A contrast between classical method and finite element method for calculating strength in impeller of centrifugal pump

In order to calculate accurately the stress and the deformation conditions of the closed impeller of centrifugal pumps in the flow field, “direct-calculation method” and the ANSYS Workbench-based finite element method are separately used to calculate the maximum stress that the impeller bears and the strength check of it have been proceed. This paper has made a comparative analysis between the two methods, and it is shown that the finite element analysis method can more comprehensively show the stress concentration, whereas the traditional method is more focused on the average of checking. Therefore, in terms of the results, it is suggested that in addition to the traditional direct-calculation method, modern simulation software such as the finite element method should be used for the proofread of the impeller in the industry, in order to improve the running safety and the reliability of the closed impeller of centrifugal pumps

Modelling the electromagnetic separation of non-metallic particles from liquid metal flowing through a two-stage multichannel

A two-stage multichannel was designed to increase the efficiency of separating non-metallic particles from liquid metal flowing through an alternating magnetic field. Numerical method was developed to calculate the particle concentration and separation efficiency of a zinc melt containing dross particles and verified by the experimental results. The distribution of particle concentration and axial fluid velocity changed significantly due to the added walls in the sub-channel, resulting in an abrupt increase in the residence time of the inner bulk melt with high particle concentrations and a remarkable increase in particle separation efficiency when flowing through the single-channel to sub-channels. A multistage and multichannel arrangement is hence recommended for further increase in the separation efficiency of an electromagnetic separator

Evaluation of Trichogramma ostriniae (Hymenoptera: Trichogrammatidae) as a biological control agent against the European corn borer, Ostrinia nubilalis (Lepidoptera: Pyralidae): Biological, behavioral and ecological perspectives

The biology and behavioral ecology of Trichogramma ostriniae, an introduced egg parasitoid of Ostrinia nubilalis and other lepidopteran species were studied in the laboratory and under field conditions. The inter- and intra-specific discrimination, competition, and the effectiveness of T. ostrinia and T. nubilale were also investigated. For T. ostriniae to complete its life cycle, it took 6.7 days at 33\sp\circC and 20 days at 17\sp\circC. Comparison of several theoretic models indicated that a transformed day-degree model and the Hilbert-Logan model were better for predicting the development of this parasitiod. The wasps reared on O. furnacalis by the seventh generation and at 27\sp\circC had a lower level of parasitism than wasps from other generations and at other temperatures. The differences among generations for the time female wasps spent drumming host eggs did not show any host and generation related trend. European corn borer egg parasitism was positively correlated with egg density. Female T. ostriniae might exhibit the Type II or Type III functional response depending on the temperature. The field data suggested a Type II functional response when data were pooled for all replicates. The effects of weather, plant size, and distribution of egg masses on egg parasitism by the wasp were studied in a sweet corn field. Logistic regression analyses indicated that percentage of eggs parasitized was negatively related to an increase in leaf area and distance of eggs from release point. Eggs on leaves in the upper third of a corn plant received much less parasitism than those on the middle and lower third. Temperature as well as the length of exposure of egg to wasps also affected the level of egg parasitism. Laboratory test on the cross breeding between T. ostriniae and T. nubilale indicated no successful hybridization. The results of the inter- and intra-specific discrimination and competition between the two species revealed that only female T. ostriniae discriminated eggs parasitized by females of the same species. When both species oviposited the same egg, T. ostriniae was most likely to be able to complete development. The level of egg parasitism by releasing T. ostriniae alone was found to be 15% higher than that by releasing T. nubilale alone, and 20% higher than by releasing a combination of the two species. Further analyses using the logistic regression model for independent and correlated data indicated T. ostriniae to be more efficient at discovering host egg masses than T. nubilale. Mutual interference between the two species was the main factor for the lower level of egg parasitism when the two species were released together. The results suggest that T. ostriniae is the better candidate for augmentative releases for control of the European corn borer, and the two species should not be released into a corn field at the same time

Microstructural Characterization of Thermal Barrier Coatings Glazed by a High Power Laser

Plasma-sprayed thermal barrier coatings were laser-glazed by a high power laser in order to modify the structures. The microstructure of laser-glazed TBCs is investigated. The result indicates that a smooth and dense glazed surface with craters and a network of microcracks is obtained after laser-glazing. The laser-glazed region consists of a columnar microstructure. There are segmentation microcracks in the laser-glazed coatings, which don’t run through the coatings along thickness. Surface roughness has been reduced significantly for the laser treated ceramic coatings

Prediction of Microporosity in Complex Thin-Wall Castings with the Dimensionless Niyama Criterion

material

Investigation of Fused Alumina Based-Mold Facecoats for DZ22B Directionally Solidified Blades

The interaction between alloy melt and mold facecoats is the main factor affecting the surface quality of investment casting nickel-based superalloys. An investigation was undertaken to develop suitable refractories as facecoat materials for the directionally solidified blades of DZ22B nickel-based superalloys in order to avoid a sand-burning defect. The wettability and interface reactions between alloy melt and various facecoats were studied by using a sessile drop experiment and the real investment casting method, respectively. The results show that by adding Cr2O3 powder with the amounts of 2 wt.%, 5 wt.% and 10 wt.% in the fused alumina-based facecoats, the wetting angles between the alloy melt and facecoats decreased from 105.40° to 100.37°, 99.96° and 98.11°, respectively, while the sand-burning defect on the casting blade surfaces still formed during the process of directional solidification. However, by adding h-BN powder in the fused alumina-based facecoats, the wetting angles between the alloy melt and facecoats dramatically increased, the sand-burning defect on the casting blade surfaces was effectively inhibited and a metallic luster on the directionally solidified blades could be obviously observed. In this study, the suitable composition of mold facecoats for the investment casting of blades is 2 wt.% h-BN added fused alumina