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J Welch 《Canadian Metallurgical Quarterly》1993,27(2):202-203
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P. PAPANIKOS K. I. TSERPES SP. PANTELAKIS 《Fatigue & Fracture of Engineering Materials & Structures》2003,26(1):37-47
A progressive fatigue damage model has been developed for predicting damage accumulation and life of carbon fibre‐reinforced plastics (CFRP) laminates with arbitrary geometry and stacking sequence subjected to constant amplitude cyclic loading. The model comprises the components of stress analysis, fatigue failure analysis and fatigue material property degradation. Stress analysis of the composite laminate was performed by creating a three‐dimensional finite element model in the ANSYS FE code. Fatigue failure analysis was performed by using a set of Hashin‐type failure criteria and the Ye‐delamination criterion. Two types of material property degradations on the basis of element stiffness and strength were applied: a sudden degradation because of sudden failure detected by the fatigue failure criteria and a gradual degradation because of the nature of cyclic loading, which is driven by the increased number of cycles. The gradual degradation of the composite material was modelled by using functions relating the residual stiffness and residual strength of the laminate to the number of cycles. All model components have been programmed in the ANSYS FE code in order to create a user‐friendly macro‐routine. The model has been applied in two different quasi‐isotropic CFRP laminates subjected to tension–compression (T–C) fatigue and the predictions of fatigue life and damage accumulation as a function of the number of cycles were compared with experimental data available in the literature. A very good agreement was obtained. 相似文献
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R Albrecht TC Awes C Baktash P Beckmann F Berger R Bock G Claesson G Clewing L Dragon A Eklund RL Ferguson A Franz S Garpman R Glasow HA Gustafsson HH Gutbrod J Idh P Jacobs K Kampert BW Kolb P Kristiansson IY Lee H Loehner I Lund FE Obenshain A Oskarsson I Otterlund T Peitzmann S Persson F Plasil AM Poskanzer M Purschke H Ritter S Saini R Santo HR Schmidt T Siemiarczuk SP Sorensen E Stenlund ML Tincknell GR Young 《Canadian Metallurgical Quarterly》1991,44(6):2736-2752
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Because T cells appear to modulate the severity of murine Borrelia burgdorferi infections, we decided to examine the possible involvement of T cell-associated cytokines in disease outcome. Comparison of in vitro B. burgdorferi Ag-induced cytokine production in disease-susceptible and -resistant strains revealed striking differences; spleen cells from susceptible C3H mice produced significantly higher levels of IL-2 and IFN-gamma and lower levels of IL-4 than spleen cells from resistant BALB/c mice. Lymph node responses were even more divergent, with C3H mice producing high levels of IFN-gamma, and BALB/c mice producing little or none. This apparent Th1/Th2 cytokine imbalance was also reflected in vivo, since serum from C3H had significantly higher levels of B. burgdorferi-specific IgG2a Ab and lower levels of IgG1 Ab than serum from BALB/c mice. In vivo studies confirmed the importance of IL-4 in early control of spirochete growth, since treatment of either strain with neutralizing anti-IL-4 mAb led to increased joint swelling and higher spirochete burdens in joints compared with those in control mAb-treated mice. In contrast, IFN-gamma may hinder early control of spirochete growth in susceptible C3H mice, since treatment of mice with neutralizing anti-IFN-gamma mAb reduced both joint swelling and joint spirochete burdens compared with those in control mAb-treated mice. These studies indicate opposing roles for IL-4 and IFN-gamma in the modulation of spirochete growth and disease development in B. burgdorferi-infected mice and suggest that differential cytokine production early in infection may contribute to strain-related differences in susceptibility. 相似文献
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MJ Kania SD Keeling SP McGorray TT Wheeler GJ King 《Canadian Metallurgical Quarterly》1996,66(6):423-432
This study examined risk factors associated with incisor injury in 3396 third and fourth grade school children in Alachua County, Florida. One of six orthodontists completed a standardized examination form for each child to assess severity of incisor injury, gender, age, race, skeletal relationships, morphologic malocclusion, incisor exposure, interlabial gap, TMJ sounds, chin trauma, and history of lower facial trauma. One in five (19.2%) exhibited some degree of incisor injury. This was limited to a single tooth in 73.1% of those with injury, while enamel injury predominated (89.4%). The majority of the injuries (75.4%) were localized in the maxillary arch, with central incisors the most frequently traumatized. Chi-square tests of association indicated that gender, race, school, orthodontist, history of lower facial trauma, chin trauma, profile, and maxillary and mandibular horizontal positions were associated with incisor injury (P < 0.05). Wilcoxon rank sum tests identified differences in age, overjet, time of screening, and interlabial gap between those with and without injury (P < 0.05). Results of logistic regression analyses indicated risk of incisor injury was greater for children who had a prognathic maxilla, a history of trauma, were older, were male, and had greater overjet and mandibular anterior spacing. 相似文献
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