Explore the vast range of titles available.

Titanium alloy is widely applied in aerospace, medical, shipping and other fields due to its high specific strength and low density. The purpose of this study was to analyze the formability of Ti6Al4V alloys at elevated temperatures. An accurate constitutive model is the basic condition for accurately simulating the plastic forming of materials, and it is an important basis for optimizing the parameters of the hot forging forming process. In this study, the optimization algorithm was used to accurately identify the high-temperature constitutive model parameters of Ti6Al4V titanium alloy, and the hot working diagram was established to optimize the hot forming process parameters. The optimal forming conditions of Ti6Al4V titanium alloy are given. Ti6Al4V alloy was subjected to high-temperature compression tests at 800–1000 °C and at strain rates of 0.01–5 s−1 on a Gleeble-1500D thermal/mechanical simulation machine. Each parameter of the Hansel–Spittel constitutive model was taken as an independent variable, and the accumulated error between the stress calculated by the constitutive model and the stress obtained by experimentation was used as an objective function. Based on response surface methodology, an inverse optimization method for identifying the parameters of the high-temperature constitutive model of Ti6Al4V alloy is proposed in this paper. An orthogonal test design was adopted to obtain sample point data, and a third-order response surface approximate model was established. The genetic algorithm (GA) was applied to reversely optimize the parameters of the constitutive model. To verify the accuracy of the optimized constitutive model, the average absolute relative error (AARE) and correlation coefficient (R) were used to evaluate the reliability of optimized constitutive model. The R value of the model was 0.999, and the AARE value was 0.048, respectively, indicating that the established high-temperature constitutive model for Ti6Al4V alloy has good calculation accuracy. The flow stress behavior of the material could be accurately delineated. Meanwhile, in order to study the formability of Ti6Al4V alloy, the hot processing map of the alloy, based on a dynamic material model, was established in this paper. The optimum hot working domains of the Ti6Al4V alloy were determined within 840–920 °C/0.01–0.049 s−1 and 940–980 °C/0.11–1.65 s−1; the hot processing map was verified in combination with the microstructure, and the fine and equiaxed grains and a large amount of β phase could be found at 850 °C/0.01 s−1.

In the present work, the deformation behavior and processing maps of a low-carbon Fe-2 wt% Nb steel were studied by means of hot-compression tests at temperatures of 800–1150 °C and strain rates of 0.01–10 s−1. The hot-processing maps at different strains and corresponding microstructural evolution were constructed and discussed. The hot-deformation behaviors of two different phase regions, i.e., austenite + NbC dual-phase and ferrite + NbC dual-phase, were predicted by determining the constitutive equations using Arrhenius-type and Zener–Hollomon models. The results suggest that the hot-deformed microstructures of the material present a strong correlation with the processing parameters in the hot-processing maps. In addition, the optimum parameters based on the processing maps were obtained, and the instable and the safe domains during the hot deformation in the hot-processing maps provide solid theoretical guidance for industrial production.

The microstructure evolution and hot deformation behavior of 9Cr18Mo stainless bearing steel were studied with the hot compression test at the temperature ranging from 1 223 to 1 423 and strain rates from 0.01 to 10 s -1 . The results indicate that the 9Cr18Mo stainless steel shows strong positive strain rate sensitivity and negative temperature sensitivity. The softening mechanism is dynamic recrystallization and dynamic recovery mechanism. A constitutive equation with the strain compensation considered was developed and the prediction value is in good agreement with the experimental value. The processing map of 9Cr18Mo stainless steel was established with the Murty criteria. Combined with microstructure analysis, the optimal hot processing parameter range is between 1 050 ℃ and 1 120 ℃ and the strain rate is between 0.1 and 1 s -1 . The composition distribution of the microstructure of 9Cr18Mo stainless steel was analyzed with the EDS. In combination with the calculation results of the JMAPTPRO software, it was determined that the coarse banded carbides were not dissolved in the matrix at high temperature were composed of M 7 C 3 carbide and M 23 C 6 carbide. 利用热压缩试验研究了9Cr18Mo不锈轴承钢在变形温度为950~1 150 ℃、应变速率为0.01~10 s -1 条件下的显微组织演化和热变形行为。结果表明: 9Cr18Mo不锈钢表现出较强的正应变速率敏感性和负温度敏感性, 软化机制为动态再结晶和动态回复机制。建立了应变补偿型Arrhenius本构方程, 计算值与试验值吻合。基于Murty准则建立了9Cr18Mo不锈钢的热加工图, 结合显微组织分析, 确定了9Cr18Mo不锈钢的最佳加工参数为: 变形温度为1 050~1 120 ℃、应变速率为0.1~1 s -1 。采用EDS分析了9Cr18Mo不锈钢显微组织的成分分布, 结合JMAPTPRO软件计算结果, 确定了高温下未溶于基体的粗大带状碳化物由 M 7 C 3 型碳化物和 M 23 C 6 型碳化物组成。

The plastic deformation behavior of selective laser melting (SLM) 3D printed SS316L steel has been analyzed at the temperature range 25- 1000℃ (25 (room temperature), 200, 400, 600, 800 and 1000℃) and strain rate range 10 −3 -10 3 s −1 (10 −3 , 10 −2 , 10 −1 , 10 0 , 10 1 , 10 2 and 10 3 s −1 ) under compressive loading environments. The flow stress vs. plastic strain results revealed that the flow stress was reduced 136.64% from room temperature to 1000℃ at 10 −3 s −1 . Further, the flow stress was decreased 102.86% from room temperature to 1000℃ at 10 3 s −1 . The flow stress was increased 46.63% from 10 −3 s −1 to 10 3 s −1 at room temperature. Moreover, the flow stress was increased 95.07% from 10 −3 s −1 to 10 3 s −1 at 1000℃. The temperature and strain rate effect on strain rate sensitivity (m) has been observed for SLM 3D printed SS316L steel. Based on strain rate sensitivity (m), the power dissipation efficiency ( ) and instability dimensionless parameter ( ) map plot contours have been investigated under various hot working parameters for SLM 3D printed SS316L steel. Further, hot working processing maps have been generated by superimposing instability dimensionless parameters ( ) map on the power dissipation efficiency ( ) map for SLM 3D printed SS316L steel. The processing map was further related with investigated material microstructure to identify the hot processing safe and unsafe zone for SLM 3D printed SS316L. The unsafe instability region occurred at the low strain rate range (10 −2 – 10 −1 s −1 ), high strain rate range (10 2 -10 3  s −1 ) and temperature range (200–400℃, and 800 − 100℃) for 0.02, 0.04, 0.06, 0.08 and 0.10 strain. Further, the remaining area was useful for hot workability. The Vicker’s hardness revealed that the hardness was decreased with 3.87%, 12.55%, 22.01%, 32.35%, and 43.70% at 200 0 C, 400 0 C, 600 0 C, 800 0 C and 1000 0 C respectively with respect to room temperature hardness.

To further investigate the properties of Incoloy825/P110 bimetallic composite seamless pipes, thermal deformation analysis was conducted on their billets. The thermal deformation and dynamic recrystallization (DRX) behavior of Incoloy825/P110 bimetallic composite materials were studied through hot compression tests at deformation temperatures (850–1150 °C) and strain rates (0.01–10 s −1 ). A constitutive relationship was established, and compensation and correction were made based on the differences in materials corresponding to different strain states. The hot processing map was established based on the thermal deformation behavior of bimetallic materials. In addition, the evolution of microstructure was also studied to verify the feasibility of the established hot processing map. The results show that the strain compensated Arrhenius can accurately predict the flow stress. By analyzing the microstructure using EBSD, it can be found that DRX behavior has a significant impact on the thermal processing properties of composite materials. This study provides an important theoretical basis for the production of Incoloy825/P110 bimetallic composite seamless pipes in the future.

Investigations using hot compression tests on a new high-strength weathering steel revealed specific deformation behaviors across different conditions. These tests were performed at temperatures ranging from 850 to 1050 °C and at strain rates from 0.01 to 5 s −1 . Results indicated that a decrease in the deformation temperature combined with an increase in strain rate notably enhanced both the maximum stress and strain achieved. Notably, above 900 °C and with strain rates below 0.1 s −1 , the flow stress of the material reached a steady state at certain strain levels. At a strain rate of 1 s −1 , irrespective of the temperature, the steel shows a continuous strain hardening behavior, achieving no stable flow stress state. Notably, when the true strain exceeds 0.8, an unusual increase in flow stress occurs, predominantly due to secondary work hardening effects. The microstructural changes in the deformed samples were examined using electron backscatter diffraction (EBSD), which helped elucidate the softening mechanisms inherent in this high-strength steel. Further, processing maps developed from true strains of 0.1–0.9, derived from the experimental flow stress data, suggest controlling the strain within 0.2–0.4 to minimize instability during hot working.

Airspace geofencing is a key capability for low-altitude Unmanned Aircraft System (UAS) Traffic Management (UTM). Geofenced airspace volumes can be allocated to safely contain compatible UAS flight operations within a fly-zone (keep-in geofence) and ensure the avoidance of no-fly zones (keep-out geofences). This paper presents the application of three-dimensional flight volumization algorithms to support airspace geofence management for UTM. Layered polygon geofence volumes enclose user-input waypoint-based 3-D flight trajectories, and a family of flight trajectory solutions designed to avoid keep-out geofence volumes is proposed using computational geometry. Geofencing and path planning solutions are analyzed in an accurately mapped urban environment. Urban map data processing algorithms are presented. Monte Carlo simulations statistically validate our algorithms, and runtime statistics are tabulated. Benchmark evaluation results in a Manhattan, New York City low-altitude environment compare our geofenced dynamic path planning solutions against a fixed airway corridor design. A case study with UAS route deconfliction is presented, illustrating how the proposed geofencing pipeline supports multi-vehicle deconfliction. This paper contributes to the nascent theory and the practice of dynamic airspace geofencing in support of UTM.

Spatially explicit, fine-grained datasets describing historical urban extents are rarely available prior to the era of operational remote sensing. However, such data are necessary to better understand long-term urbanization and land development processes and for the assessment of coupled nature–human systems (e.g., the dynamics of the wildland–urban interface). Herein, we propose a framework that jointly uses remote-sensing-derived human settlement data (i.e., the Global Human Settlement Layer, GHSL) and scanned, georeferenced historical maps to automatically generate historical urban extents for the early 20th century. By applying unsupervised color space segmentation to the historical maps, spatially constrained to the urban extents derived from the GHSL, our approach generates historical settlement extents for seamless integration with the multi-temporal GHSL. We apply our method to study areas in countries across four continents, and evaluate our approach against historical building density estimates from the Historical Settlement Data Compilation for the US (HISDAC-US), and against urban area estimates from the History Database of the Global Environment (HYDE). Our results achieve Area-under-the-Curve values >0.9 when comparing to HISDAC-US and are largely in agreement with model-based urban areas from the HYDE database, demonstrating that the integration of remote-sensing-derived observations and historical cartographic data sources opens up new, promising avenues for assessing urbanization and long-term land cover change in countries where historical maps are available.

On the example of our project on the creation of the historical web atlas on Czech history, we introduce the process of adapting originally printed historical maps for their presentation in the web environment, which overcomes the shortcomings of standard approaches in similar projects based on printed predecessors published only as zoomable scanned analogues or default GIS maps. To simplify the originally complex map and to increase the information potential of the maps, we propose seven different types of additional map functionality according to the specific characteristics of the original map content. In addition, we present a set of rules, principles, recommendations, and methods for the cartographic design and processing of originally printed historical maps that should be considered when they are prepared for presentation on the web, including the description of the specific visualisation processes for the proposed types of map functionality. The proposed complex methodology can be applied to similar projects focused on the conversion of originally printed maps to the web and may contribute to improving the quality of the visualisation and presentation of historical maps on the web in general.

The hot deformation behaviours of 316LN-Mn austenitic stainless steel were investigated by uniaxial isothermal compression tests at different temperatures and strain rates. The microstructural evolutions were also studied using electron backscatter diffraction. The flow stress decreases with the increasing temperature and decreasing strain rate. A constitutive equation was established to characterize the relationship among the deformation parameters, and the deformation activation energy was calculated to be 497.92 kJ/mol. Processing maps were constructed to describe the appropriate processing window, and the optimum processing parameters were determined at a temperature of 1107–1160°C and a strain rate of 0.005–0.026 s −1 . Experimental results showed that the main nucleation mechanism is discontinuous dynamic recrystallization (DDRX), followed by continuous dynamic recrystallization (CDRX). In addition, the formation of twin boundaries facilitated the nucleation of dynamic recrystallization.