See also Adam Powell's GF Website at http://www.ctcms.nist.gov/~powell/green

A workshop on "Library of Green’s Functions and its Industrial Applications" was held on Thursday and Friday, October 15-16, 1998, at the National Institute of Standards and Technology in Gaithersburg, Maryland. The goal of the workshop, sponsored by the National Institute of Standards and Technology, was to demonstrate the idea and application of a library of discretized Green's functions to industrial problems.

The workshop was held at the CTCMS computer room. A server was available for two participants. Each participant was given a temporary computer account. The workshop consisted of brief tutorials on the methods, a demonstration of the library, and hands-on experience with the library for the participants. Included were some new boundary element strategies associated with the library, for problems in stress analysis, fracture mechanics, ultrasonic wave propagation, and composite materials. Applications to other areas, such as acoustics, electromagnetic and thermal phenomena, were discussed. An open forum was held on potential uses of the library on specific industrial problems and its strengths and weaknesses. The plan is to make the library web based.

The inaugural talk was given by Dr. Sharon Glotzer, Director of the CTCMS. Dr. Les Smith, Director of the MSEL, visited the workshop on Oct 15 and met each participant. Dr. Hans Engler, Program director Mathematical and Computational Sciences Division, NSF, visited the workshop on Oct. 16.

An open forum was held on the second day in two parts. In the first part, all the industry participants were asked to comment upon various aspects of the workshop, in particular, about the potential usefulness of the GF library in their actual problems. A summary of the discussions and comments is given in Appendix A.

A questionnaire was given to participants on the first day with a request for them to fill out and return it on the second day. The questionnaire is given in Appendix B along with a summary of the responses.

The attendance in the workshop was free and by invitation only. Invitations were sent to scientists and engineers in several organizations, who we knew were interested in GF and BEM analysis. In addition, an announcement was placed on the CTCMS web site. People interested in attending the workshop were invited to write to us giving a brief description of the kind of problems in which they would apply the Green's function methods.

A total of 19 people attended the workshop, in addition to the PI (Vinod Tewary) and two principal collaborators (Frank Rizzo and John Berger). Out of the 19 participants, 8 were from industry, 9 from universities, and 2 from NIST. A university participant (Ravi Pandey) was sponsored by Dow Corning. The complete list of all the participants and their affiliations is given in Appendix C.

Dr. Steve Langer and Dr. Adam Powell of NIST were specially invited to attend the workshop, to give their expert comments on the software of the GF library. Dr. Powell's thoughts, now placed on the CTCMS web site, are given in Appendix D.

1. Industrial partners: Areas of industrial interest have been identified. The GF library will be further developed and adopted for application to these areas. One specific industry identified for this purpose is Ball Aerospace. We plan to start working on some problems of Ball Aerospace very soon. More industrial partners will be identified.

2. GF/ BEM consortium: Almost all the participants expressed a strong interest in using the GF library and joining the CTCMS working group as developers or users. A consortium has been formed with NIST in the coordinating role. A web-based tool developed at Kent University for scientific collaboration is proposed to be used by the consortium to communicate and collaborate on the use of the GF library.

3. GF library- second generation: We will develop the second generation GF library that would include more efficient mathematical algorithm, data structure, and GUI.

4. The solder connection: A new application of the GF library has been identified by Adam Powell in electronic packaging problems the solder group (see http://www.ctcms.nist.gov/~powell/green.html). A new working group is formed with Vinod Tewary and Adam Powell as PIs for this work that would mark collaboration between two different working groups (GF and Solder) of the CTCMS.

5. Another meeting/workshop: We plan to have another meeting/workshop after some time. In this workshop, the participants will describe the industrial problems that they addressed using the GF library and their first hand experience with using the library. We will also discuss the second generation library.

Dr. Laocet Ayari, Ball Aerospace (layari@ball.com)

Prof. John Berger, Colorado School of Mines (jberger@mines.edu)

Dr. Lingyun Pan, Caterpillar (panling@aol.com)

Prof. Frank Rizzo, Iowa State University (frizzo@cnde.iastate.edu)

Dr. Vinod Tewary (Chairman), NIST (tewary@boulder.nist.gov)

We express our gratitude to:

CTCMS for sponsoring the workshop and providing other support and help.

Dr. Shan Lu for computer programs.

Dr. Lingyun Pan for offering to make her Ph.D. thesis available.

Dr. Andy Roosen for help with all aspects of the computer work, and useful suggestions.

Dr. Adam Powell for very useful comments and suggestions

Mr. Bob Shephard for taking notes.

1. Caterpillar (Ivan Gonsalves):

Primarily use BEM analysis for fuel injection problems. Encouraged by the potential of the GF library.

GF library will be useful for analyzing multiple geometries.

Will enable design and analysis done by same people.

Turn around time is extremely important. GF library will allow numerous parameters to be changed.

It may be a good idea to switch to NT platform.

GF lib would be a big help: (a) with problems requiring lots of iterations, (b) with turnaround time in general. (c) There are still modeling and CPU problems with large finite element discretizations - there would be advantages for the GF lib and BEM here. (d) Gf lib and BEM would definitely help with (speedup) problems involving small changes (perhaps probabalistic data) in big complicated structures.

2. Allied Signals (Joe Chao):

Deal with flight safety issues. Search for flaws. Stress analysis for lifetime estimate. Need reliable method for flaw detection and to estimate which part should be scrapped. They are studying damage tolerances by analyzing cracks. The FEM is time consuming. They need to play "what if" games, such as by moving a flaw around a part and perform stress analysis. This can be done efficiently by using the GF library.

GF lib would be very good in NDE, for detecting flaws (inverse problem), and for

playing the many what-if games which are important in NDE.

Dr. Chao sees advantages in stress analysis as done in the company.

He is already using BEM/ GF library idea.

3. Ball Aerospace (Laoucet Ayari)

Build hardware for aerospace agencies such as NASA. Do stress analysis on components. Perform static and dynamic tests. They use FEM. Need a tool to assess stress field near cracks, predict flaw size and location.

GF library would provide basic solution for certain type of crack problems. He would like to use it. His colleagues don't know about GF. Some education would be needed. Suggested offering short courses on site.

BEM in general and GF lib in particular would be excellent

for the many problems in fracture mechanics which seem to be of primary

concern in the company. Education about the ideas seems to be an important

first step. There was also interest in almost everything done at the workshop.

4. Automated Analysis/ Comet Acoustics (S. Raveendra):

This company is already committed to BEM in a big way for acoustics problems of particular types.

In cases such as noise reduction problems in cars, where an analysis is not repeated, GF library would not be of much use. In cases such as architectural acoustics, concert-hall design, sound location and sound source identification, etc., the GF library would be very useful. For example, in concert hall acoustics, they need calculations like what happens if a certain instrument is moved from one place to other, or a certain absorber is introduced in the hall. In such cases where only "S2" changes, GF library would be useful.

GF library will be useful in acoustic holography. Methods for inverse problems will be useful to locate acoustic sources.

In general, GF library seems to be more suited to fracture, stress analysis, thermal problems etc. but may be tough for acoustic problems. However, he would consider using GF library for some acoustic problems; may be set up own GF libraries.

5. Digital Creators (Mike Edlin):

Very impressed by the software design. For placing the GF library on the Internet, JAVA would perhaps not work because it is not powerful enough for interactive calculations. CD ROM will be good. Suggested provision for downloading specific modules so that calculations can be done locally.

6. Automated analysis and Caterpillar (L. Pan)

Developing in-house BEM software for stress analysis. GF library will save time that is the chief advantage. It may have important applications in geomechanics (half-space calculations).

7. Dow Corning and MTU (Ravi Pandey):

Interested in interfacial failure. GF library will be useful in that kind of calculations. Dow Corning would be interested in exploring that.

8. Battelle (Raj Mohan)

Presently uses FEM. GF library would be useful in surface engineering. GF library should be particularly useful in diffusion calculations such as in electromigration problems.

9. SDRC (M. Rezayat)

The analysis component in the design of complicated structures is a real bottleneck. There are some new advantages to BEM analysis as portrayed by the GF lib idea, and when developed to their full potential for 3-D problems, there could be some revolutionary changes in speed of analysis to allow the highest level managers take notice. There is a real need for this. Nobody wants to do stress analysis anymore -especially if they have to wait at least 6 hours for it. They simply want graphical results instantly and somewhat reliably, but some sacrifices in accuracy can be made for speed. Nobody really cares about meshes, elements, etc., anymore.

The GF lib has potential for all of this. Indeed the workshop showed what is possible for 2-D problems. To be able to drag the circlular hole around on the interior of a structure, and see results of the analysis almost immediately, was very impressive and new. What we have is already valuable for some applications, certainly valuable for everyone as an educational tool for what is possible, and something of definite value in his organization if we can get comparable effects for 3-D problems.

GF library can be useful in doing real time calculations that would be useful in communication and collaboration in the analysis area. Speed of calculation is most important. GF library should be further developed to be applicable to materials of different shapes. With its present limitations, he does not think it would be useful to SDRC.

10. MTU (A. Chandra):

We should look carefully at the physics of the problem which will often dictate the choice of modeling scheme.

We should get a "shopping list" from the industry. We should define and target our initial goals.

11. ISU (Tom Rudolphi)

We are attempting to create a virtual handbook. The most important thing is that it should be easy to use.

12. CTCMS (Sharon Glotzer)

Form a working group/consortium of all the people involved. Promote direction; Problem formulation; Participation in providing ideas, sharing own experiences; Develop specific modules.

Feedback form (please also use the back of this page and extra sheets if needed)

Name:

Organization:

Brief description of the nature of your technical work:

Please list the aspects of the GF library that you feel would be useful to your work or that of someone else in your organization:

Please list the strengths and shortcomings of the GF library (criticism welcome)

In your view, how can the GF library be modified or enhanced to make it most useful to your organization, and, to the industry in general?

Do you anticipate using the GF library in your organization?

Are you interested in participating in our CTCMS working group either as a developer or as a user?

Any other suggestions/comments:

Fracture mechanics, stress analysis, and thermomechanics problems; interacting crack- microstructure problems; Interfacial failure.

Optimization of inspection probability of detection of flaws

Fatigue life prediction and lifetime of components

Analysis of engine components with complex geometry.

A generic GF generation utility, GF for different geometries.

Point and click approach to computing.

Storage of Green's functions.

Speed- advantages where only the RHS or a small component of the matrix changes.

Real time computation that enables efficient communication and online collaboration.

Electronic packaging- solder applications

Training and teaching tool

It accelerates solution of a problem, is CPU efficient, and saves time

Useful for repeated analysis on the same or similar system.

Ease of use through graphics and GUI

Excellent background information available

Very useful Point and click approach

Incomplete documentation

Lack of flexibility to meet specific industry needs.

Needs a lot of storage space.

No discussion of benchmark calculations.

Similar to the idea of static condensation in structural analysis and FEM

Identify areas where BEM is more useful than FEM

More real life 3D examples and applications, as well as optimization needed

Write a portable open-source BEM tool that would allow LU decomposed matrix storage.

Better graphical user interface; must be made very fast for large 3D problems.

Clearly illustrate the particular Green's function used in each module.

Detailed discussions should be held about the implementation in different industries, target end users, cost-benefit analysis etc.

Create a flexible hybrid (hard drive and web based) with a support/training system.

Better and detailed documentation should be available

Create a consortium for mutual exchange of experiences and ideas.

Anticipate using the GF library: Almost everybody said "yes"

Interest in joining the CTCMS working group: Almost every body said "yes"- as developer as well as user.

* Member, Organizing Committee

# Chairman, Organizing Committee

Industry (8), Academia (9), NIST (2); PI and collaborators (3); Total 22

(Available on http://www.ctcms.nist.gov/~powell/green.html)

In its current status the results appear to be

1.State of the art

2.Highly specific

3.Difficult to extend to new problems (except perhaps by the designers themselves)

In order to improve/broaden the mission of the GF Working Group: [Note: I've changed "Green's function library" to "Green's function database" for the following to prevent confusion with "software library". This can be changed back if it is too iconoclastic.]

1. A serious effort is needed to identify how a general tool would work. This means breaking down the separate processes of

i. Defining a standard format for meshes and LU-decomposed matrices, and an architecture for the database (heretofore called the "library") to store these matrices (e.g. using CORBA?).

ii. Building a software library of functions to create matrices*, create and read and store their decomposed form in the database, and use them to solve problems.

iii. Making a GUI that interfaces to that library.

2. Thus, there need to be several tools

i. A database builder

ii. A database user (calculating engine)

*The matrix creation part of the library needs to be written in an extensible/modular form to allow construction of matrices for new types of problems.

Necessarily the database builder will be for a more sophisticated user than the database user.