FEA Based Fatigue Design
- FEA Based Fatigue Design
- The Elements of a Life Estimation System
- An Overview of the FEA Based Fatigue Environment
- Different Philosophies and Life Estimation Models
- Design Philosophies
- Safe-Life
- Fail-Safe
- Damage-Tolerant
- Integrated Durability Management
- Life Prediction Methods
- Stress-Life (S-N, or Nominal Stress) Approach
- Strain-Life (Crack-Initiation or Critical-Location Approach)
- Crack Propagation Models
- The Stress-Life (S-N) Approach
- Defining Stress Cycles
- The S-N Curve
- Limits of the S-N Curve
- The Role of Stress Concentration
- The Influence of Mean Stress
- Variable Amplitude Response - Block Loading and Palmgren-Miner
- Variable Amplitude Loading - Rainflow Cycle Counting
- Material and Component S-N Curves
- Material S-N Curves
- Component S-N Curves
- FE Hints and Tips - S-N approach
- Component S-N Curves
- Nodal vs Element Averaging
- Spot Welds
- Welds
- KT and Kf Values Within an FE Model
The Strain-Life (e-N) Approach
- The Stress-Strain Curve
- Elastic and Plastic Strain
- Cyclic Stress-Strain Behaviour
- Cyclic Loading Under Strain Control
- Hysteresis Loop Shape
- Estimating a Strain-Time History
- Retaining Mean Stress Information
- The Strain-Life Curve
- The Effect of Mean Stress
- The Morrow Mean Stress Correction
- FE Hints and Tips - e-N Approach
- Element vs Nodal Results
- Weld Analysis, Component Material Curves and Composites
Crack Propagation Analysis Using LEFM
- Fatigue Cracks Start
- The Concept of Stress Intensity
- Fatigue Crack-Propagation and LEFM
- Stresss Intensity Factor K Versus Compliance-Function Y
- Nominal Stress With a Compliance-Function in FE Based Crack Growth Calculations
- FEA in Generating Compliance-Functions
- Using Fracture Mechanics in Damage-Tolerant Design
- Aircraft Engine Mounting Lug FE Based Fatigue Analysis
- S-N Analysis
- Crack Growth Prediction
- FE Hints and Tips - Crack Growth
- The Use of Crack Tip Elements
- Picking a Nominal Stress
Multi-axial Fatigue Analysis
- Multi-axial Stress-Strain States
- Separate Tensile and Torsion Loading
- Combined Tensile and Torsional Loading
- Characterisation of Stress States
- Proportional Multi-axial Responses
- Equivalent Stress-Strain Approaches
- Dealing with Non-Proportional Responses
- FE Hints and Tips - Multi Axial Fatigue
- 3D, 2D and 1D Models
- Multi Modal Response to Single Input Loading
Vibration Fatigue Analysis
- Alternative Descriptions of Engineering Processes
- The Frequency Domain
- Power Spectral Density (PSD)
- Characterization of Engineering Processes Using Statistical Measures
- Time Histories & PSDs
- Expected Zeros, Peaks and Irregularity Factor
- Moments From a PSD
- Expected Zeros, Peaks and Irregularity Factor From a PSD
- The Transfer Function
- Modal Transient (Superposition) Fatigue Analysis
- Fatigue Life Estimation From PSDs
- Time Domain Stress-Life Fatigue Life Estimation
- S-N Relationship
- Estimating Fatigue Life From a Stress pdf
- The Frequency Domain Model
- Narrow Band Solution
- Empirical Correction Factors (Tunna, Wirsching, Hancock, Chaudhury and Dover)
- Dirlik's Empirical Solution for Rainflow Ranges
- Bishop's Theoretical Solution for Rainflow Ranges
- Clipping Ratio as a Function of rms
- Simple Vibration Fatigue Hand Calculation
- Time Domain By Hand
- Frequency Domain By Hand
- Computer Based Calculations Using MSC.Fatigue
- FE Hints and Tips - Vibration Fatigue
- Calculation of Frequency Response Function (Transfer Function)
- Verifying Vibration Fatigue Results
FE Model Building and Post Processing Issues
- Introduction
- Process Issues
- Model Building
- Requirements
- Observations
- P-type element
- Meshing
- Dealing with Loads
- FEA Based Global Analysis Options
- Analysis Options
- FE Results output type
- FE Based Local Analysis Options
- Absolute Maximum Principal Stress and Signed Von Mises
- The Choice of Element Centroid Versus Nodal Results
- Pre Processing of Loading Data
- Post Processing of FE Based Fatigue Results
- Accuracy of Fatigue Life Estimates
- General Conclusions
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