Papers by Keyword: Ultrasonic Attenuation

Abstract: Concrete is a complex porous material. This porosity comes from the air trapped during mixing and also from the free water that did not react with the cement. In this work, we varied the porosity rate in concrete specimens, in order to evaluate its effect on the acoustic and mechanical properties of the material during its maturation age. These test pieces were made according to EN 196-1: 2016 of different dimensions and with three mass ratios Water/Cement (W/C=0.45, W/C=0.50 and W/C=0.65). The ultrasonic measurements were done in the direct transmission mode, using 54 kHz nominal frequency transducers, transmitting in the longitudinal mode. The results showed an increase in the propagation velocity with the age of maturation for all W/C ratios and an overall decrease in its value with this ratio. On the other hand, the attenuation coefficient increased slightly with the frequency in a quasi-linear manner, while its overall value decreased with the age of maturity of the concrete. For comparison, a destructive method was used. This consisted of crushing tests to determine the compressive strength. This latter increased with the age of maturation of the concrete for all W/C ratios, but decreased when these ratios increased. These results showed the same trend as those obtained for the ultrasonic group velocity. This allowed us to deduce a correlation law between the acoustical and mechanical parameters for all ratios with a high determination coefficient. These investigations confirm the effectiveness of ultrasonic methods in evaluating the quality of concrete.

Abstract: It is important to monitoring the fine particles (PM2.5) in atmosphere as it threatens the public health all over the world. But the existing concentration measuring devices have shortcomings in speed and range. A novel fine particle concentration measuring system based on the ultrasonic attenuation was designed in this paper, which could help to solve the problem. Firstly the mechanism of ultrasonic attenuation in dust cloud was studied to verify the relationship between the concentration and the ultrasonic attenuation. Then the novel concentration measuring system was designed. The micro ultrasonic transducer array was introduced into the system, so the system can be sensitive as well as small. Finally, experiment was conducted to check the performance of this measuring system, and the results show that it could realize measurement quickly.

Abstract: In order to set solid particle phase distributed uniformly in the whole detection space， the McClements model and Bouguer -Lambert -Beer law model were applied to formulate the ultrasonic attenuation properties of gas-solid flow for pneumatic conveying fly ash. The theoretical relation between the ultrasonic attenuation coefficients and the flow parameters of gas/ solids two-phase flow was established. By numerical simulations, the alteration laws of the ultrasonic attenuation coefficients with particle volume fraction， ultrasonic frequency and particle size were analyzed. The results show that the higher the ultrasonic frequency was, the greater the attenuation coefficients were. The ultrasonic attenuation coefficients linearly increased with the increasing of the solid particles volume fraction. If some fixed frequency was chosen， the slopes of attenuation -volume fractions curves can be confirmed by just testing ultrasonic attenuation coefficients under two volume fractions. So that testing of particle volume fraction corresponding to arbitrarily ultrasonic attenuation coefficients can be achieved. If the fly ash particle sizes were in the domain of 10 -200 μm with the same volume fraction， the ultrasonic attenuation coefficients monotonically decreased with the increasing of the particle size. But if the fly ash particle size was higher than 200 μm， the ultrasonic attenuation coefficients were no longer sensitive to the solids particle size.

Abstract: This design is based on the theory of ultrasonic attenuation,design of pulp concentration is C8051F021 microcontroller as the core of the meter, And contains the ultrasonic transmitting circuit, receiving circuit, the power amplification circuit, detection shaping circuit, LCD display circuit, 485 communication circuit. In addition to the data processing by appropriate filtering software, shield the noise and clutter signal, the rich information of real-time display, and the measurement of data transmission in serial port to a PC through the analysis and comparison.

Abstract: This paper analysis principle of BLBL(Bouguer-Laanbert-Beer-Law) model, and introduce SiO2 physical parameters of the simulation experiments to verify the scope of the model and the expected value of the theoretical model. The model be applicable under the low concentrations and meets unrelated conditions. The model full-scattering method in the optics methods of measurement obtained consistent with the theoretical value.

Abstract: To compare the different effects under different excitation methods during the measurement on the particle size of silicon carbide (SiC), an experimental system has been established to get different signal excitations of burst wave, continuous wave and pulsed wave. Variable sound path method is adopted during the measurement to obtain the ultrasonic attenuation spectrum of SiC suspensions with two immersion transducers at four different mass concentrations under the same experimental condition. It is found that the ultrasonic attenuation coefficients excited by three different waves increase with increasing frequency and the tendency is approaching the same. The result calculated by a normalized spectrum of the optimal regularization methods shows that SiC particle size distribution under the three excitation methods is similar, which indicate that the different excitation methods on particle size characterization have almost no influence to result.

Abstract: Primeval TC4 titanium alloy was subjected to solution treatment at 1150°C for 1h, followed by water quenching, oil quenching, air cooling and furnace cooling, respectively. The pulse-echo method was carried out to measure ultrasonic longitudinal wave velocities (ν) and attenuation coefficients (α) of these heat-treated samples. The relationship between microstructures of different cooling rates and ultrasonic parameters such as ultrasonic longitudinal wave velocities (ν) and attenuation coefficients (α) was investigated. The results show that the microstructures of heat-treated TC4 alloy were α phase and β boundaries, and the ultrasonic longitudinal velocities and attenuation coefficients of these heat-treated samples, in turn, increased with reducing the cooling rate from water quenching to furnace cooling.

Abstract: Ultrasonic attenuation coefficient is firstly calculated utilizing the finite difference time domain method based on a novel 2-D RVM for carbon fiber reinforced plastic (CFRP) composite materials. The results show that the void morphology has detrimental effect on ultrasonic attenuation. Even at the fixed porosity, ultrasonic attenuation coefficient fluctuates due to the randomness of void morphology in CFRP composite materials. This work significantly helps to understand ultrasonic scattering mechanism of voids and formulation of CFRP composite material properties.

Abstract: TC11 titanium alloy (Ti-6Al-3Mo-1.2Zr-0.3Si) was subjected to solution treatment above β-phase field solution for 1 h with different cooling rates, such as water quenching, oil quenching, air cooling and furnace cooling, and gained four different microstructures. The relationship between microstructures and ultrasonic parameters such as ultrasonic longitudinal wave velocities (ν) and attenuation coefficients (α) was investigated. The results show that ultrasonic longitudinal velocities and attenuation coefficients increase with reducing the cooling rate from water quenching to furnace cooling. The hardness of these microstructures exhibits an opposite behavior to longitudinal wave velocity and ultrasonic attenuation coefficient.

Abstract: Using ultrasonics, acoustic characteristics of Pd40Cu30P20, Zr55Cu30Al10Ni5, Zr65Pd12.5Ni10Al7.5 Cu5, Cu55Zr30Ti10Pd5, Cu45Zr20Hf25Ag10 and Ti41.5Cu42.5Ni7.5Hf5Zr2.5Sn1 glassy alloys were examined in terms of complex elasticity. The order of bulk modulus (K), Lamè parameter (λ ), Young (E ) and shear (G ) moduli of the glassy alloys is monopoltical character of glassy alloys, except for polymers and rubbers. For metals and alloys, ceramics, polymers and glassy alloys, Poison’s ratio correlates well to ratio G /K. Complex elasticity indicates that viscoelasticity of the glassy alloys is predominated by volumetric motion.