In the search for techniques to distinguish between merely good and excellent bond conditions, linear reflection based methods are simple to apply, but their sensitivity decreases rapidly with increasing bond quality. As an alternative, this research reports on the experimental validation of analytical and computational models of interface properties using non-collinear shear wave mixing. The interface between two solids in dry contact under varying contact pressures serves as a model for diffusion bonds with different degrees of imperfection. Both nonlinear shear-shear wave mixing and linear reflection and transmission measurements are considered. The results show that under increasing load, the nonlinear interface interaction coefficients decrease more slowly in comparison to analogous linear coefficients, demonstrating the higher sensitivity of nonlinear coefficients to subtle interface imperfections in high quality bonds. This comparison is achieved by integrating approximate phenomenological models with the experimentally measured data. Overall, these findings demonstrate the utility of non-collinear shear wave mixing for localized nonlinear interface measurements, and highlight advantages over linear methods for interface characterization.

This Letter develops a single-sided non-collinear shear wave mixing technique for material characterization based on the phase-matching interface condition. Analytical modeling reveals that the interference between incident and reflected waves produces standing wave patterns whose interaction significantly enhances the mixed wave energy. Finite element simulations and experimental measurements demonstrate that the generated mixed longitudinal wave reaches its maximum amplitude when the mixing occurs at the traction-free surface. Additional simulations confirm the analytical prediction that the amplitude of the mixed longitudinal wave scales proportionally with the Murnaghan third-order elastic constant m.These findings confirm the feasibility of the proposed approach, highlighting its potential as a single-sided ultrasonic nondestructive evaluation technique to characterize the nonlinear elastic properties of a material.

It is well established in the scientific literature that a material's nonlinear response is much more sensitive to increasing dislocation density, microcrack nucleation, and other types of early material degradation than its linear response. The nonlinear elastic behavior of materials can be studied using various nonlinear ultrasonic techniques (NLU). However, they are all significantly more complex than their linear counterparts; therefore, they are often limited to a laboratory environment, and their field of application in industry is very narrow. In recent years, numerous publications have proposed new techniques based on the so-called Sideband Peak Count (SPC) method that utilizes relatively simple ultrasonic measurements to evaluate the degree of nonlinearity in materials. In contrast to conventional NLU NDE techniques, such as harmonic generation or wave mixing, SPC currently lacks a rigorous theoretical basis. To fill this gap, this paper presents computational results obtained under the assumption of classical quadratic nonlinearity using the COMSOL Multiphysics finite element software package. Parametric studies of four relevant variables - excitation level, material nonlinearity, localized nonlinearity caused by a defect, and linear scattering caused by a geometrical feature - were conducted. All the results of this numerical parametric study indicate that the SPC method and the SPC damage parameter named SPC-Index (SPC-I) offer limited sensitivity to changes in the level of classical acoustic nonlinearity at typical excitation levels used in ultrasonic NDE.

Previous research established a nonlinear stiffness model for imperfect interfaces and analyzed non-collinear wave mixing at such interfaces for two incident shear waves. This study extends those results to encompass five possible non-collinear wave mixing modalities involving longitudinal and shear vertical waves, considering both material and interfacial nonlinearities. By simultaneously applying the conditions for both bulk resonance and interface phase-matching, the two required incident wave angles are determined, allowing the mixing efficiency to be directly characterized by the frequency ratio. The analytical predictions for both types of nonlinearities are numerically validated using COMSOL finite element simulations. Quantitative comparisons across different wave mixing scenarios reveal the relative contributions of material and interface nonlinearity. These findings offer valuable insights and guidelines for designing and interpreting future experimental studies involving non-collinear ultrasonic wave mixing.

This article focuses on the fundamentals, measurement techniques, and applications of ultrasonic residual stress measurements.

This article focuses on electric residual stress (RS) characterization methods based on electrical conductivity (EC), Hall coefficient (HC), and thermoelectric power (TEP) measurements in electrically conductive materials. It also describes electric RS measurement techniques and applications.

Laser ultrasonic subsurface sensing has key advantages for non-destructive evaluation in nuclear applications. Three such applications are summarized here: Non-invasive monitoring of hot molten salt flow for nuclear reactor heat transfer, crack depth profiling in canisters for storage nuclear waste, and measuring internal pressure and wall thickness of nuclear fuel rods.

Our research group developed a novel nano-pitted (NP) TiO2 surface on grade 2 titanium that showed good mechanical, osteogenic, and antibacterial properties; however, it showed weak hydrophilicity. Our objective was to develop a surface treatment method to enhance the hydrophilicity of the NP TiO2 surface without the destruction of the nano-topography. The effects of dilute and concentrated orthophosphoric (H3PO4) and nitric acids were investigated on wettability using contact angle measurement. Optical profilometry and atomic force microscopy were used for surface roughness measurement. The chemical composition of the TiO2 surface and the oxidation state of Ti was investigated using X-ray photoelectron spectroscopy. The ccH3PO4 treatment significantly increased the wettability of the NP TiO2 surfaces (30°) compared to the untreated control (88°). The quantity of the absorbed phosphorus significantly increased following ccH3PO4 treatment compared to the control and caused the oxidation state of titanium to decrease (Ti4+ → Ti3+). Owing to its simplicity and robustness the presented surface treatment method may be utilized in the industrial-scale manufacturing of titanium implants.

Tomographic methods are used with ultrasonic guided wave wall thickness monitors to provide two-dimensional maps of the wall thickness throughout a monitored area. Tomographic monitoring systems are typically configured with 16 to 32 non-intrusive ultrasound transducers positioned in predetermined patterns for optimal coverage and resolution. Other monitoring systems have much fewer transducers, positioned according to the pipe geometry and wall area of main concern. Although these systems are not optimized for wall thickness mapping, the same or similar tomographic methods can improve analysis and interpretation of the datasets they produce. Algorithms are sought for implementation in responsive, interactive software for browsing and analysis of recorded wall thickness monitoring data. Simple tomographic algorithms are also desirable for use in embedded software. A "light weight" tomographic algorithm is outlined, and a prototype implementation is tested against a proven full-scale tomography software package. The two approaches produce similar results on small datasets corresponding to wall thickness monitoring systems with few transducers installed. For the larger datasets generated for high resolution wall thickness mapping, the reference software is superior in terms of both computational load and accuracy.

The phenomenon of Rayleigh wave attenuation due to surface roughness has been well studied theoretically in the literature. Three scattering regimes describing it have been identified-the Rayleigh (long wavelength), stochastic (medium wavelength), and geometric (short wavelength)-with the attenuation coefficient exhibiting a different behavior in each. Here, in an extension to our previous work, we gain further insight with regard to the existing theory, in three dimensions, using finite element (FE) modeling, under a unified approach, where the same FE modeling techniques are used regardless of the scattering regime. We demonstrate good agreement between our FE results and the theory in all scattering regimes. Additionally, following this demonstration, we extend the results to cases that lie outside the limits of validity of the theory.

This paper investigates the feasibility of a novel dual-mode electromagnetic NDE technique based on broadband Hall impedance and eddy current conductivity measurements for characterization of IN718 coupons shot-peened at Almen 4A-12A intensities. The measured data were inverted into residual stress and cold work depth profiles using an iterative inversion procedure and elastic and plastic gauge factors obtained by independent calibration tests conducted under uniaxial stress. Comparison between the inverted dual-mode NDE results and residual stress and cold work depth profiles obtained by destructive XRD testing showed good qualitative agreement. However, the quantitative agreement was found to leave much to be desired as the residual stress levels were significantly underestimated while the cold work levels were slightly overestimated. To mitigate this problem caused by simple but inaccurate approximations used in the inversion, an empirical correction was applied that reduced the elastic gauge factors by 32% and increased the plastic gauge factors by 32%. This single-parameter empirical correction significantly improved the accuracy of the inverted NDE residual stress and cold work depth profiles. To check if this method worked in thermally relaxed states, preliminary dual-mode NDE data were obtained from some of the shot-peened IN718 coupons after thermal exposure to 600 degrees C for 100 h. The measured data showed trends that were different from those expected based on linearized gauge factors and indicated that the highly accelerated thermal relaxation used in these tests led to thermally activated microstructural changes in the highly cold worked near-surface regions of the shot-peened IN718 coupons. Therefore, future work should be focused on thermally relaxed IN718 coupons exposed to less accelerated thermal relaxation that leads to less severe thermally activated microstructural changes.

This article presents a design procedure for structural health monitoring systems based on bulk wave ultrasonic sensors for structures fabricated from polycrystalline materials. When designing a monitoring system, maximum coverage per transducer is a general requirement in order for the system to be economic. For coarse-grained polycrystalline materials, monitoring is often made challenging by low signal-to-noise ratios caused by grain scattering. Therefore, when designing a monitoring system for these materials, in addition to the economic requirement, it needs to be ensured that an adequate signal-to-noise ratio can be obtained throughout the monitoring volume. This typically introduces a trade-off between volume coverage per transducer and sensitivity that must be investigated. In this article, this trade-off is studied and a methodology using signal-to-noise maps is presented to design the system, that is, choose the optimal transducer parameters and placement. First, a combined analytical and numerical approach is used to generate a signal-to-noise map. Then, the influence of various factors on signal-to-noise ratio is investigated. Finally, two representative examples, with different criteria, are given to illustrate the methodology. In one example, the full surface area of the testpiece is covered with transducers and the optimum gives the deepest coverage. The other one aims to achieve the minimum fractional surface area that has to be covered with transducers to monitor a narrow depth range far from the surface, which has a potential application in weld monitoring. Results show that the optimum is likely to be at much lower frequency than typically used in inspection, as tracking signals with time gives sensitivity gains. Experiments were carried out to illustrate that higher volume coverage can be obtained at lower frequencies.

Rayleigh waves are well known to attenuate due to scattering when they propagate over a rough surface. Theoretical investigations have derived analytical expressions linking the attenuation coefficient to statistical surface roughness parameters, namely, the surface's root mean squared height and correlation length and the Rayleigh wave's wavenumber. In the literature, three scattering regimes have been identified-the geometric (short wavelength), stochastic (short to medium wavelength), and Rayleigh (long wavelength) regimes. This study uses a high-fidelity two-dimensional finite element (FE) modelling scheme to validate existing predictions and provide a unified approach to studying the problem of Rayleigh wave scattering from rough surfaces as the same model can be used to obtain attenuation values regardless of the scattering regime. In the Rayleigh and stochastic regimes, very good agreement is found between the theory and FE results both in terms of the absolute attenuation values and for asymptotic power relationships. In the geometric regime, power relationships are obtained through a combination of dimensional analysis and FE simulations. The results here also provide useful insight into verifying the three-dimensional theory because the method used for its derivation is analogous.

Studying chaotic systems at all levels of physics education can highly motivate students to learn physics. In this paper two simple systems, the Duffing oscillator and compass needle motion, are presented, which were used in a high school and in a university setting for teaching the basic ideas of chaotic motion. Studying both systems can begin with their simple mechanical models, which connect the mathematical description to tangible reality for the students. To surmount the mathematical difficulties of the theoretical treatment of the models, freeware software, the Dynamics Solver (DS), was applied. It will be shown how DS can facilitate students’ first steps toward chaotic systems both at college and high school levels. Downloadable materials in ZIP format, related to this paper, can be found in our web page ( http://csodafizika.hu/ds_girepmptl ).

Abstract Background The purpose of this research was to investigate the effects of disinfection and three different sterilization methods on the dimensional changes and mechanical properties of three-dimensional (3D) printed surgical guide for implant therapy. The objective was to assess the effects of sterilization procedures in 3D printed drill guide templates with destructive and non-destructive material testing. Methods Fifteen identical drill guide templates were produced using a 3D printer. The surgical guides were classified into five groups: three controls, three disinfected (4% Gigasept®, 60 min), three plasma sterilized, three autoclave sterilized (+ 1 bar, 121 °C, 20 min), and three autoclave sterilized (+ 2 bar, 134 °C, 10 min). The templates were digitalized with a Steinbichler SCAN ST 3D scanner. Length was measured under an SZX16 stereomicroscope. A scanning electron microscope was used to study the surface morphology of the drill templates. The hardness, and flexural and compressive strength were measured to assess any changes in the physical characteristics of the material caused by sterilization. The drill guide templates were also examined with a Dage XiDAT 6600 X-ray. During the X-ray examinations, the following parameters were used: 100 kV voltage, 128 AVG averaging, 0.8 W power. One-way analysis of variance (ANOVA) was used to detect the difference between groups. Results Evaluation of the hardness measurements of the various specimens shows that the hardness of the material was not changed by the plasma sterilization (p = 0.0680), steam sterilization on 121 °C (p = 0.6033) or disinfection process (p = 0.1399). The statistical analysis revealed significant difference in hardness strength of the autoclave sterilized (134 °C) specimens (p = 0.0002). There was no significant difference between the goups regarding the scanning electron microscopic and stereomicroscopic examinations. There was no significant difference regarding the X-ray visibility of the templates to the effect of the disinfection (p = 0.7844), plasma sterilization (p = 0.4091) and steam sterilization on 121 °C (p = 0.9277) and steam sterilization on 131 °C (p = 0.093). The effect of the sterilization was the same in case of both flexural and compressive strength of the material. Conclusions Our findings indicate that plasma sterilization and steam sterilization at 121 °C were both suitable for sterilizing the tested 3D printed surgical guides.

Ultrasonic additive manufacturing (UAM) involves ultrasonic welding of similar or dissimilar metal foils on top of a base substrate. UAM can produce solid consolidated structures under optimal processing conditions. However, inter-layer defects such as delamination/kissing bonds (type 1) and inter-track (type 2) defects are common. The authors previously developed an ultrasonic nondestructive evaluation (NDE) monitoring methodology to quantify layer-bonding stiffness modeled as an interfacial spring. In this study, ultrasonic NDE is used to monitor the evolution of type 1 defects in a UAM component divided into two zones. The first represents the base/build interface comprising of the first few layers on the base substrate, and the second region represents the bulk of the UAM stack. A mechanism for the formation and evolution of type 1 defects was proposed based on NDE and optical examination. Type 2 defects are often more catastrophic and are challenging to repair. In the present work, a novel solid-state repair technique using friction stir processing (FSP) was used to repair typical UAM defects. The use of FSP ensures that the microstructural advantages of UAM are retained while improving the part quality. Two modes of FSP were designed—FSP from above for repair of inter-track (type 2) defects and FSP from below the base for the repair of base/build (type 1a) defects. The results of this study pave the way towards the development of an integrated solid-state additive manufacturing system with UAM as the primary bonding mechanism and FSP as an enhancement and repair tool.

The authors have recently developed a new technique for nondestructive Hall coefficient measurement based on inductive sensing of the Hall-Corbin current produced by the injection of high-frequency alternating current into the component under test. In this study, the feasibility of characterizing the combined influence of near-surface residual stress and cold work based on Hall impedance spectroscopy was investigated in shot-peened fully hardened IN718 coupons. First, a simple analytical approximation is proposed that allows the direct prediction of the measured frequency-dependent Hall impedance from the depth-dependent Hall coefficient and conductivity profiles. This approximation is based on the simplistic approximation originally developed for eddy current conductivity depth profiling that has been modified for Hall coefficient measurements. According to this approximation, Hall coefficient measurements exhibit roughly half the penetration depth of eddy current conductivity measurements taken at the same frequency. Typical depth profiles of the Hall coefficient and electric conductivity were estimated from residual stress and cold work depth profiles obtained by destructive X-ray diffraction (XRD) measurements. The corresponding Hall coefficient and electric conductivity depth profiles were determined using gauge factors obtained from experiments previously conducted to study the influence of applied stress and cold work on the Hall coefficient and electric conductivity in fully hardened IN718. These Hall coefficient and conductivity depth profiles were then used to predict the Hall impedance spectra using COMSOL FE simulations and the analytical approximation. The results of finite element simulations were in reasonable agreement with the analytical approximation and validate the predicted lower penetration depth of Hall current compared to the conduction current. Finally, the feasibility of Hall impedance measurements was demonstrated by experiments conducted between 100 kHz and 30 MHz on fully hardened IN718 coupons surface treated to three different shot-peening levels of 4A, 8A, and 12A Almen intensity.

Cracks in critical sections of steel structures pose a major safety concern in many industries. Existing high-frequency ultrasonic techniques offer high detection sensitivity to cracks but have poor inspection volume coverage, limiting their practical use for monitoring large areas of structures. Low-frequency guided waves have relatively high inspection area coverage and are currently used in pipeline monitoring for corrosion defects but face challenges in detecting critical cracks that often cause over an order of magnitude lower cross-sectional area loss. A study of scattering from small cracks in a thin-walled (<; 12 mm) section with an incident plane SH0 guided wave at higher frequencies but remaining below the SH1 cutoff is presented here using quasi-static approximations, the aim being to explore the possibility of using this regime for crack growth monitoring applications. A 3-D solution was developed using dimensional analysis, which showed that the SH0 reflection ratio is proportional to frequency to the power 1.5, to the effective crack size cubed, and is inversely proportional to the plate thickness and to the square root of the distance from the crack to the receiving sensor. Finite element analysis was used to validate these power coefficients and to calculate the proportionality constant. The results show that a higher inspection frequency offers improved sensitivity, but the validity of the results here is limited to the SH1 cutoff frequency. The predicted 3-D solution was validated by measurements on a pipe with a progressively grown notch.

Monitoring deterioration of material properties is important for assessing the structural integrity of engineering components, as it may indicate susceptibility to damage. This article focusses on the example of thermoelectric power measurements, which are known to be indicative of thermal and irradiation embrittlement and may therefore act as a proxy metric for material integrity. A passive thermoelectric power–monitoring technique is proposed which is suitable for permanent installation on engineering components. In passive measurements, the active perturbation (in this case, the heating required to create a temperature gradient) is replaced by incidental perturbation from the environment. The reduction in the ‘signal’ amplitude associated with relying on incidental perturbations may be compensated by increasing the number of individual measurements, facilitated by the greatly reduced power demand of the passive modality. Experimental studies using a stainless steel tube as a test component demonstrate thermoelectric power accuracy of <0.03 μV/°C is achievable with temperature gradients of the order of 2°C; in many cases of practical importance, this is sufficient to track the anticipated changes in thermoelectric power associated with thermal degradation.