Summary
In this study, an equation is proposed considering Lamb wave motion in a plate in order to estimate the nonlinearity in plate material. The equation evaluates material nonlinearity in terms of amplitudes of the fundamental and second harmonics of Lamb waves. Because the Lamb wave second harmonic can be generated in a nonlinear material through the experiments or simulation, the proposed equation is practically useful to estimate the material nonlinearity. Accordingly, authors carried out experiments on pristine 1100‐H14 Aluminium (Al) specimens using Lamb waves and obtained their inherent material nonlinearity using the amplitude‐based equation. Additionally, authors obtained the value of inherent material nonlinearity in 1100‐H14 Al using the constitutive nonlinear stress‐strain relation containing higher order elastic constants. The material nonlinearity parameters estimated using the experimental results and amplitude‐based equation are then compared with that obtained using the constitutive nonlinear equation. The difference between the results is marginal. Thus, using amplitudes of the fundamental and second harmonics of Lamb waves obtained through the experiments, the proposed amplitude‐based equation can be used to estimate the material nonlinearity in metal plates with fair accuracy.
This study proposes a new parameter to evaluate the material nonlinearity in a thick Aluminum (Al) beam having rectangular cross section using Rayleigh waves. This parameter yields a true value of material nonlinearity using the amplitudes of Rayleigh wave harmonics, in contrast to the relative value yielded by the conventional nonlinearity parameter β′. The Rayleigh wave harmonics are generated in a thick Al 1100 specimen through experiments to estimate its inherent material nonlinearity. This inherent nonlinearity is embedded in the material via lattice elasticity and reckoned using the higher order elastic coefficients. With this experimental investigation, it is found that the accurate evaluation of material nonlinearity is highly dependent on the tone burst cycles in the excitation signal. It is also found that there is a small amount of contribution to the material nonlinearity parameter from the imaginary part of the shear wave component. Furthermore, the relationship between material nonlinearity evaluated using the proposed parameter, excitation frequency, propagation distance, and tone burst cycles in the excitation signal have been unveiled. After knowing these relationships, the material nonlinearity evaluated using the proposed parameter is compared with that obtained from a physics-based nonlinearity parameter containing higher order elastic coefficients. The deviation between the results is minimal. Thus, with the use of amplitudes of harmonics of the Rayleigh wave generated through the experiments, the proposed parameter can evaluate the true material nonlinearity of thick Al beams with fair accuracy.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.