Rolling Conditions Research Articles

Thermo-hydraulic performance of SCO2 in PCHE with NACA 4822 asymmetric airfoil fins under ocean rolling conditions

To enhance the heat transfer efficiency of a printed circuit heat exchanger (PCHE) under ocean rolling conditions, a fractal structure of the NACA 4822 asymmetric airfoil fins was proposed innovatively. This new configuration features two layers of channels: the upper is dedicated to hot CO2 while the lower is aimed for cold CO2. Notably, the asymmetric airfoil fin structure exhibits a remarkable improvement factor of heat transfer ranging from 1.0 to 3.5, accompanied by a friction factor ratio varying between 0.6 and 1.3, which signifies a dual benefit of reduced pressure drop and augmented heat transfer. Under rigorous analysis of the fractal-structured asymmetric airfoil fins in the PCHE, their performance is evaluated through varying rolling periods and angles. Our findings reveal that a rolling period of 2.0 s outperforms a rolling period of 4.0 s in terms of heat transfer performance. Specifically, at a rolling angle of 30°, the thermal performance soars by approximately 2.0 to 4.7 times, which indicates a positive correlation between a larger rolling angle and enhanced heat transfer. Intriguingly, the influence of the rolling angle on heat transfer performance eclipses that of the rolling period.

Investigation of the kinematics of turning a wheeled vehicle with a variable track

BACKGROUND: The trapezoidal lever mechanism used in the steering drive for turning steerable wheels to change the direction of movement of a wheeled vehicle does not fully meet the conditions for observing rolling wheels without slipping and conforming to the correct kinematics of rotation, which is especially evident when adjusting the track. AIMS: assessment of the degree of discrepancy between the actual kinematics of the turn and the kinematics of the correct turn when changing the track of the tractor. MATERIALS AND METHODS: Analytical methods were used in the work, which made it possible to obtain some computational dependencies, perform a numerical analysis of the curvilinear motion of a tractor with a variable track for different parameters of the steering trapezoid, and on this basis establish patterns between the geometric characteristics of the steering trapezoid and the kinematic parameters. RESULTS: Rational geometric characteristics of the steering trapezoid, which make it possible to obtain the kinematic parameters of rotation closest to the required ones, are set for the most commonly used value of the width of the pivot track. For the Belarus-80.1 tractor, it corresponds to 1.02 m. At the same time, for example, at an angle of rotation of the inner steerable wheel of 25°, the minimum turning radius realized by the steering trapezoid is 0.6521 m (10.44%), and at 40° by 0.2829m (9.27%) differs from their values obtained from the pure rolling condition. When changing the track width of the machine, there is a violation of the initial geometric characteristics of the trapezoid and the corresponding mismatch of the kinematic parameters of the rotation carried out by the steering trapezoid and by the correct rotation increases. A comparison of the minimum turning radii at an angle of 25° and a pivot track of 1.42 m showed an increase of 3.2340 m (35.83%), and at 40° — by 0.8956 m (20.21%). CONCLUSION: To ensure the correct turn, it is necessary to conduct a thorough theoretical analysis of the never mechanism of the steering trapezoid and improve its design on this basis.

Foam Rolling Intervention Improves Lactate Clearance After High-Intensity Exercise.

The acute effects of a foam rolling intervention on lactate clearance and the impaired executive function associated with fatigue after high-intensity exercise remain unclear. This study examined whether foam rolling is an effective tool for fatigue recovery. Eighteen healthy adults without consistent exercise habits participated in this study. Participants performed high-intensity exercises, and the post-exercise foam rolling intervention was compared to the control condition. Measurements included lactate, vigor/fatigue by the Profile of Mood States 2nd Edition, cognitive function (cognitive task performance), leg and body rating of perceived exertion pre- and post-exercise, and post-intervention. Blood lactate concentrations post-foam rolling intervention (-7.3 ± 3.0 mmol/L) were significantly reduced among all participants. Increased lactate clearance by foam rolling correlated with a faster recovery of executive function for those with greater lactate clearance. However, cognitive fatigue was not observed after high-intensity exercise (p = 0.086, r = 0.41). Lactate clearance was not significantly correlated with the rating of perceived exertion in the foam rolling condition. The rating of the perceived exertion decreased with increased lactate clearance for those with greater lactate clearance in the control condition (leg: r = 0.778; body: r = 0.669). In conclusion, foam rolling intervention may be effective for exhausting exercise recovery.

Effect of Rolling Process Parameters on Transverse Cracks on the Surface of Q345 Steel

This article examines the evolutionary behavior of transverse surface cracks in Q345 steel during the hot‐rolling process under various rolling conditions. “V”‐shaped cracks are prefabricated on the billet surface for laboratory hot‐rolling tests, and a corresponding rolling model is developed to validate its accuracy. The slab rolling model is established based on actual onsite rolling process parameters. The aim is to analyze the effects of different rolling conditions on the surface crack morphology and aspect ratio. The results indicate that variations in roll diameter (1400, 1300, and 1200 mm) influence crack propagation, with cracks unfolding earlier when the roll diameter is 1400 mm. At varying initial rolling temperatures (1300, 1200, and 1100 °C), cracks begin to unfold earlier at the highest temperature of 1300 °C. When examining different friction coefficients (0.4, 0.5, and 0.6), cracks unfold earlier at the highest coefficient of 0.6. Similarly, at different rolling speeds (3, 4, and 5 m s−1), cracks unfolded earlier at the highest speed of 5 m s−1. Analysis of changes in crack depth and aspect ratio during rolling shows that the initial few passes have a greater influence on crack depth and unfolding. In the later stages of rolling, cracks continue to unfold, though the depth shows minimal variation, and the aspect ratio tends to approach zero.

СОГЛАСОВАНИЕ ГЕОМЕТРИЧЕСКИХ ХАРАКТЕРИСТИК ФАКТИЧЕСКОГО ПОВОРОТА КОЛЁСНОЙ МАШИНЫ

Based on the above calculation scheme of controlled curvilinear motion of a wheeled vehicle, it was revealed that the steering trapezoid causes some discrepancy between the kinematics of real and correct rotation. It is established that when adjusting the track width of the machine, the kinematic mismatch between the optimal rolling conditions of the wheels increases, and, consequently, the calculated dependences of the parameters of the ideal turn will not give a satisfactory result when analyzing the actual turn. The minimum theoretical turning radius is taken as an estimated indicator of the turnability of a wheeled vehicle. The conclusion of a multifunctional analytical dependence for determining the theoretical minimum turning radius of a wheeled vehicle, the wheels of which are controlled by a steering trapezoid, is presented. The resulting formula includes the longitudinal base of the machine, the pin track, the angles of rotation of the inner and outer steerable wheels. A comparison of the calculation results according to the developed and known formulas is given, which confirmed the complete convergence. It was found that, for example, an increase in the pivot track of the machine by 0.2 m leads to an increase in the theoretical minimum radius of the actual turn by 16.5%, and the distance from the continuation of the rear axle to the instantaneous center of rotation by 45.07...98.02% when the angle of rotation of the inner steering wheel changes from 20° to 40°.

Assessment of former austenite structure in hot rolled steel in terms of its texture after martensitic transformation

Textures of medium carbon steel, hot rolled and then quenched, have been determined by Electron backscatter diffraction (EBSD). To ensure representativeness of results, a rather large treated scan covered about a thousand of prior grains, each containing several thousands of measurement points. Considering inter-phase orientation relationships peculiar to martensitic steels, textures of the high temperature phase (austenite) have been assessed in terms of the transformation textures. Thus, deformed and recrystallized states of austenite dependent on the rolling conditions can be distinguished. To verify EBSD data, martensite textures were measured by an independent method of EBSD whereas morphology of the prior grains was revealed by means of chemical etching.

Experimental study on flow boiling heat transfer in rigid-tail rib-channel under rolling motion conditions

This study proposes a novel addition of rigid filamentous tail structure at the trailing edge of the ribs to enhance the heat transfer performance of flow boiling in mini-channel under rolling conditions. The flow boiling heat transfer characteristics of Novec649 in both rib-channel and rigid-tail rib-channel are experimentally investigated. Heat flux, inlet flow velocity, rolling angle and rolling period are considered as the variable parameters, which are 50 – 300 kW·m−2, 0.3 – 0.9 m·s−1, 0 – 15°, 10 – 20 s, respectively. The experimental results show that the rigid-tail structure improves the heat transfer performance of the channels within the entire range of thermal parameters, while increasing the pressure drop at high heat flux and/or high velocity. Compared with rib-channel, the rigid-tail structure exhibits the strongest enhancement in flow boiling heat transfer performance under high heat flux of qeff = 300 kW·m−2 and high flow velocity of vin = 0.9 m·s−1, and the heat transfer coefficient can be increased by 6.93 % at most. And increasing the rolling angle or decreasing the rolling period will decrease the average wall temperature by a maximum of 1.94 °C and increase the heat transfer performance factor j by a maximum of 8 % at vin = 0.3 m·s−1, qeff = 200 – 300 kW·m−2 for the rigid-tail rib-channel. Furthermore, the addition of a rigid-tail structure helps maintain smaller bubble sizes and a more uniform distribution in the mainstream region of the two-phase flow.

Experimental study of boiling critical heat flux with low mass flux under motion condition in a wetted perimeter equivalent rod

The significance of floating nuclear power plant has recently surged as a viable solution for addressing ocean energy supply issues, while also meeting energy conservation and emission reduction goals. During the initial phase of nuclear reactor startup or in the event of a LOCA (Loss of Coolant Accident), the occurrence of critical heat flux (CHF) at exceptionally low mass flux in the core of floating nuclear power plant is a possibility. This underscores the importance of CHF safety characteristics of floating nuclear power plant. Despite this, there has been a noticeable absence of published experimental research on CHF under motion conditions with high operational parameters. To bridge this gap, CHF experiments were carried out on rod test sections under both static and motion conditions, employing the wetted perimeter equivalent design method. This study scrutinized the impact of system variables on CHF and evaluated the effectiveness of the design strategy based on the wetted perimeter equivalent method, using experimental data as a reference. Additionally, it elucidated the CHF mechanism and identified the penalty factor on CHF under conditions of inclination, rolling, and heaving, with the maximum penalty factor reaching up to 15%. The insights gained from this research are instrumental in guiding the CHF test scheme design under motion conditions and lay a foundational basis for the thermal design of floating nuclear power plant.

In Situ Chemical Mapping of the Thin-Film Lubricated Contact.

In this article, we propose a direct measurement of the distribution of two different chemical species in a thin-film lubricated contact under pure rolling conditions. The two chemical species were a carbonyl from an ester bond of a polyalphametacrylate (PAMA) polymer and an ether bond of a polyalphalycol (PAG) molecule, formulated in low-viscosity fluids using a mineral polyalphaolefin (PAO). A full chemical mapping of the lubricated contact region was provided thanks to the Bastet tribometer consisting of a ball-on-disk tribometer placed under a microscope coupled with an infrared spectrometer. By following the specific infrared stretching band of these two species in the inlet, contact, and cavitation areas, we showed how these molecules penetrate the high-pressure contact zone and participate in the film-formation.

Machine learning-driven intelligent tire wear detection system

Traditional methods detect wear by interpreting mathematical models and tire characteristics; however, these methods struggle to accurately reflect the actual rolling condition of the tire. In this study, we propose a machine learning-based tire wear detection module that can provide accurate results under tire test rig conditions. To develop this module, we designed three key components: integrated acceleration and PVDF sensors within the tire to capture vibration and deformation data; signal preprocessing algorithms to highlight multi-source signal differences under varying wear conditions; and deep learning algorithms to achieve precise tire wear grade identification. Experimental results demonstrate that, under different tire pressures, loads, speeds, and wear levels, the system can accurately identify tire wear grades with 99.99% accuracy by combining data from both sensors.

Investigating the evolution of U-10Mo fuel foil microstructures during multi-stage hot rolling using coupled potts model-finite element method simulations

In this work, we study the microstructural evolution of U-10Mo foils over multiple stages of hot-rolling and reheating using our previously validated method coupling the Kinetic Monte Carlo Potts Model with the finite element method. Hot rolling and reheating refine the U-10Mo foil microstructure, but the relationships between the foil microstructure and recrystallization behavior over multiple successive reductions have complex relationships with the rolling schedule that have not yet been well quantified. Simulations were employed to forecast the impact of hot rolling reduction per pass, grain size variations, and uranium carbide (UC) distribution on the Johnson Mehl Avrami Kolmogorov (JMAK) recrystallization kinetics of the U-10Mo alloy, as well as it's post-rolling grain growth kinetics. Initial homogenized grain sizes varying from 100 µm to 1 mm and UC volume fractions ranging from 0 to 2 vol% were parametrically evaluated as a part of this study. While some of our simulation results support the findings of our previous analysis for conditions of single-pass rolling and annealing, our extended analysis shows that the grain size within the as-cast and homogenized foil can lead to significant changes in the in the distribution of strain within the final microstructure, which can slow grain coarsening over the final anneal. The magnitude of the hot rolling reduction per pass had a similarly strong impact on the distribution of strain within the foil microstructure and its subsequent grain growth behavior. The implications of these results on U-10Mo fuel foil fabrication procedures are discussed.

Charging performance of a novel finned latent heat storage unit under sloshing

Latent heat storage (LHS) on ships using phase change materials (PCMs) is challenged by inefficient heat storage efficiency and susceptibility to sloshing conditions. To address this issue, this paper proposes a shell-and-tube LHS unit using innovative fins. The enthalpy-porosity approach is employed to study the melting characteristics of LHS units under sloshing, focusing on the effects of direction, frequency, and strength of sloshing conditions. An optimal fin configuration to enhance thermal storage performance under sloshing is proposed. The results indicate that the sloshing conditions effectively enhance the temperature uniformity and heat storage capacity of LHS units. Compared with the slosh-free condition, the full melting duration of PCMs in LHS units under roll and heave conditions is reduced by 20.9 % and 23.6 %, respectively. Moreover, the natural convection intensity and heat transfer uniformity under sloshing conditions increase significantly, improving the heat transport capacity in the late melting stage. Additionally, the heat storage capacity of LHS units improves with a decrease in sloshing frequency and an increase in sloshing strength; however, there is a limit to the performance enhancement gains. Interestingly, the arrangement of fins closest to the refractory zone effectively improves the heat transport in the later melting stage, resulting in a further 6.8% increase in the melting rate.

Effects of rolling at different temperatures and subsequent recovery annealing on the mechanical properties of a metastable carbon containing FeMnCoCr high-entropy alloy

Metallic materials or alloys consisting of single face-cubic centered (FCC) phases typically face difficulties in obtaining high strength without sacrificing ductility. The introduction of different crystalline defects via pre-straining and the activation of multiple deformation mechanisms have been shown to be effective in achieving superior strength–ductility synergy. In this work, we investigated the role of varying rolling conditions and subsequent annealing on the mechanical response in an established twinning- and transformation-induced plasticity dual phase high-entropy alloy (TWIP-TRIP-DP HEA). We found that all of the annealed samples exhibited similar nano-twinned structures. Furthermore, phase transformation from FCC γ to hexagonal close-packed (HCP) ε prevailed along the nano-twins under mechanical loading. With increasing rolling temperature, the phase stability of the matrix revealed a downward trend, resulting in a significant increase in TWIP/TRIP effects along with a prominent change in the deformation microstructure. Our study presented a simple and feasible strategy for manipulating mechanical performance by modulating the microstructural characteristics and associated deformation modes.

Research on the service life of bearings in the gearbox of rolling mill transmission system under non-steady lubrication state

A rolling bearing plays a key role in the gearbox of the cold rolling mill transmission system. As a result, the degradation and failure of bearings can lead to unplanned shutdowns of the entire rolling mill system. Since on-site cold rolling mills work usually in non-steady lubrication rolling conditions originating form variations of multiple parameters, the uncertainty affecting bearing performance in a cold rolling mill transmission system increases, making it more difficult to assess health status and predict the remaining service life of bearings, Therefore, by establishing a coupling model describing the relationship for the rolling mill and normal /faulty gearboxes under non steady rolling conditions, quantitatively studies the influence of various rolling parameters of a rolling mill on the fatigue service life of bearings in the gearbox of the rolling mill transmission system, and verify the effectiveness of linear cumulative damage theory for bearing fatigue service life through experiments and on-site bearing vibration data. The results indicate that as the thickness of the strip steel inlet, lubricant viscosity, and rolling speed increase, or the thickness of the strip steel outlet and rolling roll radius decrease, the service life of bearings gradually decreases. As the fluctuation amplitude of various rolling parameters in the cold rolling mill increases, the service life of bearings in the gearbox of the rolling mill transmission system gradually shortens. Moreover, when the rolling parameter value or fluctuation amplitude increases to a specific values, the remaining service life of bearings will sharply decrease. Under the same rolling conditions, the service life of bearings in gearboxes with faults decreases more significantly than that in normal gearboxes.

Numerical study on heat transfer characteristics of LBE cross flow tube bundle under rolling conditions

Combined with the neutron economy and good heat transfer performance, lead–bismuth fast reactor (LFR) has a larger prospect for marine applications. Helical coiled once-through tube steam generator (HCOTSG) is also a typical heat exchanger option for LFR. It is widely adopted in a variety of energy utilization fields, such as petrochemical industry. Study on Lead-bismuth eutectic (LBE) cross flow of tube bundle under moving conditions is necessary for obtaining the flow and heat transfer characteristics of LBE HCOTSG in marine conditions. A numerical method to simulate the heat transfer characteristic of LBE cross tube bundle flow under rolling conditions is proposed. The influence of the rolling conditions on the models with different tube arrangements are investigated. The temperature fluctuation curves with time and the time-averaged heat transfer characteristics are compared and analyzed. The results of the influence of rolling conditions under different working conditions and different tube bundle arrangements are obtained. The improvement ratio under inclined arrangement and staggered arrangement is more than 20 %, but the improvement under inline arrangement can only reach 10–15 %. Among the calculated models under different rolling conditions, the maximum heat transfer improvement reached 27.3 %. Besides, the circumferential temperature results under different conditions were also compared to analyze the influence of rolling conditions. This study may contribute to the application of LBE HCOTSG under marine conditions.

Role of scandium addition to microstructure, corrosion resistance, and mechanical properties of AA7085/ZrB2+Al2O3 composites

The effect of varying amounts of scandium (Sc) on the mechanical performance and corrosion resistance of aluminum alloy (AA7085) composites reinforced with Zirconium diboride (ZrB2) and Aluminum oxide (Al2O3) nanoparticles was investigated. The specimens were made using an in-situ process with varying amounts of Sc up to 0.5 wt%, and their microstructural behavior, corrosion, and mechanical properties were explored in detail. Phase structural analysis revealed the successful incorporation of ZrB2 and Al2O3 into the matrix through in-situ synthesis, ranging from 30 to 61.7 nm. In addition, HRTEM and XRD analysis displays the Al3Zr prominence observed with 0.1 wt% Sc content, transforming to Al3(Sc, Zr) in the 0.3 wt% Sc composite, and finally becoming Al3Sc with 0.5 wt% Sc. Corrosion analysis revealed that the 0.3 wt% Sc composite exhibited fine Al3(Sc, Zr) precipitate phases that enhanced corrosion properties. The Sc addition leads to a significant improvement in the mechanical properties of AA7085/ZrB2+Al2O3 composites. The ultimate tensile strength of 678 ± 5 MPa for 0.5 wt% Sc under the hot rolled and T6 aged condition was achieved. The optimum content of Sc in AA7085/ZrB2+Al2O3 composites has identified both corrosion and mechanical properties enhancement at 0.3 wt% and 0.5 wt%, respectively.

Joint Quality Assessment of Ultrasonic Metal Welded Parts by Fracture Surface Evaluation

In ultrasonic metal welding, low specific resistances and large joining surface cross-sections require the use of mechanical testing to quantify the joint quality. In this study, different quality features of ultrasonically welded joints made of pure copper sheet are investigated during the successive phases of joint formation. Two test series with different workpiece geometries are examined. It is shown that mechanical quality features such as shear and peel forces behave differently over the formation of the joint and are not transferable. As an alternative to these, laser scanning microscopy is used to record images of the fracture surface that describe the growth of the joint area during formation. The study finds that shear tensile force growth and joint area growth are non-linear and comparable, with optimized welds achieving joint areas of 30 mm2 out of 64 mm2 and 6 mm2 out of 16 mm2. Although overall quality increases with increasing welding time, the material strength in the joint zone decreases. Depending on the original rolling condition, between 43% and 59% of the original material strength can be identified as the joint strength. The automatic analysis of fracture images is a suitable alternative to mechanical testing for similar joints.

Determining critical Zn/Ca atomic ratio and its role in mechanical and corrosion properties of biodegradable Mg-Ca-Zn-Mn alloys

Mg-Ca-Zn-Mn alloys are promising for applications in biodegradable bone fixation devices. The Zn/Ca atomic ratio in the compositions of these alloys is important to their corrosion and mechanical properties. This paper investigated the Zn/Ca ratio using a phase-focused approach based on CALPHAD (CALculation of PHAse Diagrams) modeling and experimental validation. Six Mg-0.5Ca-xZn-0.5Mn (all wt.%) alloys were cast with x = 0.96, 1.15, 1.47, 1.69, 1.94, and 3.81 so that the Zn/Ca atomic ratio spanned from 1.18 to 4.66. The microstructure is studied in the as-cast, solution-treated, and as-rolled conditions. A critical ratio was determined to be 2.77, above which Mg2Ca phase can be suppressed in as-cast microstructure. In the solution-treated condition, a Zn/Ca ratio of less than 2.0 was required to dissolve the Ca2Mg6Zn3 phase. Alloys below 2.0 Zn/Ca were found to have yield strength of 300 MPa and a corrosion rate of 0.25 to 0.3 mg/cm2/day as measured by both weight loss and hydrogen evolution. In alloys above 2.0 Zn/Ca, the yield strength decreased to 280 MPa and the corrosion rate measured by weight-loss increased to 0.5 mg/cm2/day. Above the critical ratio, the yield strength was the highest at 347 MPa but a corrosion rate of 0.4 mg/cm2/day. The Zn/Ca region with the best combination of corrosion resistance and mechanical properties is between 1.18 and 1.8 (in rolled sheet condition), which provides important guidance for biomedical Mg-Ca-Zn alloy design and optimization.

An adapted two-step approach to simulate nonlinear vibrations of patterned tires rolling on a smooth surface

The tire/road noise is one of the major problems facing the tire industry due to the nuisance felt by the vehicle's driver and passengers. Moreover, it is expected in the coming years that this sound nuisance will be one of the main sources of vehicle noise due to the transition from combustion engine driven vehicles to electric vehicles. Tire manufacturers have therefore refined the design of their tire structures to find technological solutions to reduce traffic noise. Tire/road noise is also generated by various mechanisms which depend on different parameters such as the properties of the tire, road texture and driving conditions. This noise is partly caused by the acoustic radiation induced by the tire vibrations due to contacts with the road. The simulation and analysis of the tire's vibrations remains a challenge for the tire industry. Indeed, the simulation of the full dynamic response of a rolling patterned tire requires not only taking onto account various nonlinearities but also the multi-scale nature of the generated dynamic response. Contrary to a straightforward strategy that consists in using a time integrator to predict the multi-scale dynamic response, the strategy proposed in this study is based on a two-step approach to separate the dynamics occurring at different scales. The mathematical formulation of the proposed method is detailed as are the different modeling choices to simulate tire rolling under imposed load. The sensitivity of the tire's vibrations response is analyzed under different rolling conditions and with respect to certain key tire tread pattern parameters.

Study on numerical simulation and mitigation of parametric rolling in a container ship under head waves

To investigate the parametric rolling motion of container ships navigating in head seas, this study utilizes the unsteady RANS approach combined with dynamic overlapping grid technology to simulate parametric roll in a container ship under the coupled motions of roll, pitch, and heave. Initially, the model was validated against experimental results, demonstrating good agreement and thus confirming the reliability of the computational method. Furthermore, the paper investigates the impacts of the initial roll angle, encounter frequency, and the addition of bilge keels on parametric rolling. The research findings indicate that the initial angles of rolling impact the duration needed to attain a steady roll condition, yet they have minimal effect on the amplitude post-stabilization. The likelihood of parametric rolling arises when the frequency of encounters doubles that of the ship's inherent roll frequency. Furthermore, the likelihood of parametric rolling escalates when the wavelengths approach the length of the ship. Installing bilge keels markedly reduces the parametric rolling movement in vessels, and the occurrence of parametric rolling is also delayed.