add wiki

wiki/concepts/Abaqus User Subroutines and Utility Routines.md

@@ -4,7 +4,7 @@ title: "Abaqus User Subroutines and Utility Routines"
 complexity: advanced
 domain: computational-mechanics
 created: 2026-05-29
-updated: 2026-05-29
+updated: 2026-06-01
 address: c-000091
 aliases:
   - Abaqus user subroutines
@@ -19,12 +19,18 @@ tags:
 status: current
 related:
   - "[[Abaqus-Analysis-User-s-Guide-Volume-II|Abaqus Analysis User's Guide Volume II]]"
+  - "[[Abaqus-Analysis-User-s-Guide-Volume-III|Abaqus Analysis User's Guide Volume III]]"
+  - "[[Abaqus-Analysis-User-s-Guide-Volume-IV|Abaqus Analysis User's Guide Volume IV]]"
   - "[[Abaqus Job Execution Workflow]]"
   - "[[Abaqus Resource and Parallel Execution]]"
   - "[[Finite Element Program Implementation]]"
   - "[[Abaqus Multiphysics Coupling and Co-simulation]]"
+  - "[[Abaqus User-Defined Material Behavior]]"
+  - "[[Abaqus User-Defined Elements]]"
 sources:
   - "[[Abaqus-Analysis-User-s-Guide-Volume-II|Abaqus Analysis User's Guide Volume II]]"
+  - "[[Abaqus-Analysis-User-s-Guide-Volume-III|Abaqus Analysis User's Guide Volume III]]"
+  - "[[Abaqus-Analysis-User-s-Guide-Volume-IV|Abaqus Analysis User's Guide Volume IV]]"
 ---
 
 # Abaqus User Subroutines and Utility Routines
@@ -41,6 +47,10 @@ Subroutines can call certain Abaqus utility routines, but user subroutines canno
 
 The guide emphasizes implementation discipline: include the required Abaqus parameter files, follow Fortran/C calling conventions, avoid overwriting variables not designated for user definition, allocate large arrays dynamically, respect Abaqus file unit numbers, and test on small models before production use.
 
+[[Abaqus-Analysis-User-s-Guide-Volume-III|Volume III]] adds the material-specific branch of this extension system. `UMAT`, `VUMAT`, and `UMATHT` define mechanical or thermal material behavior, allocate and update state variables, supply material tangents where required, and can participate in element deletion through state-variable flags.
+
+[[Abaqus-Analysis-User-s-Guide-Volume-IV|Volume IV]] adds the element-specific branch. `UEL`, `UELMAT`, and `VUEL` allow custom element residuals, matrices, explicit element behavior, active degrees of freedom, state variables, loads, and output, but user elements have important contact and import limitations.
+
 ## Why It Matters
 
 User subroutines are the point where a production finite element code becomes an extensible platform. They can encode material behavior, loads, fields, output, control logic, and external coupling, but they also introduce compiler, memory, thread-safety, restart, and debugging risks.
@@ -50,8 +60,11 @@ User subroutines are the point where a production finite element code becomes an
 - [[Abaqus Job Execution Workflow]] supplies the command-line path for compiling and linking user code.
 - [[Abaqus Resource and Parallel Execution]] matters because user routines share memory and must behave correctly under parallel execution.
 - [[Finite Element Program Implementation]] is the broader code-architecture context for extension points.
+- [[Abaqus User-Defined Material Behavior]] focuses on the material subroutine subset of the extension workflow.
+- [[Abaqus User-Defined Elements]] focuses on the element subroutine subset of the extension workflow.
 
 ## Sources
 
 - [[Abaqus-Analysis-User-s-Guide-Volume-II|Abaqus Analysis User's Guide Volume II]]
-
+- [[Abaqus-Analysis-User-s-Guide-Volume-III|Abaqus Analysis User's Guide Volume III]]
+- [[Abaqus-Analysis-User-s-Guide-Volume-IV|Abaqus Analysis User's Guide Volume IV]]