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Piezoelectric materials, which exhibit a charge distribution across the surfaces in reaction to mechanical strain, find significant utility in actuation and sensing applications. Apart from actuation applications like acoustic devices, motors, and vibration damping, an emerging domain for ultrasonic actuators lies in additive manufacturing processes. Ultrasonic waves applied during solidification aim to modulate grain structure and minimize defects. This research focuses on a fixture designed to facilitate and optimize ultrasonic wave propagation through the build plate in laser powder bed fusion additive manufacturing by utilizing a piezoelectric transducer. Three implementations of piezoelectric transducers were evaluated based on their out-of-plane ultrasonic velocity transmissions. It was determined that a thin plate adhered to the surface of the piezoelectric transducer yielded the most favorable outcomes for implementation, achieving 100% transmission of velocity and energy. Preliminary analysis of melt pool morphology and defects in single-track laser scanning experiments demonstrated the impact of ultrasound on solidification, hinting at a novel approach to enhancing the printability of alloys in laser powder bed fusion additive manufacturing processes. The optimal fixture and the explored transducing efficiency could further guide advanced ultrasound testing to enable in situ defect and texture detection during the additive manufacturing processes.

Delamination represents one of the most significant and dangerous damages in composite plates. Recently, many papers have presented the capability of structural health monitoring (SHM) techniques for the investigation of structural delamination with various shapes and thickness depths. However, few studies have been conducted regarding the utilization of convolutional neural network (CNN) methods for automating the non-destructive testing (NDT) techniques database to identify the delamination size and depth. In this paper, an automated system qualified for distinguishing between pristine and damaged structures and classifying three classes of delamination with various depths is presented. This system includes a proposed CNN model and the Lamb wave technique. In this work, a unidirectional composite plate with three samples of delamination inserted at different depths was prepared for numerical and experimental investigations. In the numerical part, the guided wave propagation and interaction with three samples of delamination were studied to observe how the delamination depth can affect the scattered and trapped waves over the delamination region. This numerical study was validated experimentally using an efficient ultrasonic guided waves technique. This technique involved piezoelectric wafer active sensors (PWASs) and a scanning laser Doppler vibrometer (SLDV). Both numerical and experimental studies demonstrate that the delamination depth has a direct effect on the trapped waves’ energy and distribution. Three different datasets were collected from the numerical and experimental studies, involving the numerical wavefield image dataset, experimental wavefield image dataset, and experimental wavenumber spectrum image dataset. These three datasets were used independently with the proposed CNN model to develop a system that can automatically classify four classes (pristine class and three different delamination classes). The results of all three datasets show the capability of the proposed CNN model for predicting the delamination depth with high accuracy. The proposed CNN model results of the three different datasets were validated using the GoogLeNet CNN. The results of both methods show an excellent agreement. The results proved the capability of the wavefield image and wavenumber spectrum datasets to be used as input data to the CNN for the detection of delamination depth.

Piezoelectric effects were first discovered more than a hundred years ago and, since then, have been widely used across various fields [...]

Piezoelectric materials are defined by their ability to display a charge across their surface in response to mechanical strain, making them great for use in sensing applications. Such applications include pressure sensors, medical devices, energy harvesting and structural health monitoring (SHM). SHM describes the process of using a systematic approach to identify damage in engineering infrastructure. A method of SHM that uses piezoelectric wafers connected directly to the structure has become increasingly popular. An investigation of a novel pitch-catch method of determining instrumentation quality of piezoelectric wafer active sensors (PWASs) used in SHM was conducted as well as an investigation into the effects of defects in piezoelectric sensors and sensor bonding on the sensor response. This pitch-catch method was able to verify defect-less instrumentation quality of pristinely bonded PWASs. Additionally, the pitch-catch method was compared with the electromechanical impedance method in determining defects in piezoelectric sensor instrumentation. Using the pitch-catch method, it was found that defective instrumentation resulted in decreasing amplitude of received and transmitted signals as well as changes in the frequency spectrums of the signals, such as the elimination of high frequency peaks in those with defects in the bonding layer and an increased amplitude of around 600 kHz for a broken PWAS. The electromechanical impedance method concluded that bonding layer defects increase the primary frequency peak’s amplitude and cause a downward frequency shift in both the primary and secondary frequency peaks in the impedance spectrum, while a broken sensor has the primary peak amplitude reduced while shifting upward and nearly eliminating the secondary peak.

Acoustic emission (AE) was monitored during stress intensity factor (SIF)-controlled high-cycle fatigue (HCF) tests on an aluminum 2024-T3 specimen with a fatigue crack growing at its center. The SIF control was implemented in such a manner that crack growth could be slowed down and even inhibited while the fatigue experiment continued. In the beginning, a specific type of AE signal was observed while the crack was allowed to grow to up to approximately 9.4 mm in length. Subsequently, the load was reduced in order to control the SIF value at the crack tip and to inhibit the crack growth. AE signals were recorded even when the crack stopped growing, although the specific signature of these AE signals was different from those observed when the crack was growing, as discussed in the text. The gist of the phenomenon reported in this article is that strong AE signals could still be observed even when the crack stopped growing. These latter AE signals could be due to rubbing and clapping of the crack faying surfaces. Travel analysis was consistently performed to ensure that these AE signals were originating from the crack, though not necessarily from the crack tip. In addition, absorbing clay wave dams were built around the crack region to inhibit boundary reflections and grip noise. Fast Fourier Transform (FFT) and Choi–Williams Transform (CWT) analysis were performed to classify the AE signals. It was observed that the AE signals related to crack growth were clearly different from the AE signals originating from the crack while the crack was not growing. Strong S0-mode Lamb wave components were observed in the crack-growth AE signals, whereas strong A0-mode Lamb wave components dominated the non-crack-growth AE signals. Pearson correlation clustering analysis was performed to compare the crack-growth and non-crack growth AE signals. We propose that the fatigue-crack faying surfaces may undergo rubbing and/or clapping during fatigue cyclic loading and thus produce strong AE signals that are registered by the AE system as hits, although the crack is not actually growing. The understanding of this phenomenon is very important for the design of the structural health monitoring (SHM) system based on AE-hit signal capture and interpretation.

The acoustic emission (AE) technique has become a well-established method of monitoring structural health over recent years. The sensing and analysis of elastic AE waves, which have involved piezoelectric wafer active sensors (PWAS) and time domain and frequency domain analysis, has proven to be effective in yielding fatigue crack-related information. However, not much research has been performed regarding (i) the correlation between the fatigue crack length and AE signal signatures and (ii) artificial intelligence (AI) methodologies to automate the AE waveform analysis. In this paper, this crack length correlation is investigated along with the development of a novel AE signal analysis technique via AI. A finite element model (FEM) study was first performed to understand the effects of fatigue crack length on the resulting AE waveforms and a fatigue experiment was performed to capture experimental AE waveforms. Finally, this database of experimental AE waveforms was used with a convolutional neural network to build a system capable of performing automated classification and prediction of the length of a fatigue crack that excited respective AE signals. AE signals captured during a fatigue crack growth experiment were found to match closely with the FEM simulations. This novel AI system proved to be effective at predicting the crack length of an AE signal at an accuracy of 98.4%. This novel AI-enabled AE signal analysis technique will provide a crucial step forward in the development of a comprehensive structural health monitoring (SHM) system.

BackgroundNoncontrast CT (NCCT) is used to evaluate for intracerebral hemorrhage (ICH) and ischemia in acute ischemic stroke (AIS). Large vessel occlusions (LVOs) are a major cause of AIS, but challenging to detect on NCCT.AimsThe purpose of this study is to evaluate an AI software called RAPID NCCT Stroke (RAPID, iSchemaView, Menlo Park, CA) for ICH and LVO detection compared to expert readers.MethodsIn this IRB approved retrospective, multicenter study, stand-alone performance of the software was assessed based on the consensus of 3 neuroradiologists and sensitivity and specificity were determined. The platform’s performance was then compared to interpretation by readers comprised of eight general radiologists (GR) and three neuroradiologists (NR) in detecting ICH and hyperdense vessel sign (HVS) indicating LVO.ResultsA total of 244 cases were included. Of the 244, 115 were LVOs and 26 were ICHs. One hundred three cases did not have LVO nor ICH. Stand-alone performance of the software demonstrated sensitivities and specificities of 96.2 and 99.5% for ICH and 63.5 and 95.1% for LVO detection. Compared to all 11 readers and eight GR readers only respectively, the software demonstrated superiority, achieving significantly higher sensitivities (63.5% versus 43.6%, p

Introduction Idiopathic intracranial hypertension (IIH) is a pathology involving an increase in intracranial pressure leading to symptoms including papilledema, tinnitus, and elevated cerebrospinal fluid opening pressure. Recent research has identified venous sinus stenosis as a cause of IIH, a common treatment of which is venous stenting and angioplasty. An adverse event of this procedure is in‐stent stenosis (ISS), due to either neointimal hyperplasia or hypersensitivity to an element in the stent. There has been speculation regarding whether nickel in intracranial stents is a cause of concern, due to its potential to cause a Type IV hypersensitivity reaction and ISS, which is an indicator of future stroke. The purpose of this case report is to determine if the cobalt‐based alloy Onyx Resolute intracranial stents can safely treat IIH in patients with allergic contact dermatitis to nickel. Methods We present a 38‐year old woman who presented with migraines and IIH with papilledema and severe pulsatile tinnitus. Headaches had been present for 5‐10 years. Ophthalmology consult revealed bilateral papilledema, upon which an MRI and MRV revealed venous stenosis. There was a 17mmHg pressure gradient measured in the patient. Patient could not tolerate acetazolamide, with kidney stones and loss of sheen in hair. Cerebral angiogram indicated right transverse‐sigmoid junction stenosis and atretic left venous sinus. The patient had an Onyx Resolute stent placed in the right transverse sigmoid junction. The Onyx Resolute stent is a Zotarolimus‐eluting stent made up of a cobalt‐based shell and a platinum‐Iridium core and is not recommended for patients with a hypersensitivity to nickel, cobalt, or chromium, but has a lower nickel content than a self‐expanding stent. Results Patient underwent cerebral angiogram, revealing right transverse‐sigmoid junction stenosis with a 17mmHg pressure gradient. Stenting and angioplasty were performed; this reduced the venous sinus pressure in the R transverse sinus (pre‐stenotic segment) from 43 mm Hg to 24 mm Hg with resolution of the R transverse‐sigmoid junction pressure gradient. Patient was treated with prasugrel (Effient) for one month. At the one‐month follow‐up, the patient reported an improvement of symptoms, with near‐resolution of her prior headaches in terms of severity and frequency following her procedure. Visual acuity is at baseline, pending formal follow‐up assessment for papilledema. Follow‐up CT Head Venogram with and without contrast showed a patent R transverse to sigmoid venous stent. The patient was continued on aspirin 81mg daily and prasugrel 5mg daily and is to continue follow‐up with yearly ophthalmologic exams. Conclusion Although there is speculation regarding the use of metal intracranial stents in patients allergic to nickel, our patient has shown that it is safe to use the Onyx Resolute intracranial stent despite a pre‐existing nickel hypersensitivity.

Introduction Mycotic aneurysms of paraspinal arteries are a rare finding. The most commonly affected vessels include the aorta, iliac, visceral, femoral, brachial, and cerebral arteries, often occurring in the setting of bacteremia, direct invasion from local infection, septic emboli from infective endocarditis, or arterial trauma.¹⁻³ However, there is limited existing documentation of mycotic aneurysms of the spinal vasculature.² Furthermore, knowledge regarding the management of paraspinal mycotic aneurysms and the efficacy of endovascular repair of these lesions is scarce.⁴ Methods We present a 51‐year‐old male with a past medical history of diabetes mellitus, end‐stage renal disease on hemodialysis (T/T/S), hypertension, congestive heart failure, peripheral arterial disease s/p right bilateral knee amputation, coronary artery disease, and epilepsy that presented with a 2‐week duration of severe low back pain with associated left upper and lower extremity numbness, subjective fevers, generalized weakness, diffuse abdominal pain, nausea and vomiting. Neurological exam on admission was remarkable for left lower extremity paresthesia of no clear dermatomal distribution with no other focal deficits. CT of the abdomen and pelvis revealed concern for L3‐L4 discitis and osteomyelitis and a greater than 3 cm homogeneously enhancing lesion within the paraspinal muscles of the same level concerning for neoplasm vs. vascular malformation vs. pseudoaneurysm (Figure 1A). An emergent MRI lumbar spine revealed a left L3 radicular artery saccular aneurysm concerning for a mycotic aneurysm in the setting of infection (Figure 1B). Results Patient underwent cerebral and spinal angiography which showed a left L3 radicular artery ruptured mycotic aneurysm measuring 11.26 x 6.5 mm in mediolateral and craniocaudal diameters associated with a 16.4 x 21 mm pseudoaneurysm (Figure 1C). Successful coiling of the aneurysm, pseudoaneurysm, and fistulous connection were performed with Penumbra 400 coils and PAC coils. There was no opacification of the aneurysms at the end of the procedure and no procedural complications (Figure 1D). CT‐guided biopsy of the L3‐L4 disc was also obtained. Postoperatively, the patient was hypertensive to a systolic blood pressure of 220 mmHg that was controlled with a nicardipine infusion that was gradually weaned off once the patient’s vitals were stable while in the Neuro‐ICU. The patient’s discitis and osteomyelitis were identified as the source of infection for the aneurysm and managed medically with IV antibiotics and analgesics with no need for any acute neurosurgical intervention. Blood cultures showed no growth throughout admission and biopsy of lumbar vertebrae showed normal skin flora. Patient with stable neurological exam throughout his stay. Patient was transferred to the floor before ultimately discharging home per patient preference. Conclusion Endovascular embolization is a potentially efficacious therapy for the management of mycotic aneurysms of the spinal vasculature. Endovascular repair has been demonstrated as a surgical option for mycotic aneurysms in other vessels, such as the aorta, but further research and replication are needed to establish the utility of coiling in the setting of paraspinal mycotic aneurysms.⁵⁻⁷

Introduction Flat‐panel CT provides quick and effective parenchymal cross‐sectional imaging. Pre‐thrombectomy, flat‐panel can be obtained to evaluate ischemic stroke patients for thrombectomy candidacy in cases where the traditional CT scanner is bypassed. Post‐thrombectomy images obtained from flat‐panel CT are also effective in evaluating complications such as contrast extravasation, hemorrhage, or increased core size. Findings on flat‐panel CT may provide information to guide decisions such as blood pressure goals, antiplatelet or anticoagulation regimen, thrombolytic reversal, and the need for emergent neurosurgical intervention in rare cases. Methods We analyzed 93 thrombectomy cases from 2021 to 2022, where flat‐panel CT was obtained, with follow‐up CT and MRI. Demographics were reviewed for this series of cases. Cases where stratified and compared depending on results on flat‐panel CT. Medical records were reviewed for changes in management. The local IRB approved the project, and consent was waived according to institutional guidelines. Results For our patient population, the median age was 70; race was 59% Caucasian, 40% African American, and 1% Hispanic; and gender was 46% female and 54% male. From the flat‐panel CT, we had the following results: Flat‐panel CT was normal in 68% of cases, 20% had contrast extravasation, 9% showed evidence of contrast extravasation vs. hemorrhage, 2% had hemorrhage during the procedure, and 1% had contrast retained in the vessels. On follow‐up CT, 35% had no change, 16% had contrast extravasation, 8% had SAH, 4% had contrast extravasation vs. hemorrhage, 3% had hemorrhagic transformation, 1% had IVH, 1% had petechial hemorrhages, and 31% had no follow‐up CT. On MRI, 20% had hemorrhagic transformation, 41% had no hemorrhage, 6% had microhemorrhages, 10% had petechial hemorrhages, 2% had ICH, 1% had 1 IVH, 1% had SAH, 1% had contrast extravasation, 17% of the cases had no follow‐up MRI. Based on flat‐panel CT, results for normal and contrast extravasation were as follows (Table 1.). Therapy was altered by the flat‐panel CT results in 10 cases. The main change in therapy was a delay in restarting antiplatelet and anticoagulation therapy, which took place in 9 cases. Conclusions Post thrombectomy flat‐panel CT is a useful screen post thrombectomy for high‐risk findings such as contrast extravasation and hemorrhagic transformation. Further studies are needed to determine ideal management in cases of contrast extravasation or hemorrhage on flat‐panel CT.