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Abstract: This paper presents an experimental–numerical analysis of damage localization of concrete plate‐like elements on the basis of hybrid approach. The proposed hybrid approach uses the fast discrete wavelet transform, energy approach, and time of flight criterion for the purpose of localization of single and multidamage problems inside or on the periphery of concrete elements. Verification of the proposed damage localization approach has been performed under laboratory conditions using a laser scanning‐based system with piezoelectric excitation of the wave propagation. Numerical simulation of the wave propagation is performed using the explicit finite element method using 3D models with linear‐elastic material model of concrete with Rayleigh damping. The Rayleigh damping coefficients are determined on the basis of experimental data and implemented in numerical models. Validation of the numerical model is conducted, based on the comparison with sensor output signals obtained through experimental measuring and a very good agreement of results is obtained. The proposed hybrid approach to damage localization is verified using 15 different models/specimens, varying the number, shape (circular or notched), and position of damage, as well as the number and placement of actuators/sensors. For all the analyzed scenarios, the hybrid approach successfully localized the damage even for the least number of used sensor positions. In the models with the circular damage, the damage image created on the basis of the hybrid approach is almost identical to the actual shape of the damage, indicating a good potential of the method for damage localization. [ABSTRACT FROM AUTHOR]

This paper presents the use of metaheuristic optimization techniques to support the improvement of casting process. Genetic algorithm (GA), Ant Colony Optimization (ACO), Simulated annealing (SA) and Particle Swarm Optimization (PSO) have been considered as optimization tools to define the geometry of the casting part's feeder. The proposed methodology has been demonstrated in the design of the feeder for casting Pelton turbine bucket. The results of the optimization are dimensional characteristics of the feeder, and the best result from all the implemented optimization processes has been adopted. Numerical simulation has been used to verify the validity of the presented design methodology and the feeding system optimization in the casting system of the Pelton turbine bucket. [ABSTRACT FROM AUTHOR]

• The hybrid algorithm for defects localization uses two criteria: energy and time of flight. • Approach employs fast discrete wavelet decomposition of output signals. • Hybrid approach is verified by laser based experimental technique. • An explicit FEM has been successfully applied for wave propagation modeling. • The numerical results are in full correspondence with the experimental results. In this paper, the hybrid algorithm for localization of damage and defects is implemented on the concrete plate-like structures for localizing the clay and gypsum inclusions. The hybrid approach employs fast discrete wavelet decomposition of sensor output signals, as well as energy and time of flight criteria. The applied localization algorithm is verified both experimentally and numerically on the concrete plates with one and two inclusions. The experiment is conducted in controlled laboratory conditions, using a piezoelectric actuator for excitation of the wave propagation in the structure, while the ultrasonic laser is used for measuring vibrations at the sensor locations. Numerical simulation of wave propagation is done using the explicit finite element method on 3D models. The numerically obtained results are in full correspondence with the experimental results. The images of material defects positions obtained by the hybrid approach show a good agreement with the actual positions, which indicates a good potential of the used approach in localization of various types of material defects in plate-like concrete structures. [ABSTRACT FROM AUTHOR]