Abstract
Nonuniform microcrack identification is of great significance in mechanical, aerospace, and civil engineering. In this study, the nonuniform crack is simplified as a semielliptical crack, and simplified calculation methods are proposed for damage severity and damage identification of semielliptical cracks. The proposed methods are based on the calculation method for uniform cracks. The wavelet transform and the intelligent algorithm (IA) are used to identify the damage location and the damage severity of the structure, respectively. The singularity of the wavelet coefficient can be used to identify the signal singularity quickly and accurately, and IA efficiently and accurately calculates the structural damage severity. The particle swarm optimization (PSO) algorithm and the genetic algorithm (GA), widely used, are applied to identify the damage severity of the beam. Numerical simulations and experimental analyses of beams with transfixion and semielliptical cracks are carried out to evaluate the accuracy of the semielliptical crack calculation method and the method of wavelet analysis combined with PSO and GA for nonuniform crack identification. The results show that the wavelet-particle swarm optimization (WPSO) and the wavelet-genetic algorithm (WGA) can accurately and efficiently identify the structural semielliptical damage location and severity and that these methods are not easily influenced by noise. The damage severity calculation method for semielliptical cracks can accurately calculate the semielliptical size and can be used to identify damage in beams with semielliptical cracks.
Highlights
In the field of aerospace, mechanical engineering, and civil engineering, the damaged component will appear fatigue failure under long-term load, which has a huge impact on safety of structure. erefore, the structural damage identification and life prediction are of great significance and importance
Due to the complexity of nonuniform crack damage identification, two methods are proposed: (1) a method to identify the structural nonuniform microdamage based on the wavelet-intelligent algorithm and (2) a simplified calculation method for nonuniform crack based on fracture mechanics
By simplifying the nonuniform microcrack into a semielliptical crack, the relationship between the damage severity of the semielliptical crack and the semiminor axis of the crack can be obtained by mathematical derivation and fitting. e validity and accuracy of the crack damage identification method based on the wavelet-intelligent algorithm are verified by notch damage identification
Summary
In the field of aerospace, mechanical engineering, and civil engineering, the damaged component will appear fatigue failure under long-term load, which has a huge impact on safety of structure. erefore, the structural damage identification and life prediction are of great significance and importance. Guedria [24] defined the damage identification of plate structure as a nonlinear optimization problem and calculated the minimum value of the constructed objective function with the accelerated differential evolution (ADE) algorithm so as to accurately identify the damage location and severity of plate structure. E results of numerical simulation and experimental analysis show that the combination of wavelet and GA can effectively and accurately identify the structural damage location and severity and can be applied to the damage identification of the engineering structure. E calculation method for the damage size of beams with semielliptical cracks is verified by numerical simulations and experiments; the results show that the proposed method is of high accuracy and can be used effectively for semielliptical cracks calculations in engineering structures The damage severity of transfixion cracks is calculated firstly, and the damage severity of beams with semielliptical surface cracks is defined using the same moment of inertia (assuming that the damage severity is the same). e wavelet is combined with PSO and GA to identify the damage severity of beams with nonuniform cracks, respectively, and the semielliptical crack size is calculated based on the identified damage severity. e validity and accuracy of the crack damage identification method (based on the wavelet-intelligent algorithm) are verified by notch damage identification. e calculation method for the damage size of beams with semielliptical cracks is verified by numerical simulations and experiments; the results show that the proposed method is of high accuracy and can be used effectively for semielliptical cracks calculations in engineering structures
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