This paper presents an experimental study to determine the tensile properties of the envelope fabric Uretek3216L under biaxial cyclic loading.First the biaxial cyclic tests were carefully carried out on the envelope m...This paper presents an experimental study to determine the tensile properties of the envelope fabric Uretek3216L under biaxial cyclic loading.First the biaxial cyclic tests were carefully carried out on the envelope material to obtain the stress-strain data and the corresponding nonlinearity and orthotropy of the material were analyzed. Then for some determination options with different stress ratios the least squares method minimizing the strain terms was used to calculate the elastic constants from the experimental data.Finally the influences of the determination options with different stress ratios and the reciprocal relationship on the elastic constants were discussed.Results show that the orthotropy of the envelope material can be attributed to the unbalanced crimp of their constitutive yarns in warp and weft directions and the elastic constants vary noticeably with the determination options as well as the normalized stress ratios.In real design practice it is more reasonable to use constants determined for specific stress states in particular stress ratios depending on the project's needs.Also calculating the structures with two limitative sets of elastic constants instead of using only one set is recommendable in light of the great variety of the constant's values.展开更多
A newly designed TiAl alloy containing W,Nb,and B was produced through magnetic-flotation-melting method.Mass production of this TiAl-based alloy,15 kg ingot size,which is quite different from the 0.05 kg small ingot ...A newly designed TiAl alloy containing W,Nb,and B was produced through magnetic-flotation-melting method.Mass production of this TiAl-based alloy,15 kg ingot size,which is quite different from the 0.05 kg small ingot produced by arc-melting,has a large effect on the metallurgical properties,such as the grain size and the phase structures of the alloy.Heat treatments were carefully designed in order to reduce the amount of the high-temperature remaining β phase in the alloy,and to obtain optimal microstructures for mechanical behavior studies.A room-temperature ductility of 1.9% was obtained in the cast TiAl-based alloy after the appropriate heat treatment.The mechanical behavior of the large ingot through mass production of the TiAl-based alloy was largely improved by the alloy design and subsequent heat treatments.展开更多
The molecular conformation and the microstructure of the slenderized wool fibers have been studied by the Raman spectroscopy. The typical bands analyzed in this paper include the amideⅠand amide Ⅲ regions, the CC sk...The molecular conformation and the microstructure of the slenderized wool fibers have been studied by the Raman spectroscopy. The typical bands analyzed in this paper include the amideⅠand amide Ⅲ regions, the CC skeletal vibration region, and the SS and CS bond vibration regions. The experimental results show that ⅰ) the Raman spectroscopy can reveal the secondary structural transformation from αhelical to βpleated sheet begin at the early stage of stretching; ⅱ) the stretching mechanism of wool fibers can be divided into two different mechanisms, i.e. the secondary structural transformation and the slippage of the polypeptide chain; and ⅲ) the stretching leads to the increasing of the amount of the disordered conformation and the decreasing of the amount of SS bonds.展开更多
A theoretical estimation for the multiple-drawing has been derived under the consideration of fiber length distribution for the wool fiber stretching system. The functions of the roller drawing system and the paramete...A theoretical estimation for the multiple-drawing has been derived under the consideration of fiber length distribution for the wool fiber stretching system. The functions of the roller drawing system and the parameters in stretching process have also been analyzed. The theoretical algorithms have been verified by the experimental results and can be used for the estimation of fiber length and its distribution after the stretching.展开更多
The long-term creep behavior of polymer-matrix 3-D braided composites was studied by using the tensile creep test method, and the effect of braiding structure, braiding angle and fiber volume fraction were discussed. ...The long-term creep behavior of polymer-matrix 3-D braided composites was studied by using the tensile creep test method, and the effect of braiding structure, braiding angle and fiber volume fraction were discussed. The creep curve appears as expected, and can be defined two phases, namely, the primary phase and the secondary phase. For each sample, strain increases with time rapidly, and then the strain rate decreases and appears to approach a constant rate of change (steady-state creep). The experiment results show that the creep resistant properties are improved while the braiding angle decreases or the fiber volume fraction increases, and that the five-directional braiding structure offers better creep resistant properties than the four-directional braiding structure.展开更多
基金The National Natural Science Foundation of China(No.51278299,50878128)
文摘This paper presents an experimental study to determine the tensile properties of the envelope fabric Uretek3216L under biaxial cyclic loading.First the biaxial cyclic tests were carefully carried out on the envelope material to obtain the stress-strain data and the corresponding nonlinearity and orthotropy of the material were analyzed. Then for some determination options with different stress ratios the least squares method minimizing the strain terms was used to calculate the elastic constants from the experimental data.Finally the influences of the determination options with different stress ratios and the reciprocal relationship on the elastic constants were discussed.Results show that the orthotropy of the envelope material can be attributed to the unbalanced crimp of their constitutive yarns in warp and weft directions and the elastic constants vary noticeably with the determination options as well as the normalized stress ratios.In real design practice it is more reasonable to use constants determined for specific stress states in particular stress ratios depending on the project's needs.Also calculating the structures with two limitative sets of elastic constants instead of using only one set is recommendable in light of the great variety of the constant's values.
基金Project(11X-SP173V) supported by the U.S. Fossil Energy Materials ProgramProject supported by the U.S. National Science Foundation Combined Research-Curriculum Development(CRCD) ProgramProject(DE-AC05-00OR-22725 UT-Battelle,LLC) supported by Division of Materials Science and Engineering,Office of Basic Energy Science,U.S.Department of Energy
文摘A newly designed TiAl alloy containing W,Nb,and B was produced through magnetic-flotation-melting method.Mass production of this TiAl-based alloy,15 kg ingot size,which is quite different from the 0.05 kg small ingot produced by arc-melting,has a large effect on the metallurgical properties,such as the grain size and the phase structures of the alloy.Heat treatments were carefully designed in order to reduce the amount of the high-temperature remaining β phase in the alloy,and to obtain optimal microstructures for mechanical behavior studies.A room-temperature ductility of 1.9% was obtained in the cast TiAl-based alloy after the appropriate heat treatment.The mechanical behavior of the large ingot through mass production of the TiAl-based alloy was largely improved by the alloy design and subsequent heat treatments.
文摘The molecular conformation and the microstructure of the slenderized wool fibers have been studied by the Raman spectroscopy. The typical bands analyzed in this paper include the amideⅠand amide Ⅲ regions, the CC skeletal vibration region, and the SS and CS bond vibration regions. The experimental results show that ⅰ) the Raman spectroscopy can reveal the secondary structural transformation from αhelical to βpleated sheet begin at the early stage of stretching; ⅱ) the stretching mechanism of wool fibers can be divided into two different mechanisms, i.e. the secondary structural transformation and the slippage of the polypeptide chain; and ⅲ) the stretching leads to the increasing of the amount of the disordered conformation and the decreasing of the amount of SS bonds.
文摘A theoretical estimation for the multiple-drawing has been derived under the consideration of fiber length distribution for the wool fiber stretching system. The functions of the roller drawing system and the parameters in stretching process have also been analyzed. The theoretical algorithms have been verified by the experimental results and can be used for the estimation of fiber length and its distribution after the stretching.
文摘The long-term creep behavior of polymer-matrix 3-D braided composites was studied by using the tensile creep test method, and the effect of braiding structure, braiding angle and fiber volume fraction were discussed. The creep curve appears as expected, and can be defined two phases, namely, the primary phase and the secondary phase. For each sample, strain increases with time rapidly, and then the strain rate decreases and appears to approach a constant rate of change (steady-state creep). The experiment results show that the creep resistant properties are improved while the braiding angle decreases or the fiber volume fraction increases, and that the five-directional braiding structure offers better creep resistant properties than the four-directional braiding structure.