Study Of Ultrasonic Stress Measurement Results

Stress evaluation with ultrasonic is real-time and non-destructive, so the method has a broad application prospects. But it is affected by many factors, such as texture, residual stresses, temperature and transverse strain. The purpose of this thesis is to analyse this factors in order to minimize the measurement errors. In such a way, stress evaluation with ultrasonic is more precise and more effective guidance to engineering practice.In this thesis, sing-around method is used which can measure ultrasonic velocity precisely, and experimental material is 45 steel. In this experiment, which use ultrasonic shear wave acoustic birefringence as main testing methods and longitudinal wave secondary. In the nature state, analyzing influence factors of texture and temperature on acoustic elasticity. The test specimens go through heat treatment in a specific temperature and holding a certain time. The purpose of heat treatment is to refinement material texture and reduced residual stress. Then evaluate acoustical anisotropy with ultrasonic shear wave and longitudinal wave. The results show that acoustical anisotropy of the test specimens is different. The result also show that the specimen with 650℃heat preservation 40 minute have smaller acoustical anisotropy than other specimens, but the specimen with 650℃heat preservation 100 minute have the biggest acoustical anisotropy. In order to prove the measurement results, analyzing microstructure of 45 steel with different heat treatment through metaloscope. Then choose a test specimen to measure ultrasonic shear wave velocity and longitudinal wave velocity at different temperatures which can analyze temperature influence on the velocity. So can eliminate errors caused by environmental factors according to velocity amendment.In the uniaxial loading state, choosing specimens whose acoustical anisotropy is small according to test results in the natural state for loading experiments. Relationship between acoustical anisotropy and stress is discussed according to loading results. Evaluating stress under the premise of minimizing texture influence. Then analyzing transverse strain influence factor, and not only deducts final theory formula but also verifies through experiments. In such a way, stress evaluation with ultrasonic is more precise, and can provide a reference for engineering practice.This thesis mainly research related influence factors on stress evaluation in the the natural state and under uniaxial stress, and improve the accuracy of stress evaluation through eliminating texture influence factor and temperature influence factor, evaluating residual stress influence factor, and amending result errors which caused by transverse strain. In such a way, the technology can be applied to production practice. Stress evaluation with ultrasonic has a broad application prospects.