含氯对位芳香族聚酰胺溶液流变特性研究

采用ARES-RFS流变仪研究了低温缩聚法制备的含氯对位芳香族聚酰胺(Cl-PPTA)溶液的流变特性,讨论了Cl-PPTA浓度、Cl-PPTA相对分子质量及温度对溶液流变特性的影响,并运用Cox-Merz关系式研究了稳态剪切粘度(ηa)和动态复数黏度(η*)的相互关系。结果表明:Cl-PPTA溶液为切力变稀的非牛顿流体;随着溶液中Cl-PPTA浓度和相对分子质量的增加,温度的降低,溶液的非牛顿性增加;Cl-PPTA浓度越高,相对分子质量越大,则溶液黏流活化能(△Eη)越大;随着Cl-PPTA浓度和相对分子质量增加,相应的储能模量(G')、损耗模量(G″)和η*越大;Cl-PPTA溶液浓度或温度增大时,在一定的剪切速率(γ)和角频率(ω)范围内,ηa和η*两曲线出现了重叠区域,仅在较高或较低的γ和ω时,两曲线出现偏离,Cl-PPTA溶液的流变特性符合Cox-Merz关系式。

Study on the rheology of coal-oil slurries during heating at high pressure

Using the self-developed viscosity measuring device, the viscosity variations of coal-oil slurries with temperature increasing during coal-oil co-processing were studied. The results show that the viscosity of coal-oil slurries prepared by different kinds of oil varies differently during heating. The viscosity of the coal-oil slurry prepared by the catalytic cracking slurry （FCC） generally decreases during heating. However, the viscosity of the coal-oil slurry prepared by the high-temperature coal tar （CT） will peak at 338 ℃ during heating. The differences in viscosity variations of coal-oil slurries are analyzed. In addition to the temperature, the properties of the solvents and coal are the main influencing factors. Because the used coal contains a large number of polar functional groups, the swelling behavior of the coal in polar solvent （CT） is stronger than that in non-polar solvent （FCC）. The swelling effect of the coal can result in the appearance of the viscosity peak. Therefore, before 100 ~C, the solvent molecules entering into the coal pores is the main influencing factor of coal-oil slurries viscosity variations. After 100 ℃, the increasing of particle size of coal particles is the main influencing factor of coal-oil slurries viscosity variations.

Rheological properties of surrounding rock in deep hard rock tunnels and its reasonable support form

Second lining stability, which is the last protection in tunnel engineering, is critically important. The theological properties of the surrounding rock heavily affect second lining stability. In this work, we used laboratory triaxial compressive rheological limestone tests to study nonlinear creep damage characteristics of surrounding rock mass in construction projects. We established a nonlinear creep damage constitutive model for the rock mass, as well as a constitutive model numerical implementation made by programming. Second, we introduced a new foam concrete with higher compression performance and good ductility and studied its mechanical properties through uniaxial and triaxial tests. This concrete was used as the filling material for the reserved deformation layer between the primary support and second lining. Finally, we proposed a high efficiency and accuracy staged optimization method. The minimum reserved deformation layer thickness was established as the optimization goal, and the presence of plastic strain in the second lining after 100 years of surrounding rock creep was used as an evaluation index. Reserved deformation layer thickness optimization analysis reveals no plastic strain in the second lining when the reserved deformation minimum thickness layer is 28.50 cm. The results show that the new foam concrete used as a reserved deformation layer filling material can absorb creep deformation of surrounding rock mass, reduce second lining deformation that leads to plastic strain, and ensure long-term second lining stability.

Nonlinear dynamic characteristics of magneto-rheological visco-elastomers

The smart magneto-rheological visco-elastomer (MRVE) has a promising application to vibration control.Its dynamic characteristics are described by complex moduli which are applicable to linear dynamics.However,experimental results show remarkable nonlinear relations between force and deformation for certain large deformations,and the nonlinear dynamic modeling needs to be developed.The present study focuses on the nonlinear dynamic characteristics of MRVE.The MRVE was fabricated and specimens were tested to show nonlinear mechanical properties and dynamic behaviors.The nonlinear effect induced by applied magnetic fields was investigated.A phenomenological model for the dynamic behaviors of MRVE was proposed to describe the nonlinear elasticity,linear damping and hysteretic effect,and the corresponding equivalent linear model in the frequency domain was also given for small deformations.The proposed model is applicable to the dynamics and control analysis of composite structures with MRVE.