Predicting the Delamination Mechanisms of Multidirectional Laminates Using the Energy Release Rate Obtained from AE Monitoring

This study investigates delamination damage mechanisms during the double cantilever beam standard test using the strain energy release rate. The acoustic emission parameter is used to replace the original calculation method of measuring crack length to predict delamination. For this purpose, 24-layer glass/epoxy multidirectional specimens with different layups, and interface orientations of 0°, 30°, 45°, and 60°, were fabricated based on ASTM D5528 (2013). Acoustic emission testing (AE) is used to detect the damage mechanism of composite multidirectional laminates (combined with microscopic real-time observation), and it is verified that the strain energy release rate can be used as a criterion for predicting delamination damage in composite materials. By comparing the AE results with the delamination expansion images observed by microvisualization in real time, it is found that the acoustic emission parameters can predict the damage of laminates earlier. Based on the data inversion of the acoustic emission parameters of the strain energy release rate, it is found that the strain energy release rate of the specimens with different fiber interface orientations is consistent with the original calculated results.

Concrete Damage Identification based on Acoustic Emission and Wavelet Neural Network

In order to improve the accuracy of damage source identification in concrete based on acoustic emission testing (AE) and neural networks, and locating and repairing the damage in a practical roller compacted concrete (RCC) dam, a multilevel AE processing platform based on wavelet energy spectrum analysis, principal component analysis (PCA), and a neural network is proposed. Two data sets of 15 basic AE parameters and 23 AE parameters added on the basis of the 15 basic AE parameters were selected as the input vectors of a basic parameter neural network and a wavelet neural network, respectively. Taking the measured tensile data of an RCC prism sample as an example, the results show that compared with the basic parameter neural network, the wavelet neural network achieves a higher accuracy and faster damage source identification, with an average recognition rate of 8.2% and training speed of about 33%.

NDE Outlook: Informatization of NDT and NDE

Informatization is defined as the process by which information technologies, such as the World Wide Web and other communication technologies, have transformed economic and social relations to such an extent that cultural and economic barriers are minimized. What does this mean for nondestructive testing and evaluation (NDT/E)? In short: informatization in NDT and NDE has happened and will continue to happen, independent of whether individuals or companies like it or not. However, we can shape it—together.

2021 Revisions to ASTM E1417/E1417M and E1444/E1444M

This article provides an overview of the 2021 revisions to the industry standards for aerospace liquid penetrant and magnetic particle inspections, ASTM E1417/1417M and ASTM E1444/E1444M.

Assessing Mottled Indications when Digitally Radiographing Austenitic Stainless Steel Welds

When radiographing an austenitic stainless steel weld with an appreciable weld deposit size, selecting a low radiographic kilovoltage (keV) can contribute to producing a radiographic indication that is not an imperfection. The contributors to this mottled condition are both radiographical and metallurgical. Electrons from low keV can diffract or absorb when penetrating through the dendritic grain structure of a weld. The increase in keV, or using gamma ray–equivalent isotopes, produces a marked change in electron output and penetration in material.

Advantages of Compound S-scan over Sectorial Scan or E-scan: A Case Study

Within PAUT, inspectors have the option to apply various scanning techniques for performing weld inspections according to their configurations. These include the sectorial scan (S-scan) or a fixed-angle electronic scan (E-scan), or a combination of both called a compound S-scan. Compound S-scan, introduced around 2015 (Magruder 2016), has not been much explored, as not enough data can be extracted from the available resources to determine its effectiveness for inspection. Therefore, the author has taken a specific interest in studying this technique by comparing the available PAUT scanning techniques and providing options for selecting the most appropriate scanning techniques for the intended applications. For this purpose, a 25 mm thick welder qualification test plate with natural defects (verified by RT) was studied.

Multiwave Total Focusing Method for Full-Matrix Imaging Using Ultrasonic Phased Array

The imaging range of the traditional total focusing method (TFM) is usually limited by the directivity of excitation of a single wave pattern. In this paper, a multiwave TFM technique is proposed, which uses both compression and shear vertical (SV) waves for detection and imaging simultaneously. Based on this technique, a special ultrasonic transducer for multiwave detection is designed that can balance the excitation amplitude of compression and SV waves. Multiwave TFM uses the compression and SV wave fields generated by the same excitation, and the signals reflected by the two sound fields passing through the discontinuity are received. The signals are respectively processed by TFM according to the compression and SV wave velocities. The two processed signals are shifted and aligned according to the time difference between the compression wave with SV wave propagation, and then added together. Finally, the detection image of the block is obtained. Through simulation and experiments, it is shown that the special transducer can optimize the imaging range and effect of multiwave TFM, and multiwave TFM can effectively detect discontinuities and reduce the rate of missed detection at higher steering angles. The detection results show that the maximum amplitude gain of multiwave TFM relative to TFM can be increased about 6 dB.

Ultrasonic Evaluation of Porosity in Out-of-Autoclave Carbon Fiber–Reinforced Polymer Composite Material

Ultrasonic longitudinal wave propagation is studied in out-of-autoclave (OoA) carbon fiber–reinforced polymer composite material with varying levels of porosity contents. A combination of cure pressures and a solvent is used to produce specimens with void contents in the range of 0% to 22%. Ultrasonic measurements are made in through-transmission mode, and the data is processed to study various aspects of wave interaction with porosity in OoA specimens. The specimens with a wide range of void contents have enabled the study of broader trends of ultrasonic center frequency, wave velocity, and attenuation with respect to porosity. Results show ultrasonic center frequency and wave velocity are decreased linearly as the void content increases. The relationship of ultrasonic wave attenuation can be approximated by a logarithmic relationship when considering the full range of void content studied. Strength measurements of specimens with varying void contents are made using the flatwise tensile (FWT) test. It is observed that the strength rapidly decreases with increasing porosity. Correlations made between FWT strength, ultrasonic wave velocity, and attenuation are best described by logarithmic relationships. The data shows a potential for inferring strength knockdowns due to the presence of porosity based on ultrasonic measurements.

Nondestructive Evaluation of Electroplating-Induced Hydrogen Embrittlement in Cadmium-Coated High-Strength Steel Using Ultrasonic Surface Waves

Development of a nondestructive evaluation (NDE) method to detect nascent hydrogen embrittlement (HE) in electroplated high-strength steel parts is becoming important for the aerospace industry. This research investigates the feasibility of surface acoustic waves (SAWs) measurements to distinguish between cadmium (Cd) plated SAE 4340 steel samples with low and high HE susceptibilities. SAWs were generated with a 10 MHz piezoelectric transducer and detected by line scans via a laser Doppler vibrometer setup. Using signal processing algorithms in MATLAB, SAW velocities as well as attenuation coefficients were estimated. Depth profiles of steel hardness near coatings were also evaluated using Vickers microindentation tests. Average steel hardness in not-baked samples was slightly increased. Cd coatings were characterized by laser and optical microscopy methods. Small variations found in thickness and surface roughness of the Cd coatings among the samples did not significantly affect the NDE results. On average, samples in the not-baked condition (high HE risk) exhibited lower SAW attenuation coefficients compared to immediately baked and late-baked conditions (low HE risk). However, it was not possible to distinguish between the manufacturing conditions of individual samples due to overlaps in attenuation measurement results. SAW velocities as estimated by the cross-correlation method were found to be not sensitive to manufacturing conditions.

Automated Condition Monitoring with Remaining Lifetime Assessment for Wire Ropes in Ladle Cranes

The hazards and deterioration of operating wire ropes on overhead cranes, which articulate the ladle in the basic oxygen steelmaking process and are subjected to intensive periodic loads and exposure to high temperatures, are discussed. An automated condition monitoring system (ACMS) based on a magnetic flux leakage testing (MFL) flaw detector permanently installed on the rope under test is used. An algorithm of the rope’s residual tensile strength assessment is provided. A specially developed software that submits a decision on the rope’s condition to the crane operator is described. The practice of combining magnetic rope testing (MRT) and tensile strength analysis for the quantitative assessment of rope condition is reviewed. Practical issues are also discussed, such as how to establish the condition monitoring process, set loss thresholds for rope metallic cross-sectional area, and safely prolong the service life of rope.