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Is Elastance equal young modulus?

  1. Mar 25, 2012 #1
    Hi, dear all,

    Recently face some controversial issue with my supervisor and i cannot convince my self too.
    is it time varying elastance equal to time varying young modulus?

    Young modulus unit is Pa, however, elastance value is mmHg/ml, is both of them are equal?

    Young's modulus, also known as the tensile modulus, is a measure of the stiffness of an elastic material and is a quantity used to characterize materials. It is defined as the ratio of the uniaxial stress over the uniaxial strain in the range of stress in which Hooke's Law holds.

    Compliance is calculated using the following equation, where ΔV is the change in volume, and ΔP is the change in pressure:[3]
    http://en.wikipedia.org/wiki/Compliance_(physiology [Broken])

    as in the engineering software like ansys, comsol, adina, we only can set young modulus, so i wondering whether they are the same?
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Mar 27, 2012 #2
    Is there anyone here can give me some hint or tips?
  4. Mar 27, 2012 #3


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    Elastance is not a very common term, so you are going to have to find the place where the term was defined in whatever equipment or paper it arises for you. You can also make a dimensional analysis of the units to see if they are the same, but that will only tell you if they are proportional to each other or not; it will not establish equality.
  5. Mar 27, 2012 #4
    Dear OldEngr63,

    Thank you for your reply.
    The elastance unit is mmHg/ml, and Young modulus is Pa, in this case i understand as you say that they are not equal unit.

    but that means the elastance unit = young modulus/ volume change?

    or it means Elastance is just a description for us to justify how good is a material can deform, while young modulus can be applied quantitatively on the calculation?
  6. Mar 28, 2012 #5
    From the wikipedia article you linked, it appears that "elastance" is the reciprocal of "compliance." "Compliance" is a term that is used in basic solid mechanics - though, in that field, it is referring to the deformation of a material under axial load. In your application, compliance is NOT referring to the deformation of a material under axial load. In your application, compliance is referring specifically to the ability of a vessel to expand. This may be the source of your confusion.

    It's interesting that the wikipedia article you posted uses veins and arteries as examples. I had a similar conversation about the term "compliance" one time with a doctor.
    Colloquially, their definition of "compliance" is similar to ours.

    Higher young's modulus of the artery material will result in a lower compliance, whether we use the physiology definition of compliance or the solid mechanics definition of compliance. Keep in mind, though, that the definitions of compliance are in fact totally different.

    Higher young's modulus will result in a higher elastance, though the relationship is indirect.

    As mentioned by a previous poster, the term "elastance" probably does not exist outside of physiology.
  7. Mar 28, 2012 #6
    Thanks afreiden for your details explanation. I will read more on compliance term now.
  8. Mar 28, 2012 #7


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    Looking at the reference in the OP, "elastance" seems to be similar to the inverse of the bulk modulus of the material (i.e. the change in volume caused by a change in hydrostatic pressure in the fluid), which is a more relevant than Youngs modulus for describing a compressible fluid. http://en.wikipedia.org/wiki/Bulk_modulus

    But I've never seem the term elastance before, and I don't claim to know anything about biomechanics.
  9. Mar 28, 2012 #8
    Hi, AlephZero,

    Thanks for support the thread.
    The elastance is one kind of term which used to describe the capabilities of blood vessel on how much the volume can be result due to large pressure pump in.

    I just curious when is the term come out, as in the traditional solid mechanics book, they only mention about elasticity, maybe this word is discovered in physiology.

    I find a interesting video

    but as engineer, i need to apply this term in biomodelling, so wish to know more.
    Last edited by a moderator: Sep 25, 2014
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