优化设计的目标函数怎么设置呢

raincolour

mass，massfraction，vlum,volumefraction区别是什么？

lanshang0102

可以在objective 面板设置

raincolour

谢谢，我是想问他们之间的区别。

glin

help里讲得很清楚吧。

raincolour

help里面没有的吧？manual里面讲的很不清楚

murmur

help的原文： hyperworks的help做的很好，建议lz多翻翻 每次都会有收获

Mass, Volume

Both are global responses that can be defined for the whole structure, for individual properties (components) and materials, or for groups of properties (components) and materials.

It is not recommended to use mass and volume as constraints or objectives in a topography optimization.  Neither are very sensitive towards design modifications made in a topography optimization.

In order to constrain the volume for a region containing a number of properties (components), a DRESP2 equation needs to be defined to sum the volume of these properties (components), otherwise, the constraint is assumed to apply to each individual property (component) within the region.  This can be avoided by having all properties (components) use the same material and applying the volume constraint to that material.



Fraction of mass, Fraction of design volume

Both are global responses with values between 0.0 and 1.0.  They describe a fraction of the initial design space in a topology optimization.  They can be defined for the whole structure, for individual properties (components) and materials, or for groups of properties (components) and materials.

The difference between the mass fraction and the volume fraction is that the mass fraction includes the non-design mass in the fraction calculation, whereas the volume fraction only considers the design volume.

Formulation for volume fraction:
Volume fraction = (total volume at current iteration – initial non-design volume)/initial design volume

Formulation for mass fraction:
Mass fraction = total mass at current iteration/initial total mass

If, in addition to the topology optimization, a size and shape optimization is performed, the reference value (the initial design volume in the case of volume fraction, or initial total mass in the case of mass fraction) is not altered by size and shape changes.  This can, on occasion, lead to negative values for these responses.  If size and shape optimization is involved, it is recommended to use Mass or Volume responses instead of Mass Fraction or Volume Fraction, respectively.

In order to constrain the volume fraction for a region containing a number of properties (components), a DRESP2 equation needs to be defined to sum the volume of these properties (components), otherwise, the constraint is assumed to apply to each individual property (component) within the region.  This can be avoided by having all properties (components) use the same material and applying the volume fraction constraint to that material.

These responses can only be applied to topology design domains.  OptiStruct will terminate with an error if this is not the case.  
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What is the difference between volumefrac response and volume response?
Volumefrac response is the material fraction of the designable material volume.  The volume response is the total volume, which includes design and non-design volume
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mass 类似

[ 本帖最后由 murmur 于 2008-12-11 12:52 编辑 ]

jim.weng

mass，實際質量大小
massfraction，可視為將質量大小視為一比值關係
volume,體積
volumefraction可視為將體積大小視為一比值關係