The present work evaluated the properties of modified concrete using polyethylene terephthalate (PET) bottle waste as a partial replacement for coarse aggregate. Modified concrete samples were designed using a water/c...The present work evaluated the properties of modified concrete using polyethylene terephthalate (PET) bottle waste as a partial replacement for coarse aggregate. Modified concrete samples were designed using a water/cement (W/C) ratio of 0.50 and varying percentages of PET replacement (3%, 7%, 10%, and 15% by volume). Dreux Gorisse’s formulation approach was used to make the final products, and the mechanical properties of the samples were determined using Controlab presses. This modified concrete with PET chips has shown that with a 10% replacement of PET chips, the fresh density decreases by 3.56%, and the hardened state density decreases by 2.01%. The water absorption and thermal conductivity of the formulated concretes decreased. However, the results showed that the slump of these fresh concretes increased as the percentage of plastic aggregate replacement increased. Based on the results, incorporating PET aggregates into concrete contributes to good workability, and lightweight concrete structures, and provides some thermal comfort in concrete structures.展开更多
Metal particles such as aluminum（ Al）,magnesium（ Mg）,boron（ B） and nickel（ Ni）,as well as Mg/Al alloy（ Mg/Al = 3/4） are currently the most widely used ingredients in modified doublebase propellants. In this ...Metal particles such as aluminum（ Al）,magnesium（ Mg）,boron（ B） and nickel（ Ni）,as well as Mg/Al alloy（ Mg/Al = 3/4） are currently the most widely used ingredients in modified doublebase propellants. In this contribution,the combustion properties of the metal species are studied by means of the high-speed photography technique and the non-contact wavelet-based measurement of flame temperature distribution. The combustion process of the Al,Mg and Mg/Al samples shows both gas phase reaction and surface oxidation,which yield volatile and nonvolatile products,corresponding to the oxide and suboxide respectively. However,the combustion of B and Ni shows only gas phase reaction,due to their high melting point as well as high enthalpy of vaporization. In addition to the experiments,a hypothetical combustion model has been proposed to clarify the combustion characteristics of metal species in modified double-base propellants.展开更多
Large amounts of used rubber tires are discarded annually. A long time is needed for them to degrade naturally. This poses two major problems: environmental pollution and wastage of valuable rubber. On the other hand,...Large amounts of used rubber tires are discarded annually. A long time is needed for them to degrade naturally. This poses two major problems: environmental pollution and wastage of valuable rubber. On the other hand, with the harm of vibration and noise widely recognized, desires to control them intensify. As an important means of vibration control, viscoelastic damping technology has advanced greatly. The need for cheap and high quality viscoelastic damping materials increases rapidly. This paper made a trial to use ground rubber tire (GRT) recovered from old tires to make damping materials. The GRT is treated specially first. Then it was pressed into slabs and vulcanized. Finally, the product was cut into test samples. An Oberst beam was used to determine the loss factor βand storage modulus E. Results show that the damping materials exhibit good damping α-bility.展开更多
In order to improve the friction-wear properties of the C/C composites for aircraft brake pairs, the fric-tion behavior of samples with infiltrating Si was investigated. The influence of Si smearing thickness on frict...In order to improve the friction-wear properties of the C/C composites for aircraft brake pairs, the fric-tion behavior of samples with infiltrating Si was investigated. The influence of Si smearing thickness on frictionproperties was studied in detail. The results show that with the increase of Si smearing thickness and β-SiC content,the friction coefficient reduces from 0.40 to 0.30; the linear wear of stators increases from 2.0 μm to 18.9 μm percycle, and that of rotors increases from 1.4 μm to 22.6 μm per cycle; mass wear of stators increases from 20.6 mgto 126.9 mg per cycle, and that of rotors increases from 13.7 mg to 166.2 mg per cycle. On the other hand, whena large number of inhomogeneous β-SiC particulates are performed, friction surfaces of the samples flake off layer bylayer and many nicks are observed.展开更多
In this study, free and forced vibration analysis of nano-composite rotating pressurized microbeam reinforced by carbon nanotubes （CNTs） under magnetic field based on modify couple stress theory （MCST） with temper...In this study, free and forced vibration analysis of nano-composite rotating pressurized microbeam reinforced by carbon nanotubes （CNTs） under magnetic field based on modify couple stress theory （MCST） with temperature-variable material propertiesis presented. Also, the boundary conditions at two ends of nano-composite rotating pressurized microbeam reinforced by CNTs are considered as simply supported. The governing equations are obtained based on the Hamilton＇s principle and then computed these equations by using Navier＇s solution. The magnetic field is inserted in the thickness direction of the nano-composite microbeam. The effects of various parameters such as angular velocity, temperature changes, and pressure between of the inside and outside, the magnetic field, material length scale parameter, and volume fraction of nanocomposite microbeam on the natural frequency and response systemare studied. The results show that with increasing volume fraction of nano-composite microbeam, thickness, material length scale parameter, and magnetic fields, the natural frequency increases. The results of this research can be used for optimization of micro-structures and manufacturing sensors, displacement fluid, and drug delivery.展开更多
文摘The present work evaluated the properties of modified concrete using polyethylene terephthalate (PET) bottle waste as a partial replacement for coarse aggregate. Modified concrete samples were designed using a water/cement (W/C) ratio of 0.50 and varying percentages of PET replacement (3%, 7%, 10%, and 15% by volume). Dreux Gorisse’s formulation approach was used to make the final products, and the mechanical properties of the samples were determined using Controlab presses. This modified concrete with PET chips has shown that with a 10% replacement of PET chips, the fresh density decreases by 3.56%, and the hardened state density decreases by 2.01%. The water absorption and thermal conductivity of the formulated concretes decreased. However, the results showed that the slump of these fresh concretes increased as the percentage of plastic aggregate replacement increased. Based on the results, incorporating PET aggregates into concrete contributes to good workability, and lightweight concrete structures, and provides some thermal comfort in concrete structures.
基金Supported by the Science and Technology on Combustion and Explosion Laboratory Foundation(9140C350319140C35161)
文摘Metal particles such as aluminum（ Al）,magnesium（ Mg）,boron（ B） and nickel（ Ni）,as well as Mg/Al alloy（ Mg/Al = 3/4） are currently the most widely used ingredients in modified doublebase propellants. In this contribution,the combustion properties of the metal species are studied by means of the high-speed photography technique and the non-contact wavelet-based measurement of flame temperature distribution. The combustion process of the Al,Mg and Mg/Al samples shows both gas phase reaction and surface oxidation,which yield volatile and nonvolatile products,corresponding to the oxide and suboxide respectively. However,the combustion of B and Ni shows only gas phase reaction,due to their high melting point as well as high enthalpy of vaporization. In addition to the experiments,a hypothetical combustion model has been proposed to clarify the combustion characteristics of metal species in modified double-base propellants.
文摘Large amounts of used rubber tires are discarded annually. A long time is needed for them to degrade naturally. This poses two major problems: environmental pollution and wastage of valuable rubber. On the other hand, with the harm of vibration and noise widely recognized, desires to control them intensify. As an important means of vibration control, viscoelastic damping technology has advanced greatly. The need for cheap and high quality viscoelastic damping materials increases rapidly. This paper made a trial to use ground rubber tire (GRT) recovered from old tires to make damping materials. The GRT is treated specially first. Then it was pressed into slabs and vulcanized. Finally, the product was cut into test samples. An Oberst beam was used to determine the loss factor βand storage modulus E. Results show that the damping materials exhibit good damping α-bility.
基金Project [1998(1817)] supported by the National High-Technology for Industrial Development of China
文摘In order to improve the friction-wear properties of the C/C composites for aircraft brake pairs, the fric-tion behavior of samples with infiltrating Si was investigated. The influence of Si smearing thickness on frictionproperties was studied in detail. The results show that with the increase of Si smearing thickness and β-SiC content,the friction coefficient reduces from 0.40 to 0.30; the linear wear of stators increases from 2.0 μm to 18.9 μm percycle, and that of rotors increases from 1.4 μm to 22.6 μm per cycle; mass wear of stators increases from 20.6 mgto 126.9 mg per cycle, and that of rotors increases from 13.7 mg to 166.2 mg per cycle. On the other hand, whena large number of inhomogeneous β-SiC particulates are performed, friction surfaces of the samples flake off layer bylayer and many nicks are observed.
基金the Iranian Nanotechnology Development Committee for their financial supportthe University of Kashan (463855/7)
文摘In this study, free and forced vibration analysis of nano-composite rotating pressurized microbeam reinforced by carbon nanotubes （CNTs） under magnetic field based on modify couple stress theory （MCST） with temperature-variable material propertiesis presented. Also, the boundary conditions at two ends of nano-composite rotating pressurized microbeam reinforced by CNTs are considered as simply supported. The governing equations are obtained based on the Hamilton＇s principle and then computed these equations by using Navier＇s solution. The magnetic field is inserted in the thickness direction of the nano-composite microbeam. The effects of various parameters such as angular velocity, temperature changes, and pressure between of the inside and outside, the magnetic field, material length scale parameter, and volume fraction of nanocomposite microbeam on the natural frequency and response systemare studied. The results show that with increasing volume fraction of nano-composite microbeam, thickness, material length scale parameter, and magnetic fields, the natural frequency increases. The results of this research can be used for optimization of micro-structures and manufacturing sensors, displacement fluid, and drug delivery.
