Papers by Author: Zhuo Qiu Li

Abstract: The relationship between ceramic roller kiln simulation model building parameters and temperature field uniformity is extremely difficult work. In this paper, DEPSO-CFD, a system integrated of an algorithm of hybrid particle swarm (PSO) with Differential Evolution (DE) operator, termed DEPSO, and computational fluid dynamics (CFD), is proposed to meet the demand. And with the help of the efficient parallel calculation, the ceramic roller kiln temperature field uniformity is mainly researched by using Fluent and DEPSO algorithm. It proves that the system is of high speed and of excellent parameter exploration capability, and the final computational example is got; thus parallel-DEPSO-CFD is of great academic value and significant applicable value.

Abstract: Carbon fiber (CF) is an essential functional material focused on widely, especially in civil engineering. The mechano-electric character of carbon fiber layer based on the polymer-matrix and its sensing application to the pre-embedded crack detecting were experimentally discussed in this paper. Through the uniaxial tension the CF layer reveals a good performance by resistance changing with response to the loading. By three-points bending test, the crack of the structure would lead to an evident increasing of the resistance change ratio of CF layer. From the experimental results, the ratio of resistance increasing of CF layer laid on crack will be higher by 14.25% in average than that of CF layer with no crack laid. Thus carbon fiber mat composed with polymer will provides a new kind of potential sensor which can detect the defects of the structure.

Abstract: At present, the study of smart composite material of carbon fiber is mainly focused on the usage of the material pressure-resistant effect. The change of resistance reflects the force status of the structure and its performance mainly depends on the sensitivity of pressure-resistantance. Such composite’s sensitivity has a relationship with the sample preparation process. In this paper, the resin-based carbon fiber is improved so as to obtain a high sensitivity and good stability bundle of modified carbon fiber polymer-matrix composites. Clamp the samples of this material on the micro-tensile test table, the characteristics of mechanism pressure-resistant is analyzed by observing the fiber interface changes through SEM when loaded, combined with monotonic loading curve of the sample. With the electrical model of parallel circuit and normal distribution model and Weibull model, piezoresistivity model is established. Compared with the model curve and the experimental model, the mode is verified being a high accuracy.

Abstract: With epoxy reinforced by short carbon fiber mats, a skin-like strain sensor, polymer-matrix smart layer was developed, which can continuously cover the structural surface to sense strain for the whole filed. The smart layer was proved to be an effective strain sensor for tensile strain up to 0.8% by a monotonic tension experiment, exceeding this limit cause nonlinearity in the resistance response. The damage sensitivity of the smart layer was revealed by the monitoring for a FRP beam with prefabricated defect. Based on its sensitivities, the smart layers was applied in the health monitoring for a concrete beam under three-point bending, the result showed a good correlation between the resistance change of the smart layer and the load applied on the structure. The emergency of structure damage can be monitored by the turning point on the resistance-deflection curve of the smart layer.

Abstract: In this work, CCCW (cementitious capillary crystalline waterproofing materials) was added in CFRC (carbon fiber reinforced cement paste). Variations of electrical conductivity of CFRC with fiber contents (0.2%~2.0% by the weight of cement) and CCCW (3% by the weight of cement) were studied. The results showed that the resistivity of CFRC containing CCCW versus the concentration of carbon fiber curves had typical features of percolation phenomena. The percolation threshold was 1.2 wt.%. The relationship between resistance and compressive stress was repeatable in CFRC with carbon fiber content of 1.2 wt.%. The resistance decreased in nearly linearity to the compression stress during loading, and increased during unloading.

Abstract: Carbon fiber reinforced concrete (CFRC) structures exhibit both strain sensibility and temperature sensibility, which are coupled with each other when used in traffic or health monitoring for concrete structures. This coupling property results in inaccurateness of measured deformation. In this paper Four-probe Difference Method is used to detach the above two effects according to loaded conditions of structures and different characteristics of the two effects. The theoretical and experimental results indicate that the method is feasible and effective.

Abstract: Structural health monitoring (SHM) is becoming a popular topic. Carbon fiber reinforced concrete (CFRC) is an intrinsically smart material that can sense strain. The resistivity increases reversibly under tension and decreases under compression. A new skin-like sensor —cement-based smart layer had been put forward, which can serve as whole field strain sensor. The smart layer is satisfactorily consistent with concrete structure. The smart layer is a thin carbon fiber mat cementbased composite material layer with finite electrodes. It can cover the surface of concrete structure, and provide on-line reliable information about the deformation of whole concrete structure. The static characteristics of the new-type sensor had been researched. Its gage factor is 20-25 under tension and 25-30 under compression within the elastic deformation range. Furthermore the smart layer has satisfactory linearity and repeatability. In this paper, the sensor characteristics of the bare carbon fiber mat have been reached. The resistivity of carbon fiber mat has good agreement with strain under uniaxial tension. The gage factor can be up to 375, and the sensor limit can be up to 10000 microstrain. The strain and the fractional change in electrical resistance .R/R0 are totally reversible and reproducible under cyclic loading and amplitude-variable cyclic tensile loading.

Abstract: Based on the functional characteristics of carbon fiber reinforced concrete (CFRC), an improved infrared nondestructive testing method, to detect crack in CFRC by using infrared thermography, is presented in this paper. The principle is that when a CFRC specimen is applied a low voltage, crack existing in the specimen will result in non-homogeneous surface temperature distribution due to the electro-thermal effect of the material. Monitoring the temperature difference on the surface, the crack under the observed surface can be inspected by using infrared thermography. In theory, the mechanism causing the temperature difference comes down to an unsteady heat transfer problem with internal energy sources. In the case of the thermo-physical property of CFRC as given, the sensitivity of this method to the depth of the crack is analyzed by numerical computation.

Abstract: Cement structures such as bridges and dams often come into being distortion or exhibit excessive thermal stresses due to the sun radiation or freeze-thaw cycle. Therefore, temperature especially inner temperature difference or deformation of structures must be controlled or regulated sometimes in order to reduce thermal stresses or excessive deformation and to extend the life-span of structures. In this paper, the electro-thermal effects of smart cement are used to adjust temperature difference or deformation of concrete beams without the need of peripheral non-structural materials. Concrete beams for temperature and deformation adjustment were fabricated, and some experimental results as well as the related conclusions about temperature difference and deformation were produced. Based on these results, experiments of temperature difference or deflection adjustment are further conducted successfully. The research results in this paper are the bases of temperature and deformation adjustment for mass concrete structures. A new path will be broken to adjust temperature or deformation easily for some structures.