呵呵，讨论的氛围真是浓厚，我一个个的看，看到最后越来越明晰。
谢谢大家的分享！
9楼回答很好
本帖最后由 leeking30 于 2011-4-8 17:06 编辑
From wikipedia deformation/mechanics 黑体是我标的
Deformation in continuum mechanics is the transformation of a body from a reference configuration to a current configuration. A configuration is a set containing the positions of all particles of the body. Contrary to the common definition of deformation, which implies distortion or change in shape, the continuum mechanics definition includes rigid body motions where shape changes do not take place
The cause of a deformation is not pertinent to the definition of the term. However, it is usually assumed that a deformation is caused by external loads,body forces (such as gravity or electromagnetic forces), or temperature changes within the body.
Strain is a description of deformation in terms of relative displacement of particles in the body.
Different equivalent choices may be made for the expression of a strain field depending on whether it is defined in the initial or in the final placement and on whether the metric tensor or its dual is considered.
In a continuous body, a deformation field results from a stress field induced by applied forces or is due to changes in the temperature field inside the body. The relation between stresses and induced strains is expressed by constitutive equations, e.g., Hooke's law for linear elastic materials. Deformations which are recovered after the stress field has been removed are called elastic deformations. In this case, the continuum completely recovers its original configuration. On the other hand, irreversible deformations remain even after stresses have been removed. One type of irreversible deformation is plastic deformation, which occurs in material bodies after stresses have attained a certain threshold value known as the elastic limit or yield stress, and are the result of slip, or dislocation mechanisms at the atomic level. Another type of irreversible deformation is viscous deformation, which is the irreversible part of viscoelastic deformation.
只围观 不表态 不表态 不表示不存在！
位移 变形 都应该是相对的概念 概念无绝对
百度百科上定义变形为：“物体在外来因素作用下产生的形状和尺寸的改变。”百科上定义位移为：“物体在外来因素作用下引起的质点位置的改变。”百科上定义应变为：“物体内任一点因各种作用引起的相对变形。”
个人理解，位移包括变形（位移=变形+刚体移动量），应变是单位体的变形
听着各位的讨论，概念渐渐清晰了
看了上面这么多回复，我觉得最简单的理解就是：
变形——是一种外在的宏观的现象
应变——是一种内在的微观的现象
我觉得主要是应变，位移可以有刚体位移
位移包括刚体位移，刚体位移好像不会发生形变
通常所说的位移是指物体每个节点的位移，如果每个节点的位移均相等，物体没有发生形变。就没有变形。应变是物体在某个方向上长度的变化后尺寸与变化前尺寸的比。一定发生了变形。
应变包括线应变和切应变，分别指某长度方向的相对伸长量和某两个垂直方向直角的该变量，轴力和弯矩引起线应变，剪切引起切应变
位移广义包括线位移和转角位移。线位移指该方向线应变和长度的乘积，是宏观上的量，长度单位；角度变化类推。
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狭义就理解为应变就行了
中科大的一个老师在弹性力学中讲变形分析，引入了物质坐标和空间坐标的概念。目前我正在看这块的东西，挺费劲的，物质坐标函数的lagrange描述，空间坐标函数的Euler描述。
抛砖引玉吧，恳请这方面深入的老师，能指点迷津。
应变应该是位移对坐标的导数吧，即弹性力学中的几何方程。这是两者的数量关系，所以一般可理解为是等价的，但就物理意义而言，位移是属于向量，而应变属于二阶张量，是不同的。这是个人的理解。