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+---
+type: concept
+title: "Midas NFX Contact Analysis"
+created: 2026-06-02
+updated: 2026-06-02
+address: c-000180
+aliases:
+  - NFX contact analysis
+  - NFX penalty contact
+tags:
+  - concept
+  - finite-element-method
+  - midas-nfx
+  - contact
+  - nonlinear-analysis
+status: current
+related:
+  - "[[Midas-NFX-Analysis-Manual|Midas NFX Analysis Manual]]"
+  - "[[midas NFX]]"
+  - "[[Finite Element Contact Formulation]]"
+  - "[[Abaqus Contact Formulations and Enforcement]]"
+  - "[[Midas FEA Static Contact Analysis]]"
+sources:
+  - "[[Midas-NFX-Analysis-Manual|Midas NFX Analysis Manual]]"
+---
+
+# Midas NFX Contact Analysis
+
+## Definition
+
+NFX contact analysis enforces non-penetration and optional tangential behavior between bodies. The manual covers general contact, rough contact, welded contact, sliding contact, breaking-weld contact, node-to-surface, surface-to-surface, single-surface, and mortar contact.
+
+## Contact Search and Discretization
+
+The source distinguishes global contact search from local projection. Contact can be detected through slave node to master segment projection, surface-to-surface integration, or mortar segment integration. It notes the usual tradeoff: node-to-surface contact is cheaper, while surface-to-surface contact is generally more accurate for contact pressure distribution.
+
+## Penalty Enforcement
+
+Normal contact force is enforced with a penalty relation based on the normal gap, with contact active when the gap becomes negative. NFX automatically computes penalty stiffness from element/material scale quantities and smooths the contact-force transition to reduce oscillation near contact onset.
+
+## Friction and Breaking Weld
+
+Tangential behavior uses a penalty relation coupled to normal contact force. The manual gives a friction yield-like condition based on tangential force norm and `mu f_C`. Breaking-weld contact maintains welded relative motion until combined normal and tangential contact force measures exceed a failure envelope.
+
+## Solver Development Use
+
+For a custom solver, this page separates contact into five testable pieces: search/projection, active set detection, normal penalty force, tangential/friction update, and tangent contribution. Each needs reference-model checks because contact errors can look like element or nonlinear-solver failures.
+
+## Connections
+
+- [[Finite Element Contact Formulation]] gives the shared FE contact formulation context.
+- [[Abaqus Contact Formulations and Enforcement]] is a commercial contact enforcement comparison.
+- [[Midas FEA Static Contact Analysis]] is the sibling MIDAS static contact reference.