Abstract
Under harsh environment or during service, the mechanical properties of materials or structure will deteriorate. Most of the simulations exhibit the phenomenon of nonlinearity by introducing the actual small defects, without considering dislocation. In this manuscript, subroutines are written to change the mechanical constitutive behaviour of materials. When the mechanical constitutive behaviour of the material is not linear any more, it is found that the propagation of ultrasonic wave in the material will show more obvious nonlinear phenomenon. Furthermore, the nonlinear detection coefficient is used to characterize the increase of harmonic components. This work provides a new idea for nonlinear ultrasonic testing.
Highlights
Since structure under periodic load or in harsh environment, no matter what materials, will undergo material properties degradation
Few researchers simulate the interact between microscopic dislocations and ultrasound. Most scholars ignore this earlier dislocation stage and study crack directly, like Ref [2, 3, 6, 8, 18, 19, 21]. This manuscript simulates the damage before cracks appear and conclude that ultrasound can already reflect early dislocations of material damage, which will be an important guarantee for nondestructive evaluation (NDE) in military and aerospace
The remainder of this manuscript is organized as follows: Section 2 introduces the basic theoretical background of nonlinear ultrasound and higher harmonics generation in theory and constitutive behaviour which are written for simulations
Summary
Since structure under periodic load or in harsh environment, no matter what materials, will undergo material properties degradation. Cantrell[17] et al proposed a new model of ultrasonic to interact with dislocation dipoles and dipole arrays for exciting second harmonics They believed that when the dislocation is dense, the amplitude of the second harmonic of the ultrasound is related to the length and stress of the dislocation lines, and largely influenced by the arrangement of dislocations in the structure. This manuscript simulates the damage before cracks appear and conclude that ultrasound can already reflect early dislocations of material damage, which will be an important guarantee for NDE in military and aerospace The remainder of this manuscript is organized as follows: Section 2 introduces the basic theoretical background of nonlinear ultrasound and higher harmonics generation in theory and constitutive behaviour which are written for simulations.
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