Universal Resonant Ultrasond Spectroscopy For Measuring Elastic Constants

With the development of science and technology,all kinds of new materials are emerging constantly.It is of vital importance to measure the elastic constants of various new materials quickly and accurately,which plays an important role in improving the material properties and ensuring the safety and reliability of the devices.Compared with other material characterization methods,the resonant ultrasound spectroscopy(RUS)has the advantages of high precision,wide application range and no restriction on the shape and size of materials.A hardware for measuring the RUS is designed,and the accurate elastic constants are obtained by inverse calculation using the measured spectroscopy.For hardware design,a method for measuring the RUS is proposed,and the frequency resolution of the RUS is improved.In the software part,the forward calculation method of the eigenfrequency is deduced,and the group theory is used to carry on the modal identification when the spectrum fitting,and the Particle Swarm Optimization(PSO)algorithm is used for optimisation.To ensure the feasibility,the finite element method is used to calculate the RUS and analysize the uncertainty.For bulk materials,the influence of size,preload force and specimen clamping angle on the experimental accuracy is analyzed.The corresponding improvement methods are proposed.For thin films,the existing RUS instrument can not measure the elastic constants of c33,c44,etc.In this paper,a new sample design method is presented,that is,etching a small hole in the sample substrate,thus many film-related resonant modes are artificially constructed.The sensitivity of c33 is improved to 400% from 5%,and that of c44 is improved to 30% from 0.1%Finally,the RUS instrument was built and the experiment is carried out to measure the spectroscopy of the aluminum block with wide band excitation and single frequency excitation respectively.The elastic constants were then calculated by the PSO algorithm.