High Strength Steel Plates Research Articles

Experimental and Numerical Study on the Protective Behavior of Weldox 900 E Steel Plates Impacted by Blunt-Nosed Projectiles

To demonstrate the importance of incorporating Lode angle into fracture criterion in predicting the penetration resistance of high-strength steel plates, ballistic tests of blunt-nosed projectiles with a diameter of 5.95 mm impacted 4 mm thick Weldox 900 E steel plates were conducted. Impacting velocity range was 136.63~381.42 m/s. The fracture behavior and the ballistic limit velocities (BLVs) were obtained by fitting the initial-residual velocities of the projectiles. Subsequently, axisymmetric finite element (FE) models parallel to the tests were built by using Abaqus/Explicit software, and the Lode-independent Johnson–Cook (JC) and the Lode-dependent ASCE fracture criterion were incorporated into the finite element model for numerical simulation. Meanwhile, to verify the sensitivity of the mesh size in the numerical simulation, different mesh sizes were used in the shear plug area of the target. It can be found that Weldox 900 E steel has obvious mesh size sensitivity by comparing the experimental results and numerical simulation, and the JC fracture criterion and the ASCE fracture criterion predicted similar BLV for the same mesh size.

Microstructure and Mechanical Properties of Friction Stir Welded 1.5 GPa Martensitic High-Strength Steel Plates

Microstructure and Mechanical Properties of Friction Stir Welded 1.5 GPa Martensitic High-Strength Steel Plates

Numerical Analysis of the Structure of High-Strength Double-Layer Steel Plate Concrete Shaft by Drilling Method of Water-Bearing Weak Rock Formation

In order to ensure the safety of coal mine shaft construction, a double-layer steel plate concrete composite shaft wall structure was proposed. However, fewer studies were conducted on this structure, which made engineers too confused to fully recognize its feasibility of this structure. Hence, based on the previous experimental research on the Taohutu mine construction project in Ordos in Inner Mongolia, this research paper aims to provide a widely deep numerical analysis by the usage of the finite element software, in fact, to establish the corresponding numerical analysis model and make a comparison with the experimental data to get the rationality of the verified model. The influence of the composite characteristics of the steel plate and concrete on the ultimate bearing capacity and stress field of the shaft wall structure is studied here through the method of multi-factor analysis. Also, the optimal design scheme of the double-layer steel plate and concrete composite shaft wall structure is proposed in this research paper.

Numerical simulation of deformation and fracture processes during static and dynamic perforation of thin plates from high-strength materials

The paper presents the calculation technique for static and dynamic perforation of thin high-strength steel plates using different models of material deformation and fracture. The calculations have been performed employing the finite element (FE) method and Johnson-Cook material deformation model. The material parameters are specified for Armox 500T steel. The influence of the indenter shape, loading rate, and contact conditions on the material deformation and fracture is investigated. The distribution fields of strains and stresses at different time points are constructed. The variation in the indenter velocity during the perforation of the plates is determined, and the change in the strain rate of the fracture zone is estimated. The obtained results are used to develop the techniques for testing high-strength steels under static and dynamic perforation. The comparison of the results of experiments and calculations will help to specify the values of the material models’ parameters for modeling high-speed penetration processes.

Efforts Improving Forming Technology for Ultra-High-Strength Steel Sheets in the Western Part of Shizuoka Prefecture

The transportation equipment industry is flourishing in the western part of Shizuoka prefecture, and many manufacturers of automobile parts are concentrated. In recent years, due to the weight reduction and safety improvement of transportation equipment, high-strength and difficult-to-process high-strength steel plate stamped parts have been widely used in automobiles. Improving the molding technology is a major issue for the region. Here, "Hamamatsu UHSS Research Group," a collaborative group of industry, academia and government to improve the cold press manufacturing technology for high-strength steel sheets in the region is introduced.

Double shear tests of high-strength steel bolted connections with reduced tightening

This paper presents a study on shear resistance of high-strength steel bolted connections with reduced tightening. The double shear test was conducted with 108 specimens of high-strength steel bolted connections, including 96 steel bolted connections with different torque reduction percentages and 12 steel bolted connections under standard torque as a control group. The main variables of the test include the percentage reduction of tightening torque, steel bolt type, high-strength steel bolt grade and steel plate surface treatment. The effects of four parameters on the failure mode, strain distribution, slip resistance, shear capacity, initial stiffness and ductility of high-strength steel bolted connections under loading are studied. The test results indicate that the slip resistance and the shear capacity of the specimens are decreased with decreasing of tightening torque degraded rapidly. In the bolt loading stage, the stiffness of the steel bolted connections is decreased with the reduction of tightening torque, and decreasing rate of the stiffness is increased with the decrease of tightening torque. Nevertheless, the ductility of the steel bolted connections is increased with the reduction of the tightening torque. Among these effects of the four variables, the degree of reduction of the tightening torque has the greatest effect on the shear capacity of the specimen. The strength grade of high-strength steel bolts and the surface treatment method have the second effect on the shear capacity. In addition, the calculated formula of ultimate capacity was provided in this study. The calculated results were in good agreement with the test result. Furthermore, the finite element model was provided to simulate and analyze the shear behavior of high-strength steel bolted connection with reduced tightening.

Surface topography and stress concentration analysis for corroded high strength steel plate

In this paper, salt spray tests were firstly conducted for Q690 high strength steel plates. After the corrosion tests, the corrosion products were removed and the weight loss ratio was obtained. Then the topographies of the rough surfaces were scanned by a 3D surface profiler, and the 3D coordinates of the corroded surfaces were exported. Based on the data, the topographic feature parameters were determined, the uniform corrosion depth was calculated, and the extreme value analysis was conducted for the pitting corrosion depth to investigate its stochastic features. Finally, the corroded surfaces were restored and the finite element models of the scanned segments were established, which were validated by the experimental results and used to conduct the stress concentration analysis. The experimental results showed that the topographic feature parameters were linearly related to the weight loss ratio, and the maximum pitting depth conformed to the Frechat distribution. By conducting finite element analysis, it was concluded that under the uniaxial tensile load, the corroded steel plate showed an obvious stress concentration effect and most nodes were in a multiaxial stress state. In terms of the characteristic loads, both uniform and pitting corrosion induced the yield load and the ultimate load degradation. Regarding the uniform corrosion component, the loss percentage of the characteristic load was equal to the corresponding weight loss ratio. However, the loss percentages of the characteristic loads caused by pitting corrosion were smaller than the pitting weight loss ratio due to the stress concentration.

Experimental Investigation on the Shear Behaviour of Stud-Bolt Connectors of Steel-Concrete-Steel Fibre-Reinforced Recycled Aggregates Sandwich Panels.

Steel-concrete-steel (SCS) sandwich panels are manufactured with two thin high-strength steel plates and a moderately low-density and low-strength thick concrete core. In this study, 24 specimens were produced and tested. In these specimens, a new stud-bolt connector was used to regulate its shear behaviour in sandwich panels. The bolts’ diameter, concrete core’s thickness and bolts’ spacing were the parameters under analysis. Furthermore, the concrete core was manufactured with normal-strength concrete and steel fibres concrete (SFC). Steel fibres were added at 1% by volume. In addition, the recycled coarse aggregate was used at 100% in terms of mass instead of natural coarse aggregate. Therefore, the ultimate bearing capability and slip of the sandwich panels were recorded, and the failure mode and ductility index of the specimens were evaluated. A new formula was also established to determine the shear strength of SCS panels with this kind of connectors. According to this study, increasing the diameter of the stud-bolts or using SFC in sandwich panels improve their shear strength and ductility ratio.

Brittle Fracture Avoidance Technology in Large Structures with Thick Steel Plates.

The 460-MPa-class steel was developed by thermomechanical control process for shipbuilding, and the maximum plate thickness was 100 mm, which has the fine grain size as 5-20 µm. The surfaces were studied in terms of micro and nano structures, surface roughness, and surface energy to evaluate the effect of fracture toughness in large steel structure. The thick steel plate has possibility to occur unstable fracture because the fracture toughness will be decrease with increase of thickness. The increase in the temperature in thermomechanical control process accelerated the surface energy and created both micro and nano structures on the surfaces more effectively. It was effective to avoid brittle fracture in the base metal when the brittle crack was deviated into base metal. The developed 460-MPa-class steel plate improves the brittle fracture safety despite being a thick steel plate through the fine grain size. They had to be designed in such a manner as to avoid crack initiation, especially in welded joints. In this study, brittle crack arrest designs were developed for large weld construction using arrest design concept and micro and nano structures in high strength steel plate.

Effect of Combined Use of Brazing or Soldering around the Nugget on Tensile Shear Strength of Resistance Spot Welded Lap Joint

Resistance spot welding is used in the assembly of automobile bodies. The use of high tensile strength steel plates in automobile bodies is expanding, and there is a need to develop a welding process that improves the joint strength per resistance spot weld point. To improve the joint strength per resistance spot weld, resistance spot welding can be combined with other joining methods, such as the WeldBond method. As an additional joining method around the nugget, other than using adhesives as in the WeldBond method, brazing can be used to obtain a strong joint without melting the base metal. In this paper, it was proposed that the joint strength can be enhanced by using resistance spot welding and brazing or soldering based on the rule of mixture. And, based on this concept, effect of additional joint around a nugget, such as brazing or soldering, on rotational deformation of joint part and tensile shear strength of resistance spot welded lap joint was examined.

Application of Continuous Strength Method in high strength steel sections

AbstractHigh strength steel has been employed in modern steel‐framed building structures. It should be highlighted that these steel structures may be built‐up through fabrication of hot‐rolled steel sections or welded high strength steel plates. This study performed an extensive series of compression tests on high strength stub columns. These columns were made of Q620E steel plates through welded steel plates. The ultimate loads and displacements were extracted from the load‐displacement curves observed from the tests. The continuous strength method (CSM) was employed for analysis of the local buckling behavior of stub columns. In addition, a series of tensile strength tests were performed for standard steel coupons. A modified stress‐strain constitutive model was then proposed for design purpose for high strength steels. The predicted ultimate loads were compared with the recorded ultimate loads. It can be found that a reliable predication may be achieved in application of CSM in high strength steel sections.

Effects of laser and GMA hybrid welding parameters on shape, residual stress and deformation of HSLA steel welds

Abstract As a high-efficiency and high-quality welding process, hybrid laser-MAG welding (HLMW) has significant potential of application in welding thick plates. In the present study, based on thermal elastic–plastic theory, a three-dimensional finite element model is developed to predict the weld shape characteristics, residual stress and distortion in HLMW for a butt joint of 12-mm-thick high strength steel plate. Metal active gas arc welding (MAG) heat input and laser energy are modeled as one double-ellipsoid body heat source and one cone body heat source with enhanced peak density along the central axis, respectively. The comparison between calculated molten pool shapes and those obtained by the experiment shows a good agreement. Then weld shape characteristic, residual stresses and distortions are calculated in four different welding process parameters. The results show that the increase of laser power and current can effectively increase the weld penetration width when the welding speed is fixed. At the top surfaces of weldment, the peak stress of high laser beam power is more significant than that of low laser beam power. A high compressive transverse stress of low laser beam power can be found at the welding zone and the surrounding heat affected zone. However, at the bottom surfaces of weldment, the peak stress of low laser beam power is larger than that of high laser beam power. The peak stress of low laser beam power is much larger than that of high laser beam power. A high compressive transverse stress of low laser beam power can be found at the welding zone. The vertical deformation in low laser beam power and low arc current welding has the lowest value.

Influence of Local Properties on Fatigue Crack Growth of Laser Butt Welds in Thin Plates of High-Strength Low-Alloy Steel

In this work, local properties such as hardness and fatigue crack grow rate in the heat-affected zone of four laser-welded butt joints in thin high-strength low-alloy steel were examined, so as to explain and predict fatigue lives at high stress levels through the fracture mechanics approach. The different welded series presented a similar fatigue crack growth rate in the heat-affected and fusion zones, but lower than base metal due to the higher hardness of the bainitic–martensitic microstructure verified in the welded series. The results showed that at high stress levels in the as-welded condition, the fatigue initiation stage can be neglected and assume some types of cracks, with an initial crack of 0.07 mm and appropriate fatigue crack growth rates, estimates of fatigue life close to the experimental results were obtained.

Predicting the behavior of armored plates under shallow-buried landmine explosion using incomplete scaling models

Due to the influence of strain rate effect, distorted geometry and surface effect, the dynamic response of high strength steel plates under shallow-buried explosion will not follow the geometry similarity law. Therefore, the corrected relationship between strain-rate effect and specific impulse is derived by dimensional analysis. The exponential function presented by Oshiro and Alves is adopted to establish the corrected formula for the distorted thickness model, in which the surface effect is taken into account for alleviating the deviation caused by the manufacturing procedure. Based on the test data, which Rigby measured in the buried explosion, a set of revised empirical formulas for calculating the relationship between the specific impulse and the mass of explosives is determined. Moreover, by these models, one can predict the mid-point deflection of plates subjected to landmine explosion. Given all this, a rapid solution to predict the behavior of the prototype is presented in this paper. Three different shapes of plates subjected to landmine explosion are analyzed to validate this method. It is shown that the corrected incomplete scaling model can accurately predict the response of the prototype, which is helpful to design the incomplete scaled-down model test for mines resistant armored vehicles.

Local stability of normal and high strength steel plates at elevated temperatures

This paper presents an investigation into the local buckling behaviour and design of normal and high strength steel plates at elevated temperatures. The considered high strength steel grades include grades S690 and S460 as well as the normal strength grades S355, S275 and S235 taken into consideration. Shell finite element models of normal and high strength steel plates are created to mimic their local buckling response in fire, whose accuracy is validated against experimental results from the literature. Extensive numerical parametric studies are then carried out by means of the validated finite element models, taking into account different plate slendernesses, elevated temperature levels, edge boundary conditions and steel grades. The accuracy of the design provisions provided in the current European structural steel fire design standard EN 1993–1-2 and its upcoming version prEN 1993–1-2 for the consideration of the local buckling behaviour of normal and high strength steel plates in fire is investigated. It is observed that the existing design rules given in both EN 1993–1-2 and prEN 1993–1-2 lead to rather scattered estimations of the local buckling strengths of high strength steel plates at elevated temperatures. New cross-section classification rules and effective width design equations for the ultimate strength predictions of normal and high strength steel plates in fire are developed. High accuracy and reliability of the proposed design rules are demonstrated.

Effects of the Arctic low temperature on mechanical properties of Q690 and Q960 high-strength steels

Mechanical properties of high strength steel (HSS) are fundamental information to analyse and design HSS structures. This study extends the applications of HSS Q690 and Q960 to the Arctic infrastructures. The mechanical properties of HSS Q690/Q960 at the low temperature range of −80~20℃ were studied through performing standard tensile tests on 20 HSS Q690 coupons and 19 Q960 coupons in cooling chamber with LNG, which simulated the Arctic low-temperature environment. The influences of low-temperature levels, thickness of HSS plate, and HSS type on mechanical properties of HSS Q690/Q960 were in-depth investigated. The test results showed that the Arctic low temperature increased the modulus, yield and ultimate strength of HSS Q690/Q960, but did not reduced the ductility of these two types of HSS. In addition, all the tensile coupons of HSS failed in ductile mode without brittle fracture. This paper also developed constitutive models for HSS Q690/Q960 at low temperatures of −80~20℃. Validations showed that the developed constitutive models estimated reasonably well mechanical properties of HSS Q690/Q960 at low temperatures of −80~20℃.

Experimental investigation on fatigue behavior of butt-welded high-strength steel plates

This paper presents an experimental investigation into mechanical properties and fatigue performance of butt-welded high strength steel plates. Four typical high-strength steels (HSSs) were selected, with steel grades of 460, 550, 690, and 960 MPa. Mechanical properties were measured through monotonic tensile tests, cold bending tests, Charpy V-notch impact tests and hardness tests. A total of 114 fatigue tests were conducted on butt-welded high-strength steel plates. Comparisons of mechanical properties and fatigue performance are made among HSSs tested and conventional strength steels (CSSs) with a yield strength around 235 to 355 MPa. The natural slope of S–N curves for HSS butt-welded connections varied from 3 to 5. Two fatigue design approaches are recommended with one based on natural slope and one based on a fixed slope of 3 as for CSSs.

Properties and formation mechanism of cladding layer on high-strength low-alloy steel subjected to ultrasonic impact treatment with titanium alloy pin

The EQ70 high-strength low-alloy steel plate was treated using ultrasonic impact treatment (UIT) with titanium alloy (Ti6Al4V) pins. Scanning electron microscopy with energy dispersive X-ray microanalysis and X-ray photoelectron spectroscopy were employed to study the structure, morphology, surface chemical state, and composition of the treated product on the surface of the EQ70 steel. The microhardness was measured on the surface and the cross-section of the specimens. And the electrochemical corrosion test in the 3.5 wt% NaCl medium was carried out to evaluate the corrosion resistance of the UIT-treated specimens with different impact intensities and that without UIT. It is found that the UIT with Ti6Al4V pins can result in a mixed oxide cladding layer on the surface of the steel plate, the thickness of which increased with the impact intensity (treatment time). The elements in the cladding layer mainly come from the impact pin (Ti, Al, V), base metal (Fe), and the atmosphere (O), and the contents of these elements do not change significantly with the impact intensity. TiO, TiO2, FeO and Fe2O3 are found to be the main oxides in the cladding layer. The mutual effect of the material transfer between the pin and the treated base metal is found. The surface hardness of the cladding layer increases with the impact intensity, reaching an almost constant value (approximately twice the hardness of the parent material) when the impact intensity is over 1.33 s/mm2. The cladding layer can improve the corrosion-resistant properties of the EQ70 steel and get the best corrosion-resistant properties with an impact intensity ranging from 1.00 to 1.33 s/mm2. The possible formation procedure of the cladding layer after UIT with titanium alloy pins is suggested. The chip from the pin (material transfer from the pin) and the mechanochemical oxidation is the main cause to form the cladding layer.

Research on Finite Element Method of Hot Forming of High Strength Steel Sheet

The finite element simulation technology can provide strong support for the optimization of processing technology and the treatment of detailed problems in the processing process. Two finite element methods applied to hot forming of high-strength steel plates are introduced, namely the incremental method and the deformation method. Two methods are used for simulation calculations. The finite element simulation based on incremental theory has high accuracy and requires more complete mold and process information. It is mainly used in the middle and late stages of product and mold design. And the finite element simulation based on deformation theory have fast calculation speeds and are mainly used in the early stages of product and mold design. Both types of methods have high practical value.

The effect of kinematic hardening on the fatigue behaviour of bent high strength steel

The integration of forming in the fatigue modelling of cold-formed components significantly improves the predictive accuracy of the estimated life. The current study investigated the fatigue behaviour of a bent specimen made from a 5 mm thick, S900MC high strength steel plate. Because of its superior static and dynamic strength, this grade is progressively used for hollow cold-formed sections in mobile applications. However, it exhibits a strong stress saturation as well as limited formability. In this regard, a finite element modelling framework was adopted from previous research and further developed to integrate bending in the fatigue modelling and life estimation procedure. However, this framework currently ignores the possible influence of kinematic hardening and associated Bauschinger effect. For this reason, a numerical study was performed that compares isotropic with kinematic hardening for this specific application. First, the characteristic behaviour of these models was verified in a virtual tension-compression test. Subsequently, they were implemented in forming simulation followed by fatigue loading. Herein, the stress-strain evolution was investigated and a multi-axial fatigue criteria was used to map the sensitivity of the estimated life to the type of hardening. In general, the stress that entered the fatigue calculation was at least 21% lower for the kinematic model. As a result, a significant increase of 65% was observed for the estimated fatigue life, yielding a better comparison with experimental data.