stable α phase is harmful for ductility of Ti-Mo-Nb-V-Al alloy, but metastable Ti3Ni4 phase is effective for R phase transformation, martensitic transformation and superelasticity of Ni-rich TiNi alloy. The mechanisms of the second phases on the martensitic transformations and mechanical properties were discussed.

Uniaxial compressive behavior of equal channel angular pressing Al at wide temperature and strain rate range

Uniaxial compressive experiments of ultrafine-grained Al fabricated by equal channel angular pressing(ECAP) method were performed at wide temperature and strain rate range. The influence of temperature on flow stress, strain hardening rate and strain rate sensitivity was investigated experimentally. The results show that both the effect of temperature on flow stress and its strain rate sensitivity of ECAPed Al is much larger than those of the coarse-grained Al. The temperature sensitivity of ultrafine-grained Al is comparatively weaker than that of the coarse-grained Al. Based on the experimental results, the apparent activation volume was estimated at different temperatures and strain rates. The forest dislocation interactions is the dominant thermally activated mechanism for ECAPed Al compressed at quasi-static strain rates, while the viscous drag plays an important role at high strain rates.

Effect of processing routes on microstructure and mechanical properties of 2014 Al alloy processed by equal channel angular pressing

Al-Cu alloy was deformed through equal channel angular pressing(ECAP) by routes A,Ba,Bc and C up to 5 passes.ECAP was done using a 90° die for three different conditions,namely 1) as received,2) solutionised at 768 K for 1 h and 3) solutionised at 768 K for 1 h + aged at 468 K for 5 h.The microstructure,microhardness and tensile strength were studied for all the three conditions and four routes.Significant improvement in hardness(HV 184 after five passes) and strength(602 MPa after three passes) was observed in solutionised and aged 2014 Al alloy deformed through route Bc.Microstructure evolution was reasonably equiaxed in route Bc with aspect ratio of 1.6.Solutionised and aged 2014 Al alloy deformed through route Bc was identified to have better microstructure and mechanical property than the other processing routes and conditions.

Effect of ECAP on microstructure and tensile properties of A390 aluminum alloy

The purpose of the present research is to determine the tensile strength and elongation of the A390 alloy processed by ECAP and to reveal the relationship between the microstructure and tensile properties. Optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used for microstructural analysis of the samples. The results of the mechanical testing showed that the ultimate tensile strength (UTS) increased from 142 MPa for the as-cast sample to 275 MPa for the sample after the third ECAP pass. Increasing the ECAP passes up to 4 led to a remarkable enhancement of elongation compared with the as-cast sample. It was found that the improvement of strength and ductility of A390 alloy with increasing the number of ECAP passes was attributed to the homogenous distribution of particles, reduction of particle size, and elimination of voids especially adjacent to the primary silicon particles. The results of fractography demonstrated that when the number of ECAP passes increased to 4, the uniform round dimples formed and the relatively brittle as-cast sample transformed to a ductile alloy.

Influence of ECAP as grain refinement technique on microstructure evolution, mechanical properties and corrosion behavior of pure aluminum

Pure aluminum samples were processed by equal channel angular pressing（ECAP） up to 10 passes at room temperature. The effects of the ECAP number of passes on the microstructure evolution, the mechanical properties, deformation homogeneity and corrosion behavior of the processed samples were fully investigated. The imposed strain resulted in an obvious reduction in the grain size from 390 μm before ECAP down to 1.8, 0.4, and 0.3 μm after ECAP up to 2, 4 and 10 passes, respectively. The microhardness, deformation homogeneity and tensile strength were increased while the elongation decreased with the increase of ECAP number of passes. Immersion tests, open circuit potential, Tafel polarization, cyclic polarization and potentiostatic measurements in 3.5% Na Cl solution revealed an obvious improvement in the corrosion resistance of ECAP processed samples compared with the as-cast sample. The increase of the number of passes can be used successfully in producing ultra-fine grained（UFG） bulk pure aluminum sample with a high misorientation angle, reasonably high mechanical properties and corrosion resistance.

Effect of pressure on the performance of plasma synthetic jet actuator

The effects of the ambient air pressure level on the performance of plasma synthetic jet actuator have been investigated through electrical and optical diagnostics.Pressures from 1 atm down to 0.1 atm were tested with a 10 Hz excitation.The discharge measurement demonstrates that there is a voltage range to make the actuator work reliably.Higher pressure level needs a higher breakdown voltage,and a higher discharge current and energy deposition are produced.But when the actuator works with the maximum breakdown voltage,the fraction of the initial capacitor energy delivered to the arc is almost invariable.This preliminary study also confirms the effectiveness of the plasma synthetic jet at low pressure.Indeed,the maximum velocities of the precursor shock and the plasma jet induced by the actuator with maximum breakdown voltage are independent of the ambient pressure level;reach about 530 and 460 m/s respectively.The mass flux of the plasma jet increases with ambient pressure increasing,but the strength of the precursor shock presents a local maximum at 0.6 atm.