Measure The Tangential Stress L <sub> Cr </ Sub>-wave Emissions, The Study Of The Communication Process

The stress state of accessory which relates to machining process and manufacture methods,is the integrative result of its past and current operating state and the key indicators to evaluate the safety and reliability of products.Besides,stress key parameter leads to performance of products of precision measurement mechanical system and is the proof of analysis,design and optimization of accessory.The evaluaiton of stress distribution of material or accessory not only is the basic method to analysis of material performance and stress state,but also is the way to estimate fatigue condition and inspect heat treatment, the surface process,machining technics.The experiment stress measurement especially non-destructive stress measurement techniques has been the very important research field in the engineering, in particular in the machine, space navigation, traffic, national defence and nuclear engineering,etc.Based on the acoustoelastic theory,some parameters of ultrasonic in solid will vary with the stress.The special condition is needed to measure stress with bulk or surface wave so that the acoustoelastic method is still limited in several application.Critically Refracted Longitudinal (LCR) wave is the ultrasonic formed by the incidence of longitudinal wave with the first critical angle on the interface.The merit of the LCR wave which propagates under the surface suggests LCR wave is suit to measure parallel stress from the surface of the accessory and enlarges the adaptive range of stress measurement with ultrasonic.According to acoustoelastic stress measurement theory and the stress measurement expeiment model with LCR wave, based on the acoustoelastic theory and finited element method(FEM), the study of the conversion of wave models,the influence of the angle of reflection and refraction to energy distribution and the simulation of propagation of LCR Wave is involed in this paper.Firstly, according to critically refracted angle from material parameters,the FEM model is constructed,the excitation, propagation and receiving of LCR wave in the medium is simulated with FEM. Propagation mechanism of LCR wave is basically discussed and cause about more incidental waves forming in the propagation course is analysed.Then,the energy distribution of critically refraction related to the angle which is used to explain that LCR wave will be excited in a certain range of critical angle,is analysed,all of these explain the results from stress measurement. experiments.Lastly,the analysis of the propagation time of ultrasonic in the medium show that the first received wave is LCR wave in the series receiving waves on wedge.The result is theoretically helpful to treat with the series waves in the future research about stress measurement system with LCR wave.