Multilayer Steel Research Articles

Dynamic Response and Vibration Isolation Analysis of Very Large Floating Building under Wave Action

Taking the buildings above the very large floating structures as research object, the finite element software ANSYS/AQWA was used to carry out hydrodynamic analysis of the single module very large floating structure, and the motion response parameters were obtained. A common multi-layer steel frame structure model and a multi-layer steel frame structure model with three-dimensional vibration isolation bearings were established by using SAP2000, and dynamic time history analysis was carried out for these two steel frame building models. Studies have shown that the motion response of the very large floating structures under the action of waves can not be ignored for the upper building. After the vibration isolation bearing is added to the floating buildings, the natural vibration period of the upper steel frame structure is significantly extended, the inter-layer shear force is slightly reduced, and the inter-layer shear force, interlayer displacement and floor acceleration are increased. Compared with the installation of vibration isolation bearings for land buildings, the vibration isolation of offshore floating buildings is not effective.

Novel principle for improving performance of steel frame structures in column-loss scenario

The progressive collapse of frame structures is typically triggered by column-loss accidents. There is a tremendous need for developing new structures to resist progressive collapse. In this study, a novel principle for improving frame structures is proposed, which is called the partially out-shift plastic zone. Using this principle, a modified steel frame structure with corrugated steel plates is developed. The mechanical properties of the corrugated plates in elastic and plastic stages are investigated, indicating that part of the stress on the beam end can be steadily transmitted. The feasibility of the partially out-shift plastic zone principle is validated by the modified frame. For further optimization, multilayer steel plates and high-strength steels are applied to the modified steel frames. The multilayer configuration eliminates the composite effect so that damage accumulation can be mitigated. Excellent anti-collapse performance is observed. Because the elastic modulus differs little among steels of different strengths, the initial stiffness is hardly affected. Owing to the high strength in the plastic stage, all the peak loads are increased. The second peak load becomes the maximum one.

Research and prospect on column-column connection of assembled multi-layer steel structure

Assembled steel structure residential houses have the significant advantages of light weight, high strength and a high degree of utilization of space, which is an important development direction of the future residential industry for meeting the strategic needs of China’s “four sections –environmental protection”, sustainable development of the construction industry, and the technical requirements of industrialization of housing construction. This paper reviews and summarizes the current status and research progress on the static performance and seismic performance of fabricated multi-story steel column-column connections, including connection types, tests, finite element analysis, etc. These results provide a reference for the further research work and establishing the design methods on column-column connections in the steel structures, as is expected to promote the application of the column-column connections in China’s steel structure engineering.

Microstructure characteristics, strengthening and toughening mechanism of rolled and aged multilayer TWIP/maraging steels

The multilayer structure design of steels can accomplish the purpose of strengthening and toughening. Multilayer TWIP/Maraging steel with high strength, high toughness and interfacial shear strength of 564 MPa is obtained by vacuum hot rolling, subsequent cold rolling and aging treatment. It is found that hot rolling can achieve effective interface bonding ability. Grain refinement, twinning proliferation and dislocation strengthening are generated in TWIP layers with the increase of cold rolling reduction, which can improve the strength and toughness of multilayer steel. However, when the reduction reaches more than 90%, the nanocrystalline and nano twins are appeared in TWIP layers, and plasticity is seriously reduced. The proper adjustment of the cold rolling and ageing process, interface alloying elements diffusion, twinning proliferation, nano-precipitation strengthening, and work hardening can obviously improve the interface bonding ability, strength and toughness, this research provides theoretical basis and experimental support for the lamination design and strengthening-toughening mechanism of a series of metal materials.

Investigation on Dynamics Characteristic of Multilayer Steel Plate Impacted by Projectile

The paper describes a work focused on the process of perforation of multilayer advanced high strength steel (AHSS). A numerical investigation has been carried out to analyze in details the perforation process subjected to normal impact by different nose shapes of projectiles. The perforation process has been simulated by the application of 3D analysis using IMPACT dynamic FE program suite. The comparison on failure modes depending on the projectile nose shape have been studied and evaluated. An appropriate constitutive relation was applied to describe the material behaviour of the multilayer target plate. The study covered different failure modes of perforated advanced high strength steel (AHSS) sheet according to different level of impact velocity ranging from 22 m/s to 78 m/s. The blunt projectile impact towards multilayer target plate leads to generation of plug formation and fragmentation while hemispherical projectile impact shows almost similar petals formation between first, second and third layer.

Understanding and Avoiding Intergranular Fracture Characteristics of Hadfield/Hot-Press-Forming Multi-Layer Steel Sheets

An austenitic Hadfield steel shows highly sustained strain hardening as well as excellent tensile strength and ductility, but its yield strength is relatively low (400 to 500 MPa). In order to overcome this shortcoming, two multi-layer steel (MLS) sheets were fabricated by the hot-roll-bonding of the Hadfield steel with two kinds of martensitic hot-press-forming (HPF) steels. Carburized and decarburized layers were formed near Hadfield/HPF interfaces by the C diffusion from the high-C Hadfield (1.2 pct) to low-C HPF (0.23 and 0.35 pct) layers. The tensile test results indicated that the two MLS sheets were fractured right after the yielding with almost no plastic deformation because the intergranular fracture appeared in the carburized and HPF layers. This intergranular fracture was caused by Cr7C3 carbide precipitation and C segregation at prior austenite grain boundaries as well as considerably high residual stresses generated in both Hadfield and HPF layers. The tempering at 473 K (200 °C) was adopted for relieving residual stresses, while most of grain-boundary carbides remained. The 473 K (200 °C)-tempered MLS sheets showed improved tensile properties over the non-tempered MLS sheets, and well satisfied a rule of mixtures.

Ultra-high strength and excellent ductility in multi-layer steel sheet of austenitic hadfield and martensitic hot-press-forming steels

An austenitic Hadfield steel sheet shows a relatively low yield strength of 0.4–0.5 GPa and serrated flows in spite of excellent tensile strength and ductility along with highly-sustained strain hardening. In order to overcome the shortcomings, a multi-layer steel (MLS) sheet was fabricated by a roll-bonding with an ultra-high-strength martensitic hot-press-forming (HPF) steel sheet. Near the Hadfield/HPF interface, the carburized and decarburized layers were formed by the carbon diffusion from the Hadfield (1.2% of C) to HPF (0.23% of C) layers, and could generate a kind of very thin multi-layers of 35 μm in thickness. All tensile properties of the Hadfield/HPF MLS sheet (yield strength; 946 MPa, tensile strength; 1291 MPa, elongation; 44.5%) were superior to those of the Hadfield sheet. Interestingly, the persistent elongation up to 44.5%, which is higher than that of the Hadfield steel, in the present MLS sheet is a quite unique and interesting characteristic. The simultaneous enhancement of strength and ductility of the MLS sheet was explained by the contributions of 1) populated twin formation, 2) generation of geometrically necessary dislocations (GNDs), and 3) increase of back stress inside thin interfacial layers.

Effect of rubber insertion on impact behavior of multilayer steel fiber reinforced concrete bulletproof panel

Abstract In this study, the effect of para rubber insertion sheet on impact behavior of multilayer bulletproof panel made of steel fiber reinforced concrete was investigated. The objective of inserting rubber sheet into the middle layer was to act as a trapping layer to prevent bullets from ricocheting off the panel. Two test series were carried out: (1) investigation on energy absorption of each materials and (2) investigation on impact behavior of multilayer panel. The results from the 1st test series were used in the design of multilayer panels used in the 2nd series. The target impact energy of the bullet was 607 J. The multilayer panels were designed to have energy level ranging from 450 to 750 J. The panels were subjected impact by 9 mm caliber bullet with velocity of about 398 m/s. Results showed that the panels with impact energy absorption (IEA) level lower than the kinetic energy of the bullet (607 J.) failed by perforation. The panels with IEA level equal to or higher than 607 J. exhibited penetration failure mode with circular spalling at the back surface. There was no bullet ricocheting that occurred beyond this IEA level. At the level of IEA higher than 672 J, the failure mode shifted to penetration without visible damage at the back surface.

Hydrogen embrittlement in multilayer steel consisting of martensitic and twinning-induced plasticity steels

The hydrogen embrittlement behavior of multilayer steel consisting of 7 alternating layers of martensitic (MART) steel and twinning-induced plasticity (TWIP) steel was investigated through variation in the ratio of the hard layer to the soft layer, and the size of the grains according to the autenization temperature. Multilayer steels with a high fraction of MART was predicted to be vulnerable to hydrogen embrittlement, but was found to be less susceptible to hydrogen embrittlement due to the presence of a TWIP layer, which is supported in the center of the multilayer steels. In addition, when the grain size is large, twinning in the TWIP layer and subdivision in the MART layer occur, and so hydrogen embrittlement is promoted due to the trapping of hydrogen. The effect of electrochemically-charged hydrogen on the multilayer steel during deformation was analyzed using electron backscatter diffraction in terms of the microstructure-mechanical property relationships.

Numerical analysis on impact response of ultra-high strength concrete protected with composite materials against steel ogive-nosed projectile penetration

In order to investigate the impact behaviours of ultra-high strength concrete (UHSC) target protected with high-toughness lightweight energy absorption composite materials against the projectile penetration thoroughly, a numerical study using LS-DYNA is conducted at impact velocities between 540 m/s and 810 m/s. The major compositions of FE models are the same as those of experimental specimens which include steel wire mesh reinforced concrete (SWMRC) plates, UHMWPE fibre laminates, aluminium foam sheets and the protected UHSC. Numerical results involving depth of penetration (DOP), impact crater (exfoliated) diameter of SWMRC plates, localized damage and ballistic deviation of the projectiles are obtained and then compared with experimental data, where the numerical results show reasonable agreement with the test results. Based on the validated FE models, the projectile penetration process and the energy evolution between the target and the projectile are studied. In addition, a parametric analysis is conducted to investigate the influence of the arrangement order for present composite materials on DOP and impact resistance of reinforced UHSC target, as well as the ballistic deviation and deformation of the projectile. Results of this study indicate that for the current UHSC target, firstly, the ballistic deviation and projectile deformation are two important factors affecting the impact resistance of the target; secondly, the fibre laminates play a major role in the projectile ballistic deviation and the impact kinetic energy of the projectile is mainly absorbed by the concrete matrix, multilayer steel wire meshes and different densities of foam sheets.

Mechanical properties of multilayer materials

This article presents a study of mechanical properties of multilayer steel materials after the static, impact and cyclic tests, and evaluation of stress and strain behavior of such materials. The studies have shown an increase in the strength, impact strength and the fatigue life with the increase of the number of layers. Also, it has been shown, that high impact strength is maintained down to cryogenic temperatures. That indicates an absence of a definite point for the ductile-brittle transition within such materials. The studies of the stress and strain behavior of multilayer steel materials have shown that the rolling forces increase effect is specific for the production of such materials.

The high-temperature pseudo-invar effect in multilayer steel materials

The paper presents the results of research into Coefficients of Thermal Expansion (CTE) in multilayer steel material produced by hot pack rolling. It has been discovered that the material comprised of interleaving layers of steel features abnormally low CTE values in the direction normal to the rolling plane. A hypothesis has been proposed to explain the phenomenon by an interrelation between normal and tangent stresses generated in the interlayer boundaries within the material. A leading role of reactive stresses is confirmed by the results of the metallographic analysis. It has been shown that cyclic heating at a high temperature provokes recrystallization on the interlayer boundaries due to the difference between the CTE values of the adjacent layers and the high-temperature impact.

Effect of heat treatment on interface behavior of martensite/austenite multilayered composites by accumulative hot roll bonding

ABSTRACTThe 2Cr13/316L multilayered steel (MLS) composites were prepared by accumulative hot roll bonding and heat treatment. The element diffusion, interface bonding mechanism and interface bonding properties of the MLS composites were investigated. The microstructures of the MLS composites before and after heat treatment, are mainly composed of austenite (A), martensite (M), ferrite (F) and little M23C6 carbides. The grain refinement is achieved by accumulative hot roll bonding and heat treatment. The bonding mechanism can be divided into diffusion and recrystallization based on the difference of formation of interfacial grains. The heat treatment has opposite effects on bending strength and shear strength, it is because that softening and interface enhancement of heat treatment have different effects on corresponding bending and shear fracture behavior.

Quasi-static and Dynamic Analysis of Multi-Layered Steel Beams: Core Optimization

Quasi-static and Dynamic Analysis of Multi-Layered Steel Beams: Core Optimization

The Structure of Multi-Layer Composite Material Obtained by the Method of Diffusion Welding

Creation of reliable and durable composite materials made of components with different properties is an urgent task. Such materials include multilayered steel. Alternation of a large number of heterogeneous layers leads to a set of properties that are unattainable for homogeneous steel. Production of such composite materials faces many problems. The use of diffusion welding has created a number of composite materials based on steels of different composition, and their properties allow you to use them in the manufacture of cutting tools. The purpose of this work was to study the structure of multilayer composite materials obtained with the help of diffusion welding and the study of the heat treatment effect on the material structure. During the study, the structures of samples of six different composite materials were studied after annealing and after quenching of the metal. The study showed that the studied materials have a pronounced layered structure with a sharp transition boundary from one layer to another. The technology used in the production of composites ensures the actual absence of the transition zone and the absence of such frequent diffusion welding defects as stratifications, pores, oxide inclusions, etc. The study found that during heat treatment process sizes of carbide inclusions in the composite layers decreases, and their number increases.

Research on the mechanical properties of C45/S235JR multilayer steel systems

Abstract The main objectives of the paper are to determine the mechanical characteristics of the multilayered steel by hot forging. The approach is to obtain bimetallic layered steel by hot forging. This new multilayer system combines the advantages of both materials and reduces the major inconvenience of each one taken separately. Often, the outer part of the piece is made of other metallic material to provide outstanding properties, as well as to reduce the cost price. This is possible due to the understanding of the function of the piece because the piece needs a certain mechanical strength, which does not mean that the whole piece will be made of that material but only that part inner or the outer part of the piece. The rest of the material can be a cheaper material also, in accordance with the requirements of the finished product.

Subsurface Corrosion Detection in Industrial Steel Structures

Corrosion is a central problem for the oil and gas and nuclear industries, affecting pipelines and nuclear waste storage tanks. Reliable methods for timely corrosion detection and integrity evaluation are needed for a range of industrial structures where corrosion under insulation manifests as wall loss. Commercially available detection systems cannot be used in harsh nuclear-storage environments. Moreover, these systems are not reliable for detecting the inner wall thickness of industrial structures made of multiple layers of material, including insulation layers. A novel nondestructive testing method based on low-frequency eddy-current induction was developed and tested on a multilayered steel structure, including an insulating gap. The method enables through-wall thickness measurements between 4 and 16 mm, with a measurement error of 1 mm. The technique is quantitative, nondestructive, and allows the sensor coil to be positioned on the outside of the composite steel structure, which is useful when the interior of an industrial container or pipeline is not accessible.

Numerical impact strain response of multi-layered steel–aluminium plate using signal processing

This paper investigates the impact strain response resulting from the numerical Charpy impact test of double- and triple-layered steel–aluminium plate employing time–frequency analysis. The potential of the laminated steel–aluminium plate in weight reduction is evaluated using a single-layered specimen as a reference. The signal processing technique in the time–frequency domain is capable of revealing the behaviour and strength of the laminated plate. The time domain signal from the numerical Charpy impact test is transformed into the frequency domain using the power spectrum density and time–frequency domain by the Hilbert–Huang spectrum. The relationship of strain energy from the finite element method and the power spectrum density showed the R2 value of 0.8899, indicating that the power spectrum density can be used as an alternative in calculating the strain energy. In this study, the frequency distribution in the power spectrum density was compared with the Hilbert–Huang spectrum. The triple-layered specimen was found to show better performance with 23% higher maximum strain and 11% more strain energy to fracture, compared to the double-layered specimen. Therefore, the analysis in both frequency and time–frequency domains provide a better understanding of the impact behaviour of the double- and triple-layered plate.

Effect of rolling reductions on microstructure and properties of 2Cr13/316L multi-layered steel composite plate by accumulative roll-bonding

Abstract

Interface strengthening and fracture behavior of multilayer TWIP/TRIP steel

Abstract Series of multilayer TWIP/TRIP steels were hot rolled at 1000 °C with different rolling reduction ratios of 25%, 50%, 60%, 70%, 80%, 90% and 94%, and some in-situ reacted Al2O3 whiskers were identified at the clad interface based on selection oxidation. The continuous oxidized films or walls were broken and separated into fine dispersed reinforcements with increasing rolling reduction ratio, which are beneficial to strengthen the interface and toughen the multilayer steels. At low rolling reduction ratio, the thick oxidation walls inhibit the grain growth and alloy element diffusion, leading to the weakness of interface bonding and interface delamination. However, at high rolling reduction ratio, the fine dispersed Al2O3 whiskers bridge the clad interface and induce grain crossing, resulting into strong interfaces and high uniform plastic deformation capacity. Moreover, the grain crossing phenomenon and inner TWIP/TRIP coordination deformation mechanism provide a novel approach for improving fracture elongation of multilayer steels.