关于ANSYS实体建模中几个命令的讨论

cc610824

1，lcsl与lovlap功能是否一样？
2，先建立面，然后用拖拉命令vdrag生成的两个体，是否不用再vglue 了？

cc610824

1，lcsl与lovlap功能是否一样？
2，先建立面，然后用拖拉命令vdrag生成的两个体，是否不用再vglue 了？
3，对于两个接触的面，采用nummrg和aglue有区别吗？我发现没什么大的变化啊，重合的点都只有一个了。
（重新写一遍）

zhouxman

我感觉第一个和第二个问题 可以自己建立一个简单的模型试验一下

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原帖由 cc610824 于 2009-5-3 08:07 发表

                               
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1，lcsl与lovlap功能是否一样？
2，先建立面，然后用拖拉命令vdrag生成的两个体，是否不用再vglue 了？
3，对于两个接触的面，采用nummrg和aglue有区别吗？我发现没什么大的变化啊，重合的点都只有一个了。
（重新 ...

1、关于布尔运算详细观看help的5.4. Sculpting Your Model with Boolean Operations章节，这里有图文说明。
2、这看你的两个体之间的连接关系了，如果当成一个整体，需要进行glue或者add操作。
3、这两个还是有区别的，具体见下段文字。
Gluing Operations vs. Merging Operations

Adjacent, touching regions can be joined by gluing them (AGLUE, LGLUE, VGLUE) or by merging coincident keypoints (NUMMRG,KP, which also causes merging of identical lines, areas, and volumes). In many situations, either approach will work just fine. Some factors, however, may lead to a preference for one method over the other.

Geometric Configuration

Gluing is possible regardless of the initial alignment or offset of the input entities. Keypoint merging is possible only if each keypoint on one side of the face to be joined is matched by a coincident keypoint on the other side. This is commonly the case after a symmetry reflection (ARSYM or VSYMM) or a copy (AGEN or VGEN), especially for a model built entirely in ANSYS rather than imported from a CAD system. When the geometry is extremely precise, and the configuration is correct for keypoint merging, NUMMRG is more efficient and robust than AGLUE or VGLUE.

Model Accuracy

Gluing, like all ANSYS boolean operations, requires that the input entities meet the current boolean tolerance (BTOL). Otherwise, AGLUE or VGLUE may fail. In such cases, relaxing the tolerance may allow the glue to complete. An advantage of gluing is that it is unlikely to degrade the accuracy of a geometric model. Keypoint merging can operate on almost any combination of entities (although you may have to override the default tolerances on NUMMRG). However, it can also introduce or increase accuracy flaws, making later boolean operations less likely to succeed. If the input tolerances are too large, NUMMRG can collapse out small lines, areas, or volumes you intended to keep, possibly rendering the model unusable.

Mesh Status

Gluing, like all ANSYS boolean operations, requires that the input entities be unmeshed. Keypoint merging is effective for meshed models under the right conditions. More information on keypoint merging follows.

Merging Solid Model Entities:

When merging solid model entities (Label = KP or ALL), keypoint locations are used as the basis for merging. Once keypoints are merged, any higher order solid model entities (lines, areas, and volumes), regardless of their select status or attachment to the merged keypoints, are considered for merging.

Keypoints that are attached to lines will be merged only if:

ΔX,  ΔY, and ΔZ are each less than TOLER

where,ΔX is the X component of the distance between keypoints,
ΔY is the Y component of the distance between keypoints, and  
ΔZ is the Z component of the distance between keypoints;


and

is less than 1E-5 times the length of the longest line attached to those keypoints (internal relative solid model tolerance), or  is less than GTOLER (global solid model tolerance) if specified.

The TOLER field is a consideration tolerance. If a keypoint is within TOLER of another keypoint, then those two keypoints are candidates to be merged. If, when "moving" the higher numbered keypoint, the distance exceeds the internal relative solid model tolerance, or the global solid model tolerance (GTOLER) if specified, the keypoints will not be merged. Lines, areas, and volumes are considered for merging in a similar manner.

The internal relative solid model tolerance should be overridden by the global solid model tolerance (GTOLER) only when absolutely necessary. GTOLER is an absolute tolerance; if specified, relative lengths of lines in the model will no longer be considered in the merge operation. If GTOLER is too large, you can "merge-out" portions of your model accidently, effectively defeaturing the model. If GTOLER is used, it is recommended that NUMMRG be preceded by saving the database (since undesired merges of solid model entities could occur).

Note
Use of the NUMMRG command does not cause changes to a model's geometry; only the topology is affected.

zhouxman

还是help比较好，不过看起来比较吃力，理解上也不很如意

cc610824

我好好理解理解，谢谢了~