which generalizes to the statement. This reduces the number of material constants from 81 to 54. In a similar fashion we can make use of the symmetry of the strain tensor This further reduces the number of material constants to 36. To further reduce the number of material constants consider the conclusion from the first law for elastic materials, equation

The following stress-strain curves were obtained for dif- ferent materials subjecting the specimen to the loading path(a, b, c, d ). Which one(s) of them correspond to elas- tic material(s)

For the uniform state of plane strain shown in the fig ure,which one(s) of the following statement(s) is(are valid?(Assume Poisson's ratio v+0)

We seek to characterize the local state of deformation of the material in a neighborhood of a point P. Consider two points P and Q in the undeformed

The following expression is the right statement of linear momentum balance for a deforming body of an arbitrary material

A Cauchy stress component at a given(fixed) point P of a structure in equilibrium under the action of external loads is defined when 1. the direction of the face on which the stress component acts is specified 2 the direction of the force from which the stress component is derived is specified None of the above statements

We are going to consider the forces exerted on a material. These can be external or internal. External forces come in two flavors: body forces(given per unit mass or volume) and surface forces(given per unit area). If we cut a body of material in equilibrium under a set of external forces along a plane as shown in fig. 1. and consider one side of it we draw two conclusions: 1 the equilibrium provided by the loads from the side taken out is provided by a set of forces that are distributed among the material particles adjacent to

16.21 Techniques of Structural Analysis and sig Spring 2003 Unit #1 In this course we are going to focus on energy and variational methods for structural analysis. To understand the overall approach we start by con- trasting it with the alternative vector mechanics approach

第五章飞机费用与效能分析 5.1飞机寿命周期费用的概念和分析方法 5.1.1飞机寿命周期费用的提出 现代成功的军用飞机和民用飞机,不仅具有较高的性能和效能,而且给用户在经济上带 来效益。因此飞机作为工程系统在多种方案优选决策时,在很大程度上取决于其经济性 为了满足现代战争的需要,不仅对飞机技术性能的要求日益提高,而且对其综合性能如 可靠性、维修性、保障性等提出了更高要求使其结构日趋复杂,性能日益精良,大量先进 的航空电子设备和火控系统的采用以及大量分系统和设备在功能上互相综合,使得现代飞机 研制、生产、使用保障等费用日益增长。例如,美国战斗机出厂价自1930年以来己增长了 两个数量级以上,1960年到1980年20年间,扣除通货膨胀因素,平均年增长率仍为9% 10%,20年增长了约5~6倍

一、~the+~est+名词+(that)+主词 have ever+seen(own/heard/had/read, etc) the most+形容词名词+(tht)+主词+ have ever+seen( known/heard/had/read, etc) 例句: Helen is the most beautiful girl that have ever seen 海伦是我所看过最美丽的女孩