常规土工合成材料蠕变特性仅考虑筋材拉伸状态。随着土工合成材料应用愈加广泛,其受力条件也愈加复杂。为研究土工织物在受到顶压力作用下的蠕变特性,研制了顶压蠕变试验装置。采用该装置对Mirafi PET 1300土工织物进行了CBR圆形顶破试...常规土工合成材料蠕变特性仅考虑筋材拉伸状态。随着土工合成材料应用愈加广泛,其受力条件也愈加复杂。为研究土工织物在受到顶压力作用下的蠕变特性,研制了顶压蠕变试验装置。采用该装置对Mirafi PET 1300土工织物进行了CBR圆形顶破试验以及40%、50%和60%三种荷载水平下的2400 h圆形顶压蠕变试验,计算了5、10、60和120 a设计年限在不同顶压面积应变下的顶压蠕变折减系数,并与常规拉伸蠕变折减系数对比,建立了顶压蠕变折减系数、设计年限与顶压面积应变三者的量化关系式,以预测顶压蠕变折减系数。结果表明,对于试验土工织物,顶压蠕变折减系数比常规拉伸蠕变折减系数大65.340%~148.496%;随设计年限的增加,顶压蠕变折减系数变化不大;在不同设计年限下,随顶压面积应变的增加,顶压蠕变折减系数保持平稳。为提升工程结构的安全性和耐久性,在土工合成材料受顶压作用情况下,建议设计采用顶压蠕变折减系数。展开更多
The effects of addition of calcium up to 4 wt.% on the microstructure and creep properties of Mg-4 Sn alloys were investigated by the impression creep test. Impression creep tests were performed in temperature range b...The effects of addition of calcium up to 4 wt.% on the microstructure and creep properties of Mg-4 Sn alloys were investigated by the impression creep test. Impression creep tests were performed in temperature range between 445 and 475 K under normalized stresses σ/G(where σ is the stress;G is the shear modulus) between 0.0225 and 0.035. Optical microscopy and scanning electron microscopy were used to study the microstructure of samples. It is observed that the addition of Ca more than 2 wt.% suppresses less stable Mg Sn2 phase, and instead forms more thermally stable phases of Ca-Mg-Sn and Mg2 Ca at the grain boundaries which improve the creep resistance of Mg-4 Sn alloys. According to the stress exponents(6.04<n<6.89) and activation energies(101.37 k J/mol<Q<113.8 k J/mol) which were obtained from the impression creep tests, it is concluded that the pipe diffusion climb controlled dislocation creep is the dominant creep mechanism.展开更多
Based on mineral component and in-situ vane shear strength of deep-sea sediment, four kinds of simulative soils were prepared by mixing different bentonites with water in order to find the best simulative soil for the...Based on mineral component and in-situ vane shear strength of deep-sea sediment, four kinds of simulative soils were prepared by mixing different bentonites with water in order to find the best simulative soil for the deep-sea sediment collected from the Pacific C-C area. Shear creep characteristics of the simulative soil were studied by shear creep test and shear creep parameters were determined by Burgers creep model. Research results show that the shear creep curves of the simulative soil can be divided into transient creep, unstable creep and stable creep, where the unstable creep stage is very short due to its high water content. The shear creep parameters increase with compressive stress and change slightly or fluctuate to approach a constant value with shear stress, and thus average creep parameters under the same compressive stress are used as the creep parameters of the simulative soil. Traction of the deep-sea mining machine walking at a constant velocity can be calculated by the shear creep constitutive equation of the deep-sea simulative soil, which provides a theoretical basis for safe operation and optimal design of the deep-sea mining machine.展开更多
In order to investigate the compression creep of two kinds of high-performance concrete mixtures used for prestressed members in a bridge,an experimental test under laboratory conditions was carried out.Based on the e...In order to investigate the compression creep of two kinds of high-performance concrete mixtures used for prestressed members in a bridge,an experimental test under laboratory conditions was carried out.Based on the experimental results,a power exponent function was used to model the creep degree of these high-performance concretes(HPCs) for structural numerical analysis,and two series parameters of this function for the HPCs were given with the optimum method of evolution program.The experimental data were compared with CEB-FIP 90 and ACI 92 models.Results show that the two code models both overestimate the creep degree of two HPCs,so it is recommended that the power exponent function should be used for the creep analysis of bridge structure.展开更多
GMT-sheet is used in automobile bumper with high rigidity and strength, and its joining strength is influenced by lap length, one of the joined molding conditions. Fracture strength was calculated by dividing fracture...GMT-sheet is used in automobile bumper with high rigidity and strength, and its joining strength is influenced by lap length, one of the joined molding conditions. Fracture strength was calculated by dividing fracture load with cross-sectional area. Total five repeated measurements were made to obtain the average value. Tensile test was conducted at room temperature for 10 specimens. In addition, the effect of compression ratio on creep and tensile performance during lap joined molding was discussed. With increasing lap length, the lap joining efficiency of GMT-sheet was increased. However, higher compression ratio reduced the joining efficiency. Creep test on GMT-sheet showed abrupt fracture without tertiary creep. This can be explained by the weak thermal resistance of the resin. If GMT-sheet was exposed to high temperature for a long time, it was easily failed by external force.展开更多
文摘常规土工合成材料蠕变特性仅考虑筋材拉伸状态。随着土工合成材料应用愈加广泛,其受力条件也愈加复杂。为研究土工织物在受到顶压力作用下的蠕变特性,研制了顶压蠕变试验装置。采用该装置对Mirafi PET 1300土工织物进行了CBR圆形顶破试验以及40%、50%和60%三种荷载水平下的2400 h圆形顶压蠕变试验,计算了5、10、60和120 a设计年限在不同顶压面积应变下的顶压蠕变折减系数,并与常规拉伸蠕变折减系数对比,建立了顶压蠕变折减系数、设计年限与顶压面积应变三者的量化关系式,以预测顶压蠕变折减系数。结果表明,对于试验土工织物,顶压蠕变折减系数比常规拉伸蠕变折减系数大65.340%~148.496%;随设计年限的增加,顶压蠕变折减系数变化不大;在不同设计年限下,随顶压面积应变的增加,顶压蠕变折减系数保持平稳。为提升工程结构的安全性和耐久性,在土工合成材料受顶压作用情况下,建议设计采用顶压蠕变折减系数。
文摘The effects of addition of calcium up to 4 wt.% on the microstructure and creep properties of Mg-4 Sn alloys were investigated by the impression creep test. Impression creep tests were performed in temperature range between 445 and 475 K under normalized stresses σ/G(where σ is the stress;G is the shear modulus) between 0.0225 and 0.035. Optical microscopy and scanning electron microscopy were used to study the microstructure of samples. It is observed that the addition of Ca more than 2 wt.% suppresses less stable Mg Sn2 phase, and instead forms more thermally stable phases of Ca-Mg-Sn and Mg2 Ca at the grain boundaries which improve the creep resistance of Mg-4 Sn alloys. According to the stress exponents(6.04<n<6.89) and activation energies(101.37 k J/mol<Q<113.8 k J/mol) which were obtained from the impression creep tests, it is concluded that the pipe diffusion climb controlled dislocation creep is the dominant creep mechanism.
基金Project(51274251)supported by the National Natural Science Foundation of China
文摘Based on mineral component and in-situ vane shear strength of deep-sea sediment, four kinds of simulative soils were prepared by mixing different bentonites with water in order to find the best simulative soil for the deep-sea sediment collected from the Pacific C-C area. Shear creep characteristics of the simulative soil were studied by shear creep test and shear creep parameters were determined by Burgers creep model. Research results show that the shear creep curves of the simulative soil can be divided into transient creep, unstable creep and stable creep, where the unstable creep stage is very short due to its high water content. The shear creep parameters increase with compressive stress and change slightly or fluctuate to approach a constant value with shear stress, and thus average creep parameters under the same compressive stress are used as the creep parameters of the simulative soil. Traction of the deep-sea mining machine walking at a constant velocity can be calculated by the shear creep constitutive equation of the deep-sea simulative soil, which provides a theoretical basis for safe operation and optimal design of the deep-sea mining machine.
文摘In order to investigate the compression creep of two kinds of high-performance concrete mixtures used for prestressed members in a bridge,an experimental test under laboratory conditions was carried out.Based on the experimental results,a power exponent function was used to model the creep degree of these high-performance concretes(HPCs) for structural numerical analysis,and two series parameters of this function for the HPCs were given with the optimum method of evolution program.The experimental data were compared with CEB-FIP 90 and ACI 92 models.Results show that the two code models both overestimate the creep degree of two HPCs,so it is recommended that the power exponent function should be used for the creep analysis of bridge structure.
文摘GMT-sheet is used in automobile bumper with high rigidity and strength, and its joining strength is influenced by lap length, one of the joined molding conditions. Fracture strength was calculated by dividing fracture load with cross-sectional area. Total five repeated measurements were made to obtain the average value. Tensile test was conducted at room temperature for 10 specimens. In addition, the effect of compression ratio on creep and tensile performance during lap joined molding was discussed. With increasing lap length, the lap joining efficiency of GMT-sheet was increased. However, higher compression ratio reduced the joining efficiency. Creep test on GMT-sheet showed abrupt fracture without tertiary creep. This can be explained by the weak thermal resistance of the resin. If GMT-sheet was exposed to high temperature for a long time, it was easily failed by external force.
