【讨论】线性还是非线性？

tmpyy

我用如下命令定义结构中两个面的接触：
  
**  
** INTERACTION PROPERTIES
**  
*Surface Interaction, name=nofriction
1.,
*Friction
0.,
*Surface Behavior, pressure-overclosure=HARD
...
...
*Contact Pair, interaction=nofriction
_PickedSurf552, pin-a-3.RigidSurface_
  
我认为这种接触条件应该是线性的，但分析显示结果是非线性的，即荷载是1和荷载是1000时位移及应力并不是1000倍的关系。为什么？十分感谢！

cafe0519

Post your boundary and loads settings pls.

tmpyy

**  
** MATERIALS
**  
*Material, name=steel
*Elastic
  2.06e+08, 0.3
**  
** INTERACTION PROPERTIES
**  
*Surface Interaction, name=nofriction
1.,
*Friction
0.,
*Surface Behavior, pressure-overclosure=HARD
**  
** BOUNDARY CONDITIONS
**  
** Name: pin-a-1 Type: Displacement/Rotation
*Boundary
_PickedSet410, 1, 1
_PickedSet410, 2, 2
_PickedSet410, 3, 3
_PickedSet410, 4, 4
_PickedSet410, 5, 5
_PickedSet410, 6, 6
** Name: pin-a-2 Type: Displacement/Rotation
*Boundary
_PickedSet411, 2, 2
_PickedSet411, 3, 3
_PickedSet411, 4, 4
_PickedSet411, 5, 5
_PickedSet411, 6, 6
** Name: pin-b Type: Displacement/Rotation
*Boundary
_PickedSet412, 3, 3
_PickedSet412, 4, 4
_PickedSet412, 5, 5
_PickedSet412, 6, 6
** Name: symmetry Type: Symmetry/Antisymmetry/Encastre
*Boundary
_PickedSet413, ZSYMM
**  
** INTERACTIONS
**  
** Interaction: pin-a-1
*Contact Pair, interaction=nofriction
_PickedSurf552, pin-a-3.RigidSurface_
** Interaction: pin-a-2
*Contact Pair, interaction=nofriction
_PickedSurf550, pin-a-4.RigidSurface_
** Interaction: pin-b
*Contact Pair, interaction=nofriction
_PickedSurf548, pin-b-1.RigidSurface_
** ----------------------------------------------------------------
**  
** STEP: Step-1
**  
*Step, name=Step-1
equivalent loads
*Static
1., 1., 1e-05, 1.
**  
** LOADS
**  
** Name: Load-1   Type: Concentrated force
*Cload
_PickedSet408, 1, 1000.
**  
** OUTPUT REQUESTS
**  
*Restart, write, frequency=1
**  
** FIELD OUTPUT: F-Output-1
**  
*Output, field, variable=PRESELECT
**  
** HISTORY OUTPUT: H-Output-1
**  
*Output, history, variable=PRESELECT
*El Print, freq=999999
*Node Print, freq=999999
*End Step
** ----------------------------------------------------------------
**  
** STEP: Step-2
**  
*Step, name=Step-2
*Static
1., 1., 1e-05, 1.
**  
** LOADS
**  
** Name: Load-1   Type: Concentrated force
*Cload, op=NEW
** Name: Load-2   Type: Concentrated force
*Cload, op=NEW
_PickedSet731, 1, 1000.
**  
** OUTPUT REQUESTS
**  
*Restart, write, frequency=1
**  
** FIELD OUTPUT: F-Output-1
**  
*Output, field, variable=PRESELECT
**  
** HISTORY OUTPUT: H-Output-1
**  
*Output, history, variable=PRESELECT
*End Step
** ----------------------------------------------------------------
**  
** STEP: Step-3
**  
*Step, name=Step-3
*Static
1., 1., 1e-05, 1.
**  
** LOADS
**  
** Name: Load-2   Type: Concentrated force
*Cload, op=NEW
** Name: Load-3   Type: Concentrated force
*Cload, op=NEW
_PickedSet731, 2, -1000.
**  
** OUTPUT REQUESTS
**  
*Restart, write, frequency=1
**  
** FIELD OUTPUT: F-Output-1
**  
*Output, field, variable=PRESELECT
**  
** HISTORY OUTPUT: H-Output-1
**  
*Output, history, variable=PRESELECT
*End Step

tmpyy

我有三个pin和结构通过接触面相连，荷载和部份约束通过这三个pin施加，有三个独立变化的荷载，我建立了三个step，分别施加三个荷载的单位荷载，通过线性迭加即可得到三个荷载共同作用下的应力和变形了。可计算显示结构并非线性，即单位荷载用1000 和用1，迭加的结果相差很多，结构的其它部份肯定是线性的，唯有pin和结构的接触面我拿不准是线性还是非线性的，哪位知道请给我讲讲，十分感谢。

byhyj

接触工况肯定是非线性，只是这种非线性能在多大的程度影响你的整个模型的线性分布。就只能靠你的经验和判断了！！！！