Mechanical Properties Of Steel Plates Research Articles

Microscopic defects formation and dynamic mechanical response analysis of Q345 steel plate subjected to explosive load

As the basic protective element, steel plate had attracted world-wide attention because of frequent threats of explosive loads. This paper reports the relationships between microscopic defects of Q345 steel plate under the explosive load and its macroscopic dynamics simulation. Firstly, the defect characteristics of the steel plate were investigated by stereoscopic microscope (SM) and scanning electron microscope (SEM). At the macroscopic level, the defect was the formation of cave which was concentrated in the range of 0–3.0 cm from the explosion center, while at the microscopic level, the cavity and void formation were the typical damage characteristics. It also explains that the difference in defect morphology at different positions was the combining results of high temperature and high pressure. Secondly, the variation rules of mechanical properties of steel plate under explosive load were studied. The Arbitrary Lagrange-Euler (ALE) algorithm and multi-material fluid-structure coupling method were used to simulate the explosion process of steel plate. The accuracy of the method was verified by comparing the deformation of the simulation results with the experimental results, the pressure and stress at different positions on the surface of the steel plate were obtained. The simulation results indicated that the critical pressure causing the plate defects may be approximately 2.01 GPa. On this basis, it was found that the variation rules of surface pressure and microscopic defect area of the Q345 steel plate were strikingly similar, and the corresponding mathematical relationship between them was established. Compared with Monomolecular growth fitting models (MGFM) and Logistic fitting models (LFM), the relationship can be better expressed by cubic polynomial fitting model (CPFM). This paper illustrated that the explosive defect characteristics of metal plate at the microscopic level can be explored by analyzing its macroscopic dynamic mechanical response.

Mechanical properties of steel plate compression joint under seawater corrosion and welding

ABSTRACT Seawater corrosion and welding can together cause significant damage to marine structures, thereby deteriorating the mechanical properties of steel and the bearing and deformation capacities of the overall structure. Therefore, in this paper, the electrochemical corrosion method was used to simulate the actual seawater corrosion, and the corrosion distribution characteristics and compressive mechanical properties of D36 steel plate welded joints in seawater were studied. Through scanning electron microscopy, we analysed the influence of welding and corrosion, that is, the different weld angles and degree of corrosion on the damage distribution of welded joints. The bearing and deformation capacities of the structure, as well as the failure mode and failure position of the structure are determined. Finally, through a quadratic regression analysis, the experimental results were used to develop a generalized constitutive model of corroded and welded damaged steel with corrosion degree and weld angles as the variables.

Dimensionality Reduction for Machine Learning Using Statistical Methods: - a Case Study on Predicting Mechanical Properties of Steel Plates

Dimensionality Reduction for Machine Learning Using Statistical Methods: - a Case Study on Predicting Mechanical Properties of Steel Plates

Investigation of the mechanical properties of steel plates with artificial pitting and the effects of mutual pitting on the stress concentration factor

Pitting corrosion in steel structures reduces the cross-sectional area of steel members and generates stress concentrations, which degrade the bearing capacity of steel members, thereby causing structural collapse. This paper studied the relationship between pitting corrosion and the stress concentration factor (SCF) under tensile loading and the effects of pitting corrosion on the mechanical properties and deformation of specimens. First, mechanical drilling and milling methods were used to fabricate artificial pitting on small specimens to simulate natural corrosion. The effects of the pitting depth and diameter on the mechanical properties and deformation capacity of the specimens were studied. Then, a digital image correlation (DIC) system was employed to measure the surface strain field of the specimens, and the differences between the local deformation around the pitting and the overall deformation of the specimen were investigated. Finally, a numerical method was applied to study the effects of pitting size parameters, pitting position parameters, plate thickness and double pitting on stress concentrations. The results showed that the reason for the degradation in the mechanical properties and deformation ability of the specimen was the joint effect of cross-sectional reduction and stress concentrations around the pitting. A double yield phenomenon was observed because the deformation near the pitting occurred more rapidly than the deformation of the rest of the specimen. The maximum value of the SCF occurred when the pitting was at the edge of the component. If the ratio of the plate thickness to the corrosion pitting depth was less than 5, the effects of the plate thickness on the stress concentration were obvious. The location of the critical area around the double pitting was affected by the position parameters.

Mechanical Properties of SS400 Steel Plate at Elevated Temperatures

This paper presents the experimental test results on mechanical properties of steel plate grade SS400 at elevated temperatures. The steel is often used as structural steel due to its weldability and machinability. The steel plates were heated by a high frequency heating system to reach specific temperatures before being tested on a tensile testing machine. Five different temperature conditions were used, namely room temperature, 100°C, 300°C, 500°C and 600°C. The data of mechanical properties measured for SS400 steel plates at various temperature conditions were recorded and analysed. The research showed that when the temperature is increased, the force in tensile test is decreased while the strain is increased. The observation and the data were then used to setup the stress – strain – temperature relation for formability study of SS400 steel plates. The same method can be used to establish the mechanical properties at elevated temperatures.

Square CFST columns under cyclic load and acid rain attack: Experiments

As China's infrastructure continues to grow, concrete filled steel tubular (CFST) structures are attracting increasing interest for use in engineering applications in earthquake prone regions owing to their high section modulus, high strength, and good seismic performance. However, in a corrosive environment, the seismic resistance of the CFST columns may be affected to a certain extent. This study attempts to investigate the mechanical behaviours of square CFST members under both a cyclic load and an acid rain attack. First, the tensile mechanical properties of steel plates with various corrosion rates were tested. Second, a total of 12 columns with different corrosion rates were subjected to a reversed cyclic load and tested. Third, comparisons between the test results and the predicted ultimate strength by using four existing codes were carried out. It was found that the corrosion leads to an evident decrease in yield strength, elastic modulus, and tensile strain capacity of steel plates, and also to a noticeable deterioration in the ultimate strength, ductility, and energy dissipation of the CFST members. A larger axial force ratio leads to a more significant resulting deterioration of the seismic behaviour of the columns. In addition, the losses of both thickness and yield strength of an outer steel tube caused by corrosion should be taken into account when predicting the ultimate strength of corroded CFST columns.

Numerical Analysis of Boiler Fabricated from Ship Breaking Yard Steel Plate and Minimizing Workplace Casualties in Bangladesh

High numbers of workplace casualties and injuries are reported each year in Bangladesh due to explosion of the boiler in the rice husking mills, as well as other industries including garments factories. Rice husking mills are using locally made steam boilers, which are fabricated of steel plate obtained from the ship breaking yard and not equipped with standard safety devices and fittings. The motivation of this work is to find the causes of explosion of those boilers and provide some modifications to reduce workplace casualties. In this regard, some rice husking mills in the rural area of Bangladesh are inspected to evaluate the working and operating condition of the boilers. The mechanical properties of steel plate obtained from the ship breaking yard is found by tensile test in UTM and those mechanical properties are used in numerical analysis of the boiler, which is currently operating in the rice husking mills and fabricated locally from same source of steel plate. The FEA tool ANSYS workbench is used in numerical analysis of the boiler to evaluate maximum working stress due to thermal and static pressure load, which is found below the yield strength of the test specimen. From the instantaneous pattern of explosion in all boiler incidents and result of the numerical analysis, it is concluded that strength of steel plates obtained from the ship breaking yards is not the cause of boiler explosion, operational malfunction and lack of safety measures are the main causes of boiler explosion in Bangladesh especially in the rice husking mills. To improve safety measures, modification cost of the boiler is evaluated by modifying a locally fabricated steam boiler, which is also made of same source of steel plate and currently operating in the rice husking mill. The modification cost to install safety devices and fittings is found about Tk. 25,000 ($300), which is easily affordable by rice husking mill. Finally, some steps are recommended to reduce boiler explosion and concluded that steel plates obtained from the ship breaking yards have enough mechanical strength and can be used to fabricate low-pressure boilers.

Influence of zinc coating on anisotropic mechanical properties of hot dip galvanized steel sheet DP600

The influence of zinc coating on the anisotropic mechanical properties of hot dip galvanized steel sheet DP600 is studied by tensile test. The results show that zinc coating makes the yield strength of the steel plate decrease, but has no obvious influence on the hardening index. Compared with the bare steel sheet, in the direction of R00 direction parallel to the rolling direction, the tensile strength and yield strength of galvanized steel sheet decrease, while the elongation and thickness anisotropy coefficient increase. After comprehensive analysis, it is found that the plastic deformation ability has decreased in the direction of R00 direction. and the plastic deformation ability decreases after comprehensive analysis. In the R90 direction, the mechanical property parameters of galvanized sheet all increased, and zinc coating improves the plastic deformation ability of the steel sheet. However, in the R45 direction, the variation extent of the mechanical property parameters of galvanized steel sheet is between R00 and R90. Therefore, the influence of zinc coating on the mechanical properties of steel plate is closely related with the rolling direction, which also illustrates that the adhesion strength between the galvanized layer and steel plate substrate is affected by the surface microstructure of rolled steel sheet.

Effect of Microstructural Characteristics of Thick Steel Plates on Residual Stress Formation and Cracking during Flame Cutting

Thick wear-resistant steel plates are commonly used in demanding conditions, such as in the mining industry. In harsh environments, a high degree of both toughness and hardness is required, which extends the service life of the components but also makes the production of the plates difficult. Flame cutting is a generally applied cutting method in the heavy steel industry since it enables the cutting of thick steel plates at high production rates. However, flame cutting may cause cracks in the cut edge of the steel plates, leading to rejects for the steel industry and end-users. In addition, cutting generates a heat-affected zone at the cut edge, where volumetric and microstructural changes and hardness variations take place. A steep thermal gradient, generated during flame cutting, also produces high residual stresses on the cut edge. The goal of this study is to examine how microstructural features contribute to the residual stress formation and cracking probability of thick steel plates. Specific microstructural features can make the plates prone to cracking and tend to produce undesired stresses during the cutting process. The residual stress profiles of flame-cut specimens were measured using the X-ray diffraction method. In addition, the mechanical properties of steel plates were evaluated. The microstructures of the cut edge and the base material were characterized by electron microscopy. Results indicate that the shape of the prior austenite grains has an effect on both the cracking probability and residual stress formation. Longitudinally oriented prior austenite grain boundaries combined with a high residual tensile stress state provide potential sites for cracking.

Effect of Thin Polymer Coatings on the Mechanical Properties of Steel Plates

The influence of powder coatings based on an epoxide polyester mixture on the mechanical properties of the plates made of rolled sheet steel is studied. The influence of 100-μm-thick coatings on the mechanical properties of specimens 0.7–1.5 mm thick is considered. The bending and tensile tests performed at room and elevated temperatures show that the thin coatings weakly affect the mechanical properties of the plates. In particular, the stiffness of the coated plates during tension and bending remains almost the same despite the fact that the elastic modulus of the coated plates is always slightly lower than Young’s modulus of steel because of an increased specimen thickness determined with allowance for the presence of a coating. The influence of the coatings is substantial in compressive stability tests. Under supercritical deformation conditions, the bearing capacity of the coated plates decreases substantially, and their critical stability load on the loss of stability falls by 20–30% (depending on the substrate thickness). This effect can be explained by the influence of the residual thermal stresses that appear in the specimens during coating deposition.

Circular concrete filled steel tubular (CFST) columns under cyclic load and acid rain attack: Test simulation

Concrete filled steel tubular (CFST) structure attracts increasing engineering applications in earthquake prone regions due to its high section modulus, high strength, and good seismic performance. However, the seismic resistance of CFST columns may be affected by the environmental corrosions, such as acid rain attack. This paper makes an attempt to investigate the performance of CSFT columns with circular sections under both a cyclic load and an acid rain attack. First, the tensile mechanical properties of steel plates with various corrosion rates were tested. Second, a total of 12 columns with different corrosion rates were tested subjected to a reversed cyclic load. It was found that the corrosion leads to not only a loss in wall thickness but also an evident decrease in yield strength, elastic modulus, and tensile strain capacity of the steel coupons, and also to a significant deterioration in the load carrying capacity, ductility, and energy dissipation of the CFST columns. The larger the axial force ratio, the severer deterioration of deformation capacity of the columns.

Study on the degradation of mechanical properties of corroded steel plates based on surface topography

Degradation laws of mechanical properties of corroded steel plates were studied by experimental method and numerical simulation method based on surface topography in this paper. First, Q235 steel plate was subject to accelerated corrosion with artificial salt spray, and the characteristics of the surface of corroded steel plate were measured by three-dimensional morphology observation instrument to obtain the values related to corrosion damage parameters, and the relationship between the surface characteristic parameters and the corrosion rate was established. Then the stress-strain curves and mechanical properties of the corroded steel plates were obtained by monotonic tensile test. Finally, the mechanical properties of steel plates with real corroded surfaces were studied by numerical simulation method with reverse engineering software Geomagic Studio and finite element software ANSYS, and the stress concentration phenomenon caused by corrosion pit was discussed. The results showed that: (a) the corrosion rate is within 15%, the stress-strain curves have obvious yield plateaus; (b) and with the increase of corrosion rate, yield plateaus, yield strength, ultimate strength, and fracture strength of corroded steel plates does not decrease much, but ductility significantly decreases; (c) when the corrosion rate is over 15%, all the mechanical property index significantly decreases; (d) the constitutive model was established, and the law of the variations of the parameters of the model was summarized; (e) the numerical simulation method is feasible compared with the experimental results.

Effect of Trace Cerium on Microstructures and Mechanical Properties of 690 Mega Pascal Steel

The effect of trace cerium on microstructures and mechanical properties of 690MPa steel plates used for engineering machinery was researched by the comparative analysis of the microstructures, inclusions, and comprehensive mechanical properties of the steel plates after rolled, quenched and tempered. The result shows that trace cerium can improve the yield strength, tensile strength of rolled and quenched steel plates, and low temperature impact toughness of the tempered steel plate significantly, but has little effect on the yield strength and tensile strength of the tempered steel plates. The cerium-bearing steel has finer grain size, less inclusion contents and more spheroidal than that of cerium-free steel. The yield strength of 10 megapascal, the tensile strength of 20 megapascal for rolled plates and the yield strength of 130 megapascal, the tensile strength of 100 megapascal for quenched plates was improved by the addition of cerium. In spite of this, the cerium has little effect on the yield and tensile strength but improved about 50 Joule impact energy values under-40 centigrade degree temperature after the plate was tempered at the temperature of 620 centigrade degree. It has the same rules of the plates tempered at the temperature of 580 centigrade degree.

Influence of some Oxide Coating Layers on the Mechanical Properties of Steel Plates

The paper presents a vibroacoustic method to determining the stiffness of coated steel with various materials such as metal oxides, metallic paints, polymers etc and Young's modulus for coating materials. The method consists in measuring the dynamic response of the steel in the form of a rectangular bar subjected to external impulse. One of the latest non-destructive experimental techniques in this field is based on the analysis of vibrating signal response recorded with a condenser microphone. A Fast Fourier Transform algorithm is used for processing the sampled signals. Knowing the mechanical properties of steel plates prior to coating with metal oxides, and determining the same properties after coating, can be obtained the mechanical properties of metal oxides and their influence on the properties of the ensemble.

Nonlinear Analysis for RC Beams Strengthened by Externally Bonded Steel Plates with Bond-Slip

The RC beams strengthened by externally bonded steel plates are regarded as composite beams which consist of steel plates and reinforced concrete with bond-slip. Based on the deformation compatibility relationship between steel plates and reinforced concrete, the constitutive relationship which can reflect the mechanical properties of steel plates and reinforced concrete and the bond-slip constitutive law, a nonlinear differential equation for the beam, expressed in the form of the tensile force of steel plates, is derived. A nonlinear analytical solution under the double concentrated load of the RC beams strengthened by externally bonded steel plates is obtained. By which a coordination coefficient in the form of the characteristic value of the beam is deduced. By using the coordination coefficient, a practical nonlinear analysis method, which can exactly reflect the bearing capacity and deformation of the beam is established.

Experimental investigation of the effect of vibration on mechanical properties of 304 stainless steel welded parts

Some of the problems that occur during the welding process include the creation of coarse grains in the weld structure and the hardening of the weld region, which reduce the strength and impact resistance of the welded parts. One technique to improve the mechanical properties of weld is the application of mechanical vibration to the molten pool. In this article, the effect of vibrating the part during welding on the mechanical properties of steel plates has been investigated in the tungsten inert gas (TIG) welding process. The plate is made of stainless steel 304 with 2 mm in thickness. A filler material has also been used for welding so that the effect of vibration can be observed on the weld pool region. The experimental tests have been performed under different welding conditions with respect to voltage, current, welding speed, vibrations amplitude, and frequency. Then, the resultant mechanical properties of the tested parts were measured. Also, the microstructure obtained by applying the vibration has been examined. Based on these experimental results, the effect of mechanical vibration on mechanical properties of the weld was investigated. Moreover, considering the mechanical properties obtained from these experiments, the optimum values of amplitude, frequency, and welding speed were determined.

Influence of Direct Quenching on Microstructure and Mechanical Properties of Steel Plate for Large Oil Storage Tanks

The influence of direct quenching on microstructure and mechanical properties of high performance steel plates for large oil storage tanks was studied. The direct quenched and tempered (DQ&T) steel plates were rolled at different finish rolling temperatures (1113 and 1173 K), and their microstructures and mechanical properties were compared with those of reheat quenched and tempered (RQ&T) steel plate. The optical microscopy of the DQ steel shows deformed grains elongated along the rolling direction, while complete equiaxed grains are visible in RQ steel. Transmission electron microscopy (TEM) of the DQ steel shows refined lath martensite with high density of dislocations, which acts as preferred precipitation sites for NbC or Nb(C,N) particles during tempering. In all the plates, strength decreases with increasing tempering temperature. The strength of RQ steel increased significantly compared with that of DQ steel at the higher tempering temperature, which leads to better tempering resistance in DQ steels. The optimum combination of strength and toughness (yield strength (YS) reaches 585 MPa, tensile strength (TS) 667 MPa, and Charpy impact energy at 253 K of 291 J) in the DQ steels is achieved by quenching at 1113 K and tempering at 923 K.

Phase Transformation Rule, Microstructure and Properties of JG590 High Strength Steel

The phase transformation rule, microstructures and properties of JG590 high strength steel produced in Jinan Iron and Steel Co. ltd. have been investigated in this paper. When the chemical composition of steel are given, the cooling rates after finished rolling affect on the properties of steel greatly. The yield strength and tensile strength increasing, the elongation and reduction of area decreasing as increasing of cooling rates after rolling. The main cause is due to appearance and increasing of Bainite and Martensite other than Ferrite and Pearlite in room temperature. The finished rolling temperature have distinct effects upon the mechanical properties of steel plates. Finished rolling at different temperature with the 0.5°C/s cooling rate, the tensile strength vary in 599-698MPa, the yield strength changed from 412 MPa to 536MPa. The elongation is between 30.4-40.5%. But when finished rolling at different temperature with the 2.0°C/s cooling rate, the tensile strength vary in 747-784MPa, the yield strength changed from 441 MPa to 601MPa. The strength index can both meet the requirements of employ. But the elongation is only 18.7-24.5%. This is related with production of lots of Bainite microstructure more than 2°C/s cooling rate. In the procedure of manufacture of JG590 high steel, the quickly cooling rate should be avoided to keep suitable microstructure and good elongation and toughness.

On the processing of Fe–C–Mn–Nb steels to produce plates for pipelines with sour gas resistance

Several steel plates in the as-hot rolled plus cooled condition were studied, in order to evaluate the impact of the steelmaking route and the controlled thermomechanical processing plus the cooling media, on the resulting microstructure and mechanical properties of steel plates, which will be processed to produce large diameter steel pipes with sour gas resistance. The steelmaking route to produce the slabs involved the use of 100% sponge iron which was feed into an electric arc furnace, vacuum degassed, ladle treated and continuously casted. After soaking, a controlled thermomechanical processing schedule was applied to steel slabs followed by air or accelerated cooling of plates. Most of the resulting steel plates cooled in air showed a banded structure, which sometimes presented a central segregation region. The worst plates with a central segregation region showed intermetallics compounds in it. After modifications of the steelmaking route and to the controlled thermomechanical/cooling schedule, a steel plate with a ferritic microstructure plus 0.5 vol% of bainite was obtained. This microstructure together with the resulting mechanical properties, fulfilled the API grade 5L X-70 properties, required in modern steel pipes demanded by the oil industry.

冷間プレス曲げによる鋼板の材質変化とその改善に関する研究

This research aims at clarifying the effects of cold press-bending on the mechanical properties of steel plates in order to reason the fact that brittle fracture has been witnessed in recent experiments of steel box-columns produced by cold press-forming. The changes in mechanical properties were investigated in the press-bent corner and its welded joint to a diaphragm plate. It was found that the cold press-bending causes the increase in strength, the decrease in ductile elongation capacity, and the remarkable reduction in impact energy absorption in the outer surface. However, these unfavorable mechanical properties related to brittle fracture were completely recovered by postheating of 850℃-normalizing.