Papers by Keyword: Rotational Spring Model

Abstract: Structural crack identification has been received considerable attention in recent decade. A lot of different techniques like acoustic emission, ultrasonic, or X-ray, etc have been used for structural crack detection. However, it is still difficult to identify the small crack in structures. A new method for identification of small crack in beam structures using the first anti-resonant frequency curve is proposed in this paper. The method makes use of the driving-point mechanical impedance characteristics of beam structures and a simplified rotational spring model to model the edge crack of beam. After the first anti-resonant frequency curve is obtained, signal process based on wavelet transformation will be carried out and the small crack in beam structures can be explored. The proposed method is validated by a numerical example of cracked beam with pinned-pinned or fixed-free boundary. It is concluded that not only the location of beam crack can be determined, but also the extent of crack damage can be identified qualitatively based on the first anti-resonant frequency curve and wavelet analysis.

Abstract: Crack damage brings a serious threat to the safety of mechanical and civil structures, and the problem of incipient damage identification of structures has been paying attention as a puzzle by many researchers in recent years. To seek for an alternative solution of the problem, a method for incipient crack localization using the slope of the anti-resonance curve is proposed in this paper. The method makes use of the driving-point mechanical impedance characteristics of cracked beams stimulated by harmonic force. To characterize the local discontinuity due to the presence of crack, a simplified rotational spring model is presented to model the crack. Subsequently, the proposed method is verified by a numerical example of cracked beam under simple support or cantilever boundary conditions.

Abstract: Cracks bring a serious threat to safety of structures. Most of the failures and fractures of engineering structures are due to initial cracks or fatigue cracks of materials. So it is very important to analyze the vibration characteristics and to identify the damage of cracked structures. A method for multi-crack identification based on wave propagation is proposed in this paper, which makes use of the driving-point mechanical impedance characteristics of the cracked beams stimulated by harmonic force. The proposed identification method is used to characterize the local discontinuity due to cracks, and a simplified rotational spring model is introduced to model cracks. Subsequently, the proposed method is verified by a numerical example of a simply supported steel beam with three cracks. The effect of crack depth on driving-point impedance is investigated. Combined with the first anti-resonances information, the proposed method can identify the presence of cracks, localize the multiple cracks, and qualitatively identify the extent of the crack damages.