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This study presents a quasi- in situ observation of the fatigue crack growth behavior in a friction stir welded 2024-T4 joint. The microstructure and fatigue properties of the joint were investigated using electron backscatter diffraction (EBSD) technique, scanning electron microscopy (SEM), and fatigue crack growth tests. The fatigue crack growth behavior of the joint was examined by conducting fatigue crack growth tests with different notch locations. The results show that the sample with the notch in the stir zone (SZ) exhibited the highest resistance to fatigue crack growth, followed by the notched samples of the Advancing side (AS) and Retreating side (RS) weldments. Microstructural observations showed a homogeneous microstructure with a fine grain size in SZ and it was observed that this fine-grained structure significantly enhanced the material’s resistance to fatigue crack growth. The experimental results were further analyzed using the Paris model to provide a quantitative understanding of the crack growth behavior. The study underlines the impact of microstructural characteristics and notch location on the fatigue performance of the weldment. Overall, the quasi- in situ observations and experimental findings contribute to a comprehensive understanding of the fatigue crack growth behavior in friction stir welded 2024-T4 joints.

This study was conducted to determine the indentation behavior of thin AlSi10Mg specimens manufactured using Selective Laser Melting (SLM) in the as-built condition along with two post-treatments, namely solution heat treatment and artificial aging. Four different thicknesses of 1.0 mm, 1.5 mm, 2 mm, and 2.5 mm of SLM specimens, with the different post-treatments, underwent standardized Rockwell hardness tests using a spherical indenter to determine their hardness values and assess the impression using a stereo microscope and scanning electron microscope (SEM). The as-built specimens showed a trend of smaller indentation depths with increasing specimen thickness, and finally creased with 0.1547 mm depth at 2.5 mm. However, the post-treatments altered the behavior of the specimens to a certain degree, giving larger experimental indentation depths of 0.2204 mm, 0.1962 mm, and 0.1798 mm at 1.0 mm, 1.5 mm, and 2.5 mm thickness, respectively, after solution heat treatment. Artificial aging showed a general decrease in indentation depth with increasing specimen thickness in contrast to solution treatment, and resulted in depths of 0.1888 mm and 0.1596 mm at 1.0 mm and 2.5 mm thickness. Furthermore, a material numerical model was made using stress–strain data on ANSYS Workbench to develop a predictive model for the indentation behavior of the specimens in contrast to experimentation. Under multi-linear isotropic hardening, the Finite Element Analysis (FEA) simulation produced indentation geometry with an average accuracy of 95.4% for the artificial aging series.

Impact strength is one of the major mechanical properties that a material should possess in order to absorb sudden changes in the load intensity. The objective of current study is to compare the impact strength of two material (AU5GT and AS7G06), which are used in different structural applications. Almost no work is available which compares the impact strength of selected grade alloys along with different heat treatment cycles. Specimens are heat treated first as per designed cycles, later impact testing is performed. Charpy impact test is conducted in accordance with ASTM E23-12 standard method on three samples with and without heat treatment for each cycle. Solutionizing on samples is done at constant time and temperature to achieve homogenization. Later, aging is conducted at different temperatures ranging from 100-200°C (different intervals) at constant time to find the effect of precipitation hardness that actually increases the strength. Sample hardness is determined using Vickers micro hardness testing machine for each heat treatment cycle. Charpy test results provided the impact energy that is used to determine the strength before fracture. Heat treated samples have showed increase in impact strength for AS7G06 aluminum alloy while AU5GT shows very little change. This is because of growing the precipitation with respect to temperature, which resulted in more hard regions across grains. Hardness also shows an increasing relationship, as expected. Fracture surfaces are analyzed on stereo microscopy and Scanning electron microscopy (SEM) to find the final mode of fracture, that is brittle, ductile or transitional (combination of both brittle and ductile).

The main objective of this research was to join the CoCrNi medium-entropy allow (MEA(with SUS 304 stainless steel to obtain combinatorial properties that could be suitable for cryogenic applications. The vacuum diffusion welding process was utilized under different processing parameters. Three levels of welding temperatures and bonding time were selected, and the influences of these parameters were investigated using a full factorial design. The weld quality was assessed through ultrasonic testing to examine weld discontinuities and other defects along the weld interface region. Microstructure characterization using SEM scans were also investigated to corroborate the finding of ultrasonic scans. Based upon analysis of variance (ANOVA), the welding temperature was found to have a strong effect on the joint’s shear strength as compared to bonding time, and the interaction of the welding temperature and bonding time was found to be insignificant, while weld interface thickness revealed strong dependency on both the parameters and exhibited a strong interaction between the two parameters. Models to predict the joint’s shear strength and weld interface thickness were also developed using regression analysis. The predictability of the joint’s shear strength was more reliable with only a 7.5% error, while the error associated with the prediction of weld interface thickness was found to be 15.3%.

In this paper, two different adaptive strategies are presented for continuous time uncertain nonlinear systems with unknown disturbances and faults. In first strategy, a sliding mode control based adaptive neural observer approach is anticipated for estimation of unknown disturbances and faults by using the multi-layer perceptron, the weight parameters are updated by using the sliding mode online learning strategy. Conventionally, gradient descent back-propagation adaptation methods are used for neural networks training, within these adaptation methods a new theory of sliding mode control is added to conventional gradient descent back-propagation procedure. In this nonlinear control concept, the Sliding Mode Control is employed as a learning strategy, in which the neural network is considered as a control process and computes the stable and dynamic learning rates of neural network. By considering the unknown faults approximation and reconstruction, this online learning strategy shows a rapid sensor fault detection, approximation, and reconstruction with high preciseness and rapidness compared to conventional strategy and algorithms presented in literature. Approaches used in literature do not have much higher preciseness and fast response to fault occurrence compared to the strategy proposed in this study. In second strategy, the neural network controller strategy is proposed with concept of filtered error scheme. Online weight updating strategy comprise of additional term to back-propagation, plus an additional robustifying term, assures the stability and rapid convergence of the faulty system. The stability analysis of the proposed fault tolerance control is also provided. While considering stability of system, this robust online adaptive fault tolerance control shows a fast convergence in the presence of unknown disturbances and faults. The robust adaptive neural controller is compared with the conventional gradient descent based controller in the existence of various sensor faults and failures. The proposed strategies are validated on Boeing 747 100/200 aircraft, results show the efficiency, preciseness and robustness of strategies compared to the algorithm presented in literature.

A promising method for additive manufacturing that makes it possible to produce intricate and personalized parts is selective laser melting (SLM). However, the mechanical properties of as-corroded SLM parts are still areas of concern. This research investigates the mechanical behavior of SLM parts that are exposed to a saline environment containing a 3.5% NaCl solution for varying lengths of time. The exposure times chosen for this study were 10 days, 20 days, and 30 days. The results reveal that the tensile strength of the parts is significantly affected by the duration of exposure. Additionally, the study also examined the influence of porosity on the corrosion behavior of the parts. The analysis included studying the mass loss of the parts over time, and a regression analysis was conducted to analyze the relationship between exposure time and mass loss. In addition, the utilization of scanning electron microscopy (SEM) and X-ray photo spectroscopy (XPS) techniques yielded valuable insights into the fundamental mechanisms accountable for the observed corrosion and mechanical behavior. It was found that the presence of corrosion products (i.e., oxide layer) and pitting contributed to the degradation of the SLM parts in the saline environment. This research emphasizes the importance of considering part thickness in the design of SLM components for corrosive environments and provides insights for enhancing their performance and durability.

This study investigates the new surface development on AA6061 and AA5086 alloys considering the wire-arc additive manufacturing technique as a direct energy deposition (DED) process of wire. Two different quantities of MWCNTs, i.e., 0.01 (low) and 0.02 (high) g, with a constant nickel (Ni) weight (0.2 g) were pre-placed in the created square patterns. ER4043 filler was used as a wire for additive deposition, and an arc was generated through a tungsten inert gas (TIG) welding source. Furthermore, hardness and pin-on-disk wear-testing methods were employed to measure the changes at the surfaces with the abovementioned inducements. This work was designed to illustrate the hardness and the offered wear resistance in terms of mass loss of the AA6061 and AA5086 aluminum alloys with the function of nano-inducements. Two sliding distance values of 500 m and 600 m were selected for the wear analysis of mass loss from tracks. A maximum increase in hardness for AA6061 and AA5086 alloys was observed in the experiments, with average values of 70.76 HRB and 74.86 HRB, respectively, at a high mass content of MWCNTs. Moreover, the tribological performance of the modified surfaces improved with the addition of MWCNTs with Ni particles in a broader sense; the modified surfaces performed exceptionally well for AA5086 compared to AA6061 with 0.02 and 0.01 g additions, respectively. The system reported a maximum of 38.46% improvement in mass loss for the AA5086 alloy with 0.02 g of MWCNTs. Moreover, the morphological analysis of the developed wear tracks and the mechanism involved was carried out using scanning electron microscope (SEM) images.

The wear surface morphology of AlSi10Mg specimens, originally manufactured using selective laser melting (SLM), has been analyzed in the context of exposure to heat from gas flames. The first stage of the experimental work included the performance of surface heat-exposure on SLM-prepared specimens through oxyacetylene gas welding. Gas welding was utilized with three different flames, namely; reducing, neutral, and oxidizing on the as-built specimens of SLM. The post-surface-treated specimens were subjected to pin-on-disk wear testing against fixed parameters. After the performance of wear testing at two different radii, the mass loss of each of the four types of specimens was calculated including the three specimens exposed to heat along with the as-built specimens. The results showed that the maximum amount of mass losses at 24 mm and 30 mm radii belongs to the neutral flame specimens and the least was for the as-built condition specimens. Upon analysis, the heat-exposure specimens through all three types of gas flames resulted in an increase in the amount of mass in contrast to the as-built specimens. Moreover, the morphologies of the developed wear tracks at surfaces were examined using the scanning electron microscope (SEM) for the understating of the mechanism.

The Crimean-Congo hemorrhagic fever (CCHF) virus is a tick-borne virus that can spread from infected people and other animals, including cattle and ticks of the Hyalomma genus. People who are infected describe symptoms that range from flu-like manifestations to severe multi-organ failure. With a death rate between 10% and 30%, the virus is undoubtedly a disease of high concern. With 10,000-15,000 cases/y, it is endemic in parts of Asia, Africa, and South-Eastern Europe. There has been a recent CCHF outbreak in Iraq, with 212 cases documented, 80% of which were reported between April and May and led to 27 fatalities.

Introduction Sydenham's chorea (SC), prevalent in developing countries and occasionally affecting developed ones, poses a clinical challenge due to the lack of systematic guidelines for diagnosis and treatment. Resulting from Group A Beta‐Hemolytic Streptococcus infection, SC presents various symptoms. This review aims to collect and evaluate available data on SC management to propose a cohesive treatment plan. Methods We searched PubMed, the Cochrane Library, Google Scholar, and ClinicalTrials.gov for literature on SC management from inception until 24th July 2022. Studies were screened by titles and s. Cochrane Collaboration's Risk of Bias tool (RoB‐1) assessed Randomized Controlled Trials, while the Risk of Bias In Non‐randomized Studies of Interventions (ROBINS‐I) tool evaluated nonrandomized studies. Results The review includes 11 articles assessing 579 patients. Excluding one study with 229 patients, of the remaining 550 patients, 338 (61.5%) were females. Treatments used were dopamine antagonists in 118 patients, antiepileptics in 198, corticosteroids in 134, IVIG in 7, and PE in 8 patients. Dopamine antagonists, particularly haloperidol, were the primary treatment choice, while valproic acid (VPA) was favored among antiepileptics. Prednisolone, a corticosteroid, showed promising results with weight gain as the only side‐effect. Our review emphasizes the importance of immunomodulators in SC, contrasting previous literature. Conclusion Despite limitations, dopamine antagonists can serve as first‐line agents in SC management, followed by antiepileptics. The role of immunomodulators warrants further investigation for conclusive recommendations.