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Faculty Mentor

Jikai Du, Fereidoon Delfanian

Abstract

The objective of this paper is to describe the process and results of a residual stress analysis done on a composite cannon barrel. A cross section of a full cannon barrel was cut off to be used in the analysis. The barrel cross section was composed of an inner steel layer that was wrapped in an outer composite layer. The residual stress analysis was done using x-ray diffraction (XRD). The XRD machine uses different types of x-ray tubes based on what material it is analyzing. For this reason, the first portion of the experiment dealt with finding the exact material of the inner steel layer of the barrel. It was concluded that the majority of the barrel was composed of iron. This meant that a chromium x-ray tube had to be used in the XRD machine. Once the material composition was found, the next step was to determine how much the barrel needed to be polished down before accurate readings could be obtained. The reason this is necessary is because the cutting of the barrel would introduce stress into the system through the friction from the blade. By chemically eating away the metal, a depth in the material could be obtained where the residual stress level was not affected by the cutting. The results showed that at a depth of 200 microns or greater, accurate results were obtained. It was also observed that the inner portion of the barrel was in compression while the outer was in tension. Once the barrel was analyzed, the outer composite layer was cut off. It was predicted that the material in the inner steel layer would relax if the outer layer was removed. When placed in the XRD machine, the hypothesis was confirmed. The inner ring of the steel layer went from -396 MPa to -300 MPa, but the residual stress in the outer layer did not change.

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