Materials

Research

10 pages, 2693 KiB

Open AccessArticle

Variation in Magnetic Memory Testing Signals and Their Relationship with Stress Concentration Factors During Fatigue Tests Based on Back-Propagation Neural Networks

by Huipeng Wang, Qiaogen Wang and Huizhong Liu

Materials 2025, 18(5), 1008; https://doi.org/10.3390/ma18051008 - 25 Feb 2025

Viewed by 417

Abstract

To investigate the relationship between metal magnetic memory testing (MMMT) signals and stress concentration factors (SCFs), four-level sinusoidal constant-amplitude load tension–tension fatigue tests were carried out on 45CrNiMoVA steel specimens with different SCFs. The normal component of MMMT signals, H_p(y [...] Read more.

To investigate the relationship between metal magnetic memory testing (MMMT) signals and stress concentration factors (SCFs), four-level sinusoidal constant-amplitude load tension–tension fatigue tests were carried out on 45CrNiMoVA steel specimens with different SCFs. The normal component of MMMT signals, H_p(y), was collected during the fatigue tests, and three characteristics were extracted and analyzed during the tests, including the peak-to-peak value of abnormal peaks (ΔH_p(y)), the slope coefficient of the fitting line of H_p(y) (K₁), and the slope coefficient of the fitting line of H_p(y) between abnormal peaks (K₂), and a back-propagation (BP) neural network was developed to differentiate the SCF of the specimens. The results showed that both fatigue load and fatigue cycle number influenced MMMT signals, and the characteristics remained stable as the fatigue cycle number increased for the same fatigue load but increased significantly as fatigue load increased. In addition, all the characteristics increased as the distance between the scan line and the center line increased, but none of them could be used to differentiate the SCF of the specimens. With properly selected input vector and hidden nodes, the established BP neural network can quantitatively recognize the SCF of specimens. Full article

(This article belongs to the Special Issue Advanced Non-destructive Testing Techniques on Materials)

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11 pages, 4001 KiB

Open AccessArticle

Enhancing Reliability and Safety in Industrial Applications: Assessing the Applicability of Energy b-Value to Composites

by Doyun Jung and Jeonghan Lee

Materials 2024, 17(2), 447; https://doi.org/10.3390/ma17020447 - 17 Jan 2024

Cited by 2 | Viewed by 1090

Abstract

This study investigates the fracture behavior of glass fiber-reinforced plastic (GFRP) under various loading conditions using acoustic emission (AE) testing. Using fracture tests and time series analysis of AE signals, parameters such as b-value, improved b-value (Ib-value), and energy [...] Read more.

This study investigates the fracture behavior of glass fiber-reinforced plastic (GFRP) under various loading conditions using acoustic emission (AE) testing. Using fracture tests and time series analysis of AE signals, parameters such as b-value, improved b-value (Ib-value), and energy b-value (b_e-value) were examined to understand crack initiation, growth, and structural failure. The stress–strain curve revealed distinct responses during tensile and step loading, and time series analysis highlighted variations in amplitude, AE energy, and Kaiser and Felicity effects. Under tensile loading, the Ib-value exhibited a linear decrease, while step loading introduced complexities, including the Felicity effect. The b_e-value, incorporating energy considerations, fluctuated, providing insights into micro-cracks and macro-cracks. Statistical analysis demonstrated a consistent decrease in the b_e-value, emphasizing its potential for long-term monitoring. This study provides a comprehensive technique for assessing composite material fracture behavior, enhancing understanding for critical applications in hydrogen storage vessels and pressure pipes as well as advancing reliability and safety in industrial sectors. Full article

(This article belongs to the Special Issue Advanced Non-destructive Testing Techniques on Materials)

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11 pages, 7990 KiB

Open AccessCommunication

Tensile Failure Behaviors of Adhesively Bonded Structure Based on In Situ X-ray CT and FEA

by Jiawen Tang, Bo Niu, Yu Cao, Yayun Zhang and Donghui Long

Materials 2023, 16(24), 7609; https://doi.org/10.3390/ma16247609 - 12 Dec 2023

Cited by 4 | Viewed by 1406

Abstract

Adhesive bonding plays a pivotal role in structural connections, yet the bonding strength is notably affected by the presence of pore defects. However, the invisibility of interior pores severely poses a challenge to understanding their influence on tensile failure behaviors under loading. In [...] Read more.

Adhesive bonding plays a pivotal role in structural connections, yet the bonding strength is notably affected by the presence of pore defects. However, the invisibility of interior pores severely poses a challenge to understanding their influence on tensile failure behaviors under loading. In this study, we present a pioneering investigation into the real-time micro-failure mechanisms of adhesively bonded structures using in situ X-ray micro-CT. Moreover, the high-precision finite element analysis (FEA) of stress distribution is realized by establishing the real adhesive layer model based on micro-CT slices. The findings unveil that pores induce stress concentration within the adhesive layer during the tensile process, with stress levels significantly contingent upon pore sizes rather than their specific shapes. Consequently, larger pores initiate and propagate cracks along their paths, ultimately culminating in the failure of adhesively bonded structures. These outcomes serve as a significant stride in elucidating how pore defects affect the bonding performance of adhesively bonded structures, offering invaluable insights into their mechanisms. Full article

(This article belongs to the Special Issue Advanced Non-destructive Testing Techniques on Materials)

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31 pages, 32548 KiB

Open AccessArticle

Non-Destructive Characterization of Cured-in-Place Pipe Defects

by Richard Dvořák, Luboš Jakubka, Libor Topolář, Martyna Rabenda, Artur Wirowski, Jan Puchýř, Ivo Kusák and Luboš Pazdera

Materials 2023, 16(24), 7570; https://doi.org/10.3390/ma16247570 - 8 Dec 2023

Cited by 1 | Viewed by 2162

Abstract

Sewage and water networks are crucial infrastructures of modern urban society. The uninterrupted functionality of these networks is paramount, necessitating regular maintenance and rehabilitation. In densely populated urban areas, trenchless methods, particularly those employing cured-in-place pipe technology, have emerged as the most cost-efficient [...] Read more.

Sewage and water networks are crucial infrastructures of modern urban society. The uninterrupted functionality of these networks is paramount, necessitating regular maintenance and rehabilitation. In densely populated urban areas, trenchless methods, particularly those employing cured-in-place pipe technology, have emerged as the most cost-efficient approach for network rehabilitation. Common diagnostic methods for assessing pipe conditions, whether original or retrofitted with-cured-in-place pipes, typically include camera examination or laser scans, and are limited in material characterization. This study introduces three innovative methods for characterizing critical aspects of pipe conditions. The impact-echo method, ground-penetrating radar, and impedance spectroscopy address the challenges posed by polymer liners and offer enhanced accuracy in defect detection. These methods enable the characterization of delamination, identification of caverns behind cured-in-place pipes, and evaluation of overall pipe health. A machine learning algorithm using deep learning on images acquired from impact-echo signals using continuous wavelet transformation is presented to characterize defects. The aim is to compare traditional machine learning and deep learning methods to characterize selected pipe defects. The measurement conducted with ground-penetrating radar is depicted, employing a heuristic algorithm to estimate caverns behind the tested polymer composites. This study also presents results obtained through impedance spectroscopy, employed to characterize the delamination of polymer liners caused by uneven curing. A comparative analysis of these methods is conducted, assessing the accuracy by comparing the known positions of defects with their predicted characteristics based on laboratory measurements. Full article

(This article belongs to the Special Issue Advanced Non-destructive Testing Techniques on Materials)

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12 pages, 10407 KiB

Open AccessArticle

Characteristic Parameters of Magnetostrictive Guided Wave Testing for Fatigue Damage of Steel Strands

by Xiaohui Chen, Jiang Xu, Yong Li and Shenghuai Wang

Materials 2023, 16(15), 5215; https://doi.org/10.3390/ma16155215 - 25 Jul 2023

Cited by 2 | Viewed by 1615

Abstract

Steel strands are widely used in structures such as bridge cables, and their integrity is critical to keeping these structures safe. A steel strand is under the working condition of an alternating load for a long time, and fatigue damage is unavoidable. It [...] Read more.

Steel strands are widely used in structures such as bridge cables, and their integrity is critical to keeping these structures safe. A steel strand is under the working condition of an alternating load for a long time, and fatigue damage is unavoidable. It is necessary to find characteristic parameters for evaluating fatigue damage. In this study, nonlinear coefficients and attenuation coefficients were employed to evaluate fatigue damage based on magnetostrictive guided wave testing. Unlike pipe and steel wire structures, there is a phenomenon of a notch frequency when guided waves propagate in steel strands. The influence of the notch frequency on the nonlinear coefficient and attenuation coefficient is discussed. The relationship between the nonlinear coefficient, attenuation coefficient, and cyclic loading times was obtained through experiments. The amplitudes of the nonlinear coefficient and attenuation coefficient both increased with the increase in cyclic loading times. The experiments also showed the effectiveness of using these two characteristic parameters to evaluate fatigue damage. Full article

(This article belongs to the Special Issue Advanced Non-destructive Testing Techniques on Materials)

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17 pages, 5248 KiB

Open AccessArticle

Highly Sensitive Detection of Microstructure Variation Using a Thickness Resonant Transducer and Pulse-Echo Third Harmonic Generation

by Hyunjo Jeong, Hyojeong Shin, Shuzeng Zhang and Xiongbing Li

Materials 2023, 16(13), 4739; https://doi.org/10.3390/ma16134739 - 30 Jun 2023

Cited by 1 | Viewed by 1259

Abstract

In nonlinear ultrasound testing, the relative nonlinear parameter is conveniently measured as a sensitive means of detecting and imaging overall variation of microstructures and damages. Compared to the quadratic nonlinear parameter (

β^{'}

), the cubic nonlinear parameter (

γ^{'}

), [...] Read more.

In nonlinear ultrasound testing, the relative nonlinear parameter is conveniently measured as a sensitive means of detecting and imaging overall variation of microstructures and damages. Compared to the quadratic nonlinear parameter (

β^{'}

), the cubic nonlinear parameter (

γ^{'}

), calculated as the third harmonic amplitude divided by the cube of the fundamental amplitude, has generally a higher value, providing better sensitivity in nonlinear parameter mapping. Since the third harmonic amplitude is about two orders of magnitude lower than the fundamental amplitude, efficient excitation and highly sensitive reception of third harmonic is very important. In this paper, we explore an odd harmonic thickness resonant transducer that meets the requirements for pulse-echo third harmonic generation (THG) measurements. We also address the problem of source nonlinearity that may be present in the measured amplitude of the third harmonic and propose a method to properly correct it. First, we measure

γ^{'}

for a series of aluminum specimens using the through-transmission method to observe the behavior of

γ^{'}

as a function of specimen thickness and input voltage, and examine the effects of various corrections such as attenuation, diffraction and source nonlinearity. Next, we apply the odd harmonic resonant transducer to pulse-echo THG measurements of precipitation heat-treated specimens. It is shown that such transducer is very effective in generation and detection of fundamental and third harmonics under finite amplitude toneburst excitation. The highly sensitive detectability of

γ^{'}

are presented as a function of aging time, and the sensitivity of

γ^{'}

is compared with that of

β^{'}

and

{β^{'}}^{2}

. Full article

(This article belongs to the Special Issue Advanced Non-destructive Testing Techniques on Materials)

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14 pages, 3821 KiB

Open AccessArticle

Near-Surface-Defect Detection in Countersunk Head Riveted Joints Based on High-Frequency EMAT

by Shuchang Zhang, Jiang Xu, Xin Yang and Hui Lin

Materials 2023, 16(11), 3998; https://doi.org/10.3390/ma16113998 - 26 May 2023

Cited by 3 | Viewed by 1623

Abstract

Countersunk head riveted joints (CHRJs) are essential for the aerospace and marine industries. Due to the stress concentration, defects may be generated near the lower boundary of the countersunk head parts of CHRJs and require testing. In this paper, the near-surface defect in [...] Read more.

Countersunk head riveted joints (CHRJs) are essential for the aerospace and marine industries. Due to the stress concentration, defects may be generated near the lower boundary of the countersunk head parts of CHRJs and require testing. In this paper, the near-surface defect in a CHRJ was detected based on high-frequency electromagnetic acoustic transducers (EMATs). The propagation of ultrasonic waves in the CHRJ with a defect was analyzed based on the theory of reflection and transmission. A finite element simulation was used to study the effect of the near-surface defect on the ultrasonic energy distribution in the CHRJ. The simulation results revealed that the second defect echo can be utilized for defect detection. The positive correlation between the reflection coefficient and the defect depth was obtained from the simulation results. To validate the relation, CHRJ samples with varying defect depths were tested using a 10-MHz EMAT. The experimental signals were denoised using wavelet-threshold denoising to improve the signal-to-noise ratio. The experimental results demonstrated a linearly positive correlation between the reflection coefficient and the defect depth. The results further showed that high-frequency EMATs can be employed for the detection of near-surface defects in CHRJs. Full article

(This article belongs to the Special Issue Advanced Non-destructive Testing Techniques on Materials)

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13 pages, 6566 KiB

Open AccessArticle

Debonding Detection in Aluminum/Rigid Polyurethane Foam Composite Plates Using A₀ Mode LAMB Wave EMATs

by Xin Yang, Jiang Xu, Shuchang Zhang and Jun Tu

Materials 2023, 16(7), 2797; https://doi.org/10.3390/ma16072797 - 31 Mar 2023

Cited by 10 | Viewed by 2003

Abstract

Aluminum/rigid polyurethane foam composite plates (ARCPs) are widely used for thermal insulation. The interface debonding generated during manufacturing degrades the thermal insulation performance of an ARCP. In this study, the debonding of an ARCP, a composite plate with a porous and damped layer [...] Read more.

Aluminum/rigid polyurethane foam composite plates (ARCPs) are widely used for thermal insulation. The interface debonding generated during manufacturing degrades the thermal insulation performance of an ARCP. In this study, the debonding of an ARCP, a composite plate with a porous and damped layer of rigid polyurethane foam (RPUF), was detected using A₀ mode Lamb wave electromagnetic acoustic transducers (EMATs). The low energy transmission coefficient at the interface caused by the large acoustic impedance difference between aluminum and RPUF made the detection difficult. Based on these structural characteristics, an A₀ mode Lamb wave with large out-of-plane displacement was used to detect the debonding. EMATs are preferred for generating A₀ mode Lamb waves due to their advantages of being noncontact, not requiring a coupling agent, and providing convenient detection. A finite element simulation model considering the damping of the RPUF layer, the damping of the PU film at the interface, and the bonding stiffness of the interface was established. The simulation results indicated that the Lamb wave energy in the aluminum plate transmits into the RPUF layer in small amounts. However, the transmitted energy rapidly attenuated and was not reflected into the aluminum plate, as the RPUF layer was thick and highly damped. Therefore, energy attenuation was evident and could be used to characterize the debonding. An approximately linear relationship between the amplitude of the received signals and the debonding length was obtained. Experiments were performed on an ARCP using EMATs, and the experimental results were in good agreement with the simulation results. Full article

(This article belongs to the Special Issue Advanced Non-destructive Testing Techniques on Materials)

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15 pages, 3861 KiB

Open AccessArticle

Study on the Effect of Metal Mesh on Pulsed Eddy-Current Testing of Corrosion under Insulation Using an Early-Phase Signal Feature

by Hanqing Chen, Zhiyuan Xu, Zhen Zhou, Junqi Jin and Zihua Hu

Materials 2023, 16(4), 1451; https://doi.org/10.3390/ma16041451 - 9 Feb 2023

Cited by 5 | Viewed by 2118

Abstract

Corrosion under insulation (CUI) is a major threat to the structural integrity of insulated pipes and vessels. Pulsed eddy-current testing (PECT) is well known in the industry for detecting CUI, but its readings can be easily influenced by nearby conductive objects, including the [...] Read more.

Corrosion under insulation (CUI) is a major threat to the structural integrity of insulated pipes and vessels. Pulsed eddy-current testing (PECT) is well known in the industry for detecting CUI, but its readings can be easily influenced by nearby conductive objects, including the insulation supporting metal mesh. As a sequel to our previous study, this paper focuses on the surface distribution of eddy currents at the time of the turning off of the driving voltage instead of examining the overall process of eddy current diffusion. Based on the fact that CUI takes place on the outside of the insulated specimen, the probe footprint was calculated only on the specimen surface. The corrosion depth was regarded as an increment to the probe lift-off, whose information was carried in the early PECT signal. Finite element simulations were performed to facilitate the calculation of the probe footprint and predict the signal behavior. The peak value, which appeared in the early phase of the differential PECT signal, was found to be well correlated with the corrosion depth. Further studies revealed that the mild steel mesh could result in the enlargement of the probe footprint and a decrease in the change rate of the peak value in relation to the corrosion depth. Finally, experiments were conducted to verify the simulation results. The presented findings are consistent with the previously reported results and provide a potential alternative to evaluate CUI in specific scenarios where the insulation has a fixed and uniform thickness. Full article

(This article belongs to the Special Issue Advanced Non-destructive Testing Techniques on Materials)

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