Rolling Rod Research Articles

Numerical analysis of nucleate boiling in rolling rod bundle with tilted axis using two-fluid modeling approach

In this study, an Eulerian-Eulerian two-fluid approach was applied to simulate nucleate boiling in a vertical rolling 2 × 2 rod bundle with a tilted axis. For this purpose, the standard multiphaseEulerFoam solver of OpenFOAM was modified to include the fictitious forces necessary in a non-inertial frame of the reference formulation. High-performance computing was then applied to analyze the effects of oscillation on boiling and the physics of the fluids inside the rod bundle. In particular, the effect of a tilted rolling axis was investigated for the first time. The results indicated that the space-averaged void fraction and surface-averaged heat transfer coefficient decrease in the rolling cases compared with the stationary case. Furthermore, it was found that while the tilt angle has a negligible effect on the space-averaged values, it may have a significant impact on the maximum value of the void fraction. The higher the tilt of the rolling axis, the higher the variation in the maximum field values. The results of this study will further improve our understanding of wall nucleate boiling, which is critical for the design, development, and safety of light water-cooled reactors (LWR).

Interface Static Friction Enabled Ultra‐Durable and High Output Sliding Mode Triboelectric Nanogenerator

AbstractUtilizing the static friction of the rolling rod/ball is an effective strategy to address the mechanical durability in sliding mode triboelectric nanogenerators (TENGs), but its line/point contact seriously reduces the output performance. Herein, a high output and ultra‐durable TENG is achieved by a rolling belt method. Compared with the previous rolling rod mode TENG (R‐TENG), the electric output performance of the rolling belt mode TENG (RB‐TENG) increases nearly 3.8 times. The maximum output power density of RB‐TENG reaches ≈280 W m‐2 with self‐charge excitation and power management, and its charge density is the highest among all sliding mode TENGs without sliding friction including rolling rod/ball mode and noncontact freestanding mode. Furthermore, the RB‐TENG remains nearly 98.5% of its output performance after more than 4 100 000 cycles, which is the highest stability measured in such a long time by now, with material abrasion quality 6.42 µg·g‐1 (<1% of traditional sliding TENG) every 10 000 cycles. This work provides an effective strategy for solving the bottleneck issues of mechanical abrasion in sliding mode TENGs.

Frictional collision acceleration and damage of potato peel: an experimental study

ABSTRACT To obtain the acceleration characteristics of frictional collision between potato and rod, and reveal the mechanism of potato peel damage, a frictional collision test rig was designed to conduct single factor test and peel damage threshold test. Results showed that the maximum frictional collision acceleration (MFCA) decreased linearly with the increase of potato mass and increased linearly with the increase of initial height. The MFCA of potato colliding with the horizontal rod was smaller than that with the vertical rod, and the MFCA with the rolling rod was smaller than that with the fixed rod. The MFCA decreased in turn when potato was collided with 65Mn-rubber, 65Mn-plastic and 65Mn. The acceleration threshold of peel damage for 250 g potato was the smallest when it collided with 65Mn rod fixed in the horizontal direction from 50 mm height, which was 15.56 m/s2. The acceleration threshold was the largest for the collision with 65Mn-rubber rod fixed in the vertical direction, which was 113.6 m/s2. The research methods and conclusions of this article provided a basis for the analysis of potato peel damage mechanism, and also provided a reference method for researches on the peel damage of solid–like agricultural materials and food.

Postural control in paw distance after labyrinthectomy-induced vestibular imbalance.

Balance control is accomplished by the anatomical link which provides the neural information for the coordination of skeletal muscles. However, there are few experimental proofs to directly show the neuroanatomical connection. Here, we examined the behavioral alterations by constructing an animal model with chemically induced unilateral labyrinthectomy (UL). In the experiment using rats (26 for UL, 14 for volume cavity, 355-498g, male), the models were initially evaluated by the rota-rod (RR) test (21/26, 80.8%) and ocular displacement (23/26, 88.5%). The duration on the rolling rod decreased from 234.71 ± 64.25s (4th trial before UL) to 11.81 ± 17.94s (1st trial after UL). Also, the ocular skewed deviation (OSD) was observed in the model with left (5.79 ± 3.06°) and right lesion (3.74 ± 2.69°). Paw distance (PW) was separated as the front (FPW) and the hind side (HPW), and the relative changes of HPW (1.71 ± 1.20cm) was larger than those of FPW (1.39 ± 1.06cm), providing a statistical significance (p= 1.51 × 10-4, t test). Moreover, the results of the RR tests matched to those of the changing rates (18/21, 85.7%), and the changes (16/18, 88.9%) were dominantly observed in HPW (in FPW, 2/18, 11.1%). Current results indicated that the UL directly affected the changes in HPW more than those in FPW. In conclusion, the missing neural information from the peripheral vestibular system caused the abnormal posture in HPW, and the postural instability might reduce the performance during the voluntary movement shown in the RR test, identifying the relation between the walking imbalance and the unstable posture in PW. Graphical abstract.

Coupling one-dimensional user code and STAR-CCM+ for simulation of rolling conditions in a rod bundle channel

The numerical simulation of the one-dimensional user code and the three-dimensional software STAR-CCM + coupling is performed on a natural circulation loop of a 3 × 3 rod bundle channel under rolling conditions. The coupling simulation method in this paper utilizes our one-dimensional user code, which is compiled and linked to generate a dynamic link library (DLL). The DLL is then imported into STAR-CCM+, so as to realize the coupling simulation of the one-dimensional user code and the three-dimensional Computerized Fluid Dynamics (CFD) code. In the one-dimensional user code, the mathematical model under rolling conditions is established to simulate the natural circulation loop except for the rod bundle channel. Adding a rotational motion to the STAR-CCM + enables a rolling simulation of the rod bundle channel. In order to compare the rationality of the coupled simulation, this paper also reports on the results carried out in an uncoupled simulation to study the rod bundle channel under the rolling conditions. The coupled simulation is a simulation that can be performed independently of an experiment, but the uncoupled simulation is not. That fact further demonstrates the wide applicability of the coupled simulation. The flow velocity and pressure drop characteristics in the 3 × 3 rod bundle channel are investigated. The results show that the coupled simulation method can predict the flow characteristics of the rolling rod bundle channel in the natural circulation loop well. The paper describes the coupling method in detail, which can make a foundation for future coupling research.

Impact of radial-shear rolling on the microstructure and mechanical properties of 08Х18Н10Т stainless austenitic steel

Grinding of a structural material microstructure to an ultrafine grain state is a way to increase the strength of it. Intensive plastic deformation is the most perspective method of obtaining ultrafine grain materials. However, with the simultaneous increase in strength properties in ultrafine materials, there is an inevitable decrease in its plastic properties; they are becoming fragile and subject to failure during elongation. The use of metal materials with a gradient structure, having course grain size in the central part of the billet and decreasing to ultrafine grain size at the surface, is an effective way to solve the problem of increasing the plasticity of the metal products in general. Possibilities of forming an ultra-fine grained gradient structure in 08X18N10T stainless austenitic steel by using radial-shear rolling studied. The results of the research showed that the ultra-fine grained structure in the radial-shear rolling rod formed on the mill extends from its surface to a depth of at least a quarter of the radius of the rod. The transition zone is in the region between 0.5R and 0.25R of the bar section. Due to the structural heterogeneity of the cross-section of the bar, there is a smooth drop in the micro-hardness from the surface zone of the bar to its central zone by 10.2 %. All this testifies to the gradient character of the structure formed in the bars of 08X18N10T steel during shaping by radial-shear rolling. Studies of the mechanical properties of the deformed bars of 08X18N10T stainless austenitic steel showed that they monotonously change depending on the number of passes. After 7 passes the strength increased almost 2 times to a value of 1073 MPa, and the elongation, which is one of the indicators of the plasticity of the material, was also reduced by 2 times, reaching 21% from the original value of 40%. The results showed a possibility to obtain the gradient structure with increased level of mechanical properties by radial-shear rolling of long billets of 08Х18Н10Т austenitic stainless steel.

Performance of bi-directional elliptical rolling rods for base isolation of buildings under near-fault earthquakes

Rolling base isolation system provides effective isolation to the structures from seismic base excitations by virtue of its low frictional resistance. Herein, dynamic analysis of flexible-shear type multi-storey building mounted on orthogonally placed elliptical rolling rod base isolation systems subjected to bi-directional components of near-fault earthquake ground motions is presented. The orthogonally placed rods would make it possible to resist the earthquake forces induced in the structure in both the horizontal directions. The curved surface of these elliptical rods has a self-restoring capability due to which the magnitude of peak isolator displacement and residual displacement is reduced. The roughness of the tempered curved surface of the rollers dissipates energy in motion due to frictional damping. The seismic performance of the multi-storey building mounted on the elliptical rolling rod base isolation system is compared with that mounted on the sliding pure-friction and cylindrical rolling rod systems. Parametric studies are conducted to examine the behavior of the building for different superstructure flexibilities, eccentricities of the elliptical rod, and coefficients of friction. It is concluded that the elliptical rolling rod base isolation system is effective in mitigation of damaging effects of the near-fault earthquake ground motions in the multi-storey buildings. Even under the near-fault earthquake ground motions, the base-isolated building mounted on the elliptical rolling rods shows considerable reduction in seismic response. The isolator displacement with the elliptical rolling rod base isolation system is less in comparison to the pure-friction and cylindrical rolling rod systems.

Resistance characteristics of air–water two-phase flow in a rolling 3 × 3 rod bundle

Experimental investigation on ambient air–water two-phase flow in a 3×3 rod bundle subjected to rolling motion was carried out. Time-averaged and transient frictional resistance in rolling motion were studied in detailed. The results indicate that although time-averaged flow rate and frictional pressure drop in rolling rod bundle are very close to that under steady vertical condition, rolling motion induces obvious transient periodical fluctuation of frictional pressure gradient at low gas and liquid flow rate. While the periodical fluctuations become unconspicuous at high gas and liquid flow rate. In addition, the fluctuation amplitude of relative frictional gradient increases with the increasing of rolling amplitude. However, it is nearly invariable with the rolling period. The traditional correlations which are developed for non-rolling condition give poor predictions for transient frictional gradient when it fluctuates significantly. By taking into account of the influences of rolling parameters, a new correlation applied to calculate the transient frictional resistance in rolling rod bundle is achieved, showing good agreement with experimental results.

Experimental and theoretical analysis of bubble rising velocity in a 3 × 3 rolling rod bundle under stagnant condition

As a typical ocean condition, rolling motion has a significant effect on the two-phase flow systems. The influences of rolling motion on the bubble rising velocity were studied theoretically and experimentally. Five following rolling conditions were investigated: θm5°T8s, θm10°T8s, θm15°T8s, θm15°T12s, and θm15°T16s, where θm is the maximum rolling angle and T represents the rolling period. The theoretical results show that the fluctuation amplitude of axial tangential acceleration is much larger than that of axial centrifugal acceleration. Although the amplitude of (aroll)a is much lower than the value of axial gravitational acceleration, it shows evident influence on the phase curve of axial resultant acceleration. The difference between adjacent troughs in the phase curve of aa increases as a result of a decreased rolling period or increased rolling amplitude and parameter y′, where y′ represents the horizontal coordinate that is attached to the frame and is in the plane in which the rolling side-to-side motion takes place. The experiments were conducted in a 3×3 rod bundle under stagnant condition. The experimental results show that the fluctuation amplitude of bubble rising velocity increases with the increase in rolling amplitude or the decrease in rolling period. In addition, the effect of rolling amplitude is much more significant than that of rolling period. The fluctuation of bubble rising velocity presents one peak in one rolling period under the conditions of θm5°T8s, θm10°T8s and θm15°T8s. However, it presents two peaks under the conditions of θm15°T12s and θm15°T16s. The axial resultant acceleration gives rise to the fluctuation of bubble rising velocity.

A piezoelectric pulse generator for low frequency non-harmonic vibration

This paper reports a new piezoelectric prototype for pulse generation by energy harvesting from low frequency non-harmonic vibration. The pulse generator presented here consists of two parts: the electromechanical part and the load circuit. A metal rolling rod is used as the proof mass, moving along the substrate to achieve both actuating of the piezoelectric cantilever by magnetic coupling and self-synchronous switching of the circuit. By using this new approach, the energy from the piezoelectric transduction mechanism is regulated simultaneously when it is extracted. This allows a series of tuneable pulses to be generated, which can be applied to self-powered RF wireless sensor network (WSN) nodes.

The effect of poly (L-lactic acid) nanofiber orientation on osteogenic responses of human osteoblast-like MG63 cells

In this study, poly (L-lactic acid) (PLLA)/trifluoroethanol (TFE) solution was electrospun to fabricate fibrous scaffolds with different fiber orientations. Random and parallel PLLA nanofiber alignments were achieved by using a metal plate and a rolling rod as the receiver, respectively. The parallel PLLA fibrous scaffolds were further hot-stretched to obtain hyperparallel PLLA fibrous scaffolds. The PLLA fibrous scaffolds were characterized by fiber diameter, interfiber distance, fiber array angle, water contact angle, morphology and mechanical strength. The tensile strength of hyperparallel nano-fibers was approximately 5- and 14-times the parallel and random fibers, respectively. Osteoblast-like MG63 cells were cultured on the PLLA scaffolds to study the effects of fiber orientation on cell morphology, proliferation and differentiation. The cells on the randomly-oriented scaffolds showed irregular forms, while the cells exhibited shuttle-like shapes on the parallel scaffolds and had larger aspect ratios along the fiber direction of the hyperparallel scaffolds. Alkaline phosphatase (ALP) activity and collagen I (placeStateCol I) and osteocalcin (OC) deposition exhibited fiber orientation dependence. With an increase in parallelism of the fibers, there was a decrease in ALP activity and placeStateCol I and OC production. These results suggest that exploitation of PLLA fiber orientation may be used to control osteoblast-like cell responses.

Flexible substrate electrostatic energy harvester

Energy harvesting is attractive for powering wireless sensors, especially in applications such as body sensor networks and pervasive sensing, where power source replacement or recharging is impractical. A MEMS (micro-electro-mechanical systems) electrostatic harvesting device suitable for body motion has been reported previously, using a rolling rod as the proof mass. A new rolling rod device is presented, employing a flexible substrate to allow the formation of a concave structure. Suitable rod confinement and increased rod–plate capacitance are achieved. Regular power transduction even under impulse motion excitation is reported, supplying 0.5 µW of output power.

Перспективная технологическая схема высокоскоростной прокатки катанки

Перспективная технологическая схема высокоскоростной прокатки катанки

銅線の軟化特性に及ぼす熱間圧延銅線製造方法と不純物の影響

The softening characteristics of cold-drawn pure copper wires were studied in relation to hot-working processes and impurities of hot worked Cu wire rods. The characteristics of several kinds of hot-rolled wire rods were examined by means of structural observations, tensile tests and electrical resistivity measurements. The softening characteristics of cold-drawn copper wires were obtained from spring elongation tests and electrical resistivity measurements of 90% cold-drawn wires.It was found that the grain size and Cu2O particle size of the continuous casting and rolling rod (SCR: Southwire Continuous Rod) were the smallest and its Cu2O particle distribution was uniform. On the other hand, the grain size of Oxygen Free Copper (OFC) wire rod was the largest and its electrical conductivity was the highest. SCR cold-drawn copper had the lowest softening temperature. Specimens of copper wires could be arranged according to the order of softening tendencies by annealing:\ oindentSCR>TPC 1(normal Tough Pitch Copper)>OFC>TPC 3(Tough Pitch Copper with 16 ppm Pb and 11 ppm Sn).\ oindentA large amount of annealing twins was observed in the SCR wires.From these experimental results, the softening characteristics of the cold-drawn copper wires are considered to be related to metallurgical structure which depends on the hot-working processes and purities.