Modeling and simulation of vibro-thermography including nonlinear contact dynamics of ultrasonic actuator.

In this paper, a thermodynamically consistent generalized three-dimensional modeling scheme is developed to simulate vibro-thermography and subsequently perform a quantitative investigation on a test structure. Simulation results are analyzed considering a plate with Structural Features (SF) which are used in a gas turbine engine structural components to reduce structural mass and enhance cooling. The modeling framework includes (i) coupled thermo-elastic heat generation and (ii) effects of various sources of nonlinear vibration arising due to the amplitude of the excitation, the engagement force on the target structure due to the ultrasonic horn, and structural boundary conditions. Transient heat generation behavior in the target structure with SF is analyzed. Dynamic contact models are used to capture the nonlinear harmonics. The effects of engagement force on the dynamic response are analyzed. Simulation results are obtained by incorporating the model in a finite element scheme. The simulation results show that the thermographic inspection can be optimally designed using a relationship between the SF sizes with reference to wavelength based resonance phenomenon. The spectral components obtained at various locations in the SF reveals the presence of both sub- and super-harmonics.