## Max principal stresses

## Max principal stresses

(OP)

Hei,

I have two queries. I want to get max value of maximum principal stress at each time point. I want to know that what does this mean? Are these max principal stresses in each node of element and single value is their averages at centroid?

Secondly, I want to get a max value of max principal stress by averaging max principal stress value around this element (from surrounding 4 elements).

I have two queries. I want to get max value of maximum principal stress at each time point. I want to know that what does this mean? Are these max principal stresses in each node of element and single value is their averages at centroid?

Secondly, I want to get a max value of max principal stress by averaging max principal stress value around this element (from surrounding 4 elements).

## RE: Max principal stresses

## RE: Max principal stresses

## RE: Max principal stresses

- "Understanding how results are computed"

- "Understanding result value averaging"

- "Understanding probing"

They explain in detail how Abaqus postprocesses the results before displaying them and how probing tool actually works. For example it is explained that for elemental output Abaqus obtains probe results on an element-by-element basis without averaging.

## RE: Max principal stresses

the data can be element centroid data or it can be nodal (corners, averaged for the different elements).

then you can plot this data as either elemental (centroidal) or nodal (corners) and the s/ware interpolates.

another day in paradise, or is paradise one day closer ?

## RE: Max principal stresses

^{0}formulation (at least for most cases). This means that while the solution variable (displacements in your case) are continuous at the element boundaries (i.e. nodes) -- meaning that there is oneand only onesolution value at each node -- that stress being aderivedvalue (i.e. proportional to derivatives of the solution) is discontinuous (C^{-1}) at the element boundaries -- meaning that each element that shares a node provides its own unique stress value at the node. This is why Abaqus uses a volume-weighted average in its contour plots to make stressappearcontinuous, when in fact it isn't. This is one of the reasons why it is typically recommended to query stresses from quadrature points. As a side note, from theory it's clear to see that derived values will converge at slower rates than solution values - if you would expect displacement to converge at a rate of h^{p+1}then stress would converge at a rate of h^{p}-- so you need a lot more elements to converge to stress than are needed to converge to displacement.Anyways, I've

neverheard of the advice to "average the centroidal stresses of the neighboring elements" because "you can't trust results from a single element". The truth is, for awell-definedFEM-problem youabsolutely cantrust the results from a single element as you can show that the best-approximation property holds for derived values. The caveat to this is contained withinwell-definedas stress-singularities, elements at a boundary-condition, locking, etc. can have issues to be sure. What I typically advise is to look at aquiltplot of stresses and if you see a region that has either oscillatory stresses or a stress thatqualitativelylooks out-of-place compared to its neighbors, to then explore further to see whether you have a singularity, locking, or haven't yet converged to accurate stress results.