ansys rotational fatigue presentation

8/12/2019 AnSys Rotational Fatigue Presentation

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Fatigue Analysis of a Simple Shaft under Combined

Bending and Torsion

Material baseado em exemplo da HBM-nCODE e Ansys


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PRESENTATION TOPICS

Introduction

SAE notched shaft Specimen

Geometry and FEM model

Boundary Conditions

Linear Static Analysis Results

Overview: Fatigue Life Estimation Conclusion

References and Used Software


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Introduction

Courtesy nCode


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Introduction

Aloha Airlines Flight 243 (1988)


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Introduction

Fatigue life is estimated based on crack

initiation method.

A notched shaft under combined bending and

torsion loads is analised.

Two loading are combined , each load with its

own loading history.

Linear stresses used for the calculation is

obtained from bending and torsion loading

independently.


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Standard SAE notched shaft [1] is modeled.

This kind of specimen was used [1] to produce experimentalresults for multiaxial fatigue ,and later, these results werecompared to 5 different theories to estimate life to multiaxial

fatigue (not the scope of this example).

SAE notched shaft specimen


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Geometry


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Finite Element Model: Mesh


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Boundary Condition: Fixed Support


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Boundary Condition: Force


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Boundary Condition: Moment


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Two static analysis were performed

Bending due to unitary force

Torsion with a moment of 1000 N.mm

Following slides present stress distribution anddispacements

Linear Static Structural Analysis


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Results: Applied load is unitary force

Von Mises Equivalent

Stress

Maximum

Principal Stress

Displacements


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Results: Applied load is a Moment

Von Mises Equivalent

Stress

Maximum

Principal Stress

Displacements


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Overview: Fatigue Life Estimation


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Crack Initiation(E-N) is the selected method

1. Stresses and strains calculated froma linear static analysis

2. Material Properties: E-N Curve and Cyclic Stress-Strain Curve

3. Variable Amplitude Loading: cycles counting performed through

Rainflow counting method4. Neuber Correction to consider local plastic strain

5. Mean Stress Correction performed using either Morrow or Smith-Water-Thompson Methodologies

6. Damage Accumulation and Fatigue Life Calculation peformed using

Palmgreen-Miner rule.

Select Method for Life Estimation: Crack Initiation


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Note:

Ansys Design Life is not limited to crack initiation.

One may perform:

S-N analysis da/dN (Crack Propagation based of LEFM)

Vibration Fatigue (frequency domain fatigue lifeestimation)

Among other capabilities

Select Method for Life Estimation: Crack Initiation


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Material Properties

Anlise deFadiga


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Material Properties: Carbon Steel SAE1045_390_QT

Curva E-N

Curva Tenso Deformao Cclica

Propriedades extradas do banco de dados do Ansys Design Life


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nCode Material Propoerties Library Available


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Geometry for Life Estimation using FEM


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Geometry for Life Estimation using FEM


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Loading

Anlise deFadiga


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LOADING : FORCE

Loading History: Force x Time


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LOADING: MOMENT

Loading History: Moment x Time

F i l l i i A D i Lif


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Fatigue calculation in Ansys Design Life

F i l l i i A D i Lif


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Fatigue calculation in Ansys Design Life

Gliphs

Ambiente de clculo

R lt


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Results

Anlise deFadiga

R lt


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Results

R lt Lif


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Results: Life

R lt D


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Results: Damage

Results Spreadsheet format


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Results: Spreadsheet format

New Calculation Cycle (optimization)


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Anlise de

Fadiga



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One may change and try different values without running

linear static analysis again:

Material

Mean Stress Correction

Loading Value, Scale and Offset

Certainty of Survival

Other parameters ...


Conclusion


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A typical example of Fatigue Life Estimation was presented

Finite Element Method (Ansys WB) and Ansys Design Lifewere used to perform the analysis

Selected Method for Fatigue Life Estimation: E-N

Remember: Good Estimation is expected if you have good

imput data ( material properties, geometry and loading)

We expect to demonstrate the easy of useness and flexibilityof these calculation tools.

Conclusion

References


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[1] Bannantine, J.A. Comer, J.J., Handcrock, J.L.

Fundamentals of Metal Fatigue Analysis Prentice-Hall1990

[2] nCode - DesignLife Worked Examples:

3 AN-NC-DL-WE 14.50.083 2012 HBM UK Ltd.

References

Used Software


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1. Ansys Mechanical 14.5

2. Design Life - GlyphWorks V8.0 ISR3 Release Build 125

Used Software


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THANK YOU !!

OBRIGADO!!

ansys rotational fatigue presentation

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