Thin Wall Research Articles

Congenital Apical Left Ventricular Aneurysm.

A 17-year-old male was referred for evaluation by Pediatric Cardiology following a pre-sports medical screening, which revealed abnormal ventricular repolarization (negative T wave from V3-V6) on a 12-lead ECG. For 8 years, he has been a competitive football player. There was no relevant personal or family medical history, and he denied any prior cardiovascular symptoms. His cardiovascular physical examination was normal. In the initial assessment, a transthoracic echocardiogram was conducted, revealing an apical aneurysm of the left ventricle (LV) with regional dyskinesia, accompanied by mild mitral regurgitation. The examination also demonstrated globally preserved left ventricular systolic function, with no images suggestive of vegetations or intracardiac thrombi found. For further anatomical and myocardial characterization, a cardiac magnetic resonance (CMR) was performed. The results revealed a wide apical aneurysm of the LV, predominantly lateral, with thin walls, ridges within the outpouching, and local dyskinesia. No areas of late gadolinium enhancement (LGE) were found, suggestive of fibrosis, anomalous infiltration, or scar from a previous infarction. After excluding other etiologies, the diagnosis of a congenital ventricular aneurysm was determined. This is a very rare condition (0.12%) with a wide and variable clinical presentation, ranging from benign arrhythmias to sudden death. Various imaging techniques aid in its diagnosis, with CMR being particularly useful for excluding inflammation and cardiomyopathies, identifying LGE, and evaluating left ventricular volumes and function. There is no standard treatment, and controversy surrounds indications for surgical intervention. If a conservative approach is adopted, measures aimed at preventing endocarditis and embolism must be considered.

A novel and promising thermal insulation material: Monazite-type porous LaPO4 ceramics possessing ultra-low thermal conductivity and enhanced strength

In this study, novel porous LaPO4 ceramics possessing closed spherical pores and thin pore walls have been firstly synthesized using the particle-stabilized foaming method. Affected by the calcination temperature together with solid loading, the obtained porous LaPO4 ceramics exhibit high porosity (81.69–94.21 %), very low thermal conductivity (κ) (0.124–0.398 W m−1 K−1) and relatively high compressive strength (0.886–9.30 MPa). When the calcination temperature and solid loading are 1500 °C and 35 wt%, optimized porous LaPO4 ceramics achieve a better balance between thermal conductivity (0.160 W m−1 K−1) and compressive strength (2.07 MPa). Based on this, the prediction model for the thermal conductivity is screened and the thermal insulating capability is further verified. This work suggests that porous LaPO4 ceramics have the potential to be applied as thermal insulation material in the future.

Evaluating the effect of different diaphragm wall cracking scenarios on seepage and slope stability in Earth dams using experimental and numerical modeling approaches

BackgroundSeepage control measures are essential in earth dams to enhance their safety against seepage and slope failures. A diaphragm is a thin impervious wall that is used in the core area of the dam to prevent the seepage of water. Any crack in the diaphragm can reduce its efficiency and threaten the safety and stability of the dam. Extensive evaluation of the influence of diaphragm fracturing on dam safety is required to establish a safe design and offer the appropriate measures. This study investigates the effect of diaphragm cracking on the safety of the dam for seepage and slope stability. A permeability tank is first used to validate the numerical model; then, different scenarios for cracked diaphragm walls are studied numerically. The crack’s height, width, direction, and number are all investigated. The effect of having a downstream horizontal blanket drain with cracked internal diaphragms is also evaluated.ResultsThe results showed that the internal diaphragm enhances the safety of earth dams as it reduced the seepage discharge by 98% and increased the downstream slope safety by 34%. Considering the development of a crack in the internal diaphragm, the most critical location was at the base of the dam, wider cracks were more destructive, and the most critical direction was the horizontal crack. The fracturing of the diaphragm at multiple locations proved to be detrimental to the safety of the dam. Having three cracks caused the seepage discharge to reach 74% of its value for no diaphragm, the pore water pressure to raise drastically, and the downstream critical factor of safety to be higher than the case of no diaphragm by 8% only.ConclusionsAccording to the findings, it is advised to continuously monitor the components of diaphragm-type earth dams and perform the necessary maintenance works whenever any sign of damage or water seepage appears. Furthermore, using a well-graded horizontal drain of sufficient length and high permeability with the internal diaphragm is highly recommended as a mitigation measure if diaphragm fracturing occurs. This helps to quickly release the seeping water and keep the phreatic line away from the downstream slope.Graphical abstract

A Methodology for Shielding-Gas Selection in Wire Arc Additive Manufacturing with Stainless Steel.

The main objective of this work was to propose and evaluate a methodology for shielding-gas selection in additive manufacturing assisted by wire arc additive manufacturing (WAAM) with an austenitic stainless steel as feedstock. To validate the proposed methodology, the impact of multi-component gases was valued using three different Ar-based blends recommended as shielding gas for GMA (gas metal arc) of the target material, using CMT (cold metal transfer) as the process version. This assessment considered features that potentially affect the building of the case study of thin walls, such as metal transfer regularity, deposition time, and geometrical and metallurgical characteristics. Different settings of wire-feed speeds were conceived to maintain a similar mean current (first constraint for comparison's sake) among the three gas blends. This approach implied different mean wire-feed speeds and simultaneously forced a change in the deposition speed to maintain the same amount of material deposited per unit of length (second comparison constraint). The composition of the gases affects the operational performance of the shielding gases. It was concluded that by following this methodology, shielding-gas selection decision-making is possible based on the perceived characteristics of the different commercial blends.

Tumor Cells and Microenvironmental Interaction in Natural Course of Canine Transmissible Venereal Tumor

Canine transmissible venereal tumors (CTVT) is a naturally occurring tumor that is mostly transmitted between dogs through coitus. This study aims to investigate the effect of CTVT on molecular expression and disease progression by studying the tumor microenvironment (TME). For this purpose, biopsy samples taken from ten female dogs were evaluated histopathologically and CTVT was diagnosed. The expression of markers such as CD163, CD68, CD44, TGF-beta and bFGF was evaluated by immunoperoxidase tests. Histopathologically, CTVT cells exhibited pleomorphism, ranging from round to polygonal. Some cells exhibited prominent vacuoles and hypochromatic nuclei, while others exhibited hyperchromatic nuclei containing mitotic figures within the thin fibrovascular wall. Immunohistochemically, TGF-beta and CD44 expression was higher in CTVT cells compared to CD68 and bFGF, while bFGF expression was higher in fibrocytes and spindle cells compared to other markers. The results indicate that CD44 and TGF-beta may play a pivotal role in fibrovascular processes, CD163 and CD68 may facilitate interactions between stromal components and mesenchymal cells, and bFGF, TGF-beta and CD68 may contribute to the arrest of tumoral progression and the initiation of the regression phase. These findings underscore the necessity for further studies to elucidate the role of markers at different stages of CTVT progression.

Not All Patients with a Headache need a CT Scan, but they should be Listened to, and also with a Stethoscope: A Report of a Large Arteriovenous Malformation with a Loud Cranial Bruit.

Arteriovenous malformations (AVMs) are abnormal direct connections between arterial and venous systems, without an interposed capillary bed. This permits high-flow arteriovenous shunting, which precipitates structural changes in the afferent and efferent vessels, namely arterial smooth muscle hyperplasia and thinning of venous walls. Patients with intracranial AVMs typically present with a haemorrhage, headache or seizure. Treatment is either via medical management aimed at control of seizures, headache and blood pressure, or interventional via surgical, radiation or radiologically guided embolisation. We report the case of a woman in her early 40s presenting with a tonic-clonic seizure against a background of a 31-year history of migraine and an 18-month history of tremors in her right arm. The clinical examination was remarkable for an extremely loud cranial bruit and a right homonymous hemianopia. Imaging diagnosed an 8 cm Martin-Spetzler grade V intracranial arteriovenous malformation in her left parietal lobe, which was deemed unsuitable for operative or radiotherapy-based intervention. The patient was managed through observation and relatively good control of her breakthrough seizures was achieved through the addition of brivaracetam to her lamotrigine and carbamazepine-based therapy, six years after her initial presentation. Arteriovenous malformations may go undetected for decades.The presence of a cranial bruit is an important sign and tool in diagnosing an intracranial arteriovenous malformation. The presence of a homonymous hemianopia, of which a patient may be unaware, helps to localise an intracranial lesion.The risks of operative or radiological intervention must be balanced with the risks of haemorrhage or refractory seizure when adopting a strategy for the treatment of an intracranial arteriovenous malformation. Good control of epileptic symptoms in those deemed not suitable for operative or radiological intervention can be achieved by careful titration of anti-seizure medications.

Development of CNN-based sub-sonic speed vehicle body frame micro damage assessment technology using guided wave spectrogram images

Due to advancements in diagnostic technology, sub-sonic speed trains are subjected to significant fatigue stress on their bodies. This phenomenon can be considered a menace, leading to significant accidents on railways due to the tiny size of defects on the train bodies. In this research, a deep learning approach is employed to identify the initial damage status. The goal is to develop an evaluation technique for verifying an initial wall-thinning crack using frequency spectrogram images. The wall-thinning effects of 6.3 mm thick aluminum AL-2024 T6 plates, primarily used in frames and bodies, are confirmed through the frequency responses of guided waves. To verify the effects of wall thinning, both higher-order harmonic frequencies of guided waves and nonlinear ultrasonic techniques are simultaneously used. To identify the tendency of frequency response, frequency spectrogram images, illustrated by short-time Fourier transforming analysis, are chosen. For training the detection system using the Region-based Convolutional Neural Network (R-CNN), spectrogram images are generated for wall-thinning steps with an increment of 0.2 mm (3% of the total thickness). The ResNet-50 is employed in the convolutional layer of the R-CNN engine to address the issue of gradient vanishing. The results of this research indicate that the depth of wall thinning in the plates can be identified. Based on the R-CNN training set, the initial wall-thinning failure can be verified with reliable accuracy.

Study on rotary bending fatigue performance of TC4 lattice structure fabricated by selective laser melting

Prediction of the fatigue performance of lattice structures in additive manufacturing still lacks widely applicable methods. To address this issue, we investigated the effect of a BCC lattice structure combined with thin walls and ribs on the fatigue performance of TC4 alloy samples. The lattice-structured samples were fabricated by selective laser melting. In addition, we proposed a prediction model of fatigue performance that combined ABAQUS finite element analysis with FE-safe fatigue analysis. The simulation and experimental results verified the reliability of the model. Based on this method, the effects of lattice and ribbed plate structures on the bending fatigue performance were investigated. The experimental results showed that the stress concentration generated by lattice structures weakened the fatigue performance. On the contrary, ribbed plates can enhance fatigue performance, which also depends on the orientation of the rib structure. The simulation results showed that increasing the volume fraction of unit cells can mitigate the stress concentration, leading to improved fatigue performance. The lattice structure combined with the rib structure exhibited superior fatigue performance. In addition, the proposed models can also be applied to other metallic materials. The findings in this study can provide a theoretical basis for the design of lattice structures with better fatigue performance.

Optimizing the compression resistance of low-nickel stainless steel coronary stents using finite element and response surface methodology

Considering the high strength and excellent biocompatibility of low-nickel stainless steel, this paper focused on optimizing the design of a vascular stent made from this material using finite element analysis (FEA) combined with the response surface methodology (RSM). The aim is to achieve the desired compressive resistance for the stent while maintaining a thin stent wall thickness. The parameters of the stent’s support unit width (H), strut width (W), and thickness (T) were selected as input parameters, while the output parameters obtained from FEA included the compressive load, the equivalent plastic strain (PEEQ), axial shortening rate, radial recoil rate, and metal coverage rate. The mathematical models of input parameters and output parameters were established by using the Box Behnken design (BBD) of RSM. The model equations were solved under constrained conditions, and the optimal structural parameters, namely H, W, and T, were finally determined as 0.770 mm, 0.100 mm, and 0.075 mm respectively. In this situation, the compression load of the stent reached the target value of 0.38 N/mm; the PEEQ resulting from the stent expansion was small; the axial shortening, radial recoil, and metal coverage index were all minimized within the required range.

Manufacturing and performances of MnZn ferrite cores with thin walls prepared by paste material extrusion 3D printing

The 3D printing technique using material extrusion of a paste filled with ferrite powder (Mn,Zn)Fe2O4 and organic additives has been successfully improved to produce sintered samples for studying their magnetic and structural properties. The rheological behaviour of the pastes and the printing parameters have been optimised to obtain parts with regular geometries, in particular by minimising sagging effect during filament deposition. Printing is followed by a debinding and sintering stage, for which the temperature and oxygen partial pressure conditions were adjusted. These conditions enable the densification of the (Mn,Zn)Fe2O4 material in the spinel structure without parasitic phases, with a low grain size dispersion and a relative density of 91 %. The core loss has been measured on the 3D printed samples to be 144 mW/cm3 at a frequency of 500 kHz and an induction of 50 mT. This performance is comparable to the nominal value of a part produced by the conventional process. This work paves the way for an advantageous manufacturing method in terms of accessible geometries, while maintaining satisfactory magnetic characteristics.

Additive Manufacturing Process Simulation of Laser Powder Bed Fusion and Benchmarks

As the aerospace industry continues to adopt additively manufactured (AM) parts for flight hardware, process simulation becomes more attractive to improve the manufacturing process by understanding how process parameters affect part quality and performance. Process simulation can also be used to predict and prevent build failures before the printing process. The powder bed fusion process of Ti-6Al-4V material is modeled using commercial finite element software to simulate the selective laser melting process. The thermal history is obtained from transient heat transfer analysis. Both the inherent strain approach and a sequential thermal-mechanical approach are employed to predict residual stress and part distortion. A National Agency for Finite Element Methods and Standards (NAFEMS) benchmark problem is presented as a numerical example. It is a thin wall structure with geometry features that can lead to part defects due to thermal distortion. It is shown that both analysis approaches are able to capture the thin-member bridging behavior, stepping behavior, and general distortion contour plot as those published by NAFEMS.

Doping P heteroatoms into thin-wall polypyrrole hollow nanobelts with enhanced electrochemical performance for aqueous Zn ion storage

The aqueous zinc-ion batteries are promising to be large-scale energy technologies for solving the contradiction between the intermittency of renewable energy and the immediacy of growing electricity demand. Conductive polymers have been utilized as cathode materials for Zn ion storage but suffered from inadequate active sites, resulting in poor specific capacity. In this work, P doping polypyrrole hollow nanobelts (P-PPy HNBs) with long aspect ratio have been prepared by in-situ polymerization of pyrrole on a template of MoO3 nanotubes. Owing to the long-aspect-ratio hollow structure, the P-PPy HNBs perform thin wall, large surface area, porous structure with micropores and mesopores, which is beneficial to high and fast Zn ion storage. Remarkably, the as-obtained P-PPy HNBs cathodes in this work deliver favorable electrochemical performance for Zn2+ storage in terms of good capacity, rate capability and cycling stability. Moreover, kinetic analysis quantitatively confirms the capacitive contribution of NPCNTs is dominant for aqueous Zn ion storage. The capacitive properties are contributed that the synergistic effect of porous and hollow nanobelt structure construction and P doping strategy can provide abundant active sites and promote electronic conductivity and ion transport. Generally, the strategy for hollow structure with a long aspect ratio and heteroatom doping in our work causes excellent-performance properties, possibly bringing light on the future design of other cathodes for aqueous Znic-based energy storage devices.

Mechanisms of Medial Wall Thinning in Chronic Total Occlusion

BackgroundThe success rate of percutaneous coronary intervention (PCI) for chronic total occlusion (CTO) is lower and the risk for complications higher compared with other non-CTO PCI. Although interventionalists focus on intimal plaque characteristics, the coronary media is an important (especially for techniques involving antegrade dissection and re-entry) but poorly understood structure in CTO PCI. ObjectivesThe aim of the present study was to investigate coronary medial wall thinning in CTO lesions and determine how this thinning might affect CTO PCI. MethodsA total of 2,586 sections were investigated, from arteries with evidence of CTO from 54 subjects (1,383 sections) and arteries without evidence of CTO from 54 subjects with non-coronary-related deaths (1,203 sections) after matching for age, gender, body weight, and body height. ResultsThe medial thickness in subjects with CTO was lower than that in those with non-coronary-related death (P < 0.001). In subjects with CTO, CTO lesions had thinner medial walls compared with those with lower luminal narrowing (P < 0.001). At the CTO distal segments, the 6- to 12-mm distal segment from the distal end of the CTO had significantly less luminal narrowing (P < 0.001), and similar medial thickness, compared with the distal end of the CTO. Immunohistochemical analysis revealed that short-duration CTO had more cleaved caspase-3–positive cells in media and had significantly more CD3+, CD4+, CD8+, and CD4+CD28null T cells compared with long-duration CTO. ConclusionsCTO lesions demonstrated coronary medial thinning compared with non-CTO lesions. Further investigation of the cause-and-effect relationship among inflammation, apoptosis, and coronary medial wall thinning is warranted in future mechanistic studies.

Insight into the influence of part in cattails on electrochemical performance of the porous carbon for Zn-ion storage

Recently, biomass-derived porous carbon has gained popularity as a cathode material for Zn-ion hybrid supercapacitor (ZIHSs) due to its unique structure and heteroatoms. However, the understanding of how biomass part affects resulting carbon structure and ZIHSs performance is limited. This study utilizes cattail leaves (CLs), cattail wools (CWs), and cattail stems (CSs) as carbon sources, with each impacting carbon microstructure, morphology, specific surface area (SSA), and oxygen content. CLs-based porous carbon (CLPC) exhibits a distinct hollow tube structure with thinner walls, high oxygen content, and a large SSA, which are crucial for enhanced electrochemical performance. The aqueous Zn//CLPC ZIHSs demonstrate remarkable energy density (190 Wh kg−1), specific capacity (253 mAh/g at 0.1 A/g), and cycle life (91% capacity retention over 10,000 cycles at 10 A/g). Electrochemical processes are studied through various techniques, shedding light on the relationship between cattail parts, carbon structure, and ZIHSs performance, aiding in more efficient biomass utilization.

Conforming mesh modeling of multi-physics effect on residual stress in multi-layer powder bed fusion process

The current research aims to predict the residual stress accumulation and evolution in the powder bed fusion processed multi-layer thin wall structures through a conforming mesh modeling approach. It involves the discrete element method (DEM) interfaced with the volume of fluid (VOF) method using computational fluid dynamics (CFD) coupled with the finite element method (FEM). The conforming mesh approach developed in the research predicts multi-physics, its induced porosity, and the cumulative effect on the residual stress in the powder bed fusion processed Ti-6Al-4V thin wall structures. The results of the residual stress in the multi-layered component from this method were further quantitatively compared with the non-conforming finite element method. The results show the conforming mesh approach was not only effective in capturing the layer geometry, and defects induced during the printing, but also predicted the residual stress in the region of the defect more accurately than the non-conforming mesh methods.

Підсилення ділянки трубопроводу АЕС з дефектом стоншення стінки при встановленні зварної латки

Підсилення ділянки трубопроводу АЕС з дефектом стоншення стінки при встановленні зварної латки

Buckling resistance of ultra-low-density carbon fiber curved-wall honeycomb based on stretching process

Although honeycomb is a kind of lightweight structural material with great potential, its specific strength is not always able to meet the requirements, especially in the weight-sensitive field. Inspired by the bionic idea of cuttlebone, the curved-wall configuration design is proposed to strengthen the buckling impedance of honeycomb, which can effectively prevent the premature occurrence of buckling failure mode induced by thin walls. Compared with the straight-wall honeycomb materials of the same geometric size, the probability of buckling failure in curved-wall honeycomb materials proposed in this paper is reduced by more than 22 %. Moreover, to achieve the preparation of curved-wall configuration, a processing strategy that uses stretching process to prepare ultralight carbon fiber honeycomb (Carbcomb) material is firstly introduced. Compared to the Hexcel Corporation’s aluminum honeycomb with a density of 21 kg/m3, for the Carbcomb, the specific compressive strength and specific shear strength along both the L and W directions respectively improved by 57 %, 61 % and 77 %. In addition, the minimum density of fabricated Carbcomb (14.6 kg/m3) is less than that of the Hexcel's products (16 kg/m3), and the research findings fill the gap of the carbon fiber honeycomb material in low density areas (10 ∼ 30 kg/m3). More importantly, this process which does not require much manual operation can effectively avoid the problems of unstable mechanical properties, difficult mass production and high preparation cost of the existing carbon fiber structural parts. This curved-wall configuration design and fabricated approach widens the potential of carbon fiber honeycomb as a structural material, and makes it possible for lower cost and higher efficiency in aerospace and transportation applications.

Preparation of SiO2 nanotubes and nanoparticles in the presence of L-tartaric acid by sol-gel method and their electrochemical performance for Li-ion batteries

Recently, SiO2 has attracted increasing attention as an anode material for lithium-ion batteries (LIBs) owing to its low cost and high theoretical specific capacity. However, its inherent poor conductivity limits its practical application. To address this issue, nanostructured material design is considered an effective solution. Herein, based on the traditional ammonium tartrate template-directed sol-gel method, we use low-cost and easily available L-tartaric acid in place of D, L-tartaric acid to prepare high-yield silica nanotubes (SNTs) with a thin wall (ca. 50 nm), small diameter (ca. 150 nm), rough surface and open ends, as well as tiny spongy-like silica nanoparticles (SNPs) by adjusting the feeding amount and feeding mode of NH4OH solution. The electrochemical characterization results suggest that the SNTs show better cyclability and rate performance than the SNPs, which maintain a reversible capacity of 741.3 mAh g−1 after 500 cycles at a current density of 0.4 A g−1 and deliver a high rate capacity of 819.4 mAh g−1 at a high current rate of 2 A g−1. The excellent electrochemical performance suggests that hollow one-dimensional hollow nanotubes are more efficient in improving the electrochemical performance of SiO2 than zero-dimensional nanoparticles, and SNTs with thin tube walls and rough surfaces are demonstrated to be fascinating and promising anode materials for LIBs.

Experimental Study on the Current Pretreatment-Assisted Free Bulging of 304 Stainless Steel Sheets

In order to further improve the microplastic deformation ability and forming performance of metal sheets, a pulse current pretreatment-assisted micro-forming method was proposed. Firstly, a 304 stainless steel sheet was pretreated with current (0–25 A), and the microstructure changes in the sheet under the action of current were analyzed. Then, a current-assisted bulging experiment was carried out from three aspects as follows: current size, mold structure size, and material properties, to explore the influence of different process parameters on the micro-bulging of the sheet. Finally, the forming quality was analyzed and evaluated from the two perspectives of bulging depth and wall thickness uniformity. The research results show that when the current intensity increases from 0 to 25 A, the fibrous distribution in the thickness direction of the sheet is alleviated, the structure is more uniform, the bulging depth shows an increasing trend, and the thinning rate and wall thickness uniformity are improved. When the current intensity reaches 25 A, the bulging depth increases from the original 463 μm to 503 μm, and the thinning rate drops from the most serious 48.52% to 19.4%. At the same time, as the mold size increases, the single-channel aspect ratio (W/H) also increases accordingly. When the mold groove width (W) is 2 mm, the ratio reaches 0.4, the sheet deforms significantly, and the filling effect is better. In addition, the larger the roundness of the convex and concave molds, the more uniform the wall thickness distribution of the bulging parts. Under the same experimental conditions, the bulging depth of the 304 stainless steel sheet is higher than that of TC4 titanium alloy, and it is less prone to springback and is more conducive to plastic deformation.

Laser melting deposition of Mn–Cu-based alloy: Microstructure, mechanical properties and damping capacities

Mn–Cu-based alloys are promising structural materials for noise and vibration reduction, and Mn–Cu-based alloys with medium Mn content offer significant advantages in formability and corrosion resistance. The preparation of Mn–Cu-based alloys using traditional processes has disadvantages such as the ease of defects and long preparation cycles. Laser melting deposition was employed to fabricate the Mn-36.53Cu-4.30Al-3.07Fe-2.46Ni-0.64Zn (wt. %) alloy thin wall sample, and the microstructure, mechanical characteristics, and damping capacity of the as-deposited samples were investigated. The microstructure of the as-deposited alloy revealed randomly dispersed fine γ-(Mn, Cu) dendrites and a small quantity of α-Mn phase across different sections. The as-deposited samples along the scanning direction (AD-S) exhibited an ultimate tensile strength (UTS) of 584 ± 6 MPa, while those along the deposition direction (AD-D) showed a UTS of 578 ± 6 MPa. The elongation of AD-S samples measured at 40 ± 0 %, and for AD-D samples, it was 31 ± 1 %. At ambient temperature, the as-deposited alloy displayed high damping properties with a frequency of 1 Hz and a strain amplitude ranging from 30 to 100 × 10−6. The findings contribute to the practical applications of Mn–Cu-based alloys, particularly those with a medium Mn concentration.