Field Output（FO，场变量输出）和 History Output（HO，历史变量输出） 是 Abaqus 中两种基本的数据输出类别。这两者是独立的，有不同的应用场景。刚开始接触 Abaqus 的话会对这两个变量的使用感到困惑。

下面的描述来自于 Abaqus/CAE User’s Guide (6.14)。

Field output

Abaqus generates field output from data that are spatially distributed over the entire model or over a portion of it. In most cases you use the Visualization module to view field output data using deformed shape, contour, or symbol plots. The amount of field output generated by Abaqus during an analysis is often large. As a result, you typically request that Abaqus write field data to the output database at a low rate; for example, after every step or at the end of the analysis.

When you create a field output request, you can specify the output frequency in equally spaced time intervals or every time a particular length of time elapses. For an Abaqus/Standard analysis procedure, you can alternatively specify the output frequency in increments, request output after the last increment of each step, or request output according to a set of time points. For an Abaqus/Explicit analysis procedure, you can alternatively request field output for every time increment or according to a set of time points. For an Abaqus/CFD analysis procedure, you can alternatively specify the output frequency in increments.

When you create a field output request, Abaqus writes every component of the selected variables to the output database. For example, if you were using solid elements to model a cantilever beam with a load at the tip, you could request the stress (all six components) and the displacement (all six components) data from the entire model after the last increment of the loading step. You could then use the Visualization module to view a contour plot of stresses and deflections in the final loaded state.

History output

Abaqus generates history output from data at specific points in a model. In most cases you use the Visualization module to display history output using X–Y plots. The rate of output depends on how you want to use the data that are generated by the analysis, and the rate can be very high. For example, data generated for diagnostic purposes may be written to the output database after every increment. You can also use history output for data that relate to the model or a portion of the model as a whole; for example, whole model energies.

When you create a history output request, you can specify the output frequency in equally spaced time intervals or every time a particular length of time elapses. For an Abaqus/Standard analysis procedure, you can alternatively specify the output frequency in increments, request output after the last increment of each step, or request output according to a set of time points. For an Abaqus/Explicit analysis procedure, you can alternatively request history output in time increments. For an Abaqus/CFD analysis procedure, you can alternatively specify the output frequency in increments.

When you create a history output request, you can specify the individual components of the variables that Abaqus/CAE will write to the output database. For example, if you model the response of a cantilever beam with a load applied to the tip, you might request the following output after each increment of the loading step:

The principal stress at a single node at the root of the beam.

The vertical displacement at a single node at the tip of the beam.

You could then use the Visualization module to view an X–Y plot of stress at the root versus displacement at the tip with increasing load.

从实际使用来讲，FO 和 HO 的主要区别就体现在记录的频次和范围。

FO 在整个模拟运行过程中的记录次数较少，而 HO 的输出频次较高。这个当然也跟操作者的设定有关。记录频次是可以修改的。但是通常 FO 的设定都比较小，而 FO 的记录则比较密集以便输出的数据在做图成曲线的时候能够反映更多的变化的细节。但是记录的频次越高，需要记录的数据量就越大。有的时候，特别是大型服务器上，配置文件中可能会限定能够记录的 HO 的条数（跟选取的对象里的 Element 或者 Node 个数、变量/分量个数等有关）。

FO 在设定的时候通常选择某个变量后会将该变量所有的分量都记录下来。它在设定的时间点的时候会将选定对象（整个模型或者模型的一部分）的**所有数据点**上该变量的所有分量值进行记录。而 HO 在设定的时候可以选择只记录某个变量的某个分量。而且，设置 HO 的时候选定的观察对象可以是有限的一个或几个数据点，比如某一个节点（Node）或者某个集合（Set）等。然后它会在每个设定的时间点将该对象的改变量（或变量的分量）记录下来。简单来说就是，HO 的记录更精细，更有针对性。其结果可以直接用来作出对应的变量（或其分量）随时间的变化曲线。

而且似乎 FO 和 HO 中提供的变量还有些差别。暂时先不深究了。©

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