In order to reveal the Lamb wave propagation mechanism, the Lamb wave detection of thin plate structure was investigated numerically. To this end, a finite element model was established and the corresponding boundary conditions, mesh size and time step were set. On this basis, the displacement field was solved and the Lamb wave mode was determined in single plate. Compared with the frequency dispersion curve, the error of numerical results is 1.3%, which proves the validity of the numerical results. In addition, for the bilayer plate, the propagation of the Lamb wave between two mediums could be observed by solving the sound field at different times.
At home and abroad this paper summarizes the present stage of solid missile motor and the loading of the temperature field of research, the analysis of environment includes variable temperature load, surface vessel, warehouse storage for a long time, cooling solidification, by special heat load, etc., the results verify the reliability of the principle, put forward some new model and algorithm formula, and provide certain guiding significance to the reality.
The AU technique is employed in this paper to test the specimen which is made up of composite shell and adiabatic layer; the noise in the tested signal is reduced by adaptive filtering; Multi-resolution analysis of the signal is achieved by wavelet transform. By comparing the ratio of the energy of signal in different frequency zones to the total energy, the characteristic frequency zone of the signal is gained. The characteristic frequency zone of the signal from specimen is evaluated by energy integral Stress Wave Factor (SWF). Flaws are found effectively, and the size of flaw can be evaluated qualitatively. The validity of AU test for bond quality of the structure is approved in the experiments.
High-efficiency pre-cooler is one of the key components of RBCC combined engine. To explore the influence of tube row curvature on heat transfer, a convection heat transfer simulation of pre-cooler composed of different curvature tube rows is established. The model and numerical calculations show that when the curvature is small, the heat transfer efficiency increase slowly with curvature increasing, but the flow resistance increase obviously by increasing curvature. However, when the curvature is large, the effect of curvature increasing on the heat transfer efficiency is obvious and the increase of flow resistance get slower. Based on this, a ring pre-cooler is designed and the heat transfer effect is simulated. It has reference application value for the design of high efficiency pre-cooler.
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