crack identification is a very important issue in mechanical systems, because it is a damage that if develops may cause catastrophic failure. in the first part of this research, modal analysis of a multi-cracked variable cross-section beam is done using finite element method. then, the obtained results are validated usingthe results of experimental modal analysis tests. in the next part, a nove...

this paper presents the effects of geometric tolerances on the rotating shafts natural frequencies. due to modeling the tolerances, a code is written in matlab 2013 software that produces deviated points. deviated points are controlled by different geometric tolerances, including cylindricity, total run-out and coaxiality tolerances. final surfaces and models passing through the points are crea...

determination of allowable free span length plays a crucial role in design of offshore pipelines. the seabed intervention cost and safety of an offshore pipelines project are largely influenced by pipelines free spanning during the project life time. different criteria are proposed by both the current designing guidelines and researchers there is however lack of comprehensive assessment of inde...

in the present paper, the modal analysis on a full finite element model of an off-road vehicle. this vehicle was modeled in the catia software and then meshed in the hypermesh software. the free vibration analysis was conducted by the abaqus software. by applying an external displacement, the forced vibration analysis was also performed. as a result, natural frequencies and shape modes were ext...

wide range of planar structures in new technologies has attracted special consideration. in this research vibration behavior of plates with non-linear edges is investigated by means of finite difference (fd) method. for this issue, classical and analytical solutions for plates with linear edges were analyzed and mutual equations, needed for numerical calculation were extracted. by expanding the...

This paper introduces a perturbative inversion algorithm for determining sea floor acoustic properties, which uses modal amplitudes as input data. Perturbative inverse methods have been used in the past to estimate bottom acoustic properties in sediments, but up to this point these methods have used only the modal eigenvalues as input data. As with previous perturbative inversion methods, the o...

A full-scale seven-story reinforced concrete building section/slice was tested on the NEES shake table at the University of California San Diego during the period of October 2005 to January 2006. Three output-only system identification methods were used to extract the modal parameters (natural frequencies, damping ratios, and mode shapes) of the test structure at different damage states. In thi...

The concept of nonlinear normal modes (NNMs) is discussed in the present paper and its companion, Part II. Because there is virtually no application of the NNMs to largescale engineering structures, these papers are an attempt to highlight several aspects that might drive their development in the future. Specifically, we support that (i) numerical methods for the continuation of periodic soluti...

in the present paper, we are to put forth a paradigm for the systematic study of modality in persian.with this end in view, we consider modality as a linguistic phenomenon that can be expressed at the level of sentence, at the level of constituents smaller than sentence and/or at the level of discourse. in such a system where sentential modality, sub-sentential modality and discourse modality a...