Femap and NX Nastran Technical Seminar on Vibration ... · Femap modeling workflow for Beam, Plate...

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Normal Modes Analysis May 2012

©2012 Predictive Engineering All Rights Reserved

• Normal Modes Analysis: Basics• How it Works

• Principle of Orthogonality• Strain Energy• Mass Participation

• Available Resources• Next Training Opportunity on October 15‐19, 2012

Seminar Outline

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Linear Dynamics: )t(rkutuc

tum.M.O.E 2

2

=+∂∂

+∂∂

Eigenvalue problem: undamped free vibration: 0kutum 2

2

=+∂∂

Assuming a solution of the form: tsinuu o ω=

Then: [ ]{ } 0umk o2 =ω−

For non‐trivial solutions (i.e., solutions that are more than just zeros):

[ ] 0mk 2 =ω−mk =ωGiving us the well know frequency relationship:

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Normal Modes / Eigenvalue problem: undamped free vibration

k

secrad16.15

100000,23

mk

===ω

let:Kvertical=1000/0.0435m=100

NX Nastran reports frequencies in cycles per second. Hence, 15.16 radians/sec is equal to 2.41 cycles/sec.

Example Model: Normal Modes Validation Start.modfemSimple CBUSH with Mass ElementFocus: Units | Theory | Why Only Three Modes?

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Normal Modes / Eigenvalue problem: Principal of Orthogonality

Even basic normal modes analysis can be confusingBasic beam model with a pinned support is interrogatedIs it logical?Why are there double modes?

Example Model: Simple Beam ‐ Principal of Orthogonality.modfemAnalyze | Change B.C.’s | Double Modes

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Normal Modes / Eigenvalue problem: Strain Energy Density

To improve the dynamic performance it is often as simple as moving the first mode to a higher frequencyNormal modes is all about stiffness and massStrain energy tells you where to add stiffness

Example Model:Radioframe Networks GR‐63‐Core Seismic Analysis.MODFEMShow Strain Energy | Discuss How Improvements Were Made | CORE‐GR‐63 Zone 4 Seismic

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Example Model: Coors Tek Paper Mill Forming Board ‐ Original Design ‐ Start.modfem

Normal Modes / Eigenvalue problem: Mass Participation and Optimization

Mass Participation Tells You HeapsOptimization is often best done by intelligent inspectionDon’t expect miracles from computer programs

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Normal Modes / Eigenvalue problem: Resources

NX Nastran DocumentationPredictive Engineering WebsiteBe Inquisitive – we have lots of expertize to leverage

Femap and NX Nastran Training:Foundation | Advanced | Customization www.Predict iveEngineering.com

Course OutlineFoundation of FEA Modeling with Femap + NX Nastran (Two Days)I. FEA theoretical background w.r.t beam,

isoparametric and special elementsII. Tour of Femap interface: Preferences, Panes,

Toolboxes, Help and Tips & TricksIII. Femap modeling workflow for Beam, Plate and

Solid (BPS) elementsIV. Static stress analysis and results interpretation of

BPS elementsV. Introduction to plate and solid modeling with

surface and solid geometry and Mesh ToolboxVI. Introduction to Assembly Modeling: Glued,

Contact and Rigid Element Usage

Advanced Femap + NX Nastran (Two Days)I. Surface modeling using manifold and non‐

manifold geometriesII. Advanced surface preparation for high‐accuracy

plate modelingIII. Meshing toolbox tips and tricks with Jacobian

OptimizationIV. Building efficient assemblies via efficient solid

modeling (tet and hex elements) and linear contact

V. Introduction to linear dynamics (modal analysis tips and tricks)

VI. Non‐linear analysis: geometric versus material non‐linearity and best practices

Customization & Automation of Femap (One Day)I. Automation of results processing via ExcelII. Introduction to Femap’s macro capabilityIII. Introduction to Femap’s API via Custom ToolsIV. Programing Femap’s API

Welcome Femap Colleague,This week‐long course will take the new user from ground floor through FEA best practices to advanced subjects dealing with manifold and non‐manifold surface modeling, detailed plate meshing and tet versus hex meshing. The final day will finish with a focus on customization and automation using Excel and Femap’s own API interface. The course will be fast paced and follow a workshop format with theory, practice and Q&A sessions.

When: October 15‐19, 2012Where: Portland, ORCost: $475/day. Students may attend either the Introduction or the Advanced Sections or just the last day of Customization/Automation training.

What’s Included: Course manual with DVD. Two lunches and one social events are provided to encourage class interaction with fellow users.

Registration: Early registration is encouraged since space is limited to 20 students and it is expected that the classes will fill. To register please send email to: [email protected]: George Laird, Ph.D., P.E.

About Predictive EngineeringBased in Portland, Oregon, Predictive has over 15 years experience with Femap and Nastran and has developed a solid reputationas the “go to company” for Femap training and services. References can be obtained at our website: www.PredictiveEngineering.com.

Femap and NX Nastran Technical Seminar on Vibration ... · Femap modeling workflow for Beam, Plate...

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