Tips and Workarounds for CAD Generated Models
This book is an update of a previous document by the same name, written almost ten years ago. During the intervening period the world of analysis has moved on, especially in the area of CAD integration. It is arguable whether the field has moved on as far as was predicted or hoped for in 1999, but move on it has.
There have been both across the board enhancements to the functionality of CADintegrated analysis tools and a major increase in the numbers of CAD users who have access to analysis software as a result of vendors bundling finite element analysis software with mid-range CAD systems. So, with more and better software available, has this generated the benefits, or even the dangers, as predicted? In the author’s opinion, it has really not achieved either; the take up, although considerable, has probably not yielded many of the hoped for benefits but conversely the dangers have not, for whatever reason, manifested themselves greatly either.
So there is still much to be done; further business benefits can be accrued by fullyimplementing analysis, although this is still not without risk. By updating this book it is hoped to assist progress towards the safe and profitable implementation of CAD-integrated analysis technology.
This book is principally aimed at design engineers who have yet to become involved with Engineering Analysis but are thinking of undertaking analysis studies as part of their design work. It is also intended that the examples presented, along with some of the advice, should be relevant to the more seasoned analyst who has yet to take advantage of the integration of CAD and Analysis.
Although the examples presented in this text are derived from stress analyses, the points made are applicable in other contexts such as thermal or dynamics analysis.
It is assumed throughout this book that analysis is to be used by professionally qualified engineers who are already designing components or structures. Although such issues are covered in subsequent chapters, the current vogue of assuming that anyone capable of ‘driving a CAD system’ is capable of high level engineering design is certainly not endorsed by the author.
In addition to those who have made the decision to purchase an analysis system, there will be others who acquire such systems inadvertently, simply finding it embedded within their chosen CAD system. Although not a feature of the higher level programs such as CATIA and Unigraphics, mid-range CAD systems (eg SolidEdge, SolidWorks and Inventor) now all come with some form of finite element analysis system. This has massively increased the number of analysis systems in circulation but has, correspondingly, increased the number of unused systems. It is this situation that gives rise to the greatest risks, because users who have been given a system are less likely to seek adequate training or advice.
Worse, those who have little contact with the analysis world may remain blissfully unaware of the pitfalls. Addressing all the issues raised by this is perhaps beyond the scope of this book!
The best time to read about the technical discipline and art of analysis is prior to purchasing a system, as suggested above; it is more than likely, however, that the reader will have already purchased such a system and it is in this situation that ‘Tips and Workarounds’ may be of the greatest relevance. It is assumed that, at the time of writing, everyone involved with Engineering Design will have access to a CAD system; though, as we shall see not all CAD systems are equal.
Finally, the experienced analyst may also find useful information here. The automation of processes, which makes analysis possible for the less experienced design analyst, can also help reduce the workload for the experienced analyst.
The content of this book is broken down into several distinct topics; initially the issues concerned with gaining the maximum benefit from the use of analysis integrated into the CAD environment are covered and then specifics, such as the difficulties encountered with various types of modelling problem are addressed.
2. Analysis within the CAD environment
2.1 Why Get Involved with Analysis?
2.2 Who should be involved with Analysis?
2.3 Why Integrate CAD and Analysis?
3. Types of Integration
3.1 Transfer of CAD Data using intermediate file format
3.2 Direct Transfer from CAD System to Analysis System
3.3 Fully Embedded Analysis Systems
4. Integrating Analysis into the Design Process
4.2 The stages at which analysis can be applied
5. CAD Integration – a double-edged sword
5.1 Model Geometry
5.2 Types of CAD Data
5.3 Model Quality
5.4 The availability of an CAD model
6. Technical Issues relating to Integrated Analysis
6.1 Small Features
6.2 Data Transfer Problems
6.3 Model Quality Issues
6.4 Analysis of Thin Walled Components
6.5 Strategies for the control Mesh Density
6.6 Treatment of Assemblies
6.7 Loads and Boundary Conditions
7. Advanced Analysis in the CAD Environment
7.1 Forced Vibration Analyses
7.2 Non-linear Analysis
7.3 Fatigue Analysis
7.4 Computational Fluid Dynamics
8. Vertical Applications
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First Published - January 1999
Revised and Republished - August 2008
Softback - 51 Pages