What Are UMAT and VUMAT in Abaqus? Abaqus UMAT (User Material) and Abaqus VUMAT are Fortran-based subroutines used to define custom constitutive material models in Abaqus/Standard and Abaqus/Explicit, respectively. They allow engineers and researchers to program advanced mechanical behaviors—such as complex elasticity, plasticity, and composite damage—when built-in Abaqus material libraries are insufficient.
这 CAE 助手 guide provides a definitive roadmap for developing, implementing, and executing these subroutines. By exploring input/output architectures, step-by-step coding for elastic and orthotropic models, and a direct UMAT vs. VUMAT comparison, readers will gain the practical expertise needed to write accurate custom algorithms. Access the provided free PDF guides and Fortran code templates to accelerate advanced material modeling projects.
| 子程序类型 | 求解器界面 | 主要产出变量 | 关键输入变量 | 雅可比矩阵要求 | 应用用例 | 向量化支持 | 状态变量（SDV）容量 |
| UMAT | Abaqus/Standard（隐式） | 压力、DDSDDE、STATEV、SSE、SPD、SCD | STRAN、DSTRAN、PROPS、TIME、DTIME、TEMP、DFGRD0、DFGRD1 | 必需（一致的切线刚度） | 静态、塑性、蠕变、粘弹性 | 未向量化 | *DEPVAR (NSTATV) |
| VUMAT | Abaqus/Explicit | STRESSNEW、STATENEW、ENERINTERNNEW、ENERINELASNEW | 应变、属性、密度、DEFGRADOLD、应力OLD | 无需 | 冲击、碰撞、大变形 | NBLOCK 向量化 | *DEPVAR（NSTATEV） |
What Are UMAT and VUMAT in Abaqus?
Abaqus 内置了许多材料，但在实际项目中，这些材料往往不够用。这就是为什么工程师们会使用其他软件。 用户子程序. 。 和 Abaqus UMAT 和 Abaqus VUMAT, 您可以使用 Fortran 编写自己的材料模型，并将其直接链接到求解器。简单来说，您就是在告诉 Abaqus 您的材料在变形时如何响应。.
你可以这样理解：Abaqus 每次执行一步操作时，都会调用你的子程序并询问：, “更新后的应力是多少？材料应该如何响应？” 在 UMAT, 这种情况发生在隐式求解器（Abaqus/Standard）内部。 VUMAT, 它发生在显式求解器（Abaqus/Explicit）内部。.
- UMAT：可与 Abaqus/Standard 配合使用，最适合静态或慢速加载问题。它还提供材料雅可比矩阵（切线刚度），从而加快收敛速度。.
- VUMAT：可与 Abaqus/Explicit 配合使用，非常适合模拟碰撞、冲击或大变形等动态事件。它可以一次性更新多个点的应力。.
图 1：UMAT 子程序工作流程
典型学习路径
如果你是从零开始，通常的路径很简单：
- 从一个 基本弹性模型 （这样你就可以了解结构并测试你的设置）。.
- 逐步增加复杂性——塑性、硬化或粘弹性行为。.
- 一旦你熟练掌握了这些技巧，就可以扩展你的代码，使其包含损坏、故障或速率相关的效果。.
- 最后，当你的问题涉及动力学或大变形时，可以尝试将你的 UMAT 逻辑移植到 VUMAT 中。.
本博客将指导您完成第一步：编写和测试一个最小的弹性 UMAT 模型，然后展示如何将相同的思路扩展到 VUMAT 模型。读完本博客，您不仅会掌握理论知识，还会了解构建更高级模型所需的工作流程。.
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