Abstract: The inverse problem of structure damage detection is formulated as an optimization
problem, which is then solved by using artificial neural networks. Based on the hybrid optimization
strategy, the parameter identification algorithm was presented according to the measured data of
vibrating frequency and mode shapes in the damaged structure. The proposed algorithm combines
the local optimum method having fast convergence ability with the neural networks having global
optimum ability. By doing this, the local minimization problem of the local optimum method can be
solved, and the convergence speed of the global optimum method can be improved. The
investigation shows that to identify the location and magnitude of the damaged structure by using
an artificial neural network is feasible and a well trained artificial neural network by
Levenberg-Marquardt algorithm reveals an extremely fast convergence and a high degree of
Abstract: This paper presents an elastostatic crack analysis in three-dimensional (3D), isotropic,
functionally graded and linear elastic solids. A boundary element method (BEM) based on
boundary-domain integral equations is applied. A multi-domain technique and discontinuous
elements at the crack-front are adopted. To show the effects of the materials gradients on the crackopening-
displacements (CODs) and the stress intensity factors (SIFs), numerical results for a pennyshaped
crack are presented and discussed.
Abstract: In this paper the application of the finite element method is presented to modeling
piezoelectric sensors and actuators for use in structural health monitoring of composite panels. It
this demonstrated that FEM can be used to simulate sensorised composite panels and investigate the
damage detection capability of sensors.
Abstract: The instrumented indentation technique (IIT) is a powerful method for evaluating
mechanical properties of materials such as elastic modulus, tensile strength, fracture toughness and
residual stress. Especially, IIT is a promising alternative to conventional methods of residual stress
measurement such as hole drilling, saw cutting, X-ray/neutron diffraction, and ultrasonic methods
because of its various advantages of nondestructive specimen preparation, easy process,
characterization of material properties on local scales and measurement of in-service structures.
Evaluation of residual stress using IIT is based on the key concepts that the deviatoric-stress part of
the residual stress affects the indentation load-depth curve and that the quantitative residual stress in a
target region can be evaluated by analyzing the difference between the residual stress-induced
indentation curve and residual stress-free curve. To verify the applicability of the suggested
technique, indentation tests were performed on the welded zone.
Abstract: This study focused on the determination of fracture toughness by instrumented
indentation technique. A theoretical model to estimate the fracture toughness of ductile materials is
proposed and used to verify those results. Modeling of IIT to evaluate fracture toughness is based on
two main ideas; the energy input up to characteristic fracture initiation point during indentation was
correlated with material’s resistance to crack initiation and growth, and this characteristic fracture
initiation point was determined by concepts of continuum damage mechanics. The estimated fracture
toughness values obtained from the indentation technique showed good agreement with those from
conventional fracture toughness tests based on CTOD. In addition, we confirmed that the proposed
model can be also applied in the brittle material through modification of void volume fraction.