排序方式: 共有39条查询结果,搜索用时 203 毫秒
21.
This article deals with the investigation of the effects of porosity distributions on nonlinear free vibration and transient analysis of porous functionally graded skew (PFGS) plates. The effective material properties of the PFGS plates are obtained from the modified power-law equations in which gradation varies through the thickness of the PFGS plate. A nonlinear finite element (FE) formulation for the overall PFGS plate is derived by adopting first-order shear deformation theory (FSDT) in conjunction with von Karman’s nonlinear strain displacement relations. The governing equations of the PFGS plate are derived using the principle of virtual work. The direct iterative method and Newmark’s integration technique are espoused to solve nonlinear mathematical relations. The influences of the porosity distributions and porosity parameter indices on the nonlinear frequency responses of the PFGS plate for different skew angles are studied in various parameters. The effects of volume fraction grading index and skew angle on the plate’s nonlinear dynamic responses for various porosity distributions are illustrated in detail. 相似文献
22.
23.
25.
27.
28.
29.
30.
德国防空简史德国武装力量(Bundeswehr)包括海军(Kriegsmarine)、陆军(Heeres)和空军(Luftwaffe)。唯一隶属于北约的陆军由29万6千名正规军和战时属于第一、第二、第三军的6万4千名预备役军人组成。历史经验已使德国陆军认识到提供足够防空来保护自己地面部队的重要性。这一点至今记忆犹新并在防空军训练和教材中处处可见。 相似文献