Strip Thickness Research Articles

Vortex-induced vibration of a slender flexible riser with grooved and spanwise strips subject to uniform currents

We report a numerical investigation of the suppression of “vortex-induced vibration” (VIV) of a cylindrical flexible riser to which are attached various grooved or strip configurations with the ensemble exposed to uniform flow. Based on the thick-strip model, the simulation is done using our in-house three-dimensional VIV solver based on the Open Field Operation and Manipulation toolbox and developed at Shanghai Jiao Tong University (referred to as “viv3D-FOAM-SJTU”). The solver is applied to calculate all the simulations; it uses the Navier–Stokes equations to calculate flow field and the Euler–Bernoulli bending-beam hypothesis to calculate the vibrational displacements of the riser. A slender flexible riser with two spanwise symmetrical strips is first used to determine the appropriate installation angle of the strips, and cylindrical or grooved risers with different strip configurations are used to improve VIV suppression. The numerical results show that the spanwise strip installation angles of 30° and 45° suppress VIV due to the secondary separation of the boundary layer, but suffer from higher crossflow vibration frequency, which brings the risk of inducing high-order mode vibration, the enhancement of the lift correlation along the spanwise direction, and the increment of total drag. The main function of spanwise strips installed at 135° and 150° is to divide the wake region, which also helps suppress VIV. The introduction of grooves in the riser combined with strips of suitable thickness reduces the correlation of lift along the span, which in turn reduces crossflow vibration frequency and the total drag, and enhances VIV suppression. Of all the configurations, the grooved riser with four staggered symmetrical strips most strongly suppresses VIV in the crossflow direction.

Experimental validation of machine learning models for prediction of the thickness distribution of directionally rolled copper strips under scaling law

Predicting the results of multi-stage deep drawing in determining the thickness distribution and thinning of the workpiece are measures that will help reduce production costs by saving materials and production time. Machine Learning (ML) technique is a promising method for predicting the thickness distribution (TD) of drawn copper metal. Macro and micro products are currently used in sensitive electronic and structural applications. In this study, ML defines the relationship between the scaled thickness and the respective number of stages governed by the scaling law. It includes the development of Artificial Neural Network (ANN) tools based on machine learning to model the relationship between thickness by scaling law and stages based on multi-stage deep-drawn cups. TD is a measure of consistency. The TD is measured from the initial blank of 1500 mm long, 750 mm wide, and 6 mm thick Cu strip, reduced by 50% in nine successive steps until a final thickness of 0.1875 mm. Two ANN models used for TD prediction are Bayesian regularization (BR) and Levenberg-Marquardt (LM) algorithms. A trained machine learning model can successfully predict and verify the unseen data of 1.5 and 0.38 mm TD. ANN is used to predict the Finite Element Analysis (FEA) results and confirm them through the experimental results. The developed model can predict the TD of the multi-stage cup with the die design parameters. The difference between the TD predicted value and the measured value is based on the simulation results of multi-stage cups using the finite element method. When the predicted and measured TD, the difference in cup drawing depth is 0.5%–2.0%. The results show that the LM model is suitable for predicting the TD of formed copper cups following the scaling law.

Center Line Globular Structure of Strip Cast Using High Speed Twin Roll Caster

Formation of a centerline globular structure in an aluminum alloy strip cast using a vertical type high-speed twin-roll caster was investigated. The theory that the crystals form at tip of the nozzle and are conveyed to the roll gap was investigated by roll casting using a cooling slope and clad-strip-casting in this study. In high-speed roll casting, the center of the strip thickness is semisolid, and the temperature gradient in the thickness direction is small. The latent heat of the semisolid metal heats the dendrite structure, which is divided by melting. The dendrite structure was divided as in thixocasting, which is the mechanism of formation of a globular crystal form. The zone of the semisolid metal becomes narrow as the roll load increases or the pouring temperature of the molten metal decreases. As result, the zone containing globular crystal structures becomes thinner.

Microstructure, texture, and mechanical properties of asymmetrically cold-rolled Ni1.5FeCrCu0.5 high-entropy alloy

This study deals with the microstructural evolution, texture development, and mechanical properties of the cold-rolled and annealed Ni1.5FeCrCu0.5 high-entropy alloy (HEA). In addition to symmetric rolling (SR), asymmetric rolling (AR) was performed with different velocity ratios (VRs) between the working rolls. Electron backscatter diffraction (EBSD) measurements showed that the grain size of the annealed samples was drastically reduced by increasing the VR of the rolls and imposing shear strain. Moreover, annealing was associated with forming a high volume fraction of annealing twins. Recovery was accelerated by increased accumulated shear strain through the thickness of the ARed strips. The X-ray diffraction (XRD) method was employed to investigate the crystallographic texture in the processed high-entropy alloy. Macrotexture data revealed that the intensity of E {111} <110> and F {111} <112> shear texture components were remarkably higher in the ARed sheets. However, the intensities of S {123} <634> and Copper {112} <111> orientations were decreased in favor of the Brass {011} <211> component, indicating the pure-metal to alloy type texture transition in low stacking fault energy (SFE) materials. Compared to the homogenized sample, the Cube {001} <100> component was dramatically weakened by the annealing of the cold-rolled specimens. In terms of the mechanical properties, the pronounced grain refinement of the post-roll annealed strips enhanced the yield strength (YS) and ultimate tensile strength (UTS) from 332 to 503 in the homogenized condition to 625 and 709 MPa in the asymmetrically rolled (ARed) sample with a velocity ratio of 8. Finally, plastic anisotropy analysis demonstrated that the sheet drawability was gradually improved by increasing the velocity ratio due to the increased mean r-values and reduced planar anisotropy (Δr) values.

Solid State Joining of a Cold Rolled Zr-Based Bulk Metallic Glass to a Wrought Aluminum Alloy by Power Ultrasonics.

Ultrasonic metal welding (UMW) enables joining in the solid state at relative low temperatures with short cycle times. This technique is of particular interest for joining metallic glasses to each other or to other materials, because crystallization of the amorphous structure can be prevented due to the low thermal loading and the rapidity of the process. In this work, UMW is applied to join one 1 mm thick sheet of a commercial wrought aluminum alloy (AA5754) and one 0.4 mm thick strip of a commercial Zr-based bulk metallic glass (AMZ4). The introduced heat of the welding process is detected with thermocouples and thermal imaging. To investigate the strength of the joint and the influence on the microstructure, mechanical tensile tests are carried out in combination with scanning electron microscopy and differential scanning calorimetry. The results show that ultrasonic metal welding is a suitable technique to join amorphous bulk metallic glasses to crystalline aluminum alloys. The metallic glass component retains its amorphous structure in the joint, and the joint strength is higher than the strength of the Al sheet. These findings will help to develop future applications of BMG-based multi-material components, including medical tools.

Investigation of the features of the formation of the structure of steel 08Yu during asymmetric rolling on a new mill 400

A study of the 08Yu steel structure during cold rolling at a new rolling mill in the Zhilyaev Laboratory of Mechanics of Gradient Nanomaterials of the Nosov Magnitogorsk State Technical University. It has been found that asymmetric rolling in rollers with speeds that differ 5 times and all other things being equal, resulted in the formation of a gradient structure. In the upper part of the strip section on the side where the rolling speed was lower, a uniform structure is observed, which is formed at more than half the strip thickness and consists of ultra-fine practically equiaxial grains of less than 1000 nm in size. The formation of the ultrafine structure is explained by the dynamic recrystallization under the conditions of heating the strip to a temperature of 250&ndash;300 &ordm;C during rolling. In the lower part, on the side where the rolling speed was higher, a fibrous structure with smaller fragments up to 200 nm in size within individual fibers is clearly revealed. The hardness after asymmetric rolling compared to symmetrical rolling increased slightly and turned out to be more evenly distributed over the section. The difference in its values of different sections was not more than 15 % compared to symmetrical rolling, where the hardness in the central and perephyrian sections of the strip section differed by about 35 %. It has been found that these asymmetric rolling conditions lead to a simultaneous increase in reduction from 50 to 80 % and a decrease in force of almost 3 times per pass compared to symmetrical rolling, which can be explained by grinding the structure.The study was carried out within the framework of grants from the Russian Science&nbsp;Foundation (No. 20-69-46042 dated May 20, 2020), RFBR (No. 20-38-90097 dated&nbsp;September 3, 2020) and Megagrant (No. 075-15-2021-627 dated June 8, 2021).

Strip thickness prediction method based on improved border collie optimizing LSTM.

The thickness accuracy of strip is an important indicator to measure the quality of strip, and the control of the thickness accuracy of strip is the key for the high-quality strip products in the rolling industry. A thickness prediction method of strip based on Long Short-Term Memory (LSTM) optimized by improved border collie optimization (IBCO) algorithm is proposed. First, chaotic mapping and dynamic weighting strategy are introduced into IBCO to overcome the shortcomings of uneven initial population distribution and inaccurate optimization states of some individuals in Border Collie Optimization (BCO). Second, Long Short-Term Memory (LSTM) which can effectively deal with time series data and alleviate long-term dependencies is adopted. What's more, IBCO is utilized to optimize parameters to mitigate the influence of hyperparameters such as the number of hidden neurons and learning rate on the prediction accuracy of LSTM, so IBCO-LSTM is established. The experiments are carried out on the measured strip data, which proves the excellent prediction performance of IBCO-LSTM. The experiments are carried out on the actual strip data, which prove that IBCO-LSTM has excellent capability of prediction.

Strip Thickness and Profile–Flatness Prediction in Tandem Hot Rolling Process Using Mechanism Model‐Guided Machine Learning

This study is focused on the multivariable, nonlinear, strong‐coupling, and time‐varying characteristics of the quality control process of hot strip rolling. Using the rolling process data from a continuously variable crown (CVC) mill of a 1580 mm hot tandem rolling line, a new prediction model of the strip thickness, profile, and flatness in hot rolling based on rolling mechanism model‐guided machine learning (ML) is developed. The weighted processing (WP) method is used to fuse the rolling mechanism and process data, to improve the relationship between the strong correlation features and the model. Combined with nondominated sorting genetic algorithm III (NSGA‐III), multiple parameters of multioutput support vector regression (M‐SVR) are optimized. The results show that the root mean square error (RMSE), mean square correlation coefficient (R 2), and mean absolute error (MAE) of the strip thickness, crown, and flatness are 2.0159, 1.3191, and 0.9355; 0.9854, 0.9895, and 0.9873; and 16.601, 1.126, and 0.604, respectively. Moreover, the established method of data fusion rolling mechanism shows strong capability to improve the model prediction accuracy, increasing it by 60%. Thus, it can offer theoretical guidance for realizing accurate control of the quality of strips and improving the quality of hot‐rolled products.

Flexural fatigue strains of constituent materials in strengthened RC beams with UHPC strips

This paper presents the comprehensive experimental studies to obtain the strain responses of constituent material in the strengthened RC beams with UHPC strips. The experiments involved static and fatigue tests on 20 beams in each beam category to predict the strain response of strengthened beams with 5, 10 and 15 mm thick UHPC strips. From the experimental results, the strain in main reinforcement was significantly reduced in beams with 10 and 15 mm thick UHPC strip comparatively, which exhibited the improved fatigue responses. Micro analytical and numerical simulations were carried out to predict or confirm the experimental observations.

Experimental study and theoretical analysis on the flexural behavior of glulam bolted joints with prestressed steel strips

The glulam bolted joint with prestressed steel strips was proposed and investigated systematically. Experimental study was conducted considering the variation of pre-strain of steel strips. The presence of prestressed steel strips led to a delay in the onset and propagation of cracking with a pronounced increase in bearing capacity compared with ordinary glulam bolted joints, i.e. by 41.15%, 52.01% and 53.33%, respectively, and significantly higher deformation capacity, with the ductility increasing by 15.38%, 88.11% and 104.90% respectively. A three-dimensional finite element analysis considering mixed-mode cohesive zone modeling was performed and verified to be effective to reproduce crack path observed in the experiments. Moreover, a quasi-non-linear fracture mechanics model based on a Timoshenko beam on elastic foundation theory was extended in order to take into account the influence of the prestressed steel strips on the ultimate bearing capacity. Analytical results demonstrated how ultimate bearing capacity changed with pre-strain, thickness, width and spacing of strips and a series of design recommendations were supplied.

Variation Law of Thickness Fraction of Three-Laminated Aluminum Composite Plate by Solid–Liquid–Solid and Liquid–Solid–Liquid Twin-Roll Casting

Solid–liquid–solid twin-roll casting (SLS-TRC) and liquid–solid–liquid twin-roll casting (LSL-TRC) are two processes for manufacturing three-laminated aluminum composite plates by using solid–liquid cast-rolling composite technology. In order to study the variation law of thickness fractions, a 1060/3003/1060 three-laminated aluminum composite plate was taken as the manufacturing product, and the thickness of the solid strip was used as the variable. Based on the “uactive” user subroutines of MSC.MARC software, the 2D thermomechanical coupling models of SLS-TRC and LSL-TRC were established respectively, and the thickness variation law of the solid strip under the two processes was obtained and verified by experiments. Finally, the recommended process was given according to the target thickness fraction. The results show that with an increase in the cladding thickness, the KISS point (complete freezing point of molten metal) height of the SLS-TRC process increases, the coordinated deformation position decreases relative to the KISS point, and the strain increases. In the LSL-TRC process, as the thickness of the core increases, KISS point height increases, the coordinated deformation position decreases relative to the KISS point, and the strain decreases. The formation process of the composite interface of the two processes is consistent with the N. Bay theory. Finally, through the comparison of cast-rolling forces, it was found that when manufacturing a three-laminated aluminum composite plate with a relatively small thickness fraction (the thickness fraction is less than 30%), the SLS-TRC process requires less load; when the thickness fraction of the three-laminated aluminum composite plate is large (the thickness fraction is greater than 30%), the load required for the manufacturing of the LSL-TRC process is small. The results of this research can provide practical guidance for the manufacturing of three-laminated metal matrix composite panels.

Frictional analysis on stiffness and damping characteristics of bump foil gas bearings

Gas foil bearing has been used in high-speed turbomachinery for its high speed, high adaptability, and eco-friendly. The stability of the rotor bearing system is greatly enhanced due to the flexible foil support structure. In the foil supporting structure, vibration energy of the rotor bearing system can be absorbed by the Coulomb friction dissipation. In order to evaluate the frictional dissipation on bearing performance, a quasi-2-dimensional mechanical model is proposed considering the Coulomb friction. The Coulomb damping dissipation characteristics of the bearing in operating conditions are analyzed by coupling gas film. Frictional analysis is conducted on the bump foil bearing with different structural parameters, such as bump height, foil thickness, friction coefficient and number of bump foil strips. The stiffness of the foil bump is less affected by the base load. In the process of foil bearing design, the optimal friction coefficient, bump height should be properly selected in favor of either foil bearing stiffness or damping characteristics. In addition, the overall performance of bump foil bearing is strongly affected by the number of bump foil strips.

On the role of carbonitrides in formation of austenite grains during continuous hot rolling of pipe steel

A study of the formation of austenite grain size during rolling of a thick strip on a continuous mill by simulating multi-stage rolling on a Gleeble complex has been performed. It is shown that at low degrees of deformation in the stands of the finishing group of a rolling mill, the formation of a different-grained austenite structure can occur due to selective grain growth without the formation of recrystallization nuclei, despite the precipitation of carbonitrides of microalloying elements. The value of the difference between the deformation strengthening of neighboring grains, sufficient for the grain boundary to overcome the retardation caused by the carbonitride particles, has been determined. It is possible to avoid this negative phenomenon by increasing the degree of deformation in each pass and ensuring the conditions for the formation of recrystallization nuclei. An example of a similar phenomenon observed when rolling beryllium is given.The research was carried out with the financial support of the Ministry of Education&nbsp;and Science of Russia as part of the implementation of the program of the world-class&nbsp;Scientific Center in the direction of "Advanced Digital Technologies" of SPbPU (agreement&nbsp;dated April 20, 2022 No. 075-15-2022-311).

Enhancement of energy capture by flow induced motion of a circular cylinder using passive turbulence control: Decoupling strip thickness and roughness effects

Passive turbulence control of flow induced motion of a cylinder using strips has been practiced for over 30 years. The two distinct physical characteristics of strips: thickness and roughness, can have coupled effects on altering the flow induced motion. The experimental work discussed here decouples these two effects for augmented energy extraction. Tests with cylinders attached with strips of roughness varying from 0% to 100%, and thickness varying from 0.8% to 8.2% of the cylinder diameter, were performed (5000 < Re < 35600). The dynamic response of the configurations with rough strips was compared to that with smooth strips of same thickness. Mechanical power and energy transfer efficiencies were evaluated to analyze the power extraction potential of different configurations. Power generated by the smooth strip configurations was 1.25–5 times higher depending on the roughness ratio and flow velocity. Smooth strips also provided more operational stability, characterized by smaller values of the coefficient of variation of power and concentrated non-dimensional force-velocity states. These devices are the more efficient adaptation from an energy harvesting perspective at low velocities (<1.0 m/s), a range below the cut-in speed for most hydrokinetic turbines, thereby making energy extraction feasible from shallow rivers and slow-flowing streams.

Orientation and depth dependent mechanical properties of the porcine cornea: Experiments and parameter identification

The porcine cornea is a standard animal model in ophthalmic research, making its biomechanical characterization and modeling important to develop novel treatments such as crosslinking and refractive surgeries. In this study, we present a numerical model of the porcine cornea based on experimental measurements that captures both the depth dependence and orientation dependence of the mechanical response. The mechanical parameters of the established anisotropic hyperelastic material models of Gasser, Holzapfel and Ogden (HGO) and Markert were determined using tensile tests. Corneas were cut with a femtosecond laser in the anterior (100 μm), central (350 μm), and posterior (600 μm) regions into nasal-temporal, superior-inferior, and diagonal strips of 150 μm thickness. These uniformly thick strips were tested at a low speed using a single-axis testing machine. The results showed that the corneal mechanical properties remained constant in the anterior half of the cornea regardless of orientation, but that the material softened in the posterior layer. These results are consistent with the circular orientation of collagen observed in porcine corneas using X-ray scattering. In addition, the parameters obtained for the HGO model were able to reproduce the published inflation tests, indicating that it is suitable for simulating the mechanical response of the entire cornea. Such a model constitutes the basis for in silico platforms to develop new ophthalmic treatments. In this way, researchers can match their experimental surrogate porcine model with a numerical counterpart and validate the prediction of their algorithms in a complete and accessible environment.

Dynamic Amplitude-Frequency Characteristics of Vertical–Torsional Coupling System with Harmonic Response in Hot Tandem Mill

Vibration is a common and urgent technical issue in the steel industry. The world’s first multi-mode continuous-casting and rolling plant of Shou Gang Jing Tang Iron and Steel Co., Ltd. (Tangshan, China), has a finishing mill, F3, that experiences frequent, strong vibrations during the process of rolling thin-gauge (&lt;1.5 mm) strip steel, which have seriously hindered the production of high-quality thin strip steel products. The changes in the strips’ surface quality are among the factors that induce rolling mill vibrations. In this study, considering the nonlinear surface quality of strip steel, a finite element model of the F3 mill was established, and the harmonic response method was used to obtain a rolling mill vertical system in the ANSYS environment. This study assesses the sensitive amplitude versus frequency characteristics curve of a torsional coupling system, the influence of strip thickness and strip hardness fluctuations on the vibration of the primary drive system, and the dynamic amplitude versus frequency characteristics of the three directions on the top of a torii. Finally, the field experiment verifies the correctness of the analytical results, which provides theoretical guidance for suppressing rolling mill vibrations and has a certain application value.

The Effect of the Thermal Deformation of Casting Roll on Strip Thickness in the Strip Casting Process

Many factors affect the strip thickness in the industrial production process of twin‐roll strip casting, such as pouring temperature, casting speed, cooling capacity, cast‐rolling force, and so on. When the pouring temperature and cooling capacity are specified, the magnitude of the cast‐rolling force is determined by the actual roll gap, which has a significant effect on the thickness, shape, and surface quality of the cast strip. As a result, the actual roll gap size is critical for smooth realization. In the actual casting process, thermal deformation is a direct factor influencing the change in roll gap shape for a given roll gap value. Hence, any factor influencing the thermal deformation indirectly influences the roll gap shape. Thus, the critical factors determining the thermal deformation are simulated and studied in this research, which is integrated with actual production, based on the application and secondary development of ANSYS. The effect law of each process parameter on the thermal deformation of the casting roll is given, and corresponding mathematical models are established. This research lays the foundation for the establishment of the cast strip thickness control model and the realization of online control of strip thickness.

LES/DNS fluid-structure interaction simulation of non-linear slender structures in Nektar++ framework

Nektar++ is a spectral/hp element open-source framework written in C++ for the construction of classical low-order h-type as well as higher-order p-type finite element solvers. It seeks to overcome the implementation challenges of the complex data structures associated with high-order finite element methods; hence, providing an efficient, flexible and HPC scalable platform for the development of solvers for partial differential equations using the spectral/hp element method. In the present work, capabilities of Nektar++ is leveraged for development of two fluid-structure interaction (FSI) solvers for simulations of highly deformable nonlinear slender structures. The FSI solver uses the incompressible Navier-Stokes (NS) solvers of Nektar++ for fluid flow while the structural dynamics is modelled using Geometrically-Exact Composite Beams (GECB). The open-source SHARPy framework is linked to Nektar++ and used for structural simulation. Aiming at high-fidelity (LES/DNS) FSI simulations, the thick-strip approach is used to reduce computational costs. In this approach, the full 3D fluid domain is represented with series of smaller 3D domains normal to the local axis of the structure and having a finite thickness in the spanwise direction where periodicity is also assumed. Hence, while reducing the computational costs by avoiding the discretization of equations over the entire slender structure, the strip thickness allows capturing the local 3D turbulent wake and accurately predict the fluid forces on the structure. Two approaches are adopted to avoid the dynamic remeshing due to the large and non-linear deformation of the structure. In the first approach, the transformed the NS equations are solved in the non-inertial body-fitted coordinates while in the second approach the NS equations are formulated in the moving frame of reference and solved with the spectral/hp element method. A hybrid parallelisation approach of Nektar++ is extended for the thick-strip method which allows having non-constant cross-section along the structural span as well as efficient and flexible use of computational resources, and excellent HPC performance for the FSI simulations. The capability of the FSI solver is demonstrated via several examples.

A space deployable antenna model based on shape memory alloy composite with folding‐deploying two‐way behavior

AbstractIn this study, a flexible space deployable antenna model with good self‐folding and deploying two‐way shape memory effect is proposed and prepared based on shape memory alloy composite strips and polyimide thin film. The thickness and cyclic properties of the shape memory alloy strip were considered for the two‐way shape memory effect. Good self‐folding at 110°C and self‐deploying at 20°C for 10 min were demonstrated. Moreover, the Joule heating method was applied to improve the folding speed within 90 s. The two‐way shape memory effect with reversible self‐folding and deploying behavior of the space deployable antennas is aimed at improving avoidance of space debris in future applications.

Mathematical study on the propagation of Griffith crack in a dry sandy strip subjected to punch pressure

The present study investigates the features of a moving Griffith crack in a dry sandy infinitely long and finitely thick isotropic strip with moving parallel punches of constant load acting on both of its boundaries owing to plane wave propagation under point loading. Coupled singular integral equations and Cauchy-type singularities are used to formulate the present model, the Dirac delta function is employed to analyse the point load located at the moving crack edge, and the properties of Hilbert transformation are employed to obtain the closed-form expression of the stress intensity factor with constant point loading. For the sake of validation, the obtained results are matched with pre-established and standard results. Numerical simulations and graphical illustrations are performed to analyse the influences of the prevalent parameters, viz., sandiness parameter, punch pressure, distinct point load positions, length and speed of the crack corresponding to the plane wave on the stress intensity factor for the considered dry sandy isotropic material strip.