Katsuhide Fujita

Experimental Study on Dynamic Behavior of a Rolling Agricultural Tire

When agricultural machines are operated on pavements, the vibration and noise caused by the interaction between the tire lugs and the road surface are inevitable. In conventional studies, it is considered that the dynamic behavior of a rolling agricultural tire is influenced by the vibration characteristics of the tire. Resonance occurs when the lug excitation frequency of the tire, which is defined as the lug number multiplied by the number of revolutions of the tire, becomes equal to the natural frequency of the tire. In other words, the rolling tire shows large vibrations in the direction of the natural mode corresponding to the natural frequency of the tire. However, the vibration mode of the rolling tire in resonance state has not yet been clarified. In this study, it is confirmed that the dynamic behavior of the rolling tire can be evaluated by performing sound pressure measurements using closely located microphones to the tire. Further, the vibration mode in the resonance state is identified by performing simultaneous measurements of the sound pressure, and the vibration mode corresponds to the natural mode of the tire is confirmed as well.Copyright

Application to the Reciprocating Compressor Condition Monitoring Using Vibration Models

The purpose of this study is to establish a new monitoring technique to detect the state of sliding portion and connecting portion, where it is known that some failure often occurs.In this paper, we examined the feasibility of estimation for the state in which the support rigidity of the sliding portion using the vibration characteristics in the experiment for a small experimental equipment and in the eigenvalue analysis based on the mathematical model. To simulate the change of the rigidity for the sliding portion, we employ two kinds of material, carbon and molybdenum steel as the ring bush of the ground support. To obtain the natural frequencies and modes for both the case, the impact tests are carried out for several crank angles in the small experimental apparatus as the vibration characteristics is depend upon the crank angle. Based on the obtained natural frequencies, the parameter identification was carried out. As a result, it showed the possibility of estimating the characteristics of the sliding portion by focusing on the natural vibration characteristics.Copyright

Experimental Research on Dynamic Characteristics of a Rolling Agricultural Tire: Measurement of Forces Acting on Tire Shaft

When agricultural machines are operated on pavements, the lug excitation force occurring on a rolling agricultural tire is primary cause of the vibration. Therefore, it is important to investigate the lug excitation force in order to clarify the vibration generation mechanism. In our previous study, it is considered that the dynamic behavior of a rolling agricultural tire is influenced by the vibration characteristics of the tire. Further, only the rigid modes among the natural modes could affect the rolling tire behavior. So, we modeled the tire as a circular rigid ring supported on an elastic foundation with contact model. This rigid ring model can be valid to investigate the lug excitation force, while it is necessary to measure forces acting on tire shaft in order to estimate the lug excitation force. In this study, the test equipment is modified to measure tire shaft forces at rolling, by improved supporting structure equipped with 6-component force transducers and the shaft force characteristics are investigated. It is confirmed that the vibration characteristics of the tire influence the shaft force characteristics.Copyright

Verification of the Vibration Characteristics of a Reciprocating Compressor in Operation and the Proposal of the Model Parameters Estimation Method

Vibration characteristics of a reciprocating compressor are discussed. To investigate the frequency characteristics in the operation of unhealthy and healthy, we employed the proposed model, which includes stiffness characters about both the connecting and the sliding parts. Expressing the motion of the reciprocating compressor as a rigid body model with eleven degrees of freedom, we numerically investigated the frequency characteristics in operation and the natural vibration characteristics based on a locally linearized method. To examine the frequency characteristics, we carried out vibration tests using a small experimental machine and the eigenvalue analysis based on the proposed model. Comparing the analytical results with experimental results, we found that the proposed model could simulate the fundamental frequency characteristics in operation and the natural modes. Eigenvalue analysis shows that the natural frequencies and modes for a reciprocating compressor depend upon the angle of the crankshaft. In the proposed model, it can express the dominant frequencies occurring during operation and the natural vibration characteristics.Copyright

Experimental Research on Dynamic Characteristics of a Rolling Agricultural Tire (Influence of Running Condition)

When agricultural machines are operated on pavements, the vibration and noise caused by the interaction between the tire lugs and the road surface are inevitable. In conventional studies, it is considered that the dynamic behavior of a rolling agricultural tire is influenced by the vibration characteristics of the tire. Resonance occurs when the lug excitation frequency of the tire, which is defined as the lug number multiplied by the number of revolutions of the tire, becomes equal to the natural frequency of the tire. In other words, the rolling tire shows large vibrations in the direction of the natural mode corresponding to the natural frequency of the tire. However, in the conventional equipment, the diameter of the drum is smaller than that of the tire. Therefore, the real running condition on the road was not realized by the rolling test using the conventional equipment. In this study, a new equipment is produced to realize the running condition in the rolling test. The dynamic and vibratory characteristics of operating agricultural machine are investigated by using this new equipment. The obtained results are compared to the conventional ones and the influence of the running condition on dynamic characteristics of rolling tire is investigated.Copyright

Research on Fluctuating Forces Occurred in Components of Reciprocating Hydrogen Compressors

This paper treats dynamic analysis about reciprocating compressors used in a petroleum refining plant and a petrochemical plant. In order to clarify the cause of damage occurred as a result of long-term operation, we investigated the effects of deterioration around the connecting parts and the sliding parts on the dynamics of the system. Introducing the rigid body model with eleven degrees of freedom, we have determined the model parameters based on beam theory and the Hertz contact theory. By comparison with experimental results, we showed validity of the proposed model. Thus, changes in the characteristics of the middle spring piston rod were found to be a major impact on the dynamics of the system [1].Copyright

Influence of Patch Boundary Condition on the Vibration Characteristic of an Agricultural Tire

Though it is well known that the vibration and the noise of agricultural machinery during running on a road are strongly influenced by the tire lug form, few studies have been carried out to clarify this mechanism, while many studies were done on the characteristics of automobile tire. In the previous studies for automobile tire, the tire is typically modeled as a thin, cylindrical beam on a continuously distributed elastic foundation representing the sidewall stiffness. However, this model cannot be directly applied to agricultural tire, because of non-uniform stiffness effect caused by tire lugs. In this research, natural frequencies and mode shapes of a non-rotating agricultural tire are assessed by the experimental modal analysis method for two boundary conditions: without the ground contact and with the ground contact. Then, the tire is modeled as a thin, cylindrical beam with multiple radial spring attachments, which represent tire lugs with non-uniform radial stiffness. A calculation procedure based on the receptance method for obtaining the natural frequencies of tire is formulated, then applied to the said two boundary conditions. Furthermore, the fundamental parameters of tire are identified from the measured natural frequencies using Downhill Simplex method. As a result, the influence of boundary conditions on the parameter is clarified.Copyright