Can anybody tell me how poisson ratio is mathematically related with flexibility calculation. If possible plz give reply with conventional formula.

I think it is not posible!

Mathematics for material sounds unrealistic....

Regards!

Ok can you give me the basic engineering formula relating the poisson ratio and flexibility equation. Because in ASME B31.1 it is mentioned poisson ratio of 0.3 can be considered for fleibility calculation, so i want to know how flexibility equation = E*alpha*L*(T2-T1) and poisson ratio is used in stress analysis.
Where,
alph = Coefficient of thermal expansion (mm/mm deg C)
E = Modulus of elasticity (N/mm^2)
L = length (mm)

Poisson's ratio is not used in the equation to determine the thermal growth of a straight pipe (the equation you referenced above).

Poisson's ratio is a term in some of the equations used in generating the element stiffness matrix. Poisson's ratio relates the elastic modulus of elasticity to the shearing modulus of elasticity. Find any text that discusses the stiffness matrix for 'beam elements' and you'll have all the equations.

Hello Nixon123,

Actually, yours is a "very good question" as it motivates us ALL to think about "the basics" (something most of us are guilty of doing too infrequently). Understanding the fundamentals of beam theory is essential to becoming a competent piping engineer. While (whilst for our Land of Oz colleagues) the understanding of the response of straight beams is important, it leads us to the more complicated study of curved sections of pipe and the inevitable torsional loadings.

You may be interested in reading Dr. Hashem M. Maurad's 1999 thesis as he does a fine job of reviewing the history and theoretical development flexibility analysis before he get to "the meat" of his study. Actually most of us should read it again.

Go here to the University of Michigan archive:

www-personal.umich.edu/~hmourad/PDF/MS_Thesis.pdf

or just go here:

http://www-personal.umich.edu/~hmourad/

and find the thesis under the "The American University in Cairo" heading.

Well, if you want equations, they can be found. Of course poisson's (ratio of strains for a given material and a given stress) is related to the modulus of elasticity and all of that is shown by wikipedia at:

http://en.wikipedia.org/wiki/Poisson%27s_ratio

Regards, John

Ofcourse yes... Poisson's Ratio can be use to calculate flexibility but you need a E or the G to have the limit.
"so i want to know how flexibility equation = E*alpha*L*(T2-T1) and poisson ratio is used in stress analysis."
Flexibility is true, but thermal expansion?

please read this one this will help you understand what poission's ratio are about..
http://silver.neep.wisc.edu/~lakes/PoissonIntro.html

Thanks Sir John for the link.. Me to need this kind of links for my study.

Regards!

Thank you friends for the kind reply
Friends i have another question?
As per ASME B31.1 what is meant by "STRESS RANGE"?
1) Why it should be called as stress range?
2) We all know Thermal Expansion Stress range equation as per ASME B31.1
Sa = f(1.25Sc + 0.25Sh),what is the basis for this equation and how it is
derived from fundametals.
3)Why Sc is multiplied with higher factor as "1.25" and Sh with lower factor as "0.25"?

Basically i need funda behind stress range equation very clearly,because
it is the root of stress analysis without understanding it clearly
it doesn't make sense as good piping engineer, so plz guide me with
good explanation.

Search the forum here. This has been explained several times. The original theory goes back to Spielvogel's work in the 1950's. Basically, the sum of the multipliers is 1.50 because the basic allowable stress for materials is no greater than 2/3 yield. And we deal in stress ranges because piping stress analysis is primarily a prediction of the fatigue life of a piping system.

I'm sure John Breen has a 5000 word essay on this subject tucked away somewhere on this forum. He can explain it much better than I can.

May I recommend you a book.
It’s “Piping Handbook” by Mohinder L. Nayyar, McGraw-Hill Professional; 7th edition ISBN-10: 0070471061
Chapter B4 is "Stress Analysis of Piping Systems" and definitely isn’t my favorite. The reason I recommend you this book is the availability on market; you can buy it from Amazon, for example.

In this book, you can find basics of the stress analysis (I’d like to say no more than "acceptable" basics) as well the main Codes review formulas.
You may find interesting that for restrained lines B31.4 counts the longitudinal compressive stress due to the combined effects of temperature rise and fluid pressure with a formula that include Poisson coefficient while other Codes don’t.
Why? Because B31.4 deals with restrained lines, others no, etc

It’s a lot to learn and you must pay your personal effort. Success!

Regards

Dear nixon123,

It’s not the primary purpose of forums to explain Codes formuls. More common is to give you references. Maybe it’s allowed to make an exception today.

A quite common mistake in today (and yesterday…) engineering is to mix formulas, concepts, ideas, computer results, some knowledge and good intentions. Your question it’s a good example: you mix B31.1, a common value for Poisson coefficient, "flexibility equation =" and a positive determination to learn by melting all in a stress analysis pot.

Probably you are confused by a formula similar to one given by B31.4, paragraph 419.6.4 (b) "Restrained lines". For those lines, the net longitudinal compressive stress is due to the combined effects of temperature rise and fluid pressure (and) shall be computed from the equation: SL=E*alpha*(T2-T1)- nu*SH.
Supposing this is the source of your confusion, please note that "nu" is Poisson ratio and SH is the hoop stress due to fluid pressure.
The formula must be applied only for "totally restrained lines", which means "zero longitudinal strain". Zero longitudinal strain doesn’t mean zero longitudinal stress, despite a naïve and wrong idea of Hook law applied as proportionality everywhere.
This stress status is characteristic to pipeline buried, far away from pig traps.

The term "-nu*SH" is due to pressure. It’s not the place here to explain why the pressure term has this form. Some authors are calling this term Poisson effect ("longitudinal shrinkage due to hoop strain"). Obviously, a shrinkage effect exist; however for me this term is not more than the tension done by pressure in zero longitudinal strain.
In software results , this value of longitudinal stress "naturally" appears when the pipeline model is well done and extended enough to have "zero longitudinal strain".

No connection between the above formula and piping "without substantial axial restrain" under B31.4, B31.3, B31.1, etc Codes. Pay attention to this aspect! Basically, for those lines, the behavior is to transmit the thermal expansion to the adjacent legs, by bending them (for some codes also counting "in a way" the fatigue due to cyclic loads)

With the hope I helped you and excusing I get bored all the rest…
Regards

Dear mariog,

Thank you for clearing my doubt excellently, this doubt came to me once i gone through the book "Mohinder Nayyar", but as you told i missed to notice the difference in codes (ASME B31.1 & ASME B31.4).

Hereafter i will not post these type of questions in forum,excuse me this time.

Dear friends
What is meant by pressure stiffening and how it can be related technically with engineering equations?

more royalist than the king!!!

Dear friend,

In my last 3 major projects I’ve been fighting with Clients (Contractors) that had the strong idea all B31.3 Code engineering is not more (and not less…) than the formula given by para. 304.1.2 "Straight Pipe Under Internal Pressure". Maybe this explains the fight for that formula...
It’s good to have as target to minimize the piping thickness , to be competitive on market… but engineering is not only a formula.
Anyway for my Clients the APPENDIX D and the notes enclosed within, especially note 1, were not more than "pure theory"…. Maybe I was very lucky….

The point is….perhaps you are "the next generation" since you try to discover (or reinvent?) more than one formula linked to the Codes. That’s good! It's a progress!
But finally it’s really good you keep thinking.

Answers for your question:
- to consider this effect in Caesar, search this forum and Caesar docs
- as formula, see Appendix D "Flexibility And Stress Intensification Factors" Note 7
-to see what’s beyond the formula, see "Effect of Internal Pressure on Flexibility and Stress- Intensification Factors of Curved Pipe or Welding Elbows", an article by Rodabaugh and George
- …..and if you like mathematics, study the Appendix I of the article, with an elegant von Karman, Galerkin- Ritz method…

BTW, what’s next in your adventure?
Some Stiffness Matrices techniques by hand?

Regards,

Hello again Nixon123,

Please learn to use the powerful “SEARCH” function that this discussion forum provides. You will find that MANY of the questions that trouble you have been previously discussed here in detail. Judging from your questions you will have to do a lot of studying to “catch up” with the “basic concepts”.

You cannot perform competent piping design and stress analysis unless you completely understand several basic concepts.

You must totally understand the beam theory method of structural analysis. The B31 Codes for Pressure Piping are based upon beam theory methods. For piping flexibility analysis, stresses are calculated as the bending moment divided by the pipe section modulus (the general form is M / Z). If the beam is other than a straight piece of pipe, a stress intensification factor (SIF – using the symbol “i”) is included making the equation for calculating the stress (or stress range) M * i / Z. The stress intensification factors that are appropriate for various piping components came from fatigue testing of various piping components and they can be found in appendices “D” in B31.1 and B31.3. To find the bases for the ASME B31 Pressure Piping Code SIF’s it would be good to read the Markl Papers that are found in the book “Piping Engineering” that was published by Tube Turns Company. The book can be found on the Internet.

As per ASME B31.1 what is meant by "STRESS RANGE"?
1) Why it should be called as stress range?

You must completely understand the difference between primary and secondary stresses and why the piping Codes evaluate these stresses differently. This leads directly to the concept of using “the total range for calculating secondary stress” and the Code allowable stress range. Please understand that in piping structural analysis, the concept of thermal expansion and contraction stresses (secondary stresses) is all about alternating loadings and the effect of fatigue. We consider the piping “as installed” at the ambient installation temperature to be “without expansion stress”. When the piping contracts as the temperature falls from the “ambient installed temperature” (perhaps winter weather and out of service) to the coldest temperature, it will experience bending stresses results throughout the piping system. When the piping expands as the temperature increases from the “ambient installed temperature” to the highest operating temperature, it will experience bending stresses results throughout the piping system. The entire RANGE of stresses from the coldest temperature to the hottest temperature must be considered and compared to the Code allowable stress range. Read this previous discussion:

http://www.coade.com/ubb/Forum1/HTML/000057.html .

And maybe this one:

http://www.coade.com/ubbthreads/ubbthrea...ch=true#Post693

and:

http://www.coade.com/support_discussion.asp

2) We all know Thermal Expansion Stress range equation as per ASME B31.1:
Sa = f(1.25Sc + 0.25Sh),what is the basis for this equation and how it is
derived from fundametals.
3)Why Sc is multiplied with higher factor as "1.25" and Sh with lower factor as "0.25"?

The equation that you cite:

Sa = f * (1.25 * Sc + 0.25 * Sh)

IS NOT the equation for calculating the Thermal Expansion Stress Range. Rather it is the equation for calculating the Code allowable stress range. This equation for the “allowable” provides the stress range that you must compare to the calculated (by Caesar II) stress range as given in paragraph 104.8.3 of B31.1:

SE = i * Mc / Z

Note that the expansion (or displacement) stress range, SE, must be less than (Sa + f * (Sh – Sl))

The expansion (displacement) stress RANGE, SE, that you calculate (and compare to Sa) is the range of stresses from the coldest temperature to the hottest temperature (e.g., consider a piping system that is installed at 70 degrees F - if the coldest temperature is 20 degrees F and the hottest temperature is 500 degrees F, the temperature range to be considered in the SE equation is 480 degrees F (70 to 20 = 50 plus 70 to 500 = 430, therefore the sum (range) is 480 degrees F).

As I mentioned, you can find many of the answers that you seek here at this discussion forum simply by searching the archive of previous discussions, for example:

http://www.coade.com/ubbthreads/ubbthrea...h=true#Post1252

Also, search and find the archive of COADE “Mechanical Engineering” newsletters because our esteemed colleague John Luf and many others (including our COADE board moderators) have written many articles for these newsletters that will help you to understand the “basic concepts”.

There are some good books available that may make your study easier:

Process Piping: The Complete Guide to ASME B31.3. Second Edition. Charles Becht IV. ASME Press

http://catalog.asme.org/books/PrintBook/Process_Piping_Complete_Guide.cfm

The Fourth edition of the CASTI Guidebook to ASME B31.3 - Process Piping
The authors are Glynn Woods and Roy Baguley.

http://www.casti.ca/books_ebooks/B31_3.html

A new book from ASME Press:

Applying the ASME Codes: Plant Piping & Pressure Vessels (Mister Mech Mentor, Vol. 2) by James A. Wingate

http://catalog.asme.org/books/PrintBook/Applying_Codes_Plant_Piping.cfm

And this one:

Piping Systems and Pipelines : ASME Code Simplified (Hardcover)
by Phillip Ellenberger

http://www.amazon.com/Pressure-Vessels-ASME-Code-Simplified/dp/0071436731

Be a good student.

Regards, John

Dear Friends
Thank you for your suggestions, but i need to know whether the questions i am asking is right or wrong, whether i am going in the right path or wrong path, whether my intention to learn about manual calcualtion behind code formulas is right or wrong. My ultimate goal is to become excellent piping engineer with fundas in tip. Just now i finished my one year professional life in piping.
I am considering everybody as guru in this forum,so plz tell your suggestions.

Nixon123,

You wrote:

......i need to know whether the questions i am asking is right or wrong, whether i am going in the right path or wrong path, whether my intention to learn about manual calculation behind code formulas is right or wrong.....

Some people posting above ARE answering your questions. You are also being asked to "do your homework" and READ the material that is being suggested. There is no such thing as a trivial question in the engineering field but when you receive answers from those you ask it is your responsibility to USE the suggestions ("do your homework"). With all due respect, if you have been working in piping engineering for one year and you (at this point) are asking questions about fundamental concepts, you have not learned much about piping engineering in your one year (are your working under a senior engineer?). Now (for the sake of other people's safety) you must study harder - READ THE BOOKS!!!

It took the mentors that post answers here many years of "doing their homework" to become competent piping engineers. There are no "shortcuts"; YOU must also be willing to study the material that is being suggested to you. Read and reread the suggested material and THINK about the concepts. THIS IS YOUR RESPONSIBILITY.

Read this:

http://www.eng-tips.com/viewthread.cfm?qid=189629&page=3

Respectfully, John.

Wow do you mean that a lifetime of study cannot be acquired in 5 minutes on the Internet now thats profound!

John with due respect one can get the work/equations over the internet in 5 minutes but,
not the Judgement/Confidence acquired over the years by masters like you and others in this field!
(Only if the modern science could hack ya brains!!)

Regards,
Siddharth.

This is true enough, often times our modern tools that are used to convey thought and information are mistakenly used for instant gratification purposes. One can only imagine Socrates or Sun Tzu answering posts in forums of today... The questions I am sure would be as "What is the meaning of life etc." in 25 words or less!

LOL have a great Holiday over there... and Go Blues

Dear Friends
Can anybody tell me about the cost range for snubbers for below mentioned details.

PIPE SIZE PIPE MATERIAL LOADS

OD 711 X 12.7 A335 P22 2.5 TONNES
OD 711 X 12.7 A335 P22 4.0 TONNES
OD 711 X 12.7 A335 P22 4.5 TONNES
OD 711 X 12.7 A335 P22 7.5 TONNES
OD 457 X 23.83 A335 P92 4.5 TONNES
OD 457 X 23.83 A335 P92 7.5 TONNES

Sure, your local snubber vendor's rep. Expect a several week delay.

Dear Friends
I query regarding the occasional stress check as per ASME B31.1Rev.2007

1)Whether all the occasional loads such as seismic (both inertia, & seismic anchor movement), safety relief valve, steam hammer, wind, should be clubbed together for occasional stress calculation or occasional loads
should be done separately & check with allowable 'ksh' .
Code tells only wind & seismic need not to be considered together. But regarding other occasional i didn't found any details from code about to be clubbed or not to club all the occasional cases.
Morever code tells that the occasional stress due to seismic anchor movement condition shall be added to thermal expansion stress range equation.

What is you opinion & world wide practice for occasional stress check as per ASME B31.1 Rev.2007.

Note: If i am clubbing all the occasional loads acting on the same time, then the pipe is failing

Nixon123.

PLEASE start a NEW THREAD when you have a NEW question that is not related to the question in the original posting. This is the polite and respectful way when using discussion fora.

CraigB advised you to learn how to use the search facility that is available in this discussion forum because your questions have been addressed in past discussions. Please heed CraigB's advice.

John