Compensation of system nonlinearity in the measurement of acoustic nonlinearity parameters.

The acoustic nonlinearity parameter is determined from the amplitudes of the fundamental and second harmonic component of the acoustic wave propagating through the material. However, the generally used through-transmission based measurements with PZT transducers contain high system nonlinearity, so that the received second harmonic component includes an extra component caused by the transducer, which significantly decrease the reliability of measurements. In this study, we proposed a novel method to reduce the system nonlinearity in the conventional through-transmission based measurements by adding a simple process in which the transmitting and receiving transducers are in direct contact without a specimen.

Full-range stress-strain curve estimation of aluminum alloys using machine learning-aided ultrasound.

Full-range stress-strain (SS) curves are crucial in understanding mechanical properties of a material such as the yield strength, ultimate tensile strength, and elongation. In this study, a full-range SS-curve was nondestructively estimated by applying machine learning to the ultrasonic amplitude-scan signal propagated through the material. The performance of the developed technique was validated using five-hundred aluminum alloy specimens with a wide spectrum of mechanical properties.

Microstructural Characterization of Additively Manufactured Metal Components Using Linear and Nonlinear Ultrasonic Techniques.

Metal additive manufacturing (AM) is an innovative manufacturing technology that uses a high-power laser for the layer-by-layer production of metal components. Despite many achievements in the field of AM, few studies have focused on the nondestructive characterization of microstructures, such as grain size and porosity. In this study, various microstructures of additively manufactured metal components were characterized non-destructively using linear/nonlinear ultrasonic techniques.

Compensation of a Second Harmonic Wave Included in an Incident Ultrasonic Wave for the Precise Measurement of the Acoustic Nonlinearity Parameter.

The incident second harmonic wave is a problematic issue for the precise measurement of the acoustic nonlinearity parameter. This paper proposes a compensation method to remove the effect of the incident second harmonic component in the measurement of the absolute acoustic nonlinearity parameter using the calibration method. For this, the second harmonic component detected by the receiving transducer is considered as the sum of the component due to material nonlinearity and the component included in the incident signal and a numerical calculation model is developed as a function of the propagation distance.

Rapid Molecular Diagnostic Sensor Based on Ball-Lensed Optical Fibers.

Given the fatal health conditions caused by emerging infectious pathogens, such as severe acute respiratory syndrome coronavirus 2, their rapid diagnosis is required for preventing secondary infections and guiding correct treatments. Although various molecular diagnostic methods based on nucleic acid amplification have been suggested as gold standards for identifying different species, these methods are not suitable for the rapid diagnosis of pathogens owing to their long result acquisition times and complexity. In this study, we developed a rapid bio-optical sensor that uses a ball-lensed optical fiber (BLOF) probe and an automatic analysis platform to precisely diagnose infectious pathogens.

Ultrasonic nonlinearity parameter in uniaxial stress condition.

The ultrasonic nonlinearity parameter derived for one-dimensional propagation of a longitudinal wave in an isotropic material has been considered useful in the evaluation of material degradation. To demonstrate this, many researchers have reported on the correlation with the yield strength obtained from a tensile test. However, there is an essential issue with this procedure - which is that the ultrasonic nonlinearity parameter is derived in a state where the lateral strain is restrained, whereas the tensile test to measure the yield strength is carried out under uniaxial stress conditions, where lateral deformation is free.

Dependence of nonlinear ultrasonic characteristic on second-phase precipitation in heat-treated Al 6061-T6 alloy.

It is well known that nonlinear ultrasound is sensitive to certain microstructural features in materials such as dislocations and precipitates. This paper investigates the dependence of the nonlinear ultrasonic characteristic on MgSi precipitation in heat-treated Al 6061-T6 alloy specimens. The specimens were heat-treated at a constant temperature of 220°C for different exposure times up to 6000min.

A method to estimate the absolute ultrasonic nonlinearity parameter from relative measurements.

The ultrasonic nonlinearity parameter (β) is determined from the particle displacement amplitudes of the fundamental and second-order harmonic components in an ultrasonic wave propagated through a material. This parameter is generally referred to as the absolute parameter. However, measuring the second harmonic component is especially difficult because its amplitude is usually much smaller than those of signals in typical ultrasonic measurements.

Nanotribological and wetting performance of hierarchical patterns.

Surface modification is a promising method to solve the tribological problems in microsystems. To modify the surface, we fabricated hierarchical patterns with different pitches of nano-scale features and different surface chemistries. Micro- and nano-patterns with similar geometrical configurations were also fabricated for comparison.

Relationship between second- and third-order acoustic nonlinear parameters in relative measurement.

The higher-order acoustic nonlinear parameters are considered effective damage indices in the field of nondestructive evaluation (NDE). They are defined by using the displacement amplitudes of the fundamental frequency and the harmonics, which are called the absolute nonlinear parameters. Generally, however, it is difficult to measure the very small displacement amplitudes of high-frequency harmonics.

In-line ultrasonic monitoring for sediments stuck on inner wall of a polyvinyl chloride pipe.

This research verified the applicability and effectiveness of the ultrasonic monitoring of sediments stuck on the inner wall of polyvinyl chloride (PVC) pipes. For identifying the transmittance of acoustic energy and the speed of sound in the PVC material, the pulse-echo ultrasonic testing was conducted for PVC sheets of different thicknesses. To simulate the solidified sediment, the hot melt adhesive (HMA) was covered on the inner wall of the PVC pipe in different heights.

In situ detection of laser-induced slip initiation on the silicon wafer surface.

We propose a real-time in situ method to detect slip initiation on the surface of silicon wafers during high-power laser beam irradiation. In this method, light is collected from the surface of a silicon wafer subjected to laser irradiation. When the slip is initiated, it strongly scatters the laser beam, allowing detection of the time of the slip initiation based on the resulting sudden increase in the scattering signal.

Imaging of contact acoustic nonlinearity using synthetic aperture technique.

The angle beam incidence and reflection technique for the evaluation of contact acoustic nonlinearity (CAN) at solid-solid contact interfaces (e.g., closed cracks) has recently been developed to overcome the disadvantage of accessing both the inner and outer surfaces of structures for attaching pulsing and receiving transducers in the through-transmission of normal incidence technique.

Harmonic generation of an obliquely incident ultrasonic wave in solid-solid contact interfaces.

The conventional acoustic nonlinear technique to evaluate the contact acoustic nonlinearity (CAN) at solid-solid contact interfaces (e.g., closed cracks), which uses the through-transmission of normally incident bulk waves, is limited in that access to both the inner and outer surfaces of structures for attaching pulsing and receiving transducers is difficult.

Estimation of clamping force in high-tension bolts through ultrasonic velocity measurement.

The estimation of clamping force has been regarded as the main issue in the maintenance of high-tension bolts. This paper proposes a method which uses the dependency of ultrasonic velocity on stress based on the nonlinear elastic effect. The variation of ultrasonic velocity in the range of actual stress acting in the bolt is very small so that the precise measurement of ultrasonic velocity is needed.

Application of the laser generated focused-Lamb wave for non-contact imaging of defects in plate.

The laser generation method of focused-Lamb wave is expected to have high defect-detection ability with advantages of non-contact testing. In this method, the laser beam is illuminated on the surface of the object through an arrayed-arc slit, and then the energy of the generated Lamb wave is concentrated on the focus point of arc. This focusing effect enables the concentration of higher wave intensity on the focus with better S/N ratio of signal, and has better spatial resolution compared to the conventional line arrayed method.

A nondestructive method for estimation of the fracture toughness of CrMoV rotor steels based on ultrasonic nonlinearity.

The objective of this paper is to develop a nondestructive method for estimating the fracture toughness (K(IC)) of CrMoV steels used as the rotor material of steam turbines in power plants. To achieve this objective, a number of CrMoV steel samples were heat-treated, and the fracture appearance transition temperature (FATT) was determined as a function of aging time. Nonlinear ultrasonics was employed as the theoretical basis to explain the harmonic generation in a damaged material, and the nonlinearity parameter of the second harmonic wave was the experimental measure used to be correlated to the fracture toughness of the rotor steel.