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Technical Paper

Investigation and Improvement of a Bouncing Torsional Vibration in Automotive Dual Mass Flywheel by Combining Testing and 1D CAE Modeling Approach

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.
Technical Paper

Construction of Sound Source Model for Diesel Engine Using New Method for Selecting Optimal Field Points in Inverse-Numerical Acoustic Analysis

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.
Technical Paper

Vibration Analysis of Rotating Tires Focused on Effect of Rotation Using a Three - Dimensional Flexible Ring Model

The tire is one of the most important parts, which influence the noise, vibration, and harshness of the passenger cars. It is well known that effect of rotation influences tire vibration characteristics, and earlier studies presented formulas of tire vibration behavior. However, there are no studies of tire vibration including lateral vibration on effect of rotation. In this paper, we present new formulas of tire vibration on effect of rotation using a three-dimensional flexible ring model. The model consists of the cylindrical ring represents the tread and the springs represent the sidewall stiffness. The equation of motion of lateral, longitudinal, and radial vibration on the tread are derived based on the assumption of inextensional deformation. Many of the associated numerical parameters are identified from experimental tests.
Technical Paper

Application of Transfer Path Analysis (TPA) to a Mechanical Structure with a Variety of Transfer Paths

In a typical mechanical product such as an automobile or construction machinery, it is important to identify deformation modes, for which experiments and analyses can result in significant improvements. It is also important to consider how to improve the structure with high rigidity by using a technique such as the strain energy method in conventional design and development. However, the abovementioned method often generates conflicting results with regard to weight saving and cost reduction of development requirements. Transfer path analysis (TPA) using the finite element method (FEM) is an effective way to reduce noise and vibration in the automobile with respect to these issues. TPA can reveal the transfer path from the input to the response of the output point and the contribution of the path, and to efficiently consider improved responses.
Technical Paper

Placement Technique of Measurement Points for Inverse Acoustic Analysis

This paper describes a measurement points' placement technique for the sound source identification using inverse acoustic analysis. In order to reduce noise in NVH problem for various kinds of machines including small size engine, it is necessary to identify the sound source. The inverse acoustic analysis is a technique that is effective for the sound source identification.[1,2] The inverse acoustic analysis identifies a surface vibration of an object by measuring the radiated sound and solving the inverse problem. Nakano et al. researched about the location of sound pressure measurement points for accurate improvement.[3] They clarified that the sound pressure measurement points on the concentric circle gave more accurate surface vibration than the measurement points on the square lattice.
Technical Paper

Natural Frequency Analysis of Tire Vibration Using a Thin Cylindrical Shell Model

Early studies on the tire vibration characteristics of road noise focused on radial modes of vibration because these modes are dominant in vertical spindle force. However, recent studies of Noise, Vibration and Harshness (NVH) prediction have suggested that tire modeling not only of radial modes, but also of lateral vibration, including lateral translational and lateral bending modes, affect interior noise. Thus, it is important to construct tire dynamic models with few degrees of freedom for whole-vehicle analysis of NVH performance. Existing tire dynamics model can't express tire lateral vibrations. This paper presents a new approach for tire vibration analysis below 200Hz, and a formula for tire natural frequencies. First, a tire dynamic model is developed based on the thin cylindrical shell theory. Kinetic and potential energies are derived. Mode shape function is also derived by the assumption of inextensility in the neutral of the tread ring.
Technical Paper

Identification of Sound Source Model Using Inverse-Numerical Acoustic Analysis and Noise Prediction for Engine Enclosure

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.
Technical Paper

Prediction of Vibration at Operator Position and Transfer Path Analysis Using Engine Multi Body Dynamics Model

This paper describes a prediction of vibration and the transfer path analysis (TPA) using an engine multi body dynamics (MBD) model and measured frequency response functions (FRFs). TPA is used in order to analyze each contribution of vibration transfer paths. In the TPA, input forces from vibration source to passive part should be identified accurately. In the traditional TPA, an identification of input forces is done using only experimental results. Therefore, a parametric study to an improvement of a structure or an isolation system is impossible. In this study, the MBD model of engine is constructed, and input forces from engine to mainframe of agriculture machine are predicted. The accuracy of prediction is confirmed, compared with the results from the traditional TPA method. The contribution of each transfer path is analyzed, and the vibration levels of operator position are predicted using the measured FRFs and the simulated input forces.
Journal Article

Vibration Behavior Analysis of Tire Bending Mode Exciting Lateral Axial Forces

The demand to reduce noise in the passenger cars is increasing. Tire vibration characteristics must be considered when studying road noise because of the strong interaction between tire vibration characteristics and interior car noise. Car manufacturers are keenly interested in studies on the prediction of NVH (Noise, Vibration and Harshness) performance, including viewing tires as substructure. Recently, studies have illustrated the effect that tire lateral bending mode have has on road noise, while most past studies of tire vibration focused on the circumference mode, which excited the vertical spindle force. Therefore, further study of tire lateral bending mode is necessary. Modeling of the tire lateral bending mode is described in this paper. First, lateral spindle force is measured under tire rolling conditions. Second, experimental modal analysis is performed to grasp tire lateral bending mode. Finally, a tire vibration model is built using the cylindrical shell theory.
Journal Article

Vibration Analysis of Tire Circumferential Mode Under Loaded Axle

Road noise is one of the main vehicle interior noises. To minimize this, it is necessary to reveal the vibration characteristics of a rolling tire. Tire vibration has complex behavior due to tire contact with the road and rolling. In an earlier study, we clarified the effect of contact patch restriction for tire vibration characteristics in the non-rolling condition using the tire dynamical model. However, mode shapes were identified with circumferential wave number. Therefore, it is difficult to clarify the effect for tire vibration in the contact and rolling condition. In this paper, we will apply the receptance method, which is used as an analysis of the rotating disc and gear pair for the tire model toward the tire vibration analysis in the contact and rolling condition. Furthermore, the validity of the approach using this method will be verified from comparison with the result of an earlier study.
Technical Paper

Identification of Tire Equivalent Stiffness for Prediction of Vertical Spindle Forces

The research into vibration characteristics of a loaded and rolling tire is essential for the prediction of spindle forces. There are tire vibration characteristics one of which is the first natural frequency of a loaded and rolling tire is lower than that of an unrolling tire. The vibration characteristics, for a loaded and rolling tire, are affected by the effect of rotation, restrictions of the vibration due to road contact, and the behavior of rubber dependent on amplitude strain. The consideration of the degradation of natural frequency is therefore necessary in the tire model for prediction of spindle forces. This paper describes an identification method for the tire equivalent stiffness of a tire model focused on vertical spindle forces. The first mode is dominant in vertical spindle forces. First, the natural frequencies in rolling and unrolling tires are identified by operational impact test.
Journal Article

Vibration Transmission Analysis of Automotive Body for Reduction of Booming Noise

This paper presents progressive techniques based on the previous SAE papers [1], [2] for vibration transmission analysis (VTA) on finite element (FE) model using Transfer Path Analysis (TPA). The techniques are: 1) a contribution calculation technique for structure with manifold and continuous transfer paths: 2) a visualization technique of the influence degree for efficient derivation of measures for response reduction. In VTA, influence degree of each DOF is calculated based on TPA. In order to understand characteristics of vibration transmission (VT) easily and visually by engineers, magnitude of influence degree is expressed by replacement to magnitude of displacement in the diagram of FE vibration shape. This visualization technique is applied to an automotive body structure. The proposed techniques are applied to automotive body structure consisting of members and panels. The members are such as pillars, cross members and side members, which are the main VT paths.
Technical Paper

Damping loss factor prediction in statistical energy analysis for co-generation system enclosure

This paper describes damping loss factor prediction in statistical energy analysis (SEA) for co-generation system (CGS) enclosures. To accurately predict vibration and noise by SEA, it is important to estimate parameters called the damping and coupling loss factors. In this study, the damping loss factors were estimated by the decay ratio method and a technique for calculating the modal damping ratio that uses a multi-degree of freedom curve fit. The calculated loss factor was applied to the vibration prediction of the co-generation system, and the influence of the internal loss factor calculation method on prediction accuracy was verified.
Technical Paper

Evaluation of Feeling of Pulse for Cruiser-type Motorcycle

This paper describes the relationship between the rider's evaluation of feeling of pulse and the seat vibration of the cruiser-type motorcycle. A simulated running condition was created to measure the seat vibration and engine speed. Next, the seat vibration was reproduced on the hydrodynamic shaker. Finally, we examined the influence of which order of rotational speed effects evaluation of feeling of pulse in a forced vibration test. As a result, it is known that 0.5th and 1st orders of seat vibration contribute to evaluation of feeling of pulse near 1,500 to 2,000 rpm of engine rotation.
Technical Paper

Prediction of Spindle Force Using Measured Road Forces on Rolling Tire

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.
Technical Paper

A Measures Planning Method by Analysis of Contribution of the Vibration Transfer Path

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.
Technical Paper

Application of Statistical Energy Analysis to Noise Prediction of Co-generation System

This paper describes the application of statistical energy analysis (SEA) to predicting sound power radiated from co-generation system enclosure. To predict vibration and noise accurately by using SEA, it is important to estimate parameter called loss factors. In this study, loss factors were estimated by power injection method. Next, the noise radiated from enclosure surface was predicted by the obtained vibration and radiation efficiency of enclosure panels. As a result, the calculated sound power was relatively corresponding to measured sound power. Finally, the sound power from modified enclosure was predicted. Coupling loss factors related to a modified subsystem were estimated by ratio of the number of structure modes. By using these steps, the noise from the system was reduced.
Technical Paper

Application of Inverse Boundary Element Method to Vibration Identification of Co-generation System

This paper describes the application of inverse boundary element method (Inverse BEM) to vibration identification on surface of Co-generation System enclosure. This method is a kind of matrix inversion using singular value decomposition. Therefore it is significant to select proper tolerance in order to identify vibration accurately. In this study, the tolerance selection method is proposed. First step, the surface velocity of numerical model with unit input was obtained by Finite Element Method. The sound pressure around the model was obtained by BEM. Second step, random noise was mixed with obtained sound pressure. Third step, by using Inverse BEM, the surface velocity was identified from the sound pressure with noise. Next, the error between the identified velocity and the velocity obtained by FEM were evaluated and the tolerance is selected to minimize the error.
Technical Paper

Mode Classification Analysis using Mutual Relationship between Dynamics of Automobile Whole-Body and Components

Current simulation of Noise, Vibration and Harshness (NVH) using Computer Aided Engineering (CAE) often uses a large DOF and detailed finite element model along with improvement of CAE technology and computational performance. By using a detailed model, predictions of precise vibration characteristics become possible. However, the number of eigenmodes in the target frequency range increases and engineers require a lot of time to examine eigenmodes and establish countermeasures. In this paper, a practical method of efficient and effective analysis by classifying target eigenmodes into a small number of groups is proposed. The classification is executed based on the relation between the dynamic characteristics of the entire automotive body structure and substructures.
Technical Paper

Application of Multi-objective Optimization to Exhaust Silencer Design

This paper describes how use of multi-objective optimization of pulsating noise and backpressure improved an exhaust silencer for diesel drive equipment. Low frequency pulsating noise and backpressure were simultaneously predicted using one-dimensional fluid dynamics and acoustic analysis by BEM. In addition, an experiment was done to investigate the relation between high frequency noise including flow-induced noise and the dimensions of perforations in silencer pipes. Finally, a prototype of the exhaust silencer was built and examined in order to confirm the effects of these design methods mentioned. As predicted, exhaust noise was reduced without increasing backpressure.