김경종
62 lines
2.7 KiB
Markdown
62 lines
2.7 KiB
Markdown
---
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type: concept
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title: "Midas NFX Linear Dynamics and Buckling Analyses"
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created: 2026-06-02
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updated: 2026-06-02
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address: c-000178
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aliases:
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- NFX linear dynamics
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- NFX buckling analysis
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tags:
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- concept
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- finite-element-method
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- midas-nfx
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- dynamics
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- buckling
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status: current
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related:
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- "[[Midas-NFX-Analysis-Manual|Midas NFX Analysis Manual]]"
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- "[[midas NFX]]"
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- "[[Direct Time Integration Methods]]"
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- "[[Finite Element Eigenproblem Solvers]]"
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- "[[Geometric Stiffness Matrix]]"
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- "[[Midas NFX Equation Solvers and Eigen Extraction]]"
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sources:
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- "[[Midas-NFX-Analysis-Manual|Midas NFX Analysis Manual]]"
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---
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# Midas NFX Linear Dynamics and Buckling Analyses
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## Definition
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The NFX linear dynamics and buckling thread covers normal modes, linear buckling, effective mass, mode superposition, transient response, frequency response, random response, and response spectrum analysis.
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## Modal and Buckling Base
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Normal mode analysis uses mass-normalized modes, generalized mass, generalized stiffness, participation factors, and modal effective mass. Buckling uses the same generalized eigenproblem structure but replaces the dynamic mass-like matrix with geometric stiffness and normalizes buckling vectors by maximum displacement component rather than modal mass.
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## Mode Superposition
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The manual presents mode superposition as a reduction of the physical dynamic equation
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```text
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M u_ddot(t) + C u_dot(t) + K u(t) = f(t)
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```
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into modal coordinates. It also documents residual vectors for improving truncated modal bases and enforced-motion handling through constrained/free DOF partitioning.
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## Linear Response Families
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NFX covers direct and modal transient response, direct and modal frequency response, random response, and response spectrum analysis. The manual includes damping treatment, frequency-domain response, random response statistical values, RMS and zero crossing, modal combination, and spectrum correction.
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## Solver Development Use
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For a custom solver, this page defines output checks that should be testable against reference solvers: natural frequencies, periods, mode shapes, modal mass, effective mass ratios, buckling load factors, transient displacement histories, frequency-response amplitudes/phases, response-spectrum modal combinations, and random-response statistics.
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## Connections
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- [[Finite Element Eigenproblem Solvers]] gives the common eigen extraction context.
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- [[Direct Time Integration Methods]] gives the time-domain integration frame.
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- [[Geometric Stiffness Matrix]] connects linear buckling to stress stiffness.
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- [[Midas Civil Dynamic and Seismic Analysis]] and [[Midas FEA Linear Dynamics and Buckling Analyses]] are sibling MIDAS references.
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