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• Collaborative Optimization of Simplified Sections of steel/aluminum vehicle body. • Simplified Section was translated into Complex Section under Constraints of Sectional Mechanical Properties. • Optimization method for complex sections controlled by proportional vectors was established. A multi-level matching transformation and optimization design method for complex sections of thin-walled structures in steel/aluminum vehicle body skeleton was proposed. The problems of lengthy body performance numerical analysis and low optimization efficiency were solved by the rapid collaborative optimization of simplified cross-sections and performance of the body skeleton. A complex cross-sections shape library of thin-walled structures in steel/aluminum body skeleton and formulas for solving section mechanical properties were established, which overcame the difficulty of translating simplified cross-sections of thin-walled structures in steel/aluminum body skeleton to actual complex sections. A precise optimization method for complex cross-sections of thin-walled structure controlled by proportional vectors was established, which solved the defect that it was difficult to precisely control the arbitrary change of complex cross-section shape, and provided a new way for lightweight optimization design of complex cross-sections. The proposed method achieved the rapid collaborative design of steel/aluminum body thin-walled structure with complex cross-sections and body skeleton performance through multi-level progressive cross-section matching transformation and optimization. A body skeleton model with actual complex cross-sections was established, and compared with the initial simplified structure, the weight reduction ratio of the body skeleton was up to 6.9 %, and the performance indicators of the body skeleton fully met the design requirements, which verified the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Twinning-induced plasticity (TWIP) steel is an ideal material for impact-resistant structures and energy absorption because of its high product of strength and elongation. However, compared with other advanced high-strength steels, the relatively low yield strength of TWIP steel is one of the important shortfalls that significantly limits its engineering applications. To enhance the comprehensive properties of TWIP steel, a machine learning design strategy that integrated comparative modelling, SHAP analysis, and multi-objective optimization were adopted in this study. Initially, various machine learning algorithms were compared for their predictive accuracy based on normalized data (273 entries) regarding the microstructure and properties of TWIP steel. Then, performance prediction models for yield strength, tensile strength, and elongation were established. SHAP analysis was subsequently employed to assess the significance and explicit laws of composition and microstructures in these three target properties, identifying key elements that enhance the overall performance. Furthermore, two new TWIP steels with high yield strengths and high products of strength and elongation were developed via multi-objective optimization. Under conventional hot forging + hot rolling + cold rolling + annealing processes, the two designed TWIP steels had yield strengths of 585 MPa and 560 MPa, tensile strengths of 1055 MPa and 1101 MPa, elongations of 55% and 58.5%, and products of strength and elongation of 58.0 GPa% and 66.4 GPa%, respectively. The yield strengths of the designed TWIP steels significantly improved while maintaining a reasonable product of strength and elongation. This work provides important references for the rational development of new TWIP steels. [ABSTRACT FROM AUTHOR]

The research presented in this article consisted of analysis of the ship structural accidents at low temperatures and the effect of carbon percentage in various classifications of carbon steel, compared to the high tensile strength steel materials. The objective of this research was to fill the knowledge gap by expanding the understanding of the influence of low temperature, material, and structure on the axial compression test of tubes. The simulations as idealization of the compression test were conducted with variations in temperature, material carbon percentage, and geometry shape, using Finite Element Analysis (FEA). The results showed that at -100 °C, the material had the best ability to resist compression energy; high carbon steel had the highest strength at various carbon percentages, and the square geometry showed the best ability to absorb energy before failure. [ABSTRACT FROM AUTHOR]

This article discusses a numerical study on predicting the bond-slip relationship of reinforced concrete using surface-based cohesive behavior. The study aims to develop a finite element modeling strategy to accurately predict the bond-slip behavior in reinforced concrete. The article provides a comprehensive review of previous research on bond-slip behavior and includes a table of maximum bond stress equations from different literature sources. The document discusses the testing procedure and finite element modeling strategy for studying the bond behavior between concrete and reinforcement in pullout tests. The document also explains the loading and boundary conditions applied in the finite element model and the interaction between reinforcement and concrete. The text discusses the different contact models available in ABAQUS for simulating contact between surfaces. It concludes by discussing the finite element mesh size and solution procedure used in the study. The text discusses the results of finite element analysis (FEM) conducted on reference specimens to predict their failure modes and bond stress-slip behavior. The analysis used different mesh sizes and analytical models to simulate the behavior of the specimens. The results showed that a finer mesh size of 10 mm provided more accurate predictions of failure patterns, while a mesh size of 10 mm or larger could be used to estimate specimen strength. The FEM developed using the analytical model by Strum and Visintin showed the most accurate prediction of maximum bond stress. The failure modes observed in the analysis included pullout failure, splitting followed by pullout failure, and splitting or splitting-pullout failure. The FEM models generally performed [Extracted from the article]

This study investigates the seismic performance of built-up steel tubular (BST) columns composed of four mild-steel plates welded to four ultrahigh-strength steel (UHSS) tubes of Grade 1200, presenting a novel concept in column construction. The focus of this research is to evaluate the behavior of these columns under six degrees-of-freedom (6DOF) boundary conditions, replicating realistic loads induced by seismic events. A comprehensive experimental program was carried out at Swinburne University of Technology, including quasi-static (QS) cyclic and hybrid simulation (HS) tests. These experiments aimed to monitor the progression of physical damage and assess the hysteresis response of the columns, providing valuable insights into their stiffness, strength, and energy absorption capabilities. The results demonstrate the columns' reasonable seismic performance, indicating their potential use in ordinary moment-resisting frames within regions experiencing low–moderate seismic activity. [ABSTRACT FROM AUTHOR]

Significant advancements have been made in the area of composite structures. Aligned with an innovative design, the motivation behind this research is, first, to make efficient use of timber as an environmentally friendly material and, second, to employ steel alongside timber effectively to prevent buckling of the steel. This research aims to bridge this knowledge gap by exploring the integration of steel, carbon fiber–reinforced polymer (CFRP), and timber. The objective is to create innovative composite column structures that leverage the unique properties of each material to enhance structural performance and efficiency. The authors conducted tests on a set of 24 columns under compression conditions. The results of the structural tests demonstrated significant compression capacities relative to their mass, highlighting the significant advantages of material synergy within these elements. The study thoroughly quantifies these benefits, shedding light on the potentially transformative impact of these innovative composite columns in the field of structural engineering. A significant finding was the influence of the timber section's geometry on preventing column buckling. Furthermore, the positioning of steel within the sandwich columns played a vital role, with steel elements having a greater area with timber exhibiting enhanced structural performance and reduced likelihood of debonding. This paper introduces a new parameter, the inelastic transition area denoted as INT±70% peak , which characterizes the smoothness or abruptness of the transition once the inelastic region begins and the graph descends. This parameter bears significance in risk analysis for structures susceptible to progressive failure. All specimens displaying substantial energy absorption featured larger timber sections, highlighting the pivotal role of timber in absorbing higher levels of energy during structural loading. The findings contribute to the growing body of knowledge on composite materials and their applications in modern construction. [ABSTRACT FROM AUTHOR]

In this study the cold cracking (CC) susceptibility of naval grade high strength steel (HSS) welds developed using flux core wires of different yield strength levels was analyzed for lightweight shipbuilding structures. The steel plates of the PCE500 TM grade were welded in T-joint configuration using automatic flux core arc welding under the shielding gas. The CC susceptibility of weld metals was evaluated using Tekken weldability test. The microstructure of weld metal and the hardness of welded joint were analyzed using optical microscope and Vickers microhardness tester, respectively. Software package Sysweld was used for finite element simulation of CC susceptibility of weld metals. Results showed that the probability of CC increases with increase in the strength of filler wires, especially under conditions of limited welding deformations and exposure to low temperatures. The maximum resistance to the formation of cold cracks (CCs) in microstructure of the weld metal is observed in the presence acicular ferrite of at least 60%. To assess the structural strength of T-joint with soft welds, a calculation method has been developed, which allows ranking various structural and technological solutions of the T-joint from the condition of resistance to various types of fracture. Numerical calculation showed that the margin for brittle fracture at 11e23% and the gain in fatigue durability at 40% for welded joint with soft weld greater than for a welded joint with an equally strong weld. The use of low strength filler wires for welding thick plates of HSSs can successfully resolve the problem of CCs and ensure structural strength of joints. [ABSTRACT FROM AUTHOR]

Faced with the rapid development of large-scale pumped-storage power stations, the trade-off between the strength and toughness of hydropower steels in extreme environments has been limiting their application. The effects of Nb micro-alloying and direct quenching and tempering processes on the strengthening–toughening mechanism of 1000 MPa grade high-strength hydropower steel are studied in this paper, and the precipitation behavior of Nb is discussed. The results showed that only the 0.025Nb steel using the DQT process achieved a cryogenic impact energy of more than 100 J at −60 °C. Under the DQT process, a large number of deformation bands and dislocations were retained, refining the prior austenite grains and providing more nucleation sites for the precipitation of NbC during the cooling process. The DQT process has a more obvious local strain concentration, mainly focusing on the refined lath boundary, which indicates that the refinement of the microstructure also promotes the stacking of dislocations. The improvement in fine grain strengthening and dislocation strengthening by the DQT process jointly led to an increase in strength, resulting in a better combination of strength and toughness. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM), specifically Directed Energy Deposition (DED)-Arc, holds great potential for the fabrication of individually designed components. In the construction industry, the demand for tailored steel nodes is increasing, particularly for large-scale structures, where high-strength steel deployment can significantly reduce material consumption and production time. However, the thermal material deposition process has a strong impact on the technical properties of high-strength steel. Parameters like heat input, interpass temperature (IPT), and cooling strategies modulate cooling times and peak temperatures in thermal cycles, which are crucial for estimating mechanical properties indispensable for safety certification. The development of digital twins or digital shadows emerges as the primary approach for quality assurance and certification, deploying real-time monitoring of manufacturing parameters such as voltage, current, wire feed, thermal history, and bead shapes. This data can be correlated with specific regions in the fabricated part to draw quality inferences. To interpret this data effectively, an understanding of the influence of these process parameters on resultant properties is indispensable. Given that the resulting microstructure strongly depends on the thermal history in AM parts, temperature monitoring during DED-Arc using thermography emerges as a promising method. This article aims at providing fundamental knowledge about phase transformations of a high strength steel feedstock under repeated reheating and gaining comprehensive knowledge about microstructural evolution during DED-Arc Additive Manufacturing. This is done by the analysis of time-temperature profiles, resulting microstructure and mechanical properties, linking it to CCT diagrams. A novel approach for describing the degree of tempering in different regions of the samples by deploying tempering parameters for anisothermal heat treatments is presented. By using this approach, an estimation about the resulting microstructure and hence the mechanical properties can be drawn.

The underwater 10CrNi3MoV high-strength low-alloy steel thin-walled part with forming quality up to in-air laser deposition quality was successfully manufactured for the first time. The influencing mechanisms of complicated thermal history and water environment on microstructure evolution and mechanical properties of thin-walled part were researched. Due to austenitization and interlocking effect, the microstructure in the bottom, middle and top (below the 56th layer) areas of underwater sample and the middle area of in-air sample were composed of fine grain ferrite and granular bainite. With the increase of building height, the heat accumulation effect of underwater sample enhanced, resulting in small grain size (GS), high dislocation density, strong solution strengthening effect and low maximum texture strength at the bottom area, while the high proportion of high-angle grain boundaries (HAGBs) at the top area. These resulted in the greatest tensile strength (714 MPa) and microhardness (232 HV) at the bottom area and the highest elongation (11%) at the top area. Due to the cooling effect of water environment, the proportion of HAGBs reduced and there were oxides in fracture. As a result, the horizontal elongation of underwater sample was about 90.9% of in-air sample. Additionally, the GS reduced, and the dislocation density and solution strengthening effect increased, so the microhardness of underwater sample was slightly higher than that of in-air sample. However, due to some microscopic defects, the horizontal and vertical tensile strength of underwater sample were about 97.6% and 90.7% of in-air sample.

Nature has long inspired technological innovations, fostering the rapidly developing field of bionics. Inspired by the microstructure of bamboo, we have developed a bamboo-like structure for steel. This novel steel achieves a tensile strength exceeding 1200 MPa and a uniform elongation nearing 68%, resulting in a product of strength and uniform elongation up to 83 GPa·%. The high strength of the steel is primarily attributed to its ultra-fine lamellar grains. Additionally, the graded occurrence of multiple deformation mechanisms collectively maintains its exceptional work-hardening capability. This study presents a new approach to enhancing the performance of medium-Mn steels. Impact Statement: A bamboo-like steel consisting of lamellar ferrite and austenite alternating along the rolling direction, providing a new path to produce medium-Mn steels with outstanding mechanical properties. [ABSTRACT FROM AUTHOR]

This study investigated the V-bending process of 1.2 mm thick SCGADUB1180 advanced-high-strength steel sheet plate by experimental and finite element method, and its springback behaviour was investigated in detail. In the experiments, 27 different V-bending experiments were modeled in three different punch radii (3mm, 6mm, 9mm), three different bending angle values (60°, 90° 120°), three different rolling directions (0°, 45°, 90°). In the experiments created with these input parameters, the effect of the sheets on the springback was investigated by comparing the experimental data with different material models. 108 analyses were performed for four different finite element models (Hill-48, Barlat-89, Hill-48-kinematic, Barlat-89-kinematic). It was analyzed that the Barlat-89-kinematic strain hardening model was the closest model to the experimental results. In addition, with the help of the Minitab 18.0 statistics program, how well the finite element model data agreed with the experimental results was analyzed. It was observed that the variation of punch radius (83.03%) and bending angle (8.51%) had a significant effect on the springback behaviour of the sheet. As the punch radius increased, the springback values increased. At the highest parameter level, where the bending angle was 120°, the springback values decreased. The highest springback occurred at 90° bending angle.. [ABSTRACT FROM AUTHOR]

Considering the advantages of hybrid steel I-section beams in reducing engineering costs and fully utilizing the mechanical properties of steel, and the lack of research on their ductility, hybrid steel I-section beams were tested to analyze the effects of the plate width–thickness ratio and steel strength matching on the flexural bearing capacity and ductility. The steel strength matching of the hybrid steel I-section beam with a high steel strength utilization rate and good ductility was related closely to the section size. Additionally, a parametric analysis based on the finite- element method was performed for further study. The steel strength ratio φ of the web to the flange with the best ductility was less than 1, and φ decreased with an increase in flange steel strength. The steel strength utilization rate and ductility decreased with an increase in φ. Based on the parametric analysis results, the optimal range of φ in hybrid-steel I-section beams with flange steel strength of 460–690 MPa was 0.56–1. The plate width–thickness ratio limit of the ductile section decreased with the decrease of φ. Considering the plate interaction and steel strength matching, a sectional ductility design method is proposed that is more applicable to hybrid steel I-section beams than existing methods. [ABSTRACT FROM AUTHOR]

The increasing demand for lightweight vehicles, while ensuring collision safety, has led to the growing utilization of high-strength steel sheets. Accordingly, the hot stamping process, which involves heating the material and shaping it in a die while simultaneously cooling it, has gained significant attention. However, the inclusion of heating and cooling processes in the hot stamping engineering presents competitive disadvantages in terms of cost. As a result, numerous studies are being carried out to overcome these challenges and improve productivity. In particular, the sidewall areas of the vehicle body parts, which thin out during the stamping process, can experience a reduced cooling rate compared to other areas. To counteract the potential risk of a relative decrease in strength in these areas, extending the pressurization time of the press becomes necessary. In this study, by introducing groove patterns on the surface of the die used in the hot stamping forming and cooling processes, it was investigated how to enhance the cooling rate of the sidewall of the vehicle part without necessitating additional press dwell time. Using this approach, it was possible to achieve a strength of over 1.6 GPa and a dimensional accuracy of -0.06 mm within a short in-die quenching time of 6 s. [ABSTRACT FROM AUTHOR]

The Modified Mohr–Coulomb criterion has been demonstrated to exhibit high accuracy in the prediction of fracture in high-strength steels. Taking DP780 as the research object, the undetermined parameters of the Modified Mohr–Coulomb criterion at different temperatures were calibrated by tensile and shear tests combined with simulation. The relationships between the parameters and temperature were investigated. Finally, the relationship between criterion parameters and temperature was verified using the stretch-bending tests of U-shape parts. The fracture of automotive parts can be accurately predicted by simulation during warm stamping, thereby guiding actual production. [ABSTRACT FROM AUTHOR]

In the present work, a study of the fatigue strength of two materials widely used in the production of molds, namely, the AISI P20 and AISI H13 steels, is presented. The tests were performed at a constant amplitude with a stress ratio of R = 0 using samples where U-shaped notches were filled with laser beam fusion deposition. Three different sets of deposition parameters for each material were analyzed. Fatigue strength results are presented as S-N curves obtained for filled and non-filled materials. In addition to the assessment of the fatigue strength, metallography, hardness, and the fracture surface of the specimens tested were also evaluated. In general, a high number of metallurgic defects was detected, and consequently, a decrease in the mechanical properties of the materials was observed, especially the fatigue strength. However, the parameter optimization of the repairing laser process produced repaired zones with good metallurgical quality, leading to higher fatigue strength in both of the high-strength steels analyzed. [ABSTRACT FROM AUTHOR]

Surface selective oxide layer on continuous annealed steels is difficult to analyze because of its thickness in nanometer scale, but it tremendously affects the properties of the coatings. Detailed photographs about the morphology, distribution and relative surface coverage of different oxides are still limited in relevant literature. With the method of carbon extraction replicas, such oxides are extracted from dual-phase high strength steels and Ti-stabilized interstitial free steel, and they are analyzed by transmission electron microscope (TEM) with energy-dispersive spectroscopy (EDS) and selected area electron diffraction (SAD) attachments. Their chemical composition, crystal structure, size, morphology and distribution are investigated in detail. Four different ternary oxides including Mn2SiO4, MnCr2O4, MnAl2O4 and Mn2TiO4 are extracted and confirmed in both crystal structure and chemical compositions. MnAl2O4 and Mn2TiO4 on steel surface are identified by single-crystal SAD and EDS techniques. MnCr2O4 is confirmed to have similar chemical compositions and crystal structure with reported literature but different particle size and location observed. Mn2SiO4 along the grain boundaries is also photographed in low Si content of 0.2–0.7 wt% steels, which is usually reported in high Si-containing steels and low Mn/Si ratio. Among all these oxides, Mn2SiO4 is bigger than the others. [ABSTRACT FROM AUTHOR]

This study presents a solution for push-out failure for the staged bond-slip constitutive relationship between the structural steel and high strength concrete, taking into account the concrete strength grade, anchoring length, and stirrup ratio. The critical point coordinates for different stages are determined by the tests of 14 steel-reinforced high strength concrete (SRHSC) specimens. It is observed that with the increase in the concrete strength grade and anchorage length, the ultimate load of the specimens increased significantly, but the influence on the residual bond strength was not significant. The effect of the stirring ratio was mainly manifested in a slight increase in the initial bond strength. The formula for calculating SRHSC characteristic bond strength and characteristic slip value is established, and the bond-slip constitutive relation of SRHSC is proposed based on the tests. The material constitutive model considering the effect of bond-slip is implanted into the software in the case of the ABAQUS finite element platform. The material is applied to the numerical simulation analysis of the SRHSC exterior joints. The rationality and accuracy of the new material are verified by comparing the simulation results with the test results. [ABSTRACT FROM AUTHOR]

Expansive soil is one of the problematic soil types due to its potential to swell highly when moisture content increases and shrink when moisture decreases. The soil exhibits mechanical behavior that is highly sensitive to changes in natural moisture content influenced by environmental factors such as infiltration and evaporation. It has the potential to damage civil structures such as road pavement and lightweight buildings. An alternative method to overcome this phenomenon is the use of ground anchors, a structural element installed into a soil or rock layer to withstand the tension load. An expandable ground anchor is proposed as an alternative to overcome the drawback of a helical anchor. Wings are installed in such a way that additional passive pressure is developed. The study was firstly conducted by performing anchor pullout capacity tests on a dense sand layer, followed by a swelling test of expansive soil, and finally, the performance test of ground anchor to withstand swelling pressure using three different sizes of steel box anchor prototypes, 4 cm × 4 cm × 30.5 cm, 5.5 cm × 5.5 cm × 30.5 cm and 7 cm × 7 cm × 30.5 cm. A series of anchor pullout capacity tests were conducted on a 90 cm dense sand layer, continued by a swelling test of 25 cm expansive. The result indicates that an expandable anchor can significantly withstand the swelling of expansive soil. [ABSTRACT FROM AUTHOR]

The main goal of this study is to examine the buckling properties of a composite material that combines graphene-origami-enabled features with magnetostrictive facesheets. The nonlocal theory, as developed by Eringen, has been used for the purpose of quantifying the small-scale parameter. However, the system being presented is based on the theoretical framework established by Winkler and Pasternak, which incorporates the analysis of a deformable medium. The use of a theoretical framework referred to as higher-order sinusoidal shear deformation theory has been utilized to formulate the governing equation. The governing equation is then solved via the Galerkin solution approach, while considering various boundary conditions. In order to assess the precision and effectiveness of the present inquiry, the findings are juxtaposed with the prevailing scholarly publications in the academic literature. Furthermore, this study aims to examine the impact of several factors, including as the weight fraction, hydrogen atom coverage, aspect ratio, and temperature, on the critical buckling load. The findings of the present investigation indicate that an increase in the weight fraction of graphene-origami-enabled material leads to an increase in the buckling load. The main aim of this study is to improve the understanding and predictive capability of engineers and designers about the phenomenon of buckling response. The aforementioned data have the potential to provide advantages in the advancement of nanoscale systems, including highly sought-after technologies such as sensors and actuators. [ABSTRACT FROM AUTHOR]

With the continuous integration of semiconductor devices, the requirements of the size accuracy and surface quality of etched lead frames are stricter. The etchant is a key factor in the etching process and etched surface quality, while the effects of the difference in etchants on the etched surface morphology of Cu alloy have not been directly studied. In this study, aqua regia, acidic FeCl3 and two CuCl2 solutions were used as etchants, and different CuCrSn specimens were etched and characterized. The results show that the etching rate in aqua regia is high, and the grain orientation, grain boundary (GB) and dislocations have significant influences on the local etching rate. The preferential etching of some atomic planes forms steps between the grains with different orientations, and preferential etching around the GB and dislocation group forms grooves, resulting in high surface roughness. For the surfaces etched by the FeCl3 and CuCl2 etchants, the steps and grooves are blurred; thus, they are less rough. The CuCrSn alloy surface etched by the aqua regia is clean, with little Cr-rich particles, while high-density Cr-rich particles remain on the surfaces etched by the FeCl3 and CuCl2 etchants. For the same kind of etchant, the ion concentration can affect the etching mechanism, rate and the etched surface morphology. [ABSTRACT FROM AUTHOR]

Considering the high-speed and high power density technical specifications of new energy vehicle motors, there is a growing demand for rotor strength as motor peak speeds reach 20,000 r/min and beyond. The utilization of non-oriented silicon steel with a high yield strength in rotors has emerged as a promising approach to increase motor speed. However, the magnetic and mechanical properties of high-strength silicon steel under variable temperature conditions have not been fully explored, particularly in regards to their impact on motor torque, efficiency, and speed. This manuscript investigates the behavior of high-strength silicon steel before and after annealing and at different temperatures, analyzing its influence on high-speed motor performance. The validity and feasibility of this study are confirmed through prototype testing, providing a comprehensive reference for engineering design. [ABSTRACT FROM AUTHOR]

A systematic study is performed on the development of hot-dip galvanized coatings on a Mn-containing high-strength steel sheet by varying the dew point (− 50, − 10, and + 10 °C) during inter-critical annealing of the steel strip at 800 °C. It also studies the effect of dew point on the corrosion behavior of the coatings in freely aerated 3.5 wt% NaCl solution. The reducing gas atmosphere consists of 95% N2 and 5% H2, where inter-critical annealing is carried out. Surface oxidation of the steel has a strong effect on the development of sound coating. A defect-free adherent galvanized coating is obtained on the annealed steel surface at a fixed dew point of + 10 °C, and it is attributed to the fine and continuous compact Fe-Al crystals compared to galvanized coatings produced at other dew points as well as the highest atomically dense (0002) basal plane. This also leads to the lowest corrosion rate (~ 0.164 mm y−1, where mm and y stand for millimeter and year, respectively) of the galvanized coating produced at a dew point of + 10 °C when compared with galvanized coatings produced at dew points of − 50 °C (~ 0.279 mm y−1) and − 10 °C (~ 0.259 mm y−1). The lowest corrosion rate of the galvanized specimen developed at + 10 °C dew point can be attributed to the uniform and defect-free coating surface, together with the dominance of the more atomically dense (0002) basal plane. [ABSTRACT FROM AUTHOR]

The absence of analytical expressions in current codes for evaluating the critical moment for lateral–torsional buckling of cold-formed beams with omega-shaped sections presents a fundamental challenge when assessing their resistance to global buckling. In response to this challenge, a comparative study was conducted to explore various approaches for calculating the critical moment. This involved both analytical and numerical analyses, using different methods available in codes and computational tools. The analytical analysis followed the Effective Width Method, employing the expression proposed in ENV 1993-1-1:1992, which is commonly used for evaluating the critical lateral–torsional moment of hot-rolled profiles. Numerical analyses were then performed using the ABAQUS v6.13, GBTUL v2.0, and CUFSM v5.05 software packages. The ABAQUS model, validated with results obtained from an experimental campaign, serves as the reference model. Upon assessing the bending moment resistances according to European, Brazilian, and American standards, consistency was found among these standards. However, it became evident that using the analytical expression proposed for hot-rolled profiles is inadequate for evaluating the critical lateral–torsional moment of CFS omega-shaped profiles. Conversely, the agreement between the ABAQUS, GBTUL, and CUFSM results suggests their utility as reliable tools for estimating the elastic critical lateral–torsional buckling moment. [ABSTRACT FROM AUTHOR]

Hydrogen embrittlement (HE) continues to be a limiting factor in implementing high strength steel alloys in applications such as fasteners. In this work, 9260 bar steel was heat treated to produce quench and tempered (Q&T) martensite and quench and partitioned (Q&P) microstructures at hardness levels between 52 and 54 HRC. The Q&P microstructures consisted of lath martensite, retained austenite, martensite-austenite (M/A) constituents, and intercritical ferrite in some conditions. The Q&P process promoted higher strength and uniform elongation than the Q&T martensite, though also exhibited a relatively low degree of post-uniform elongation except in the lowest quench temperature condition. Slow strain rate tensile and circular notch tensile tests were performed on all conditions after electrochemical hydrogen charging at hydrogen levels of 1–1.5 ppm. The Q&T condition exhibited a better slow strain rate performance and notch tensile strength after hydrogen pre-charging than the Q&P conditions. In the Q&P conditions subjected to slow strain rate tensile tests, a higher HE susceptibility is correlated with higher quench temperatures, which had lower austenite stability and more fresh, non-tempered martensite in the initial microstructure. However, the HE susceptibility was comparable for all of the Q&P conditions in the notch tensile tests. [ABSTRACT FROM AUTHOR]

Medium-carbon, high-strength steels are widely used in the field of hydrogen energy because of their good mechanical properties, and they can be readily tailored by heat treatment processes such as the normalizing–tempering (N&T) and quenching–tempering (Q&T) methods. The hydrogen embrittlement (HE) susceptibility of a medium-carbon, high-strength steel was investigated utilizing microstructural characterization with scanning electron microscopy (SEM), the electron backscatter diffraction (EBSD) technique, and transmission electron microscopy (TEM). A study was also conducted on the steel's hydrogen transport behavior as affected by the N&T and Q&T treatments. The steel contained more hydrogen traps, such as dislocations, grain boundaries, lath boundaries, and carbide interfaces, after the Q&T process, which was associated with a lower HE sensitivity when comparing the two treatments. In comparison, the N&T process produced larger-size and lesser-density carbides distributed along the grain boundaries, and this resulted in a relatively higher HE susceptibility, as revealed by the slow-strain-rate tensile (SSRT) tests of the hydrogen-charged steels and by the fractographic study of the fracture surface. [ABSTRACT FROM AUTHOR]

Over the past several decades, conventional spectral analysis techniques of polluted white dwarfs have become powerful tools to learn about the geology and chemistry of extrasolar bodies. Despite their proven capabilities and extensive legacy of scientific discoveries, these techniques are, however, still limited by their manual, time-intensive, and iterative nature. As a result, they are susceptible to human errors and are difficult to scale up to population-wide studies of metal pollution. This paper seeks to address this problem by presenting cecilia , the first machine learning (ML)-powered spectral modelling code designed to measure the metal abundances of intermediate-temperature (10 000 ≤ T eff ≤ 20 000 K), Helium-rich polluted white dwarfs. Trained with more than 22 000 randomly drawn atmosphere models and stellar parameters, our pipeline aims to overcome the limitations of classical methods by replacing the generation of synthetic spectra from computationally expensive codes and uniformly spaced model grids, with a fast, automated, and efficient neural-network-based interpolator. More specifically, cecilia combines state-of-the-art atmosphere models, powerful artificial intelligence tools, and robust statistical techniques to rapidly generate synthetic spectra of polluted white dwarfs in high-dimensional space, and enable accurate (≲0.1 dex) and simultaneous measurements of 14 stellar parameters – including 11 elemental abundances – from real spectroscopic observations. As massively multiplexed astronomical surveys begin scientific operations, cecilia 's performance has the potential to unlock large-scale studies of extrasolar geochemistry and propel the field of white dwarf science into the era of Big Data. In doing so, we aspire to uncover new statistical insights that were previously impractical with traditional white dwarf characterization techniques. [ABSTRACT FROM AUTHOR]

Various industries, including mechanical engineering, utilize steel rings featuring variable cross-sectional profiles, such as eccentric rings. Presently employed methods for producing eccentric rings possess drawbacks like restricted geometries, significant material wastage or uneven microstructures. The radial–axial ring rolling process serves to create seamless rolled steel rings with near-net-shaped cross-sections. A novel technique involves achieving eccentricity by dynamically adjusting the mandrel's position during the ring rolling process. This method's fundamental feasibility has previously been showcased using a blend of oil clay and a labor test bench. Transferring the possibility of manufacturing eccentric rings on industrial radial–axial ring rolling mills would expand the product range of ring manufacturers without encountering drawbacks associated with existing manufacturing processes. The objective of this paper is to demonstrate the basic feasibility of the concept of an industrial radial–axial ring rolling mill. In the first step, FEA simulation studies were carried out to develop the rolling strategy and estimate the achievable eccentricity on the institute's radial–axial ring mill. Subsequently, the rolling strategy was implemented on an industrial ring rolling mill with the help of a unique technology module programmed in C++. Finally, an eccentric ring was ring rolled and compared with the FEA simulation, and the reproducibility was demonstrated to be successful. [ABSTRACT FROM AUTHOR]

The door of a passenger car is one of the key components used for the safety of passengers from side collisions. Mostly car doors are made of Steel that increase the overall weight of the vehicle since steel is the primary metal used for the construction of door. The main objective of this research is to replace Steel material of a car door with low-cost automotive materials such as aluminium alloy, magnesium alloy, and carbon fibre material to perform weight reduction analysis without compromising the strength and safety. A comprehensive theoretical study of the existing car door has been performed with 3D Computer-Aided Design (CAD) models through commercially available software SolidWorks. Results of this research work revealed that by selecting the appropriate engineering materials of the doors for a commercially available passenger car, the overall weight reduced to 45% when used aluminium material and 64% when used magnesium and carbon-fibre materials compared to the total weight of four doors made of typical steel material. Furthermore, reduction in fuel consumption and CO2 emission was also obtained by reducing the overall weight of the passenger car doors. Lastly, the performance was measured through power-to-weight ratio (PWR) analysis for steel and aluminium which revealed that the latter material was more economical and lighter in weight than the former material. [ABSTRACT FROM AUTHOR]

The derived diagram defines three main ranges of hydrogen concentration in the metal, which have their own specific mechanisms of hydrogen influence on the characteristics of strength and ductility of the pipeline steel. It has been demonstrated that the nature of the hydrogen effect mechanism depends on the ratio of diffusible C H dif and residual (trapped) hydrogen C H res in the steel. A specific effect has been found, namely: at the hydrogen concentration C H ≅ 0.01 - 0.2 ppm where all hydrogen is practically diffusible, the plastic deformation of the steel is facilitated, i.e., the deforming of the material takes place more easily. At the concentration range C H ≅ 0.8 - 10 ppm , where the trapped hydrogen prevails, the mechanism of hydrogen embrittlement of the steel is completely dominated. Therefore, the hydrogen concentration range beginning from C H ≅ 0.8 ppm can be considered as critical. The range of values of hydrogen concentration in the metal C H ≅ 0.2 - 0.8 ppm is a transition zone where the simultaneous coexistence of these two mechanisms is possible. The constructed diagram can be applied for the interpretation of the inspection results of long-term operated pipelines, and also for the choice of materials for the construction of new networks for hydrogen transportation. [ABSTRACT FROM AUTHOR]

In this study, the effect of steel rolling technique, temperature, yield strength and welding heat input on the impact toughness of high-strength steels is studied. The impact toughness of five kinds of high strength steels with yield strength of 550 MPa, 690 MPa and 890 MPa are experimentally studied. The standard Charpy V-notch test is carried out and the absorbed energy AKV of the test specimens is obtained. The test results show that the impact toughness of QT550 high-strength steel is not sensitive to temperature and it also has good impact performance at low temperature. For other high strength steels, with increase of steel strength, the impact toughness is severely degraded with decreasing temperature. For the effect of rolling technique on impact toughness, the QT type high-strength steel generally follows the law that the impact toughness deteriorates with the increase of the yield strength. QT process can produce better impact resistance than TMCP process for 690 grade steel. The effect of temperature on the impact toughness of WM is intensified at high heat input. The impact toughness of the base material (BM), heat-affected zone (HAZ) and weld metal (WM) deteriorates with the rise of the yield strength. QT550 and QT690 show different impact characteristics for HAZ and WM. The former HAZ has better impact performance under high heat input while WM is better under low heat input; both HAZ and WM of QT690 show higher impact toughness under low heat input.

This study combines experiments with finite element simulations to investigate the effects of different forging ratios on the properties and microstructure of high strength steel 40CrNi2Si2MoV. The results indicate that under high forging ratios, the peak of the austenite phase is significantly reduced, while the peak of the martensite phase becomes dominant, accompanied by an increase in dislocation density, strength, and hardness. The uniform distribution of newly formed small-angle martensite grains enhances both strength and plasticity. The excellent strength and toughness of high-strength steel under high forging ratios mainly depend on tempered martensite and retained austenite. The impact toughness of under a high forging ratio increases by nearly 1.23 times compared to the lower forging ratio. Additionally, the ultimate tensile strength increases by 1.02 times, the microhardness rises by 2.25 %, while the elongation decreases by 0.65 %. Fracture morphology analysis reveals that heightened forging ratios not only ensure a more uniform dispersion of carbides within the matrix but also significantly boost crack propagation resistance, thus enhancing the impact toughness of the experimental steel. The study utilizes finite element software to assess the influence of equivalent stress, equivalent strain, temperature fluctuations, and damage progression on the mechanical properties during the forging process. This comprehensive analysis establishes a robust theoretical framework aimed at optimizing both the forging process and subsequent heat treatment structures and properties of high strength steel 40CrNi2Si2MoV.

AbstractWire arc additive manufacturing (WAAM) processes have many advantages including the ability to repair worn or damaged components. Compared to other arc processes, plasma welding constricts the arc, which leads to a highly concentrated energy input. Thus, an understanding of the heat input distribution and its consequences such as transient temperature field, transformation, build up of stresses, and distortion is of great importance for applications with high-strength steels. Numerical simulation can provide an important input for this evaluation. However, the plasma arc is challenging to simulate due to its high energy density and thus steep gradients, as standardly used heat sources in commercial software often only represent classical arc or beam processes. Therefore, this study deals with the development of an accurate heat source model based on standard implemented heat sources in Simufact Welding. Therefore, welding experiments were performed on steel and thermal cycles representing the quasi-­stationary temperature field were recorded. Subsequently, metallographic examinations were performed describing the fusion and heat-affected zone. On this basis, distortion simulations were carried out and validated using further welding experiments. Using the obtained results, path planning, idle time, and consequently interpass temperatures and the resulting heat flow can be analysed.

High-carbon hardline steels are primarily used for the manufacture of tire beads for both automobiles and aircraft, and vanadium (V) microalloying is an important means of adjusting the microstructure of high-carbon hardline steels. Using scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM), the microstructure and precipitation phases of continuous cooled high-carbon steels were characterized, and the vanadium content, carbon diffusion coefficient, and critical precipitation temperature were calculated. The results showed that as the V content increased to 0.06 wt.%, the interlamellar spacing (ILS) of the pearlite in the experimental steel decreased to 0.110 μm, and the carbon diffusion coefficient in the experimental steel decreased to 0.98 × 10−3 cm2·s−1. The pearlite content in the experimental steel with 0.02 wt.% V reached its maximum at a cooling rate of 5 °C·s−1, and a small amount of bainite was observed in the experimental steel at a cooling rate of 10 °C·s−1. The precipitated phase was VC with a diameter of ~24.73 nm, and the misfit between ferrite and VC was 5.02%, forming a semi-coherent interface between the two. Atoms gradually adjust their positions to allow the growth of VC along the ferrite direction. As the V content increased to 0.06 wt.%, the precipitation-temperature-time curve (PTT) shifted to the left, and the critical nucleation temperature for homogeneous nucleation, grain boundary nucleation, and dislocation line nucleation increased from 570.6, 676.9, and 692.4 °C to 634.6, 748.5, and 755.5 °C, respectively. [ABSTRACT FROM AUTHOR]

This paper adopted the new process of double-sided oscillation laser autogenous backing welding and double-sided oscillation laser–TIG hybrid filling welding to achieve 80 mm thick SA-738Gr.B steel narrow gap welding in the horizontal position. The microstructure, mechanical properties, and residual stress of the welded joints in the as-welded (AW) state and in the post-weld heat treatment (PWHT) state were analyzed comparatively. The results show that because of the high-temperature tempering effect of PWHT, the microstructure of the welded joint is transformed into a high-temperature tempered microstructure with the increase in alloy carbide precipitation. The grains growth of the backing weld and the base material is obvious. The relative frequency of the high-angle grain boundary of the weld increases. Under the PWHT, the tensile strength of the welded joint decreases, and the residual stresses of the welded joint are redistributed and reduced significantly. [ABSTRACT FROM AUTHOR]

In this paper, the corrosion environment of a railway coal truck was simulated with 1.0%H2SO4 + 3%NaCl solution. The effect of weld toe Tungsten Inert Gas (TIG) remelting on the microstructure and corrosion resistance of welded joints of Q450NQR1 high-strength weathering steel was studied. The results show that the weld toe melts to form a remelting area after TIG remelting. After TIG remelting, the weld geometry was improved, and the stress concentration factor decreased from 1.17 to 1.06 at the weld toe, a decrease of 9.4%. TIG remelting refines the microstructure of the weld toe and improves the corrosion resistance of the welded joint. The surface of the TIG-remelted sample is uniformly corroded with no "deep and narrow" pits after the removal of corrosion products. The weight loss rate and corrosion rate of remelted welds are lower than those of unremelted welds. The structure of corrosion products is loose at the initial stage of corrosion, and the corrosion products are transformed into Fe3O4 and Fe2O3 protective rust layers with a dense structure after 480 h of corrosion. With the extension of corrosion time, the tensile strength and percentage elongation of the specimen decreased linearly. The decreasing rates of tensile strength of remelted and unremelted specimens were 0.09 and 0.11, respectively, and the decreasing rates of elongation after fracture were 0.0061 and 0.0076, respectively. [ABSTRACT FROM AUTHOR]

The influence of varying the manganese (Mn) contents of high-strength copper-containing hull steel on its microstructural evolution and mechanical properties was investigated. With increasing Mn content from 2 to 5%, the tensile strength of the steel increased by ~100 MPa, while the elongation of steel remained at ~23.5%, indicating good plasticity. However, the 2Mn sample had 128 J higher low-temperature (−84 °C) impact work than the 5Mn sample. The microstructures of different Mn steels were composed of fresh martensite (FM), ferrite/tempered martensite (F/TM), and reversed austenite (RA). The increase in Mn content markedly increased the presence of RA and intensified the work hardening caused by the transformation-induced plasticity (TRIP) effect during the tensile process. However, as the phase transformation in different Mn steels occurred in the early stage of strain and did not extend throughout the entire plastic deformation process, increasing plasticity via phase transformation was difficult. In addition, although the volume fraction of RA increased significantly in 4Mn and 5Mn steels, the stability of RA significantly decreased. The presence of numerous metastable blocks and coarse lath-like RA contributed little to low-temperature impact work and was even detrimental to toughness. The substantial fresh martensite resulting from phase transformation facilitated microcrack generation, owing to rapid volume expansion and mutual impacts, thus reducing the work required for crack formation. Additionally, the abundance of deformation twins significantly reduced the work needed for crack propagation. These combined actions significantly reduced the low-temperature toughness of 4Mn and 5Mn steels. [ABSTRACT FROM AUTHOR]

Process maps were developed using a combination of microstructural analysis and DICTRA-based modeling to predict the austenite vol.% as a function of the intercritical annealing parameters and starting microstructure. The maps revealed a strong dependence of the calculated austenite fraction (vol.%) on the Mn content (4–12 wt.%) and intercritical annealing temperatures (600 °C to 740 °C). The calculations were carried out for constant carbon, Al, and Si contents of 0.2 wt.%, 1.5 wt.%, and 1.0 wt.%, respectively. A modified empirical equation proposed by Koistinen and Marburger was employed to calculate the room-temperature retained austenite vol.% as a function of the intercritical annealing temperature, including the effect of the austenite composition. The process maps offer valuable insights for designing intercritical treatments of medium-Mn steels, aiding in the optimization of steel properties for automotive applications. [ABSTRACT FROM AUTHOR]

Cutin, one of the main structural components of tomato peels, is a waxy biopolymer rich in hydroxylated fatty acids. In this study, 10,16-dihydroxyhexadecanoic acid (10,16-diHHDA) was extracted and isolated from tomato peels and exploited to develop fully crosslinked polyesters as potential candidates for replacing fossil-based metal protective coatings. A preliminary screening was conducted to select the base formulation, and then a design of experiments (DoE) was used as a methodology to identify the optimal composition to develop a suitable coating material. Different formulations containing 10,16-diHHDA and other biorefinery monomers, including 2,5-furandicarboxylic acid, were considered. To this end, all polyesters were characterized through differential scanning calorimetry (DSC) and gel content measurements to determine their Tg value and crosslinking efficiency. Compositions exhibiting the best trade-off between Tg value, chemical resistance, and sufficiently high 10,16-diHHDA content between 39 and 48 wt.% were used to prepare model coatings that were characterized for assessing their wettability, scratch hardness, chemical resistance, and adhesion to metal substrates. These polyester coatings showed a Tg in the range of 45–55 °C, a hydrophobic behavior with a water contact angle of around 100°, a good solvent resistance (>100 MEK double rubs), and an adhesion strength to steel higher than 2 MPa. The results obtained confirmed the potential of cutin-based resins as coatings for metal protection, meeting the requirements for ensuring physicochemical properties of the final product, as well as for optimizing the valorization of such an abundant agri-food waste as tomato peels. [ABSTRACT FROM AUTHOR]

Owing to the non-uniform distribution of chemical composition and temperature during the heat treatment process, the residual stress and deformation of the workpiece emerge as crucial factors requiring consideration in managing the service performance and lifespan of shield machine cutter rings crafted from H13 steel. Considering H13 steel with titanium microalloying as the research object for the shield machine cutter ring, we simulate the quenching process using Deform-3D. The temperature field, phase transformation, stress evolution, and deformation amount after quenching are analyzed. The results demonstrate a strong agreement between the simulation and experimental results, offering valuable insights for optimizing the heat treatment process and enhancing the overall performance of shield machine cutter rings. [ABSTRACT FROM AUTHOR]

As an innovative building system, the modular steel structure demonstrates a high degree of industrialization and assembly efficiency. However, no linkage exists between the components of modular units, leading to issues such as diminished load capacity and excessive steel usage in modular construction. In order to tackle these challenges, finite element numerical simulations are employed to examine the inter-column connectors and the cooperative modular steel buildings. This simulation calculates the initial stiffness across various degrees of freedom in these connectors. In addition, it analyzes the displacement response, changes in internal forces, and height of cooperative modular steel structures under varying seismic precautionary intensities. The results revealed that cooperative modular steel buildings substantially improve overall stiffness and lateral performance compared to their non-cooperative counterparts. There is a maximum reduction in the inter-story displacement angle of up to 36.1%, and the maximum reduction of the top displacement can reach 16.2%. This enhancement also increases structural stiffness, a shortened natural vibration period, and an augmented bottom shear force. Based on these findings, it is advised that the height of cooperative modular steel buildings should not exceed 21 m at 7 degrees (0.10 g), 21 m at 7 degrees (0.15 g), and 12 m at 8 degrees (0.20 g). [ABSTRACT FROM AUTHOR]

Fire is generally aftermath of an earthquake because of damaged gas pipelines, electrical short circuits, etc. This increases the vulnerability for greater damage to structures and human. In order to mitigate the damage, authors designed and developed an earthquake-resistant high strength steel with fire resistance using Thermo-Calc software. The designed micro-alloyed steel was produced in vacuum induction furnace and casted into ingots. Subsequently, the ingots were rolled to the preferred size in 2/4 high rolling mill. From the rolled plates, desired UTM samples were fabricated. The fabricated samples were quenched in different quench media like brine, water and forced air after preheating to 1050 °C in order to obtain TEMPCORE properties (martensite at the outer ring and ferrite plus pearlite at the core) in the final product. Though various quenching media were used, water quenched samples were giving desired results and hence these samples were used for further fire resistance studies. SEM and TEM studies were performed on these samples at various stages. It was observed that pearlite formed at the core and martensite at the outer ring transformed from the ferrite and the same was confirmed by EBSD. From the TEM studies, it was observed that there is formation of tempered martensite laths and nano-sized nodular carbides of V, Nb and Mo resulting in high yield strength of 715 and 477 MPa at room temperature as well as at elevated temperature of 650 °C, respectively. [ABSTRACT FROM AUTHOR]

In complex networks, important nodes have a significant impact, both functional and structural. From the perspective of data flow pattern detection, the evaluation of the importance of a node in a network, taking into account the role it plays as a transition element in random paths between two other nodes, has important applications in many areas. Advances in complex networks and improved data generation are very important for the growth of computational materials science. The search for patterns of behavior of the elements that make up steels through complex networks can be very useful in understanding their mechanical properties. This work aims to study the influence of the connections between the elements of steel and the impact of these connections on their mechanical properties, more specifically on the yield strength. The patterns found in the results show the significance of the proposed approach for the development of new steel compositions. [ABSTRACT FROM AUTHOR]

When designing steel members with nonsymmetric cross sections, it is essential to consider twisting effects when performing stability checks via second-order analysis according to the ANSI/AISC 360-22. Existing line-element formulations for nonsymmetric sections are mostly derived based on thin-walled assumptions, leading to an overestimation of member strength due to the inaccurate prediction of member behavior, especially when the cross sections have moderate wall thickness. This paper proposes an efficient line-element method for second-order analysis of steel members with nonsymmetric thick-walled sections considering the warping degree of freedom (DOF) and the twisting effects along with the transverse shear deformations. Additionally, a two-dimensional (2D) finite-element cross section analysis method employing the constant strain triangle (CST) element is developed to calculate the section properties for arbitrary cross sections, including the Wagner and the shear coefficients. The proposed method is implemented in the educational structural analysis software MASTAN2 and verified through two sets of examples. [ABSTRACT FROM AUTHOR]

Nb-Ti high-strength low-alloy pipeline steel was subjected to a six-pass rolling process followed by the coiling process at different temperatures between 600 and 650 °C using the thermo-mechanical testing system Gleeble 3500 (Gleeble, New York, NY, USA). This experimental steel was subjected to 72% heavy reduction through a thermos-mechanical controlled process. Thereafter, the microstructures were observed using optical microscopy, scanning electron microscopy, electron backscatter scanning diffraction, and transmission electron microscopy coupled with energy dispersive spectrometry and selected area electron diffraction. For the selected three coiling temperatures of 600, 625, and 650 °C, acicular ferrite, polygonal ferrite, and pearlite were observed, and morphology and statistical analysis were adopted for the study of precipitates. Based on the estimation by the Ashby–Orowan formula, the incremental strength through precipitation strengthening decreases with coiling temperatures and reaches 26.67 Mpa at a coiling temperature of 600 °C. Precipitation-time-temperature curves were obtained to explain the transformation of precipitates. The (Nb, Ti)(C, N) particles tended to precipitate in the acicular ferrite with [011](Nb, Ti)(C, N)//[011]α-Fe orientation. The lower coiling temperature provided enough driving force for the nucleation of precipitates while inhibiting their growth. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) has rapidly evolved and is being embraced by major industrial companies. Various metals, including stainless steel, titanium, aluminum alloys, copper, and precious metals, are available in powdered form for AM technologies. This special issue presents 10 articles covering topics such as improving the sintering process for carbon nanotube-based composites, evaluating the heat treatment condition of a stainless steel, examining crack growth in additively manufactured materials, investigating the microstructure of HSLA steel components, exploring the use of non-destructive testing for AM parts, and discussing the formation of adiabatic shear bands in nickel-based superalloys. These contributions provide valuable insights into optimizing additive manufacturing processes and applications using metal powders. [Extracted from the article]

In order to find out the deformation behavior and mechanical properties of 42CrMo steel under warm upsetting conditions, the Gleeble-3500 thermal simulation testing machine was used to carry out a warm upsetting physical simulation experiment on 42CrMo steel. By controlling deformation temperature, strain rate, and constant temperature deformation pass, the microstructure evolution rule under different warm upsetting conditions was analyzed, and its hardness value was measured. Then, the simulation experiment is carried out based on the Deform-3D finite element platform. The results show that, with the increase in deformation temperature, 42CrMo steel has a temperature rise softening effect, which significantly reduces the peak value of rheological stress. At 650 °C, the maximum peak value of rheological stress is only 45.3% of that of cold upsetting deformation at room temperature, and the stress-strain curve tends to be gentle at the plastic deformation stage, which is the most suitable temperature for warm upsetting deformation. The maximum peak flow stress of 42CrMo steel increases with the increase in strain rate, but the number of deformation channels has little influence on the stress-strain curve. The warm, upsetting deformation can refine the internal grain structure significantly, and the grain refinement mechanism is mechanical crushing. When the temperature is slightly higher, the broken grain will recover, and the grain size will grow. During the process of warm upsetting, the strain rate has a great influence on the microhardness of the sample. The deformation pass has little influence on the hardness, and the hardness increases slightly with the increase in the deformation pass. Through the Deform-3D simulation, the correlation coefficient R and the average absolute relative error (AARE) between the simulation value and the experimental value were calculated, and the correlation coefficient R-value was 0.9948, and the average absolute relative error (AARE) was 2.05%, indicating that the simulation can accurately reflect the relationship between displacement and applied load. [ABSTRACT FROM AUTHOR]

Ice accumulation on airfoils and engines seriously endangers fight safety. The design of anti-icing/de-icing systems calls for an accurate measurement of the adhesion strength between ice and substrates. In this research, a test bench for adhesion strength measurement is designed and built. Its reliability and accuracy are verified by the calibration. The adhesion strength is first measured at different loading speeds and freezing times, and the most suitable values are determined based on the results. Then, the variation in adhesion strength with heating temperatures at different initial substrate temperatures and different heating powers is investigated. Parameter AW is defined to evaluate the heating power from the point of view of energy consumption and adhesion strength. As a result, the loading speed and the freezing time are determined to be 0.5 mm/s and 90 min, respectively. The adhesion strength degrades as the heating temperature increases. As the initial temperature drops, the adhesion strength decreases more slowly. Furthermore, the temperature of WAS (Weak Adhesion State) under heating varies with the initial temperature. Heating with a high power will yield more reduction in adhesion strength for the same temperature increase. The values of AW illustrate that a medium power heating is more favorable to reduce the adhesion strength with a low energy consumption. [ABSTRACT FROM AUTHOR]

In this paper, AlSi coatings and AlSiN coatings on 22MB5 high strength steel and MoS 2 coatings on the die steel were prepared by magnetron sputtering respectively. The tribological properties of the coatings were studied from room temperature to 800 °C. The hardness and the bond strength between the coatings and the substrate were also investigated. The experimental results show that AlSi coatings have poor anti-friction behaviors comparing with the steel, and coefficient of friction (CoF) is as 0.2 at room temperature, but 0.8 at 600 °C. The N element was doped into AlSi coatings with FeAl transition layers to improve the tribological performances of the coatings at high temperature. CoF of AlSiN coatings and H13 steel is high. However, AlSiN coatings have excellent wear-resistance. WS 2 coatings were prepared on the surface of the die steel to improve high temperature anti-friction behaviors of AlSiN coatings and H13 steel pin. The experimental results show that WS 2 coatings exhibit good high temperature anti-friction behaviors. Super low friction about 0.003 is achieved at 600 °C. High temperature superlubricity mechanisms of AlSiN coatings and WS 2 coatings are discussed systematically. [ABSTRACT FROM AUTHOR]