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71.
利用锻造镦粗工艺制备了高横向塑性Mo-La2O3棒材,并检测了其在退火过程中横向弯曲性能,观察了其组织结构,利用SEM进行了断口形貌分析。结果表明:Mo-La2O3棒经锻造镦粗变形85%后横向具有较好的塑性,延伸率达到了2%,在退火过程中横向塑性逐渐升高,在1200℃时延伸率达到10%以上,经1570℃退火1 h后,合金发生了再结晶,此时延伸率为1.5%;Mo-La2O3棒中形成了大量的位错胞亚结构,胞内有大量的位错缠结在一起,这些位错还被La2O3钉扎;Mo-La2O3棒经1200℃退火后,断口有"分层"现象,且断口上具有明显的河流状花样和解理台阶,断裂面上伴有大量塑性变形的韧带和撕裂岭。 相似文献
72.
The torsion of homogeneous, isotropic, linearly elastic cylindricalbars has been the subject of numerous investigations from theoretical,computational and applied viewpoints. It is well known thatin this case, the circular shaft is the only one whose cross-sectiondoes not involve a warping displacement in the axial direction.For an inhomogeneous, isotropic, circular bar, there is alsono warping of the cross-section provided that the shear modulusvaries only in the radial direction. For general anisotropicmaterials, torsion induces bending and vice versa. For thoseanisotropic materials with at least one plane of elastic symmetrynormal to the axial direction, pure torsion is possible. Forhomogeneous materials of this type and special inhomogeneousmaterials, it has been shown by various arguments that no warpingoccurs for bars of particular elliptical cross-section. Here,we provide a unified derivation of the foregoing results. Somediscussion of torsional rigidities is also given. 相似文献
73.
In this work, a detailed three-dimensional (3D) nonlinear finite element model is developed to study the response and predict the behavior of precast hybrid beam–column connection subjected to cyclic loads that was tested at the National Institute of Standards and Technology (NIST) laboratory. The precast joint is modeled using 3D solid elements and surface-to-surface contact elements between the beam/column faces and interface grout in the vicinity of the connection. The model takes into account the pre-tension effect in the post-tensioning strand and the nonlinear material behavior of concrete. The model response is compared with experimental test results and yielded good agreement at all stages of loading. Fracture of the mild-steel bars resulted in the failure of the connection. In order to predict this failure mode, stress and strain fields in the mild-steel bars at the beam–column interface were generated from the analyzed model. Such fields of stresses and strains are hard to measure in experimental testing. In addition, the magnitude of the force developed in the post-tensioning steel tendon was also monitored and it was observed that it did not yield during the entire loading history. Successful finite element modeling will provide a practical and economical tool to investigate the behavior of such connections. 相似文献
74.
Hu Ping Na Jingxin 《Acta Mechanica Solida Sinica》1997,10(2):138-147
The BPA eight chain molecular network model is introduced into the finite element for-mulation of elastic-plastic large deformation.And then,the tensile deformation localization develop-ment of the amorphous glassy circular polymeric bars(such as polycarbonates)is numerically simulat-ed.The simulated results are compared with experimental ones,and very good consistence betweennumerical simulation and experiment is obtained,which shows the efficiency of the finite elementanalysis.Finally,the influences of the microstructure parameter S_ on tensile neck-propagation andtriaxial stress effect are studied. 相似文献
75.
A.L.C.H. Villavicencio M.M. Araújo G.B. Fanaro P.R. Rela J. Mancini-Filho 《Radiation Physics and Chemistry》2007,76(11-12):1875-1877
Gamma-rays utilized as a food-processing treatment to eliminate insect contamination is well established in food industries. Recent troubles in Brazilian cereal bars commercialization require a special consumer's attention because some products were contaminated by insects. To solve the problem, food-irradiation treatment was utilized as a safe and effective solution. The final product was free of insect contamination. The aim of this study was to determine the best radiation dose processing utilized to disinfestations and detect some change on sensorial characteristic by sensorial analysis in cereal bars. In this study, three different kinds of cereal bars were purchased in São Paulo (Brazil) in supermarkets and irradiated with 1.0, 2.0 and 3.0 kGy at “Instituto de Pesquisas Energéticas e Nucleares” (IPEN-CNEN/SP). The samples were treated with ionizing radiation using a 60Co gamma-ray facility (Gammacell 220, A.E.C.L.). That radiation doses were used successfully as an anti-insect treatment in the cereal bars, since in some food industries doses up to 3.0 kGy are used to guarantee at least a dose of 1.0 kGy in internal cereal bars package. Sensorial analysis was necessary since cereal bars contain ingredients very sensitive to ionizing radiation process. 相似文献
76.
Juha Honkala 《Semigroup Forum》2008,76(1):51-57
We generalize the notions of sparse and slender sets for an arbitrary monoid and characterize the unambiguous rational sets
which are sparse or slender. 相似文献
77.
78.
The investigations of forebody vortex flow and its flow control have great importance in both academic field and engineering application areas. A large number of papers and many review papers have been published. However in this research field of forebody asymmetric vortices, three problems such as tip perturbation effect, Reynolds number effect and flow instability are less studied and thus not understood completely. So many researches are still working on the issues in recent years. The present paper attempts to provide a review of recent research progress on first two problems. The first problem is mainly concerned with how the vortex flow evolves after tip perturbation; how to solve the problem of repeatability and reproducibility of wind tunnel testing data; how to develop a conception of active flow control technique with tip perturbation based on the study of vortex flow response to tip perturbation. For the second problem one is mainly concerned that how the asymmetric vortices are developed with the increase of Reynolds number; how to classify the vortex flow patterns in different Reynolds number regimes; how to develop an appropriate boundary layer transition technique to simulate flows at high Reynolds number in the convention wind tunnels. Finally, some important ques- tions that deserve answers are proposed in the concluding remarks. 相似文献
79.
80.
介绍了迈克孙干涉条纹自动计数仪的设计与应用,该装置与迈克耳孙干涉仪配合使用,实验的测试结果与教学效果得到了显著改善。 相似文献