Research On The Visualization Of NDT Of Solid Rocket Engine Based On ICT

Due to the huge volume and complex structure, the NDT (non-destructive testing) of the solid rocket engine is a difficult problem all along. There are two main traditional methods: one is the ultrasonic method, the other is DR (Digital Radiation) method. The former is most used to check the debonding of the solid rocket engine by receiving the reflected ultrasonic wave and then judging by human beings according the shape of the wave. This method has a number of weaknesses such as random deviation, no quantitative analysis, and a longer testing cycle. The latter is most used to check the crack and slag inclusion inside the solid rocket engine. The acquired information by this method is the one dimension projection data, and the experience of operator himself is needed to determine the size and orientation of the faults. So the second method is also not enough efficient as its dependence of manual subjectivity.ICT (Industrial Computerized Tomography) is one of the best nondestructive detection methods currently, but it hasn't been widely used in the field of nondestructive detection of solid rocket engine. The main reason is that it costs too much time for each detection, so the detection efficiency is lower and the detection cost is too high to endure for manufacturer. Aiming at this problem, we propose an innovative detection schema to reduce the detection time, in which there are two key technologies, one is the image reconstruction based on a few of projections, and the other is the local image reconstruction. The main research contents of this paper are as follows:1. Propose a new detection and image reconstruction schema. The detection schema consists of three main steps. 1) The DR method is used to check roughly whether an abnormity exists. 2) The image reconstruction based on a few of projections is implemented to determine the range of the faults. 3) Through the local high-resolution slice image acquired by the local tomography we can make the ultimate conclusion on the properties of the faults.2. Propose a multicriterion HNN neural network image reconstruction algorithm and a Genetic image reconstruction algorithm based on a few of projections of the solid rocket engine. Normally, image reconstruction from incomplete projections is an ill-conditioned inverse problem which can not be solved by traditional FBP or ART algorithm. However, by adding in advance some constraints, it is converted into a multiple objective optimal problem, and then with a HNN neural networkand a modified genetic algorithm the global optimal solution is gained separately. Typical experiments proved that the reconstruction results of the HNN algorithm is the best in all algorithms considered. 3. Apply the wavelet to local image reconstruction of the solid rocket engine. For the non-local property of Fourier transform, it isn't fit for local image reconstruction (also called ROI, Region of Interesting). On the contrary, the wavelet has a good local property. Adding the multiresolution analysis theory and the fast wavelet transform algorithm, a high-resolution local slice image can be reconstructed by it with the projections passing through a region only slightly larger than ROI.