Ultrasonic Frequency Research Articles

Frequency shifting of transmitted ultrasound in thick composites containing fiber wrinkles and its application in non-destructive evaluation

Thick composite structures are prone to defects such as fiber wrinkles and voids during manufacturing. It is challenging to accurately evaluate the forming quality of the structures using conventional ultrasonic inspection, due to the coupling effects between time-frequency features of ultrasound and mixed-type defects. Propagation behaviors of through-thickness transmitted ultrasound in thick composites with fiber wrinkles, voids and no defects were comparatively investigated by both simulation and experiment in this study. Influence of out-of-plane fiber wrinkles on the ultrasonic frequency shifting was studied by comparing the time-frequency characteristics of simulated ultrasonic signals after propagating different distances in the intact and wavy composites. Changes of transmission coefficients of converted transverse waves caused by fiber wrinkles were concluded be the reason for the appearance of high-frequency components above the excitation frequency in the transmitted ultrasound signal. Thereby ultrasonic defect inspection indices based on the phenomenon of ultrasonic frequency shifting were defined. Effects of interaction angles between ultrasonic propagation direction and fibers on the defined inspection indices was further investigated quantitatively. The thick composites with diverse defects were successfully diagnosed using the ultrasound frequency shifting and energy dissipation behaviors.

A hybrid RSM-GA-PSO approach on optimization of process intensification of linseed biodiesel synthesis using an ultrasonic reactor: Enhancing biodiesel properties and engine characteristics with ternary fuel blends

The depletion of fossil fuels necessitates the development of sustainable and energy-efficient techniques for biodiesel production. In recent years, cavitation reactors have emerged as a viable alternative to conventional biodiesel synthesis methods due to their superior conversion rates and shorter processing times. These reactors possess a high surface-to-volume ratio and facilitate efficient heat and mass transfer. This study aims to optimize the production of biodiesel from linseed oil using a novel ultrasonic cavitation reactor through a hybrid approach. In order to achieve this, an L50 orthogonal array with five factors and three levels was developed using a Box-Behnken design based on response surface methodology (RSM). These factors included the molar ratio (4:1, 6:1, and 8:1), ultrasonic power (100, 125, and 150 W), temperature (25, 35, and 45 °C), time (3, 6, and 9 min), and ultrasonic frequency (25, 30, and 35 kHz). The parameters were optimized using RSM-based desirability, genetic algorithm (GA), and particle swarm optimization (PSO) approaches. The results indicated that the RSM-based optimization approach outperformed the other methods. The optimal combination of parameters obtained through RSM consisted of molar ratio of 6.58:1, ultrasonic power of 133.65 W, temperature of 37.44 °C, time of 7.71 min, and pulse frequency of 26.29 kHz. This combination resulted in a biodiesel yield of 95.25%. Furthermore, this study explored the impact of different linseed oil methyl ester, octanol, and diesel blends (B10, B20, B30, B10 (O-10), and B20 (O-10)) on engine performance and emission characteristics. The B20 (O-10) blend exhibited significant potential for simultaneously reducing emissions and enhancing engine performance. When used as engine fuel, the B20 (O-10) blend increased brake thermal efficiency (BTE) by 0.848%, decreased brake specific fuel consumption (BSFC) by 0.607%, and decreased CO, HC, and NOx emissions by 18.75%, 6.55%, and 0.72%, respectively, compared to pure diesel at rated power.

Thorough ultrasonic rheology of soft, visco-elastic materials: Example of crosslinked Polyurethane elastomer

We present a thorough procedure for measuring the rheological properties of soft, highly attenuating, visco-elastic materials at ultrasonic frequencies. The material chosen for this illustration is a crosslinked Polyurethane (PU) elastomer (Sika UR3440 type), which is widely used in the field of underwater acoustics. We determine its complex longitudinal modulus M and shear modulus G as function of frequency in the range 1–5 MHz and of temperature in the range 5–40 °C. M is determined from the measurement of the transmission of longitudinal, plane waves by a slab of PU immersed in water. G is determined by contact measurements from the transmission and reflection of transverse, plane waves by a slab of PU. This determination of G for such a soft and viscous material as PU is made possible by the use of thin slabs and the implementation of an original signal analysis. M, G and bulk modulus K are found to obey the time–temperature superposition principle and to be accurately described by a fractional derivative rheological model. This allows us to propose analytic formulas for the frequency and temperature dependence of M, G and K valid above PU glass transition temperature.

Ultrasonic-assisted supercritical fluid separation removing plasticizers from ganoderma lucidum spores’ oil

Ultrasonic-assisted supercritical fluid separation (USFS) was firstly applied to regulate solubility and remove plasticizers from ganoderma lucidum spores’ oil to improve product safety. Separation efficiency was related with four variables, including temperature, pressure and ultrasonic power. The QD-T6A ultrasonic generator probe, which provided for the study with adjustable ultrasonic power 0 W to 800 W and the ultrasonic frequency was 40 kHz, was fixed at the entrance of the primary separation kettle. The optimal separation conditions were determined to be temperature as 15.0 °C, pressure as 18.0 MPa, and ultrasonic power as 360 W of ultrasonic power on the basis of response surface methodology (RSM). Experimental Di-n-butylphthalate (DBP) and Diethyl phthalate (DEP) content were 0.09 mg and 0.04 mg, respectively, which were below the limits for plasticizers. Meanwhile, the total triterpene and ganoderic acid A contents were 6.89 g and 1.10 g, respectively, comparable to conventional supercritical fluid extraction. The experiments with USFS at different power intensities revealed that ultrasonic at a power intensity of 36 W/L and the power density of 0.20 W/cm2 could resolve the separation contradiction between ganoderma lucidum spores’ oil and plasticizers. This study revealed that USFS could be an innovation in the field of ultrasonic separation, with numerous potentials uses in pharmaceutical manufacturing.

Numerical Assessment of Combustion Behavior and Emission Formations in an Ultrasonic-Assisted Ignition Engine.

By effective utilization of the dynamic mesh and coordinate transformation techniques, an ultrasonic horn is physically integrated in the chamber of an internal combustion engine. The consequences of multiple ultrasonic-fed strategies on the flow field, combustion process, and emission formation under the same working conditions are studied by numerical simulation. Based precisely on the bench test data, GT-Power and CONVERGE set up the original engine one-dimension (1d) and three-dimension (3d) simulation models. The chamber pressure and heat release rate of the 1d and 3d models under a full load condition of 3000 r·min-1 were validated, and the maximum relative error is less than 5%, proving the accuracy of the model. By reforming the 3d numerical model, ultrasonics is added to the gasoline engine's combustion chamber. Six different ultrasonic-fed schemes with 20 kHz amplitude of 30-300 μm are typically selected for in-depth research. The larger the amplitude, the stronger the turbulent kinetic energy (TKE), and the maximum TKE exceeds 46.6% at the ignition time. Stronger TKE can energetically encourage the generation of OH, O, and H radicals and improve the combustion reaction rate, and the peak pressure (PMAX) is increased by 1.9 MPa compared with scheme No. However, NOX and HC emissions gradually increase, reaching a maximum of 32.4 and 43.8%, respectively, while CO and soot emissions decrease, reaching a maximum of 11.4 and 11%, respectively. Four groups of ultrasonic-fed schemes with an amplitude of 100 μm and frequency of 20-50 kHz are scientifically studied. The findings indicated that the TKE level steadily increases as the frequency increases and the in-cylinder TKE increases by 16.4% at ignition time. The increase in ultrasonic frequency can promote the generation of active free radicals and meaningfully improve the combustion reaction rate to a certain extent. The PMAX can be increased up to 1 MPa compared with scheme No. At the same time, the NOX, HC, and soot also increased considerably, reaching 31.8, 17.9, and 21.9%, respectively. The CO showed a downward trend but gradually slowed, with a maximum decline of 6.5% at 20 kHz. The above simulation analysis is based on the full load condition of 3000 r·min-1, sufficiently proving that ultrasonics has a regulation effect on emissions and can achieve specific emissions through later optimization.

The Influences of Ultrasonic Vibrations on Laser Cladding Ni60/WC-TiO2+La2O3 Composite Coating.

The optimal process parameters of ultrasonic-assisted processing were studied to further improve the molding quality and mechanical properties of Ni60/WC-TiO2+La2O3 composite coating. A single-factor experiment was used to explore the influences of ultrasonic vibration frequencies on Ni60/WC-TiO2+La2O3 composite coating. The microstructure, elemental composition, phase composition, hardness, and wear resistance of the coating were studied using scanning electron microscopy (SEM), an X-ray diffractometer (XRD), an energy spectrometer, a microhardness meter, a friction and wear tester, and other equipment. Ultrasonic vibrations significantly improved the problems of pores in the coating, and the porosity was reduced from 0.13 to 0.014%. When the vibration frequency was 32 kHz in the experiment, the aspect ratio of the coating was optimized from 2.06 to 2.48, the dilution rate increased from 5.60 to 5.79%, the hardness increased from 960.25 to 988.45 HZ1.0, and the friction coefficient was reduced from 0.34 to 0.27. The coating performance was significantly improved, and the research results provide a reference for preparing excellent Ni60/WC-TiC+La2O3 composite coating.

Developing a novel ultrasonic atomization-based cutting fluid spray system and evaluating its performance during milling processes

Cutting fluid has been widespread in the metal cutting industry due to its cooling and lubrication properties. However, the excessive application of cutting fluids can lead to significant environmental issues and raise machining costs. Recently, the ultrasonic atomization-based cutting fluid (UACF) spray using minimum quantity has shown superior cooling and lubrication performance during machining processes, while the precise management of UACF spray and its influence on machining performance requires further comprehension. In this case, this paper developed a novel ultrasonic atomization-based cutting fluid (UACF) spray system, featuring a specialized nozzle unit that included an internal droplet nozzle and an external gas nozzle. Subsequently, the dynamics of droplet impingement on a rotated surface were analyzed, and the spray characteristic parameters were investigated. Then, comparative milling experiments were conducted under different cooling conditions, including dry cutting, flood cooling, high-pressure air cooling, and UACF. The influence of these cooling conditions on machining performance was investigated, in terms of cutting force, temperature, surface roughness, and chip morphology. The results obtained indicate that the critical velocity of droplet spreading was dependent on the cutting fluid properties, ultrasonic frequency, and velocity of the rotated surface. The droplets generated by ultrasonic atomization follow a Gaussian distribution. Flood cooling and UACF exhibit similar effects in reducing cutting force, temperature, and surface roughness due to the efficient penetration of liquid film into tool-workpiece interfaces. Additionally, UACF can significantly reduce the consumption of cutting fluid by up to 98.5 % compared to flood cooling. The effective cooling and lubrication in UACF can improve the surface quality and suppress machining vibration. Moreover, the appropriate droplet velocity can ensure the formation of a thin film on the tool surface, thereby enhancing cooling and lubrication performance in the UACF process.

The image-based ultrasonic cell shaking test.

Mechanical signals play a vital role in cell biology and is a vast area of research. Thus, there is motivation to understand cell deformation and mechanobiological responses. However, the ability to controllably deform cells in the ultrasonic regime and test their response is a noted challenge throughout the literature. Quantifying and eliciting an appropriate stimulus has proven to be difficult, resulting in methods that are either too aggressive or oversimplified. Furthermore, the ability to gain a real-time insight into cell deformation and link this with the biological response is yet to be achieved. One application of this understanding is in ultrasonic surgical cutting, which is a promising alternative to traditional methods, but with little understanding of its effect on cells. Here we present the image based ultrasonic cell shaking test, a novel method that enables controllable loading of cells and quantification of their response to ultrasonic vibrations. Practically, this involves seeding cells on a substrate that resonates at ultrasonic frequencies and transfers the deformation to the cells. This is then incorporated into microscopic imaging techniques to obtain high-speed images of ultrasonic cell deformation that can be analysed using digital image correlation techniques. Cells can then be extracted after excitation to undergo analysis to understand the biological response to the deformation. This method could aid in understanding the effects of ultrasonic stimulation on cells and how activated mechanobiological pathways result in physical and biochemical responses.

Sound production in sea turtle nests and hatchlings (Eretmochelys imbricata and Caretta caretta) in Northeast Brazil

ABSTRACT Sea turtles have been considered the least vocal of living reptiles, but recent studies are changing this perception. Here, we aimed to investigate the acoustics of hatchlings of, Eretmochelys imbricata and Caretta caretta in Northeast Brazil, to describe their acoustic signals and compare sound structure within and between species. We monitored 13 km in Ipojuca, southern coast of Pernambuco State. We recorded five nests of each species and the hatchlings’ walk to the sea in 2020/2021. We recorded 12 sonotypes in C. caretta and 5 in E. imbricata, increasing the number of described signals. Nevertheless, not all sonotypes were produced by all or in the different developmental stages. Some of the sounds for both species reached ultrasonic frequencies. The sound structure varied between C. caretta nests, suggesting a potential vocal signature, but the sound structure had no variation between E. imbricata nests. The sound structure varied between species. Despite their reputation for being silent, this study shows a diverse acoustic repertoire in the target species, further supporting speculations of acoustic signals mediating the potential synchronisation of hatchlings’ departure to the sea. Our signal descriptions could be used for future passive acoustic monitoring of the target species. Future studies should focus on understanding the functionality of acoustic signals in the different life stages.

Acoustic Levitation-Assisted Contactless Printing of Microdroplets for Biomedical Applications

Abstract The cell is a microcapsule system wherein biological materials are encapsulated by a thin membrane, which provides valuable information on the metabolism, morphology, development, and signal transduction pathways of the studied cell. The cell-inspired microdroplet has the characteristics of efficient nanoscale substance transportation, self-organization, and morphological adaptation. However, it is extremely difficult to manufacture such systems. Mostly vesicles such as liposomes, polymersomes, and microcapsules are first produced by a high-pressure homogenizer and microfluidizer as an emulsion and then encapsulated microcapsules by the drop or emulsion method. Currently, acoustic levitation opens entirely new possibilities for creating bioinspired microdroplets because of its ability to suspend tiny droplets in an antigravity and noncontact manner. Herein, we propose contactless printing of single-core or multi-core cell-inspired microdroplets via acoustic levitation. First, the oscillation mode and microscopic morphology of the droplets under different ultrasonic vibration frequencies are shown by simulation, and the curing characteristics of the shell structure under different ultraviolet illumination conditions are quantitatively measured. The feasibility of manufacturing multi-core microdroplets and manufacturing submillimeter-scale particles based on oil trapping is extensively studied. To explore the morphological adaptability of microdroplets, ferromagnetic Fe3O4 nanoparticles are used to give magnetic-responsive properties to cells, and the microscopic deformation and motion in microfluidic channels under the magnetic field are characterized. Finally, the proposed printing method proves the versatility of in-space contactless printing of complex 3D beam structures and provides a powerful platform for developing biomedical devices and microrobots and studying morphogenesis and synthetic biological systems.

Ultrasound-assisted Extraction Method for Element Determination in Lignocellulosic Biomass

In this work, a sample preparation method based on ultrasound-assisted extraction (UAE) for the determination of Al, Ba, Ca, Fe, K, Mg, Mn, Na, P, Sr, and Zn in lignocellulosic biomasses (sugarcane bagasse, eucalyptus wood residues, and pine wood residues) was evaluated. Reference values were achieved following the EN ISO 16967, which was based on a microwave-assisted wet digestion sample preparation method for further element determination by inductively coupled plasma optical emission spectrometry (ICP OES). The optimizations for the proposed UAE method were performed using 250 mg of sugarcane bagasse sample, where the ultrasonic bath frequency (25, 35, 37, 45, 80, and 130 kHz), and acoustic amplitude (50, 70 and 100%) were evaluated. After selecting the most efficient extractant solvent (20 mL of 1 mol L-1 of H2O2, HNO3, H2SO4, H2O, or CH2O2), the extraction temperature (20, 50, or 70 ºC) and time (15, 30, or 40 min) were evaluated. The most efficient extraction condition using the UAE method employed 45 kHz (70% amplitude), 20 mL of 1 mol L-1 of H2SO4, and 50 °C for 30 min. The optimized UAE was used for extraction and subsequent element determination in residues of pine wood and eucalyptus wood. Although poor recoveries were observed for Al, Ba, and Fe (lower than 75%), the results for Ca, K, Mg, Mn, Na, P, Sr, and Zn were in agreement (Student t-test, 95% confidence level) with those obtained by EN ISO 16967. Therefore, the proposed UAE method proved to be efficient for the determination of most of the evaluated elements in lignocellulosic biomasses with different matrix complexity, employing milder extraction conditions and diluted reagents.

Experimental Study on Ultrasonic Cavitation Intensity Based on Fluorescence Analysis

The Ultrasonic cavitation effect has been widely used in mechanical engineering, chemical engineering, biomedicine, and many other fields. The quantitative characterization of ultrasonic cavitation intensity has always been a difficulty. Based on this, a fluorescence analysis method has been adopted to explore ultrasonic cavitation intensity in this paper. In the experiment of fluorescence intensity measurement, terephthalic acid (TA) was used as the fluorescent probe, ultrasonic power, ultrasonic frequency, and irradiation time were independent variables, and fluorescence intensity and fluorescence peak area were used as experimental results. The collapse of cavitation bubble will cause molecular bond breakage and release ·OH, and the non-fluorescent substance TA will form the strong fluorescent substance TAOH with ·OH. The spectra of the treated samples were measured by a F-7000 fluorescence spectrophotometer. The results showed that the fluorescence intensity and fluorescence peak area increased rapidly after ultrasonic cavitation treatment, and then increased slowly with the increase of ultrasonic power, which gradually increased with the increase of irradiation time. They first decreased and then increased with the increase of ultrasonic frequency from 20 kHz to 40 kHz. The irradiation time was the most influential factor, and the cavitation intensity of low frequency was higher overall. The fluorescence intensity and fluorescence peak area of the samples increased by 2–20 times after ultrasonic treatment, which could increase from 69 and 5238 to 1387 and 95451, respectively. After the irradiation time exceeded 25 min, the growth rate of fluorescence intensity slowed down, which was caused by the decrease of gas content and TA concentration in the solution. The study quantitatively characterized the cavitation intensity, reflecting the advantages of fluorescence analysis, and provided a basis for the further study of ultrasonic cavitation.

Surface/subsurface formation mechanism of tungsten during ultrasonic elliptical vibration cutting

The ultrasonic elliptical vibration cutting (UEVC) has been proved to be a valid method to improve surface quality and reduce subsurface damage of tungsten. However, it is still a huge challenge to elucidate the surface/subsurface formation mechanism of tungsten during UEVC. Hence, molecular dynamics simulations were employed to reveal the formation mechanism of surface/subsurface during UEVC of tungsten from the atomic level, and the effects of ultrasonic amplitude and frequency on the surface/subsurface formation were explored. The results showed that compared with general cutting (GC), the improved surface quality was attributed to the smaller actual cutting depth and more amorphous tungsten in chips caused by cyclic loading-unloading during UEVC. Moreover, the reversing friction direction facilitated the formation of surface chips during UEVC as well. The thermal-activated dislocations caused by high transient cutting temperature could result in the wide distribution of subsurface dislocations, and the dislocations were usually expanded by the way of crystal plane slip to suppress generation of long slip plane, which could reduce the subsurface damage of tungsten during UEVC. In comparison with ultrasonic amplitude in cutting depth direction, elevated ultrasonic amplitude in cutting speed direction or ultrasonic frequency could reduce depth of subsurface damage layer, surface roughness, and dislocation density, which derived from the small transient cutting force and stress as well as high strain rate. This study provides a new insight into the surface/subsurface formation mechanism of tungsten during UEVC, which can offer a theoretical basis on the selection of ultrasonic parameters for achieving high surface/subsurface quality for tungsten and other materials machined by UEVC.

Assessing the recovery of dodecanol from alkyl polyglycosides (APG) using solvent extraction

Dodecanol, known as lauryl alcohol, is commonly used in the production of alkylpolyglycosides (APG) by reacting dextrose with an excess of dodecanol in the presence of an acid catalyst. After the reaction is completed, the challenging part is the purification step, to separate unreacted dodecanol from APG to ensure the final product meets an industrial specification requiring less than 5% of the dodecanol residue. Current separation methods i.e., evaporation and distillation, require high energy and could deteriorate the product quality if it is not operated carefully. In this research, the extraction process was evaluated to separate the unreacted dodecanol without compromising the quality of the final product. The study investigates the effect of the solvent matrix, temperature and stirring speed for the extraction of dodecanol using a mixture of water with ethanol, propanol or toluene as a solvent matrix. The composition ratio of sample: solvent: water was fixed at 10:10:10 (in mL). The extraction temperature was manipulated between 60 °C and 80 °C and stirring speed was at 5 and 7 rpm. In addition, the extraction was also subjected to the ultrasonic frequency set at 9 Hz for 30 min and using toluene as a matrix solvent. Results show that higher extraction yield was obtained at low temperatures and stirring speed. By using a solvent matrix-toluene leads to the highest extraction yield of 15.02 w/w%. Applying ultrasonic during the extraction process increased the extraction yield to 32 w/w%, indicating that the ultrasonic has intensified the extraction process. In conclusion, the excess of dodecanol in the APG sample could be separated via an extraction process. This potential method allows an alternative separation technique at a low investment cost, energy saving and eventually meeting the APG’s product specifications requirement.[copyright information to be updated in production process]

Removal of pesticides from fresh-cut Chinese cabbage (Brassica rapa var. chinensis L.) by sequential multi-frequency ultrasound cleaning treatments

Pesticides may remain on the surface of fresh produce due to inappropriate and inadequate cleaning. In view of the public health significance of pesticide residues in fresh produce and the long-term effects of low dose exposure of these pesticides, decontamination procedures are needed for ready-to-eat foods, especially vegetables. Ultrasound cleaning is considered to be an effective environmentally-friendly decontamination process which is unique in its ability to remove pesticides compared to other conventional methods. The reduction of dimethoate and diazinon residues from fresh Chinese cabbage by sequential multi-frequency ultrasound cleaning treatments was investigated in this study to ascertain the levels of reduction after cleaning. The ultrasonic treatment has higher efficiency on the removal of these organophosphorus pesticides compared to ordinary water cleaning. The removal rates of ultrasonic cleaning treatments for dimethoate and diazinon residues were in the range of 20.10–72.42% and 29.60–77.37% compared to the ordinary water cleaning with 13.24–19.89% and 17.32–24.16% respectively. In addition, quality parameters for the leaves treated were also assessed. The physical impairment and vitamin C loss increased with the increase in ultrasonic frequency combination and cleaning time. Application of triple frequency ultrasound and extended washing time resulted in high dimethoate (>70%) and diazinon reduction (>75%) alongside slight perceptible darkening in colour of the leaves. The use of multi-frequency ultrasound in sequential mode is an effective technique for the removal of pesticide residues from leafy vegetables. However, ultrasonic operating conditions should be considered to maintain product quality.

Effects of ultrasound on the removal of emulsion plugging in oil reservoirs

The generation of water-in-crude oil emulsions in a reservoir can cause formation damage due to droplet trapping at pore spaces. The removal of the damage is anticipated to be inexpensive and eco-friendly when done with ultrasound as opposed to chemical demulsifiers. The influence of ultrasonic power and frequencies on the removal process, however, is not well understood. Additionally, the process's underlying mechanism is largely speculated. In this study, the effect of ultrasound on the removal of emulsion plugging in oil reservoirs was investigated using a glass micromodel. Emulsion blockage during oil production was replicated in the micromodel and subjected to different ultrasonic frequencies (20 and 40 kHz) and powers (100–1000 watt). The experiments demonstrate that when ultrasonic power and frequency increase from 100 to 1000 watt and 20–40 kHz, respectively, demulsification effectiveness decreases. Ultrasound at low frequency (20 kHz) and power (100 watt) proved to be the most efficient condition to dislodge trapped emulsions in the micromodel pores, facilitate droplet coalescence and increase fluid recovery. The percentage of recovered emulsions increased to 58 % when the micromodel was exposed to ultrasound (20 kHz, 100 watt), as opposed to 53.3 % in the case without ultrasound. This study provides insights into the microscopic behavior of emulsions under the influence of ultrasonic waves, allowing petroleum engineers to optimize ultrasound demulsification process.

Fatigue strength estimation of a CF/PEKK composite through self-heating temperature analysis using cyclic bending tests at 20 kHz

Very high cycle fatigue (VHCF) testing at conventional frequencies is highly time-consuming and unrealistic for large sample sizes. Though testing at ultrasonic frequencies can accelerate the testing, any undesirable thermal effect arising from testing at 20 kHz can cause significant heat generation in the specimens, increasing the likelihood of thermally induced failure. When mitigated, the temperature behavior during ultrasonic fatigue testing may conversely provide knowledge of the fatigue behavior of the composite. We study this hypothesis in this work by estimating the fatigue strength of a CF/PEKK composite through its temperature evolution during 3-point bending tests at 20 kHz with different cyclic load amplitudes. The fatigue strength of the composite was estimated using the temperature characteristics from an increasing cyclic amplitude test. This estimation was validated with four constant cyclic amplitude tests. Further, the estimation model was extended to different pulse–pause sequences by two constant cyclic amplitude tests. The results indicate a reliable and rapid method for fatigue life estimation as a material property. Finally, the criticality of the self-heating phenomenon during the non-stationary self-heating condition was evaluated.

A new method for ultrasonic fatigue component frequency modulation: From ultrasonic horn to uniaxial and multiaxial specimens

Ultrasonic fatigue specimens require rigorous design. The entire machine and specimen setup must vibrate in resonance at high frequencies, with the desired mode shapes that produce the intended stresses. The connection between parts must be considered too as they should allow for the desired mode shape to vibrate in free-free conditions. Most published research uses an analytical method that works only for uniaxial tension–compression or pure torsion specimens. This limits the range of experiments. In this paper, a semi-analytical formulation that can model more complex ultrasonic specimen geometries for a variety of stress states is proposed, namely multiaxial tension–torsion. Comparing numerical simulations with the analytical method show a good correlation between results. This work can help other researchers to design and conduct more varied and efficient ultrasonic fatigue experiments.

Ultra-wideband optical coherence elastography from acoustic to ultrasonic frequencies

Visualizing viscoelastic waves in materials and tissues through noninvasive imaging is valuable for analyzing their mechanical properties and detecting internal anomalies. However, traditional elastography techniques have been limited by a maximum wave frequency below 1-10 kHz, which hampers temporal and spatial resolution. Here, we introduce an optical coherence elastography technique that overcomes the limitation by extending the frequency range to MHz. Our system can measure the stiffness of hard materials including bones and extract viscoelastic shear moduli for polymers and hydrogels in conventionally inaccessible ranges between 100 Hz and 1 MHz. The dispersion of Rayleigh surface waves across the ultrawide band allowed us to profile depth-dependent shear modulus in cartilages ex vivo and human skin in vivo with sub-mm anatomical resolution. This technique holds immense potential as a noninvasive measurement tool for material sciences, tissue engineering, and medical diagnostics.

Ultra-low temperature sono-assisted CO2 stripping/ carbon-rich solvent regeneration using different ultrasonic frequencies

ABSTRACT Carbon dioxide emission from anthropogenic sources plays a major role in global warming and climate change. Conventional amine-based carbon capture is matured technology that has limitations on high-temperature use imposed by solvent degradation and solvent loss during CO2 stripping/regenerating solvent. The present experimental investigation involves the application of tank-type (bath-type) sonication for CO2 stripping from aqueous carbon-rich 30 wt% MEA solvent in a low temperature-controlled environment, using ultrasonic frequencies of 25 kHz (cavitation-dominant), 360 kHz (streaming-dominant), and 58/132 kHz dual-mode (combined phenomena). The results are analyzed to understand the effects of carbon loading, CO2 stripping efficiency, stripping rate, temperature profile, and energy demand. The stripping rate is higher in the low-temperature range of 6°C to 12°C for all the frequencies due to the sonication effect. In the mid setpoint range of 15°C to 30°C, the CO2 stripping rate is lower due to the combination of sonication and temperature effect, and when the temperatures increase from 40°C to 45°C, the stripping rate increases gradually due to additional temperature effect. A high cyclic capacity of 1.12 mol CO2/kg. was observed for 360 kHz frequency at 12°C. The lowest energy of 3.94 kJ/mol CO2 was achieved for 360 kHz at a setpoint of 12°C. Factors such as sonication frequency, CO2 loading (mol CO2/mol soln.), temperature, and nominal power of ultrasonics play an important role in determining the sensible energy required for CO2 stripping. Specifically, CO2 stripping at the low temperature set point of 6°C and 12°C is found to be promising in all frequencies, indicating that CO2 stripping is primarily promoted by sonication, rather than by temperature.