Thin Steel Plate Research Articles

Study on seismic behavior of oblique CFRP corrugated plate-steel plate light weight sandwich composite shear wall

To improve the seismic behavior of the thin steel plate shear wall (SPSW), carbon fiber reinforced polymer (CFRP) is introduced into the thin SPSW, and polyethylene terephthalate (PET) foam is filled between CFRP corrugated plates and steel plate. An oblique CFRP corrugated plate-steel plate lightweight sandwich composite shear wall specimen (hereinafter: sandwich composite plate specimen) is designed. Furthermore, this paper compares the failure mechanism and hysteresis performance of the sandwich composite plate specimen and traditional non-stiffened SPSW specimen under the quasi-static test, and explores the influence of sandwich composite plate on the performance of wallboard. Finally, a simplified finite element model is established and its accuracy is verified by experiments. The results show that compared with the non-stiffened SPSW structure, the initial stiffness of the sandwich composite plate structure is increased by 34.0%, the energy dissipation capacity is increased by 38.44% when loads to 2% drift, and the maximum out-of-plane deformation is reduced by 93.24%. The sandwich composite plate structure shows obvious four-stage stress characteristics, and has good cooperative working performance before the CFRP corrugated plates debond in a large area, also plays a great role in anti-buckling.

Retrofit of RC buildings using vertical shear links and hybrid connections

This study employs a retrofit system with a vertical shear link inside a steel frame to improve the structural behavior of an existing reinforced concrete (RC) frame. The steel frame is connected to the RC frame through a hybrid connection system. The hybrid connection not only provides a rigid, strong connection between the steel and RC frames but also increases the shear strength of RC columns and beams. It is referred to as a hybrid connection in light of such combined measures. The connection is composed of thin steel plates, bolts, and infilling grout. This study tested four one-bay one-story RC frames. One of the RC frames was the benchmark, while the three remaining RC frames were retrofitted under different schemes. The scale factor of the frames was set to 1/3 ∼ 1/4 to model a low-rise RC building. The experimental results of the retrofitted RC frames by vertical shear links demonstrated that the boundary steel frame played a key role in obtaining a stable hysteretic response. Moreover, the hybrid connection strongly withstood the shear force between the RC frame and the steel frame. A series of calculation approaches were proposed to find the lateral strength of retrofitted frames under different failure mechanisms. The calculated lateral strengths were observed to agree with the experimental results.

Investigation of delta-t mapping source location technique based on the arrival of A0 modes

The main assumptions made for traditional Time of Arrival (TOA) source location techniques are constant wave speed and straight wave path between the acoustic emission (AE) source and the sensors. However, because of material inhomogeneity and structural complexity, wave velocities may vary in different directions and a direct wave path may be very difficult to be achieved. Therefore, to solve these problems, researchers developed delta-T mapping source location technique, which has been shown to have good accuracy for source location in aerospace structure because complex geometric features are considered when training the mapping data and accurate wave speed data are not required. However, this technique relies on identifying the arrival time of S0 (extensional) Lamb mode, which may not be distinguished from background noise due to lowamplitude AE sources such as corrosion or large source-to-sensor distance. As shown in Figure 1, source location accuracy in a corrosion test on a simple plate was greatly improved after the velocity of A0 (flexural) Lamb mode was used in the source location algorithm. Therefore, identifying the arrival time of A0 modes and hence building delta-T maps are more feasible to solve the problem. Experiments have been carried out with an artificial AE source on a thin complex steel plate. A threshold crossing method based on wavelet coefficient was used to estimate the arrival time of A0 modes. The average error (3.9 mm) of the source locations predicted by delta-T mapping based on A0 arrival was larger than that (1.8 mm) of S0 arrival, which can be explained by the difficulties in accurately identifying the arrival of A0 modes.

Non-contact Gripping of Thin Steel Plates by Electro Magnetic Suspension

Non-contact Gripping of Thin Steel Plates by Electro Magnetic Suspension

The influence exerted by active cooling on the permanent connection formed as a result of electric arc welding

The problem of temperature stresses is solved in the work. The process of electric arc welding with guaranteed penetration of steel plates of various thicknesses is simulated. The possibility of reducing residual stresses formed as a result of welding by applying heat removal from the surface of the near-weld region of a steel plate is being investigated. The temperature distribution is determined by solving a non-linear heat equation, in which the specific heat and thermal conductivity depend on temperature. The heat source is modeled using the double ellipsoid method proposed by John A. Goldak. The horseshoe-shaped heat sink follows immediately after the anode spot and is set by the heat flux in such a way that the main temperature of the plate does not decrease below its initial temperature. This limitation reduces the level of the temperature gradient, thereby reducing the stresses in the metal plate. To illustrate the effect of active heat sink, the temperature distribution in the top layer at the moment of termination of welding is compared with and without active heat sink. The material is assumed to be elastoviscoplastic, the deformations are small and consist of reversible and irreversible ones. Reversible deformations are related to stresses by the Duhamel - Neumann law. Irreversible strains increase when the von Mises plastic flow condition is satisfied, in which there is a plastic strain rate component responsible for the plastic flow viscosity. The elastic moduli (Young's modulus, Poisson's ratio) and the yield strength are assumed to be temperature dependent. The solution of the mechanical part of the problem is found by the method of simple iterations. For plates with different thicknesses, diagrams of residual stresses are given, located in the center of the plate from the seam to the periphery. As a result of the work, according to the obtained distributions of residual stresses in the plate material, it is concluded that the use of an active horseshoe-shaped heat sink from the near-weld zone when welding thin steel plates reduces residual stresses, therefore it is recommended to use in the welding process. The use of an active heat sink on the reverse side of the plate leads to an increase in the stress level, therefore it is not recommended for use.

Efficient stress integration algorithm of memory surface model with shrinking rule under plane stress field

Reliable nonlinear finite element analysis (FEA) of steel structures requires a constitutive model capable of predicting the cyclic plasticity of structural steels. Steel structure members are typically composed of multiple thin steel plates. The FEA of such structures has frequently used shell elements to capture the bending deformation and reduce the computational complexity, where its stress state can be regarded as the plane stress field. This study provides a constitutive model with a memory surface under a plane stress field for the cyclic plasticity of structural steels. A noble computationally efficient algorithm for stress integration and consistent tangent operator was proposed, where the constitutive equations were linearized after solving some unknown variables. The proposed model was implemented in the Abaqus FEA code. The residual-force convergence rate of the consistent tangent operator is investigated using a single-shell element under simple boundary conditions, where the consistent tangent operator achieves more than a quadratic convergence. The proposed model was validated by comparing the experimental results and FEA results with the proposed model for thin-walled steel members under cyclic loading. The average difference in peak forces between FEA and experimental results was 11.5 % for the local buckling tests and 8.4 % for the shear buckling tests at most. These results suggest that the proposed model provides an accurate prediction for other thin-walled steel structures under cyclic loading.

Performance of thin blast-loaded steel plates after ballistic impact from small-arms projectiles

It is known from real blast-load events that the combined effect of fragment impact and blast loading is more severe than the effect of the blast loading alone. The present study investigates this effect by comparing the blast response of thin steel plates pre-damaged by either ballistic impacts or idealized pre-cut circular holes under similar blast loading conditions. The ballistic impacts were performed with a rifle, firing 7.62 mm APM2 projectiles, and the subsequent blast loading was applied in a shock tube facility. During the blast tests, pressure measurements and two high-speed cameras were used to record the dynamic response of the target plates and allowed for a reliable experimental procedure. To investigate the strength-ductility trade-off dilemma of the material during extreme loading, three different steels with different levels of strength and ductility were used in the tests. Numerical simulations were conducted in an attempt to obtain more insight into the fracture characteristics of the plates.For similar loading conditions and material, the target plates exposed to ballistic impact showed a reduced resistance to fracture during blast loading compared with target plates containing pre-formed circular holes. As for the effect of material strength and ductility, the global deformation decreased, while the localization of plasticity increased, with an increased material strength. The fracture resistance was also observed to decrease with increased material strength. The numerical models were able to capture the main trends observed in the physical tests, i.e., a decrease in fracture resistance with initial ballistic impact, and a reduction in fracture resistance with increased material strength. The numerically predicted crack paths also showed a strong dependence upon the initial cracks caused by the petals from the ballistic impacts.

Experimental Consideration on Suppression Effect of Elastic Vibration in Electromagnetic Levitation System for Flexible Thin Steel Plate with Curvature

Recently, research on non-contact conveyance systems using electromagnetic levitation technology has accelerated. We have constructed an electromagnetic levitation control system that keeps the relative distance between the electromagnet and steel plate constant. To investigate the levitation stability of thin steel plates, we performed magnetic levitation experiments on a thin steel plate with curvature. A physical disturbance was applied to the electromagnet units by vibrators. The electromagnet units were vibrated up and down by a vibrator. We investigated whether the bending magnetic levitation improved the levitation performance even if the magnetic levitation system was in a vibrating environment. We determined that it was possible to realize stable levitation for a steel plate under external disturbances during levitation at the optimal bending angle.

Thin steel plates exposed to combined ballistic impact and partially confined airblast loading

Pre-formed defects created by high-velocity impact have the potential to reduce the structural integrity of lightweight, flexible structures. This study evaluates the effect of complex, partially confined detonations on thin steel plates with realistic pre-formed defects. Target plates containing pre-cut circular holes with a diameter of 8.0 mm are compared to target plates exposed to an initial ballistic impact from 7.62 mm APM2 projectiles. The target plates were exposed to blast loading generated from detonating C-4 inside a steel tube. The stand-off distance was fixed and set equal to the tube radius, where the rear end of the tube was kept open. All blast tests were recorded with several pressure sensors, synchronized with two high-speed cameras monitoring the dynamic response of the target plates. This allowed for a reliable experimental procedure, serving as a benchmark for different numerical methods. For similar loading conditions, the target plates containing initial ballistic impact showed a reduced fracture resistance during blast loading compared to the target plates with pre-cut circular holes. Two different numerical approaches were tested and compared, i.e., a purely Lagrangian particle-based approach and a fully coupled simulation approach using an ALE description of the blast domain. The ALE simulations were found to underestimate the structural response, while the particle-based approach overestimated the structural response.

Comparison of the Efficiency of Cross-Flow Plate Heat Exchangers Made of Varied Materials

This paper discusses a mathematical model for airflow through a cross-flow plate heat exchanger. The exhaust air is used to heat the supply air. Three kinds of plates are considered: made of aluminium, copper, and steel. The purpose of this research was to verify which material used to build the plate heat exchangers uses the exhaust air heat more efficiently. The method of the Trefftz function was used to determine approximate solutions to the analysed problem. The results obtained for 1.2 mm-thick plates and for external winter, summer, and spring–autumn temperatures are discussed. The results indicate that if the efficiency and price of the metals are considered, then steel is the best material for the plate heat exchanger. Thanks to the use of thin steel plates and the reduction in air exchange time to a few minutes, a cheap and efficient cross-flow heat exchanger can be obtained.

Effects of Preheating on Microstructural and Mechanical Properties of Friction Stir Welded Thin Low Carbon Steel Joints

Abstract Friction stir welding of a low carbon thin steel plate was performed with preheating the base material to increase the joining performance. The rotational speed of the tool was set from 1500 to 2000 rpm with a constant travel speed of 15 mm/min and preheating temperature of 50 to 150 °C. The tensile strength of 340 MPa was achieved for the preheated specimen compared with 310 MPa for the non-preheating specimen at the welding speed of 15 mm/min. Electron microscopic images of the preheated joint revealed a remarkable plasticized material flow and dynamic recrystallization, which resulted in the grain refinement that had increased the joining strength. The weld thinning issue was almost eliminated in the preheated welded specimen. However, by increasing the preheat temperature further, the tensile strength decreases due to the formation of defects from excessive heat. The preheated sample fractured at the base metal, revealing a ductile fracture mode.

Effect of Cold Rolling on Microstructural and Mechanical Properties of a Dual-Phase Steel for Automotive Field.

A new advanced dual-phase (DP) steel characterized by ferrite and bainite presence in equal fractions has been studied within this paper. The anisotropy change of this steel was assessed as a progressively more severe cold rolling process was introduced. Specifically, tensile tests were used to build a strain-hardening curve, which describes the evolution of this DP steel's mechanical properties as the thinning level increases from 20 to 70% with 10% step increments. As expected, the cold rolling process increases mechanical properties, profoundly altering the material's microstructure, which was assessed in depth using Electron Backscatter Diffraction (EBSD) analysis coupled with the Kernel Average Misorientation (KAM) maps. At the same time, the process strongly modifies the material planar anisotropy. Microstructural and mechanical assessment and the Kocks-Mecking model applied to this steel evidenced that a 50% strain hardening makes the DP steel isotropic. The material retains or resumes anisotropic behavior for a lower or higher degree of deformation. Furthermore, the paper evaluated the forming limit of this DP steel and introduced geometric limitations to testing the thin steel plates' mechanical properties.

Post-earthquake Fire Behavior of Steel Plate Shear Walls

Recently steel plate shear walls were used as a lateral load-resisting system in multi-story buildings due to their significant stiffness and post-buckling strength. Typical steel plate shear walls consist of a steel plate acting as the main shear-resisting element that is welded to the boundary columns and beams. These shear walls are preferred more and more every day because they are ductile, lightweight, and economical. On the other hand, it is important to examine the behavior of thin steel plate shear walls in the event of a fire that may occur after an earthquake due to natural gas leakage or electrical contact. In this paper, the change in stiffness and displacements of a steel plate shear wall due to fire-induced temperature is investigated using a single-story and single-bay steel plate shear wall ABAQUS model. Furthermore, effect of steel plate yield strength on the shear wall behavior was investigated. In the case of using higher yield strength steel, better behavior in stiffness and beam deflection, and a smaller value in out-of-plane displacement of the plate were obtained. As a result of the analytical study, the out-of-plane displacement in the infill plate increased with temperature. When the model was exposed to high heat for 35 minutes, it was observed that the permanent lateral stiffness was reduced by half. In 40 minutes, it lost almost all of its rigidity. When the steel grade was increased to S275, the loss of rigidity time was prolonged.

Reconstruction of surface pressures on flat plates impacted by blast waves using the Virtual Fields Method

An accurate description of surface pressure loads imposed by blast waves is crucial for the design of the next generation of blast-resistant structures. However, experimental techniques for non-intrusive, full-field surface pressure measurements are not readily available. To address this challenge, a new application of the Virtual Fields Method (VFM) has been explored to reconstruct the surface pressures acting on thin steel plates using full-field deformation measurements of the plate dynamics. A shock tube facility was used to generate a blast-like loading in controlled, laboratory environments, where the plate dynamics were measured using the deflectometry technique. Different blockages at the shock tube exit allowed for varying the spatial distribution and temporal history of the blast loading. The surface pressures were reconstructed from experimentally measured kinematic fields using the VFM. A nearly non-deformable plate equipped with point-wise pressure sensors was also used to obtain a reference, allowing to assess the performance and reliability of the proposed methodology in capturing the surface pressure distributions. Moreover, visualizations of the different blast wave impacts on the plate were obtained using a background-oriented schlieren setup. Finally, the influence of potential error sources was investigated by means of a virtual laboratory using a finite element analysis to generate synthetic input to the load reconstruction analysis. The proposed methodology provided robust, precise predictions using noise-free input from virtual experiments. The presence of both systematic and random errors during the experimental campaign resulted in a reduced pressure reconstruction accuracy, where the peak pressure amplitudes were approximately 10–20% lower compared to the pointwise transducer data. Pressure reconstructions from experimental data still showed qualitatively good estimates of the pressure distributions that were extrapolated from transducer data. Hence, this work highlights the capabilities of a promising methodology to obtain more insight into the effective action of the loading during blast–structure interaction of plated structures.

Seismic behavior of steel-sheathed cold-formed steel shear walls with reinforced end columns

In this study, we investigated six full-scale, steel-sheathed, cold-formed steel shear walls (CFS-SWs), three of which were CFS-SWs with reinforced end columns (CFS-SW-Rs), under reversed-cyclic loading and analyzed their damage modes and mechanical properties. Tests were conducted to compare the seismic performance between the CFS-SWs and CFS-SW-Rs and investigate the effects of the horizontal steel bands and aspect ratio on the seismic behavior of the CFS-SWs, and the effects of the thickness of the steel plates, and the aspect ratio on the seismic behavior of CFS-SW-R. According to the results, CFS-SW-Rs exhibited better seismic performance than CFS-SWs. Specifically, the CFS-SW-R benefited from the high strength and stiffness of the square steel tube end columns that could effectively restrain the thin steel plate, such that the tension band formed by the thin steel plate could be fully expanded. In addition, the shear capacity of CFS-SWs was improved by increasing the number of horizontal steel bands and the aspect ratio, the shear capacity of CFS-SW-Rs was also improved by increasing the aspect ratio and thickness of the sheathing plate.

Ballistic penetration of deforming metallic plates: Experimental and numerical investigation

A combined experimental and numerical investigation is carried out to study systematically the ballistic performance of a metallic plate that deforms continuously under pre-imparted impulsive loading (e.g., due to TNT explosion) before being impacted by a projectile. First, based on a novel experimental method, ballistic impact test of a deforming thin steel plate is performed via an one-stage gas gun; as benchmark, ballistic impact test of a static (non-deforming) thin steel plate via a two-stage gas gun is also performed. Results show that deforming has significant influence on ballistic performance of metallic plates in terms of perforation mode and ballistic limit. Then, based on three-dimensional finite element simulations that are validated against experimental measurements, physical mechanisms underlying the deforming effect are explored. The effects of pre-imparted impulse, the shock resistance of target plate, and the nose shape of projectile on the ballistic performance are also quantified. It is demonstrated that deforming leads to changes of the projectile-target system in three aspects: providing initial kinetic energy to target, changing plastic deformation in dished region, and altering shear force during perforation. The interaction of these three aspects dictates the ballistic performance of a deforming target plate. The results are employed to carry out anti-penetration design for deforming steel plates.

Experimental and analytical investigations of steel shear buckling-inhibited energy dissipation devices

This study presents the development and cyclic performance assessment of steel buckling-inhibited shear yielding devices (St-BISYDs). These devices consisted of thin steel plates as the main energy dissipating elements and modular built-up restrainers as the buckling inhibition mechanism. St-BISYDs are designed to achieve a shear strain of at least 20% without buckling to maximize the energy dissipation potential by minimizing the heat-affected zone (HAZ) and using the bolted connections. Ten specimens with two geometric configurations, namely, hourglass and rectangular, steel plates were experimentally tested under quasi-static displacement-controlled cyclic loading. The proposed restrainers greatly enhanced the cyclic performance of St-BISYDs and helped the St-BISYDs to reach the target shear strain level without significant strength and stiffness degradation under cyclic loading. An analytical study is conducted to predict the force-deformation characteristics of St-BISYDs. Experimental results of the tested specimens are also compared with other similar energy dissipation devices. Further, nonlinear modeling parameters are proposed for the force-deformation response of St-BISYDs which can be directly used in the design practices.

STRENGTHENING OF THIN FLEXURAL MEMBERS USING STRIPS EXTRACTED FROM USED TIRES

Present study investigates the ability of using the damaged tires in the field of structural engineering. The proposed reinforcement material in this study represents an innovative approach to reuse strips extracted from used tires to increase the ultimate flexural capacity of thin flexural members, include thin timber beams and steel plates, satisfying clean environment and economic considerations by consuming the waste materials in the structural field. Results showed that the proposed reinforcement increases the ultimate flexural load value of the thin timber beam specimens in the range of 24.113 % to 30.809 % respectively based on results obtained experimentally and numerically by ANSYS software compared to specimens without reinforcement. Similarly, the ultimate flexural load was increased in the range of 83.95% to 101.7% respectively based on the results obtained numerically and experimentally for the rib type steel plates specimens. Also, deflection has been reduced due to the proposed reinforcement method.

Shock Initiation and Detonation Parameters of Hexanitrohexaazaisowurtzitane (CL‐20)

AbstractExperimental studies of the reaction zone structure in hexanitrohexaazaisowurtzitane (CL‐20) at different initial densities with a multichannel VISAR laser interferometer have been carried out. It is shown that the flow in the reaction zone corresponds to the Zeldovich‐von Neumann‐ Döring theory with a characteristic reaction time of 50 ns. The dependence of the detonation velocity on the initial density is well approximated by a similar line for HMX with a charge diameter of 20 mm. With a decrease in diameter to 4 mm, a sharp drop in the detonation parameters of CL‐20 has been recorded. The initiation of detonation under shockwave action is investigated, and the comparison of data for CL‐20 and PETN has shown that their shockwave sensitivity is quite close. The experiments on the acceleration of thin steel plates by detonating CL‐20 charges have been performed, and it is found that its accelerating ability is higher than that of HMX and retarded RDX.

Toward a Structural Health Monitoring Methodology for Concrete Structures under Dynamic Loads Using Embedded FBG Sensors and Strain Mapping Techniques.

A data-driven-based methodology for SHM in reinforced concrete structures using embedded fiber optic sensors and pattern recognition techniques is presented. A prototype of a reinforced concrete structure was built and instrumented in a novel fashion with FBGs bonded directly to the reinforcing steel bars, which, in turn, were embedded into the concrete structure. The structure was dynamically loaded using a shaker. Superficial positive damages were induced using bonded thin steel plates. Data for pristine and damaged states were acquired. Classifiers based on Mahalanobis’ distance of the covariance data matrix were developed for both supervised and unsupervised pattern recognition with an accuracy of up to 98%. It was demonstrated that the proposed sensing scheme in conjunction with the developed supervised and unsupervised pattern recognition techniques allows the detection of slight stiffness changes promoted by damages, even when strains are very small and the changes of these associated with the damage occurrence may seem negligible.