Test Technologies Contributing to Electrification - 6. X-ray CT Nondestructive Measurement Technology Supporting Vehicle Body Weight Reduction TechnologyFig. 8 X-ray spectraFig. 9 Value of POA3.5 Verification of the hypothesisFig. 10 CT images of a test piece of aluminum plates bonded 4. Results of application to weight-reduced togetherpartsThe larger the attenuation coefficient, the greater the attenuation of the X-rays. Fig. 7 indicates that the attenuation coefficient changes with X-ray energy and becomes lower energies. Moreover, the attenuation coefficient of copper increases sharply at the K-absorption edge of 8 keV, and it is approximately eight times higher than that of aluminum. The results lead to the hypothesis that the change in the energy distribution of the incident X-rays is significantly different at lower energies and affects hardening reduction.larger at The X-ray spectra obtained to testly verify the above hypothesis for the aluminum and copper filters are presented in Fig. 8. The thickness of each filter is 1 mm.In Fig. 8, The number of X-ray photons was qualitatively reduced on the low-energy side for both copper and aluminum filters. A comparison of the X-ray spectra for both filters indicates that the number of photons for the copper filter was significantly lower than that for the aluminum filter in the 20–40 keV energy band. The reduced number of photons calculated from the partial over-all (POA) in the 20–40 keV and 80–100 keV energy bands is illustrated in Fig. 9 and is used to quantitatively evaluate the difference in the X-ray spectra.64The reduced number of photons for the copper filter in the 20–40 keV energy band is approximately 3.5 times higher than that for the aluminum filter. By contrast, the number of photons for both filters in the 80–100 keV energy band is 0.1 times less than that for the aluminum filter in the 20–40 keV energy band; this indicates a significant difference in attenuation between copper and aluminum in the 20–40 keV energy band. This result verifies the hypothesis that a change in the energy distribution of incident X-rays in the low-energy band caused by metal filters affects hardening reduction.The relationship between the X-ray energy distribution and CT imaging results was determined to develop a method for selecting an optimal metallic filter. Reliable imaging was realized through an engineering approach that does not rely on the expertise and intuition of the operator. High effectiveness was achieved with new materials that had not been used in the past. Examples of clear visualization of internal structures that were previously difficult to visualize because of image noise are listed and illustrated below.Example 1: The appearance and imaging results of a test piece consisting of aluminum plates bonded with an iron SPR and adhesive are illustrated in Fig. 10. The state (shape) of the adhesive application and the SPR bonding requirements, i.e., the piercing of the upper plate by a rivet, spreading of the rivet leg within the lower plate, and absence of cracks in the lower plate, were evaluated in the three-dimensional structure.Example 2: The imaging results of the multimaterial composite of iron and CFRP are illustrated in Fig. 11. The fiber orientation of the CFRP was observed in iron-mixed materials even when a metal filter was inserted.
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