Shock and Vibration - Volume 3, issue 1

Article Type: Other

DOI: 10.3233/SAV-1996-3101

Citation: Shock and Vibration, vol. 3, no. 1, pp. iii-iii, 1996

Authors: Mester, Sandor Stephen | Benaroya, Haym

Article Type: Research Article

Abstract: Extensive work has been done on the vibration characteristics of perfectly periodic structures. Disorder in the periodic pattern has been found to lead to localization in one-dimensional periodic structures. It is important to understand localization because it causes energy to be concentrated near the disorder and may cause an overestimation of structural damping. A numerical study is conducted to obtain a better understanding of localization. It is found that any mode, even the first, can localize due to the presence of small imperfections.

DOI: 10.3233/SAV-1996-3102

Citation: Shock and Vibration, vol. 3, no. 1, pp. 1-10, 1996

Authors: Hu, Haiyan

Article Type: Research Article

Abstract: One critical case for the motion of a periodically excited oscillator with continuous and piecewise-linear restoring force is that the motion happens to graze a switching plane between two linear regions of the restoring force. This article presents a numerical scheme for locating the periodic grazing orbit first. Then, through a brief analysis, the article shows that the grazing phenomenon turns the stability trend of the periodic orbit so abruptly that it may be impossible to predict an incident local bifurcation with the variation of a control parameter from the concept of smooth dynamic systems. The numerical simulation in the …article well supports the scheme and the analysis, and shows an abundance of grazing phenomena in an engineering range of the excitation frequency. Show more

DOI: 10.3233/SAV-1996-3103

Citation: Shock and Vibration, vol. 3, no. 1, pp. 11-16, 1996

Authors: Wang, W. J.

Article Type: Research Article

Abstract: The wavelet transform is introduced to indicate short-time fault effects in associated vibration signals. The time-frequency and time-scale representations are unified in a general form of a three-dimensional wavelet transform, from which two-dimensional transforms with different advantages are treated as special cases derived by fixing either the scale or frequency variable. The Gaussian enveloped oscillating wavelet is recommended to extract different sizes of features from the signal. It is shown that the time-frequency and time-scale distributions generated by the wavelet transform are effective in identifying mechanical faults.

DOI: 10.3233/SAV-1996-3104

Citation: Shock and Vibration, vol. 3, no. 1, pp. 17-26, 1996

Authors: Iwatsubo, Takuzo | Kawamura, Shozo | Kamada, Masahito

Article Type: Research Article

Abstract: A new method for reducing ill-conditioning in a class of identification problems is proposed. The key point of the method is that the identified vibration of the sound source is expressed as a superposition of vibration modes. The mathematical property of the coefficient matrix, the practical error expanding ratio, and the stochastic error expanding ratio are investigated in a numerical example. The mode-superposition method is shown to be an effective tool for acoustic-vibratory inverse analysis.

DOI: 10.3233/SAV-1996-3105

Citation: Shock and Vibration, vol. 3, no. 1, pp. 27-37, 1996

Authors: Marcus, Jeffrey H.

Article Type: Research Article

Abstract: Effective thoracic mass is an important parameter in specifying mathematical and mechanical models (such as crash dummies) of humans exposed to impact conditions. A method is developed using a numerical optimizer to determine effective thoracic mass (and mass distribution) given a number of acceleration signals and a force signal response. Utilizing previously reported lateral and frontal impact tests with human cadaveric test specimens in a number of different conditions, the effective thoracic mass is computed. The effective thoracic masses are then computed for a variety of crash dummies exposed to identical test conditions.

DOI: 10.3233/SAV-1996-3106

Citation: Shock and Vibration, vol. 3, no. 1, pp. 39-59, 1996

Authors: Xiong, Ye-Ping | Song, Kong-Jie | Ai, Xing

Article Type: Research Article

Abstract: This article deals with the interaction between wave effects in mounts and resonances of foundations inflexible vibration isolation systems. A new model is proposed that is represented as a rigid mass supported by two linear unidirectional isolators on a flexible foundation beam, whose closed-form solutions for transmissibility and response ratio are then obtained, with which the influence of wave effects coupled with the flexibility of the foundation on the effectiveness of isolation is discussed. The wave effects on flexible isolation systems are analyzed under various parametric conditions and compared with those in rigid systems. In addition, several special cases are …presented to show the transition between various limiting cases. Some approaches to control wave effects are also proposed. Show more

DOI: 10.3233/SAV-1996-3107

Citation: Shock and Vibration, vol. 3, no. 1, pp. 61-67, 1996

Authors: Schramm, Uwe | Pilkey, Walter D.

Article Type: Review Article

Abstract: In the design process structural optimization is a useful tool to reach design decisions. The impact behavior of structures is important for many designs, such as for automobiles. This article reviews methodology for the optimization of structures under impact loading. The optimization problem is to minimize the structural mass with constraints on the transient dynamic response of the structure. The structural behavior is nonlinear dynamic. Optimization is performed using the approximation concept. Design sensitivity analysis for transient response is treated.

DOI: 10.3233/SAV-1996-3108

Citation: Shock and Vibration, vol. 3, no. 1, pp. 69-81, 1996

Article Type: Book Review

DOI: 10.3233/SAV-1996-3109

Citation: Shock and Vibration, vol. 3, no. 1, pp. 83-84, 1996