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Exploring fire resistance of high strength steel end-plate connections is one of the key technical bases for fire resistance design and fire safety assessment of high strength steel structures. Numerical simulation and parameter analyses of high strength Q690 steel flush end-plates will contribute to a reasonable design of high strength flush end-plate connections. In this paper, a finite element model of high strength steel flush end-plate connection considering thermal creep effect was established and validated by experimental results. The thermal creep finite element model can simulate accurately heat performance, failure modes and deformations of high strength flush end-plate connections at elevated temperatures. The increase of axial compression ratio has little effect on rotation, deflection, failure time, critical temperature, and critical rotation with elevated temperatures. The increase of bending moment ratio has little effect on the development trend of rotation and deflection. Proper increase of thickness of the end-plate can improve failure time and critical rotation, and the increase range is within 7% and 36% respectively. Proper increase of diameter of bolt can improve failure time, critical temperature, and critical rotation to a certain extent, and the increase range is within 10%, 6% and 27% respectively. Proper increases of thickness of the end-plate and diameter of bolt will improve the fire resistance of flush end-plate connection. [ABSTRACT FROM AUTHOR]

Galvanizing is an important industrial process to improve the corrosion resistance of advanced high strength steels (AHSSs) that are vital for automotive industries. During galvanizing, nanoscale intermetallic phases with complex crystal structures are formed at the interface between the steel substrate and the zinc overlay. To better understand the nanoscale structures and the interfacial properties between the intermetallics, in this work, we develop a second nearest neighbor (2NN) Fe–Al–Zn ternary Modified Embedded Atom Method (MEAM) potential to describe the crystal structures of the intermetallics, i.e. Fe3Al8, Fe4Zn9 and FeZn13 and to calculate the interfacial structure and energy between them. The developed MEAM potential describes well the complex crystal structures and can be used to investigate the interfacial properties that are difficult to obtain from experiments. The Fe4Zn9, FeZn13 surface energies; the Fe–Fe4Zn9, Fe–FeZn13, Fe3Al8–FeZn13 interfacial energies; and the work of adhesion are calculated with the developed MEAM potential. The results show that FeZn13 crystal orientation has an insignificant effect on the FeZn13 surface energy and the Fe–FeZn13 interfacial energy. A negative interfacial energy is obtained for the Fe–Fe4Zn9 and the Fe–FeZn13 interface. The lowest interfacial energy is obtained in the {100}Fe case. The interfacial energy of Fe3Al8–FeZn13 depends on the surface termination of Fe3Al8 and FeZn13. A low interfacial energy is obtained when the surface termination of Fe3Al8 and FeZn13 are both Fe rich. In contrast, when the surface termination of Fe3Al8 is Al rich or the surface termination of FeZn13 is Zn rich, no low energy, stable interface can be formed between the two phases. [ABSTRACT FROM AUTHOR]

Responsible for 70% of the global CO2 emissions, infrastructure has a significant impact on our climate and the related consequences. Bridges are a major keystone of the infrastructure and take a leading position in its decarbonization. In this framework, low‐carbon emission steels play an important role. Low‐carbon emission steels, like ArcelorMittal's XCarb® recycled and renewably produced steels, are already available on the market. Combining scrap and renewable electricity, it offers very low levels of CO2 emissions per ton of finished steel. The present paper describes how different steel solutions can be combined to lower the material input, to simplify the construction process and to reduce the maintenance efforts in bridge construction. The impact of efficient design has been assessed by a Life‐Cycle Assessment (LCA) for bridge solutions with small and medium spans of up to 40 m. The paper concludes with a summary of recently realized bridge projects in Poland. [ABSTRACT FROM AUTHOR]

In this study, a constitutive model applied to predict the tensile properties and fracture behavior of well‐bonded multilayered metal composites is extended. The equivalent single‐layer model, as a convenient method, is introduced into finite‐element simulations by combining it with an improved Xue–Wierzbicki damage plasticity model that considers material anisotropy. The steel use stainless (SUS) 430/Al1050/SUS430 laminated sheet fabricated by cold rolling is selected as the research material. The quasistatic uniaxial tests and Nakazima tests are operated to verify the accuracy of the proposed method. The mean errors in tensile stress and fracture forming limit strains are 2% and 3%, respectively. A load‐sharing mixture rule is proposed to assess the effects of the volume fraction, strength coefficient, and hardening exponent of the constituent materials on the mechanical properties of the laminates. In the results, it is indicated that the laminate exhibits sufficient elongation and remains markedly enhanced in tensile strength, reaching 470 Mpa when the ductile Al layer is combined with the higher strength and hardenability steel layer. In this research, it is aimed to clarify the formability characteristics in laminated composites for optimal sheet configuration design and development. [ABSTRACT FROM AUTHOR]

• 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]

In high-strength steel (HSS), shear edge failure due to stretch flangeability is a serious problem. Shear edge failure is strongly affected by the cutting methods. As countermeasures, cut-off punching and double punching of the entire circumference have conventionally been considered. However, it has not been shown whether these processes can be applied to the stretch-flange-forming part of the outer circumference of automotive parts. In this study, the effect of the punching allowance and the method of improving the double punching process on the outer circumferences of automotive parts were investigated using hot-rolled HSS sheets. The results of hole expansion tests and observations of shear edge faces and metal flow show that partial double punching reduces the rigidity of the cut-off side and increases the collapse probability. Also, the crack propagation caused by high tensile stress near the upper cutting edge is accelerated. In comparison with double punching of the entire circumference of a 590 MPa-class or 780 MPa-class HSS sheet, in partial double punching, the stretch flangeability is improved and the hole expansion test value is 1.5 times that of double punching when the cut off amount is greater than the thickness. However, it is considered that the stiffness of the cut-off side varies depending on the curvature and the thickness of the plane, and the effect of such variations will be confirmed in a wide range of curvature and thickness in the future. [ABSTRACT FROM AUTHOR]

To investigate the fracture initiation mechanisms and establish the relationship between the ductile fracture mechanism and macro stress–strain for high-strength structural steel, the mechanical response and fracture behavior of Q460C steel and its butt welds were studied via tests, numerical analysis and scanning electron microscopy (SEM) in this paper. The mechanical properties of high-strength steel (HSS) under different stress triaxialities were studied by uniaxial tensile tests on standard specimens and notched round rods. The finite element model is set up according to the characteristic length which is based on SEM observations. By combining experimental results and numerical simulations, the constitutive model and fracture prediction model were established. The relationship between the ductile fracture mechanism and the macro stress strain was obtained. The toughness parameters of the micromechanical model of Q460C steel and its welded joints were compared with those of Q345 steel and seven other types of structural steel from the United States and Japan. The results show that the characteristic length of the crack tip is the key factor affecting the accuracy of predicting fracture toughness under a large stress–strain gradient. The toughness predicted by the model is in good agreement with the traditional fracture toughness test results when taking the average value. The experimental results and finite element analysis verified the effectiveness of the VGM and SMCS micromechanical models in predicting the fracture toughness of Q460C steel and its welded joints, which can provide a theoretical basis and practical guidance for the anti-fracture design and application of HSS structures. [ABSTRACT FROM AUTHOR]

Hydrogen can cause weld cold cracking even days after fabrication. In this respect, higher strength steels present a challenge to established cold crack testing. In general, the tolerable hydrogen concentration for crack prevention decreases with increasing material strength. In addition, advanced welding processes require changes in weld geometry and heat input. This directly influences the formation of crack-critical microstructures, e.g. in hardened areas of the heat-affected zone. The limits of use and application of modern cold cracking tests are evaluated by (1) the externally loaded Implant-test and (2) the self-restraint Tekken-test. In particular, external mechanical stresses, which cause additional mechanical loads on the components during welding, must be considered due to the component-specific stiffness of high-strength steels. Accompanying test methods for determining hydrogen concentration and diffusion in welds are presented, such as carrier gas hot extraction for determining hydrogen concentration (ISO 3690) or temperature-dependent diffusion coefficients. These values are of great importance for a holistic approach to the evaluation of the cold cracking sensitivity of high strength steels. [ABSTRACT FROM AUTHOR]

Nonoriented electrical steel for new energy vehicles should have high strength and excellent magnetic properties simultaneously. However, it is challenging to optimize mechanical and magnetic properties simultaneously during nonoriented electrical steel processing. This article prepares nonoriented electrical steel with high strength and excellent magnetic properties by Cu–Ni alloying, and the evolution of properties of Cu–Ni‐alloyed nonoriented electrical steel during aging and underlining mechanisms is studied. The optimal strength is achieved when aging for 10 min with a yield strength of 773 MPa, where the magnetic induction intensity (B50) is 1.66 T, and the iron loss (P1.0/400) is 18.07 W Kg−1. The optimal strength is attributed to the Cu–Ni recombination, which induces a rapid precipitation of numerous small‐sized Cu‐rich phases within a short period. Besides, the main strengthening mechanisms of the small‐size Cu‐rich phases are modulus strengthening and ordered strengthening. Furthermore, the small‐size Cu‐rich phases with B2 and body‐centered cubic structure in the earlier aging period do not deteriorate the magnetic properties of the steel. Nevertheless, in the late aging period, due to the coarsening of the precipitated Cu‐rich phase with face‐centered cubic structure and the abnormal growth of some grains, the eddy current loss increases, leading to worsen magnetic properties. [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]

Tool condition monitoring is an important basis to ensure workpiece quality and machining efficiency. It is also a key factor in improving machining efficiency, ensuring machining accuracy. Therefore, a new method for predicting tool wear based on DenseNet-ResNet-GRU is proposed. Firstly, statistical theory and an improved wavelet threshold denoising method are used to improve the signal quality. In addition, the asymptotic semi-soft threshold function is applied to reduce the noise of the cutting force signal. Secondly, DenseNet, ResNet, and GRU (gate recurrent unit) deep learning networks are integrated to create a new tool wear prediction model to realize the nonlinear mapping relationship between the tool wear amount and the cutting force characteristic. Finally, the tool wear prediction model is verified by high-strength steel experiment. The experimental results verify the accuracy and reliability of the method, which has a better training effect and higher prediction accuracy compared with the CNN-GRU model. [ABSTRACT FROM AUTHOR]

Advanced high‐strength steels (AHSS) have been extensively studied to develop its third generation from relatively low‐cost alloys, but seeking optimized mechanical properties. In this context, the effects of quenching heat treatments are evaluated in this work after intercritical austenitizing (IA) on microstructure, alloying elements partitioning, and Ms temperature for a commercial CMnSi alloy. Applying dilatometric data and microstructural characterization, different heat cycles are evaluated. The obtained experimental results are compared with those ones obtained by computer simulations at equilibrium conditions. Based on this characterization, an optimized one‐step quenching and partitioning (Q&P) cycle (after IA) is proposed and applied to tensile test specimens. Then, the specimen microstructure is characterized by scanning and transmission electron microscopy as well as by X‐ray diffraction. Using the proposed methodology, it is possible to produce a Q&P steel with a product of tensile strength and elongation of 29.5 GPa% and a 7% volumetric fraction of retained austenite. It is concluded that the precise knowledge about the IA effects on the phase transformations and microstructure evolution in a commercial CMnSi alloy has great potential to be applied in defining a one‐step Q&P heat treatment that favors a multiphase microstructure, which meets mechanical properties requirements for a third‐generation AHSS. [ABSTRACT FROM AUTHOR]

High-strength steel (HSS) can effectively and economically design structural members that withstand large forces induced by extreme events such as earthquakes. To evaluate the seismic performance of HSS members and structures using nonlinear finite element (FE) analyses, using an accurate material model is important, which can simulate the inelastic cyclic behavior of the HSS. The peculiar material behavior of HSS needs to be considered in the model. This study used a combined hardening model to construct the material model. The configuration of the model and the constituent model parameter values are determined to precisely simulate the low-cycle fatigue (LCF) behavior of HSS. An efficient particle swarm optimization (PSO) algorithm is used to determine parameter values with LCF test data of 54 individual HSS coupons. In additions, to conveniently determine the model parameter values with only monotonic tensile test data instead of conducting expensive LCT tests, empirical equations are proposed. It is shown that the LCF curves of HSS can be accurately simulated using the constructed material model with the proposed equations. [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]

Structured catalysts coatings exhibit excellent performance on non‐adiabatic gas–solid process, deriving from their enhanced heat and mass transfer properties. However, the coating catalysts prepared by traditional hydrothermal method of zeolite encapsulating noble metal are prone to spalling, especially under conditions of large flow rate and high temperature. Herein, we prepared PtZn clusters encapsulated in silicalite‐1 zeolite coating on stainless steel with high bonding strength by an improved in situ growth method. The optimized catalyst exhibited ultra‐thin, uniform, continuous, and high degree of crosslinking, thereby enhancing mass transfer and thermal stability. In propane dehydrogenation reaction, the optimized PtZn@S‐1‐R showed a high specific activity of 14.7 molC3H6 molPt−1 s−1 and a propylene selectivity above 99% at 600°C with a high weight hourly space velocity of 120 h−1. The metal‐encapsulated zeolite coating catalysts broaden the application avenue for heterogeneous catalysis with great application prospects. [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.

Martensitic steels, engineered to meet automotive weight reduction and crashworthiness requirements, are highly susceptible to hydrogen embrittlement (HE). Despite extensive research to improve HE resistance, these steels remain vulnerable to HE after undergoing resistance spot welding (RSW). HE in spot-welded steels has been largely unexplored, and its underlying mechanism remains unclear. This study investigates the HE mechanism in RSWed steel sheets by examining microstructural alterations and hydrogen trapping sites before and after RSW. Additionally, the study analyzes variations in tensile-shear test (TST) properties relative to increasing hydrogen content. In spot-welded steels, the tensile-shear strength and fracture displacement decline as diffusible hydrogen levels increase. Specifically, fracture displacement sharply declines within the first 3 h of hydrogen charging, but this loss rate significantly decreases thereafter. This slope shift is attributed to a transition in the crack propagation path. Initially, cracks propagate along the fusion zone line, featuring transgranular failure. However, beyond a critical hydrogen content, crack propagation shifts to the prior austenite grain boundary (PAGB) in the upper critical heat-affected zone (UCHAZ), exhibiting intergranular failure. Consequently, when hydrogen content surpasses this critical threshold, the PAGB in the UCHAZ is weakened due to hydrogen-enhanced decohesion (HEDE) and hydrogen-enhanced localized plasticity (HELP). Cracks then propagate along the PAGB in the direction of maximum stress during the tensile-shear test (TST), leading to a change in the crack propagation path. [Display omitted] • The resistance to hydrogen embrittlement for spot-welded advanced high strength steel is evaluated by tensile-shear test. • The difference in the behaviors of hydrogen embrittlement between steel matrix and welded part is compared. • The phenomenon of crack propagation path transition is observed over certain hydrogen content. • The mechanism of crack propagation path transition is discussed. [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 expanded web depth of steel beams leads to improved strength and stiffness. In some design scenarios, such as cellular, castellated, or expanded steel beams, increasing the depth of the web improves the strength and performance of the steel beam. The expanded web of steel beams can be accomplished by creating a horizontal cutting in the web and then adding a plate between the two web section halves, which are called spacer plates. This method leads to improved stiffness and strength. Numerical models have been developed to accurately predict the properties of these beams. This study investigates the use of incremental plates to increase the depth of hot-rolled wide-flange steel beams. The experimental results were validated first with the Finite Element (FE) numerical model created by ABAQUS software, and then Finite Element Analysis (FEA) methods were used to create and analyze new numerical models by considering parameters that provided more models at a lower cost. The load-mid-span deflection curve behavior of both models (experimental and theoretical) was similar. Also, the load-deflection behavior of steel beams with two types of openings was studied. For the first type of opening (B1 NUM), with a smaller opening width of 30 mm and a higher hole number (24), the ultimate load increased by 53%, 111%, and 184%, the deflection at 0.95 Pu increased by 160%, 293%, and 81% of beams with ratio 150%, 200%, and 250% compared with the reference beam. For the second type of opening (B2 NUM), with a larger opening width of 60 mm and smaller hole number (12), the ultimate load capacity increased by 51%, 147%, and 177%, for beams with a ratio of 150%, 200%, and 250%, compared with the reference beam. The deflection at 0.95 Pu increased by 46% and 15% for beams with a ratio of 150%, and 200%, and decreased by 8% for beams with a ratio of 250%. Accordingly, for the first type of opening, the expanded ratios of 150% and 200% performed best with a reduction of only 1%-12% in the ultimate load capacity. However, for the second type of opening, the beam with a ratio of 250% performed better than the first type. Using prestress strands may highly improve steel beams' performance with the expanded webs containing openings by creating a stronger section that can withstand higher loads and exhibit improved structural performance, especially from beams with a ratio of 150%. [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 an experimental study on cold-formed steel (CFS) composite beams with profiled steel sheeting. Four full-scale composite beam specimens comprising cold-formed double-lipped channel sections, profiled steel sheeting, concrete slabs, and bolted shear connectors were examined. The results show that profiled steel sheeting behaves like tensile reinforcement beside the concrete slab. Of particular interests were thickness and height of CFS beams. The results showed that for higher steel thickness, the failure mode was concrete crushing before CFS beam reached its yielding point. Besides, no failure occurred in the shear connections. By increasing the thickness of CFS from 1.25 to 2 mm, the ultimate loading capacity of composite beams increased almost 45%. This was due to the presence of the profiled steel sheeting and the strong connectors, which prevented sudden slip between the CFS beam and the concrete slab. A comparison between code-calculated and experimentally evaluated degree of shear connection shows that the results are so close. Furthermore, a 3D finite element model was established, and the numerical models were verified against experimental results and the behavior of structures were accurately simulated. [ABSTRACT FROM AUTHOR]

Mean torsional stress is considered to have less effect on the torsional fatigue strength of steels, but several experimental results have been recently reported that mean torsional stress caused significant reduction in torsional fatigue strength in the very high cycle region for shot-peened spring steel. To investigate the effect of mean torsional stress on high strength steel, ultrasonic torsional fatigue tests with mean torsional stress were conducted for spring steel and bearing steel, which are used for mechanical components subjected to cyclic shear stress. Torsional fatigue strengths up to 109 cycles were obtained for fully-reversed torsional loading (R = -1) to pulsating torsional loading (R = 0). The results revealed that mean torsional stress caused a reduction in fatigue strength in the very high cycle region for both spring steel and bearing steel, and applying higher mean shear stress would result in transition of the fracture origin from a surface to an internal inclusion. The reduction in torsional fatigue strength was discussed from the viewpoint of the transition of the fatigue origin, and applicability of a √area p parameter model was discussed for predicting the reduction in torsional fatigue strength. [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]

Given their numerous functional and architectural benefits, such as improved bearing capacity and increased resistance to elastic instability modes, cold-formed steel (CFS) built-up sections have become increasingly developed and used in recent years, particularly in the construction industry. This paper presents an analytical and numerical study of assembled CFS two single channel-shaped columns with different slenderness and configurations (back-to-back, face-to-face, and box). These columns were joined by double-row rivets for the back-to-back and box configurations, whereas they were welded together for the face-to-face design. The built-up columns were filled with ordinary concrete of good strength. Finite element models were applied, using ABAQUS software, to assess mechanical performance and study the influence of assembly techniques on the behavior of cold-formed columns under axial compression. Analytical approaches based on Eurocode 3 and Eurocode 4 recommendations for un-filled and concrete-filled columns respectively were followed for the numerical analysis, and concrete confinement effects were also considered per American Concrete Institute (ACI) standards for face-to-face and box configurations. The obtained results indicated a good correlation between the numerical results and the proposed analytical methodology which did not exceed 8%. The failure modes showed that the columns failed due to instabilities such as local and global buckling. [ABSTRACT FROM AUTHOR]

The usage of high strength steel (HSS) is steadily increasing, primarily driven by the pursuit of weight reduction, leading to a subsequent decrease in greenhouse gas emissions. This paper investigates the impact of various post-weld heat treatment (PWHT) temperatures of 525 °C, 550 °C and 575 °C with a holding time of 2 h on both the microstructure and mechanical properties of weld metal produced using a HSS metal cored wire. The investigation reveals that PWHT does not significantly alter strength but has a more pronounced influence on toughness. The as-welded condition exhibited the highest toughness. Among the samples subjected to the PWHT, the one treated at 575 °C showed the highest impact energy, reaching 69 J at −60 °C. This outcome is attributed to the increased presence of acicular ferrite in the microstructure, surpassing that of samples subjected to PWHT at different temperatures. [ABSTRACT FROM AUTHOR]

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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]