Structural Steel Plates Research Articles

Crash Analysis of Aircraft Nose Prototype

This paper presents the comparison of structural deformation of generic metals and the new age composite materials on the aircraft nose during a crash. The analysis is conducted to be able to make more educated predictions of the internal structure damage caused when the airplane has a head on collision with a vertical obstacle (buildings) or when affected by a bird strike. Two nose profiles widely seen nowadays are spherically blunted tangent ogive and elliptical. These nose cones have been designed based on model to prototype ratio on NX CAD. CFD has been performed on the nose designs and solved on ANSYS Fluent for flow visualizations. Materials like Aluminum alloy (which is still widely used in fuselage frames) and Carbon Fiber Reinforced Polymer with epoxy resins, have been applied to the CAD models. These were analyzed for stress, strain and deformation on ANSYS 18.1 by simulating the crash of the nose on a thick structural steel plate. After the analysis, it was inferred that the elliptical nose made of Carbon Fiber Reinforced Polymer has less structural deformation on being crashed.

Effects of strain paths on the fracture forming limit of high strength structural steel sheets

The cruciform two-axial tensile specimen was designed and the two-axial tensile test scheme for different strain paths was developed. The effect of strain paths on the forming limit of high strength structural steel plates was obtained by the DIC method. The results show that for the unidirectional alternating loading test scheme, the equivalent strain of the ultimate strain is less than the sum of the equivalent strains from each step. When the main strain direction of the specimen pre-strain is perpendicular to the final strain path, the forming limit decreases with the increase of the pre-strain.

Effect of Cooling Rate and Finish Rolling Temperature on Structure and Strength of API 5LX70 Linepipe Steel Plate

The present study has investigated the effect of changes in accelerated cooling (ACC) and finish rolling temperature (FRT) on the mechanical properties of high-strength low-alloy (HSLA) Nb-V-Ti steel plate of non-sour API 5LX70 linepipe during the thermomechanical controlled process (TMCP). Tensile test results showed that increasing ACC or reducing FRT enhanced yield and tensile strengths of the subject steel, which was also confirmed by the Vickers hardness test. Microstructure examinations demonstrated that increasing ACC and reducing FRT resulted in a lower volume fraction and a finer size of pearlite. Moreover, an increase in the ACC enhanced the formation of granular ferrite (GF) and fine polygonal ferrite (FPF), while a decrease in the FRT mostly affected the formation of acicular ferrite (AF). In all microstructures, banded structures and particles with a size of approximately 6 μm were observed due to segregation during solidification, where changing the parameters did not affect their formations.

Experimental-based methodology for the double ellipsoidal heat source parameters in welding simulations

The welding numerical simulation involves thermal and mechanical analyses and metallurgical consideration. The thermal analysis determines the transient temperature distribution on the welded part, and its accuracy is relevant for the following analyses on structural integrity, in particular buckling and fatigue failure modes of steel-plated structures. The temperature distribution is strongly influenced by the size and shape of the heat source, which can be represented as a double ellipsoid and defined by Goldak’s parameters. The main difficulty is that the adjustment of these parameters to obtain a suitable temperature distribution is usually determined by trial and error. In this paper, a parametric study is performed to analyze the influence of Goldak’s parameters on the weld bead size for 2D and 3D numerical welding simulations. A method to estimate the parameters of a double ellipsoidal heat source in motion is proposed. An algorithm has been implemented based on the combination of analytical formulation, experimental data, and numerical simulation. As an analytical formulation, the Fachinotti’s solution is used to determine the isotherms. The weld bead dimensions are defined from the melting temperature isotherm of the material. Experimental data, such as the welding process parameters and the weld bead dimensions are input to the algorithm. Numerical simulations of the welding process have been developed to calibrate and validate the method. The numerical simulation results from the obtained Goldak’s parameters by the proposed method are correlated with the experimental results of fillet-welded specimens.

Relation between microstructure and mechanical properties on intercritically deformed low carbon steels

Intercritical rolling is often applied in order to improve the mechanical properties of heavy gauge structural steel plates. However, these products have large temperature and deformation gradients both over thickness and width, being the control of the process very complex. Considering this issue, it is important to analyze the microstructural evolution under intercritical conditions and how the different process parameters like deformation temperature, chemical composition etc. influence on the final mechanical properties. For that purpose, plane strain compression tests simulating intercritical rolling conditions were carried out for a CMn and a NbV microalloyed steel. Tensile tests perfomed for various austenite-ferrite contents prior to the last deformation, show that the reduction of deformation temperature increases strength properties. However, ferrite fractions higher than 25% prior to the last deformation, reduce significantly the ductility. These analyses give the necessary background for the definition of stable process windows that optimize the strength-ductility property balance of intercritically rolled products. Similarly, the estimation of the contribution of different strengthening mechanisms such as, solid solution, grain size and dislocation density, allows the prediction of the yield strength of an intercritically deformed microstructure.

Statistical properties of the yield strength of normal strength hull structural steel plates

The statistical properties were studied of normal strength hull structural steel plates (with a strength level of 235) of a thickness of  50 mm that were manufactured in 1990-1991 at four European steelworks. The study focused on the yield strength, as the available literary sources indicate that in terms of structural strength and design assessment this particular aspect is the most essential property of steel used for ship structures, and, at the same time, its values are characterized by the highest variability. Detailed statistical tests were performed on nearly 2,200 plates. The results of these analyses suggested that for the sample examined herein the mean yield strength value was 308.3 MPa, the standard deviation was 25.24 MPa, the coefficient of variation was 0.0819 (8.19%), the (average) difference bias was 73.3 MPa and the (average) ratio bias was 1.31. It has been shown that both lognormal distribution LN(5.7276, 0.0817) and normal distribution N(308.2589, 25.2444) provide an adequate representation of normal strength hull structural steel plates.

A robust stochastic model updating method with resampling processing

Abstract A robust stochastic model updating framework is developed for a better estimation of uncertain properties of parameters. In this framework, in order to improve the robustness, a resampling process is primarily designed for dealing with the ill sample point, especially for limited sample size problems. Next, a mean distance uncertainty qualification metric is proposed based on the Bhattacharyya distance and the Euclidian distance to fully exploit available information from the measurements. The Particle Swarm Optimization algorithm is subsequently employed to update the input parameters of the investigated structure. Finally, the mass-spring system and the steel plate structures are presented to illustrate the effectiveness and advantages of this proposed method. Discussions on the role of the resampling process have been made through using the measured samples added an ill sample.

Dynamic response measurement of steel plate structure utilising video camera method

Vibration measurement is a common method used to assess a structure’s condition. The basic premise for the detection of damage in a structure is based on vibration measurement, whereby changes of stiffness, vibration mode, and energy dissipation in the system can cause changes in the dynamic response. The vibration measurement is conducted by obtaining the fundamental period to judge the health condition of the monitored structure. This research used the high-speed camera (HSC) to capture the structure motion during the vibration of steel-plated structure. Laboratory experiments were performed on a thin steel plate (600 × 600 × 2.3 mm) and orthotropic steel deck. The HSC was used to measure the resonance frequency of the structure monitored.

Interaction between Microalloying Additions and Phase Transformation during Intercritical Deformation in Low Carbon Steels

Heavy gauge line pipe and structural steel plate materials are often rolled in the two-phase region for strength reasons. However, strength and toughness show opposite trends, and the exact effect of each rolling process parameter remains unclear. Even though intercritical rolling has been widely studied, the specific mechanisms that act when different microalloying elements are added remain unclear. To investigate this further, laboratory thermomechanical simulations reproducing intercritical rolling conditions were performed in plain low carbon and NbV-microalloyed steels. Based on a previously developed procedure using electron backscattered diffraction (EBSD), the discretization between intercritically deformed ferrite and new ferrite grains formed after deformation was extended to microalloyed steels. The austenite conditioning before intercritical deformation in the Nb-bearing steel affects the balance of final precipitates by modifying the size distributions and origin of the Nb (C, N). This fact could modify the substructure in the intercritically deformed grains. A simple transformation model is proposed to predict average grain sizes under intercritical deformation conditions.

Structural Performance of Externally Strengthened Rectangular Reinforced Concrete Beams by Glued Steel Plate

This paper examines both flexural and shear behaviour of eight full-scale (2700×160×100-mm) reinforced concrete rectangular beams subjected to one-third point load. Two types of beams were investigated; Type-E and Type-C. Type-E are reinforced concrete rectangular beams strengthened externally by 1.5mm thick structural steel plate glued to the tensile face with epoxy as adhesive while type-C are reinforced concrete rectangular beams without structural steel plate glued to the tensile face. An average concrete strength of 30N/mm2 at 28 days was used. Required internal reinforcement according to BS 8110-1:1997 was provided for the concrete rectangular beams. Before the beams were externally strengthened, the beam surface to be plated was gritted to take off the cement membrane and to open up the aggregates. Epoxy adhesive was applied as a paste to both the plate and concrete surfaces: the two surfaces were then put together and held in place under pressure of 3.84kN/m2 until the glue was cured. The beams were subjected to flexural testing after 28 days, using loading frame. Each of the rectangular beams support at both ends were subjected to one-third point load, deflection readings were recorded using a dial gauge at every 1.82kN increment. At ultimate load, the beams failed by a crack initiated at the bottom fiber of the beams. From the test results, an average flexural and shear strengths of Type-C beams are; 21.91N/mm2 and 1.05N/mm2 respectively, while type-E beams are; 28.91N/mm2 and 1.39N/mm2 respectively. The results of the investigation showed that flexural and shear strengths of reinforced concrete rectangular beam increased when strengthened externally by bonded steel plate. A straightforward analytical procedure was developed to validate the experiment results of type-E and type-C beams, using rectangular stress block for concrete. Experimental average failure load for beams Type-C and Type-E are 22.44kN and 29.60kN respectively while theoretical failure load for Type-C and Type-E beams are 20.86kNand 31.2kN respectively. Generally, there were acceptably fair correlations between analytical and experimental failure loads of Type-C and Type-E beams.

Structural Performance of Externally Strengthened Rectangular Reinforced Concrete Beams by Glued Steel Plate

This paper examines both flexural and shear behaviour of eight full-scale (2700×160×100-mm) reinforced concrete rectangular beams subjected to one-third point load. Two types of beams were investigated; Type-E and Type-C. Type-E are reinforced concrete rectangular beams strengthened externally by 1.5mm thick structural steel plate glued to the tensile face with epoxy as adhesive while type-C are reinforced concrete rectangular beams without structural steel plate glued to the tensile face. An average concrete strength of 30N/mm2 at 28 days was used. Required internal reinforcement according to BS 8110-1:1997 was provided for the concrete rectangular beams. Before the beams were externally strengthened, the beam surface to be plated was gritted to take off the cement membrane and to open up the aggregates. Epoxy adhesive was applied as a paste to both the plate and concrete surfaces: the two surfaces were then put together and held in place under pressure of 3.84kN/m2 until the glue was cured. The beams were subjected to flexural testing after 28 days, using loading frame. Each of the rectangular beams support at both ends were subjected to one-third point load, deflection readings were recorded using a dial gauge at every 1.82kN increment. At ultimate load, the beams failed by a crack initiated at the bottom fiber of the beams. From the test results, an average flexural and shear strengths of Type-C beams are; 21.91N/mm2 and 1.05N/mm2 respectively, while type-E beams are; 28.91N/mm2 and 1.39N/mm2 respectively. The results of the investigation showed that flexural and shear strengths of reinforced concrete rectangular beam increased when strengthened externally by bonded steel plate. A straightforward analytical procedure was developed to validate the experiment results of type-E and type-C beams, using rectangular stress block for concrete. Experimental average failure load for beams Type-C and Type-E are 22.44kN and 29.60kN respectively while theoretical failure load for Type-C and Type-E beams are 20.86kNand 31.2kN respectively. Generally, there were acceptably fair correlations between analytical and experimental failure loads of Type-C and Type-E beams.

Experimental Study of Residual Stresses in Hybrid Laser Arc and Submerged Arc-Welded 10-mm-Thick Low-Carbon Steel Plates

Abstract Offshore structures are constantly exposed to a multihazard marine environment that threatens their structural integrity. This imposes a high risk for extensive structural failures while various deterioration mechanisms may degrade the available capacity of the structures. Thus, no reliable decisions can be reached regarding design, operation, and survivability of the structures unless a deep comprehension of their fatigue performance is available, including welding-induced residual stresses. In particular, the continuous increase in size of the weldments for the offshore wind industry needs special attention with regard to welding-induced residual stresses, as they can reduce fatigue life, promote distortion, and contribute to stress corrosion cracking. Thus, the current design methods and increased structural dimensions as well as new design and manufacturing methods need to be inspected, understood, and optimized. Related to this, there is a growing need for evaluation of the effect of welding methods with various heat input density distributions. This article deals with the influence of welding method on the welding-induced residual stresses in 10-mm-thick low-carbon structural steel plates. The residual stresses are investigated in hybrid laser-arc welded and submerged arc butt-welded steel plates by means of experimental temperature profile measurements and neutron diffraction measurements and in accordance with existing production procedures. The residual stresses were measured at three different depths in the plates. The goal of the analysis is to gain a comprehensive understanding of the distribution and development of residual stresses in relation to the welding method for better control of the residual stresses and distortion. The repeatability of the neutron diffraction measurements is also investigated and reported in this article.

Material properties and stress-strain curves for titanium-clad bimetallic steels

Titanium-clad (TC) bimetallic steel plate is a composite steel plate manufactured by metallurgically bonding a titanium cladding layer to a base structural carbon steel plate commonly through hot-rolling process. Such advanced bimetallic product takes advantages of the weldability, formability, thermal conductivity and good mechanical properties of structural carbon steel and the excellent corrosion and impact resistance of titanium in a symbiotic fashion, so it possesses structural performance, environmental and economic benefits compared with pure structural carbon steel and titanium. TC bimetallic steels have been applied wisely in many engineering structures, but their research studies in engineering application in the open literature are still very limited. The aim of this paper is to present an experimental study for investigating the material properties and stress-strain curves of TC bimetallic steels. A series of experimental tests including tensile coupon tests, bend tests, Charpy impact tests and hardness tests on the TC bimetallic steel specimens are undertaken and reported. Their basic mechanical properties and stress-strain curves are obtained. The influence of the clad ratio that is defined as the ratio of the thickness of cladding layer to the total plate thickness on the stress-strain curves are studied. Through the interpretation of the collected experimental data and supplementary finite element analysis data of tensile coupon tests, a three-stage model for predicting the stress-strain curves of the TC bimetallic steels over full range of tensile strain are developed. The proposed model is defined by using the four basic parameters including three basic Ramberg-Osgood parameters and an exponent parameter, together with some additional parameters that can be expressed in terms of these basic parameters. The predictive expressions for the basic and additional parameters are also proposed in this study. The accuracy of the proposed model is demonstrated by comparing its predictions with the experimental stress-strain curves of the TC bimetallic steels with various clad ratios.

Application of two-dimensional wavelet transform to detect damage in steel plate structures

Wavelet Transforms (WT) have been receiving an increasing attention for the detection of damage in structures based on vibration response. The existence of the problem of boundary distortion in WT may lead to unreliable results at and around the boundaries of the structure. Previous studies have applied methods such as signal extension, zero padding and windowing to avoid border distortion. However, these methods try to avoid border distortion by distorting/reducing the original signal to prevent the distortion at the boundaries of the signal from occurring, thus altering the original signal and leading to unreliable damage identification. In this study, a WT-based method is proposed to solve boundary distortion problem. To achieve this, the mode shape difference of a structure is applied for WT decomposition. By using mode shape difference, the problem of border distortion is solved by reducing the effect of sudden change in stiffness that occurs at boundaries. A two-dimensional Continuous Wavelet Transform (CWT) is applied to decompose the difference between the damaged and the undamaged first mode shape signal. The damaged mode shape is subtracted from the undamaged mode shape to obtain the difference, and the difference is decomposed to detect and locate the damage. This method is demonstrated via numerical and experimental examples of a square steel plate. The reliability of the method is demonstrated through different damage intensities and locations. The numerical study involves applying a square plate model with two boundaries formats: all four sides fixed, and two opposite sides fixed and free. The mode shape and mode shape difference are decomposed and the coefficients of the two are compared to show the advantage of this method. The experimental example was applied to a square steel plate with all four sides fixed to verify the efficiency of the method. The numerical results showed that the problem of boundary distortion is resolved by using the mode shape difference and damage at all locations are detected, while applying mode shape provided unreliable results for both numerical models even at 25% severity. The sensitivity of the proposed method to noise is investigated by introducing various levels of signal to noise ratios and showed the detection of damage with 5% severity when mode shape difference was applied in presence of noise.

Research on Measurement of Loss Factor based on Transient State Decay Method

As an important parameter in application of the Statistical Energy Analysis (SEA), loss factor can measure damping characteristics of a system and determine the ability of vibration energy dissipation. First, the experimental models of steel plate structures are established. And then, the loss factor test is carried out based on transient state decay method. Finally, the variation characteristics of loss factor with medium, thickness and size of structures are explored. The results show that: (1) The loss factor of steel plates has the characteristics that larger at low frequency and small at high frequency, it decreases gradually with the increase of frequency. (2) For the same structure, the loss factor tested in water is greater than the loss factor tested in air. (3) The loss factor increases with the raise of thickness of plates when its cross-sectional dimension is constant.

Thread effects on the stiffness of bolted shear connections

ABSTRACT This paper investigates the effects of bolt threads on the initial and final stiffnesses of double-shear bolted connections through laboratory tests and finite element (FE) analyses. Nineteen specimens composed of 4.7 mm and 8.0 mm thick structural steel plates with bolt diameters of 20 mm and 30 mm having varying end distances are studied. The investigation, which involves shank and thread bolted connections, has found that the threads reduce the initial stiffness but increase the final stiffness. The FE analysis shows that the reduction in the initial stiffness is due to the bolt threads cutting into the connected plate, increasing the initial displacement. However, the same factor moderates the softening behaviour of a thread bolted connection as it approaches its ultimate capacity. The FE simulation shows that in certain cases this newly discovered phenomenon is caused by the threads restraining the crimpling of the plate material downstream of it. The present modelling technique significantly improves the simulation results of bolted connections tested by independent researchers, compared to their own modelling techniques including that which attempts to simulate the thread effects by reducing the diameter of the bolt model. The “elastic” stiffness values obtained from the present laboratory tests are compared against the Eurocode's provision based on the ASTM definition, and ad hoc stiffness formulae are proposed for shank and thread bolted connections.

Effect of stress-induced magnetization on crack monitoring by self magnetic flux leakage method

Fatigue cracks could occur in the material of offshore and marine structures that are cyclically loaded. These cracks occur due to the cyclic stresses induced by the waves causing premature failure. Monitoring these fatigue cracks using a wireless system gives the opportunity to guarantee the integrity of the structure without manual inspection, making this a safer way of inspection. In addition, inspection is very costly due to the man hours and because of the fact that the locations of fatigue cracks are mostly not easily accessible. Also, visual evaluation of the crack length can be difficult to assess, which could result in early retirement of structures or unnecessary and costly maintenance. A wireless crack monitoring system based on the Self Magnetic Flux Leakage (SMFL) method could be a solution for this problem. This method suggests that the ferromagnetic material is passively magnetized by the Earth’s magnetic field and the magnetic signal changes when a crack appears in the material. The measured data is sent wirelessly to the control room of the marine structure. Here, the data can be assessed to determine the size of the fatigue crack. With this information, it can be decided what course of action should be taken to ensure the integrity of the marine structure as long as possible. This will result in a safer way of working and being economically more efficient. For accurate crack sizing, the SMFL must be interpreted correctly. During cyclic loading the stresses in the material change, affecting the magnetic signal. This is called the stress-induced magnetization. The aim of this research is to investigate the effect of stress-induced magnetization on the SMFL in the stress concentration zone of a structural steel plate, and its implications for crack monitoring by the SMFL method. The measured stress magnetization curves are obtained by means of an experiment. In this experiment, a steel plate with an elliptical hole is cyclically loaded up to the yield stress. The magnetic signal is measured in a grid around the hole. The results show a maximum variation of 25 µT. Depending on the application, the stress-induced magnetization may need to be considered for the interpretation of the measured signals for crack monitoring using the SMFL method.

Numerical modeling of the pattern and wear rate on a structural steel plate using DEM

The discrete element method (DEM) has been implemented to model abrasive wear on steel plates that interact with bulk solids, such as crushed copper ore. The Archard model was used to predict the rate and the wear pattern on a structural steel plate A37-24 ES under different types of copper ore. One of the key steps of the methodology consists of the proper characterization of the granular medium to calibrate the numerical model. The numerical results obtained are in good agreement with the values of the standard test method for measuring abrasion using the wear wheel (ASTM G65). This allows to establish that the model is able to correctly predict the phenomenon of abrasion wear. There are many processes where wear limits the life of equipment, affecting its productivity and operating costs. A numerical method such as the one developed here could be used to reduce costs in the design and operation of mining equipment, looking for configurations appropriate to the actual working conditions.

Verification of Compressive and Flexural Behavior of Corrugated Steel Plates Composite Section with SFRC

To increase the span of the buried structure using corrugated steel plates, concrete composite section is being increasingly applied; however, it increases the risk of brittle fracture of the structure because bending and compressive stress by moving loads such as overpassing vehicles act simultaneously. In this study, steel fiber reinforced concrete was applied to the composite section to secure the ductility and to analyze the compression and flexural behavior experimentally. As the structure becomes larger, the flexural and compressive stress act simultaneously on the composite section of the corrugated steel plate structures. This study experimentally verified the compressive and flexural behavior of the steel plate composite section with steel fiber reinforced concrete. Moreover, the structural performance of the revised corrugated steel plate composite section applied with SFRC and triangular confinement rebar to control brittle failure at the lap joints and enhance serviceability were experimentally verified. The test results show that the compressive strength of the composite section increased by 10% or more when the fiber reinforced concrete was applied. The concrete composite section under axial loads is dominantly performed by the resistance of the reinforced concrete section without the contribution of steel plate up to the cracking load, but after the cracking load, the core concrete section inside the confinement rebar and the lap connected steel plate become resistant to the external loads. The flexural behavior under yield loads was dominated by the internal resistance moments of the steel bars and corrugated steel plates, and then the concrete section as well as the rebar and steel plates was partially contributed to the flexural strength after yield loads. Keywords: Compressive Strength, Flexural Strength, Corrugated Steel Plate Composite Section, Steel Fiber Reinforced Concrete

Numerical modelling of underwater structural impact damage problems based on the material point method

Based on the material point method (MPM), the numerical modelling of the steel plate structure under the near-field contact explosion in underwater was studied. The equations of state, constitutive equation and failure mode are used to analyse the destruction and failure process of materials. Numerical studies analyse the impact of explosive loads on underwater steel plates under different operating conditions and calculate the distribution of pressure and particles. The results show that the steel plate will produce a large plastic deformation and eventually form a punch inge, and the existence of steel plate medium has obviously helped the whole system to weaken the shock wave, which can reduce the damage by about 20%. It can serve as a useful reference for the protection of underwater systems.