Search Results

This paper describes a proposal of techniques on Transfer Path Analysis (TPA) to analyze transmission of vibration among the components in a complex structure. This proposal is evolved from the previous one [1] in the dimension which dominates the quality of the analysis in automotive body structure by TPA. The proper coordinate transformation was introduced to resolve the troublesome process on the application of the body structure in the previous proposal. The complications are caused by the treatment with a lot of transfer functions and transmitted forces at the conjunctions that are complexly assembled with many adjacent nodes. Dimension of the analytical region is expanded from two to three in this study. That is, from the cross section of interface of components to the structure itself where the vibration transmits between two components.

Improvement of vehicle interior noise is desired in recent years in the modern world of the demand of low weight, good fuel economy and offering technical advantages strongly. The dynamic force transmission of rolling tires from the road surface to the spindles is a critical factor in vehicle interior noise. We focus on structure-borne noise transferred through the spindle. It is necessary for effort of the effective tire/road noise reduction to predict spindle force excited by tire/road contact. The major issues in predicting spindle forces are to clarify the distribution of road forces and how to input on the simulation model. Therefore, it is important that road forces are measured accurately on the rolling tire. First, the dynamic road forces on the rolling tire are measured by using the tri-axial force sensor directly. In efforts to reduce interior noise due to structure-borne noise, it is necessary to predict spindle forces excited by the tire/road contact.

This paper describes new method for selecting optimal field points in Inverse-Numerical Acoustic analysis (INA), and its application to construction of a sound source model for diesel engines. INA identifies the surface vibration of a sound source by using acoustic transfer functions and actual sound pressures measured at field points located near the sound source. When measuring sound pressures with INA, it is necessary to determine the field point arrangement. Increased field points leads to longer test and analysis time. Therefore, guidelines for selecting the field point arrangement are needed to conduct INA efficiently. The authors focused on the standard deviations of distance between sound source elements and field points and proposed a new guideline for optimal field point selection in our past study. In that study, we verified the effectiveness of this guideline using a simple plate model.

This paper presents an analytical model for the prediction of piston secondary motion and the vibration due to piston slap. For the modeling of piston slap phenomenon, cylinder liner is modeled as a several spring-mass system that are connected by modal characteristics, and lubricant film between the piston and the cylinder is modeled as reaction force vectors which excite resonant mode of them. By comparing experimental results and analytical ones, the validity of the proposed model has been confirmed. The optimization of the piston skirt profile is also carried out with the analytical model, and it is confirmed that the round shape of the lower part of piston skirt is effective for the reduction of piston slap excitation.

This paper describes the identification of a sound source model for diesel engines installed on agricultural machines by using Inverse-Numerical Acoustic (INA) analysis, and noise predictions using the sound source model identified by INA. INA is a method of identifying surface vibrations from surrounding sound pressures. This method can be applied to sound sources with complicated shapes like those in engines. Although many studies on INA have been conducted, these past studies have focused on improvements to the identified accuracy and prediction of noise in free sound field or hemi-free sound field. The authors accurately predicted the sound pressure levels of engine enclosures using a sound source model identified by INA and a boundary element method (BEM). However, we had not yet verified the effectiveness of this sound source model against enclosures that had sound absorbing materials and openings.

Dual mass flywheel (DMF) is a well-known isolation system for vehicle drivetrain. DMF has two typical elastic energy storage systems: long travel arc springs and in-series spring units (including two or more springs) and sliding shoes connected in series. DMF has such complex nonlinear characteristics as torque-dependent torsional stiffness and rotational speed-dependent hysteresis friction due to its dependency of centrifugal force that is applied to components and radial force of springs. Because of this complexity, sub-harmonic vibration (SHV) may occur under certain circumstances, such as under light-load and high-rotational conditions. In general, since SHV’s frequency is 1/2 or 1/3 of the engine’s combustion frequency and may cause human discomfort, DMF must be designed robust against such nonlinear vibration. In this paper to reduce the SHV occurrence and to show a more robust design indicator, the SHV causing the mechanism is researched by testing and 1D CAE modeling.