---
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]]"
source_refs:
  - source: "[[Midas-NFX-Analysis-Manual|Midas NFX Analysis Manual]]"
    raw_path: ".raw/MidasNFXAnalysisManual/"
    raw_files:
      - "MidasNFXAnalysisManual_024.md"
      - "MidasNFXAnalysisManual_002.md"
    md_indices:
      - 24
      - 2
    match: "heuristic-heading-keyword"
    confidence: low
---

# 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.