Yield Strength

Dear Sir/Madam

While thanking for your reply ,I'm from Iran where you most probably know it,we have many refinery,wells,oil and gas petrochemicals and ....

as you stated above, yield and and tensile indicate the mechanical properties and both shows the material behavior in different temp,pressure,i know ,but the question is for instance we have pipe ASTM A106 Gr B with tensile (60,000 psi) and yield strength (35,000 Psi),but in all calculation for selection the thickness,pressure calculation and ... just considering the yield strength as the figure for selection and nothing said about tensile and totally yield strength consider for pipe.

thank you guy.

hello sha while i am not well versed in the pipeing disciplines etc, - i know that whatever something starts out as - this will not remain the same as time progresses and the system will change and therefore the input compared to the output will shift and change. these are what you have do address thruout the lifetime of the article. regards -

dear rabbit16

sorry but i don't understand your intention.

my intension is to open a path of cummnicacation around which we can continue to converse most of my knowledge is based on direct experience throughout lifes pages.

i well come to you.leave your e-mail to enable me to have correspondence .

my email is rabbit16@telus.net i am 58 years old and have built original objects for people for most of my life - wood - metal - plastics - cements these days i am preparing to start making guitars again as i have done this in the early seventies and now feel it is time to get back into this. hope you are well glc

well i agree with you principal and thank your consideration. some ideas are in jest yet can contain a seed of reality within. the constraints that maintain a "system" to be in proper operation sooner or later alter enough to become no good. its a fact. regards rabbit

Force applied to a material can be of compression or tension or shear. All materials give with force; too much they break. Fore per area is stress. Tension affects the ductile materials. Below elastic limit material stretches in proportion to stress. Beyond elastic limit stress gives permanent set. At yield point material begins to flow with no increase in unit stress. After that ultimate strength followed by breaking point. We need to design any parts within the safe limit of working forces.

Both the yield strength F_y and the ultimate tensile strength F_u (I'm not sure F_u is the standard notation) are important. Various construction codes consider either or both of these.

To determine allowable stress S, some structural codes use a safety factor of 1.67 based on F_y (i.e., S = F_y/1.67). At least some of the ASME pressure vessel code is based on F_u with safety factor 4.0 (S = F_u/4.0). I think some piping codes use a safety factor of 5.0, but higher safety factors can be specified either in codes or in contract requirements. (Buyers can ask for whatever they want, so long at is ≥ the local code requirement.)

The yield strength or yield point of a material is defined in engineering and materials science as the stress at which a material begins to deform plastically. Prior to the yield point the material will deform elastically and will return to its original shape when the applied stress is removed. Once the yield point is passed some fraction of the deformation will be permanent and non-reversible. Look at the diagram of stress testing at http://en.wikipedia.org/wiki/File:Stress_v_strain_Aluminum_2.png . Ultimate tensile strength (UTS), often shortened to tensile strength (TS) or ultimate strength, is the maximum stress that a material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract. Brittle materials, such as concrete and carbon fiber, are characterized by failure at small strains. They often fail while still behaving in a linear elastic manner, and thus do not have a defined yield point. Many materials display linear elastic behavior, defined by a linear stress-strain relationship in which deformations are completely recoverable upon removal of the load; that is, a specimen loaded elastically in tension will elongate, but will return to its original shape and size when unloaded. Beyond this linear region, for ductile materials, such as steel, deformations are plastic. A plastically deformed specimen will not return to its original size and shape when unloaded. After the yield point, ductile metals will undergo a period of strain hardening, in which the stress increases again with increasing strain, and they begin to neck, as the cross-sectional area of the specimen decreases due to plastic flow. In a sufficiently ductile material, when necking becomes substantial, it causes a reversal of the engineering stress-strain curve; this is because the engineering stress is calculated assuming the original cross-sectional area before necking. The reversal point is the maximum stress on the engineering stress-strain curve, and the engineering stress coordinate of this point is the tensile ultimate strength. The UTS is not used in the design of ductile static members because design practices dictate the use of the yield stress. It is, however, used to for quality control, because of the ease of testing. It is also used to roughly determine material types for unknown samples.