你不知道的CAE小常识系列（二十七）：深入解析

你不知道的CAE小常识（二十七）

*BOUNDARY_NON_REFLECTING
1，0，0
还是
*BOUNDARY_NON_REFLECTING
1，1，1
许多人争论不休。
要告诉大家的是，LS-DYNA关键字手册关于该*BOUNDARY_NON_REFLECTING的说明
AD Default activation flag for dilatational waves. (on.EQ.0.0, off.NE.0.0)
AS Default activation flag for shear waves. (on.EQ.0.0, off.NE.0.0)
是错误的（关键字手册有不少错误），恰好说反了。应该是
AD Default activation flag for dilatational waves. (off.EQ.0.0, on.NE.0.0)
AS Default activation flag for shear waves. (off.EQ.0.0, on.NE.0.0)
意思是说等于0的时候，膨胀波和剪切波不会产生，是关闭的，相当于无反射边界；不等于0的时候，会产生膨胀波和剪切波，相当于有限边界，自由边界。
对此，ANSYS的帮助手册上有说明：
EDNB, Option, Cname, AD, AS
Defines a nonreflecting boundary in an explicit dynamic analysis.
Option
Label identifying the nonreflecting boundary option to be performed.
ADD — Define a nonreflecting boundary (default).
DELE — Delete a nonreflecting boundary.
LIST — List all defined nonreflecting boundaries (remaining fields are ignored). 
Cname
Name of existing nodal component to which the nonreflecting boundary is to be added or deleted. For Option = DELE, use Cname = ALL to delete all defined nonreflecting boundaries.
AD
Activation flag for dilatational waves (dampers normal to waves).
0 — Dilatational activation flag is off (default). 
1 — Dilatational activation flag is on.
AS
Activation flag for shear waves (dampers tangent to waves).
0 — Shear activation flag is off (default).
1 — Shear activation flag is on.
此外，使用TG中无反射边界的NR命令，输出为：
*BOUNDARY_NON_REFLECTING
1，0，0
所以，无反射边界就是
*BOUNDARY_NON_REFLECTING
1，0，0