A linear elastic model of the stress concentration due to contact between a rounded flat punch and a homogeneous substrate is presented, with the aim of investigating fretting fatigue crack initiation in contacting parts of vibrating structures including turbine engines. The asymptotic forms for the stress fields in the vicinity of a rounded punch‐on‐flat substrate are derived for both normal and tangential loading, using both analytical and finite element methods. Under the action of the normal load, P, the ensuing contact is of width 2b which includes an initial flat part of width 2a. The asymptotic stress fields for the sharply rounded flat punch contact have certain similarities with the asymptotic stress fields around the tip of a blunt crack. The analysis showed that the maximum tensile stress, which occurs at the contact boundary due to tangential load Q, is proportional to a mode II stress intensity factor of a sharp punch divided by the square root of the additional contact length due to the roundness of the punch, Q/(√(b − a)√πb). The fretting fatigue crack initiation can then be investigated by relating the maximum tensile stress with the fatigue endurance stress. The result is analogous to that of Barsom and McNicol where the notched fatigue endurance stress was correlated with the stress intensity factor and the square root of the notch‐tip radius. The proposed methodology establishes a ‘notch analogue’ by making a connection between fretting fatigue at a rounded punch/flat contact and crack initiation at a notch tip and uses fracture mechanics concepts. Conditions of validity of the present model are established both to avoid yielding and to account for the finite thickness of the substrate. The predictions of the model are compared with fretting fatigue experiments on Ti–6Al–4V and shown to be in good agreement.
Objective To compare the eBcacy of three diCerent doses groups A to D, respectively. The diCerences were statistically significant only between groups A and C of intravesical interferon a-2b P<0.001). The results were always in favour of the patients treated with the high dose, the only exception bimonthly for the next 4 months and thereafter monthly for 6 months. The patients were followed for being the diCerence between groups C and D (P= 0.026). No side-eCects of the drug were noted, nor 36 months. The four groups were compared for the number of recurrences (simple recurrence rate), prowas any adverse reaction reported from any patient. Conclusion These results show a significant advantage gression in stage, disease-free interval and recurrence rate per 100 patient-months.for adjuvant intravesical IFNa-2b treatment over TUR alone for the 36 months of follow up and indicate Results During the follow-up, 33 patients had recurrence (13, eight, seven and five in groups A to D, that IFNa-2b can modify the clinical course of superficial TCC at least in the short term. The appropriate respectively). The simple recurrence rate was 65% for group A, compared with 36% (P=0.06), 29% dose was apparently 80 MU, for although 40 MU was better than TUR alone, it was less eCective than 60 (P<0.05) and 22% (P<0.01) for groups B, C and D, respectively. The diCerences in simple recurrence rates MU and 80 MU; the 80 MU dose was slightly better than 60 MU and thus this regimen is recommended. between the groups treated with IFNa-2b were not statistically significant. Eleven patients experienced Keywords Interferon, transitional cell carcinoma, immunotherapy, progression, outcome progression in stage, with six, three, one and one in gression occurs in 5-30% of all cases and up to 80% of
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.