uniform adhesion of rosette gages to the surface. Some spots under the foil gage may not be bonded as strong as other spots. At large strain, the foil gage tends to debond locally and results in errors in measured strain. However, at low strain amplitudes, it is believed that the strain gages reading will closely represent the average strain of the tube surface under internal pressure. The internal pressure in this study is generated using a piston-type hydraulic pressure generator (Model 37-6-30 from High Pressure Equipment Co. Erie PA) that feeds hydraulic oil into flexible rubber tubing placed within the SiCf-SiCm sample tube. Loading-unloading tests were performed using a SiCf-SiCmsample tubes. During the test the internal pressure was increased by displacing the high pressure cylinder shaft of the hydraulic pressure generator, from zero to a predetermined internal pressure and then decreasing to zero, completing a cycle. The loading-unloading continues for the next predetermined internal pressure. Each loading-unloading cycle is achieved in less than 60 s to reduce the effect of slow crack growth. The internal pressure was varied in the range of 6.9 MPa (1,000 psi) to 96.5 MPa (14,000 psi), the pressure was monitored with an analog pressure gage. Simultaneously images of the SiCf-SiCm sample tube were acquired with CCD cameras. These images were later used to calculate the strains on the outside surface by DIC method. Data from the strain gages attached to the aluminum adapters was recorded during the experiment using a NI-cDAQ-9172 chassis with two NI9237 modules and LabView software. To detect the evolution of damage within the SiCf-SiCmsample tube, the signal from AE sensor was recorded for posterior analysis. The AE equipment is a Micro-II Digital AE System (Physical Acoustics Corporation) equipped with a NANO-30 AE sensor and 60 DB pre-amplifier. The data was analyzed using the AEWin software. The AE sensor (NANO-30) was coupled to the sample with play dough and held in place by rubber band. The digital image correlation (DIC) method is applied to measure the surface strains. DIC is a non-contact full-field strain measurement technique with a broad range of applications [11]. Due to the curved nature of the sample, three-dimensional DIC method enabled by two cameras is used. Two CCD cameras from Point Grey (GRAS-30S5M) are used for image acquisition. Figure 46.2 shows the spatial arrangement of the cameras with respect to the sample. The camera-to-sample Fig. 46.1 Speckle pattern (1) and strain gages installed in sample; Sample without speckle pattern (2) Sample Fluorescent light Fluorescent light 22o Fig. 46.2 Position of cameras respect to sample 46 High Pressure Burst Testing of SiCf-SiCmComposite Nuclear Fuel Cladding 389
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