Re: How to get DDSDDE for strain softening material or damage elastic material?
"shayan seg
[email protected] [Abaqus]" <
[email protected]>
Fri, 25 Oct 2019 02:07:21 +0000 (UTC)
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Hi,=C2=A0
In the past, I implemented a similar elastic model with a damage =
model without plasticity. That UMAT code worked quite well even after softe=
ning. However, in that study, all the softened elements had some minor elas=
ticity, even if they were completely damaged and the time increments were v=
ery small.
For your model, I do not have all the information about your cod=
e, and therefore, I cannot go into details. But as you mentioned that your =
model did not experience any divergence before the peak stress, I assume th=
at your DDSDDE is accurate (it is only an assumption meaning that your code=
and DDSDDE could also be inaccurate). So maybe the divergence arose either=
from the low local elasticity of your model or from the high localization =
effect.
One remedy, as you did, is the artificial viscosity. However, if st=
ill, the localization exists considerably, as you mentioned, you ought to s=
olve it, considering that it could also affect your results. A nearly ideal=
method to address this localization issue is based on averaging the integr=
ation point data locally. Accordingly, you need to get the data from each i=
ntegration point through the URDFIL subroutine. Then, you should average yo=
ur strain or stress parameters based on the neighboring integration points =
depending on their distance. Subsequently, the new STRESS/STRAIN arrays sho=
uld be transferred to the UMAT subroutine so that you can use their values =
instead of the default values in the UMAT. This approach might help if othe=
r parts of your model and code, including the DDSDDE, were correct. For mor=
e details, refer to section 2.2 of the following article:
Quiroga, JM P=C3=
=A1rraga, et al. "The effect of loading rate on the development of early da=
mage in articular cartilage."=C2=A0Biomechanics and modeling in mechanobiol=
ogy=C2=A016.1 (2017): 263-273.
Sincerely,Seyed Shayan SajjadiniaPh.D. Stud=
ent at Unibz
Sent from Yahoo Mail on Android
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<p>Hi, <div id=3D"yMail_cursorElementTracker_1571963924723"><br>=
</div><div id=3D"yMail_cursorElementTracker_1571963984734">In the past, I i=
mplemented a similar elastic model with a damage model without plasticity. =
That UMAT code worked quite well even after softening. However, in that stu=
dy, all the softened elements had some minor elasticity, even if they were =
completely damaged and the time increments were very small.</div><div id=3D=
"yMail_cursorElementTracker_1571964450246"><br></div><div id=3D"yMail_curso=
rElementTracker_1571964450485">For your model, I do not have all the inform=
ation about your code, and therefore, I cannot go into details. But as you =
mentioned that your model did not experience any divergence before the peak=
stress, I assume that your DDSDDE is accurate (it is only an assumption me=
aning that your code and DDSDDE could also be inaccurate). So maybe the div=
ergence arose either from the low local elasticity of your model or from th=
e high localization effect.</div><div id=3D"yMail_cursorElementTracker_1571=
965261446"><br></div><div id=3D"yMail_cursorElementTracker_1571965261891">O=
ne remedy, as you did, is the artificial viscosity. However, if still, the =
localization exists considerably, as you mentioned, you ought to solve it, =
considering that it could also affect your results. A nearly ideal method t=
o address this localization issue is based on averaging the integration poi=
nt data locally. Accordingly, you need to get the data from each integratio=
n point through the URDFIL subroutine. Then, you should average your strain=
or stress parameters based on the neighboring integration points depending=
on their distance. Subsequently, the new STRESS/STRAIN arrays should be tr=
ansferred to the UMAT subroutine so that you can use their values instead o=
f the default values in the UMAT. This approach might help if other parts o=
f your model and code, including the DDSDDE, were correct. For more details=
, refer to section 2.2 of the following article:</div><div id=3D"yMail_curs=
orElementTracker_1571966891339"><br></div><div id=3D"yMail_cursorElementTra=
cker_1571966891533"><span style=3D"color: rgb(34, 34, 34);font-family: Aria=
l, sans-serif;font-size: 13px;background-color: rgb(255, 255, 255);">Quirog=
a, JM P=C3=A1rraga, et al. "The effect of loading rate on the development o=
f early damage in articular cartilage." </span><i style=3D"color: rgb(=
34, 34, 34);font-family: Arial, sans-serif;font-size: 13px;background-color=
: rgb(255, 255, 255);">Biomechanics and modeling in mechanobiology</i><span=
style=3D"color: rgb(34, 34, 34);font-family: Arial, sans-serif;font-size: =
13px;background-color: rgb(255, 255, 255);" id=3D"yMail_cursorElementTracke=
r_1571969021020"> 16.1 (2017): 263-273.</span><br></div><div id=3D"yMa=
il_cursorElementTracker_1571963984913"><br></div><div id=3D"yMail_cursorEle=
mentTracker_1571965947792">Sincerely,</div><div id=3D"yMail_cursorElementTr=
acker_1571963924894">Seyed Shayan Sajjadinia</div><div id=3D"yMail_cursorEl=
ementTracker_1571963935422">Ph.D. Student at Unibz</div><div id=3D"yMail_cu=
rsorElementTracker_1571963961665"><br><div id=3D"ymail_android_signature"><=
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