Operational Life Research Articles

H‐Bonded Amorphous Polymer Glass Nanofibers with Simultaneously Large Enhancement in Strength, Toughness, Ductility, and Thermal Stability

AbstractUnderstanding the direct effects of hydrogen bonding (H‐bonding) on the mechanical response of glassy state polymers remains a challenge, largely owing to the use of semicrystalline polymers in such studies, wherein, separating the contributions due to the changes in degree of crystallinity and direct H‐bonding effects on the observed mechanical properties is extremely difficult. This limitation is overcome by studying the mechanical behavior of amorphous, glassy polyvinylpyrrolidone (PVP), H‐bonded with tannic acid (TA). Uniaxial tension experiments on individual submicron scale PVP fibers (0.6–1.0 µm diameters) with different TA concentrations are conducted to capture their elasto‐plastic deformation characteristics. Amorphous PVP‐TA complexes exhibited some distinctive trends in elasto‐plastic properties with increasing H‐bond density, which are not observed earlier. These distinctive trends are discussed in terms of the competing effects of H‐bond driven crosslinking and TA‐induced reduction in entanglement density, and their differing roles during elastic and plastic deformation. The improvements in elasto‐plastic properties (particularly ductility and toughness) are simultaneously accompanied by uniquely significant thermal stability (i.e., glass transition temperature, Tg) improvements, that can help improve the practical applicability, operational life, and performance of these materials.

Implementation of a modified Graham-Walles viscosity function within a Chaboche viscoplastic constitutive model

This work provides a numerical framework for the accurate prediction of operational life of metallic components exhibiting a non-classical creep behavior under constant loadings and very high temperature. A modified Graham-Walles type analytical viscoplastic function is implemented into a Chaboche unified viscoplastic constitutive model. The numerical model is integrated into the finite element software Lagamine following a fully-implicit two-step radial return mapping algorithm. The non-linear system of equations is solved using a robust Newton-Raphson method. The computational efficiency of the model is enhanced by implementing a sub-step routine, thereby decreasing the average number of iterations of the finite element software. The validation of the model is performed using experimental data available in the literature on the non-classical creep behavior of Incoloy 800H, a Ni-superalloy exhibiting a two-step creep strain rate minima attributed to multiple complex dislocation-precipitate interactions.

Physical-mechanical Properties and Morphology of Lignocellulose Powder Modifiers for Vulcanized Rubbers

Powder lignocellulose modifiers for vulcanized rubbers were prepared from secondary paper resources (recycled cardboard) treated with TiCl4 in hexane. The diffraction patterns, IR spectra, and morphological characteristics of the materials obtained, including the geometric characteristics and length distribution of fibers, were analyzed. The content of titanium, lignin, and carbonyl and carboxyl groups and the bulk density of the material were determined. The presence of up to 5 wt parts of powder modifiers per 100 wt parts of rubber in the rubber stock favors preservation of physicomechanical properties of vulcanized rubbers both before and after accelerated thermal oxidative aging at 100°C for 72 h, enhancing the resin–metal cord adhesion and thus prolonging the operation life of the vulcanized rubbers.

METHODOLOGY OF THE RATIONALE OF AN AMOUNT OF UNMANNED CARGO DELIVERY SYSTEMS

It is possible to reduce human losses during the cargo delivery to units on the battlefield with the use of unmanned systems (UMSs), including logistical unmanned ground vehicles (UGV) of various groups carrying capacity and unmanned aircraft systems (UAS). The urgent task is to determine the required number of unmanned cargo delivery systems in the interests of the mechanized infantry battalion. The method of determining the number of unmanned cargo delivery systems for the logistical means (LM) transportation to the units of the mechanized infantry battalion is described. The optimality criterion of the selected composition of the system is the maximum efficiency-cost ratio (ECR) under the condition of transporting the maximum weight of LM required for the battle day from the combat supply point to the units of the mechanized infantry battalion. In this case, the efficiency indicator is the share of the total weight of LM that must be delivered to the units. In order to calculate this indicator, it is necessary to estimate the probability of successful delivery of LM to different battalion units for each UMSs. The cost indicator is the product of the masses of the cargo and energy costs on the delivery route, purchase costs and total costs for operating the UMSs during the forecasted average life of operation in terms of 1 kg of cargo. Two transport tables are built based on the results of the calculations. The first table includes probability weighting factors, and the second includes weighting factors of the cost of delivering LM from a combat supply point to units by various UMSs. For each of these transport problems, the optimal solution is obtained by linear programming methods, and for the ECR, by methods of optimization of problems with a nonlinear objective function, which is illustrated by an example using the "Solver" add-on in the Excel spreadsheet processor. Keywords: logistic support, unmanned systems, logistical unmanned ground vehicles, unmanned aircraft systems, load capacity, cargo delivery, efficiency-cost, optimization of an amount.

Dna forensic data bank, facts and perception: The Italian experience

In 2016 the Italian National Dna database for forensic purposes finally went live. After seven years of “operational life”, numbers and results are still scarce. The aim of the study is to evaluate the actual knowledge and perceived usefulness of this investigative tool among a significant sample of Italian magistrates. The research was conducted through the administration of an anonymous structured questionnaire to magistrates belonging to the Court of Milano. The overall picture emerging from the questionnaire is a worrying lack of preparation regarding the functioning of the Dna database among judges and public prosecutors. This situation affects the performance of the instrument. The authors believe that a specific and compulsory training for magistrates should be introduced.

Direct Numerical Simulation of Transitional and Turbulent Flows Over Multi-Scale Surface Roughness—Part II: The Effect of Roughness on the Performance of a High-Pressure Turbine Blade

Abstract Turbine blades generally present surface roughness introduced in the manufacturing process or caused by in-service degradation, which can have a significant impact on aero-thermal performance. A better understanding of the fundamental physical mechanisms arising from the interaction between the roughness and the turbine flow at engine-relevant conditions can provide insights for the design of blades with improved efficiency and longer operational life. To this end, a high-fidelity numerical framework combining a well-validated solver for direct numerical simulation and a second-order accurate immersed boundary method is employed to predict roughness-induced aero-thermal effects on an LS89 high-pressure turbine (HPT) blade at engine-relevant conditions. Different amplitudes and distributions of surface roughness are investigated and a reference smooth-blade simulation under the same flow conditions is conducted for comparison. Roughness of increasing amplitude progressively shifts the blade suction side boundary layer transition upstream, producing larger values of the turbulent kinetic energy and higher total wake losses. The on-surface data-capturing capabilities of the numerical framework provide direct measurements of the heat flux and the skin friction coefficient, hence offering quantitative information between the surface topology and engineering-relevant performance parameters. This work may provide a benchmark for future numerical studies of turbomachinery flows with roughness.

Novel method for evaluation of stress assisted corrosion through compact tension specimens to assess material compatibility in latent heat thermal energy storage systems

The next generation Concentrated Solar Power (CSP) plants integrated with Thermal Energy Storage (TES) offer a promising solution for dispatchability, reliability, and economic concerns associated with renewable energy technologies. However, the expected operational life of up to 30 years proves to be a major challenge due to the impact of high temperatures and corrosive eutectic salts utilised in the latent heat TES systems. Additionally, the system is under varying degrees of stress that can accelerate corrosion mechanisms. Unfortunately, this stress corrosion relationship is often neglected during the material compatibility assessment. This study utilises a novel static immersion testing approach with three designs of modified Compact Tension (CT) specimens manufactured from AISI 316L to investigate the interaction of alloys under stress with various eutectic salts at up to 750 °C for up to 1000 Hours. The results indicate that oxidation is accelerated up to four times and Intergranular Corrosion (IGC) up to two times in the high-stress region of the test samples. Furthermore, the findings suggest that static immersion testing using CT specimens can be regarded as an effective approach to assess the influence of stress on corrosion and conduct a reliable material assessment for latent heat TES systems and CSP plants.

Enhanced Heat Transfer Analysis on MHD Hybrid Nanofluid Flow Over a Porous Stretching Surface: An Application to Aerospace Features

The advancement of aircraft technology has presented manufacturers with new criteria and problems for the functioning of their devices. It is essential that, in order to guarantee the secure operation of aerospace machinery, the failure mechanisms be identified and the operational durability of critical structural components be improved as quickly as possible. New aviation materials have been developed in modern years. In an aviation engine, engine oil lubricates, cools, washes, maintains against rust, decreases sound, and accelerates. Most important is lubrication. All mechanical components would burn out if not maintained. The aim of this work is to minimize costs by extending the operational life of aircraft components (mechanical and motor parts) and enhancing fuel mileage and flying distance. Based on the importance of the inspiration on magnetohydrodynamic Aluminum Oxide-Cobalt hybrid nanofluid flow over a stretching surface (SS) in the existence of porous medium, and thermal radiation are investigated. In this model we used Engine oil mixed with Aluminum Oxide and Cobalt nanoparticles. By using the suitable self-similarity variables, the PDE is transformed into ODEs. After then, the dimensionless equations are solved by using the Maple built in BVP Midrich scheme. Graphs and tables explain how the operational factors affect fluid flow efficiency. Compared to nanofluids, hybrid nanofluids have a better heat transfer rate.

Decommissioning fund evaluation considering a multiple reactor site

In the next future, several nuclear power plants would reach the end of operational life. Most of them are being evaluated for long-term operation, while the remaining should be permanently shut down. For these ones, it should exist a decommissioning fund large enough to cost the project. Since some plants delay to start to collect provisions for the decommissioning fund, there is an elevated risk of lack of funds. The present work aims to evaluate the evolution of the decommissioning fund and when, or if, the lack of funds occurs considering a hypothetical multiple reactor site. The Brazilian site was taken as benchmark for this hypothetical site. Scenarios addressing normal operation, long-term operation and premature shutdown were evaluated. The decommissioning costs were estimated according to the multiple reactor approach. The novelty of the present work relies on the evaluation of the adequacy of decommissioning fund against the cost estimation performed. It was found that the lack of funds occurs in some scenarios evaluated for the oldest plant and when it could not operate in the long term, as well as, for the newest plant, if required to shut it down prematurely after a very brief operating time.

Ensuring Irradiation Conditions for Metal Specimens within a Materials Science Assembly to Validate the BN-600 Operational Life Extension

Ensuring Irradiation Conditions for Metal Specimens within a Materials Science Assembly to Validate the BN-600 Operational Life Extension

Prediction on the wear rate of epoxy composites reinforced micro-filler of the natural material residue using Taguchi – neural network

The abrasive wear rate of epoxy composites reinforced with fillers sourced from recycled natural waste consisting of pollen of palm (PPW) and seashells (SSW) was studied.
 Due to the importance of polymer composites used in the tribological couplings of machinery structures, as well as their possible use in brake pads as alternative materials for harmful components in environmentally polluted asbestos, the current research seeks to develop the tribological properties of composite materials reinforced with natural fillers and environmentally friendly. The research investigated the effect of two factors, the weight percentage of natural filler wt. % (0.5 %,1 %, and 1.5 %) and testing loads (1000 g, 2000 g, 3000 g) upon the wear resistance of epoxy composites. The importance of developing epoxy compounds is evident, especially since their work does not require lubricating conditions in various industrial fields, and therefore the development of their bonding properties will increase their operational life and achieve economic benefit for the industrial sector and the environment at the same time. The epoxy composites were subjected to abrasive wear tests under dry friction conditions using a pin-on-disc system. Signal-to-noise (S/N) analysis is adopted to study the influence of the two factors, wt. % and test loads, upon the tribological wear resistance of epoxy composites. A predictive model depending on the regression equation was developed to predict the wear resistance of epoxy composites. The results showed an improvement in the wear resistance of the composite material compared to the epoxy sample without filling by about 47 %. The optimum condition for wear resistance of epoxy composites has been achieved with a weight ratio of (1.5 %) and an applied load of 1000 g

Fatigue constrained topology optimization for the jacket support structure of offshore wind turbine under the dynamic load

This paper proposes a topology optimization method considering fatigue constraints for the jacket support structure of offshore wind turbine. Jacket support structure is an important component and supports the whole wind turbine weight under the dynamic environmental loads, which would induce serious fatigue problems. To obtain the optimal structural layout, the topology optimization method considering fatigue constrained is introduced for the jacket support structure under the dynamic load. The fatigue lifetime is constrained base on the Miner's cumulative damage rule. The design sensitivity of the objective and constraint functions are evaluated analytically, while the equivalent static load approach is applied. Some typical topology optimization problems are introduced to verify the effectiveness of the proposed method, and this method can obtain the appropriate layouts with stable convergence. A case study on the OC4 reference jacket indicates that the method can achieve a reasonable layout structure under the dynamic load, which meets the fatigue constraint. And the final design is reconstructed based on the topology optimization layout. Finally, a lighter jacket structure has good performance on the ultimate bearing capacity, eigenfrequency, and buckling, which is suited for long operation life.

Review on Thermal Analysis of LED Heat Power Dissipation and Efficiency Analysis.

Abstract: Light Emitting Diodes (LEDs) have become increasingly popular in a variety of lighting and display applications because of their extended lifespan and energy efficiency. Nonetheless, maintaining LED performance and increasing their operational life depend heavily on effective heat management. In order to gain a better understanding of the heat power dissipation and efficiency of LEDs, this study focuses on their thermal analysis. The study evaluates the heat generation and dissipation in LEDs using a variety of techniques, such as thermal imaging, computational simulations, and experimental measurements. It investigates how various LED designs, compositions, and operational circumstances affect their thermal performance. The analysis's findings offer insightful information about methods for improving LED heat management and raising their overall effectiveness.

Design and Development of swarm AGV’s alliance for Search and Rescue operations

Rapid response is essential for saving lives in search and rescue operations since the amount of time is critical. In this project, a swarm of autonomous ground vehicles (AGVs) equipped with ROS-based software architecture will be designed and built for rapid search and rescue missions. The swarm of AGVs will function autonomously to navigate through challenging areas and be outfitted with a variety of sensors, including cameras, and LIDAR. The proposed system will be capable of performing 2D mapping, live video surveillance, autonomous navigation, victim/object detection, and two-way audio communication. The goal of the project is to reduce the risk to human life in dangerous areas by providing a quick and efficient response system for search and rescue operations. A centralized management system with a de-centralized module will be created as part of the project to keep an eye on and manage the AGV horde. However, there will be a functionality to take control of a specific robot in the swarm network when needed. In difficult areas where it might not be safe for humans to operate, the suggested method will enable quick and efficient search and rescue operations.

Recovery of tungsten from spent selective catalytic reduction catalyst by sulfuric acid precipitation and evaporation crystallization method

AbstractBACKGROUNDSelective catalytic reduction (SCR) can effectively handle NOx from flue gas in coal‐fired power plants. However, as the core part of the SCR method, V2O5–WO3/TiO2 catalyst has a limited operational life in the complex flue gas environment. The recovery of rare metals from spent catalyst would not only bring economic benefits but also solve environmental problems. The process of reducing acid leaching and further roasting‐water leaching could realize the efficient recycling of vanadium, tungsten and titanium.RESULTSAfter reducing acid leaching and roasting‐water leaching to treat spent SCR catalyst, the obtained solution containing tungsten was used as the raw material in this study. The optimal pH value of solution for removal of silicon and aluminum impurities was 9.2–9.5. The best tungsten precipitation conditions were shown as follows: a tungsten concentration of 30 g L−1, a sulfuric acid concentration of 8 mol L−1, reaction temperature of 70 °C and reaction time of 2 h. Under the optimal tungsten precipitation conditions, the tungsten precipitation efficiency can reach 92.53%. Finally, in order to further improve the purity of the crude H2WO4, the crude H2WO4 was fully dissolved in ammonia, followed by filtration and evaporation crystallization to obtain 5(NH4)2O.12WO3.5H2O (APT) crystals with a purity of 93.05 wt%. The crystallization efficiency of APT was 73.37% at 60 °C for 2 h with a rotor speed of 400 rpm.CONCLUSIONThese results indicated that a higher purity of APT crystals can be obtained by the steps of removing silicon and aluminum, precipitation of tungsten by sulfuric acid, ammonia dissolution and evaporation crystallization. © 2023 Society of Chemical Industry (SCI).

An LBM study of multichannel flow boiling for electronic thermal management coupling flow instability mitigation

The rising heat dissipation requirement on electronic devices urges a more efficient and energy-saving cooling strategy to keep the equipment operating within a safe temperature range. Multichannel flow boiling provides a straightforward solution to this challenge due to enormous latent energy of vapor preventing heat accumulation. However, pressure drop minimization and flow instability mitigation should also be considered for optimizing multichannel design. Hence, a Lattice Boltzmann Method (LBM) study on multichannel flow boiling process is conducted to provide design-based suggestions. The effects of surface wettability, channel number, input heat flux, and inlet velocity on the two-phase flow characteristics, heat transfer coefficient enhancement, dimensionless pressure drop, and flow instability are compared to examine the overall performance. Non-dimensional pressure drop is proposed for comparison through dividing the pressure drop under two-phase flow stage by the pressure drop under single-phase flow stage. Results show that hydrophilic coating prevents the film boiling transition at high input heat flux and reduces the maximum temperature for safer electronic operation. Designing a dense channel array can enhance the overall HTC but also significantly increase flow instability on the inlet, leading to shorter pumping operation life. A hybrid design of multichannel with downstream microgap region is proposed, and results indicate great mitigation ability with the increase of gap length and inlet velocity. These findings offer an invaluable blueprint for multichannel heat sink design and reveal the mechanisms of flow boiling enhancement.

Investigation of the cooling performance of a double-layer liquid-cooled plate with circular arc-shaped flow channels for thermal management of light-emitting diodes

Since the integration and heat flux of high-power light-emitting diodes (LEDs) are continuously increasing in response to the rising demand for illumination, high-power LEDs require a sophisticated thermal management system to ensure stable operation and prolonged service life. In the present work, a double-layer liquid-cooled plate with circular arc-shaped flow channels was developed. Circular arc-shaped flow channels may help the fluid flow against the channels' wall more effectively by preventing the development of eddy and impact flow and minimizing flow resistance. Combining it with the double-layer design may conduct cooling in the hot spot area twice as effectively. Numerical analysis and experimentation were conducted to explore the hydraulic properties and cooling performance of the plate, and the LED chips' arrangement schemes were examined. Water and ethylene glycol solutions with varying mass concentrations are utilized as the working fluids. The pin temperatures and illumination characteristics of LED chips were assessed after being cooled using the created plate at various flow rates. The results demonstrate the advantages of the proposed liquid-cooled plate's flow characteristics and cooling capability. After cooling, the LED chips' pin temperatures may be kept below 50 °C. When the flow rate was increased from 0.03 L/min to 0.18 L/min and the operating power of the LEDs was 300 W, the luminous intensity of the chips rose by 1440–1680 lx. Based on the temperature of the surrounding environment, the appropriate working fluid should be employed in practical applications. Furthermore, when the j/f coefficient is large, less pump work is needed, and the plate cools more effectively. It satisfies the need for a lightweight cooling system because the produced liquid-cooled plate weighs only 200 g.

Heat Transfer Analysis of Enhanced Geothermal System Based on Heat-Fluid-Structure Coupling Model

Dry hot rock geothermal resources by virtue of its wide distribution, large reserves, clean and low-carbon, stable, high utilization rate, and other characteristics have been widely used. The enhanced geothermal system (EGS) is the most efficient approach for harnessing and exploiting geothermal energy from hot, arid rock formations. To investigate the impact of varying parameters on heat recovery in EGS operations, we employed the COMSOL numerical simulation software to construct a seepage heat transfer model for fractured rock masses. Essential parameters and boundary conditions were established, followed by conducting numerical simulations. Through the numerical simulation results, the temporal and spatial changes of coupling effects among seepage field, stress field, and temperature field in fractured rock mass were analyzed. We investigated the impact of water injection temperature, injection-production pressure difference, injection flow rate, and initial reservoir temperature on the heat transfer process. The findings indicate that raising the water injection temperature and injection-production pressure difference can enhance the reservoir’s heat recovery capability. However, it may also accelerate thermal breakthrough and reduce the system’s operational lifespan. The higher injection flow rate can improve the heat recovery efficiency. However, too large injection flow can cause problems in other aspects of the reservoir; increasing reservoir temperature leads to higher production temperatures, which can potentially result in dynamic catastrophes. Therefore, while ensuring the heat recovery efficiency of the system, the operation life of the system can be extended by adjusting the water injection temperature in stages, setting a reasonable injection and production pressure difference, and selecting an appropriate injection flow rate, so as to achieve the purpose of EGS optimization.

High reliability of piezoresistive pressure sensors by wafer to wafer direct bonding at room temperature

As a micro-component for detecting and acquiring pressure data, piezoresistive pressure sensors are widely used in the microelectronic industry. Enhancing the sensitivity and reliability of piezoresistive pressure sensors can be achieved with optimized fabrication process and advanced techniques. However, in previous studies, there is limited information and knowledge of the relationship between the sensor performances and their fabrication process. In this study, we further optimized the fabrication process for piezoresistive pressure sensors, achieving a significantly higher stability of the pressure sensor compared with that of the commercial products obtained based on the standard test of “Pressure & High temperature Operating Life Test.” A detailed analysis revealed that both the designed structure of the piezoresistive pressure sensor and the preliminary thermal treatment conditions for tetraethylorthosilicate (TEOS) oxide substrate are critical factors that contribute to the improved performance of the pressure sensors. After low-temperature annealing, the atomic scale characterization of the interfaces between different material layers of the sensor showed well-proportioned interfaces. Furthermore, reducing water content in the sensors through high-temperature annealing is crucial for improving the stability of the piezoresistive pressure sensors.

Failure analysis and electrochemical testing of ammonium chloride corrosion in a heat exchanger in a diesel hydrotreating unit of a petroleum refinery

Crude oil is a complex mixture of hydrocarbons and can contain various impurities, which vary depending on the source and geographical location from which it is extracted. These impurities include sulphur, nitrogen, some metals, asphaltenes, non-condensable gases and salts. Salts in oil are typically found in the form of ions, which means that they are dissolved in the water present in the crude oil, or in the form of solid salts that are later deposited in equipment, pipes, and ducts. These salts can be harmful because, when the oil is processed, the water present in the oil can separate from the hydrocarbons and cause corrosion of equipment in the oil refining plant. In addition, salts can form solid deposits that can obstruct equipment. It is therefore important to remove or reduce the presence of salts in oil during the refining process to avoid operational problems and problems with the quality of the refined product. Several occurrences are reported in the specialized literature of equipment failures in the oil refining industry involving corrosion by salts, especially ammonium chloride salts. Basically, ammonium chloride, whose chemical formula is NH4Cl, is an inorganic chemical compound consisting of ammonium ions (NH4+) and chloride ions (Cl−), It is known by several names, including “ammonium salt” or “ammonium salt” due to its composition. The aim of this paper is to investigate the failure of a shell-and-tube heat exchanger in the charge preheater system of the diesel hydrotreating unit of a Brazilian oil refinery, in which the root cause of the failure identified as responsible for the damage was ammonium chloride corrosion. A severe corrosive process was observed in the tubes of the tube bundle, including perforation in some tubes, as well as damage to the inside of the heat exchanger shell. The analysis methods employed involved the study of three different types of austenitic stainless steel in terms of corrosion resistance: 304, 316L and 317L, which were exposed to media containing sodium chloride and ammonium chloride at a concentration of 3.5 % (m/v). Two electrochemical corrosion tests were carried out in aqueous media, the first determining potentiodynamic polarization curves and the second electrochemical impedance spectroscopy. In addition to material characterization tests, such as determining the chemical composition, hardness and scanning electron microscopy of the corroded samples. The results of this paper indicate that the 317L steel samples have larger passivation regions, higher pitting potential values, lower passivation current density values, as well as lower corrosion rate values during the simulation of the equivalent electrochemical circuit, which implies greater resistance to corrosion in a medium containing ammonium chloride, compared to the others. The conclusions reached reveal the applicability of 317L austenitic stainless steel in environments containing ammonium chloride, such as in the diesel hydrotreating sections of oil refineries, in addition to the use of washing water in pipes and equipment to dissolve these salts. Due to the high corrosion resistance of 317L steel in media containing ammonium chloride, it could be extended to other refining sections, such as distillation, cracking and coking units in oil refineries. This research will enable potential gains in terms of increasing the operational life of equipment and installations, reducing corrective maintenance interventions and operational safety in the operation of the industrial plant.