How To Interpret Finite Element Results

Due to the evolving nature of the engineering analysis and simulation market this publication no longer represents current best practice and has been archived. The document may be of historical interest and is therefore still available for purchase.

The last two decades have seen major changes in the application of the finite element method. During the seventies the range of elements and their performance was improved. Application of the method was still fairly new and the learning curve was steep. Much of the change, particularly in the functionality of programs, was influenced by response from the growing number of users. The advances in the eighties were greatly influenced by the increasing power and reducing cost of computers, and the development of computer graphics. Development of solution techniques slowed, but powerful graphics based techniques for the modeling of complex structures were developed. Computer power hungry techniques for the solution of nonlinear problems became a practical reality. Development in the nineties has been dominated by the automation of the modelling process, involving adaptive mesh refinement and design optimization. These have led to the return to the theory to establish error estimating techniques and the development of p-type elements.

This set of booklets is mainly a snapshot in time, although there is some reference to the development of the method where it influences current practice, and some prediction of the future.

In these 'How to' booklets, theory and jargon are kept to a minimum. The authors have endeavoured to ensure the correctness of statements presented as fact, although simplicity gad often required that exceptions to rules be omitted. In the application of the finite element method there are many grey areas where the opinions of experienced practitioners vary. The opinions of software vendors are naturally coloured by their commercial interests. While the authors have aspired to be impartial, some of the booklet contents reflect their opinions as users of commercial software. For ease of reading the border between fact and opinion is not clearly delineated, but it is hoped that the context will distinguish between the two.

Contents

Preface

Introduction

Validation

• The Need for Validation
  
• Warnings
  
• Matrix Conditions
  
• Reactions
  
• Displacements
  
• Reduced Mass
  
• Stresses
  
• Stress Continuity and Convergence
  
• Stress Singularities
  
• Adaptive Mesh Refinement
  
• Review of Assumptions
  
• Summary
  

Presentation and Post-processing

• Presentations
  
• Load Combination
  
• Stress Averaging
  

Interpretation

• Model Behaviour
  
• Translation of FEA Results to Structural Behaviour
  
• Structural Integrity
  

Frame Example

• Warnings
  
• Matrix Conditioning
  
• Reactions
  
• Deflections and Deflected Shape Plots
  
• Reduced Mass
  
• Stresses
  
• Load Combination
  
• Review of Assumptions
  

Axi-symmetric Examples

• Warnings
• Matrix Conditions
• Reactions
• Deflections and Deflected Shape Plots
• Reduced Mass
• Stresses
• Stress Continuity
• Load Combinations
• Review of Assumptions

3D Shell Example

• Warnings
  
• Matrix Cinditioning
  
• Reactions
  
• Deflections and Deflected Shape Plots
  
• Stresses and Stress Continuity
  
• Load Combination
  
• Review of Assumptions
  

3D Solid Example

• Warnings
  
• Matrix Conditioning
  
• Reactions
  
• Deflections and Deflected Shape Plots
  
• Stresses and Stress Continuity
  
• Load Combination
  
• Review of Assumptions