Forward Slip Research Articles

Study on High-Precision Tension Control Technology for a Cold-Rolling Pilot Mill with Hydraulic Tension

Tension control in cold-rolling pilot mills (CRPMs) with hydraulic tension is subject to extraneous forces resulting from positional disturbances, strong coupling, and time-varying characteristics, making it challenging to achieve ideal control results using the existing control methods. Therefore, in this study, a mathematical model of tension is first derived and then used to analyze the properties and difficulties associated with tension control. Second, a hydraulic servo-control system based on servovalves and proportional pressure relief valves is developed. In this system, redundant feedforward flow is generated by a servovalve according to the rolling schedule. The surplus flow is absorbed by a proportional pressure relief valve in the closed-loop control of tension. Third, simulation analysis is performed. Under severe friction disturbance (maximum 0.2 kN), and with the wide range of forward and backward slip, an accuracy of ±0.27 kN in tension control can still be achieved using the proposed control strategy, thereby demonstrating its effectiveness. Moreover, it has obvious advantages over existing control methods. Finally, an experimental study of tension is carried out in the cold-rolling mill with a maximum tension capacity of 50 kN, achieving ±0.2 kN tension control precision in the multipass rolling process.

Contribution of viscous shear to friction in cold rolling of low-carbon steel

This work shows that for temperatures, pressures and shear rates that are common in cold rolling of low-carbon steel, viscous shear stress significantly contributes to the total friction force. Experiments were carried out to validate the theory on lubricant film formation and elasto-hydrodynamic lubrication, both with laboratory scale tribometers and a semi-industrial pilot mill facility. These experiments showed that at high shear rates, that are common in cold rolling, the lubricant does not behave as a Newtonian fluid anymore; moreover the viscosity at high pressure cannot accurately be described by a simple exponential law. With the correct relations implemented in a rolling model, both rolling force and forward slip are predicted with good accuracy for hydrodynamically lubricated cold rolling experiments.

Analysis of the Varying Thickness Rolling Process Based on the Principle of Pre-Displacement

This paper conducts a comprehensive analysis of the varying thickness rolling process, grounded in the principle of pre-displacement. Within the rolling deformation zone, the subject is divided into three distinct areas: the backward slip zone, sticking zone, and forward slip zone. We propose a model that delineates the sticking-sliding motion between the rolled piece and the roller, all within the context of the rolling deformation zone, and derive a calculation method for determining the longitudinal lengths of both the sliding and sticking zones within this area. Unlike existing full sliding and full sticking models, our sticking-sliding model offers a novel perspective, overcoming inherent limitations when analyzing the rolling process. Furthermore, we establish models to describe the neutral angle and forward slip value and to predict the longitudinal length of the rolled piece during the varying thickness rolling process. A comparison of our calculated results with experimental data demonstrates the feasibility and effectiveness of the method, thereby laying a robust theoretical foundation for the varying thickness rolling process.

Analysis of the roll imprint on the cross-sectional area of hot rolled wire rod by frequency spectroscopy

This work presents an approach for analysing the sensor data of an eddy-current based cross-sectional area measurement for hot rod and wire steel in an innovative manner and for approximating the influence on the forward slip by longitudinal tensile forces between the mill stands. The method is based on frequency spectroscopy of the cross-sectional area of the rolled stock. The measurement data of three sensors already implemented in two hot rolling mills is used in order to obtain information out of the roll imprint on the cross-sectional area. Since measurement data from two measuring sites and from three sensors are evaluated, this allows statements to be made about the reliability and reproducibility of the measurement and shows that the method can be used for different rolling blocks such as 3-roll and 2-roll blocks. In addition, a mathematical model is presented which allows conclusions to be drawn about possible causes for certain characteristics in the measured frequency spectrum of the cross-sectional area.

Mode-II progressive fracture of sawn timber and timber-adhesive bond: experimental evaluation of end notched flexure (ENF) testing using DIC

The end-notched flexure (ENF) testing technique has been used in this paper to investigate the Mode II fracture behaviour of sawn timber and timber-adhesive bonds. Mode-II strain energy release rates were obtained by using classical data reduction schemes based on actual crack lengths captured using digital image correlation (DIC) technique. The compliance-based beam method (CBBM), which does not require the actual crack length measurements, was also evaluated for its suitability for Mode-II fracture of timber. Utilizing forward shear slip measurement from DIC at every millimetre of crack length, a simple yet effective and innovative technique to identify crack tip opening and to monitor crack length has been proposed herein. Three different initial notch widths were used in the current study to examine their suitability in producing reliable crack initiation and consistent bond delamination in solid timber and glued timber. The strain energy release rates calculated from the actual crack and equivalent crack length values showed similar trends in fracture resistance curves, which are commonly known as R curves, but the initial strain energy release rate (GII0) and the critical strain energy rate (GIIC) obtained from the two methods showed some discrepancies. Equivalent crack method CBBM was found to be inadequate in determining a consistent initial strain energy release rate despite producing a stable and steady fracture energy after crack initiation. Experimental results showed that Mode-II timber-adhesive bond line fracture is relatively more brittle than timber fracture, and the average critical strain energy release rate of timber-adhesive bond (GIIc) was 14% greater than that of sawn timber. Based on experimental observations, specific test criteria for ENF testing of timber structures are proposed in this paper.

Microstructure and Crystallographic Texture in Twin-Roll Casting of AA1050 Aluminum Alloy: Simulation and Industrial Validation

Twin-roll casting (TRC) is a process in which liquid metal is introduced directly between counter-rotating water-cooled rolls, where it solidifies and is rolled to a strip having final thickness of 3 to 8 mm. TRC for aluminum is best suited to those alloys having a narrow freezing range with little susceptibility to hot tearing, such as 1XXX, 3XXX, 5XXX, and 8XXX. TRC offers advantages over conventional DC casting followed by hot and cold rolling for these alloys due to its lower capital cost, and decreased downstream processing operational cost and energy consumption, since hot rolling is not required. The microstructure formed in the strip must be carefully controlled, because as a near-net shape product used mostly for non-age-hardenable alloys, there is limited opportunity to modify it by subsequent processing. In particular, the near-surface microstructure has a strong effect on performance in forming applications. In this article, we present a computational model of TRC, and validate it for AA1050 aluminum alloy in a production environment. The novel aspect of this work is that the model is used to predict the final microstructure and crystallographic texture of the cast strip. The model is validated in plant trials for strip cast at a range of thicknesses, casting speeds, and caster setup by comparing the predicted microstructure, texture, and process outcomes such as roll separating force and forward slip to their corresponding measured values. We then apply the validated model to explore process parameters outside the standard practices, including feed inlet setback, casting speed, metal inlet temperature, and changing roll material to demonstrate how the microstructure and texture can be controlled via these parameters.

Diagnosis and treatment of left ureteral injury as a rare complication of oblique lumbar interbody fusion surgery: a case report and literature review

BackgroundOblique lumbar interbody fusion (OLIF) surgery has been performed as a minimally invasive lateral lumbar fusion technique in recent years. Reports of operative complications of OLIF are limited, and there are fewer reports of ureteral injuries.Case presentationA 62-year-old Chinese woman diagnosed with "lumbar spondylolisthesis (L4 forward slip, I degree)" underwent OLIF treatment. The surgical decompression process was smooth, and the cage was successfully placed. After the expansion sleeve of OLIF was removed, clear liquid continuous outflow from the peritoneum was found. The patient was diagnosed with a ureteral injury. The urological surgeon expanded the original incision, and left ureteral injury anastomosis and ureteral stent implantation were performed. The patient was changed to the prone position and a percutaneous pedicle screw was placed in the corresponding vertebral body. The patient was indwelled with a catheter for 2 weeks, and regular oral administration of levofloxacin to prevent urinary tract infection. After 2 months, the double J tube was removed using a cystoscope. One year after surgery, the symptoms of lumbar back were significantly improved, and there were no urinary system symptoms. However, the patient needed an annual left ureter and kidney B-ultrasound.ConclusionUreteral injury is a rare complication and is easily missed in OLIF surgery. If the diagnosis is missed, the consequences can be serious. Patients should undergo catheterization before the operation and hematuria should be observed during the operation. We emphasize the careful use of surgical instruments to prevent intraoperative complications. In addition, after withdrawing the leaf in the operation, it is necessary to carefully observe whether a clear liquid continues to leak. If ureteral injury is found, one-stage ureteral injury repair operation should be performed to prevent ureteral stricture.

A Model for Roll-Drawing of Full Sections with Experimental Verification

Roll-drawing of full sections is an alternate process for wire drawing through a closed die, as it conserves less hard tool materials. It therefore enhances the resource efficiency of thin wire production. As the tools are rotating, the relative velocity is lower and friction is reduced. Apart from this, there is only little knowledge about the process mechanics inside the deformation region. According to the relative motion mentioned above, a neutral point should exist within the deformation region, but this hypothesis is unconfirmed until today. In the present work, a combination of an improved empirical model for the lateral spread in roll-drawing and a mechanical model for roll drawing based on the slab method is proposed. The mechanical model deviates from the well-known rolling theory by the fact that a zero deformation torque should exist on the rolls, it predicts the neutral angle, the forward-slip, the external drawing force and the roll separating force. The hypothesis of existence of a neutral point in the deformation region is supported by experimental measurements of the nonzero forward slip in the roll-drawing process. Measurement is done on copper wire, where 200 passes with initial round section sizes ranging from 2 mm to 1.3 mm with an increment of 0.1 mm are evaluated.

Smart Wearable Device for Quantification of Risk of Fall: Exploring Role of Gait Phases and Knee Bending Angle for Parkinson's Patients.

Gait disturbances with falls are common among patients with Parkinson's disease. Falls commonly occur from slips while walking on pathways with turns. Gait phases namely Loading Response and Terminal Stance are linked with forward and backward slips. Also, postural deformities (connected with knee joint angles) are debilitating symptoms of Parkinson's patients and are related with falls. Here, we have focused on exploring the contribution of Loading Response and Terminal Stance to risk of fall along with the relevance of postural deformity (e.g., knee bending) while an individual walked overground on pathways (with 0° and 180° turn) under dual task condition. For this, we have used a wearable device consisting of a pair of Sensored shoes and Knee Bending Angle Recorder Units. The device was used to compute Coefficient of Variation of knee bending angle during different gait phases as an indicator of one's risk of fall that corroborated with clinical measure. Clinical Relevance- A study with age and gender matched healthy and Parkinson's individuals indicated the importance of Loading Response and pathway turn while assessing risk of fall. This can serve as important pre-clinical input while designing intervention paradigms.

Development and Evaluation of a Slip Detection Algorithm for Walking on Level and Inclined Ice Surfaces.

Slip-resistant footwear can prevent fall-related injuries on icy surfaces. Winter footwear slip resistance can be measured by the Maximum Achievable Angle (MAA) test, which measures the steepest ice-covered incline that participants can walk up and down without experiencing a slip. However, the MAA test requires the use of a human observer to detect slips, which increases the variability of the test. The objective of this study was to develop and evaluate an automated slip detection algorithm for walking on level and inclined ice surfaces to be used with the MAA test to replace the need for human observers. Kinematic data were collected from nine healthy young adults walking up and down on ice surfaces in a range from 0° to 12° using an optical motion capture system. Our algorithm segmented these data into steps and extracted features as inputs to two linear support vector machine classifiers. The two classifiers were trained, optimized, and validated to classify toe slips and heel slips, respectively. A total of approximately 11,000 steps from 9 healthy participants were collected, which included approximately 4700 slips. Our algorithm was able to detect slips with an overall F1 score of 90.1%. In addition, the algorithm was able to accurately classify backward toe slips, forward toe slips, backward heel slips, and forward heel slips with F1 scores of 97.3%, 54.5%, 80.9%, and 86.5%, respectively.

Evaluation of an actuated force plate-based robotic test setup to assess the slip resistance of footwear

Slipping is a frequent cause of occupational accidents. This is often due to an insufficient available coefficient of friction (ACOF) of footwear. The aim of this study was to present a footwear ACOF test setup, and to evaluate it based on device requirements presented in the ISO 13287 test standard. One left Airtox TX2 shoe underwent slip resistance measurements under three test modes (Forward flat slip, backward slip on the forefoot at angled contact and forward heel slip at angled contact), with six contaminant conditions (dry steel, dry tile, glycerine on steel, glycerine on tile, canola oil on steel and canola oil on tile). The test setup was successfully able to measure ACOF in close accordance to the ISO 13287 test standard with a good repeatability. Furthermore, the test setup can alter biomechanical and tribophysical testing conditions, which may provide more valid footwear ACOF measurements in the future. Relevance to industryThe setup can accommodate biomechanical and tribophysical testing conditions, hence the setup can be a tool for accessing more valid ACOF measurements - closer to real world slip events. Footwear manufactures or researchers, with the goal of improving footwear slip resistance, can implement the setup.

Estimation and Compensation of Ionospheric Phase Delay for Multi-Aperture InSAR: An Azimuth Split-Spectrum Interferometry Approach

Multiple aperture interferometric synthetic aperture radar (MAI) can measure ground displacements along SAR track. However, MAI measurements may suffer from severe ionospheric error, especially for long-wavelength SAR sensors. This study presents a new approach, azimuth split-spectrum interferometry (AziSSI), to correct ionospheric errors in MAI measurements. The proposed method can straightforwardly resolve ionospheric phase delay by exploiting two subband MAI interferograms with different centroid frequencies. We utilized two groups of ALOS-1 PALSAR images, which cover the 2008 Wenchuan earthquake containing strong coseismic ground deformation and a stable coast region in Chile, respectively, to test the proposed method. Experimental results show that the AziSSI method can successfully recover the coseismic displacements induced by the Wenchuan earthquake and circumvent the azimuth stripes for the Chile case’s MAI measurements. The maximum ionosphere-induced azimuth shifts are about 2.2 m for the Wenchuan case and 2.5 m for the Chile case. We validated the correction performance of the AziSSI method with the Wenchuan case by comparing the compensated azimuth displacements with the simulated deformation from a forward fault slip model and coseismic global positioning system (GPS) measurements. The validations show that the deformation patterns after the ionospheric correction are consistent with the simulations of the sinistral slip of the causative fault. The root-mean-square error between the GPS and MAI measurements is reduced from 0.77 to 0.28 m before and after the ionospheric correction, indicating that AziSSI can significantly compensate ionospheric errors for MAI.

Study of the friction coefficient during the steady-state process of continuous hot rolling of steel strips in conditions of the 1950 industrial mill

This paper describes a method for determining the value of the friction coefficient in a steady-state hot rolling under industrial conditions of the casting and rolling complex of “Vyksa Steel Works” located in Vyksa. The algorithm implies the forward slip method for determining the friction coefficient using the Ekelund formula. Measurements of hot rolling technological parameters from sensors are used as input parameters. Mathematical formulas are implemented in the ibaAnalyzer software, with the help of calculations are made for several thousand strips and data on the friction coefficient are obtained under various conditions. The data processing results demonstrate a normal distribution of the friction coefficient. The highest value of the friction coefficient is typical for the first finisher stands F1-F2, and the lowest values are found for the thinner gauge products rolled at high speed. The influence of the working layer of the work rolls on the friction value is demonstrated. High-chromium cast iron rolls have lower values of the friction coefficients, in contrast to indefinite cast iron, which is used for the working layer of the last finisher stands of mill 1950. A detailed comparison of the results with the classical methods for determining the friction coefficient in a steady-state process has been carried out. The dependence of the ratio of the friction coefficient during initial entry to the steady-state friction coefficient was refined.

An Evaluation of the Influence of Forward Slip on the Corrosion Behavior of Aluminum-Manganese Alloys

The tribological influence of hot rolling parameters, such as the work roll roughness, roll speed, and the number of rolling passes on the surface quality of rolled aluminum alloys, has been a subject of interest for the wrought aluminum industry. A hot rolling tribo-simulator was used to investigate the effect of forward slip on the surface damage induced by the rolling operation and the subsequent corrosion behavior of the Al-Mn alloys. A two-pass hot rolling schedule was conducted at 500–540 °C for forward slip levels of − 4, 1, 7, and 13% using an AISI 52100 steel work roll with a surface roughness (Ra) of 0.01 µm. Characterization of the rolled surfaces using scanning electron microscopy (SEM) revealed hot rolling-induced damage in the form of microcracks, nanocracks, and MgO coverage, which was more prominent for higher forward slips. Corrosion tests were subsequently conducted on the rolled Al-Mn specimens by immersion in a 0.5 wt.% NaCl solution. These tests showed greater corrosion-covered surface areas on samples rolled at lower forward slips. This relationship between the forward slip and corrosion behavior was due to the extent of surface damage induced at varying forward slip levels. The preferential corrosion mechanism was observed to be due to the dissolution of the MgO-rich near-surface microstructures induced during hot rolling.

An advanced model of lubricated cold rolling with its comprehensive pilot mill validation

The increasing demand for thinner and harder steel strips requires the introduction of flexible lubrication systems that continuously adapt the lubrication conditions in existing rolling mills to not saturate the stand capacity by excessive friction. To design these systems, this article introduces one of the most advanced models of lubricated cold rolling since it combines the following features in a single model: elasto-thermo-viscoplasticity of the strip, mixed lubrication by a thermo-piezoviscous lubricant, full-flooded lubrication or starvation, and a complete formulation of non-circular roll flattening. This model is then validated by a new semi-industrial data set, which is one of the most comprehensive ones since it includes: roughness measurements of the rolls and the strips, hardening laws of the strips by plane-strain compression tests, thermo-piezoviscous material laws of the lubricants and a large design space to isolate the influence of individual operating parameters. The results indicate that the changes of the rolling force and the forward slip with the rolling speed and the reduction can be quantitatively predicted except for the decreasing forward slip with the reduction. These predictions require to calibrate the coefficients of boundary friction, thermoplasticity and viscoplasticity for each rolled product as well as the inlet film thickness at each rolling speed, if starvation occurs. Once calibrated, the model therefore allows to predict the influences of various operating conditions, e.g. by how much the rolling force can be reduced if more lubricant becomes available at the entry of the roll bite.

The Density of Deformations Distribution on the Side Edges during Strip Rolling

Experimental densities of intensity distribution for main deformations, as well as the stress strain state of a metal on the side edges of an aluminum strip during its flat rolling, have been determined. Strain, spread and extrusion ratio have been evaluated. The dimensions of the strip cross-section have been chosen in a way that minimizes spreading. Therefore, the deformed state under rolling is close to a flat one. The correlation between the deformation intensity and the stress-strain state of macro-volumes occurred on strip edges has been estimated. The parameters of two-dimensional probability-density function for the joint distribution of deformation intensity and the Nadai-Lode stress-strain parameter have been determined. Distribution densities for longitudinal, transverse deformations and the intensity of main deformations in the zone of strip rolling are bimodal, which corresponds to both forward and backward slip zones under rolling. The results of the work can be used to predict the depletion of plasticity resources during strip rolling.

Development of On-line Model of Forward Slip on Tandem Cold Strip Mill

Development of On-line Model of Forward Slip on Tandem Cold Strip Mill

DETERMINATION OF THE FRICTION COEFFICIENT IN THE PROCESS OF HIGH-SPEED ROLLING

The aim of this work is to determine the probable range of changes in the coefficient of friction for a stable process of high-speed rolling. The friction coefficients were determined using the modified Blend-Ford method, the empirical Ekelund dependence taking into account the influence of velocity on the Zander dependence, and the energy index of plastic friction proposed by Oginski was determined. The modification of the Bland-Ford method consisted in the refusal to provide one-zone sliding along the deformation zone, i.e., we used the data of the usual rolling process in the presence of an forward slip. Calculations were performed on the technological parameters of rolling wire rod with a diameter of 6.5 mm of medium carbon steel in the conditions of wire block 210. In particular, we used the average values of force and moment of rolling for the campaign of the set of rolls of the block. All calculated values of friction indicators on the modules of the block received less than 0.15. According to the Blend-Ford method, the values of the calculated coefficients of friction decrease almost monotonically in the direction of rolling in the range of 0.143 - 0.093. Eklund-Zander ratios ranged from 0.117 in the first pass to 0.099 in the tenth. The energy index plastic friction of Oginsky's was obtained in the range of 0.091 - 0.045. From the analysis of the obtained data it follows that the Blend-Ford method provides the closest to the real values of the coefficient of friction. The values calculated by this method correspond to the capture conditions for a steady rolling process. Other reviewed methods give the value of the coefficient of friction less than half the angle of capture. For the practical use of data obtained on the basis of actual technological parameters of rolling a specific profile size of wire rod according to the Blend-Ford method, the distribution of friction coefficient values by block modules was obtained by regression depending on speed and temperature. Thus, it is established that the coefficient of friction during high-speed rolling in wire blocks can take values less than 0.15. According to the obtained data, it is necessary to take into account the decrease in the coefficient of friction of the steady process from the first to the last module, due to the increase in speed and rolling temperature.

An Experimental Investigation of Steel Surface Topography Transfer by Cold Rolling.

Automobile and household appliance panels require steel strips with extremely high-quality surfaces. Therefore, an in-depth study of the surface topography transfer of the steel strip during the rolling process is of considerable significance for improving product quality. In this study, the scale-invariant feature transform (SIFT) algorithm is used to realize the large-field stitching and the correspondence measurement of the surface topography of the roll and strip. The surface topography transfer mechanism and microconvex change law during cold rolling are revealed. Further analysis is conducted regarding the effects of different reduction rates and the initial surface topography of the roll on the formation of strip surface topography. Experimental results reveal that the furrow phenomenon occurs during the rolling process owing to the backward slip effect but is eliminated by the elastoplastic deformation of the matrix and the forward slip action. No furrow occurred along the width direction of the strip. With an increase in the rolling reduction rate, the transfer rate increases, and the strip surface topography is closer to the roll surface topography. Under the same rolling roughness condition and a small reduction rate (5%), the transfer degree increases remarkably with a rise in the reduction rate and increases slowly as the reduction rate continues to grow (from 7 to 10%). This study serves as a theoretical basis for the subsequent improvement of the surface quality of cold rolled strips.

Influence of Process Parameters on the Forward Slip of Cup during Roll Forming

The effect of friction coefficient, reduction of thickness, forming speed, roller diameter on the coefficient of forward slip at the rim of the roller during cup roll forming was studied by numerical simulation. The results show that during roll pre-forming, the friction coefficient and forming speed have little effect on the coefficient of forward slip, and the reduction of thickness and the diameter of the roller have a greater influence on the coefficient of forward slip; as the reduction of thickness increases, the coefficient of forward slip increases; as the roller diameter increases, the coefficient of forward slip increases first and then decreases. The coefficient of forward slip during the roll pre-forming of cup is much larger than that of roll forging. During roll shaping, the process parameters have little effect on the coefficient of forward slip and its value is close to zero, that is, the axial length of the roll shaped part is almost equal to the arc length of the roller rim. The accuracy of numerical simulation is verified by experiments, and the error between the numerical simulation and experiment is less than 1%.