Steel Research Articles

Seismic performance investigation of new buckling-restrained steel plate for resilient rocking column foot joint

Seismic damage-controllable components and design approaches are crucial for achieving the seismic resilience and post-earthquake recovery of building structures. To improve the seismic resilience of reinforced concrete (RC) frame structures, this study proposed a novel assembled replaceable rocking column foot joint. The column foot joint is composed of a concrete foundation, short steel-tube concrete column in the center, and four new buckling-restrained steel plates (BRSPs) on the periphery. A detailed design method for the BRSPs was developed, and six BRSP specimens were designed with different core weakening forms and thicknesses. The specimens were cyclically tested and the failure mode and hysteresis behavior were examined. The test results confirmed that the proposed BRSPs exhibit satisfactory energy-dissipation capacity and achieve damage control. The refined numerical models were developed using ABAQUS and verified using the test results. Parametric analyses were conducted for the BRSPs to examine the influence of core plate thickness, gap size, and restraint plate thickness. A numerical analysis model of the column foot joint was established, and the influence of the axial compression ratio and BRSP bearing capacity on the seismic performance of the column foot was investigated. This study provides a reference for the construction of resilient RC frame structures.

Behavior of CFRP-strengthened short spiral welded tubes under axial load

Spiral welded tubes (SWTs) are formed by rolling steel plates at a certain angle and welding the resulting abutting edges. They are extensively utilized because of their large diameter ranges, high production efficiency, and low production cost. Thin-walled spiral welded tubes with large diameter-to-thickness ratios are susceptible to local buckling under compressive load, and their performance can be affected by corrosive environments. Therefore, this paper proposed the use of carbon fiber-reinforced polymer (CFRP) to strengthen tubes by external bonding. There are limited studies on the axial compression behavior of CFRP strengthened spiral welded tubes, particularly studies that consider the initial imperfections and residual stresses in spiral welded tubes. To bridge this gap, this paper first investigated the distributions of initial imperfections and residual stresses in spiral welded tubes, finding that both are significantly influenced by distinct forming and welding manufacturing processes. Subsequently, axial compression tests were carried out on four unstrengthened specimens and twelve CFRP-reinforced specimens to investigate the compressive behavior by considering the diameter-to-thickness ratio, the length of the steel tubes, and CFRP layer orientation. The experimental results indicate that CFRP strengthening delays local buckling, and significantly enhances the yield load, ultimate load, and initial stiffness of spiral welded tubes, achieving a maximum increase of the yield load up to 69.11 % and the ultimate load up to 61.99 %, while its impact on the ductility index remains uncertain and is influenced by variables such as the diameter-to-thickness ratio of the tubes and the CFRP layer orientation. Finally, a comparison of the ultimate loads of the specimens by tests and design codes was conducted.

Impact of prototype scale effect on the dynamic responses and damage of steel plates under explosions

Scaling model was widely used in engineering to reveal the responses of full-scale prototype model. This study provided insight into the impact of the scale effect on the dynamic response and damage of stiffened and unstiffened steel plates under explosions. A numerical model consider fluid-structure-interaction (FSI) was established using LS-DYNA platform, and the numerical model was verified by the blast test results. Moreover, the scaling factors (S) equal to 1 (prototype), 1/2, and 1/4, and 1/8, and 1/12 were considered in the study, the scaling effects on the breach size, plastic area, and the deformation shape were analyzed. The results showed that the breach size and plastic area of the scaled model deviated from the ideal results based on the replica law. However, the deformation shapes of scaled-down plates accurately reflected the deformation characteristics of the full prototype plate. The scaling factor significantly influenced the dynamic responses of stiffened and unstiffened steel plates; as the scaling factor (S) increased, the dimensionless displacement decreased. The results indicated that a smaller S led to a larger deviation in response. The influencing factors of the scaling effect were investigated, and it was found that stiffened steel plates were more sensitive to the scaling factor than unstiffened steel plates. By comparing the detonation of cuboid, cylindrical, and spherical explosives blast-loaded onto stiffened steel plates, it was determined that the detonation of cubic explosives caused the most severe scaling effect on stiffened steel plates under blast loads. The study also found that explosive mass and standoff distance influenced the scaling effect of stiffened steel plates under blast loads. Additionally, steel plates in the plastic stage and the critical state between the elastic and plastic stages were particularly sensitive to the scaling effect. Due to the strain rate effect, which can lead to a deviation from the ideal scale law, different steel materials exhibit varying scale sensitivities. Comparing stiffened plates made from Q235, Q345, DH36, and L907A, the order of sensitivity to the scaling factor was: Q235 > Q345 ≈ DH36 > L907A.

Simulation and experiment of eddy current detection of U-shaped defects in steel plates

Simulation and experiment of eddy current detection of U-shaped defects in steel plates

Turbulent impinging air jet for cooling the heated surface

The present work deals with the experimental and numerical study of steadystate conjugate heat transfer during impingement of turbulent air jet over a heated stainless steel. The plate is heated using copper heater located at the middle. The temperature field is measured using an infrared camera and compared with the numerical simulations. Numerical simulations are performed using three-dimensional finite volume based formulation. The turbulence shear-stress transport (SST) is modeled using k−ω model based on the Reynolds averaged Navier Stokes (RANS) equations. The numerical simulations are in good agreement with the experimental data with marginal discrepancy in the steel plate region due to the contact thermal resistance between steel and copper. It is observed that the local Nusselt number increased in the stagnation region with increasing velocity of the impinging turbulent flow and practically unaltered in the region of the steel plate.

Flexural Behavior of Reinforced Concrete Beams with Steel-Plate Reinforced Vertical Opening

The structural response of simply supported Reinforced Concrete (RC) beams with square vertical openings is investigated in this work. Studies were conducted using seven specimens of RC beams, with the aim of comparing beams with vertical openings to those without. Meanwhile, the other beams featured carefully positioned square openings. Note that one of these beams served as the control and had no openings. Each beam was the same length (1400 mm) with a 180×120 mm cross-section. Two-point loads were applied over a span of 1200 mm throughout the testing method, with a central load placed 300 mm from the ends. The openings were positioned in the middle of the span and came in three different widths: 20, 40, and 60 mm. Openings were made using either 1.5 mm thick square steel tubing or none at all. The major goal of this study was to determine whether the steel tube could compensate for the decrease in beam strength and the impact of decreasing beam cross-section (producing opening). Correspondingly, the beam ultimate load was found to decrease by 15.75%, 24.2%, and 32.5% for opening widths of 20 mm, 40 mm, and 60 mm, respectively, as the opening width increased. On the other hand, the performance gain for beams strengthened with steel plates when steel tubes were used was 11.78%, 12.14%, and 13.28% for the respective opening widths. Doi: 10.28991/CEJ-2024-010-09-04 Full Text: PDF

Study on the continuous cooling transformation behavior of X65 hydrogen transportation pipeline steel

Abstract In this work, the continuous cooling transformation (CCT) behavior of X65 hydrogen transportation pipeline steel was studied by Gleeble-3800 machine. The CCT curve was constructed by temperature-dilation curves and microstructures of samples at different cooling speeds. The Ac1 and Ac3 temperatures of the tested steel are 715 °C and 901 °C. Polygonal ferrite and pearlite can be recognized when the cooling speed is between 0.2 °C/s ~ 5 °C/s, bainite and polygonal ferrite can be recognized when the cooling speed is higher than 10 °C/s. The hot-rolling process was designed according to CCT. After finishing rolling, the air cooling steel plates possesses higher hydrogen diffusion coefficient, and the steel plates coiled at 650 °C possesses lower hydrogen diffusion coefficient.

Development of Phased Array Ultrasonic Testing System Using Distributed Architecture

Abstract With more rigorous requirements for reliability and safety of structures and materials, high resolution and fast imaging have been urgent needs of Phased Array Ultrasonic Testing (PAUT). In order to improve the detection resolution and efficiency of complex structures and materials such as ultra-thick carbon steel and honeycomb plate, a PAUT system is proposed in this paper. The system uses a distributed architecture, which not only divides hardware resources, improves system performance, but also is scalable. PA, single- and multi-channel conventional UT, and TOFD (Time Of Flight Diffraction) modalities are combined, and PA modality is carried by the fully parallel non-multiplexed 128 PE (Pulse Echo) electronics with independently adjustable emitting and receiving parameters. In addition, the ultrasound analog front-end circuit is designed using discrete devices, providing more powerful analog performance than integrated chips. GTX (Gigabit Transceiver) and PCIe (Peripheral Component Interconnect Express) are applied to high-speed data transmission, providing raw ultrasound data. Characterization and verification results indicate that the system is ideal for challenging inspections in many industries.

The SAM-Krom biomonitoring study shows occupational exposure to hexavalent chromium and increased genotoxicity in Denmark.

Hexavalent chromium (Cr(VI)) is a carcinogen. Exposure to Cr(VI) may occur in different industrial processes such as chrome plating and stainless steel welding. The aim of this study was to assess occupational exposure to Cr(VI) in Denmark. This cross-sectional study included 28 workers and 8 apprentices with potential Cr(VI) exposure and 24 within company controls, all recruited from six companies and one vocational school. Use of occupational safety and health (OSH) risk prevention measures were assessed through triangulation of interviews, a questionnaire and systematic observations. Inhalable Cr(VI) and Cr-total were assessed by personal air exposure measurements on Cr(VI) exposed participants and stationary measurements. Cr concentrations were measured in urine and in red blood cells (RBC) (the latter reflecting Cr(VI)). Genotoxicity was assessed by measurement of micronuclei in peripheral blood reticulocytes (MNRET). At announced visits, a consistent high degree of compliance to OSH risk prevention measures were seen in 'chromium bath plating' for both technical devices (e.g. ventilation, plastic balls, sheet coverings) and in the use of personal protective equipment (e.g. gloves, respirators), yet a lesser degree of compliance was observed in 'stainless steel welding'. The geometric mean of the air concentration of Cr(VI) was 0.26μg/m3 (95% confidence interval (CI): 0.12-0.57) for the Cr(VI)-exposed workers and 3.69μg/m3 (95% CI: 1.47-9.25) for the Cr(VI)-exposed apprentices. Subdivided by company type, the exposure levels were 0.13μg/m3 (95% CI: 0.04-0.41) for companies manufacturing and processing metal products, and 0.81μg/m3 (95% CI: 0.46-1.40) for bath plating companies. Workers with occupational exposure to Cr(VI) had significantly higher median levels of urinary Cr (2.42μg/L, 5th-95th percentile 0.28-58.39), Cr in RBC (0.89μg/L, 0.54-4.92) and MNRET (1.59 ‰, 0.78-10.92) compared to the within company controls (urinary: 0.40μg/L, 0.16-21.3, RBC: 0.60μg/L, 0.50-0.93,MNRET: 1.06 ‰, 0.71-2.06). When sub-dividing by company type, urinary Cr (4.61μg/L, 1.72-69.5), Cr in RBC (1.33μg/L, 0.95-4.98) and MNRET (1.89μg/L, 0.78-12.92) levels were increased for workers with potential Cr(VI) exposure in bath-plating companies, and when subdividing by work task, workers engaged in process operation had increased levels of urinary Cr (8.51μg/L, 1.71-69.5), Cr in RBC (1.33μg/L, 0.95-4.98) and MNRET (1.89μg/L, 0.82-12.92) levels. This biomonitoring study shows that bath platers were highly exposed to Cr(VI), as suggested by relatively high levels of urinary Cr, Cr in RBC and increased levels of micronuclei. The urinary Cr concentrations were high when compared to the French biological limit value of 2.5μg Cr/L, corresponding to the Danish occupational exposure limit of 1μg/m3. This, in turn, indirectly suggests that additional exposure routes than via air may contribute to the exposure. For welders, no statistically significant increases compared to within company controls were observed, however, the observed urinary Cr levels were similar to the levels observed in a European study (HBM4EU), and were higher than the levels observed for welders in Sweden (SafeChrom). In spite of a high degree of self-reported and observed compliance to OSH risk prevention measures during announced visits, the biomarkers of exposure reflecting recent exposure (urinary Cr) or exposure during the last four months (Cr in RBC) may point to variation in compliance to OSH risk prevention measures in general. Reduced occupational exposure to Cr(VI) may be achieved by applying the hierarchy of controls in eliminating or substituting Cr(VI), and the use of more effective technical solutions (e.g. automation).

Numerical study of steel beam to reinforce concrete column (RCC) connection with through-plate and buckling-restrained steel plates

This study examines the behavior and failure mechanisms of steel beam-to-reinforced concrete column connections with through-plate and buckling-restrained steel plates (BRSPs) configurations. These connections are critical components in composite steel and concrete structures, playing a vital role in force transfer and resistance to various loads, especially dynamic loads such as earthquakes. The primary objective of this study is to analyze the hysteresis behavior of these connections under cyclic loading using numerical analyses. Parametric models with varying BRSP thicknesses, ranging from 5 to 25 mm, were used to investigate their impact on hysteresis behavior and load-bearing capacity. The effects of different BRSP thicknesses on stress distribution and failure mechanisms were analyzed. The results from the parametric studies show that increasing the thickness of BRSPs improves the stress distribution in the beam-to-column connections. This improvement includes reduced stress concentration and enhanced uniformity of stress distribution, which can lead to reduced localized failures and increased overall connection stability. Numerical simulations indicate that the use of BRSPs (with a thickness of 15 and 17 mm) results in wider and more stable hysteresis loops, reflecting increased energy absorption capacity and improved deformation behavior of the connections under cyclic loading. The findings show that BRSPs can reduce failure concentration, increase flexural resistance, and prevent buckling in steel beams. These results underscore the importance of using BRSPs to enhance structural performance and mitigate potential failures under severe loading conditions.

Fracture strain improving via structural austenitic stainless steel-coated 22MnB5 plates

A total of 316 austenitic stainless steel (ASS) coatings were deposited on 22MnB5 press-hardening steel plates by varying the substrate bias voltages using a magnetron sputtering technique and quenched in a flat mold with cooling water. The substrate bias current and ion-bombardment energy densities increased up to 0.5 mA/mm2 and 50 J/mm2 at a high voltage of −100 V, and, therefore, the variations in the coatings’ morphologies were owing to the increases in the ion bombardment. The porous bulk pattern appeared in the quenched ASS coating at −100 V, clearly different from the porous columnar structure of the others at −50 and −75 V. The γ-Fe and α-Fe phases were observed from the diffraction peaks, presented the ASS coating and 22MnB5 substrate, respectively. There was no intermetallic compound (IMC) peak detected. In addition, the diffusion layer of the quenched ASS-coated plate was observed, in which its morphology was different from the quenched martensite (M) plate, and proved to be the α-Fe microstructure by the very low α-Fe peak at the standard (110) position. The bright image of TEM and the select area electron diffraction pattern indicated the nanostructure of the quenched ASS coating. The nanohardness of the ASS coating, diffusion layer, and M plate (7.36, 3.60, and 6.25 GPa, respectively) was detected, indirectly proving an α-Fe structure of the diffusion layer. The fracture angles of the 316-coated plates significantly improved from 51.82° at −50 V, 53.77° at −75 V to 57.38° at −100 V, as the ASS structure changed to be porous bulk pattern. The clearance of IMC, coating’s porous bulk pattern, and the low hardness α-Fe diffusion layer benefited for the fracture strain by lengthening the pathway of the crack’s development and blocking the further crack’s propagation, respectively.

Parameter characterization of the PBM-DEM method in numerical simulation of shallow buried mine explosions

Abstract To investigate the impact of various parameters on the numerical simulation of shallow buried mine explosions through the particle explosion method and discrete element method, this paper adopts a coupled method of particle blast method and discrete element method, namely the PBM-DEM method, to simulate the response of AL-6XN stainless steel plate under shallow buried mine explosions. This article first combines the experimental results of Børvik to validate the precision of the PBM-DEM approach. Then, the influence of particle quantity, interaction parameters between sand particles, and interaction parameters between sand particles and plate on the outcomes of the numerical simulations are analyzed. The analysis reveals that as the quantity of explosive particles rises, the central displacement and maximum kinetic energy of the plate escalate. In contrast, these values decrease as the number of sand particles increases. The interaction parameters between sand particles have almost no effect on the numerical simulation results. The damping and stiffness parameters between the sand particles and the plate have a pronounced effect on the numerical simulation results, and the center displacement and peak kinetic energy of the plate rise as the damping and stiffness parameters between the sand particles and the plate increase.

Microstructural and mechanical characterizations of weld metal of S960QL ultra high strength steel joints obtained with different multi-pass laying techniques using GMAW

Abstract 15 mm thick ultra-high strength steel plates with 960MPa yield strength were welded using different multi-pass laying techniques (i.e., stringer and weaving beads) with torch manipulation. Weld metals obtained were compared using different mechanical (i.e., micro tensile tests and Vickers hardness maps) and microstructural (i.e., optical microscope, scanning electron microscope, X-ray diffraction, electron backscatter diffraction) characterization techniques. Coarser grains and acicular ferrite were observed in weld metal obtained with weaving pass procedure. There were hardness differences in face and root passes of both weld metals. Yet, hardness values were 19% and 11% higher for face and root regions of the joint obtained by stringer pass procedure, respectively. Fractographs of micro tensile test specimens revealed dimples depicting ductile network structure for both joints.

Strategic selection of metal-cutting processes for thick steel plates using a hybrid decision methodology

Metal-cutting is indispensable in manufacturing, enabling precise component fabrication for industries like construction, automotive, aerospace, and shipbuilding, where accurate, efficient cutting of thick steel plates is crucial. This paper introduces a novel case study to strategically determine the optimal metal-cutting process for thick steel plates utilizing a hybrid MOORA-PSI approach. The use of the hybrid MOORA-PSI method simplifies decision-making by integrating weight assignment and ranking of alternatives. Five prominent metal-cutting processes, including oxygen flame, plasma arc, laser, wire EDM (wire electro-discharge machining), and abrasive water jet cutting, are commonly used for cutting thick steel plates, each with unique capabilities and limitations, and are considered potential alternatives. Eight evaluation criteria, capital cost, running cost, accuracy, edge quality, kerf width, maximum thickness, production flexibility, and production rate, are used to assess these metal-cutting alternatives. Wire EDM ranks as the optimal choice for cutting thick steel plates based on defined evaluation criteria, with laser cutting closely trailing, followed by oxygen flame, abrasive water jet, and plasma cutting successively. The results are validated by comparing them with those of other MCDM approaches and by conducting a Spearman’s rank correlation coefficient test, yielding consistent results. Additionally, sensitivity analysis, employing criteria weight exchange and dynamic variations in the decision-making matrix, further confirms the accuracy and reliability of the findings.

Stress-strain state of ceramic shell mold during formation of spherical steel casting in it. Part 2

The paper presents the results of numerical calculations of the solution to the problem of modeling the process of possible cracking in a spherical shell mold when pouring liquid steel into it and cooling the solidifying casting. The numerical scheme of the axisymmetric problem and the algorithm for its solution were given in Part 1. The crack resistance is estimated by magnitude of the normal stresses in the ceramic shell during its co-cooling with a solidifying casting. The results detailed analysis considered: fields of displacement, stresses, and temperatures both on spherical surface and in growing crust of solidified metal. The solution took into account the change in the shear modulus of the mold material from temperature, and an assessment of this refinement was given. The problem was solved in two ways. The first – with a constant shift modulus of the shell mold; the second – with its temperature-dependent shift modulus. There is a significant difference between these variants in terms of magnitude of the normal stresses arising in the shell mold. The authors analyzed resistance of the shell mold spherical geometry to external influences from its support filler and filling funnel. The problem of determining the contact and free surfaces at the boundary of the shell mold and support filler was solved. The results are presented graphically in the form of diagrams of stresses and temperatures over the studied area in its different sections and time intervals for cooling of the growing metal crust. The role of compressive normal stresses σ22 , σ33 on the surface of contact of the shell mold with liquid metal at the initial moment of cooling on probability of cracking in a spherical mold is shown. The level of strain-stress state in a spherical shell mold when cooling a steel casting in it is significantly determined by dependence of shift modulus of the shell mold on temperature.

Damage assessment of fixed U-shaped stiffeners stiffened square plates subjected to close-in explosions

The aim of this study is to suggest an approach for evaluating the damage modes and damage levels of the U-shaped stiffeners stiffened plates exposed to close-in explosions. To achieve this objective, a numerical model was developed in LS-DYNA, and the numerical model was verified by experimental results of the authors. Using this validated model, various U-shaped stiffeners stiffened plates were examined under different blast loads. The study investigated the factors that influence the damage modes of the plates, including the strength and distribution of the blast loads, as well as the geometry of the stiffened plates. The results indicated that the small size stiffened plates exhibited overall damage mode while the large stiffened plate showed localized damage at the same blast load. The blast load distribution on the different size plate led to different damage modes. Additionally, this study found that the slenderness of the stiffened plate had a great influence on the support rotation angle of the tensile tearing threshold. The larger span to thickness ratio can result in larger tensile tearing threshold. Moreover, 400 numerical cases were included and used to classify the damage modes of stiffened steel plates. Based on the damage mechanism of the stiffened steel plate, the damage number (Φ1 and Φ2) which considering the blast loads and material parameters of plate, the maximum incident angle of the blast load(α), and the relative stiffness of the stiffeners and the flat steel plate (κ1 and κ2), and the thickness to span ratio of the stiffened plate (λ) were combined to identify the damage modes of stiffened plates. Furthermore, a flow chart was constructed for determining damage modes based on these considerations. Additionally, a curve surface fitting was performed using Φ1 and λ, the fitting formulas were then used to estimate the deformation characteristics of the stiffened plates with U-shaped stiffeners. The damage levels of the U-shaped stiffeners stiffened plates were then classified as low damage, medium damage, severe damage, and collapse by combining the nominal support rotation angle with the threshold of the global tensile tearing at boundaries. The study result can provide insight into the damage mode identification and damage level classification of stiffened steel plates under explosion. Additionally, this study was a base of damage evaluation of the structure elements (such as steel box girder) include stiffened steel plates under explosions.

An Evaluation of Backfill Material Applicability through Deformation Measurements of Long-Span Buried Corrugated Steel Structures

Corrugated steel plates are increasingly being applied to various types of structures, such as eco-corridors, noise reduction tunnels, and urban elevated roads. However, applications for spans exceeding 25 m are lacking, as they require clear standards for calculating the elastic moduli of backfill materials and reinforced sections. This study evaluated the appropriateness of mechanical assumptions applied in the design, by measuring displacements at each stage and comparing the finite element analysis results for a concrete-reinforced corrugated steel plate arch underground structure with a width of 27.5 m and length of 467 m. Based on the measurement results, deformations ranging from 19.8% to 63.7% of allowable deflection were observed when applying an elastic modulus of 60 MPa to solidified soil backfill, which is twice the maximum standard value applied to general soil, thereby confirming the suitability for the serviceability of underground structures.

Residual mechanical properties of corroded ultra-high-strength steels and weld metals

This paper presents an in-depth investigation into the residual mechanical properties of ultra-high-strength steels and weld metals after exposure to corrosive environment. The tensile specimens of weld metals were fabricated using ER100S-G, ER110S-G, ER120S-G feedstock wires by robotic gas metal arc welding, whilst ultra-high-strength steel tensile coupon specimens were machined from the Q890 and Q960 steel plates. The high-strength steel and weld metal tensile specimens were exposed to neutral salt spray accelerated corrosion conditions. Six exposure durations were designed to achieve different corrosion degrees of specimens. A total of 23 corroded ultra-high-strength steel tensile coupon specimens and 19 corroded high-strength weld metal specimens were included. The geometric profiles of corroded steel specimens were determined via non-contact 3D laser scanning. Monotonic tensile tests were conducted to determine the stress-strain responses and key mechanical properties of corroded steel and weld specimens. Mechanical properties deterioration of corroded ultra-high-strength steels and weld metals are reported and discussed. Prediction equations on the residual mechanical properties regarding the tensile loading capacity, yield stress and ultimate tensile stress of ultra-high-strength steels and weld metals after exposure to corrosive environment were established.

Seismic performance of slit steel plate shear walls strengthened by FRP laminate

Steel plate shear walls with slits are widely used in high–rise building structures due to their flexible arrangement and high ductility. After long-term service, cracks may occur in the slit steel plate shear walls due to repeated buckling and stress concentration. In this study, an FRP–steel composite slit steel plate shear wall was proposed to improve its mechanical performance and service function. Experimental and finite element analysis were conducted to investigate the performance of slit steel plate shear walls reinforced with FRP under low cycle reciprocating load. It was shown that the use of FRP to strengthen slit steel plates can effectively improve the out–of–plane stability of the structure and reduce the stress concentration at the slits. The stiffness and load–bearing capacity of the reinforced slit steel plate shear walls were significantly enhanced. The reinforcement effect of FRP did not significantly affect the energy dissipation capacity of the shear walls. A numerical study was performed to investigate the optimal orientation of the FRP arrangement. The analysis revealed that when the carbon fibers were arranged horizontally and vertically orthogonally, the structure exhibited better seismic properties. This study can not only improve the seismic performance of slit steel plate shear walls, but also have engineering implications for the seismic reinforcement of existing slit steel plate shear walls.

Induction assisted autogenous plasma arc welding of HSLA steel

In this work, a high frequency induction heating (HFIH) assisted plasma arc welding (IPAW) technique is proposed to weld 6 mm thick S690QL high strength low alloy steel plates in square butt joint configuration and without using any filler material. A 3D finite element based coupled electromagnetic-thermal analysis is carried out to ascertain the weld's thermal characteristics. Microstructure evolution and mechanical performance are investigated using scanning electron microscopy, electron back scattered diffraction, transmission electron microscopy, tensile test, Charpy impact test and micro hardness test. The results demonstrate that 15 s initial static heating using a co-directional current coil with magnetic flux concentrator predominantly improves the weld penetration by 48 % and joint efficiency reaches 90 % to the base plate strength. Microstructural study shows that the addition of HFIH promotes low angle grain boundaries (LAGB) with bainite ferrite and granular bainite micro-constituents in the fusion zone, which causes localised yielding and failure in this zone during tensile test. Further investigation reveals that the HFIH encourages the formation of BI-type bainite ferrite laths of 1.3–2.2 μm width, combined with slender martensite-austenite (M-A) island at the bainite ferrite lath boundaries. The results also reveal that the induction heating promotes the formation of M23C6 precipitates and B2 structured Cu-enrich nano precipitates in the fusion zone (FZ). The microhardness distribution indicates that the FZ and coarse grain heat affected zone are significantly reduced due to the assistance of the HFIH. The impact test result shows a lower energy absorption by the IPAW weldments due to dominance of the LAGB with unfavourable strain distribution.