RESUMO
By experimental methods, 26 specimens were designed to conduct elastic and elastic-plastic buckling tests on cylindrical shells containing cracks. This study discusses the influence of factors such as the length-diameter ratio, the diameter-thickness ratio, the crack length, the inclination of the crack, etc., on the buckling load. Additionally, finite element models were established to compare with experimental results. For the PMMA cylindrical shell, the results showed that as the length-diameter ratio of the cylindrical shell increased, the buckling load first decreased and then increased. For the 6063 aluminum alloy cylindrical shell, with increasing length-diameter ratio, diameter-thickness ratio, and crack length of the cylindrical shell, the buckling load decreased accordingly. However, concerning the crack inclination, as the crack inclination increased, the buckling load increased accordingly. This indicates that the larger the crack inclination, the higher the load capacity of the cylindrical shell containing cracks. Through finite element simulations of cylindrical shells with cracks, it was found that through compressive mechanical properties, both elastic and elastic-plastic buckling loads yielded results that are closer to the experimental results. Additionally, the inclusion of contact effects in numerical simulations further improved the agreement with the experimental results, and the variation trend of the buckling load in the finite element simulation was consistent with the experimental results. The research findings provide valuable references for the assessment of load capacity in structures containing cracks.
RESUMO
OBJECTIVE: To investigate the cardioprotective effects of total saponin from Panax japonicus pretreating on acute myocardial ischemia injury induced by ligating coronary artery left anterior descending branch (LAD) in rats. METHODS: Rats were divided into sham group, model group and total saponin group. The treatment group was given total saponin of Panax japonicus. After pretreating for 7 days, the rats' acute myocardial ischemia model was induced by LAD. The electrocardiogram, hemodynamics, infarct size and histomorphology were assessed 12 h after LAD, the serum levels of phosphokinase (CK), lactate dehydrogenase (LDH), superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) were also measured. RESULTS: Compared with the model group, total saponin from Panax japonicus significantly improved heart function, heart histomorphology, opposed ECG T wave decreased and decreased infarct size; Remarkably decreased the contents of LDH, CK and MDA, increased the activity of SOD, CAT. CONCLUSION: Total saponin from Panax japonicus has cardioprotective effects on acute myocardial ischemic injury and the mechanism may be related to antioxidation.
