Search Results (356)

Curved plate forming is essential in shipbuilding but traditionally relies on manual methods with low efficiency. Achieving automation in curved plate forming requires robust methods to generate processing solutions. This paper introduces a novel method for deriving the processing routes and strain distributions necessary to form complex curve plate using integrated heating and mechanical rolling forming equipment. The key aspects of this method include analyzing the target surface and solving for the required processing strains based on finite element analysis, discretizing the strain paths and refining them into engineering-feasible processing routes, deriving processing schemes from the calculated strains, and predicting and validating the processing schemes using the inherent strain method. The method is validated by applying it to typical surface of ship hull plates. Key outcomes demonstrate the method’s effectiveness and applicability: (1) The proposed method effectively establishes a quantitative relationship between the target surface geometry, processing routes, and the required processing strains. (2) By analyzing various target surface cases, the method demonstrates wide applicability. Standardized procedures can be applied to different surface shapes to derive the necessary processing routes and strains, thereby laying a solid foundation for the automation of curved hull plate forming. (3) Experimental forming tests on typical curved surfaces confirm that the processing schemes based on the proposed strain generation method can reliably achieve the desired geometries, showcasing the method’s capability to guide practical forming processes. The comparison between the formed and target shapes shows that the processing deviation of the schemes generated by this method remains within 5 mm, demonstrating high accuracy. Full article

In the industrial practice of metal forming, the consistent and reasonable characterization of the material behavior under the coupling effect of strain, strain rate, and temperature on the material flow stress is very important for the design and optimization of process parameters. The purpose of this work was to establish an appropriate constitutive model to characterize the rheological behavior of a hot-formed steel plate (22MnB5 steel) produced through the TSCR (Thin Slab Casting and Rolling) process under practical deformation temperatures (150–250 °C) and strain rates (0.001–3000 s⁻¹). Subsequently, the material flow behavior was modeled and predicted using the Johnson–Cook flow stress constitutive model. In this study, uniaxial tensile tests were conducted on 22MnB5 steel at room temperature under varying strain rates, along with elevated-temperature tensile tests at different strain rates, to obtain the engineering stress–strain curves and analyze the mechanical properties under various conditions. The results show that during room-temperature tensile testing within the strain rate range of 10⁻³ to 300 s⁻¹, the 22MnB5 steel exhibited overall yield strength and tensile strength of approximately 1500 MPa, and uniform elongation and fracture elongation of about 7% and 12%, respectively. When the strain rate reached 1000–3000 s⁻¹, the yield strength and tensile strength were approximately 2000 MPa, while the uniform elongation and fracture elongation were about 6% and 10%, respectively. Based on the experimental results, a modified Johnson–Cook constitutive model was developed and calibrated. Compared with the original model, the modified Johnson–Cook model exhibited a higher coefficient of determination (R²), indicating improved fitting accuracy. In addition, to predict the material’s damage behavior, three distinct specimen geometries were designed for quasi-static strain rate uniaxial tensile testing at ambient temperature. The Johnson–Cook failure criterion was implemented, with its constitutive parameters calibrated through integrated finite element analysis to establish the damage model. The determined damage parameters from this investigation can be effectively implemented in metal forming simulations, providing valuable predictive capabilities regarding workpiece material performance. Full article

To ensure the product quality of a steel slab continuous casting machine, the mechanical alignment of the guide rolls must be monitored and corrected regularly. Misaligned guide rolls cause stress and strain in the partially solidified steel strand, leading to internal cracks and other quality issues. Current methods of alignment measurement are either not suited for regular maintenance or provide only indirect alignment information in the form of angle measurements. This paper presents three new algorithms that convert the available angle measurements into the absolute position of each guide roll, which is equivalent to the mechanical alignment. The algorithms are based on geometry and trigonometry or the gradient descent optimization algorithm. Under near ideal conditions, all algorithms yield very accurate position results. However, when tested and evaluated under various conditions, their susceptibility to real-world disturbances is revealed. Here, only the optimization-based algorithm reaches the desired accuracy. Under the influence of randomly distributed angle measurement errors with an amplitude of 0.01°, it is able to determine 90% of roll positions within $0.1$ mm of their actual position. Full article

Plastic forming in magnesium alloy sheet products is becoming a hot topic because of its potential in light-weight structural designs. Due to the special anisotropic and tension–compression asymmetrical properties of magnesium alloys, traditional modeling methods based on the von Mises yield criterion and using only uniaxial tensile properties for bending-dominated process simulations are not able to produce accurate predictions. In this study, two kinds of tensile tests (uniaxial and biaxial) and some compressive tests were performed along three material directions to obtain anisotropic and asymmetric properties, based on which the parameters of the Hill48 and Verma yield criteria were obtained. Then, the user subroutine VUMAT was developed, and the roll-forming process for magnesium alloys was simulated with the established anisotropic and asymmetric yield criteria. Finally, a roll-forming experiment on AZ31 magnesium alloy was performed. Compared with the experiments, it was found that roll-forming and springback predictions based on the Verma yield criterion had higher accuracy than those based on the von Mises and Hill48 yield criteria FEM models, which ignore anisotropy and asymmetry. This study provides an important FEM modeling idea that considers not only anisotropy but also asymmetry in the bending-dominated forming processes of magnesium alloys in which tension and compression exist simultaneously. Full article

To achieve the forward movement of the aircraft landing attitude ultra-limit, this paper builds a deep learning-based aircraft landing attitude warning system. The early warning system includes four modules: data pretreatment, feature dimensionality reduction, prediction, and judgment. Subsequently, through data pretreatment methods such as data cleaning, frequency normalization, data standardization, and feature classification, the experimental dataset is transformed into a form recognizable by machine learning algorithms and neural network models. The necessary feature parameters are extracted to form a deep learning training dataset. Then, the Max-Relevance and Min-Redundancy algorithm was applied to screen the QAR (Quick Access Recorder) parameters with the highest correlation with the predictor variables, and the LSTM network model was established to predict the pitch and roll angles of the aircraft landing, respectively. Evaluation metrics are used to determine the optimal model parameters. Finally, the confusion matrix is introduced to test the prediction effect of the model, and through the secondary indicators of the confusion matrix, the prediction accuracy of the established landing attitude warning system is 94.83% for the pitch angle and 91.18% for the roll angle. It also provides pilots with a 5 s time margin to avoid risks. The system can effectively issue early warnings for ultra-limit landing attitude events and, based on the prediction results, identify the types of risks. Full article

The CASTRIP process is an innovative method for producing flat rolled low-carbon and low-alloy steel at very thin thicknesses. By casting steel close to its final dimensions, enormous savings in time and energy can be realized. In this paper, an ultra-high-strength low-alloy corrosion-resistant steel was produced through the CASTRIP process. Microstructure and properties were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), laser confocal microscopy (LSCM), electron backscattered diffraction (EBSD), and tensile testing. The results show that the microstructure is mainly composed of polygonal ferrite, bainite ferrite, and acicular ferrite. The bainite ferrite forms parallel lath bundles nucleating at austenite grain boundaries, propagating perpendicularly into the parent grains. The acicular ferrite exhibits a cross-interlocked morphology preferentially nucleating at oxide/sulfide inclusions. Microstructural characterization confirms that the phase transformation of acicular ferrite and bainite ferrite introduces high-density dislocations, identified as the primary strengthening mechanism. Under the CASTRIP process, corrosion-resistant elements such as Cu, P, Sb, and Nb are completely dissolved in the matrix without grain boundary segregation, thereby contributing to solid solution strengthening. Full article

Fishing boats anchored away from the wharf or revetment are typically in side-by-side configurations due to their small size. Expanding on previous physical model tests investigating regular wave interactions with multi-boat and bow-and-stern-anchored fishing arrays, this study examines the hydrodynamic effects of irregular wave conditions. The Hilbert–Huang transform (HHT), an adaptive time–frequency processing technique, was applied to investigate multi-order nonlinear oscillatory elements in dynamic systems. It is found that the roll and heave motions of each boat are dominated by the wave-frequency components, whereas the sway motion is dominated by the low-frequency components. When multi-boats are anchored side by side, the roll and heave motion of the lee-side boat has a greater wave-frequency response compared with other boats, while for sway motion, the middle boat seems a little higher than others. The nonlinear dynamics of the roll and sway motion for a single boat is very large. An increase in the number of parallel boats has significant effect on reducing these responses. The variation trends of the three motion responses of the boat on the weather and lee sides are obviously different in each form. Full article

This study proposes a novel octagonal starfish-inspired roller imprinting control for multi-space and multi-axial microstructure replication, featuring a roller printing system with a controllable mold structure for multi-space and multi-axis applications. First, a microstructure was made and a micro mold was replicated to develop and simulate a negative Poisson ratio structure as a special structure to control the polymer microstructure mold. Meanwhile, a spatial axial roller imprinting system was designed as a roller imprinting replication system for the replication and roller imprinting of microstructures to research and conduct a roller imprinting testing experiment. The experiment results showed that the multi-space and multi-axial roll imprinting processing system with a controllable mold in this research had high replication formability. The results proved that the high replication formability of the microstructure obtained through white light scanning after subsequent roller imprinting was up to 98.75%. The diameter of the microstructure reached 99.025%, and the development of this innovative system and method of new technology could obtain the expected replication formability of the microstructure. Meanwhile, good achievements were obtained through optical preliminary validation. The results of this research could provide a reference about continuous microstructure component roll forming processing for academic and technological development. Full article

Considering the greater contact stress of turnout rails during wear and the development of heavy-haul railways, twin-disc sliding–rolling wear tests were performed on U75VH heat-treated rail steels applied for turnouts under high contact stress ranging from 1980 MPa to 2270 MPa. The microstructure of the worn surfaces was analyzed using optical microscope (OM), scanning electron microscope (SEM), 3D microscope, electron backscatter diffraction (EBSD), and hardness tests. The results indicated that after 10 h of wear, the weight loss was 63 mg at a contact stress of 1980 MPa, while it reached 95 mg at a contact stress of 2270 MPa. At a given contact stress, the wear rate increased with increasing wear time, while a nearly linear increase in wear rate was observed with increasing contact stress. As wear time and contact stress increased, the worn surface showed more pronounced wear morphology, leading to greater surface roughness. Crack length significantly increased with wear time, and higher contact stress facilitated crack propagation, resulting in longer, deeper cracks. After 10 h of wear under a contact stress of 2270 MPa, large-scale cracks with a maximum length of 128.29 μm and a maximum depth of 31.10 μm were formed, indicating severe fatigue wear. Additionally, the thickness of the plastic deformation layer increased with the wear time and contact stress. The surface hardness was dependent on the thickness of this layer. After 10 h of wear under the minimum and maximum contact stresses, hardening rates of 0.39 and 0.48 were achieved, respectively. Full article

Modern requirements for aluminum alloys used in mechanical engineering and aviation include increased strength characteristics and refined microstructure. One of the promising methods for improving the properties of aluminum alloys is rolling on a three-high skew rolling mill, which provides intense plastic deformation and a fine-grained structure. This study describes the results of numerical modeling of the rolling process of aluminum alloy 6082 rods in a three-high skew-type mill. Numerical modeling of alloy 6082 was conducted using the ForgeNxT 2.1 software designed to simulate metal-forming processes, including rolling. The rheological behavior of the material under study was investigated by compression tests using a Gleeble 3800 plastometer (“DSI”, Austin, TX, USA), which enabled the determination of the main parameters of material flow under specified conditions. The process of rolling bars of alloy 6082 on a three-high skew mill was numerically analyzed in the temperature range of 350–400 °C. This allowed for the study of the distribution of stresses, temperatures, and strain rates from the rolling mode. A physical experiment was conducted to validate the results of numerical modeling. The obtained results enabled the identification of rolling modes that promote microstructure refinement and enhance the mechanical properties of the alloy. Full article

Ti₂AlNb-based alloys are widely used in aerospace applications due to their excellent high-temperature mechanical properties. This study aims to investigate the texture, microstructural evolution, and phase transformation behavior of Ti₂AlNb-based alloy sheets during heat treatment and their effects on tensile properties. During heat treatment, B2 → O phase transformation occurs at 550 °C and 650 °C, while Ostwald ripening takes place at 700 °C and 850 °C. The α₂ phase undergoes spheroidization around 1000 °C due to grain boundary separation and recrystallization. Additionally, the B2, O, and α₂ phases all exhibit strong textures. The B2-phase texture follows a cubic orientation ({100}<001>), rotated ~30° around the normal direction (ND). The O-phase texture consists of a strong {100}<010> rolling texture and a weaker texture component <001>//RD, influenced by the B2-phase texture, rolling deformation, and variant selection during O-phase precipitation. Each B2 grain generates four variants, forming distinct O-phase textures within the same grain. The α₂-phase texture exhibits typical rolling textures, [0001]//TD, <$\overline{1}$2$\overline{1}$0>//ND, and {11$\overline{2}$0}<01$\overline{1}$0>, remaining stable after heat treatment. Tensile tests show that the rolled sheet has better ductility along the rolling direction (RD), while the transverse direction (TD) demonstrates higher yield strength (up to 1136 MPa). The anisotropy in tensile properties is mainly attributed to the O-phase texture, with minor contributions from the α₂-phase and B2-phase textures. These findings provide a theoretical basis for optimizing the mechanical properties of Ti₂AlNb-based alloys. Full article

To address the technical challenge of high polymer gel viscosity reducers losing viscosity at elevated temperatures and difficulty in controlling fluid loss, a polymer-based nano calcium carbonate composite high-temperature tackifier named GW-VIS was prepared using acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), N-vinylpyrrolidone (NVP), and nano calcium carbonate as raw materials through water suspension polymerization. This polymer gel can absorb water well at room temperature and has a small solubility. After a long period of high-temperature treatment, most of it can dissolve in water, increasing the viscosity of the suspension. The structure of the samples was characterized by infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy, and their performance was evaluated. Rheological tests indicated that the 0.5% water suspension had a consistency coefficient (k = 761) significantly higher than the requirement for clay-free drilling fluids (k > 200). In thermal resistance experiments, the material maintained stable viscosity at 180 °C (reduction rate of 0%), and only decreased by 14.8% at 200 °C. Salt tolerance tests found that the viscosity reduction after hot rolling at 200 °C was only 17.31% when the NaCl concentration reached saturation. Field trials in three wells in the Liaohe oilfield verified that the clay-free drilling fluid supported formation operations successfully. The study shows that the polymer gel has the potential to maintain rheological stability at high temperatures by forming a network structure through polymer chain adsorption and entanglement, with a maximum temperature resistance of up to 200 °C, providing an efficient drilling fluid for deep oil and gas well development. It is feasible to select nano calcium carbonate to participate in the research of high-temperature resistant polymer materials. Meanwhile, the combined effect of monomers with large steric hindrance and inorganic materials can enhance the product’s temperature resistance and resistance to NaCl pollution. Full article

Heavy rolling contact fatigue (RCF) may be caused by wheel surface defects under the influence of rail corrosion, which threatens the operational safety of rail vehicles. To investigate the role of surface defects on wheel RCF damage under the influence of rail corrosion, a salt spray tester was used to corrode the rails, an impact testing machine was employed to create surface defects, and RCF tests were completed. The role of surface defects on wheel RCF damage was studied by monitoring the wheel defect surface and cross-section. The results indicate that the tendencies of the RCF crack extension of surface defects of different sizes are similar, and they all extend in a C-shape along the tangential force direction. However, the larger the defect size, the later the crack is initiated. The leading edge material is continuously squeezed into the defect by the tangential force, and a larger plastic deformation layer is formed, which causes the RCF at the leading edge to crack more severely. Meanwhile, under the effect of combined normal force and shear stress, the leading edge crack intersects with the middle edge crack, and the leading edge material is spalled off first. Wheel RCF damage and wear are aggravated by rail corrosion, the longer the corrosion time, the more serious the RCF damage and wear, and the earlier the material spalling time, the lower the fatigue life. Full article

The accuracy of numerical predictions in sheet metal processes involving multiaxial stress–strain states (e.g., blanking, riveting, and incremental forming) heavily depends on the characterisation of plastic anisotropy under multiaxial loading conditions. A fully calibrated 3D plastic anisotropy model is essential for this purpose. While in-plane material behaviour can be conventionally characterised through uniaxial and equi-biaxial tensile tests, calibrating out-of-plane material behaviour remains a significant challenge. This behaviour, governed by out-of-plane shear stress and associated material parameters, is typically described by out-of-plane shear yielding. These parameters are notoriously difficult to determine, leading researchers to frequently assume isotropic behaviour or identical shear parameters for in-plane and out-of-plane responses. Although advanced calibrations may utilise crystal plasticity modelling, there remains a critical need for macro-mechanical characterisation methods. This paper presents an out-of-plane shear testing and material characterisation procedure based on full-field strain measurements using digital image correlation (DIC). Strains within the shear zone are measured via DIC and employed in the Finite Element Model Updating (FEMU) to identify out-of-plane shear parameters of a 2.42 mm thick, cold-rolled AW5754-H22 aluminium alloy sheet, using the Yld2004-18p yield criterion. Given that the characteristic strain response at this scale may be influenced by local crystal structure behaviour on the surface, this paper evaluates the feasibility of such measurements. Finally, to test the validity of the full-field-based approach, the FEMU-identified parameters are compared against results obtained through a classical optimisation procedure based on force-elongation measurements from the shear zone. Full article

In order to reduce the edge waves and defects of the strip in the forming process and obtain better properties of the strip, it is urgent to establish a better flexible cold forming process. In this paper, a finite element model of the production line was established to simulate the forming process, and the effective stress distribution at the corner of the strip was simulated. The effect of cold working hardening was basically consistent with that calculated by the analytical method and tensile test results. A mathematical model of the maximum normal strain along the tangent direction of the strip’s outer edge of each pass was established. With the constraint conditions that the maximum value of the normal strain value of each pass is less than the critical value and the upper and lower limit of the horizontal value of each test factor, and the maximum value of the normal strain of each pass as the goal, the number of cold forming passes, the bending angle of each pass and the working roll diameter of the roll have been determined. The optimized process parameters were used in the simulations. No edge wave at the strip edge and no “Bauschinger effect” in forming before high-frequency induction welding was found. The method proposed in this paper can optimize the key process parameters before the production line is put into operation, minimize the possible buckling of the strip edge during the forming process, and reduce the possible loss caused by design defects. Full article