Rolling Conditions Research Articles

Numerical Simulation of Passenger Evacuation Process for a Cruise Ship Considering Inclination and Rolling

This study focuses on a large-scale cruise ship as the subject of research, with a particular emphasis on conditions not covered in the MSC.1/Circ.1533 guidelines. The investigation explores the impact of specific motion states of the cruise ship, including rolling, heeling, and trimming, on passenger evacuation times. Based on the maritimeEXODUS tool, simulations were conducted to replicate the evacuation process in these unique scenarios. The results of the simulations highlight a significant correlation between the cruise ship’s motion state and evacuation time. Specifically, under inclination conditions, evacuation times were extended, with bow trimming leading to a notable increase in the time. This study underscores the importance of considering the motion state of a cruise ship in evacuation procedures, confirming the validity of the numerical simulation for studying large-scale cruise ship evacuations under inclination and rolling conditions. The findings contribute valuable insights for enhancing safety protocols and optimizing ship arrangements.

Numerical study on flow characteristics in the primary side of a once-through steam generator under ocean conditions

The flow characteristics of the primary side of the helical coil once-through steam generator (OTSG) have a significant impact on the safe operation of the reactor. Different from the land-based stationary working conditions, the flow of the primary side of the OTSG is influenced by sea waves and winds under ocean conditions. The rigid body motion model is used to calculate the flow of the primary side under different ocean conditions, including heeling, trimming, rolling, pitching, heaving, and combined conditions. The results show that under heeling and trimming conditions, the static pressure of the primary side is different from that under vertical conditions due to the influence of gravity, but its impact on the flow field is relatively small. Under rolling and pitching conditions, the mean flow velocity and pressure drop change periodically with the movement of the OTSG, and the smaller the sway angle, the smaller the variation amplitude of the mean flow velocity and pressure drop. Under the heaving condition, the variation amplitude of the mean flow velocity is greater than that under rolling and pitching conditions, and reverse flow occurs. Under the combined heaving and rolling condition, the mean flow velocity and pressure drop are influenced by the period and amplitude of both the two motions.

Investigation of Austempering Effect on Fatigue Crack Growth of AISI 4140 Steel

The compact tension (CT) and tensile specimens of the AISI 4140 steel in cold rolling condition (untreated steel) were austempered by immersing it into the salt bath at 362°C for 60 minutes. The tensile strength properties and the fatigue crack growth (FCG) resistance were performed to investigate the effect of the austempering process in AISI 4140 steel. A significant increase in the yield strength for austempered steel is about 8.7 % and the elastic strain energy increases by 55.7 %. Austempered steel's fatigue crack cycle is longer than that of untreated steel. Data of stress intensity factor range (ΔK, MPa.m1/2) and FCG rate (da/dN, m/cycle) was constructed in double log plot x-y axes for determining the materials constants m and C according to Paris’s law equation using a linear regression method. From the curve of ΔK versus da/dN, the constant m value for austempered steel (m = 3.45) shows better resistance than untreated steel (m = 3.77). On the other hand, the constant C value of 1.409×10-12 for austempered steel is one order magnitude higher than that of untreated steel (C = 4.151×10-13). The resistance of austempered steel against fatigue crack growth can be attributed to the formation of a bainite structure.

Experimental study on the surface defects of materials in bar rolling with a processing map applicable to billet-to-oval groove rolling

This paper proposes a systematic method for detecting surface defects (SDs) on specimens by performing a pilot hot (850°C–950°C) bar rolling test and suggests a processing map for billet-to-oval groove pass in bar rolling mills. Unlike previous studies, the specimens for the rolling test were prepared such that the billet surface became the surface of the specimens. A series of the rolling tests were performed at different temperature and area reduction ratios. Physical-chemical nondestructive testing was employed to detect SDs in the specimens before and after the rolling test. The depth of the SDs of the rolled specimens was measured using an optical microscope. The results revealed that the SDs depended both on the rolling parameters (temperature and reduction ratios) and the contact condition between the specimen and the roll groove during rolling, which is one of the characteristics of bar rolling that distinguishes it from flat rolling. The decrease in temperature caused an increase in the defect depth above the appropriate reduction ratio of 24.61% when the part of the specimen was in contact with the roll shoulder curve and the relief line of the oval roll groove. The proposed processing map presents a guiding path for operators in actual bar rolling mills to quickly determine a rolling condition (combination of temperature and reduction ratio), avoid SDs, and minimize defect depth within an acceptable range.

Hydrodynamic characteristics of the underwater continuous launching of vehicles under rolling conditions

Due to the influence of initial conditions such as the tethered velocity, vertically launched underwater vehicles generate large vortex structures in the wake after leaving the launch platform. This leads to an asymmetric surface pressure distribution on the second vehicles passing through the wake, adversely affecting their attitude. The rolling of the launch platform is another critical component of the above initial conditions. This study used the Realizable k−ε model, the volume-of-fluid multiphase flow model, and overlapping grid technology to numerically simulate the launch process of sequentially launched and retrogradely launched vehicles, both with and without rolling conditions. The study conducted a comparative analysis of the evolution patterns of wake vortex intensity, pressure distribution, and air–water phase distribution for the second underwater vehicles under different conditions after their launch. The results show that under rolling conditions, the wake vortex structure exhibits curling at both the vortex head and the vortex tail, with regions of greater vorticity shifting laterally. At certain moments, rolling and vorticity have similar effects on the surface pressure of the second vehicle. The presence of rolling accelerates the expansion and compression of gas pockets within the launch tube, reducing the disturbance of gas on the retrogradely launched first vehicle and changing the rolling angle of the vehicle. In the rolling conditions, the peak water hammer force on the inner wall of the platform increases and the forces acting on the inner wall of the tube show periodic variations.

Short-term ship roll motion prediction using the encoder–decoder Bi-LSTM with teacher forcing

The safety of maritime operations has become a paramount concern with the advancement of intelligent ships. Ship stability and safety are directly impacted by roll motion, making the prediction of short-term ship roll motion pivotal for assisting navigators in making timely adjustments and averting hazardous roll conditions. However, predicting ship roll motion poses challenges due to nonlinear dynamics. This study aims to predict short-term ship roll motion by leveraging the encoder–decoder structure of Bidirectional Long Short-Term Memory Networks (Bi-LSTM) with teacher forcing. The model is accomplished by employing an encoder–decoder structure to map input sequences to output sequences of varying lengths, and employing teacher forcing to enhance the network’s ability to extract information. To refine and analyze the prediction model, aspects such as the quantity of training data to guarantee model generalization, establishing apposite length relationships between input and output sequences, and assessing the model performance in various sea states are investigated. Additionally, comparative experiments assessing roll motion prediction for intervals of 10s, 30 s, 60 s, and 120 s are conducted to substantiate the necessity and effectiveness of the proposed network. The dataset originates from a commercial professional simulator developed by the Norwegian company Offshore Simulator Center AS (OSC).

Improvement of shape recovery by controlling the microstructure and mechanical properties in a thermomechanically-treated Fe-based alloy

In this research, the effects of thermomechanical treatment including heavy cold rolling and post-deformation annealing on the improvement of shape recovery in an Fe–9Ni–7Mn (at.%) martensitic alloy were investigated. Experimental results showed that the 80 % cold rolling produced a little fraction of strain-induced austenite phase in the martensitic matrix due to the strain concentration in the microstructure and the temperature rise under deformation. During post-deformation annealing at 590 °C in a dual phase (α+γ) region, a greater fraction of the austenite was introduced in the martensitic matrix such that its amount first increased by increasing the annealing time to 1.8 ks and then decreased at a more time of reversion. The microstructural evolution revealed that the austenite reversion under post-deformation annealing initially occurred by a shear nature at the early steps of reversion and then continued by diffusion. Tensile testing represented a good mixture of a relatively high ultimate tensile strength of ∼780 MPa and proper ductility of ∼8.5 % in the post-deformation annealed (PDA) sample for 0.9 ks. In addition, the shape memory properties were examined under the conditions of cold rolling and post-deformation annealing. The results showed a maximum shape recovery rate of ∼23 % for the cold rolled specimen which increased to ∼50 % after post-deformation annealing for 0.9 ks. The presence of a relatively high amount of retained austenite with proper stability and strength in the microstructure of the PDA sample for 0.9 ks was the reason for achieving the highest value of shape recovery.

Origin and evolution of false brinelling and fretting corrosion under rolling conditions

Rolling bearings working in oscillating applications often suffer from false brinelling and fretting corrosion that limit their service life. At present, the study of oscillation-induced failures is primarily dominated by a large number of sliding and bench tests. However, most of the previous work are not able to fully describe the two closely related but different failure mechanisms. In this study, the origin and evolution of the two failures are thoroughly investigated under strictly controlled oscillating rolling conditions. The results show that failure evolves from false brinelling to fretting corrosion under dry friction conditions regardless of the oscillation amplitude. This process is accompanied by a large area peeling and serious oxidation, and the oxygen content increases from 2.50 wt% to 21.22 wt%. Oxidation is a crucial factor in the evolution of false brinelling into fretting corrosion. However, the distribution of microwear and oxygen content depend on the oscillation amplitude. Under lubrication conditions, the friction coefficient (COF) is smaller in the initial stage and led to local slip or transient instability of rolling elements. Therefore, the size of the wear marks and COF increased and appeared to be larger than those under a dry friction condition. However, grease can separate the contact surfaces, only surface deformation owing to false brinelling and slight damage at the roughness level occurred. The evolution of false brinelling and fretting corrosion is also closely related to residual stress. False brinelling often occurrs with residual stress accomulation, meanwhile, the residual stress increases from 120 to 300 MPa. When peeling occurs, residual stress is released. The failure pattern transformed from false brinelling to fretting corrosion and is accompanied by oxidation. So far, none of investigation is able to show satisfactory evolution of oscillating-induced failures, this study may contribute to more scientific understanding of rolling bearings against long-run reciprocating oscillating wear.

Research on AGC Nonlinear Compensation Control for Electro-Hydraulic Servo Pump Control of a Lithium Battery Pole Strip Mill

Electrode roll forming involves rolling a battery electrode into a preset thickness using a hydraulic roll gap thickness automatic control system (hydraulic AGC for short). The pump-controlled AGC is a highly nonlinear servo system, which is a combination of mechanical, hydraulic and electronic control disciplines; thus, as a new technology, it still faces many challenges in the field of pole plate rolling. In this paper, electro-hydraulic servo pump-controlled AGC technology is replaced by electro-hydraulic servo valve-controlled AGC technology. With pump-controlled AGC high-precision thickness control as the research objective, the fuzzy control method is selected to deal with complex nonlinear systems based on pump-controlled AGC nonlinear stiffness characteristics and nonlinear transmission characteristics. A characteristic compensation control strategy is proposed. At the same time, considering the load fluctuation caused by the uneven thickness of the electrode plate under the intermittent coating rolling condition of a lithium battery, the fuzzy internal model (IMC) compensation control strategy was proposed to compensate the structural characteristics of the electrode plate rolling. Comparative experiments show that the position control accuracy of the pump-controlled AGC system can be improved significantly by using a fuzzy IMC compensation control strategy. The steady-state accuracy of the slope signal can reach ±0.7 μm, and the position-following accuracy of the sinusoidal signal can reach ±1.8 μm. In addition, this study will assist technological upgrades to lithium battery electrode roll forming and fixed-roll-gap rolling, laying a theoretical foundation for the promotion of pump control technology in the field of electrode rolling.

Analysis of coolant flow distribution characteristics at core inlet of small pressurized water reactor under rolling condition

The flow distribution characteristics at core inlet directly determines the thermal and hydraulic characteristics in the core, and it is closely related to the safety of nuclear reactor. The primary coolant is subjected to additional inertial force in ocean motion, which influence the flow distribution characteristics at core inlet. In the present paper, numerical simulation method is adopted to analyze the coolant flow distribution characteristics at core inlet of the Reactor Pressure Vessel (RPV) of a Small Reactor under rolling condition. Then the results of the flow distribution characteristics were compared with those under steady state. The results show the variation range of flow distribution factors in each channel under rolling condition is within 5%. And the uneven distribution of coolant at the core inlet increases with the increase of rolling amplitude, and decrease with the rolling period in short period. Standard deviation of flow distribution factor at the core inlet changes little under rolling condition, which indicates the flow distribution at the core inlet keeps good uniformity.

A new method for selecting and evaluating the hyperelastic model of tread rubber material under rolling contact condition

The selection and evaluation of the hyperelastic model of tread rubber material were of great value and significance to the clarification and application of the mechanical properties of tread rubber material. In this article, a non-contact tread rubber material rolling test bench was established. The improved digital image correlation method was used to calculate the strain rate distribution of the marked point under different test conditions. Combined with the stress distribution of the marked point, the rolling dynamic stress-strain characteristics of tread rubber material were obtained. Based on rubber material models under different tensile test modes, the parameter inversion identification of the hyperelastic model was completed, and the influence of the tensile test mode on the parameter inversion of the tread rubber hyperelastic model was revealed. A new method for selecting and evaluating the hyperelastic model of tread rubber material under rolling contact conditions was proposed. The selection criterion for the hyperelastic model of tread rubber material was developed under different rolling conditions. The experimental and analytical results show that the nonlinear degree of the constitutive relation of the hyperelastic model decreased with the increase in rolling speed. Compared with hyperelastic models under different tensile modes, the fitting error of the Yeoh model was less than 3%, and the overall fitting error of the Yeoh model was less than 2%. Therefore, the Yeoh model had better stability and accuracy and was more suitable for describing the rolling mechanical properties of tread rubber under rolling contact conditions.

Preparation of AlMgSi1 (6082) aluminum alloy for the study of mechanical and physico-chemical properties in the rolling process

The study is devoted to the preparation of the AlMgSi1 (6082) aluminum alloy for the study of its mechanical and physico-chemical properties under rolling conditions. The purpose of the work is to develop a methodology for preparing an alloy that provides reproducible analysis of its properties. The main directions include the study of rheological and plastic properties of the material, as well as thermal effects during deformation. The scientific significance of the work lies in the analysis of the effect of heat treatment and deformation parameters on the plastic fluidity and corrosion resistance of the alloy. The practical significance lies in improving the quality of materials for various industrial applications. The methodology included experiments with heat treatment and rolling, analysis of the microstructure and mechanical properties of the alloy. The tests were carried out on samples at different temperatures and strain rates using the STD 812 torsion plastomer. The results showed that the plasticizing stress of the alloy increases with deformation at low temperatures and decreases at high temperatures. The conclusions confirm the significant influence of temperature and strain rate on the properties of the alloy.

The influence of random factors on the estimation of the speed and time of rolling cuts from sorting humps

The main direction of increasing efficiency and safety of the work of sorting humps is the management automation of breaking-up of trains. The difficulty of solving this problem is due to the fact that it is solved in the absence of accurate information about the running characteristics of the cars, the parameters of their routes of rolling and environmental conditions. In addition to this, car retarders implement given modes with errors. The purpose of this study is to assess the influence of various random factors on the indicators of cars rolling from the sorting humps. The research was carried out using methods of simulation modeling, planning of factorial experiments and statistical analysis. As a result, it was established that the main factors affecting the mean square deviation of the time of the cars rolling are the distance of unregulated rolling and the specified speed of the cut leaving the car retarders. The research results make it possible to improve algorithms for determining braking modes for retarders in the absence of accurate information to solve the problem.

Experimental and numerical investigation of flow dynamics in an upward bubbly flow in a tube undergoing oscillating rolling motion

Offshore nuclear power plants are characterized by a potential oscillatory motion depending on ocean waves. Investigating the local flow behavior in a system undergoing oscillating motion is necessary. In particular, because the local void fraction near the heating element surface significantly affects the nucleating boiling heat transfer and critical heat flux, understanding the dynamic behavior of the local void fraction is very important. Therefore, in this study, as an essential first step in predicting boiling heat transfer and departure from nucleate boiling in offshore nuclear reactors, the dynamic behavior of air–water bubbly flows has been experimentally and numerically investigated in a tube under oscillatory rolling conditions. An optical fiber Doppler probe was used to measure the local bubble parameters. The effects of the rolling period on the void fraction distributions, bubble sizes, and bubble velocities were insignificant. However, the rolling amplitude effect was significant. The void fraction was the highest at the downward-facing wall when the tube was at its maximum tilt. Moreover, the local water velocity became the highest when the tube returned to near vertical because of the combined effect of gravity and Euler force. These findings provide insights into understanding the characteristics of bubbly flow in a rolling tube.

DEVELOPMENT OF METHODS FOR SIMULATION OF RAILCARS ROLLING FROM SORTING HUMPS

Purpose. The purpose of this article is to carry out a historical analysis of the development of methods for simulation of railcars rolling from sorting humps and to determine directions for their improvement in order to solve the problems facing the railway transport of Ukraine today. Methodology. The research was carried out on the basis of the processing of literary sources of the library of the Ukrainian State University of Science and Technology, as well as scientometric databases Scopus and Google Scholar. Findings. The origin of the methods for simulation of railcars rolling from sorting humps took place at the beginning of the 20th century, when they were separated from the methods of traction calculations. Until the middle of the 20th century, the simulation of the railcars rolling was carried out in order to solve the problems of designing sorting humps. This period is characterized by the simulation of the rolling of individual curs under known conditions. The complication of the simulation methods of the sorting humps operation is connected with the tasks of automating the control of the trains breaking-up. For this purpose, the tasks of establishing the laws and parameters of the distribution of random resistance values acting on the cuts, taking into account changes in the longitudinal profile of the track under the cuts, modeling the operation of brake retarders and their control systems, etc., were solved. Originality. The scientific novelty of the work lies in the fact that, on the basis of a historical analysis of the development of methods for simulation of railcars rolling from sorting humps, the connections between the working conditions of railway transport and the methods of modeling rolling processes are established. Practical value. The practical value of the results lies in the fact that they indicate the need to develop methods development of methods for simulation of railcars rolling from sorting humps in conditions of inaccurate information about their running characteristics and rolling conditions. This will make it possible to increase the efficiency of the sorting humps operation without significant capital investments in their control systems.

Formation and effect of intermetallic compounds in the interface of copper/aluminum composites under rolling conditions

Rolling and annealing are common composite processes of Copper/Aluminum composites (Cu/Al), but the formation of intermetallic compounds (IMCs) at Cu/Al interfaces and their relationship with processing conditions still lack a nanoscale understanding. Here, we use molecular dynamics (MD) method to simulate the formation of IMCs at Cu/Al interface under different rolling and annealing process parameters with their formation mechanisms quantitatively analyzed. XRD, RDF and potential energy analysis show that rolling promotes the formation of interfacial IMCs, because copper and aluminum atoms tend to diffuse into each other at the interface and combine to form IMCs during rolling. The effects of different size ratios of copper to aluminum and annealing on IMCs are also evaluated. By studying the equivalent phonon thermal conductivity of the interfacial layer and shear strength, it is shown that IMCs enhances interfacial phonon heat transfer, but reduce the interfacial shear strength due to their brittle and hard properties. In addition, the rolling and annealing processes are able to change the dislocation density, thereby affecting the phonon scattering and shear strength of Cu/Al. These results are expected to guide improved directions for the process optimization of high-performance Cu/Al.

Numerical simulation of flow and heat transfer in fuel assembly of floating nuclear power platform

ABSTRACT Floating nuclear power platform (FNPP), unlike onshore nuclear power plants, is subjected to periodic rolling loads at sea. These loads will have a more obvious impact on the flow characteristics and temperature distribution inside the fuel assembly (FA). This paper first establishes a refined model of the 7 × 7 core fuel assembly. Then, the flow and heat transfer characteristics of assembly with pure fuel bundles and assembly with guide tubes are analyzed using a segmented grid partitioning method, taking into consideration both accuracy and efficiency in calculation. Finally, the flow and heat transfer characteristics inside the assembly with guide tubes under rolling conditions are simulated and calculated, and compared with the previous simulation results. The calculation results show that the flow and heat transfer characteristics of the assembly with guide tubes are quite different from those of the pure fuel rod bundle assembly, and the rolling environment has obvious adverse effects on the flow field characteristics and temperature distribution in the fuel assembly of the offshore reactor, which must be considered in the design and construction of the floating nuclear power platform. The research results have significant reference value for the design and optimization of floating nuclear power platform assemblies under rolling conditions.

Full-field contact dynamic mechanical properties of tread rubber material under rolling and slippery conditions based on digital image correlation

The dynamic mechanical properties of rolling tire on special road surface were closely related to the vehicle’s handling stability, driving safety and braking effectiveness. The tire tread rubber material was the only contact part of the vehicle with the road surface, so the strain distribution characteristics of tread rubber material within the contact patch of rolling tire on thin water film pavement played a crucial role in the mechanical characteristics of vehicle. In this paper, a non-contact tire tread rubber rolling mechanical test system was developed. The improved digital image correlation (DIC) method was used to obtain the full-field strain distribution of tread rubber blocks. The effects of load and velocity on the strain rate of the marked points, the full-field strain distribution in the region of interest and rolling resistance were investigated under thin water film pavement. The experimental results were compared with dry condition to analyze the effect of water film on the rolling dynamic characteristics. The results showed that the strain rate increased first and then fluctuated under the action of thin water film. With the increase of speed and load, the full-field strain distribution of tread rubber contact patch was gradually occupied by low strain zone. The change rate of rolling resistance firstly increased and then decreased with the increase of rotational speed.

Mechanism of Tire / Road Noise Emission and Reduction Technology

The significant noise reduction has been brought by recent electrification of power train of vehicles. More concern about impact on the health due to the environmental noise, especially road traffic noise, requires further reduction of tire / road noise emission caused by the contact between the tire and road surface. The tire / road noise emission mechanism can be described by three different systems such as the excitation, the response, and the propagation. The excitation is composed of the road excitation, the tread excitation, the air-pumping and the friction. The tire structural response and the acoustic response in the void formed inside contact patch are respectively excited by those sources. The recent technology development in numerical analysis and test methods allow us to investigate the detailed behavior of tire in various rolling condition. The present article gives progresses on the mechanism understanding of tire / road noise emission and some reduction technologies.

Design and Properties of Hot Rolled Tough Carbide Free Bainitic Steels

Carbide free bainitic microstructures of steels in hot rolled condition have high potential for automotive and structural applications, where both high elongation and toughness at a high strength level are needed. However, achieving a combination of these properties remains a challenge due to difficulties in ensuring a high stability of retained austenite while maintaining industrial processability. Therefore, an attempt has been made in this work to achieve combined high toughness and high elongation in hot rolled carbide free bainitic steels.