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991.
粘弹塑性统一本构模型理论 总被引:6,自引:1,他引:5
文章在已有的统一本构模型的基础上,将粘弹性变形引入到统一本构模型之中,成功地改善了材料过渡段的变形模拟情况。通过Hastelloy-X的变形模拟及与其它统一本构模型的变形模拟比较,证明了粘弹塑性统一本构模型的合理性。 相似文献
992.
Bettina Wolf William J. Frith Scott Singleton Manlio Tassieri Ian T. Norton 《Rheologica Acta》2001,40(3):238-247
The rheological behaviour of suspensions is influenced by many parameters, one of which is the particle shape. For rigid
particle suspensions a number of studies demonstrate the effects of the particle aspect ratio. Indeed, fibres are widely used
as rheology modifiers in different materials such as synthetic polymers. This work is concerned with testing the hypothesis
that regularly shaped particles with aspect ratios larger than one that are made of gelled biopolymers could be used as rheology
modifiers for biopolymer solutions. Biopolymers, and mixtures thereof are a widely used ingredient in foods and other products
with structure functionality. Tailoring rheology modifiers by morphology offers an alternative to using different biopolymers.
It is demonstrated how biopolymer suspensions with regular spheroidal, or cylindrical particle shapes can be produced by gelling
the droplet phase of a liquid two phase biopolymer mixture in a shear field. Biopolymers were chosen such that gelation is
initiated by cooling. Shear-cooling at constant stresses leads to the formation of ellipsoidal particles. Cylindrical particles
can be generated by stepping up the shear stress prior to gelation, i.e., stretching the droplet phase into fibrils, and trapping
the shape prior to break-up through gelation.
Morphologies and steady shear rheological data for suspensions of the two biopolymers gellan and κ-carrageenan with an internal
phase volume of 0.2 are reported. The influence of particle shape on relative viscosity is pronounced. At high shear stresses
particle orientation leads to decreased viscosity with increasing particle aspect ratio. In the low shear region, higher aspect
ratio suspensions show higher viscosities. Additionally, the material properties, including the interfacial tension, which
influence the suspension morphology are reported.
Received: 3 March 2000 Accepted: 22 August 2000 相似文献
993.
994.
Summary: This paper presents a computational study of phase separation‐phase ordering‐texturing in blends of polymer coils and rod‐like nematic liquid crystals under the presence of magnetic fields, using an extended version of the Matsuyama‐Evans‐Cates model (Phys. Rev. E 2000 , 61, 2977). This work demonstrates that demixing in these blends leads to droplet morphologies with tunable droplet shapes and director textures. In contrast to filled nematics, where solids are suspended in a nematic liquid crystal matrix, demixing in coil‐mesogenic rods blends leads to nematic emulsions, in which the deformable viscoelastic polymer drops are suspended in a nematic matrix. Under strong anchoring conditions, the imposition of a magnetic field leads to a director re‐orientation that due to strong anchoring produces a droplet shape change. Magnetic field‐induced shape transitions in these blends are shown to be second order with a finite critical field threshold that diverges as anchoring strength vanishes. A morphological‐texture diagram summarizes the magnetic field‐anchoring conditions that promote anisotropic shapes. This work presents additional material processing routes to design and control bi‐phasic morphologies in polymer‐liquid crystal blend.
995.
996.
997.
Based upon the theory of ardsotropic plates, the unsymmetrical large deformation equations of orthotropic circular plates were derived. By using Fourier series, the partial differential equations of this problem can be transformed into sets of nonlinear differential equations . And the procedure to solve the problem using the iterative method is given . 相似文献
998.
在地下抗爆结构动力计算中,结构变形速度的作用是非常突出的.考虑结构变形速度的作用,所建立的结构体系运动微分方程可以真实地描述结构振动的实际情况.文中通过一维平面波理论,导出了作用在结构周边上的荷载表达式,给出了地下曲杆结构动力分析的广义变分原理,同时还进行了数值计算结构的对比分析. 相似文献
999.
We present several families of exact solutions to a system of
coupled nonlinear Schr\"{o}dinger equations. The model describes a
binary mixture of two Bose--Einstein condensates in a magnetic trap
potential. Using a mapping deformation method, we find exact
periodic wave and soliton solutions, including bright and dark
soliton pairs. 相似文献
1000.
The molecular dynamics method was adopted to investigate the tension deformation for SWCNTs with different chiralities and radius. The results show that nanotubes have an extremely large breaking strain. Carbon nanotubes are completely ductile before their structural defects appear. Through tracing the evolution of the spacial configuration of a micro structural cell of SWCNTs, it is found that the torsion deformation results in the change of structural symmetry. Thus the load is no longer well distributed. The structural defects will occur with further loading. The systematic energy change of SWCNTs is observed. It can be seen that there is a structural transformation around the initial vacancy defects when the axial tension strain reaches a certain value. The two adjacent hexagons change to one pentagon and one heptagon (also called the Stone Wales transformation). The 5 7 configuration makes strain energy release, and the systematic energy falls. This configuration is more preferable from the viewpoint of the energy. The results also show that fewer defects have weak influence on the mechanical properties of SWCNTs under the present initial vacancy defect condition. 相似文献