Atsuo Sueoka

Quenching of vortex-induced vibrations of towering structure and generation of electricity using Hula-Hoops

Abstract This paper deals with the quenching problem of vortex-induced vibrations by using devices composed of Hula-Hoops and generators. These devices are also able to generate electricity. The experiment was made concerning the quenching problem of the vortex-induced vibrations of towering structures with the devices. Moreover, a numerical analysis was also carried out using the Runge–Kutta–Gill method. An optimum approach for quenching the vortex-induced vibrations of low and high flexural rigidity directions are discussed. As a result, the following was made clear: (1) The vortex-induced vibrations of both flexural rigidity directions were well quenched for a wide range of wind velocities and the different wind directions by using four devices simultaneously. (2) The optimally quenched vibration was a chaos of intermittency. (3) A condition of maximum power generation was not equal to that of the optimum vibration quenching of the main system. (4) The experimental and the analytical results were in good qualitative agreement with each other.

Effect of Stiffness Ratio of Piecewise-Linear Spring on the Occurrence of Subharmonic Nonlinear Vibration in Automatic Transmission Powertrain

In the torque converter, a damper with a piecewise-linear spring is used to reduce the forced vibration, and the subharmonic vibration occurs when the spring restoring torque characteristics approach the switching point. This research analyzed the effect of stiffness ratio between the neighboring piecewise-linear springs on the occurrence of the subharmonic nonlinear vibration in automatic transmission powertrain. The powertrain is modeled with multi degree-of-freedom nonlinear system as an actual vehicle. The result shows higher value of the stiffness ratio between the neighboring springs creates larger value of the subharmonic vibration.

Pattern Construction Generated in a Winder System of Textile Machine.

Elastic yarns in the winder system of a textile machine are deformed into a certain convex polygon in the process of winding at an operating speed of the bobbin holder rotating viscoelastically in contact with the drive roll. The polygonal deformation increases and develops into a serious vibration of the machine. This paper presents a model and a theoretical analysis to investigate the mechanism of this vibration phenomenon which is regarded as instability due to the time lag. The bobbin holder and the drive roll are both modelled by the one-mass one-shaft system. From the numerical computations using parameters obtained experimentally, the analytical results showed a good agreement with the phenomenon generated in the actual machines.

Optimal Design of Spring Characteristics of Damper for Subharmonic Vibration in Automatic Transmission Powertrain

In the torque converter, the damper of the lock-up clutch is used to effectively absorb the torsional vibration. The damper is designed using a piecewise-linear spring with three stiffness stages. However, a nonlinear vibration, referred to as a subharmonic vibration of order 1/2, occurred around the switching point in the piecewise-linear restoring torque characteristics because of the nonlinearity. In the present study, we analyze vibration reduction for subharmonic vibration. The model used herein includes the torque converter, the gear train, and the differential gear. The damper is modeled by a nonlinear rotational spring of the piecewise-linear spring. We focus on the optimum design of the spring characteristics of the damper in order to suppress the subharmonic vibration. A piecewise-linear spring with five stiffness stages is proposed, and the effect of the distance between switching points on the subharmonic vibration is investigated. The results of our analysis indicate that the subharmonic vibration can be suppressed by designing a damper with five stiffness stages to have a small spring constant ratio between the neighboring springs. The distances between switching points must be designed to be large enough that the amplitude of the main frequency component of the systems does not reach the neighboring switching point.

Fundamental study of subharmonic vibration of order 1/2 in automatic transmissions for cars

A torque converter is an element that transfers torque from the engine to the gear train in the automatic transmission of an automobile. The damper spring of the lock-up clutch in the torque converter is used to effectively absorb the torsional vibration caused by engine combustion. A damper with low stiffness reduces fluctuations in rotational speed but is difficult to use because of space limitations. In order to address this problem, the damper is designed using a piecewise-linear spring with three stiffness stages. However, the damper causes a nonlinear vibration referred to as a subharmonic vibration of order 1/2. In the subharmonic vibration, the frequency is half that of the vibrations from the engine. In order to clarify the mechanism of the subharmonic vibration, in the present study, experiments are conducted using the fundamental experimental apparatus of a single-degree-of-freedom system with two stiffness stages. In the experiments, countermeasures to reduce the subharmonic vibration by varying the conditions of the experiments are also performed. The results of the experiments are evaluated through numerical analysis using the shooting method. The experimental and analytical results were found to be in close agreement.

Vibration Analysis of a Moving Probe with Long Cable for Defect Detection of Helical Tubes

A defect detection of a heating tube installed in a power station is a very important process for avoidance of a serious disaster. The defect detection for the fast breeder reactor “Monju” in Japan is implemented by feeding an eddy current testing (ECT) probe (Isobe et al., 1995; Robinson, 1998) with a magnetic sensor, into the tube. The ECT probe (hereafter, simply called probe) is controlled so as to move in the heating tube at a constant velocity. A peculiar feature of the heating tubes in “Monju” is that each tube is mostly helical. An undesirable vibration of the probe always happened in the helical heating tube under a certain condition (Inoue et al., 2007). The vibration was considerably large and generated an obstructive noise in the signal of the magnetic sensor. It made the detection of defects difficult. Some papers reported similar problems (Bihan, 2002; Giguere et al., 2001; Tian and Sophian, 2005), but a large vibration of the probe was not involved. A key to the problem is that the noise in the signal was accompanied with the hard vibration. Several characteristics of the vibration became clear through some experiments by using a mock-up, and a countermeasure was taken by making use of the characteristics of the vibration (Inoue et al., 2007). However, an essential factor on the cause of the vibration was still unclear. Since the noise in the signal is highly correlated with the vibration, a thorough investigation of the vibration is needed. It is desirable to find out the cause of the vibration in order to remove or reduce the vibration and ensure the reliability of the inspection. In this study, the cause of the vibration is assumed to be Coulomb friction between floats, which are attached to the probe, and the inner wall of the heating tube on the basis of the experimental results. An analytical model is obtained by taking Coulomb friction into account and numerical simulation is implemented by applying a step-by-step time integration scheme. However, the analytical model has a very large number of degree of freedom. Furthermore, there are many points on which Coulomb friction acts when the probe is fed into the tube under air pressure since many floats, which are in contact with the inner wall of the heating tube, are attached to the probe. It implies that a lot of strong nonlinearities exist in the analytical model. There is no precedent for this kind of problem, and heavy computational costs are ordinarily required to carry out the numerical simulation. Sueoka et al. (1985) presented the Transfer Influence Coefficient Method (Inoue et al., 1997; Kondou et al., 1989, hereafter: TICM), which is a computational method for a dynamic

Application of Transfer Influence Coefficient Method to Inverse Iteration Method.

The inverse iteration method is one of the most effective methods of eigenvalue analysis and is suited for both vibration and structural analyses. It can compute eigenvalues in the order of increasing absolute value, the convergence of iterative computation can be accelerated by applying the technique of origin shift. However, the inverse iteration method must be able to solve a large-sized simultaneous linear algebraic equation in every iterative process. In order to improve the computation accuracy and the computation speed of the inverse iteration method, we introduce the concept of the transfer influence coefficient method into the iterative process. The transfer influence coefficient method is advantageous in that it can solve simultaneous linear algebraic equations, and the memory size required in the computation is extremely decreased. The present method is applied to both the undamped and the damped systems.

Polygonal Deformation of Roll-Covering Rubber. Practicability of Prediction Method.

Rubber-covered rolls are in wide use in many machines for processing, pressing and conveying paper and plastic film. We have studied the polygonal deformation caused by viscoelastic deformation of roll-covering rubber under high load and at high speeds. It is said that the above-mentioned phenomenon is influenced by rubber damping and its deformation recovery characteristics. Previously, we reported a prediction method for analysis of this phenomenon, regarding viscoelastic deformation as causing instability due to the time-delay deformation. In this study, we compared experimental with calculated results, and found good agreement between them. Moreover, in this report we describe methods for preventing polygonal deformation.

Chaotic Behavior of a Nonlinear Vibrating System with a Retarded Argument (Characteristics in the Region of Subharmonic Resonance).

In this paper, we consider the characteristics of a nonlinear vibrating system, i. e., the van der Pol and Duffing equation, with a retarded argument under a harmonic exciting force. A numerical analytical procedure has been applied to analyze the characteristics in the subharmonic resonant region of the system. The system has been found to show quite complex charachteristics, e.g., many kinds of subharmonic oscillations, both symmetric and asymmetric subharmonic solutions, difurcations and nonperiodic solutions. Each of these subharmonics has shown isolated, island like response curves. With the use of numerical simulation, Poincare mapping, basin of attractions and chaotic phenomena, corresponding to nonperiodic solutions, have been obtained. The chaotic behavior appears in various frequency regions. These nonperiodic motions have been concluded to be chaotic because of the positive Lyapunov exponent. The route to chaos is via period doubling bifurcations.

直列形非線形構造物の強制振動解析 : 第2報, 断片線形系の取扱いと数値計算結果

A numerical computational method is suggested for the nonlinear analysis of a piecewise linear system including a system with clearances which is often found in practical mechanical structures. When this method is combined with the analytical method for the nonlinear system based on the concept of harmonic balance, the piecewise linear system is analyzed with high accuracy. The validity of the incremental transfer influence coefficient method formulated in the previous report for the structure connected in series is verified by the numerical computational results for some examples, as compared with those of the incremental harmonic balance method and the incremental transfer matrix method. As a result, it was confirmed that the incremental transfer influence coefficient method was the most effective among the three methods as the degrees of freedom of the structure treated become large and the accuracy of an approximate solution becomes high.