Subject: New mechanical free site
From: Jean-Luc MARTIN
Date: Tue, 17 Sep 1996 12:54:11 -0700
Hello,
From france, I inform you that a new mechanical site can be reach at :
http://www.machpro.fr
Over 8500 free pages can be consult.
The biggest french site...
Machining centers, Milling machines, Drilling, EDM, cutting tools, etc...
Have a nice surf :-)
Jean-Luc MARTIN
jlmartin@machpro.fr
Subject: Re: Bolted connections in composites
From: jnsingle@unity.ncsu.edu (James Neal Singletary)
Date: 16 Sep 1996 14:02:18 GMT
Oroginal poster wrote:
>> I'm reviewing someone else's design of a bolted connection in a composite
>> structure (a metal plate loaded parallel to a glass reinforced plastic
>> plate with several bolts in essentially single shear)....
Barry Berenberg (berenberg@caent11.esa.lanl.gov) wrote:
> ...On a project a few years ago, we had to answer this same question. We
> ended up running tests of representative laminates. The bearing
> strength depends not only on the strength of the laminate, but on the
> proportion of different angle plies (you want about equal amounts of
> 0, 45, and 90 plies), and on the amount of fabric versus tape (fabric
> is much better). The bearing strength is also highly dependent on the
> pre-load of the bolt. In our case, a fully-torqued joint had a
> bearing strength greater than twice that of a pinned joint...
The original poster cited a typical fiber volume fraction of his
composites as 35%, from which I assume that the fibers are a mat,
not unidirectional laminate or cloth. However, I would like to
ammend the last poster's implication about whether or cloth laminates
have generally better bolt strength in general than laminates, or
visa-versa.
From what I have seen in the literature, the conclusion about which
reinforcement system has a better bolt-bearing strength is contradictory
and somewhat inconclusive. Some researchers consolidate a panel, and then
drill through it, and test that. Others form the fiber architecture with
a hole already in it (be it a random mat, or a cloth preform woven or
braided around a pin), and then consolidate and test that. Honestly, it
seems that the composite with the strongest bolt-bearing strength is always
found to be the one that the rsearchers spent the most time making...
I do not know if the question of whether or not cloth-reinforced composites
have better bolt bearing strength than nominally similar laminated
composites, and why so many previous researchers have reached contradictory
conclusions, has yet been authoritatively resolved.
I am sorry to wax a little academic -- this probably isn't of much concern
to the original poster...
Regards,
James Singletary
--
Jumpin' James Neal Singletary |
NCSU College of Textiles | ``Blond. Spritzig. Wuerzig.''
(919) 515-4399 |
Subject: Re: Publishing Scholarly Work on the Web -- opinions?
From: "Matthew W. White"
Date: Tue, 17 Sep 1996 10:25:33 -0400
I think you have to consider two aspects of this discussion:
First, what is "publishing" with respect to scholarly works? The peer review process for technical
publications and the editoral process of the popular press add credability and legitimacy to the work in
question. A researcher can employ a vanity press to print a book with his pet theories without
consideration of merit. Thus you have to take a very guarded approach to using these references. Just
publishing faster w/o regard to quality is not an answer.
Please don't get me wrong - I think the WWW is the wave of the future for making technical information
available. Edison Welding Institute has established a site just for this purpose, and we include documents
and links to non-reviewed and interim works. However, we try to distinguish between these and papers which
have undergone more scrutiny. There are also some documents which we do not include, as they don't appear
to be credible sources. This is a critical role for all organizations which attempt to provide public
information services
Second, how do you reference these documents? Hopefully you can identify the author and the site from
which you accessed the document. I would think you would want to perform some additional verification of
the author, etc. Also, subject to copywrite restrictions, I think one would want to keep a copy of the
document (hard copy and/or file). At this point, I don't think you can depend on archives.
Matthew W. White
Edison Welding Institute
http://www.ewi.org
matthew_white@ewi.org
Subject: Re: Assistance needed with o-ring problem
From: soffiler@stealth.mc.ti.com (Steve Offiler)
Date: Tue, 17 Sep 1996 09:30:22
In article <51l66h$8sa@uhura.phoenix.net> jflester@phoenix.net (Jeff Lester) writes:
>From: jflester@phoenix.net (Jeff Lester)
>Subject: Assistance needed with o-ring problem
>Date: Tue, 17 Sep 1996 03:38:14 GMT
>I have an o-ring problem. I have a radially compressed
>o-ring with a 5/16" cross section diameter. The joint
>is a static one sealing primarily air. The operating temp
>is approximately 300 degF and operating pressure is
>90 psig. The o-ring is also exposed to water and small
>concentrations of anhydrous ammonia.
>Any ideas on material...? What would the recommended
>gland dimensions be?
>Any assistance would be appreciated.
>Sincerely,
>Jeff Lester
Jeff:
Give Parker O-Rings a call. (Dang, can't find my catalog right now or I'd
give you the number...)
Their catalog contains a wealth of useful, practical design and application
information. I've used it successfully many times in the past.
Stephen B. Offiler, P.E.
Subject: Re: New mechanical free site
From: niemotka@tetraprec.com
Date: Tue, 17 Sep 1996 12:49:11 GMT
If you are interested in machine tool accuracy and precision, and a
new instrument to measure it, check out http://www.tetraprec.com/tetra
Jean-Luc MARTIN wrote:
>Hello,
>From france, I inform you that a new mechanical site can be reach at :
>http://www.machpro.fr
>Over 8500 free pages can be consult.
>The biggest french site...
>Machining centers, Milling machines, Drilling, EDM, cutting tools, etc...
>Have a nice surf :-)
>Jean-Luc MARTIN
>jlmartin@machpro.fr
Subject: Re: Which engineers are more in demand?
From: "Joe Boothe"
Date: Tue, 17 Sep 1996 17:03:53 GMT
It is really personal preference. If you specialize, like aerospace, You
can limit your self on the jobs you can get. Basically, an car company
would most likely hire a Mechanical engineer over an Aerospace. This is my
opinion thought and if I could do it agian I think I would go Aerospace or
lean towards that in ME.
t0kx@unb.ca wrote in article <32374FD7.7A60@unb.ca>...
> Of mechanical, electrical, and aerospace, which engineer is more in
> demand? And which would you do if you were interested in all 3? (or
> all 8 for that matter) Thank-you kindly.
>
>
Subject: Re: Publishing Scholarly Work on the Web -- opinions?
From: doolin@menkar.cs.utk.edu (David Doolin)
Date: 17 Sep 1996 11:44:13 GMT
In article <323DB1F3.2781@mae.carleton.ca>, Chad English writes:
|> Kirk Kerekes wrote:
|>
|> Agreed. But that's not quite the issue I was bringing up. A conference and a
|> journal issue are events that occur in time. Even with a medium change, you
|> can (hopefully) find information from either of those by referencing the
|> event. Using a URL is like referencing the library, not the event. If the
|> URL is permanently associated with the paper, which doesn't make sense down
|> the road when things change (URL's change, storage mediums change), then it's
|> not a problem. I was just looking for a way to permanently reference the
|> paper. Perhaps if we approached the archive as a series of journals, give it
|> a permanent name, etc, and then use the dates, it may be better.
|>
*We* have one good shot at doing this right, 'cause it will get done.
As an unpublished (no refereed pubs) grad student, I find the issue
particularly relevant and interesting. What I have done is convert
my stuff (conference offprints) to html and stick them on my web page.
I include the name of the copyright holder and that the documents are
offprints from such and such conference. Since I use LaTeX, html is
no extra effort, I just type a command and out pops the html, graphs, tables,
figures, references, etc.
What I am curious about is how the copyright holders are going to
deal with it.
In my opinion, ED's (electronic documents) ought to be archived by a dedicated
server similar to a library. The peer review system probably should
stay more or less intact. Publication would consist of periodic
collections of peer reviewed material available online under a
title. The geotechnical community is expecting it's first issue
of just such a `journal.'
This is going to be really interesting. As an interdisciplinary
effort, it had better include the library science folks as well
as the science and engineering community.
Dave D
|>
|> > How many 50-year-old academic papers have you _directly_ referenced?
|>
|> Well, I can think of at least 2 greater than 50, and quite a few in the 25-30
|> years ago range, from my Master's thesis alone. Some fundamental works will
|> be referenced for quite some time.
|>
|>
|> --
|> ("`-''-/").___..--''"`-._
|> `6_ 6 ) `-. ( ).`-.__.`) Chad English
|> (_Y_.)' ._ ) `._ `. ``-..-' cenglish@mae.carleton.ca
|> _..`--'_..-_/ /--'_.' ,' http://www.mae.carleton.ca/~cenglish
|> (il).-'' (li).' ((!.-'
--
David M. Doolin Institute for Geotechnology
doolin@cs.utk.edu Department of Civil Eng. UTK
__________________________________________________
You may add me to your junk email list for $1000.00,
payable in US currency. Otherwise, don't call me,
I'll call you. Sending me junk email from a list
obligates you to this contract.
_________________________________________________
Subject: Re: PE Liability
From: "Kevin Rhodes, P.E."
Date: Tue, 17 Sep 1996 11:53:59 -0700
Eric Mieczkowski wrote:
>
> Thanks for an excellent reply. Let me run through this with you and make sure I'm
> understanding it all.
>
> hobdbcgv@aol.com wrote:
> >
> > < SNIP >
> >
> > There is at least one common thread, however. If you perform work
> > which involves "technical matters relating to life, health, safety, or the
> > public welfare" and are not a licensed PE, you are "liable" from actions
> > contrary to law and "liable" for punishment under the law, that separate
> > from any civil actions under "tort law".
>
> So, if you're not a licensed PE and your work violates some aspect of the law,
> you're criminally liable in addition to being civally liable. Let me turn this
> one around. If you DO hold a PE license and your work violates some aspect of the
> law, are you liable in the same manner (i.e. criminal and civil)?
>
> >
> > < SNIP >
> >
> > Also, sometimes having the PE responsibilty allows the corporate veil
> > to be pierced because corporations cannot "own" the license and thus the
> > actions are viewed as the joint and several responsibility of the person
> > and the corporation.
>
> What you are saying is that by obtaining licensing as a PE, I can no longer be
> treated as a member of a corporation for liability purposes, but rather exist as a
> seperately liable legal entity.
>
> If I am reading this correctley, what seems to be true is that criminal liability
> is reduced or eliminated by PE licensing, but the risk of civil liability is
> increased.
>
> Thank you sincerely for helping me wrestle with this. I just can't seem to get
> good information on this anywhere.
>
> Eric
I run an engineering firm in Kentucky. Not only am I licensed by the
Board, but so is my firm. Hope it helps.
Subject: Re: aluminum on steel linear bearings?
From: hobdbcgv@aol.com (Hobdbcgv)
Date: 17 Sep 1996 15:51:29 -0400
A couple of the sintered bearing makers design booklets had information
on aluminum on steel guides. OilLite was one.
As I remember on the guides I made, and per sources, all was well if
you kept the loads under 50 psi. I felt these levels were acceptable more
to keep the penetration thru the oxide down, because within hours of
opening the aluminum forms aluminum oxide, which is very hard and wears
extremely well, but even when deep anodized is only a thousandth thick.
The steel can easily deform the softer under-aluminum.
Wore like iron, ruined if a steel part was dropped on it.
Hope it helps.
Subject: Re: Publishing Scholarly Work on the Web -- opinion anyone?
From: Nick Kew
Date: 16 Sep 1996 22:27:16 GMT
> I agree and support the concept. The problem I see is that it may be
> that many of the scientific journals will not be happy about being
> second in line for a paper though it could force them to provide
> electronic subscriptions.
My original suggestion is to hold *abstracts* online, with the provision
to hold full papers where appropriate. Keeping abstracts in an easily-
searchable website would surely be a valuable service to researchers,
while referring them to the traditional publishing media for full papers.
My software will index and cross-reference the abstracts, and has the option
to hold any or all of the full papers online according to publisher choice.
As others have pointed out, the peer-review process is an important element
of academic publishing. I believe web-based collaboration software can
be used to facilitate this process, providing a forum ("workgroup") whose
members are a paper's authors together with recognised referees in a
subject area. Such papers may have readonly access to the general public
(or subscribers-only if a publisher prefers) while in the review process,
thus accelerating the publication cycle.
The technology is ready: we need only apply it!
Nick Kew.
Subject: Re: isolation of conducted noise
From: hobdbcgv@aol.com (Hobdbcgv)
Date: 17 Sep 1996 15:31:06 -0400
Is the noise continuous or singular? (a steady hum or a single ping or
bang)
Since there is a wavelength associated with mechanical vibration and
you're probably not seeking active control, if you can determine the
frequency you can then add an equivalent spring-mass system to remove the
noise (such as a "bulbed" tab on a lead along the axis of the offending
system) , you can isolate using parts whose natural frequency is less than
the offending frequency (like using a series of "zig-zag"ed heat
conductors rather than one wire), or you can damp it out with a conducting
elastomeric such as 3M rubber electrical wrapping tape (NOT ordinary
rubber electrical wrapping tape) -note this is not the common electrical
tape used for insulating electrically.
If it is a singular "ping" and it involves heat, you almost always find
it by looking for a contained device that can suddenly release when
heated, and removing the restraint.
There are other more exotic sources for noise, but I think these are the
most common/easiest fixes.
Let me know what you find.
Subject: FEA question
From: milesb@leland.stanford.edu (Craig M. Lawrence)
Date: Tue, 17 Sep 1996 11:12:42 -0800
I am performing a 2-D, plane-stress, linear static analysis using ANSYS,
and I am running into a "small negative pivot" error which prevents the
analysis from running. I was under the impression that this error can
occur when the model is not properly constrained, and you obtain
rigid-body motion. I believe I have constrained my model correctly, but I
still get the error. Are there other potential causes for a small negative
pivot error?
Thanks,
Craig
*****************************************
Craig M. Lawrence
Ph.D. Candidate
Mechanical Engineering - Design Division
Stanford University
email: milesb@leland.stanford.edu
phone: (415) 725-1595
fax: (415) 723-3521
******************************************
Subject: Re: Question about Creep
From: hobdbcgv@aol.com (Hobdbcgv)
Date: 17 Sep 1996 16:09:29 -0400
It is my understanding that springs have some residual stresses from
the forming process, and this can affect spring performance. I have heard
this change in residual stress, as well as changes from overworking,
referred to as spring creep, which is different than creep in materials.
I have some reference materials regarding creep in materials, but the
stresses at which these occur would be beyond any reasonable spring
design. I would think that any spring using that high a stress would have
very short-lived and deteriorating spring characteristics.
I would check in a good spring design book. I think Alllied Spring had
a good one. Unless it's a materials research project, you're probably
safer to stick with available spring materials.