Search Results

Squeak and rattle (S&R) problems in body structure and trim parts have become serious issues for automakers because of their influence on the initial quality perception of consumers. In this study, various CAE and experimental methods developed by Hyundai Motors for squeak and rattle analysis of door systems are reported. Friction-induced vibration and noise generation mechanisms of a door system are studied by an intelligent combination of experimental and numerical methods. It is shown that the effect of degradation of plastics used in door trims can be estimated by a numerical model using the properties obtained experimentally. Effects of changes in material properties such as Young's modulus and loss factor due to the material degradation as well as statistical variations are predicted for several door system configurations. As a new concept, the rattle and squeak index is proposed, which can be used to guide the design.

This paper describes the optimal design process of the steering column system and the supporting system. At the initial concept stage of development process, a design guide is proposed to obtain sufficient stiffness of the steering system while reducing idle vibration sensitivity of the system. Case studies on resonance isolation are summarized, in which separated vibration modes among systems by applying Vibration Mode Map at the initial stage of design process. This study also makes it possible to provide design guideline for optimal dynamic damper system using CAE (computer aided engineering) analysis. The damper FE (finite element) model is added to vehicle model to analyze the relation between the frequency and the sensitivity of steering column system. This analysis methodology enables target performance achievement in early design stage and reduction of damper tuning activity after proto car test stage.

Design optimization of a vehicle is required to increase a product value for noise and vibration performances and for a fuel-efficient car. This paper describes the development process of a high stiffness and lightweight vehicle. A parameter study is carried out at the initial stage of design using the mother car, and a design guide with a good performance is achieved early prior to the development of the proto car. Influences of body stiffness based on the relative weight ratio of the floor and side structures are analyzed. Results show that bending and torsional stiffness has a significant effect on weight distribution ratio. Influences of the distribution of side joint stiffness are analyzed through numerical experiments. Results reveal that the stiffness difference between the upper and lower parts should be small to increase the stiffness of a body.

With the recent development of technologies for interpreting vibration and noise of vehicles, it has become possible for carmakers to reduce idle vibration and driving noise in the phase of preceding development. Thus, the issue of noise generation is drawing keen attention from production of prototype car through mass-production development. J. D. Power has surveyed the levels of customer satisfaction with all vehicles sold in the U.S. market and released the Initial Quality Study (IQS) index. As a growing number of emotional quality-related items are added to the IQS evaluation index, it is necessary to secure a sufficiently high quality level of low-frequency speaker sound against rattle noise. It is required to make a preceding review on the package tray panel, which is located at the bottom of the rear glass where the woofer speakers of a passenger sedan are installed, the door module panel in which the door speakers are built.

The analytic wavelet transform (AWT) is a wavelet transform that works much like a transient Fourier transform. Therefore the AWT enables utilizing advantages of both the wavelet transform and Fourier transform. A special form of AWT developed for transient vibration and acoustics signal analyses is applied to various engineering signals in this paper. Application examples include a general time-frequency (T-F) analysis, analysis of exposures to impulsive vibrations and noises, and estimation of reverberation times. Some new definitions such as the T-F noise reduction and frequency weighted time history are defined by taking the advantage of unique capabilities of the AWT. Possible automotive applications of these new concepts are briefly discussed.

In highly transient sounds, time and frequency components are highly dependent of each other. A time-frequency (T-F) analysis is necessary for such signals. The wavelet transform is a T-F signal analysis algorithm which uses variable scales to satisfy both time and frequency resolution requirements more effectively. The analytic wavelet transform (AWT) is a wavelet transform that retains most of the basic features of the Fourier transform. We developed a form of AWT specifically made for acoustics applications. The method obtains the amplitude as well as phase of the sound signal as the Fourier transform does, however in the transient sense. Advantages of the method over the short time Fourier transform method, a commonly used Fourier transform based transient signal analysis method, are demonstrated using two impulsive signals as examples.

Two potential applications of a dynamic stiffness matrix (DSM) based direct damping matrix identification method are presented in this paper. The method was proposed to identify both the mechanism and spatial distribution of damping as a matrix of general function of frequency. First potential application is the analytical-experimental hybrid structural dynamics modeling, in which the model is constructed by combining analytically formulated mass and stiffness matrices with the experimentally identified damping matrix. Second application is the direct measurement of complex shear modulus of viscoleastic materials. The real and imaginary parts of the dynamic stiffness measured on a test setup that resembles a single degree of freedom system is used to compute the shear modulus and the loss factor of viscoelastic materials.

This paper is intended to describe some of the advances in automotive NVH research and applications based on recent developments in the Structural Dynamics Research Laboratory (SDRL) at the University of Cincinnati. State-of-the-art vibro-acoustic research capabilities and infrastructure ranging from advanced vibration modal analysis and spectral techniques for linear and nonlinear automotive systems to computational tools for structure-borne acoustic noise generation, transmission and synthesis problems are discussed. These systems have been devised with the intent of integrating a versatile set of experimental, computational and analytical approaches in order to be able to investigate a variety of crucial automotive NVH concerns. The materials will be grouped into three separate but closely related sets of applications consisting of (i) powertrain noise and vibration control, (ii) analysis and control vehicle system dynamics, and (iii) NVH and sound quality.

A new algorithm to detect and to quantify the seriousness of the detected squeak and rattle (S&R) events was developed. A T-F analysis technique called AWT, the Zwicker loudness model and leaky integration are employed to define new concepts we called transient specific loudness time histories and perceived transient loudness time history. The detection threshold of the perceived transient loudness was identified by a clever interpretation of jury test results. The proposed algorithm showed a good promise producing results that are well correlated with the jury tests. The new algorithm developed in this work will be able to automate detection and rating of the S&R events with good accuracy and with minimum possibility of false alarm under normal operating conditions

Squeak and rattle (S&R) noises are undesirable noises caused by friction-induced vibration or impact between surfaces. While several computer programs have been developed to automatically detect and rate S&R events over the years, no reported work has been found that can detect squeak and rattle noises and distinguish them. Because the causes of squeak noises and rattle noises are different, knowing if it is a squeak noise or rattle noise will be very helpful for automotive engineers to choose an appropriate measure to solve the problem. The authors have developed a new algorithm to differentiate squeak noises and rattle noises, and added it to the S&R detection algorithm they had developed previously. The new algorithm utilizes a combination of sound quality metrics, specifically sharpness, roughness, and fluctuation strength.

Despite tremendous advances in modern computational technology, there still remain many engineering problems that do not allow numerical solutions of reasonable accuracy. In many of these problems the main difficulty stems from lack of our ability to accurately model damping. Such examples are simulation of structure-borne noise, stability analysis of dynamic systems and numerical prediction of fatigue failure. In these problems small difference in damping description results in a completely different solution, while the current state of the art of damping modeling cannot provide such accuracy. A new concept proposed by one of the authors [1,2], which uses the dynamic stiffness matrix (DSM-the inverse of a frequency response function matrix), is studied in this two-part paper. Advantages of the method and practical issues to overcome are discussed in both papers. The method obtains the damping model directly from measured data; and is independent of classical damping models.

Despite tremendous advances in modern computational technology, there still remain many engineering problems that do not allow numerical solutions of reasonable accuracy. In many of these problems the main difficulty stems from lack of our ability to accurately model damping. Such examples are simulation of structure-borne noise, stability analysis of dynamic systems and numerical prediction of fatigue failure. In these problems small difference in damping description results in a completely different solution, while the current state of the art of damping modeling cannot provide such accuracy. A new concept, which had been proposed by one of the authors as a potential break-through for damping modeling, is studied in this two-part paper. Advantages of the method and practical issues to overcome are discussed in both papers. The method obtains the damping model directly from measured data; therefore is completely independent of classical damping models.

The transfer function synthesis method is one of the most powerful methods in analyzing the responses of complex built-up structures under high modal density. Its superiority mostly comes from the ability to incorporate experimental FRFs into the formulation. In this paper, a general procedure for the design sensitivity analysis of vibro-acoustic problems has been presented in frame of the transfer function synthesis method. For an acoustic response function, the proposed method gives a parametric design sensitivity expression in terms of the partial derivatives of the connection element properties and the transfer functions of the substructures. As a realistic problem, an interior noise problem in a passenger car is analyzed. The proposed noise sensitivity formulation calculates the interior noise variations with respect to the changes of the dynamic characteristics of the engine mounts and the bushes.

An air-conditioner compressor-mounting bracket is a structural component of an engine, on which bolts attach an air-conditioner compressor. In this paper, the shape of the air-conditioner compressor-mounting bracket of a passenger car is optimized using a finite element software, and the optimized bracket is manufactured and verified by tests. An objective function for the shape optimization of the bracket is the weight of the bracket. Two design constraints on the bracket are the first resonant frequency of the compressor assembly and the need not to fracture during the workbench durability test. The compressor assembly, which consists of a compressor, a bracket and connection bolts, is modeled using finite elements. The bracket is modeled by solid elements and the swash-plate-type compressor is represented by rigid masses and beam elements in order to consider the elastic effects of the compressor.

It is common knowledge that body structure is an important factor of road noise performance. Thus, a high stiffness of body system is required, and determining their optimized stiffness and structure is necessary. Therefore, a method for improving body stiffness and validating the relationship between stiffness and road noise through CAE and experimental trials was tested. Furthermore, a guideline for optimizing body structure for road noise performance was suggested.