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[en] Reassessment of past ASME N-47 creep-fatigue rules have been under way by committee members. The new proposed elastic creep-fatigue methods are easier to apply than those previously in the code case. They also provide a wider range of practical application while still providing conservative assessments. It is expected that new N-47 code rules for elastic creep-fatigue evaluation will be adopted in the near future
[en] The elastic field of a semi-infinite wedge crack and its interaction with a screw dislocation under mode III loading conditions are examined. The stress field around the wedge crack is expressed in terms of a wedge stress intensity factor. The rate of falloff of the stress field with distance from the crack tip is found to be a function of the wedge angle. The relationship between the stress intensity factors for the wedge and sharp cracks is derived and used to estimate the magnitude of stress relaxation occurring at the crack tip due to crack blunting. The crack extension force for the wedge crack is calculated and is shown to be zero. The modifications in the stress field and the local wedge stress intensity factor due to the presence of the dislocation are calculated. From the image stress on the dislocation, the condition for the emission of dislocations from the wedge crack is obtained in terms of the critical wedge stress intensity factor for dislocation generation. It is found that the emission of dislocations from the crack tip is more difficult when the crack is blunting
[en] Patient-centred practice and increasing user involvement adds impetus to built environmental research within the health care setting. Much work has been centred around stress reduction initiatives for improving health outcomes for patients and staff. This study examined the influence of music choice on patients' anxiety levels whilst seated in a radiotherapy waiting area. Patients' stress levels and perceptions were assessed in the absence/presence of music. The opinions of patients were elicited through a questionnaire following exposure to a range of music types. Music therapy was shown to have clear benefits when individuals enjoyed the music to which they listened. Although clear preferences were indicated, the results were skewed by the negative effects of music not enjoyed by patients. Further investigation needs to take account of the impact of personal variables and the value of 'quiet areas'
[en] Reliability requirements of the system equipment under long-term storage are put forward especially for the military products, so that the connectors in the equipment also need long-term storage life correspondingly. In this paper, the effects of stress relaxation of the elastic components on electrical contact of the connectors in long-term storage process were studied from the failure mechanism and degradation models. A wire spring connector was taken as an example to discuss the life prediction method for electrical contacts of the connectors based on stress relaxation degradation under long -term storage. (paper)
[en] A series of experiments to monitor the aging performance of Viton® GLT and GLT-S O-rings used in the Model 9975 shipping package has been ongoing since 2004 at the Savannah River National Laboratory. One approach has been to periodically evaluate the leak performance of O-rings being aged in mock-up 9975 Primary Containment Vessels (PCVs) at elevated temperature. Other methods such as compression-stress relaxation (CSR) tests and field surveillance are also on-going to evaluate O-ring behavior. Seventy tests using PCV mock-ups with GLT O-rings were assembled and heated to temperatures ranging from 200 to 450 °F. They were leak-tested initially and have been tested periodically to determine if they continue to meet the leak-tightness criterion defined in ANSI standard N14.5-97. Due to material substitution, a smaller test matrix with fourteen additional tests was initiated in 2008 with GLT-S O-rings heated to temperatures ranging from 200 to 400 °F. Leak test failures have been experienced in all of the GLT O-ring fixtures aging at 350 °F and higher temperatures, and in 8 fixtures aging at 300 °F. The 300 °F GLT O-ring fixtures failed after 2.8 to 5.7 years at temperature. The remaining GLT O-ring fixtures aging at 300 °F were retired from testing following more than 5 years at temperature without failure. No failures have yet been observed in GLT O-ring fixtures aging at 200 °F for 9 to 10.5 years, or in GLT O-ring fixtures aging at 270 °F for 5.7 years. These aging temperatures bound O-ring temperatures anticipated during normal storage in K-Area Complex (KAC). Leak test failures have been experienced in all of the GLT-S O-ring fixtures aging at 300 °F and above. No failures have yet been observed in GLT-S O-ring fixtures aging at 200 and 250 °F for 6.9 to 7.5 years. Data from the O-ring fixtures are generally consistent with results from compression stress relaxation testing, and provide confidence in the predictive models based on those results. However, uncertainty still exists in extrapolating these elevated temperature results to the lower temperatures of interest for normal storage in KAC. Measurement of compression set in O-rings removed from failed fixtures, compared to that from KAC surveillance O-rings, indicates margin remains for O-rings still in service. Aging and periodic leak testing will continue for the remaining PCV fixtures.
[en] This paper reports the effect of low-temperature vacuum anneling on Terfenol-D samples made by the Reduction-Diffution (RD) method. It was expected that the hidri dephase previously present in the sample could be removed by the anneling. The anneling was done at 200 C, under dynamic vacuum for 8 hours. The pelletised samples were wrapped in Ta-foil then placed in a glass tube tube tugether with a pure Titanium getter. The XRD data analyses show several results: first, the FWHM values o peak of annealed samplesare smaller than those of samples before anneling. This might be due to internal stressre lieving, since at that temperature, the diffusion is not favorised yet. Second, the hidride phase could be removed by anneling. Third, for certain samples, it was observed a shift of position of the main phase's peaks to a bigger 20 angle, meaning that main phase initially contained a tiny amount of hydrogen, somting which had not been detectedyet. In conclusion, the low-temperature vacuum annealing has positive effect on Terfenol-D samples, and can be concidered as an important modification of the RD technique
[en] The 9975 shipping package is used within the DOE complex for shipping special nuclear materials. The shipping packages are currently approved for up to 20 years storage in K-Area Complex (KAC) and work continues to provide technical basis to extend that period. Several techniques have been used at Savannah River National Laboratory to monitor the aging performance of Viton ® GLT or GLT-S fluoroelastomer O-rings. These experiments all involve accelerated aging of the O-ring samples at elevated temperatures. This report describes efforts to extend the service life estimate of GLT and GLT-S O-rings used in the 9975 shipping package.