Subject: Re: Is Mechanics of Materials misleading ?
From: Ben Sauvin
Date: Wed, 2 Oct 1996 01:40:11 GMT
George H. Thiel wrote:
>
> In article <01bbad19$a48b4980$279615a5@Singnet.singnet.com.sg>, "DR. JOHN CHEUNG" writes:
> |> I am having heated debate with a colleague in my university's mechanical
> |> engineering department. In planning a new Elective subject relating to
> |> advanced aspects of buckling, plastic collapse, as well as plates, shells,
> |> etc. I give the subject the established name of Advanced Mechanics of
> |> Materials.
> |> He strongly object to this title. It should be called something like
> |> mechanics of structures, or structural mechanics. Struts, beams, plates,
> |> shells are structures, he said. Mechanics of materials is to do with
> |> elasticity, plasticity, fracture, creep, etc. They concern study of the
> |> mechanics of solid materials.
> |> No, struts and beams are load bearing component, I said. They may be
> |> structural components, but may also be machine components subjected to
> |> loads. And structural elements are components of structures and are not
> |> structures, like gears and bearings are components of machinery and are not
> |> machinery. The name mechanics of materials may be misleading in terms of
> |> language use, but it is the acceptable term for such study of beams and
> |> struts in the English speaking mechanical engineering community.
> |> The arguement is still going on, as my colleague does not give up easily.
> |> And I am exasperated.
> |>
>
> Why not call the course "Advanced Mechanics of Materials and Structures" ? You will probably
> include elements from both "subjects"
>
> Finally a qusetion on this forum I could answer :)
>
> George
> (thiel@vnet.ibm.com)
The problem I'd have with "Mechanics of Materials" is that I'd have
presumed that it'd be a course in devising designer materials at the
atomic or molecular level - unique metal alloys or copolymers to Your
Specifications While You Wait!
Subject: Re: Your Most Often Used References
From: Ben Sauvin
Date: Wed, 2 Oct 1996 01:55:49 GMT
Jim Papadopoulos wrote:
>
> Steve Offiler writes:
>
> >
> >
> >>An impromptu survey for the masses:
> >
> >>What are your favorite references?
> >
>
> McMaster-Carr catalog
Agree with McMaster-Carr catalog, although this is my true background showing.
I'm currently employed as a "mechanical designer", and was for a time officially a "systems engineer",
which is really a fancy way of saying that I came to understand manufacturing, manufacturing processes,
machine design and fabrication quite literally from the ground up and without benefit of formal schooling
while suffering from an addiction to programming languages while not punched in.
As such, I'm often galled at how REAL enigneers re-invent wheels, gears, clamps and suchlike, spending days
or even weeks drawing and detailing something that will be VERY expensive and with absolutely monstrous lead
times when a single afternoon spent just thumbing through a McMaster-Carr catalog or something similar, EVEN
IF it's just to shop for an IDEA, can often result in something being built not by the end of the quarter, or
the end of the month, but by the end of TOMORROW and costing something not much more than a couple of days'
lunch money.
Taking an "off the shelf" approach to mechanical design can do WONDERS for keeping the beancounters off our
backs about projects deadlines.
Subject: Air Compressor Sizing
From: David Richards
Date: 2 Oct 1996 04:11:41 GMT
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I saw your posting on sci.engr.mech on air compressors. I work at a natural gas
tranmission company that might have a similar air load as you. (Just so you know, I
have no interest in any manufacturers.) Couple of questions for you:
1. What is the pressure you are operating at?
2. What kinds of steady and reduced flow rates are you talking about? How long does
each flow rate occur for?
3. What are your ambient conditions?
If these are in the following ranges:
1. about 1035 kPag
2. 40% to 100% of rated flow. Rated flows depends on the size of the air
compressor.
3. 85 to 101 kPaa and -30 to 30C
then you might consider a screw-type air compressor. We use 2 or more screw air
compressors in parallel (with a lead/lag panel controlling them to equalize unit
hours) to provide a wider range of flow. I can give you a schematic if you want.
Using standard controls, they will operate on their own starting and stopping using
the setpoints on the lead/lag panel. To ensure that dry air is provided, we put a
dehydrator (dessicant bed) sized for a maximum dewpoint of -40C (mostly operates
around -60C).
Some of the air compressor (a/c) manufacturers will have a butterfly valve which
will throttle the a/c to run between 40% and 100% of full load to allow the starter
some resting time. (The butterfly valve works by artificially lowering the suction
pressure to reduce the actual capacity of the air compressors' screw.)
E-mail me if you want more details.
Cheers!!
David Richards
djrichar@cadvision.com
Calgary, Alberta, CANADA
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I am currently looking into replacing the two compressors houses at my company
with one central site, complete with a new reticulation ring main distributing
to the three separate factory areas. As a requirement for the majority of the
processes is dry, oil free-air, I have considered centrifugal compressors.
However they do not handle load fluctuations very well, being more suited to
continuous flow operation. I am therefore considering (as one of my options)
centrifugals to handle the base load, and screws to handle any increases in
flow above this base load, due to their better unloading characteristics.
If anyone has any experience in this type of arrangement, or has any other
suggestions, your comments would be greatly appreciated.
Regards
Mike Clapperton
---------------------------------467959003684--
Subject: Re: Combustion efficiency based on ambient temperatures?
From: tomlinsc@ix.netcom.com (Chuck Tomlinson)
Date: 2 Oct 1996 06:01:45 GMT
On 1 Oct 1996 20:53:10 GMT, Matt Kennel wrote...
>
>P Barnes (pbarnes@iserv.net) wrote:
>
>: >Your higher fuel consumption in winter is not necessarily caused by lower
>: >engine efficiency but by higher aerodynamic drag on the car. If the air is
>: >say 30 degrees C colder in the winter it will be about 10% denser. This means
>: >10% higher drag that must be compensated by higher power output from
>: >the engine.
>
>Maaybe, but I doubt this is usually significant.
I disagree. IMHO, 10% is pretty significant, especially at highway cruise.
>: Ok so if the air is denser, then more O2 in the intake, so engine is
>: slightly more efficient. I don't know by how much, but shouldn't this
>: offset the "higher drag?"
>
>More oxygen means it will have more power but not necessarily be more
>efficient.
If anything the engine will be *less* efficient at low ambient temps because of
smaller throttle openings (and higher throttling losses) to produce the same
power.
>: One factor in lower fuel mileage in winter is the fact that the engine
>: is run richer during warm up. Especially if short trip driving occurs
>: often.
Agreed.
>And that with a colder engine block temperature, you lose more energy from
>the fuel combustion to heating up the cylinder walls (heat which is lost)
>instead of causing a higher in-cylinder gas pressure which turns into
>mechanical work.
But the cylinder walls are at the same temp regardless of the ambient temp
(remember the thermostat?). Unless the thermostat is *completely* closed
(ultra-low ambient temps), the coolant temp will be independent of ambient temp.
>In reality, cold weather is often bad weather, and there are more traffic
>jams, and there is less traction on the ground thanks to snow and ice.
Perhaps, but I've observed increased fuel consumption in winter, even over long
distances at steady speeds. My car has a pretty accurate instant/average fuel
economy digital readout, so I'm not really guessing here.
--
__
___| |____ Chuck Tomlinson
/___LT-1___/ Mouse Power!
|__| '94 Vette Z07/ZF6, '89 Mustang LX5.0L/T5
Subject: Re: Combustion efficiency based on ambient temperatures?
From: tomlinsc@ix.netcom.com (Chuck Tomlinson)
Date: 2 Oct 1996 06:01:45 GMT
On 1 Oct 1996 20:53:10 GMT, Matt Kennel wrote...
>
>P Barnes (pbarnes@iserv.net) wrote:
>
>: >Your higher fuel consumption in winter is not necessarily caused by lower
>: >engine efficiency but by higher aerodynamic drag on the car. If the air is
>: >say 30 degrees C colder in the winter it will be about 10% denser. This means
>: >10% higher drag that must be compensated by higher power output from
>: >the engine.
>
>Maaybe, but I doubt this is usually significant.
I disagree. IMHO, 10% is pretty significant, especially at highway cruise.
>: Ok so if the air is denser, then more O2 in the intake, so engine is
>: slightly more efficient. I don't know by how much, but shouldn't this
>: offset the "higher drag?"
>
>More oxygen means it will have more power but not necessarily be more
>efficient.
If anything the engine will be *less* efficient at low ambient temps because of
smaller throttle openings (and higher throttling losses) to produce the same
power.
>: One factor in lower fuel mileage in winter is the fact that the engine
>: is run richer during warm up. Especially if short trip driving occurs
>: often.
Agreed.
>And that with a colder engine block temperature, you lose more energy from
>the fuel combustion to heating up the cylinder walls (heat which is lost)
>instead of causing a higher in-cylinder gas pressure which turns into
>mechanical work.
But the cylinder walls are at the same temp regardless of the ambient temp
(remember the thermostat?). Unless the thermostat is *completely* closed
(ultra-low ambient temps), the coolant temp will be independent of ambient temp.
>In reality, cold weather is often bad weather, and there are more traffic
>jams, and there is less traction on the ground thanks to snow and ice.
Perhaps, but I've observed increased fuel consumption in winter, even over long
distances at steady speeds. My car has a pretty accurate instant/average fuel
economy digital readout, so I'm not really guessing here.
--
__
___| |____ Chuck Tomlinson
/___LT-1___/ Mouse Power!
|__| '94 Vette Z07/ZF6, '89 Mustang LX5.0L/T5
Subject: CFP: Robotics & Manufacturing
From: warwodad@cuug.ab.ca (Dennis Warwodad)
Date: 2 Oct 1996 15:42:54 -0600
CALL FOR PAPERS
Fifth IASTED International Conference
ROBOTICS AND MANUFACTURING
May 28-31, 1997
Cancun, Mexico
SPONSOR: The International Association of Science and Technology
for Development - IASTED
LOCATION: Cancun, Mexico
SCOPE: Topics to be covered include:
* Adaptive Control
* AI Techniques
* Architectures
* Autonomous Systems
* Bionics/Biomechanics
* Design Automation
* Expert Systems
* Flexible Manufacturing Systems
* Fuzzy Control
* Human/Machine Interface
* Industrial Automation
* Industrial Robots
* Intelligent/Self-organizing Systems
* Knowledge-Based Systems
* Learning/Reasoning Systems
* Manufacturing Systems
* Mechatronics
* Microrobotics
* Mobile Robots
* Modelling
* Motion Planning
* Multirobot Systems
* Neural Networks
* Process Control
* Reliability/Safety/Stability
* Robot Dynamics
* Robot Control
* Robot Kinematics
* Robot Mechanisms
* Robot Safety
* Robust Control
* Scheduling
* Sensors
* Sensor Data Fusion
* Simulation
* Space Robotics
* Teleoperation
* Virtual Reality
* Applications - all areas
GENERAL CHAIR: T.C. Hsia, University of California, Davis, USA
PROGRAM CHAIR: Rene V. Mayorga, University of Waterloo, Canada
INTERNATIONAL PROGRAM COMMITTEE
S. Arimoto - University of Tokyo, Japan
M. Asada - Osaka University, Japan
A. Avello - Univ. de Navarra, Spain
M.M. Bayoumi - Queen's University, Canada
Z. Bien - KAIST, Korea
G. Casalino - DIST-Universita di Genova, Italy
A. Casals - U. Politecnica de Catalunya, Spain
R. Colbaugh - New Mexico State Univ., USA
P. Dario - ARTS, Scuola Superiore S. Anna, Italy
C. de Silva - Univ. of British Columbia, Canada
A.P. del Pobil - Jaume-I University, Spain
A. Desrochers - Rensselaer Polytechnic Inst., USA
C. Doumanidis - Tufts University, USA
S. Elgazzar - National Research Council, Canada
T. Fukuda - University of Nagoya, Japan
A. Goldenberg - University of Toronto, Canada
W.A. Gruver - Simon Fraser University, Canada
J.M. Ibarra - CINVESTAV, Mexico
S. Kalaycioglu - Canadian Space Agency, Canada
V. Karri - University of Tasmania-Hobart, Australia
R. Kelly - CICESE, Mexico
O. Khatib - Stanford University, USA
P. Khosla - Carnegie Mellon University, USA
J.-H. Kim - KAIST, Korea
H. Koivo - Helsinki University of Technology, Finland
K. Kosuge - Tohoku University, Japan
S.H. Lee - JPL, USA
F. Lobo-Pereira - ISR-Porto, Portugal
R. Luo - North Carolina State University, USA
L. Luong - University of South Australia, Australia
A.A. Maciejewski - Purdue University, USA
H. Miura - University of Tokyo, Japan
Y. Nakamura - University of Tokyo, Japan
C.C. Nguyen - Catholic University of America, USA
D. Romero - UNAM, Mexico
A.C. Sanderson - Rensselaer Polytechnic Inst., USA
H. Seraji - JPL, USA
Y. Shirai - Osaka University, Korea
B. Siciliano - Universita di Napoli, Italy
J.J.E. Slotine - MIT, USA
K. Tanie - AIST-MITI, Japan
P.M. Taylor - University of Hull, U.K.
S. Tsuji - Wakayama University, Japan
M. Vidyasagar - CAIR, India
A.K.C. Wong - University of Waterloo, Canada
T. Yoshikawa - Kyoto University, Japan
J. Zurada - University of Louisville, USA
REGIONAL CHAIRS - Mexico
A. Pamanes - Tec. de la Laguna
F. Ramos - ITESM, Morelos Campus
REGIONAL PROGRAM COMMITTEE - Mexico
F. Betancourt - Tec. de la Laguna
J. Frausto - ITESM, Morelos Campus
J. Flores - Tec. de la Laguna
J.L. Gonzalez - ITESM, Monterrey Campus
A. Molina - ITESM, Monterrey Campus
J. Negrete - Univ. de Veracruz
V. Parra - CINVESTAV
L.A. Pineda - I.I.E., Cuernavaca
A. Ramirez - CINVESTAV
G. Rodriguez - I.I.E., Cuernavaca
M. Sanchez - ITESM, Monterrey Campus
V. Santibanez - Tec. de la Laguna
R. Soto - ITESM, Monterrey Campus
E. Sucar - ITESM, Morelos Campus
SUBMISSION OF PAPERS
Three copies of the papers (maximum 12 double-spaced pages,
including figures, for regular papers; and maximum six double
spaced pages for short papers) should be received by the IASTED
Secretariat by November 25, 1996. Please provide four keywords
to indicate the area of the paper. Also, include a statement in
your cover letter confirming that if the paper is accepted, one
of the authors will attend the conference to present it. Please
give the full name, affiliation, full address, telephone and fax
numbers, and email address if available.
Notification of acceptance and author kits will be mailed by
February 3, 1997. The final manuscripts and registration payment
are due prior to March 15, 1997. Registration fees not received
by that date may result in the paper being excluded from the
proceedings.
IMPORTANT DATES
Manuscripts Due November 25, 1996
Notification of Acceptance February 3, 1997
Final Manuscripts and Payment March 15, 1997
MANUSCRIPTS MUST BE SENT TO:
IASTED Secretariat - RM'97
#80, 4500 - 16 Ave. N.W.
Calgary, AB
Canada T3B 0M6
Tel: 403-288-1195
Fax: 403-247-6851
Email: iasted@cadvision.com
URL: http://www.cuug.ab.ca:8001/~warwodad/iasted.html
Subject: PIVCO Joins National Station Car Association
From: stncar@ix.netcom.com(Marty Bernard)
Date: 2 Oct 1996 21:09:41 GMT
PIVCO Joins National Station Car Association
October 2, 1996, Oakland, California, U.S.A
PIVCO, the Norwegian maker of CITI (labeled CityBee in the European
market) confirms its commitment to the US market for electric vehicles
and joins the National Station Car Association (NSCA).
The CITI represents a new concept of transportation in the urban areas,
combining energy efficiency, high level of safety, environmental
friendliness and low cost.
PIVCO has been active in the US for nearly two years, and has currently
40 electric vehicles delivered to the San Francisco Bay Area Station
Car Demonstration introduced by the Bay Area Rapid Transit District
(BART).
The station car concept calls for making small electric vehicles
available at transit stations for riders who can then use them to drive
to home, to work, to shop, and to run other errands during the day,
evening, or week
end. Eventually the definition of station will be expanded to include
all points requiring regular high access, like hotels, parks and the
like.
Rolf Gulbransen, PIVCO's President said, "By joining the National
Station Car Association, we will be working hand in hand with the
innovative experts developing a market that we see as a very important
introductory marke
t for our electric car, the CITI. Members of the Association are as
committed to improving urban environments as we are. In October 45 of
our cars will be operating as station cars in the U.S. This is probably
the largest
electric vehicle application in the world."
"As we build the team to implement station cars on a large scale, it is
important to include electric car makers. PIVCO has been very
supportive of the station car concept and we are pleased we will be
working even closer
with them in the coming months," stated Victoria Nerenberg, President
of the Association and Manager of Technology Advances for BART.
"PIVCO is committed to producing a world class electric urban car that
will attract an international market for station cars, corporate fleets
and for personal applications," said Gulbrandsen.
Station car demonstrations are being developed for dozens of stations
and transit districts around the world.
The National Station Car Association is a national, non-profit
corporation with the purpose of guiding the development, testing, and
commercialization of the station car concept.
To learn more about PIVCO visit http://home.sol.no/pivco/. To learn
more about the National Station Car Association visit
http://www.stncar.com.
--
Martin J. Bernard III, Ph.D.
Executive Director
National Station Car Association
Oakland, California
******************************************************************
* Station cars will become mobility systems including *
* battery-powered cars for access to mass transit stations. *
* For information about the station car concept please visit the *
* National Station Car Association's Info Pages at *
* http://www.stncar.com *
* If you want to learn about the French *
* concept of station cars, visit *
* http://www-rocq.inria.fr/praxitele *
************************Making EVs Current************************
Subject: Re: Mechanical Shock Help
From: hobdbcgv@aol.com (Hobdbcgv)
Date: 3 Oct 1996 00:47:49 -0400
MTS systems in Minneapolis had a pocket rule for such calculations. I
don't know if they still do.
In background, shock and vibration and force describe the three main
areas of failure mechanism in material. One is delivered at a frequency
higher than the natural frequency (static and dynamic force), one at or
near the naturaly frequency (vibration as force), and the third at a rate
lower than the natural frequency (shock as energy density, loosely
referred to as "localized force" ) of the object/system.
I think your question is what happens when you drop it? Having worked
in the shock and vibration area for a good many years, when faced with
that question for one kind of product/object, unless we are building a
test machine, we drop a few and fix what breaks.
The reason is--
1. You need to calculate the dynamic force of each component based on
its mass, how it is attached, and on the gross deceleration of the total
object, which is a function of how and where the item lands and what
deformation occurs to change the deceleration, which can be a large
variable.
2. Once the static part of the problem is solved by determining the
deceleration dynamic of the masses in 1., then you need to find the shock
component by calculating energy transfer and energy dissipation in each
component along the chain of components, which means you need to know the
energy capaciity of each material to find if there it will be a fail from
this phenomenon. Not many capacities are readily available, and so
further complex testing may be required.
3. Then you need to find the natural frequency of each item and compare
it to the
initial impact and deceleration with its damping and compare frequencies
to find any sympathetic pairs or multiples, and sometimes harmonics.
That esoteric work why we engineers who can figure it out just drop a
few items.
It's quicker.
There were shakers that we used with Fourier analysis capabilty, but they
were weak in the shock area. However, not a lot of shock failure occurs
unless you have a very, very rigid case.
MTS used to test product. I don't know if they still do.
PS: When I built test machines for shock and vibration, I did calculate
the natural frequency of every nut, bolt, washer, beam, column, and
protrubence, and checked the shock capacity of most major items.
.
If you still want to calculate it all out because you have an unlimited
budget, let me know.
Subject: Re: Is Mechanics of Mat-not nice!
From: hobdbcgv@aol.com (Hobdbcgv)
Date: 3 Oct 1996 01:28:49 -0400
Do I detect a tone of pontification in Bill, who apparently does not
understand Aristotilean logic and Tony, considers the dozen educated
engineers and professors who assisted in this question as incapable of
cogent thought, and considers creep not, and I quote his words,
"geometrically reactive to applied loads"?
Am I mistaken here, or did not creep used to be the changing of
[geometric] dimensions in reaction to an applied load? Tsk, Tsk.
I would think a bit of respect would better serve Virginia Tech than
ridicule of a colleague. You see, if you were a PE in this state and you
ridicule a colleague, we are to bring you before the board on charges of
ethics violation, and if we do not, we can be brought up on charges of
ignoring a violation. It's written into our state law. You do not appear
to be a PE as it was not listed. So we can forgive you your
unprofessional gaffe.
yours, humbly as ever,
President, ====
Professor Emeritus, -----------
Chair, -------
PE
CSP
BME,BEE,ME, PHD
Eagle Scout
and other titles on committees whose chairmanships are such hot potatoes
that no one in his or her right mind would take.
For those of you who may be impressed by my list ---FORGET IT. It takes a
long time to get these, too damn long not to be a little wary of decisions
made by someone that old. Trust the man's output and examine his thoughts
in the context of your problem, not by his titles. God knows I might run
my wheelchair over your bridge, and you trusted my title over experience,
and I die before my impotence prescription runs out and I wasted good
money.