Abstract: Irradiation damage in materials for nuclear reactors, particularly for fusion reactors, is a serious problem. For example, the pressure vessel in a fission power plant becomes brittle after exposure to neutron irradiation for many years. In the case of fusion reactors, in addition to the increase in ductile-to-brittle transition temperature, irradiation-induced swelling occurs in structural materials that need to tolerate high-dose irradiation of several hundreds of displacements per atom (dpa). The irradiation of particles (such as neutrons, ions, and electrons) with high energy introduces a large number of point defects, i.e., self-interstitial atoms and vacancies, into materials. Such point defects aggregate together to form self-interstitial atom clusters as interstitial loop and vacancy clusters as void, stacking fault tetrahedra, or vacancy loop. Then, these clusters affect the microstructure and properties of materials. Moreover, these clusters play a more important role than individual point defects during the irradiation damage process. Even after research for decades, many questions about clusters remain unanswered partially because of the difficulties in irradiation test and cluster observation. This review paper explained the structures of clusters and the effect of clusters on irradiation damage in materials. As a unique research of this author’s group, the formation of vacancy-type dislocation loops with sizes of up to 100 nm in iron was introduced, including the effect of hydrogen and its isotope and the effect of alloy elements on the formation of vacancy-type dislocation loops. There are two different kinds of vacancy-type dislocation loops, i.e., those having a Burgers vector of b=<100> and those having a Burgers vector of b=1/2<111>. The density of the first type is approximately one order of magnitude higher than that of the second type. The one-dimensional motion of self-interstitial atom clusters and the research activities in this field were also discussed in detail, and the one-dimensional motion would be a key factor effecting the irradiation damage of high entropy alloys.
Abstract: Metallurgical process engineering proposed by academician Ruiyu Yin is a new branch in the field of metallurgy, which deals with the physical nature, structure, and global behavior of metallurgical manufacturing process. Process interface technology used in steelmaking-continuous casting section (SCCS) is developed from metallurgical process engineering. It is used to study and analyze the running dynamics of mass flow in steelmaking plants. In recent years, the intelligent and green production in steelmaking plants has become the demand and necessity of the time because of the rapid development of intelligent manufacturing represented by Industry 4.0 in Germany. Nowadays, the automation control of single-process has been realized in most steelmaking plants at home and abroad, which is a stepping zone and has created the foundation for the intelligent and green production. But at the same time, importance also should be given for the improvement in the multi-process operation of SCCS considering the global optimization on steelmaking production. Undoubtedly the process interface technology is an important method to deal with the collaboration-optimization of process relationship set, but also it has a greater influence on the analysis-optimization of process function set and the reconstruction-optimization of process set. Therefore, the process interface technology has created lot of interest and drawn greater attention from scholars and experts of metallurgy, which results in the great improvement of the multi-process operation in SCCS. Currently, three kinds of classic process interface technologies, including ladle cycling control, crane running control, and operation mode optimization, have become the most important research areas because of their significant effect on the high-efficient connection of mass flow among multi-process. The scope of ladle cycling control includes the monitoring of thermal state and the matching and scheduling of ladles. The task assignment and multi-crane collaborative scheduling are the most important components of crane running control and it is of great interest to research further. When operation mode optimization is considered, the improvement of furnace-caster coordinating mode based on the matching of capacity and rhythm can be regarded as the most interesting research area. It is known that the operation mode is the fundamental for ladle cycling and crane running, and moreover, the status of ladle cycling and crane running also can guide the further optimization of operation mode. Based on above analysis, this paper presented a detailed overview of progress made in the research on abovementioned three kinds of classic process interface technologies in SCCS. Further, the necessity of collaboration between process interface technologies was also illustrated, aiming at unfavorable restraints of multi-process collaborative operation. In addition, the collaboration mechanisms and schemes of all three kinds of classic process interface technologies were described in detail. Finally, it is expected that this review could offer some reference and guidance for the improvements in multi-process operation of SCCS.
Abstract: The nondestructive technique for testing ferromagnetic materials known as the metal magnetic memory method is formally proposed in 1997 by the Russian scholar Dubov at the 50th International Conference on Welding. The main advantage of this metal magnetic memory technology is that no external excitation magnetic field source is required. That is, by the excitation of the natural geomagnetic field, when a ferromagnetic member is subjected to external stress, a free magnetic leakage field is generated around the stress concentration or defect position of the ferromagnetic member due to the magnetic-force coupling effect. By measuring and analyzing the magnetic leakage signal on the surface of the material, the stress concentration, early damage, and degree of damage in the ferromagnetic member can be readily detected and evaluated to effectively prevent sudden brittle failure of the structure or member. This technique is the only effective nondestructive testing method for diagnosing early damage in ferromagnetic components. Because this metal magnetic memory testing technology can be used to assess the stress concentration, early damage position, and the degree of damage of ferromagnetic materials, it has great potential for use in predicting structural or component life and warning of damage. Its advantages include no manual magnetization or attached sensor, no surface treatment of components, and simple, convenient, and quick operation. As such, it has attracted wide interest from scholars around the world since its formal introduction. In this paper, based on the research on metal magnetic memory testing technology over the past 10 years, a theoretical model of the technology was established and the progress made in the theoretical research, experimental research, and engineering applications of this technology were summarized. The damage assessment criteria for magnetic memory testing technology were discussed and the factors that affect the magnetic memory detection signal were analyzed. Based on this review, the current problems were identified and future research directions of magnetic memory testing technology were proposed.
Abstract: Shale gas is a type of unconventional natural gas that can be accumulated in a large area in tight shale and has self-generation and self-storage abilities. The low porosity and low permeability characteristics of shale make its development under natural conditions poor, and large-scale stimulations of its production are needed to achieve economic benefits. Due to the complex geological tectonic conditions in China, three types of organic-rich shale strata, namely, marine facies, marine-continental facies, and continental facies, are developed during the multicycle tectonic evolution. China has made important breakthroughs in the exploration and development of marine shale gas. Considerable effort has also been invested in the exploration of continental shale gas. The exploration and research of marine-continental transitional shale have gradually attracted people’s attention. Marine-continental transitional shales are of importance to the shale gas field. However, research on transitional shale gas exploitation is still in its infancy, and this topic needs to be urgently discussed and solved. Shale gas exploitation seriously restricts the development level of shale gas in China. The shale gas in the Zhongmou Block of the southern North China Basin is a typical representative of marine-continental transitional shale gas, with good gas resources and development prospects. In this study, based on a geologic model, the influences of different reservoir parameters on oil recovery, daily gas production, and cumulative gas production were examined through the integration of theoretical analyses and numerical simulations. The main factors affecting the gas production capacity of shale were determined by an orthogonal design and multi-index analysis. Considering the relationship between main control factors and shale gas production capacity, the cumulative gas production and shale gas recovery equations under the horizontal fracturing condition were established. For the target fracturing zones, the shale gas productions under different fracturing parameters were compared and analyzed, which shows that the horizontal length and producing degree are the main parameters that determine the production capacity. In a certain fracturing condition, the increase in fracture length can effectively communicate natural cracks, thereby increasing production capacity. Taking a net present value greater than 0 and a yield rate ranging from 8% to 12% as the economic evaluation indices, three types of fracturing parameters are optimized for the marine-continental transitional shales.
Abstract: It is a fact that a large number of defects such as cracks, voids, inclusions, weak planes, and joint sets are generated within the rock mass during the process of rock formation because of geological-tectonic evolution. The existence of these preexisting natural defects poses potential threats to the stability and safety of structures built on the rock mass. Therefore, it is highly significant to better understand the effects of the preexisting defects on the rock mechanical and fracture behaviors for the stability and safety assessment of rock structures. Uniaxial compression tests were carried out by using ?50 mm × 50 mm cylindrical marble specimens with double parallel flaws at end surfaces. When tests were performed, a high speed camera was used to capture the failure processes of the marble specimens. The effects of the flaw length and inclination angle on the mechanical properties and crack propagation of marble specimens were investigated. Further, the experimental results indicate that the uniaxial compressive strength, elastic modulus, and peak strain of the specimen decrease slightly before the flaw length reaches the threshold value. Compared to flaws at vertical angle 90°, flaws at inclined angles (0°<α<90°) of the same length have larger effect on the mechanical properties of marble. It is found from both the experimental and theoretical analysis that cracks usually do not start from the tip of vertical end flaws and most of initiation cracks are developed into dominant cracks. In addition, there are few branches and bifurcations in the crack propagation process, and further, local spalling also occurs at the surface of the specimen. The specimens with inclined flaws exhibit shear failure or combined shear and tensile failure and the ones with vertical end flaws show axial splitting tensile failure. The variation trend of energy consumption parameters is consistent with that of uniaxial compressive strength. It is found that total strain energy of the specimen is positively correlated with its uniaxial compressive strength. Finally, the difference between mechanical and crack propagation processes of marble specimens with end flaws under dynamic and static loads were compared.
Abstract: Cobalt-rich crusted deposits are found all over the world’s oceans, and their distribution is closely related to the submarine topography. The determination of crusting area is the basic work for the exploration and mining of these deposits. Many factors affect the accumulation of crusts, and topography is a crucial factor. Mineralization forecast requires comprehensive consideration of geological background and experts’ views and opinions, the prior knowledge of prospectors is the biggest factor affecting the results. In the course of ocean research, especially with the rapid development of space information technology, a huge amount of ocean data that cover about 70% of the total surface area have been accumulated rapidly; how to extract valuable information from large, fast, complex, and multisource data has become a hot topic in current ocean research. Machine learning- and deep learning-related research methods can read feature signs from mineral data to obtain existing mineral knowledge to further serve mine prediction work. Based on the study of terrain features of cobalt-rich crust in high-producing areas, the numerical matrix of altitude of 1 km2 ocean surface was obtained, with the geographical coordinates of cobalt-rich crust sites as the center. Using the analysis method of convolutional neural network, the numerical matrix is trained to learn regional features such as slope and flatness and to distinguish the cobalt-rich crust–crust site topography from other submarine topography. According to the training model, the high-producing cobalt-rich crusting area was predicted and better forecasting value is obtained. Meanwhile, the accuracy of the selection of crusting target area was improved by combining the influence of other factors.
Abstract: Using eyes with high concentration for long periods can cause visual fatigue. With the continuous development and progression of modern electronic devices, screens have become an integral part of many aspects of life. Watching a screen for a long time can cause extreme eye fatigue and accidents. A wireless monitoring system including multiple communication platforms is a new means of monitoring in confined spaces, which requires people to perform visual display terminal (VDT) operations in common operating places such as dispatch rooms, cabins, and shipyards. Visual fatigue in a confined space is one of the main causes of accidents. To explore the effect of lighting in a limited space on visual fatigue of VDT, 24 operators were selected to perform VDT typing in a confined space platform for 1 h, and seven light gradients were set within the range of 50–700 lx to collect pupil diameter data using an eye tracker. The collected data were normalized to reduce noise. Experimental results show that with an increase in illuminance, the pupil diameter generally decreases and the pupil–illuminance relationship conforms to the power function relationship. In high-illumination environments (400, 550, and 700 lx), the pupil diameter change rate fluctuates in the ?12%–8% range, and with the increase in light intensity, the degree of visual fatigue of workers increases. Under low-illumination environments (50, 100, and 200 lx), the pupil diameter change rate fluctuates in the range of ?8%?4%, and the degree of visual fatigue of the workers also increases with decreased intensity. This study proposes to use the windowed pupil diameter standard deviation, σ, to determine the time of visual fatigue. The peak value of σ under low illumination is earlier than that under high illumination; the peak value of σ under 300-lx illumination is the latest, weak illumination. The fatigue degree of vision caused by 50?300 lx is greater than that caused by strong illumination of 300?700 lx.
Abstract: This paper focuses on the radius of coal failure zones under cumulative blasting with shaped charge. Based on the analysis of the mutual superposition effect of the explosion stress waves during the simultaneous detonation of two blastholes, a numerical analysis model of the double-hole cumulative blasting with linear shaped charge was established. Additionally, the propagation characteristics of the stress wave during the simultaneous detonation of two blastholes, stress state of the coal body, mechanism of coal crack propagation and coalescence, and influence of the stress wave superposition effect on crack propagation were evaluated. Results show that the stress wave superposition effect induces the formation of a pressure equalization zone in the partial region of the middle section of the two blastholes and its adjacent regions. This occurrence forces the radial cracks of the two blastholes to turn, and they cannot connect with each other, leading to the formation of a gap blank zone between the two blastholes. After the directional cracks generated under cumulative blasting load coalesce, the collision of the explosive gases produced from the two blastholes further promotes the expansion of the cracks in the directional crack coalescence zone and eventually penetrates the gap blank zone. Field test results of deep-hole cumulative blasting in coal seams show that the explosion stress waves from the blastholes in the opposite side promotes the propagation of the blasting-induced crack on the left or right side of the two blastholes. This propagation first increases and then decreases as it moves away from the blasthole. Between the two blastholes, the stress wave superposition effect from the two blastholes inhibits the propagation of the cracks in some areas, resulting in a W-like fluctuation in the degree of improvement of the gas drainage effect at different positions in the area between the two blastholes.
Abstract: Although zinc–nickel (Zn–Ni) secondary batteries have numerous advantages, these have not been widely used in practice. The main reason is that problems such as the formation of dendritic zinc, corrosion, and passivation are encountered in the use of zinc anode. These problems restrict the development of Zn–Ni secondary battery using zinc electrode. To improve the electrochemical properties of zinc anode, researchers are constantly looking for new materials to be applied to Zn–Ni secondary batteries. Recently, many studies on the modification of zinc oxide and the electrochemical properties of calcium zincate have been conducted. The improvement measures can effectively enhance the corrosion resistance and cycle stability of Zn–Ni secondary batteries, but the improvements are not up to expectations. Therefore, researchers have now focused their attention on the research and development of new materials. The unique properties of hydrotalcite have attracted the attention of researchers. Hydrotalcite has shown excellent performance in electrocatalysis, medicine, nanofillers, and other functional fields. Moreover, because hydrotalcite has high stability in alkaline solution, hydrotalcite may become a new material for alkaline batteries. Presently, hydrotalcite, as a new kind of B-type material, has been used in alkaline secondary batteries; the performance of these batteries is excellent. The introduction of Zn–Al LDHs effectively improves the electrochemical properties of Zn–Ni secondary batteries. Therefore, this study proposes the application of Zn–In LDHs to Zn–Ni secondary batteries for the first time to analyze its electrochemical properties. Zn–In LDHs were prepared via the hydrothermal method and used as a new anode material for Zn–Ni secondary batteries. The morphology and microstructure of Zn–In LDHs were analyzed via scanning electron microscopy and X-ray diffraction, respectively. The electrochemical properties of Zn–In LDHs as anode material for Zn–Ni batteries were investigated via cyclic voltammetry, Tafel extrapolation of polarization curves, and galvanostatic charge–discharge test. The morphology of Zn–In LDHs shows a hexagonal structure. The electrical properties of Zn–In LDHs show that they have good cycle reversibility and corrosion resistance when Zn–In LDHs are applied to Zn–Ni secondary batteries. The analysis of the constant current charge–discharge test results shows that Zn–In LDHs have excellent cycle stability and charge–discharge characteristics. After 100 cycles, the cycle retention rate can reach values of up to 92.25%.
Abstract: Aluminum alloys are lightweight materials widely used in the automobile industry because of their high specific strength. As the aluminum alloy with the highest strength at room temperature, 7075 aluminum alloy has great potential for usage in the manufacturing of structural parts. However, its formability at room temperature is poor and its springback is large. Although both good formability and high strength in aluminum alloys can be realized by hot forming, 7075 aluminum alloy has high susceptibility to adhesive wear, which means its tribological properties are poor during hot forming. Exploration of the influence of process parameters on the friction behavior and wear mechanism of 7075 aluminum alloy has great significance for the numerical simulation of the hot-stamping process and lubrication engineering. The high-temperature friction process of 7075 aluminum alloy during the actual hot forming–quenching integrated process was simulated by a self-made high-temperature strip friction tester. The upper and lower friction components were cooled and heated, respectively, to simulate the cooling and heating of the die (blank holder) in the actual hot-stamping process. The effects of the preheating temperature of the lower die, normal load, and sliding speed on the friction behavior and wear mechanism of 7075 aluminum alloy were analyzed. The results show that the friction coefficient of aluminum alloy increases with increase in the preheating temperature, and the wear mechanism changes from adhesive wear at 300 °C to adhesive, abrasive, and oxidative wear at 500 °C. The larger the normal load applied, the larger is the friction coefficient. The wear mechanism under different loads was determined to be adhesive wear with slight abrasive wear, with the degree of adhesive wear increasing with the increase in load. A high sliding speed leads to the formation of local oxides on the surface, which makes the friction coefficient decrease with an increase in the sliding speed. The main wear mechanisms are oxidative, abrasive, and adhesive wear when the sliding speed is 30 mm·s?1.
Abstract: Titanium/steel composite plates are widely used in petrochemical equipment, seawater desalination equipment, nuclear power equipment, ocean engineering, and other fields owing to the excellent corrosion resistance of titanium and low steel cost. Various methods have been adopted for manufacturing titanium/steel composite plates, which include explosive bonding, explosive-rolling bonding, diffusion bonding, and hot rolling bonding. Among these techniques, hot rolling bonding method enables the production of large-sized titanium/steel composite plates with high efficiency, low pollution, and low energy consumption. However, electron beam welding of billets is required to prevent interface oxidation and the formation of brittle compounds such as TiC, FeTi, and Fe2Ti on the interface, which may cause the degradation of mechanical properties of titanium/steel composite plates. In this study, the precomposite formation of billets was done through cold rolling and the titanium/steel composite plates were prepared via single pass hot rolling after induction heating to the hot rolling temperature. The effect of induction heating temperature on the interfacial structure and bonding properties of titanium/steel composite plates was studied. The results show that the interface of titanium/steel composite plates prepared by the cold–hot rolling composite method is tightly bonded without holes and gaps. The short induction heating and hot rolling time (<5 s) are insufficient for the formation of intermetallic compounds on the carbon steel side of the composite plates, yielding only a small number of blocky hardened layers at the titanium/steel interface. Higher induction heating temperature results in wider Ti and Fe element diffusion layer at the interface, with the maximum width of 8 μm obtained at 950 ℃. The titanium/steel composite plates in this study achieved good metallurgical bonding with induction heating temperatures of 750 ℃ to 950 ℃.
Abstract: Thermal and sound insulation material in aircraft can ensure that the crew and passengers are in a relatively comfortable environment. To analyze the flame propagation characteristics of thermal and sound insulation superfine glass fiber wool, the flame propagation characteristics of glass fiber wool exposed to radiant heat and open flame were investigated using a flame propagation characteristic tester. Results show that, when the ignition time increases from 15 to 85 s, the maximum distance of forward flame spread along the Y-axis increases from 280 to 435 mm. Moreover, the flame spread rate initially decreases, subsequently increases, and finally decreases. According to the analysis, the flame propagation rate increases because the sample is cut during the preparation process so that local oxygen is supplemented to a certain extent. When the temperature of the radiant plate increases within the range of 700?820 ℃, the maximum distance of the flame spreading along the Y-axis was continuously increased from 280 to 390 mm, an increase of 110 mm, indicating that the increase in the temperature of the radiant plate has a significant positive effect on the spread of the flame. Furthermore, the growth rate of the flame that spreads the longest along the Y-axis decreases. By monitoring the real-time temperature inside the glass fiber wool at different positions during the combustion process, we determined that the temperature at the monitoring point close to the ignition source is generally high, and at the same time, the maximum temperature appears longer than the ignition time. The quantitative fitting curve of the furthest distance of forward flame spread along the Y-axis and the thickness of the glass fiber wool is obtained. The thicker the glass fiber wool is (i.e., from 12 to 48 mm), the more obvious the effect on preventing flame spread and diffusion. When the glass fiber wool is burned, more heat is propagated along the thickness direction of the inner layer, thereby reducing the flame heat propagation speed and spread distance along the Y-axis forward direction.
Abstract: While the industrial robotic manipulator is a kind of multi-input and multi-output human-like operation and highly autonomous control system. It is widely used in medical care, home service, industrial manufacturing and other fields. With the integration of cyber-physical system networks and the Internet in recent years, the control commands of the industrial robotic arm control system can be totally exposed to the Internet. Under these circumstances, the chances of successful attacks by attackers to systems are increasing year by year. Compared to the security of traditional cyber physical system, the security of manipulator control system is a very challenging problem. In this paper, a covert attack method of 7 degrees of freedom (7-DOF) manipulator control system was proposed. Firstly, based on the inverse kinematics equation of the manipulator, the motion planning and modeling of 7-DOF manipulator, which communicated by EtherCAT, was carried out. Secondly, according to the research and analysis of particle swarm optimization method, a 7-DOF manipulator system PID parameter identification algorithm based on chaotic theory for multi- swarm particle swarm optimization was proposed. Parameter identification mainly identified the PID parameters of each joint. The principle and derivation process of the algorithm were described in detail. Finally, the experimental platform of manipulator control system was built and the identified parameters were used in combination with the covert attack principle to conduct the experiment. The proposed method was compared with other traditional attack methods, such as state machine attack and traditional sine attack. The results show that the covert attack model of the proposed 7-DOF manipulator can destroy the data integrity and accuracy of the manipulator system, and has a good concealment, which verifies the effectiveness and feasibility of the established attack model. The attack experiment platform constructed in this paper provides the physical basis for the attack and defense experiment of the manipulator, and it has certain reference significance for similar researchers.
Abstract: With the development of civil aviation safety management, the flight operation risk of airlines is of increasing concern. Risk prediction technology extracts information from historical and current risk data and uses it to predict short-term trends in the future, thus helping identify emerging risks and providing more time for risk management. Compared with non-dynamic risk assessment, this technology is more substantial for the management and control of flight operation risk. To improve the accuracy of flight operation risk prediction, on the basis of the flight risk data of a certain airline in 2016—2018, the chaotic characteristics of 15 risk time series were verified and a short-term risk prediction model based on the multivariate chaotic time series was constructed. First, multivariate phase space reconstruction was performed on 15 risk time series, and the phase space was reduced by the principal component analysis (PCA) method. Then, four short-term risk prediction models, namely, extreme learning machine, radial basis function (RBF) neural network, echo state network, and Elman neural network, were built on the basis of iterative prediction. Finally, the phase space after dimension reduction was used as the model input, and the risk prediction results for 1–7 d were calculated and compared. Results show that the total number of dimensions after multivariable phase space reconstruction is 62, which is reduced to 31 by PCA dimension reduction. Of the four prediction models, the RBF neural network model after dimension reduction has the best prediction effect. The occurrence frequency of <25% relative error is 82.62% for the first day and 75% for the fifth day. The corrected mean absolute percentage error for the first day is 11.32%, and lower than 20% for the next 4 d. Thus, the calculation results meet the requirements of the airline. The prediction results within 1–5 d have practical value for flight risk management, proving that the risk prediction method based on the multivariate chaotic time series is feasible and effective.
Abstract: In 2016, a novel naturally simulated optimization algorithm, termed the sine cosine algorithm (SCA), was proposed by Seyedali Mirjalili from Australia. This algorithm uses the sine cosine mathematical model to solve optimization problems and has attracted extensive attention from numerous scholars and researchers at home and abroad over the last few years. However, similar to other swarm intelligence optimization algorithms, SCA has numerous shortcomings in optimizing some complex function problems. To address the defects of basic SCA, such as low optimization precision, easy dropping into the local extremum, and slow convergence rate, a sine cosine algorithm based on differential evolution (SCADE) was proposed. First, the search capabilities of the new algorithm was improved by adjusting parameter r1 in a nonlinear manner and ensuring that each individual adopts the same parameters r1, r2, r3, and r4. Then, differential evolution strategies, including crossover, variation, and selection, were adopted to fully utilize the leading role of the globally optimal individual and information of other individuals in the population. This approach balanced the global exploration and local development abilities and accelerated the convergence rate of the algorithm. Next, using the reconnaissance bees’ strategy, random initialization was performed on individuals whose fitness values showed no improvement in continuous nlim times, which increased the population diversity and improved the global exploration ability of the algorithm. Moreover, the globally optimal individual variation strategy was used to conduct a fine search near the optimal solution, which enhanced the local development ability and optimization accuracy of the algorithm. Based on the above optimization strategies, the algorithm exhibits improvements and its excellent performance is validated by the result analysis of a simulation experiment.
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
