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Given the increasing use of high-strength steels in building constructions, the stability design of high-strength steel beams has become a crucial consideration. However, the current standards of various countries are based on analyses and fittings derived from conventional steel, rendering them unsuitable for high-strength steel. Moreover, existing research indicates that these standards underestimate the ultimate load-bearing capacity of high-strength steel beams. A finite element model was established to investigate lateral torsional buckling in high-strength steel beams. The obtained results were then compared with test results from experiments conducted on Q460GJ and Q690 steel beams. The reliability and accuracy of the established finite element model were validated. Through parametric studies, the impact of depth-to-width ratio, boundary condition, and steel grade on the stability coefficient was evaluated. It was observed that at the same non-dimensional slenderness, an increase in the depth-to-width ratio or a reduction in support constraints led to a decrease in the stability coefficient. It should be noted that the steel grade had little effect on the stability coefficient. Comparisons with the current steel structure design codes, such as EN1993-1-1, GB50017-2017, JGJ/T483-2020, and ANSI/AISC360-22 revealed an underestimation of the stability coefficient for clamped high-strength steel beams under uniformly distributed loads. Based on finite element simulations, stability coefficients for high-strength Q460, Q690, and Q960 clamped beams were determined. Similar to the stability coefficient proposed in GB50017-2017 for the lateral buckling stability design of steel beams, a lateral buckling stability coefficient for high-strength steel clamped beams subjected to uniformly distributed loads was proposed.

In order to clarify the effects of nitriding and hybrid surface modification process combining nitriding and induction hardening on fatigue properties of SCM435H steel, high cycle fatigue tests were carried out with a rotational bending machine at room temperature. Observations of fracture surfaces and measurement of hardness and residual stress distributions were carried out to investigate the fracture mechanism. It was revealed that hybrid surface modification process generated a compressive residual stress field and hardened even at center of the specimen. Fatigue strength of hybrid surface modified specimens was much higher than that of substrate and nitrided specimens. This was because a transition of fracture mode from internal to surface fracture; fatigue fracture of nitrided specimens occurred at inside of the hardened layer, in the case of hybrid surface modified specimens, however, fatigue crack initiated at the surface of the specimen with higher hardness and higher compressive residual stress.

In this research, the effects of pre-fatigue on the dynamic and quasi-static tensile properties of laser welded butt joints between three kinds of steel plates, i.e. HR270, HR590 and HR780 steels, were investigated using tensile split Hopkinson bar apparatus. There were no significant effects of pre-fatigue on the dynamic and static tensile properties of HR780-HR270 and HR780-HR590 joints. Their fracture occurred in the middle of the weaker base metal parts. However, one or two in three pre-fatigued HR780-HR780 joint specimens broke at the heat affected zone, irrespective of strain rate. Their elongation decreased dramatically from that of the virgin specimens, although there are no changes in the tensile strength.

The tensile properties of YAG laser welded butt joints using different high strength steel sheets with a tensile strength of 270 MPa, 590 MPa and 980 MPa (denoted HR270, HR590 and HR980, respectively) were investigated at static and dynamic rates, together with the three kinds of laser welded joints made by the same steel sheets. The impact tensile tests were performed by using the vertical type of split Hopkinson tension bar apparatus, while the static tensile tests were carried out using a universal testing machine INSTRON5586. The impact tensile strengths were significantly increased in comparison with the static ones due to the effect of strain rate, which might be the contribution of the part of HR270 base metal. And in both of static and impact tests, the fracture strains of HR270-HR590 joint, HR270-HR980 joint and HR590-HR980 joint were about one half of the fracture strains observed in the same steel welded joints of HR270-HR270, HR270-HR270 and HR590-HR590, respectively.

Galling is a known failure mechanism in sheet metal forming (SMF), especially in the forming of high strength steels. It results in increased cost of die maintenance and scrap rate of products. In this study, U-channel forming tests were conducted to study the galling behavior under the condition of tension-bending. The effects of tool surface characteristics (hardness and surface roughness) and process parameters (blank holder force and sliding distance of the contact surfaces) on galling were investigated. Experimental results indicate that galling tendency can be reduced through hardening and polishing of the forming tool and galling becomes more severe with increasing blank holder force and sliding distance in SMF. A numerical model between the galling and these factors was established through non-linear curve fitting of the large amount of experimental data.

Thermal-assisted machining (TAM) is an effective processing solution to improve productivity and product quality made from materials with high strength and hardness. This method is widely used in nonchip machining such as forging, stamping, deep drawing, etc. For the method of heating on the molds, it is possible to control local heat or uniform heat on the workpiece. However, the calculation of heat capacity, heat transfer as well as the heating time to achieve the temperature on the workpiece is necessary to design suitable molds and heating system. This study focuses on a heating system that uses single-sided thermostatic heating rods to heat the molds, verify the effect of the heating time on the temperature of the workpieces and then control the temperature on the workpieces at various heat levels through a heating control system. Thereby, this study proposes to build a mathematical model between temperature and heating time on the workpiece.

A new method was introduced to research the corrosion resistance of enamel coatings which were sintered at different temperatures in this paper.^1–4 Scanning electrochemical microscopy (SECM) conjunction with capacitance-potential test and Mott–Schottky analysis technique were used to study the coating failure process and semiconductor conduction behavior of enamel coating in 3.5wt.% NaCl solution. The high strength steel (SAPH440) was selected as the metal substrate. The coatings which were sintered at different temperatures on the high strength steel were analyzed and their corrosion behaviors and microstructures were also measured by potentiodynamic polarization curves, Mott–Schottky analysis technique and scanning electrochemical microscopy.^5–10 In this paper, five kinds of enamel coatings were prepared on high strength steel. The SECM results show that the Faraday current of the microprobe tip gradually decreases with the soaking time increasing, which indicates that the coatings become failure slowly with the invasion of water and aggressive ions. At the same time, the tip current was homogeneous during the immersion process, which reflected that the surface of the sample remained stable, no obvious bulges appeared. Capacitance–potential test and Mott–Schottky analysis^7,8 show that the external ions and water molecules gradually penetrate into the coating; coating showed characteristics of $n$-type semiconductor as time increases, the capacitance increases gradually, the space charge layer thickness decreases, slope of Mott–Schottky curve decreased gradually which indicates that the failure of coating in the process of soaking slowly with the charge carrier density increases.

This paper investigates the combined effect of flexural and shear actions on the failure modes of the high strength reinforced concrete (HRC) members using the proposed algorithm for plastic hinge formation. The accuracy of the present procedure for the HRC columns was verified by comparing the results obtained with those of the cyclic loading tests performed in Japan. To evaluate the seismic performance of the HRC high-rise buildings, a seismic performance checklist for the HRC buildings was recommended. Based on the proposed algorithm for formation of plastic hinges, the seismic performance of HRC buildings based on the static pushover analysis is evaluated. From the results of the pushover analysis, a simplified lumped-mass stick model was developed, which is adopted to evaluate the seismic performance using the nonlinear time history analysis. For the purpose of illustration, the seismic performance of a high-rise building constructed with HRC was investigated by both the nonlinear pushover and nonlinear dynamic analyses using the proposed procedure and concepts. The results of this paper serve as a useful reference for the seismic design and evaluation of HRC high-rise structures.

In this study these advantages of the laser welding has been considered for Nd:YAG laser stitch welding(LSW) as a substitute for resistance spot welding(RSW) of lightweight car body plates. First, optimized parameters for Nd:YAG laser stitch welding for automotive high strength steel sheet(SRPC340) have been determined comparing the economical and mechanical characteristics to match with the currently used spot welding characteristics. Second, the mechanical phenomena of thermal elasto-plastic behavior on the Nd:YAG laser stitch welded joints has been clarified by two-dimensional thermal elasto-plastic analysis using F.E.M.

High strength steel has been increasingly used in auto body design to achieve lightweight and safety. Recently WISCO made great efforts in research and development of HSS, including new grades development, new forming technology research and application. DP780 as a typical UHSS had been widely applied in car body parts after deep investigation in all kinds of properties. Springback analysis and welding test had been carried out to have better understanding in different grades of HSS. Roll forming, as an efficient forming technology, had been successfully applied in processing WISCO's hot rolled high strength steel product used for bus body. Many Optimizing methods were researched and utilized to provide high quality roll formed parts to customers. In hot forming area, WISCO had been working on boron steel development, tool design, whole process technology, tailed blank design, and post-treatment for part surface for long time. A lot of novel research results showed that hot forming will be more and more important in lightweight and safety for the future vehicles.

To improve the automotive safety and achieve light weighting, high strength steel was used in automobile pillar. The numerical simulation by Dynaform was finished for hot stamping of automobile pillar with thickness of 1mm and material of high strength steel 22MnB5. The simulation results analyzed and predicted defects such as cracking, wrinkling in hot stamping of high strength steel. The research can be used to guide the optimization of stamping process and die design for the automotive pillar to obtain the qualified products.

Thermal contact resistance between sheet metal and die is the key fact of influencing parameters in thermal and physical properties of the heat transfer in hot stamping process. Based on the cooling curves of blank and flat die obtained by experiment, the inverse heat conduct problem is solved by using sequential function method (SFM) and the thermal contact resistance is calculated.

B pillar structure has a greater impact on the vehicle side collision performance. This paper studied on high strength steel and advanced hot stamping of B pillar impact on the vehicle side collision performance. First, the conduct of a vehicle side collision test model and simulation Benchmarking, in order to verify the correctness of the whole vehicle model; Then, Using advanced hot stamping alternative to conventional hot stamping program. The analysis results found that advanced hot stamping B pillar enhanced the vehicle side impact performance, while reducing the quality of vehicle. Advanced hot stamping technology can also be in A pillar, stringer, and other critical small assembly, in the case of collision performance, to achieve the purpose of automotive lightweight design. Advanced hot stamping has important significance to automotive lightweight design.

Threshold beam is a primary energy absorbing structure, and is also important part to minimize the occupant injury in side impact. This paper mainly introduced the material of high strength steel used on the Threshold beam's lightweight research. The correspondence between completed car test and component test is made from aspects of deformation, energy and force transmission. Then a component crash test for threshold beam is built, with which the crash performance of threshold beam system in completed car impact test can be evaluated. This model of threshold beam crash test can be used on lightweight research, after the optimization the weight of threshold beam system is reduced without risk of lowing crashworthiness performance, in order to promote the safety performance.

The response characteristics of high strength steel for automotive under high strain rates were comprehensively reviewed, the relationship of vehicle lightweight with improvement of vehicle safety and the application of high strength steel were discussed, and the demand of response characteristics of materials for crash safety simulation was proposed. The developments of highspeed tensile testing equipment, test methods, data processing and constitutive equations were further discussed, and finally presented the test results, response characteristics, the related constitutive equation and typical application of various types of automotive high strength steel under high strain rates. Perfection of tests for response characteristics of high-strength steel under high strain rates and deep understanding of its deformation mechanisms will contribute to the development and applications of high-strength steel.

Hot stamping of high strength steel (HSS) can significantly improve overall mechanical properties of part and thus meet the increasing demands for weight reduction and safety standards in vehicles. However, cracking prediction using traditional forming limit curve (FLC) in hot stamping is challenging. In this paper, to predict HSS cracking in hot stamping a temperature-dependent forming limit surface (FLS) is developed by simulations combined with experiments. Different from the FLC the newly developed FLS, where temperature and phase transformation are included, suits the hot stamping of HSS. A finite element (FE) thermo-mechanical coupled numerical model of the hot stamping process is developed and implemented under ABAQUS/Explicit platform. Finally the developed FLS is used to predict crack initiation in a hot stamping. Results show that effectiveness of the developed FLS is verified in cracking prediction for hot stamping of HSS.

Q&P hot stamping is a novel process to produce high strength steel parts with better elongation than the conventional ones. In this paper, recent studies of Q&P hot stamping process are presented. Firstly, the process of the Q&P hot stamping is discussed and a fractional cooling steps strategy is introduced to optimize the procedure. Secondly, several different materials are introduced to test the positive effects of Q&P process, and the suitability of these steels are also discussed. Thirdly, the formability of the hot stamping process is studied, as well as the springback phenomenon and its relationship with process parameters. Finally, microstructure evolution during the Q&P hot stamping process is modelled and discussed.

In this paper, the contents mainly include two aspects, one of which is the study of Q&P parameters effects, the main parameters are quenching temperature, partition temperature and partition time. Several groups experiments are carried on under different conditions, the results are determined by the tensile strength and elongation rate which are obtained by tensile test. The second is to carry out experiments on U shaped parts in the same conditions respectively with the traditional hot formingquenching process and Q&P process, comparing the effect of Q&P and traditional hot forming process on springback, the results of springback are evaluated by the rebound angle. Finally, by analyzing and summarizing the experimental results, finding that Q&P process has little influence on springback.

Hot stamping is increasingly used in automobile structure part for the demand of automotive safety and emission reduction. However, due to the non-uniform cooling path of the blank, the mechanical properties are not consistent. This paper expounds that the main reason of non-uniform cooling parts is the non-uniform contact pressure and clearance between parts and sheet metal. Base on the finite element analysis of cooling path during the forming and quenching process, an optimization method that improves contact condition between blank and die is developed by using modified mold block to improve contact condition between die and blank. The result shows that the blank obtains more uniform cooling path.

The effects of different process routes on fatigue properties of DP600 and FB540 two wheel steels are studied, including the raw material (R), pre drawing (RP), and baking (RPB). With standard tensile specimens as the experimental object, the tensile test and the tension-compression cyclic loading fatigue test have yielded basic parameters of materials, including the material’s stress-strain curve and strain life fatigue curve. Simple sample simulation results verify the quasi static analysis method with the feasibility study. After obtaining the basic parameters of the material, according to the basis of the wheel to change wheel shape, the fatigue life of the wheel and the new wheel of modified shape, the quasi-static analysis method for stress and strain on the wheel were undertaken using ANSYS software to study the strain fatigue analysis between the original and new modified wheel. Studying the influence of the bending fatigue life with an original wheel and a diverted wheel, analysis results showed the influence of different material technologies on the material of the original wheel and the diverted wheel. The influence had the same tendency: the wheel modification achieved the goal of losing wheel weight. Finally, experimental verification of the modified wheel, simulation and experimental results show that, simulation results and fatigue life test results were approximate. The crack that appeared in the wheel fatigue experiment had a consistent position with the fatigue life simulation minimum cycle times. The validity of the fatigue strain and fatigue life analysis is verified. This paper provides an effective way to study the influence of material technology on the properties of materials, and it has a certain practical value.