Steel Sheets Research Articles

The effect of pre-painting and W-temper forming on springback

AbstractThe present investigation examined the impact of thermal cycling applied during the painting of sheet steels and the transfer period in the forming of W-temper heat treatment of high-strength aluminum alloy on springback. The U-draw bending test was conducted numerically and experimentally to examine the springback parameters. Pre-painted steel might be aged due to surface cycling during painting and it changes the mechanical characteristics. As a result, pre-painted steel becomes more susceptible to springback. It is also observed that springback is mostly reliant on the amount of transfer time between the W-temper forming of aluminum alloy. To sum up, the interplay among material characteristics, processing techniques, and forming conditions leads to the springback phenomena.

Influence of welding-induced mechanical stress on the electromagnetic properties of magnetic lamination

Purpose This paper aims to analyze the influence of welding-induced mechanical stress of a magnetic core material on the performance behavior of a permanent magnet excited synchronous machine (PMSM). Welding, interlocking, clinching and the use of adhesives are state-of-the-art packaging technologies used in the manufacturing of electrical machines. However, the packaging processes degrade the electromagnetic properties of the electric steel sheets, thereby decreasing the performance and achievable range of the electric vehicle. Design/methodology/approach In this paper, an approach that maps the local changes in magnetic properties due to welding induced stress with the stress values is developed. The welding process induces internal stress inside the steel sheet due to the diffusion of thermal energy into the sheets. Other effects are the changes in the micro structures of the steel sheets (grain sizes). These induced mechanical stresses lead to significant deterioration of the electromagnetic properties. They also lead to an increase in iron loss attributed to steel lamination. Findings A low speed (city), a high-speed (highway) and WLTC-c3 driving cycle will be used to analyze the effects of the induced stresses on the machine efficiency at the different operating conditions. A high-speed PMSM with a maximum speed of 26,000 min−1 and maximum torque of 130 Nm is designed for this study. Originality/value The value of this study is in the development of a local varying modeling approach that analyses the influence of weld-induced stress on the performance of electrical machines. Its originality is evident in the mapping methodology. This will enable an application dependent improvement possibilities due to the understanding of the impact of weld-induced stress on the electromagnetic properties of weld-packaged core.

Combined Experimental and Numerical Modelling of the Electrical Behaviour of Laser-Soldered Steel Sheets.

The electric vehicle (EV) industry challenges battery joining technologies by requiring higher energy density both by mass and volume. Improving the energy density via new battery chemistry would be the holy grail but is seriously hindered and progresses slowly. In the meantime, alternative ways, such as implementing more efficient cell packaging by minimising the electrical resistance of joints, are of primary focus. In this paper, we discuss the challenges associated with the electrical characterisation of laser-soldered joints in general, and the minimisation of their resistive losses, in particular. In order to assess the impact of joint resistance on the overall resistance of the sample, the alteration in resistance was monitored as a function of voltage probe distance and modelled by finite element simulation. The experimental measurements showed two different regimes: one far from the joint area and another in its vicinity and within the joint cross-section. The presented results confirm the importance of the thickness of the filler material, the effective and total soldered area, and the area and position of the voids within the total soldered area in determining the electrical resistance of joints.

Vector magnetic circuit analysis of silicon steel sheet parameters under different frequencies for electrical machines

AbstractSilicon steel sheets (SSSs), serving as the principal constituent of the magnetic circuit in electric machines, necessitates precise modelling and accurate computation using magnetic circuit theory as a prerequisite for analysing the characteristics of electric machines. Nevertheless, the conventional magnetic circuit theory, limited to a single reluctance component, fails to address the phase relationship between magnetomotive force and magnetic flux, and inadequately represents the magnetic flux distribution observed under high‐frequency conditions. Consequently, the existing magnetic circuit model for SSSs remains imperfect in its current state. Fortuitously, the advent of magductance has effectively addressed these challenges. Building upon magductance, this study deduces the fundamental laws and theorem within the vector magnetic circuit theory. Subsequently, a distributed parameter vector magnetic circuit model for the SSSs is constructed, accompanied by the derivation of expressions pertaining to its reluctance and magductance. The authors propose the transfer function composed of reluctance and magductance parameters, successfully resolving the phase between the magnetic circuit vectors, the magnetic flux distribution, and the magnetic circuit loss under different frequencies for SSSs. Finally, experimental findings affirm the efficacy and validity of the distributed parameter vector magnetic circuit model for SSSs. The proposal of vector magnetic circuit theory opens a whole new door for the analysis, computation, and optimisation of electric machines.

An investigation on bending fatigue in a corrosive environment of dual-phase 1000 sheet steel RSW joints and damage model via experiment and numeric analysis

Fatigue, corrosion, and fatigue damage models are best addressed to improve and understand the service performance of materials, particularly automotive steel. This study is an attempt to experimentally and finite element investigates plain bending fatigue performance and damage model of DP 1000 sheet steel resistance spot welding (RSW) joints in 3% NaCl aqueous corrosive treatment. RSW applications were carried out using different weld currents. The joint samples were then subjected to optical image analysis, tensile shear, and fatigue tests (3% NaCl-aqueous and normal atmosphere). A proper damage model of RSW junctions was developed and corrected by numeric analysis. Besides, RSW nugget formation, tensile shear, and plain bending fatigue tests were also applied. Consequence, fatigue behavior, tensile load carrying capacity, and effective fracture behavior of resistance spot welded joint specimens were evaluated. Results showed that a corrosive environment negatively affected fatigue performance. With the developed model, it was observed that the fatigue life of the samples decreased by 30–35% in the fatigue tests performed in the corrosive environment. Experimental and numerical analysis results of plain bending were compatible.

DRAGen in Application-An Approach for Microstructural Fatigue Predictions of Non-Oriented Electrical Steel Sheets.

This study investigates multiple cyclic loading scenarios of non-oriented electrical steel sheets through both experimental and numerical approaches. The numerical simulations were conducted using Representative Volume Elements generated with DRAGen. DRAGen allowed for the generation of Representative Volume Elements with a non-cubic shape to cover the complete sheet thickness and enough grains to represent the material's texture. The experimental results, on the other hand, are utilized to calibrate and validate a prediction model, highlighting the significance of accumulated plastic slip as a suitable parameter correlated with fatigue life. Using the accumulated plastic slip from the simulations, a fatigue fracture locus is introduced, which describes a 3D surface dependent on the maximum stress, fatigue life, and the fatigue stress ratio. The study shows reliable results for the fatigue life prediction using the calibrated fatigue fracture locus. While substantial progress has been made in predicting the fatigue life at multiple fatigue stress ratios, notable disparities between experimental and simulation results suggest the need for further investigations regarding the influence of the surface quality. This observation motivates ongoing research efforts aimed at refining simulation methodologies to better incorporate surface roughness effects. In summary, this study presents a validated model for predicting fatigue life in non-oriented electrical steel sheets, offering valuable insights into material behavior at different loading scenarios and informing future research directions for enhanced structural performance and durability.

Strict convexity of yield surfaces of some weakly-textured materials

Let Sym0 be the space of traceless symmetric second-order tensors. We say that a polycrystalline elastic–plastic material is weakly-textured if its yield function f:Sym0→R is the sum of a texture-independent isotropic part fiso and an anisotropic part which is linear in the relevant texture coefficients. Let c>0 and S≔f−1(c)⊂Sym0 be the yield surface of the weakly-textured material in question. We present a sufficient condition (*), namely that ∇2f(S) be positive definite for each S∈S, for a smooth yield surface S to be strictly convex in Sym0. We apply this sufficient condition to weakly-textured materials with yield functions that satisfy the following conditions: (i) the yield functions f and fiso are smooth; (ii) ∇2fiso(S) is positive definite for each S in Siso≔fiso−1(c)⊂Sym0. We prove that the yield surface S⊂Sym0 of such weakly-textured material is strictly convex if the texture coefficients in f are sufficiently small. As illustration for practical applications, by appealing to condition (*) we study the strict convexity of the yield surface pertaining to a weakly-textured orthorhombic aggregate of cubic crystallites which has a quadratic yield function of the type proposed by Hill in 1948. Moreover, we show that all 35 samples of cold-rolled and annealed low-carbon steel sheets studied by Stickels and Mould have their quadratic yield functions and corresponding yield surfaces strictly convex.

Behavior of stressed skin corrugated sheet under hydrostatic loads

Water storage in buildings is an integral part of water supply, which can be used for firefighting and drinking. It can be divided into three categories: elevated, rooftop, and underground water tanks. This paper presents a novel water storage system consisting of thin-walled corrugated steel sheets, which can be installed in a multi-story building on any floor. Compared with a reinforced concrete tank, the integrated steel water tank can be fabricated and installed much faster and store freshwater more easily. To develop the system, a finite element model is developed, which is validated using the on-site measurements. Next, the model is used to conduct a parametric study to evaluate the effects of boundary conditions, panel depth, sheet thickness, trough-to-crest width ratio, and corrugation angle on the behavior of integrated steel water tanks. The model is further used to evaluate the water tank subjected to lateral diaphragm loads and report the tank stiffness under combined loads. Finally, an implementation guide for the steel tank is presented, showing the supporting system, vacuum and magnetic handling of steel panels, robotic welding techniques, and delivery. It can be concluded that the paneled steel tank can be an efficient solution for water storage inside buildings.

Effect of multiple laser peening on the wear resistance of 304 stainless steel

PurposeThe purpose of this paper is to investigate the effect of laser peening (LP) on mechanical and wear properties of 304 stainless steel sheet.Design/methodology/approachThree-dimensional morphology, micro-hardness and micro-structure of shocked samples were tested. The wear amount, wear track morphology and wear mechanism were also characterized under dry sliding wear using Al2O3 ceramics ball.FindingsThe LP treatment generates deformation twins that contribute to the grain refinement and hardness increase. The wear test displays that the wear mechanism of samples is mainly abrasive wear and oxidation wear at 10 N load. While at 30 N, the delamination and adhesion areas of treated sample are reduced visibly compared to untreated ones.Originality/valueThis study specifically investigates the mechanical and wear properties of 304 stainless steel after the direct action of LP on its surface, which shows an effective improvement on the wear resistance. For example, the wear loss of processed sample is reduced by 19% at 30 N, the friction coefficient decreases from 0.4714 to 0.4308 and the groove depth is reduced from 78.1 to 74.4 µm under same condition.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2024-0007/

Multi-objective optimization of rivet and die for self-piercing riveting using finite element analysis

This study numerically investigated the effects of self-piercing riveting (SPR) process parameters on the quality of joints between steel and aluminum alloy sheets. First, the mechanical properties of each metal were experimentally evaluated, and a single-lap shear test was performed to validate a constructed finite element analysis model. This model was subsequently applied to optimize the die depth, die radius, and rivet length parameters of the SPR process using a multi-objective optimization method considering the shear strength, interlocking distance, and minimum thickness of the bottom sheet as objective functions. The results indicated that the maximum interlock distance was achieved with a longer die depth and larger die radius, and the largest minimum thickness of the bottom sheet was achieved with a shorter rivet length and larger die depth and radius. The die radius and depth were determined to be the most critical variables for all objective functions. The findings of this study can be applied to optimize the SPR of steel and aluminum alloy sheets.

A Calculation Method for Static Hysteresis Loop and its Applications

Background: Due to experimental equipment limitations, it is usually difficult to measure the quasi-static hysteresis loop at extremely low frequencies, which inevitably introduces errors in the static hysteresis model. Objective: This study aims to propose a method for calculating the static hysteresis loops of grainoriented silicon steel sheets so as to improve the accuracy of the static and dynamic hysteresis model. Methods: The parameters n0 and V0 in the magnetic field strength expression of the excess loss are determined by the measured losses within the range of 0-100Hz. Subsequently, the dynamic components in the quasi-static hysteresis loops are eliminated. Furthermore, a dynamic hysteresis model is established based on the loss and field separation theory, which incorporates the inverse Preisach model. Results: The dynamic hysteresis loops of the grain-oriented silicon steel sheets are measured in the range of 8-250Hz and compared with the results of both the improved model and the original model. Conclusion: Experimental results demonstrate the effectiveness and accuracy of the improved model. The proposed method for calculating static hysteresis loops has universal applicability and is meaningful for accurate simulation and prediction of magnetic properties in soft magnetic materials.

Optimised design of aviation stainless steel sheet SH guided wave focusing PPM EMAT

ABSTRACT Electromagnetic Acoustic Transducer (EMAT) is an ultrasonic testing technique that generates sound in the part inspected instead of the transducer. Electromagnetic ultrasonic guided wave detection technology has problems such as low energy conversion efficiency and the great influence of environmental noise, resulting in low echo signal amplitude. When the two rows of permanent magnets are arranged non-parallel, the sound beam will be focused at the intersection point of the axes of the two rows of permanent magnets. This article uses this rule to optimise the design parameters of PPM EMAT. Distance amplitude curve (DAC) is a method of compensating. However, large-scale detection requires a flat DAC curve. In addition, the increase in the angle and length of the permanent magnets and the number of pairs of permanent magnets will improve the intensity of the defect wave indication intensity. However, the increase in the angle of the permanent magnets will increase the signal attenuation. After simulation and experiments, when the angle, length and number of permanent magnet pairs are 4°, 25 mm and 8 pairs, the corresponding EMAT has the optimal axis radiation sound field and a smoother DAC, which is more suitable for stainless steel sheets, long-distance rapid guided wave detection.

Inverse Scheme to Locally Determine Nonlinear Magnetic Material Properties: Numerical Case Study

We are interested in the determination of the local nonlinear magnetic material behaviour in electrical steel sheets due to cutting and punching effects. For this purpose, the inverse problem has to be solved, where the objective function, which penalises the difference between the measured and the simulated magnetic flux density, has to be minimised under a constraint defined according to the corresponding partial differential equation model. We use the adjoint method to efficiently obtain the gradients of the objective function with respect to the material parameters. The optimisation algorithm is low-memory Broyden–Fletcher–Goldfarb–Shanno (BFGS), the forward and adjoint formulations are solved using the finite element (FE) method and the ill-posedness is handled via Tikhonov regularisation, in combination with the discrepancy principle. Realistic numerical case studies show promising results.

Experimental investigation of photoelectrical performance and thermal characteristics of ventilated building-integrated photovoltaic system utilizing lightweight and flexible crystalline silicon module

The existing large-scale of industrial buildings with lightweight insulated roofing structures presents a challenge for traditional glass crystalline silicon photovoltaic (PV) systems due to insufficient load-bearing capacity. Meanwhile, traditional PV rooftop applications also face challenges due to limited rooftop resources. To address these issues, this study proposes a ventilated building-integrated lightweight photovoltaic (VL-BIPV) system. The VL-BIPV system incorporates lightweight and flexible crystalline silicon modules, which increase rooftop load by about 6 kg/m2. Additionally, the system features a ventilation channel design to enhance thermal management performance. To evaluate the PV performance and thermal characteristics of the proposed system, an experimental setup was implemented to compare the performances of the VL-BIPV system with a building-attached lightweight photovoltaic (L-BAPV) system that utilizes color steel sheet base plates. The results demonstrate the exceptional performance of VL-BIPV system, with a 100.56% higher ratio of the product of short-circuit current and open-circuit voltage compared to L-BAPV. Moreover, the VL-BIPV system achieved a 1.77% increase in PV efficiency and a 2.35% enhancement in daily electricity generation. In hot weather, the adoption of VL-BIPV reduced the extreme temperature of PV cells by 9.23 °C below 85 °C, surpassing the 6.29 °C reduction achieved by L-BAPV system. Furthermore, the ventilation channel exhibited a gradual temperature increase with slower changes in the flow direction, while the base plate temperature decreased by 13.41 °C, which indicates that VL-BIPV can effectively reduce solar heat gain in the building envelope and improve the indoor thermal environment. The research findings provide important guidance for promoting and applying VL-BIPV technology in large-scale industrial buildings with low rooftop load-bearing capacity, thereby promoting the production and utilization of clean electricity in industrial parks.

Fortifying Slab Resilience against Touch-Off Explosions: Integration of Innovative Stud Reinforcements and Computational Analysis

Explosions, once limited to military and accidental contexts, now occur frequently due to advances in warfare, local disputes, and global conflicts. Recent incidents, like urban bombings, emphasize the urgent need for infrastructure to withstand explosions. Slabs, critical in architectural frameworks, are vulnerable to explosive forces due to their slimness, making them prime targets for sabotage. Scholars have explored various strategies to fortify slabs, including the use of advanced materials like CFRP laminates/strips, steel sheets and ultra-high-strength concrete, along with reinforcement techniques such as two-mesh and diagonal reinforcements. A novel approach introduced in current research involves integrating vertical short bars, or studs, to enhance slab resilience against touch-off explosions. The aim of this research endeavor is to assess the impact of studs and their utilization in bolstering the anti-contact-blast capabilities of a concrete slab. To achieve this goal, a specialized framework within the ABAQUS/Explicit 2020 software is employed for comprehensive analysis. Initially, a conventionally reinforced slab devoid of studs serves as the benchmark model for numerical validation, facilitating a comparative assessment of its anti-contact-blast effectiveness against the findings outlined by Zhao and colleagues in 2019. Following successful validation, six additional distinct slab models are formulated utilizing sophisticated software, incorporating studs of varying heights, namely, 15 mm and 10 mm. Each configuration encompasses three distinct welding scenarios: (i) integration with upper-layer bars, (ii) attachment to bottom-layer bars, and (iii) connection to both upper- and bottom-layer bars. The comparative merits of the slabs are evaluated and deliberated upon through the examination of diverse response parameters. The research revealed that the incorporation of studs within slabs yielded notable enhancements in blast resistance. Specifically, taller studs demonstrated exceptional resilience against deformation, cracking, and perforation, while also diminishing plastic damage energy. Particularly noteworthy was the superior performance observed in slabs with studs welded to both upper and lower layers of re-bars. This highlights the critical significance of both the integration of studs and their precise positioning in fortifying structural integrity against blast-induced loadings.

Investigation of the Compound Strength of Hybrid Casting Components with Different Variations of Coated and Undercut Sheet Metal

AbstractLightweight design can reduce CO2 emissions and improve energy efficiency, especially in the fuel-intensive transportation sector. Multi-material design approaches can combine specific properties of materials for effective lightweight design. A multi-material component made from two metals used widely in industry could combine the exceptionally lightweight properties of aluminum with the strength and structural integrity of steel. However, joining aluminum and steel is a challenge due to their different thermo-physical properties and the possible formation of brittle intermetallic phases. In hybrid casting, aluminum is cast around a steel sheet insert in a high-pressure die casting process to produce complex parts. In a first approach, a cold gas sprayed aluminum coating on the insert was tested as a bonding agent between the steel substrate and the molten aluminum. The joint was achieved by a combination of metallurgical bonding and micro-clamping. As a second option, surface structures with undercuts were applied to the steel sheet by modified cold rolling, which allowed the molten aluminum to flow into the channels and interlock with the solid steel. Different orientations of the structure on the insert were tested. In addition, the combination of both approaches was used to potentially enhance the positive effect of the pretreatment techniques. Given the critical importance of joint strength, the quality of these approaches was tested by static tensile tests and dynamic fatigue tests. The results show that the joint by coatings is strongly influenced by the process temperature. The improvement of the joint by the surface structure depends on its orientation to the melt flow.

Effects of steel bolts on retrofitting the buckling performance of storage rack system uprights

Storage rack systems, essential for product storage, encounter design challenges, particularly for uprights under axial loading. Despite being produced from thin-walled steel sheets, these systems are required to support excessive loads. Extensive research has focused on maximizing the load-bearing capacity of rack uprights in recent years. This study aims to enhance the axial load capacity of upright profiles through a retrofitting method of installing steel bolts and spacers. Experimental, numerical, and analytical evaluations were conducted to assess the effectiveness of bolt installation in enhancing axial strength of the uprights. Bolt installation altered buckling modes, suppressing distortional buckling. Results consistently showed an increase in axial load capacity with bolt installation, particularly notable in taller uprights. Comparison of experimental, numerical, and analytical results revealed good alignment, highlighting the positive impact of bolt installation on structural stability. Numerical analysis slightly underestimated experimental outcomes, especially for longer lengths, while the analytical approach showed a combination of overestimation and underestimation, with significant overestimation for longer lengths. The study concludes that bolt installation effectively increases the axial load capacity, especially for taller uprights. These findings offer remarkable insights on the positive effect of bolt installation for optimizing storage rack systems by enhancing structural stability and eliminating distortional buckling.

Study on magnetostrictive properties of oriented silicon steel sheet under different working conditions

Accurate measurement of magnetostriction is the basis for calculating the vibration of silicon steel laminated core. In this paper, a laser magnetostriction measurement system (MST500) is used to study the magnetostriction characteristics of silicon steel under sinusoidal, third harmonic, and DC bias magnetization. The magnetostrictive butterfly curves, time domain waveforms, and spectrum diagrams of silicon steel sheets under different excitations are compared and analyzed. The effects of different operating conditions on the magnetostrictive properties of silicon steel sheets were studied and analyzed, mainly including amplitude and spectrum analysis. Finally, the magnetostrictive peak to peak curves under different operating conditions were extracted, providing a data basis for the core vibration of power equipment.

Novel approach for sheet metal constitutive parameters identification based on shape index and multiple regression

To accurately predict the behavior and mechanical damage of sheet metal during hot forming process, the use of advanced thermomechanical modeling and precise identification of the constitutive parameter are required. This paper proposes a novel identification approach for constitutive parameters that relies on multiple regression and the shape index of experimental data curves. This approach is used to determine the material constants associated with the Johnson-Cook material and failure models for steel and aluminum sheets. Therefore, the obtained results approve the applicability and high accuracy of the identification procedure for the damage and the constitutive parameters of sheet metal, which allows for substantial time savings. Furthermore, to evaluate the formability of sheet metal, experimental forming tests at various temperatures were conducted. The identification process enhances the prediction of forming results, as shown by the fact that the numerical simulation of Erichsen and square die hydroforming tests using identified Johnson-Cook parameters agreed with the results of these tests carried out at different forming conditions. Moreover, the thickness measurement shows the ability of the developed model to properly predict the thickness of deformed shapes.

Fatigue Properties of Zinc Coated Low Carbon Steel Sheet Joints by the Means of Spot Welding

Fatigue Properties of Zinc Coated Low Carbon Steel Sheet Joints by the Means of Spot Welding