> For the complete documentation index, see [llms.txt](https://manual-1-3.karamba3d.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://manual-1-3.karamba3d.com/chinese_1_3_3/2-getting-started/2-getting-started-1/setting-up-a-structural-analysis/2.2.7-specify-materials.md).

# 2.2.7: 定义材料

材料的定义有两种方式：可以通过手动设置材料的力学性能来定义材料或从预先定义的材料库中选择材料（如图2.2.7.1（3））。材料添加在断面上。以下有两种定义材料的选项：

![图2.2.7.1：材料的定义](/files/-M9XuRnKh8vcpJxtHXhv)

1. 通过**“Assemble（模型构建）”** 运算器添加（如图2.2.7.2）。**“Elem|Id”**输入端指定应附加到构件上的材料名称。抑或使用正则表达式来选择构件。**“Elem|Id”**可以保留所有构件的材料为空设置。材料不直接附着到构件，而是附着到构件的断面。为了避免对其他构件产生副作用，请在确定新材料之前复制断面。
2.  在**“Cross Section（断面）”**运算器上直接输入，如图2.2.7.2所示。

![ 图2.2.7.2：材料的定义](/files/-M9XuRnLZULqINGpBAMS)

图2.2.7.1显示了如何通过元素名称“Elem|Id”定义材料：左：定义各向同性定制材料（1）；中：定义正交异性定制材料（2）；右：从材料库中选择一种材料（3）

{% hint style="info" %}
“**Assemble（模型构建）”**运算器定义的材料。
{% endhint %}

{% hint style="info" %}
如果用户未曾为梁或壳体单元指定横截面，程序将使用[默认材料](/chinese_1_3_3/2-getting-started/2-getting-started-1/karamba3d-entities.md#mo-ren-she-zhi)。
{% endhint %}


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