1 This is the list of frequently asked questions for FElt
3 last modified: 07-16-95
6 What kinds of problems can FElt solve?
7 Can FElt solve my type of problem?
8 Can I modify FElt to make it solve my type of problem?
9 On that same note, can I add new kinds of elements?
10 2. Where can I get FElt?
11 3. What machines does FElt run on?
12 Is there a Windows interface to FElt?
13 What about a Motif or OpenLook interface?
14 Can I compile FElt using X11R4 (R3 ...) ?
15 Where can I get gzip to unpack the tar files on cs.ucsd.edu?
16 4. I think I found a bug, what now?
17 5. Is there a newsgroup or mailing list for FElt?
18 What kind of things should I post to the mailing list and what kinds of
19 things should I contact the authors for?
20 6. Why do the FElt components have such stupid names?
24 FElt is a free system for introductory level finite element analysis. It is
25 primarily intended as a teaching tool for introductory type courses in finite
26 elements - probably in the mechanical/structural/civil fields. In a command
27 line environment, FElt uses an intuitive, straightforward input syntax to
28 describe problems. It also includes a graphical user interface for
29 workstations that allows the user to set-up, solve and post-process the
30 problem in a single CAD-like environment.
32 From the end-user point of view, FElt consists of six programs: felt, burlap,
33 velvet, corduroy, patchwork, and yardstick. felt is the basic command-line
34 application; burlap is an interactive Matlab-like environment for scripting
35 your own elements and analyses; velvet is the primary GUI interface into the
36 bulk of the functionality in FElt; corduroy is command-line program for
37 automatic element generation; patchwork is a command-line application for
38 file format conversion to and from the FElt syntax; and yardstick is a simple
39 program for problem scaling and unit conversion.
41 Felt is the simplest - it takes a FElt input file and spits back appropriate
42 ASCII based (tabular or ASCII graphics) results depending on the problem
43 type. The command line application felt is the only interface of the three
44 analysis engines (felt, velvet, burlap) that is available under DOS.
46 Velvet is the most powerful interface into the pre-programmed functionality
47 of FElt - it allows for complete graphical problem definition through
48 pulldown menus, popup dialog boxes and an interactive drawing area. It
49 offers all of the capabilities of both felt and corduroy and has several options
50 for post-processing, including color stress plots for planar elements, plots of
51 the displaced structure, animation, graphical time-displacement plots for
52 transient analysis problems, graphical frequency domain plots of transfer
53 functions and output spectra for spectral analysis, and graphical plots of
54 mode shapes for modal analysis problems.
56 Burlap is the most powerful interface in terms of raw FE computing power
57 simply because you can make it perform analyses that are not otherwise
58 available in FElt simply by scripting your own analyses algorithms in burlap's
59 powerful Matlab-like syntax. You can also use burlap to try out new element
60 definitions quickly and easily or to manipulate the results from one of FElt's
61 pre-programmed analyses in a novel way that is otherwise not provided for.
63 What kinds of problems can FElt solve?
65 As distributed, FElt can solve the classic problems in linear statics and
66 linear dynamics for both structural and thermal mechanics (i.e.,
67 problems of the form Kd = F, Md'' + Cd' + Kd = F , or Md' + Kd = F).
68 It can also solve the generalized eigenvalue problem (K - lM)x = 0
69 and use this information in modal analysis. It can do spectral
70 (frequency domain) analysis of transient structural problems. The
71 element library consists of truss, beam (Timoshenko and Euler),
72 constant strain triangular, bilinear planar isoparametric, plate bending
73 (selective reduced integration quadrilateral), isoparametric solid (eight
74 node brick) elements, and rod and constant temperature gradient
77 Can FElt solve my type of problem?
79 Unless it fits into one of the classes above there are no built-in solvers
80 for your type of problem. You may be able to use burlap to write your
83 Can I modify FElt to make it solve my type of problem?
85 Probably, and we'd be happy to help. The only reason FElt cannot do
86 more right from the start is partly because we don't have time and
87 partly because it is very hard to keep everything simple,
88 straightforward and intuitive if we support every different type of
89 analysis and algorithm - especially because beyond the basics there
90 are so many different possibilities. What may interest one person on
91 the serious research level is probably not going to interest the majority
94 FElt does offer a lot of basic support that would be useful in a broad
95 class of finite element programs. If you do want to add your own
96 analysis algorithms, the best place to start is to probably look at the
97 source code for the felt driver program (bin/Felt/felt.c) and see how it
98 handles switching between static, dynamic and modal analyses. Then
99 take a look at the routines for static (lib/Felt/fe.c), dynamic
100 (lib/Felt/transient.c), modal (lib/Felt/modal.c), and spectral
101 (lib/Felt/spectral.c) problems to see how the different types of
102 algorithms make use of the data structures and general routines to
103 actually go about getting a solution.
105 Finally, we want people to know that our major motivation for
106 creating burlap were questions just like this. With burlap you now
107 have two options for performing analyses that don't already exist -
108 you can modify and add to the FElt source as outlined above or you
109 can script your algorithm in burlap. The latter is probably much easier
110 and we encourage people to try it out. If we do end up with a lot of
111 neat analyses scripted into burlap then perhaps we can start putting
112 together a library of this functionality for general distribution. That
113 kind of growth in functionality sounds a lot nicer to us because it would
114 be a lot easier to maintain and distribute.
116 On that same note, can I add new kinds of elements?
118 Absolutely, there's even a whole chapter in the user's manual devoted
119 to this very topic. We'd be very interested if you did add a new
120 element because we'd like to start putting a user contributed element
121 library together for distribution with with regular sources.
123 Also, just like you can add your own new analyses through burlap,
124 keep in mind that you can script new elements in burlap as well. This
125 is a potentially much easier way to go about it. Whichever way you
126 choose to go about it, let us know what you come up with - we'd like
127 to hear whatever success (or horror) stories people might have.
129 2. Where can I get FElt?
131 The latest version of FElt, in all its incarnations, is always available via
132 anonymous ftp from cs.ucsd.edu. Once you have ftp'd to cs.ucsd.edu login as
133 anonymous and give your email address as the password. cd to /pub/felt and
134 grab whatever files you need for your particular situation. As of this update,
135 the latest version is v3.00. Information (and hypertext access to the ftp site)
136 is available via World Wide Web (e.g., Mosaic) at
138 http://www-cse.ucsd.edu/users/atkinson/FElt/felt.html
140 if you want to take a more serious look at some of FElt's capabilities before
141 you actually take it for a test drive on your machine.
143 3. What machines does FElt run on?
145 The complete version of FElt (including the X11 based graphical user
146 interfaces) has compiled and tested on HPs, DECs, Suns, SGIs, 386/486s
147 running Linux and SysV R3, and IBM workstations. It should do the same on
148 any reasonable Unix system with X11R5 or R6. In general we provide
149 binaries for Sparc stations running SunOS or Solaris and 386s with Linux, but
150 there is no guarantee that the binaries are as up to date as the source code.
151 When in doubt just grab the source code and build it yourself - really, it's
154 DOS executables are available for the command-line applications felt,
155 corduroy, yardstick, and patchwork. A simple graphical application, feltvu is
156 also available. You need to have at least a 386 to use the DOS versions.
158 Is there a Windows interface to FElt?
160 Not yet, and we're probably not the folks to write it as neither of us
161 have much experience with Windows programming. If someone else
162 would like to volunteer then I'd suggest starting with something like
163 xfelt as it's really pretty simple. There may be people working on this
164 - let us know if you're thinking about something like it and we'll try
165 our best to make sure that people don't duplicate a lot of effort.
167 What about a Motif or OpenLook interface?
169 Well we originally chose to work with the Athena widgets because
170 the price is right and because they allow us to maintain FElt as a 100%
171 free product. With the current set-up anyone (in theory at least) can
172 get and build everything they need to get FElt up and running free. If
173 we had worked in Motif then we at least would have had to shell out
174 for Motif for Linux and people without Motif simply would be out of
175 luck unless they happened to be working on one of the few machines
176 that we could provide statically linked binaries for. We also recognize
177 that we could maintain separate GUI interfaces, but we feel that our
178 development time is better spent on functionality rather than on
179 constantly keeping two or more separate interfaces up to date. In
180 addition, it's our feeling that Motif or OpenLook or any other widget
181 set would not offer us any significant additional capabilities that we
182 haven't already worked out with the Athena widgets.
184 However, if you just want a slightly different look and feel than the
185 stylized default look of velvet then please feel free to change it - that's
186 what Xresources are for after all. The easiest way to get a slightly
187 more Motif look (not really the feel though) is to switch to the 3d
188 Athena widgets. I know that these are readily available as compiled
189 libraries for Linux and should be for some other machines as well;
190 they're also really easy to build yourself if you are so inclined. Once
191 you have them all you have to do is swap them for your regular
192 Athena shared library (or re-link if you don't use shared libs); the
193 next time you run velvet everything should be 3d. There are some
194 recommended changes to the app defaults for velvet if you do decide
195 to go this route, they're at the bottom of Velvet.ad in src/Velvet.
197 Can I compile FElt using X11R4 (R3 ...)?
199 Not really - you really should have X11R5 or R6. Compiled libraries
200 should be available for most machines. If not, source code for the
201 X11R5 distribution is available via anonymous ftp from ftp.x.org and
202 pre- compiled libraries should be available from many places on the
203 net. Now that X11R6 is available you should be able to use that just as
206 If you really want to do it with X11R4, then you can try the following:
207 from ftp.x.org get three header files from the untarred R5 or R6
208 sources - Xfuncs.h, Xfuncproto.h, Xosdefs.h. Make a directory
209 FElt-x.xx/inc/X11 and copy these three files into it. Then just do a
210 regular make as described in the INSTALL file. See the notes on
211 SGIs in the INSTALL file if you need a few more details.
213 Where can I get gzip to unpack the tar files on cs.ucsd.edu?
215 Source code is available from prep.ai.mit.edu. Binaries for a wide
216 variety of machines should also be available from various archives on
217 the net. Building gnu binaries from source is really easy, just untar
218 them, cd into the directory into which they unpacked, type configure
221 4. I think I found a bug, what now?
223 Send one of us email (jgobat@mit.edu or atkinson@ucsd.edu). Please,
224 please, please, include as much information as possible in your report. Things
225 that are absolutely essential:
226 version of FElt that you are using
227 the application that you think the bug is in (felt, velvet, everything,
228 etc.), this is particularly helpful if the bug only shows up in velvet but
229 not in felt (or the reverse)
230 type of machine and operating system (including the OS version) that
232 if you are using a pre-built binary or if you are using a binary that you
233 built yourself; if you built the binary, how did you build it (gcc, native
235 and of course a detailed description of what went wrong and what you
236 were doing when it went wrong. If possible send us the input file that
237 causes the problem, if you can't do that then tell us what kind of
238 analysis you are doing and any other relevant details specific to your
241 5. Is there a newsgroup or mailing list for FElt?
243 There is a mailing list. To subscribe to the list send a one line email message
248 to listserv@mecheng.asme.org. To send a message to the list just send it like
249 regular email to felt-l@mecheng.asme.org. Incremental release
250 announcements and bug fixes will be posted to the mailing list. Major release
251 announcements will be made to the following newsgroups:
252 comp.os.linux.announce, sci.math.num-analysis, sci.engr, sci.engr.civil, and
253 sci.engr.mechanical. So if you really want to keep up on new versions and
254 capabilities, you should subscribe to the mailing list.
256 What kind of things should I post to the mailing list and what
257 kinds of things should I contact the authors for?
259 The list is generally for announcements, bug fixes, and questions that
260 several FElt users might have an interest in (i.e., I'm trying to make
261 FElt solve a problem like xxx, how have other people modeled this? or
262 I really think that velvet should be able to do xxx, what does everyone
263 else think?). We'd also like it to be a forum for discussion of what
264 types of things people would like to see in FElt.
266 For bug reports that you think are specific to your machine or things
267 that other users probably don't have an interest in, feel free to send
268 email to one of us: jgobat@mit.edu or atkinson@ucsd.edu. See the
269 question on bugs for details on how to submit a bug report.
271 6. Why do the FElt components have such stupid names?
273 Well, FElt is obvious, right? Finite ELemenT. felt the application came first -
274 it's the most basic interface into the system. Now when it comes to fabrics,
275 everybody knows that velvet is smoother than felt ... thus the slickest GUI
276 interface is called velvet. xfelt is simply xfelt because it is nothing more than
277 an encapsulator, with no real functionality beyond that provided by felt.
279 After this, we start to stretch because with the felt - velvet connection we
280 have this fabric motif to keep up on.
282 - Burlap is rough but functional, just like its namesake fabric. It may not be
283 as easy to use as velvet (or maybe it is if you like scripting in Matlab-like
284 mathematical languages) but you can do an awful lot with it.
286 - Corduroy has that regular ripple effect so its sort of like a mesh ...
288 - Patchwork, well we figured that was better than convert simply to avoid
289 conflicts. How many systems have some local app called convert to do
290 whatever, or how many little hacks are there called convert. It seemed
291 common enough to us that we figured we might as well call it something
292 different. Patchwork implies a lot of different fabrics coming together so it
293 seemed as good as anything else.
295 - A yardstick is used to measure fabric ... measuring implies some sort of