Natural frequency changes due to damage in composite beams

11th International Conference on Damage Assessment of Structures

物理学;材料科学

Negru, I.^1 ; Gillich, G.R.^1 ; Praisach, Z.I.^1 ; Tufoi, M.^1 ; Gillich, N.^2

Department of Mechanical Engineering, Eftimie Murgu University of Resita, P-ta Traian Vuia 1-4, Resita

320085, Romania^1

Department of Electrical Engineering, Eftimie Murgu University of Resita, P-ta Traian Vuia 1-4, Resita

320085, Romania^2

关键词: Damage location;    Frequency shift;    Mode shape curvatures;    Multi-layer beam;    Reference curves;    Transversal cracks;    Transverse mode;    Transverse vibration modes;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/628/1/012091/pdf
DOI  :  10.1088/1742-6596/628/1/012091

学科分类：材料科学（综合）

来源: IOP

【 摘 要 】

Transversal cracks in structures affect their stiffness as well as the natural frequency values. This paper presents a research performed to find the way how frequencies of sandwich beams change by the occurrence of damage. The influence of the locally stored energy, for ten transverse vibration modes, on the frequency shifts is derived from a study regarding the effect of stiffness decrease, realized by means of the finite element analysis. The relation between the local value of the bending moment and the frequency drop is exemplified by a concrete case. It is demonstrated that a reference curve representing the damage severity exists whence any frequency shift is derivable in respect to damage depth and location. This curve is obtained, for isotropic and multi-layer beams as well, from the stored energy (i.e. stiffness decrease), and is similar to that attained using the stress intensity factor in fracture mechanics. Also, it is proved that, for a given crack, irrespective to its depth, the frequency drop ratio of any two transverse modes is similar. This permitted separating the effect of damage location from that of its severity and to define a Damage Location Indicator as a sequence of squared of the normalized mode shape curvatures.