Rolling Conditions Research Articles

STUDI LITERATUR: PERFORMA MODEL KAPAL BENTUK MONOHULL, KATAMARAN DAN TRIMARAN

Along development of technology from time to time, makes the shipping sector have experienced development. This made the Indonesian geverment place the maritime sector into a priority program in national development. The development of ships occur from various scopes, this things takes the development of ships in terms of the number of hulls such as single hull (monohull), double hull (catamaran), and with three hulls (trimaran). This research uses a literature method that will analyze the results of previous research related to the ship’s performance. The purpose of this research to determine the best performance between ships with monohull, catamaran and also trimaran forms. The results of this research are expected to be a basic reference for selecting the ship’s hull to be fabricated in the future, whether in terms of tourism, military, etc. the results of this research indicate in terms of stability ships with trimaran hulls have good stability among others. This is because trimaran ships have a larger surface area than monohull and catamaran. With the ratio of the width and height of the ship makes the catamaran have good stability. In terms of resistance, catamaran ships have the smallest resistance than others, but this influenced by the demihull distance factor which makes the waves formed from each hull not collide with each other. In terms of seakeeping, the catamaran is the best in case of heaving, rolling and pitching conditions from all heading angles.

Acute Effects of Static Stretching Combined with Vibration and Nonvibration Foam Rolling on the Cardiovascular Responses and Functional Fitness of Older Women with Prehypertension.

Simple SummaryThirty-seven percent of the US adult population have prehypertension, and a quarter to half of these over 65 years of age progress to hypertension in four years. Along with healthy diet, exercise or physical activity is one of the critical lifestyle factors for this population. General exercise recommendation or prescription to individuals who have cardiovascular risks is provided by organizations such as ACSM and AHA, but more detailed information and research are still needed. As the first component of any exercise program, finding the proper warm-up routine is important. We aimed to examine the acute immediate effects of three different warm-up protocols on cardiovascular responses and functional fitness testing in older women with prehypertension. Thirteen qualified subjects went through three protocols (static stretching with and without foam rolling, and stretching with vibration rolling) in three different sessions. Blood pressure was not altered only in the static stretching with foam rolling condition. Interestingly, adding the vibration component to the stretching increased the upper body flexibility and stretching. We therefore suggest the combination of static stretching with foam rolling as the safe and effective protocol for older women with prehypertension.We compared the effects of three warm-up protocols (static stretching (SS), static stretching with vibration foam rolling (SS + VFR), and static stretching with nonvibration foam rolling (SS + FR) on the blood pressure and functional fitness performance in older women with prehypertension. Thirteen older women went through different protocols in separate visits, and their systolic (SBP) and diastolic (DBP) blood pressure, heart rate, mean arterial pressure, brachial pulse pressure (BPP), functional fitness test (back scratch (BS), chair-sit-and-reach, 30 s arm curl (AC), 30 s chair stand, 2 min step, 8-foot up and go), and single-leg standing balance (SLB) were recorded. The SBP and BPP were significantly higher after SS and SS + VFR than after SS + FR. Both SS + FR and SS + VFR significantly improved the 2 min step, when compared with SS. Additionally, SS + VFR significantly improved the BS and AC performance. However, compared with SS and SS + FR, SS + VFR significantly reduced the SLB performance. Therefore, SS + FR may be a better warm-up protocol for older women in maintaining blood pressure. On the other hand, even though SS + VFR induced superior shoulder flexibility, aerobic endurance, and arm strength, it could impair balance.

Adaptive (Cr,Al)N+Mo:Sg Coating for Highly‐Stressed Contacts under Dry Rolling‐Sliding Conditions

Highly-stressed rolling-sliding contacts under fluid-free lubrication as found in ultralightweight gear applications require effective friction and wear reduction. Promising approaches are PVD deposited Mo:S-modified nitride coatings (Cr,Al)N+Mo:Sg and Zr modified diamond-like-carbon coatings ZrCg that provide transfer film-based self-lubrication. In this study, the self-lubrication mechanism of both systems is tribologically tested on a twin-disk tribometer and physiochemically analyzed by secondary electron microscopy and Raman spectroscopy. MoS2 lacquer provides the reference. Results reveal lowest friction and stable self-lubrication through in-situ MoS2- and MoxOy-rich transfer films from (Cr,Al)N+Mo:Sg on the steel counter surfaces. High pressures and pure rolling conditions favor the transfer film formation.

Effect of in-situ layer-by-layer rolling on the microstructure, mechanical properties, and corrosion resistance of a directed energy deposited 316L stainless steel

In this study a novel micro-rolling set-up was installed on a directed energy deposition additive manufacturing system to achieve in-situ grain refinement and porosity closure. A 316 L stainless steel was investigated and it was found that even low micro-rolling loads were capable of increasing the part density from 99.7% to 99.98%. Martensitic transformations as a result of micro-rolling were not detected. Additionally, using a combination of X-ray diffraction and optical, scanning, and transmission electron microscopy techniques, it was found that micro-rolling resulted in a finer internal grain substructure, twinning, an increase in dislocation density, a reduction of grain sizes, a refinement of the cellular structures, and a randomization of the crystallographic orientation distribution. This resulted in an increase in hardness by up to ~ 23% and in yield strength by up to ~ 31%. More importantly, due to pore closure, improved mechanical properties were achieved without compromising ductility. As the segregation of solute elements to cell boundaries was also not affected by micro-rolling, the excellent corrosion resistance of the alloy was generally retained. Thus, this approach allows the fabrication of denser, stronger and harder 316 L parts without the need for additional post-processing steps such as hot isostatic pressing or thermo-mechanical treatments, while also maintaining ductility and corrosion performance. • An in-situ rolling apparatus was built into a directed energy deposition system. • Four rolling conditions were studied for the fabrication of 316 L stainless steel. • Porosity closure was achieved even with the lowest applied rolling load. • Higher rolling loads resulted in greater grain refinement and hardness. • This process minimizes the need for additional post-processing steps.

Facilitating the occurrence of dynamic recrystallization in plain extra low-carbon steel by warm asymmetric rolling

The occurrence of dynamic recrystallization in warm rolling of plain extra-low carbon steel was examined by applying 75% thickness reduction in a single pass. The investigated temperature range was ambient to 700 °C. Results show apparently dynamic recrystallization remains absent in symmetric rolling below 600 °C. Nevertheless, dynamic recrystallization not only just occurs but accelerates as the condition of warm rolling changed from symmetric to asymmetric condition. The analysis of grain internal disorientations and geometrically necessary dislocation densities by High-angular Resolution on-axis Transmission Kikuchi Diffraction (HR-TKD) allowed to identify the type of dynamic recrystallization and its evolution through the warm temperature range. New grains formed by either continuous or discontinuous dynamic recrystallization are preferentially orientated according a typical shear texture up to 600 °C in the case of asymmetric rolling. Above 600 °C, dynamically recrystallized grains produce restrengthening in the rolling texture as well as in the overall texture.

Numerical investigation of flow characteristics in a rearing tank aboard an aquaculture vessel

The mobile aquaculture vessel is expected to be a sustainable way for future nutritious food due to its mobility, potential production rates and environment preservation. The flow field in fish rearing tanks aboard the vessel is a prerequisite for fish welfare. In this paper, the flow field characteristics in an aquaculture tank was numerically investigated. The fish fitting guaranteed rate (FFGR) based on the statistical cumulative distribution probability is presented and used to analyze water flow. A typical rolling condition of an aquaculture tank from the analyses of response amplitude operator (RAO) was used for the flow field analysis. The wavelet and fast Fourier transformation on the mass averaged mean kinetic energy reveals a steady-state of the rolling flow condition after 100 oscillating periods. Statistical analysis on the water velocity indicates that the period-averaged FFGR increases with velocity. Based on the FFGR, the flow field of aquaculture vessel in rolling oscillations are evaluated for six fish species, including Atlantic salmon and Pseudosciaena crocea.

Comparison and optimization of heat transfer models in reactor channel under the rolling condition

The convective heat transfer characteristics of reactor system under ocean condition affect the reliability and safety of its operation. The modification of system code applied to marine reactor mainly focuses on momentum equation and geometry position, but rare of improvement on heat transfer model. Therefore in this paper, a series of single-phase flow experiments in circular and rectangular channels under ocean motion are summarized. Then the related heat transfer models are analyzed and compared with experiment data. The results show that the existing models have limited application in different intervals of Reynolds Number. In order to optimize the heat transfer model, time average and pulsation amplitude of Nusselt number is taken into consideration and modified based on mechanism and best fit of existing experiments.

Reduction of Structure-Borne Tyre/Road Noise through Rubber Resonant Metamaterials in Tyres

<div class="section abstract"><div class="htmlview paragraph">This paper demonstrates the application of a resonant metamaterial concept to tyres in order to reduce structure-borne tyre/road noise. Special attention is given to the frequency range around 220Hz, containing the first acoustic tyre resonances. These resonances are known to transmit high forces to the wheel-knuckle, leading to structural energy propagating into the vehicle’s body and, consequently, causing a tonal noise issue in the vehicle compartment. By adding recycled rubber resonant elements to the inner liner of the tyre, structural stop band behaviour is achieved in the frequency band of interest. Hence, structural vibrations in the tyre are reduced, resulting in a reduction of the excitation of the first acoustic tyre resonances and, consequently, a mitigation of the transmitted forces to the wheel-knuckle. First, the stop band behaviour is designed via unit cell modelling of a section of a tyre mock-up that only accounts for its structural behaviour. Next, the resonant elements are produced and added to the tyre. Finally, an experimental campaign is carried out to verify the performance of resonant metamaterials in static and rolling conditions.</div></div>

Computerized design, simulation of meshing and stress analysis of pure rolling internal helical gear drives with combined tooth profiles

The computerized design of non-generated pure rolling internal helical gear drives with combined transverse tooth profiles based on the active design of the meshing line function is presented. The application of different combinations of curves, namely circular arcs and involutes, to form the gear active tooth profiles is discussed. The parametric equations for tooth surfaces and the basic design parameters and equations of geometric sizing are proposed. The meshing performance and mechanical behavior are studied in terms of the contact patterns, maximum contact and bending stresses and peak-to-peak level of loaded transmission errors compared with a design of internal helical gear drive with corrected fillet. The combination of a circular arc and an involute connected at the pitch point to form the active tooth profile for both the pinion and the internal gear shows reduced maximum contact and bending stresses and lower peak-to-peak level of the loaded function of transmission errors. The proposed design of combined tooth profiles will contribute to lower the noise and vibration of the proposed gear drives, increase the endurance and life of the gear drive, and lower the heat generation due to pure rolling conditions of the achieved bearing contact.

Determination of Particular Relative Reduction in Cold Rolling of Thin and Extra Thin Strips to Implement the Process with the Least Force

Introduction. It has been theoretically established and experimentally confirmed that the elastic deformations of rolls and strips in cold rolling have a significant and, in the case of thin rod rolling, a crucial effect on all process parameters.Problem Statement. The influence of the elastic-plastic interaction of a thin strip with rolls, the tension, the temperature and rate of deformation, and the strength of strip material shall be taken into account for developing a modern theory of longitudinal cold rolling.Purpose. Modeling and forecasting the parameters of cold rolling of thin and extra thin strips.Materials and Methods. To solve this problem, the conditions of rolling strips made of 08kp steel with different degrees of preliminary metal hardening, which reflected the features and regularities of hardening the strip material in the multicellular state line, have been modeled. The partial relative reductions vary within 0.02—0.35,with the initial data corresponding to the most characteristic conditions of cold rolling of thin and extra thin steel strips on operating mills taken.Results. The quantitative data on the influence of the strip thickness, at the entrance to the deformation zone, partial and preliminary relative reduction during cold rolling on the process conditions with the least force. For the first time, the conditions and range of partial relative reductions for the cold rolling process of thin and extra thin strips with the least force have been determined. It has been established that in the case of cold rolling of thin and extra thin strips made of unriveted and pre-hardened steel, varying partial relative reductions within the rangefrom 0.1 to 0.30—0.35 provides the realization of process with the least force.Conclusions. The implementation of cold rolling process with the least force is advantageous in terms of energy saving and manufacturability, as it allows reducing the specific consumption of electricity and expanding the range of cold rolling mills for smaller thicknesses of rolling strips and indicates the need to determine conditionsfor such a process.

Flow stress stabilization of Zn-Cu-Mn-Mg alloys using thermomechanical processing

Zinc-based alloys are potential candidates for bioabsorbable metallic devices due to their application-appropriate corrosion rates and biocompatibility. However, strain softening and rate sensitivity in tensile testing remain as challenges for their use in load bearing applications. In this study, three different Zn-xCu-yMn-0.05Mg (x = 0.5, 1.0 wt%, y = 0.4, 0.6 wt%) alloys were formulated and their microstructure and tensile properties in the room-temperature rolled condition were characterized. Additionally, the effect of short-time annealing at 320 °C on the strain softening and strain rate sensitivity of alloys was studied. The results indicate that dissolution of secondary phases and grain coarsening lead to the suppression of strain softening and strain rate sensitivity. The evolution of microstructure during the room-temperature tensile testing indicates that dynamic recrystallization is responsible for strain softening and can be eliminated by tuning the fraction of secondary phases and underlying grain size. The formulated alloys are not susceptible to natural aging and show good thermal stability during aging up to 200 °C for 60 h due to the pinning effect of MnZn13 precipitates on the grain boundaries.

Enhancement of mechanical properties of a novel single phase Ni1.5FeCrCu0.5 HEA through cold rolling and subsequent annealing

A novel single-phase Ni1.5FeCrCu0.5 High entropy alloy was fabricated by Vacuum Arc Remelting (VAR). The evolution of the alloy's microstructures, crystallographic texture, and mechanical behavior was investigated in as-cast, cold rolling (90% thickness reduction), and annealing (1000 °C for 1 h) conditions. Microstructural evolution demonstrated that the dendritic structure of the as-cast HEA was associated with a very small amount of Cu element segregation, which changed to tense elongated grains after cold rolling. Cold rolling resulted in development of Goss {110}<001>, Goss/Brass {110}<111> and Brass {110}<112> as the major texture components. After annealing, the complete recrystallization structure appeared in an average grain size of 3 μm, and deformation texture components remained. The results indicated the cold rolling led to a significant strengthening of the alloy; its yield strength and ultimate tensile strength of the alloy reached 1220 and 1574 MPa, which was 5 and 3.5 times the as-cast conditions (yield strength: 236 MPa and ultimate tensile strength: 454 MPa), respectively. However, the elongation was reduced to 5%. Eventually, the elongation in the recrystallization state increased approximately seven times.

Effects of rolling motion on transient flow behaviors of gas-liquid two-phase flow in horizontal pipes

The investigation of transient flow behaviors of gas-liquid two-phase flow under ocean conditions is vital to the application of gas-liquid transport in ocean engineering area. In this paper, the gas-liquid two-phase flow numerical model of rolling horizontal pipe is established based on CFD code combined with user-defined functions (UDF). The three-dimensional rolling flow fields are simulated using the volume of fluid (VOF) model, RNG k−ε turbulence model and additional inertia force method. First, the simulation results are compared with the experimental data, which revealed a reasonable agreement. Then, the variation in transient flow behaviors by horizontal pipe (L = 2.0 m, D = 0.035 m) with varying rolling conditions (θm = 2°-6°, T = 0.5–4.0 s) and flow velocities (jG = 0.1–10.0 m/s, jL = 0.1–0.5 m/s) are investigated. The results showed that the rolling motion caused agglomeration of dispersed bubbles and gas slugs into a continuous gas column, increased the cross-sectional void fraction significantly. The variation of additional inertial force and pressure drop increased with the increase of rolling angle and the decrease of the rolling period. Compared with the rolling angle, the transient flow behaviors are more sensitive to the rolling period. In addition, as the initial gas volume fraction increased, the effects of rolling motion on the transient flow behaviors decreased gradually. These qualitative conclusions may serve as a reference for gas-liquid transport simulations under rolling conditions.

Influence of Strain Rate Sensitivity on Cube Texture Evolution in Aluminium Alloys

The influence of strain rate sensitivity on development of Cube texture and on the morphology of Cube-oriented grains is often neglected in simulations approaches. Therefore, crystal plasticity simulations and experiments were performed up to 73 pct of thickness reduction for cold rolling on Al 6016. It is found, that low values of strain rate sensitivity promote Cube grains fragmentation and avoid formation of transition bands already at 50 to 55 pct thickness reduction. High values of strain-rate sensitivity cause formation of Cube transition bands leaving thin Cube grains in the microstructure and delay their fragmentation. Other texture components are affected by changes in strain rate sensitivity as well. The Copper volume fraction in the final texture diminishes as the strain rate sensitivity decreases, while Brass and S components of the beta fiber show a moderately higher volume fraction when the strain rate sensitivity increases. The final volume fraction of Goss is highest when the strain rate sensitivity is 10−2 but low if the strain rate sensitivity is 10−3 or raises up to 10−1. Recrystallization texture components (P, Q) are not affected by strain rate sensitivity, while the invGoss fraction decreases for high values of strain rate sensitivity. The results found in cold rolling crystal plasticity simulations were compared with experimentally determined Cube distribution and texture components obtained through thickness for Al6016 rolled at 80 m/min and 600 m/min. Further crystal plasticity simulations were performed to predict the influence of strain rate sensitivity during several hot rolling conditions where activity of non-octahedral slip systems was included in the simulations. During hot rolling, high values of strain rate sensitivity contribute to Cube stabilization and promote formation of Copper texture and delay Brass and S.

Pore closure in thick aluminum plate: From industrial hot rolling to individual pore observation

Pores are often present in large aluminum ingots after casting. To ensure the mechanical reliability of the final thick plates, these pores must be closed during the forming process, hot rolling in the present case. This study aims at understanding the effects of rolling parameters on the volume evolution of pores. To do so, X-ray microtomography is used to track real casting pores during deformation. Nevertheless, thick plates are too large to enable a fine characterization of the evolution of pores during the process. The size and shape of the samples as well as the mechanical boundary conditions must be optimized to meet imaging constraints. This paper focuses on the reproduction of complex loading paths. Multi-scale FE simulations are used to reproduce the loading conditions of thick plate rolling with uniaxial tests on samples of a few millimeters. Uniaxial tests are then characterized with tomography on a synchrotron X-ray beamline. In each sample, tens of pores are individually tracked, giving access to their volume evolution. The local loading path experienced by each pore is determined with FE simulation. It is shown that the volume evolution of a real pore correlates with the hydrostatic integration which is the integral of stress triaxiality along cumulated strain. This confirms that the closure of complex casting pores is enhanced by a high relative reduction and high values of L/H ratio during rolling similarly to what was observed numerically on simpler shapes.

Rolling force and length of strip head and tail sections under unsteady deformation conditions

This paper describes the results of an experimental study that looked at the distribution of strains and rolling forces along the length of brass (L63), bronze (BrOF6,5-0,23) and copper (M3, M0) strips in a 150&times;235 twin rolling mill equipped with a microcontroller-based high-precision roll load measurement system. 2 and 3 mm thick workpieces with the widths of 10, 20 and 30 mm and the length of about 200 mm taken from the commercial batches of rolled copper, brass and bronze were used for the study. The workpieces were rolled at the Kolchugino and Kirov Non-Ferrous Metals Processing Plants. The reduction rate was varied within the range of 4 to 45%. The paper contains graphs showing the distribution of rolling forces along the strip length. The graphs indicate that the length of the strip head and tail sections, which experience unsteady rolling conditions, is dictated by the reduction degree, mechanical properties and dimensions of the strip. It was found that the length of the strip head and tail sections undergoing unsteady deformation tends to increase as the reduction rate increases. It was established that the initial mechanical properties of the strips had a significant effect on the unstable rolling duration and the length of the strip head and tail sections deviating from the given dimensions of the proper strip. Regression equations were obtained that can help predict the duration of unsteady rolling conditions with regard to copper strips as a function of their initial rigidity and reduction. The results of the study can be useful when finetuning rolling mills, as well as automatic gauge control systems, to ensure strips are rolled to precision along their entire length.

Characterization of the Microstructure Changes Induced by a Rolling Contact Bench Reproducing Wheel/Rail Contact on a Pearlitic Steel

Understanding the effects of wheel-rail contact on the microstructure of rails is an important issue for railway management. The impact of wheel-rail contact and surface preparation on the microstructure of rails is studied using a rolling contact bench. Microstructure changes are characterized by coupling microhardness measurements and scanning electron microscopy combined with electron backscattering diffraction. This analysis led to a complete description of the sub-surface microstructure in link with the contact conditions. It was found that the use of a corroded layer on the material surface led to a considerable strain-hardening decrease. Lower surface strain-hardening was also found for sliding conditions compared to pure rolling conditions. EBSD characterizations using different indicators highlighted the importance of the scale of investigation: the use of Kernel Average Misorientation led to the identification of larger impacted depths than the Inverse Pole Figures.

Segregation Neutralised Steels: Microstructural Banding Elimination from Dual-Phase Steel Through Alloy Design Accounting for Inherent Segregation

Banding in commercial dual-phase steels, such as banded ferrite and pearlite or ferrite and martensite microstructures, is inherited from segregation during solidification in continuously cast material, predominantly from Mn segregation, and subsequent rolling. The banded microstructures lead to anisotropic mechanical properties which is generally undesirable. This paper presents an alloy design approach (termed “segregation neutralised” steels) to remove banding of the second phase by utilising co-segregation of both austenite and ferrite stabilisers to reduce local variability in second phase stability. The new composition proposed also considers achieving the same strength levels through maintaining the same second phase fraction, grain size and solid solution strengthening increments. Phase field modelling has been used to predict the segregation and phase transformation behaviours for a commercial composition dual-phase steel and the new composition segregation neutralised steel. A 5 kg laboratory alloy production route (casting, hot rolling and coiling simulation, cold rolling and annealing) has shown that the banded structure seen in commercial dual-phase steels is accurately reproduced and that banding has been reduced dramatically in both the hot rolled condition as well as after cold rolling and annealing in the new segregation neutralised steel. Chemical analysis has shown that in the segregation neutralised alloy the second phase distribution shows no correlation to the segregation bands, due to the achieved balance in austenite and ferrite stabilisers.

Modal Analysis of a Discrete Tire Model with a Contact Patch and Rolling Conditions Using the Finite Difference Method

Obtaining the modal parameters of a tire with ground contact and rolling conditions represents a challenge due to the complex vibration characteristic behaviors that cause the distortion of the tire’s symmetry and the bifurcation phenomena of the natural frequencies. An in-plane rigid–elastic-coupled tire model was used to examine the 200 DOF finite difference method (FDM) modal analysis accuracy under non-ground contact and non-rotating conditions. The discrete in-plane rigid–elastic-coupled tire model was modified to include the contact patch restriction, centrifugal force and Coriolis effect, covering a range from 0 to 300 Hz. As a result, the influence of the contact patch and the rotating tire conditions on the natural frequencies and modes were obtained through modal analysis.

A self-powered triboelectric multi-information motion monitoring sensor and its application in wireless real-time control

With the advantages of low power consumption, low cost and miniaturization, self-powered sensors have a wide range of applications in the human-machine interface, Internet of Things (IoTs), sports monitoring and versatile fields. Here, a novel and easy-processing self-powered triboelectric multi-information motion monitoring sensor (TM3S) is proposed and systemically investigated under the conditions of rolling and sliding motion. The relationships between electrical signals (charge, rate of charge change, current, rate of current change, voltage, etc.) and kinetic parameters (displacement, direction, velocity, acceleration, etc.) are established and verified with various motion states. The results show that TM3S can precisely detect the displacement, direction, velocity, and acceleration of the moving object, demonstrating excellent performance in motion monitoring. Furthermore, a wireless self-powered motion monitoring system based on TM3S is developed, which can detect the movement of a sliding mouse in real time, wirelessly transmit sensing data instantaneously, and achieve real-time control in human-machine interface. The real-time motion monitoring system exhibits two significant advantages of high sensitivity and self-powered nature, showing huge potential in low power consumption IoTs and intelligent human-machine interaction.