Immersion Ultrasonic Method Research Articles

Design and experimental verification of phase-reversal Fresnel lens for contact stress characterization

The accurate characterization of the contact stress on the mating surfaces of assembly components is a key means to ensure the assembly accuracy and operational safety of aero-engines. In this paper, a phase-reversal Fresnel lens for contact stress characterization is designed to solve the problem of low spatial resolution of contact stress characterization by the non water immersion ultrasonic method. The phase-reversal Fresnel lens is used to focus the ultrasonic wave on the mating surface of the assembly components to improve the spatial resolution of the contact stress characterization. The finite element simulation method is used to analyze the influence of the number of lens rings, the piezoelectric plate's diameter, the lens's thickness, and the groove depth on the focusing characteristics of Fresnel lenses. The power spectrum peak is used to analyze the residual reflected wave energy of the mating surface. According to the correlation between the residual reflected wave energy and the contact stress, a correlation model between the two is built to realize the characterization of the contact stress. This study provides a promising method for the characterization of contact stress on the mating surface of aero-engine assembly components by non water immersion focused ultrasound.

Calculation and Lubrication Characteristics of Cylindrical Roller Bearing Oil Film with Consideration of Thermal Effects

Aiming at the problem of how the thermal characteristics of cylindrical roller bearings affect the lubrication characteristics of bearings under actual working conditions, the influence of parameters such as speed and load on the lubrication characteristics of cylindrical roller bearings under thermal effects is analyzed. The numerical calculation method combining the quasi-static model of cylindrical roller bearing and the thermal elastohydrodynamic lubrication model is adopted. The effects of rotational speed, load and thermal effect on the lubrication performance of the bearing and the lubrication state under certain oil supply conditions were analyzed via numerical model calculation. The oil film thickness was measured via an immersion ultrasonic method to verify the correctness of the model. The results show that the larger the bearing speed, the larger the central film thickness and the minimum film thickness. At the same time, the thermal effect on the film thickness is more obvious; the greater the load, the greater the maximum oil film pressure. The film thickness gradient in the inlet region is greatly reduced, but the thermal effect has no obvious effect on the overall film thickness. In addition, there is a critical value of effective lubrication film thickness for each set of operating parameters. When the actual film thickness is equal to the critical value, the bearing lubrication state is at its best; the numerical simulation results are compared with the experimental values. Under the calculation conditions, the maximum error at the measuring point is within 10%, which meets the error requirements and provides a theoretical basis for revealing the bearing lubrication mechanism.

Comparative Study of Bismuth Ferrite Deposition Method on TiO2 Nanotube and Performance of Hydrogen Evolution in a Photoelectrochemical Dye-Sensitized Solar Cell Tandem System

Hydrogen is a renewable and environmentally friendly energy source that can replace fossil fuels by utilizing solar energy through water splitting. The hydrogen production was conducted in this research by using a tandem system of dye-sensitized solar cell–photoelectrochemical cell (DSSC–PEC) and a TiO2 nanotube coated with BiFeO3 (BiFeO3/TNT) as a photoanode in the PEC. The deposition of BiFeO3 on TNT was prepared using the following three methods: successive ionic layer adsorption and reaction (SILAR), ultrasonication-assisted SILAR, and ultrasonic– immersion method by varying the number of deposition cycles in each method. In this study, the optimum cycles for SILAR, ultrasonication-assisted SILAR, and ultrasonic–immersion methods were 15, 5, and 3, respectively. Results show that the BiFeO3 deposited on TNT using the ultrasonic–immersion method with three cycles (BiFeO3/TNT_UI3) demonstrates the best photoelectrochemical activity. The tandem system comprises BiFeO3/TNT_UI3 photoanode and Pt-coated TNT dark cathode PEC cell connected to TNT/N719-based DSSC with an efficiency of 1.27%. The constructed DSSC–PEC system could produce 3.11 × 10−6 mol hydrogen in 6 h with a solar-to-hydrogen (STH) efficiency of 0.0033% in an H-type reactor filled with 0.5 M H2SO4 electrolyte.

Preparation of a Heterogeneous Catalyst CuO-Fe2O3/CTS-ATP and Degradation of Methylene Blue and Ciprofloxacin

A heterogeneous particle catalyst (CuO-Fe2O3/CTS-ATP) was synthesized via injection molding and ultrasonic immersion method, which is fast and effective. The particle catalyst applied attapulgite (ATP) wrapped by chitosan (CTS) as support, which was loaded dual metal oxides CuO and Fe2O3 as active components. After a series of characterizations of catalysts, it was found that CuO and Fe2O3 were successfully and evenly loaded on the surface of the CTS-ATP support. The catalyst was used to degrade methylene blue (MB) and ciprofloxacin (CIP), and the experimental results showed that the degradation ratios of MB and CIP can reach 99.29% and 86.2%, respectively, in the optimal conditions. The degradation mechanism of as-prepared catalyst was analyzed according to its synthesis process and ∙OH production, and the double-cycle catalytic mechanism was proposed. The intermediate products of MB and CIP degradation were also identified by HPLC-MS, and the possible degradation pathways were put forward.

Noncontact Laser Ultrasound Detection of Cracks Using Hydrophone.

We present a noncontact, non-immersion ultrasonic inspection method. A broadband ultrasound signal generated by a pulsed laser was measured using a hydrophone. The generated ultrasound signals propagated through the specimen and received a signal from the hydrophone in the water. Soldered chip ceramic capacitors, resistors, and surface-mount-type chip amplifiers were used as experimental specimens. A polydimethylsiloxane layer was used to prevent the specimen from being impacted by contact with water. The presence of a crack in the middle of the specimen resulted in an air layer, and the intermediate air layer reduced the magnitude of the signal transmitted owing to impedance mismatch. Using this principle, the cracks in each specimen could be distinguished. The image contrast ratio derived from the proposed method is approximately two to three times higher than that derived using the conventional immersion ultrasonic method. These results show that the proposed method can replace existing immersion-type ultrasound transmitted images.

Numerical and Experimental Modeling of Spot Welding Defects by Ultrasonic Testing on Similar Sheets and Dissimilar Sheets

This paper investigates the impact of defects on similar sheets and dissimilar sheets used in the automotive industry. Spot welding is one of the types of resistance welding used in this experiment for sheet welding. The thickness of sheets welded by the spot welding method can be between 0.5 and 3 mm. In this paper, the simulation is performed by finite element method for non-destructive tests on spot welding. This study investigated the propagation of ultrasonic waves in two similar layers of stainless steel and galvanized stainless steel sheets and two dissimilar layers of stainless steel sheets and galvanized stainless steel sheets in different thicknesses. This test was performed by ultrasonic immersion method and the intensity and amplitude of the reaction of the resulting defect waves and its effect on the results were also investigated. Due to the performance of finite element method softwares, Comsol Multiphysics software because of its high accuracy used. It has been studied various factors and conditions including excitation frequency, boundary conditions, the most suitable position for the probr Fto stimulate the waves, focused or unfocused waves in the simulation, sensitivity analysis of mesh size and appropriate mesh size for simulation. In this paper, the joint of similar sheets and dissimilar sheets is investigated. For this performance, the average relative error that can meet the industrial requirement is mentioned. The results of the simulation with the results of the experimental test They were compared and investigated And with the amount of error tests, have acceptable results and it can be used with the error specified and can meet the needs of the automotive industry.

Effect of distribution of polytetrafluoroethylene on durability of gas diffusion backing in proton exchange membrane fuel cell

Gas diffusion backing (GDB) in proton exchange membrane fuel cell played an important role in conducting electricity, conducting air and draining water, and its durability had not been widely valued. In order to improve its durability, the ultrasonic immersion method was tried during the hydrophobic treatment of GDB and the characteristic parameters of the GDBs by different immersion methods and their effects on the performance of the single fuel cell were compared by scanning electron microscopy, sectional fluorine line-scanning and map-scanning, pore size distribution, gas permeability and fuel cell performance. Besides, the hydrophobic stability of the GDBs by different immersion methods was measured by potentiostatic oxidation and ultrasonic water washing tests. It was found that ultrasonic immersion method improved the content and the uniform distribution of polytetrafluoroethylene (PTFE) in the section of GDB, resulting in the better fuel cell performance and hydrophobic stability.

The polymeric ionic liquids/mesoporous alumina composites: Synthesis, characterization and CO2 capture performance test

The CO2 capture materials and technology have received much attention in recent years due to the environmental deterioration caused by the greenhouse gas emissions. Several imidazolium polymeric ionic liquids (PILs) were synthesized and immobilized on mesoporous γ-Al2O3 (MA) using ultrasonic immersion method. The prepared adsorbents were characterized by FT-IR, 1H NMR, EA, TGA, SEM, XRD, BET and TEM, indicating the successful synthesis of the desired PILs/MA. The CO2 adsorption capacity was investigated under different loading ratios, temperatures, pressures and CO2 flow rates, whose optimal adsorption conditions were 1/1, 313 K, 5 bar and 10 mL/min, respectively. Moreover, the adsorption curves for P[VCIm]Cl/MA were coincident with pseudo-second order model, and the CO2 adsorption kinetics model was calculated and obtained. Compared with P[VRIm]Cl and P[VEIm]Cl, P[VCIm]Cl/MA demonstrated an outstanding adsorption amount of 0.562 mmol/g under the suitable conditions, and its regeneration efficiency could achieve 94.8% after 5 times cycle.

Validating a micromechanical modelling scheme for predicting the five independent viscoelastic constants of unidirectional carbon fibre composites

In this paper we experimentally validate a new micromechanical modelling scheme for predicting the five independent viscoelastic constants of a unidirectional carbon fibre epoxy resin composite. This study has built on a number of previous papers by these authors, where extensive finite element calculations were used to validate a much more easily implemented, classical analytical micromechanical approach for predicting the viscoelastic properties of composite materials. For formulating the viscoelastic predictions, the elastic-viscoelastic correspondence principle is used to convert the static elastic solutions to their complex steady state viscoelastic forms simply by replacing static elastic moduli of the matrix and the fibers by their complex viscoelastic moduli.To formulate accurate micromechanical predictions for comparison and validation by experimental measurements, appropriate values for the five independent elastic constants of the reinforcing carbon fibres in the experimental materials are required. To obtain them, we have used the ultrasonic immersion method (UIM) and an inverse modelling scheme as previously described by Smith. The UIM allows the full stiffness tensor to be determined for both the carbon fibre composite and the epoxy resin matrix at a frequency of 2.25 MHz. The validated Hashin–Rosen composite cylinders micromechanical model was then used to determine the best fit elastic constants of the carbon fibres. Once these were determined, the ‘viscoelastic properties’ of both the pure epoxy matrix and the carbon fibre composite were studied using low frequency measurements (1 Hz). The results showed that for the two viscoelastic constants that can be routinely measured experimentally, namely the in-plane longitudinal and transverse Young's moduli, these are very well predicted by the same micromechanical model. Most importantly, following this validation, the micromechanical model can then easily provide all of the five independent viscoelastic composite stiffness constants. These values are critical for accurate vibration damping and noise cutting design of advanced engineering composite parts exposed to oscillatory loading such as aircraft wings and tails or wind turbine blades.

PtCo Nanoparticles Supported on Carbon for Hydrolysis of Ammonia Borane

Ammonia borane received extensive attention due to its hydrogen content as high as 19.6%. In present article we prepared the Pt-Co/C catalyst via ultrasonic immersion method and in situ reduction method. The catalyst was characterized by measuring the specific area. The influence of the catalyst on the properties of the hydrolysis of ammonia borane was tested, and the catalytic activity of the catalyst in cycle use was verified. Results shows that the catalytic activity of Pt0.5Co0.5/C is the highest, and the maximum hydrogen generation rate is 7229.613 mL/ (g ·min). It was verified that it remained good catalytic activity after cycle use for more than 10 times.

Visible-light driven generation of reactive radicals over BiFeO3/TiO2 nanotube array: experimental evidence and energetic mechanism

BiFeO3-based materials have attracted broad interests due to their multiferric and photoactive properties, but there remains some controversial uncertainty about the electronic structures of various nanoparticles of BiFeO3. In this work, BiFeO3 nanoparticles smaller than 100 nm have grown into TiO2 nanotube array by an ultrasonic-immersion method. Some evidences on the energy band position of BiFeO3 nanoparticles in BiFeO3/TiO2 nanotube array were from the visible-light driven photo responses. Positive surface photovoltage polarity of the composite is the same as that of the pure TiO2 nanotube array, which reveals the photo-induced electron transfer from BiFeO3 nanoparticles to TiO2 nanotubes. Furthermore, both ·OH and ·O2 − radicals could be detected by the electron paramagnetic resonance (EPR) spin-trapping method. According to the EPR result, the valence band edge of BiFeO3 nanoparticles could be deduced as more positive than the potential at which ·OH radical could be generated. A scheme on the energy band alignment and photo-induced charges transfer processes is then proposed based on the observed visible-light photo activity of BiFeO3/TiO2 nanotube array.

Nondestructive Evaluation of Spot Weld in Stainless Steel Using Ultrasonic Immersion Method

This paper describes quantitative evaluation of the nugget size and shape of resistance spot welds on stainless steel using ultrasonic pulse-echo amplitude. Here an empirical formula has been derived for predicting spot weld nugget diameter for sample having different thickness. The reliability as well as the accuracy of the empirical equation has been verified by comparing the calculated results based on ultrasonic response with the results obtained by X-ray (Radiography) and destructive testing.

BiFeO3/TiO2 Nanotube Arrays Composite Electrode: Construction, Characterization, and Enhanced Photoelectrochemical Properties

This work aims at the exploration of nanostructured ferroelectric-material-modified semiconductor electrodes for enhanced photo-induced activity. A well-aligned BiFeO3/TiO2-nanotubes (NTs) array with visible-light activity was successfully synthesized on a titanium sheet by combining anodization and an ultrasonic-immersion method followed by annealing. The structural and optical properties of the TiO2-NTs and the composite BiFeO3/TiO2-NTs were comparatively characterized. The composite BiFeO3/TiO2-NTs grown on a Ti sheet and used as an electrode exhibited a stronger absorption in the visible region and a much higher photoconversion efficiency than the pure TiO2-NTs/Ti electrode. Electrochemical impedance investigation attested to a significant improvement of the interfacial electron-transfer kinetics with enhanced separation of electron-hole pairs. The as-prepared composite electrode showed a high efficiency for photoelectrocatalytic degradation towards rhodamine B under visible-light irradiation (λ > 400 nm). The enhanced photoelectrocatalytic activity of the composite electrode could be attributed to the synergistic effect between the lowered electron-hole recombination rate by the applied bias and the wider spectral response promoted by the BiFeO3 component.

Comparison between Contact and Immersion Method in Ultrasonic Stress Measurement of Welded Stainless Steel Plates

Abstract This study presents a comparison between contact and immersion ultrasonic method to measure welding residual stress of austenitic stainless steel plates (AISI 304L). Longitudinal critically refracted (LCR) waves are employed to measure the residual stresses. By using contact and immersion transducers, a 3D distribution of longitudinal residual stress for the entire of the welded plate is presented. A finite-element model of welding process, which is validated by the hole-drilling method, is used to verify the ultrasonic results. The results show no considerable differences between using contact or immersion transducers in ultrasonic stress measurement of stainless steel plates; however, some practical considerations are mentioned.

Influence of test method used to evaluate resistance of C‐Mn steel to hydrogen induced cracking

AbstractThe presented paper deals with a comparison of test methods for evaluating the resistance of API grade X65 steel to hydrogen induced cracking (HIC). It concerned particularly the ultrasonic immersion method using an AGFA non‐destructive testing device by Krautkrämer and metallographic evaluation of the results of ultrasonic tests according to the directive NACE TM 0284. Comparison of test methods was made on the basis of established parameters of cracks, i. e. crack length ratio (CLR), crack thickness ratio (CTR) and crack sensitivity ratio (CSR). The determination of parameters in case of ultrasonic examination was performed using the pulse reflection method. Metallographic evaluations were performed always at hundred‐fold magnification on a light microscope ZEISS NEOPHOT 32. The obtained results showed that all the test methods used had very small differences between the investigated parameters.

Comparison between contact and immersion ultrasonic method to evaluate welding residual stresses of dissimilar joints

This paper presents a comparison of contact and immersion waves used to measure residual stresses. The residual stresses are produced due to a dissimilar welding of stainless steel (304) to carbon steel (A106). Longitudinal critically refracted (LCR) wave propagated by 2MHz contact and immersion ultrasonic transducers is employed to measure the residual stresses. A Finite Element (FE) model of welding process, which is validated by hole-drilling method, is used to verify the ultrasonic results while an acceptable agreement is achieved. The best agreement is observed in the parent material while the maximum difference is measured in the heat affected zone (HAZ). The results show no considerable difference between using contact and immersion transducers in ultrasonic stress measurement of dissimilar joints.

Study in Ultrasonic Flaw Detection for Small-Diameter Steel Pipe with Thick Wall

In this paper, the detective method, using ultrasonic immersion method with focusing probe, was presented. Based on analyzing and solving the reflection and refraction coefficients of ultrasonic waves at the interface between two different media, the transmission paths were chosen, which were based on selected thick steel pipe (t/D ≥ 0.3), this is so-called converted shear wave testing method of ultrasonic detection of flaws. Moreover, the theory of flaw detection of the pipes was studied. The sound pressure of echo of flaws detected by converted shear wave was deduced, as was verified by independently developed automatic ultrasonic flaw detection equipment for the pipe. Experimental results revealed that it was feasible to detect the flaw by converted shear wave testing method. Echo was clear, the SNR was perfect, and the sensitivity was 4.3dB higher than one detected by refracted transverse wave. Detected-flaw speed was improved resulting in the test time dramatically shortening, which was especially beneficial for overall-length and all-round detection.

Noise Reduction Using Wavelet Transform in Ultrasonic Flaw Detection of Small-Diameter Steel Pipe with Thick Wall

In order to ensure that small diameter steel pipes with thick wall have high intensity and high quality, ultrasonic immersion method with focusing probe was used to detect the flaw of the small-diameter steel pipes with thick wall. In practice, the echoes are often corrupted with external noise or internal noise, therefore, it is necessary to reduce the noise and to enhance the SNR of ultrasonic signals. A technique for improving the SNR of ultrasonic signals using wavelet transform is presented. In this method, WT, consider as one band-pass filter, is used to remove the noises. The performance of this technique has been verified by experimental, which is done by using a series of flaw ultrasonic echoes obtained from a specimen of the small-diameter steel pipes with thick wall. In particular we have found the processing of the ultrasonic signals using wavelet transform extremely useful for noise reduction. After processing, the SNR of ultrasonic signals are enhanced substantially. All experimental results show that this technique is effective for removing the white noise from the ultrasonic signals.

Sonochemical growth of lanthanum conversion films using ultrasonic immersion method for performance improvement of zinc electrodes

The growth of lanthanum conversion coatings on the zinc powder modified by ultrasonic immersion is deeply investigated by Auger electron spectroscopy, X-ray photoelectron spectroscopy, spectrophotometrical and other characterization techniques. The conversion kinetics of La element and the growth mechanism of lanthanum conversion layers are also reported and proposed. The influence of the lanthanum conversion coatings on the discharge properties and cycle behaviors of zinc electrodes is evaluated through charge–discharge measurements and cycle voltammetry. It is found that La 2O 3 and ZnO compose the lanthanum conversion films and trace content of La element in modified zinc powder can be controlled by varying the ultrasonic power. Furthermore, the superior performance of zinc electrode using the zinc powder coated with lanthanum conversion films is clearly established by low capacity loss and high cycle stability. The great improvement over the electrochemical properties of zinc electrodes should be ascribed to the physical shielding effect of lanthanum conversion layers.

Evaluation of Modulus of Elasticity, Mineral Composition and Bone Mineral Density of Trabecular Bone L3- Vertebrae Samples Extracted From Mexican Men

ABSTRACTExtracted samples of L3 vertebrae, the healthy, osteopenic and osteoporotic from Mexican men, were fixed to carry out measurements of the modulus of elasticity (ME) and the minerals content, on the trabecular zone to study their behavior as a function of age.To determine the ME the immersion ultrasonic method (IUM) was used, X-ray dispersion was applied to know the chemical element concentration (Ca++, Na++, P, and Mg++) and computerized axial tomography (CAT) to obtain bone mineral density (BMD).The samples were organized in four groups by decade. The samples in the range of 30-39 years revealed: a normal BMD and a concentration [% w/w] between pairs of Ca++/P, Ca++/Mg++, P/Mg++ and Mg++/ Na ++ with correlation positive due to the strong dependence between them.The average ME results were: 2.79±0.326, 2.68±0.45, 2.66±0.43 and 2.70±0.397 [GPa] for each decade respectively. The ME profiles show a nonlinear behavior as a function of age, indicating a minimum value in the third decade, similar behavior is observed in the Ca++. An exponential behavior between ME and T-score was obtained. The plotted Ca++ and ME as a function of area showed a homogeneous distribution for the first and a non homogeneous for the second.