Hi all ... I did a simple one element elastic simulation of VUMAT and everything
(force balance) is fine.My aim is to change
young's modulus during runtime using strain rate data. So i want to
write VUMAT for the elastic model only and plastic model
(Drucker-Prager) and damage models i want to use the inbuilt one. But
when i tried to run *drucker prager along with my VUMAT i got the
following error.
The option *user material,type=mechanical completely
defines the material behavior. It can not be used with an option that
defines part of a material`s behavior
*drucker prager requires the use of *elastic, *porous elastic, or the combination of *eos and *eos shear, type=elastic options

Hi all ... Am trying to run a model with VUSDFLD+vgetvrm to get
strain components from the odb. But am getting an error "ERROR in job
messaging system: Error in connection to analysis". If someone can point out a
possible reason for this error, that may help me to resolve the issue.
Also if anybody is interested  in looking the problem more closely , I
am open to sending the source files. thank you.

Priya

Hi all

      What is the difference between plastic deformation and Elasto-plastic deformation? Thank you all.

Dear all,

          I did a three point bending test on a brittle rod. I observed an oblique fracture (slant approx 45 degrees). It can be an easy conclusion that this 45 deg crack is due to shear failure. But i have the following questions

1. Can a shear band  occur in  bending mode? as in literature very frequently shear bands are reported in pure tension and compression.

2. What is the state of hydrostatic stress or the principal stresses along line of shear band (whether the hydrostatic or principal stresses increase or decrease with bending)? as it is well known that even in max shear state there exists normal stresses.

Dear all,

           I did a 3 pt bending impact simulation with an elasto plastic model. But the slope of contact force vs time curve is too steep at the beginning of the impact. One trivial way of reducing the slope is by reducing the young's modulus of elements in the vicinity of contact or the impactor. Also reducing the mass of the impactor and the impact velocity did not help in reducing the slope.

Is there any other non-trivial parameters that controls the slope of contact force vs time plot? Thanks ina dvance.

Hello all,

            How to find sum of all nodal forces along a plane in abaqus. Thanks in advance.

Hi all,

     My first question is i have a set of stress Vs strain data for different strain rates (100/s to 350/s). Can prony series be extracted using these data? Or is there a way in Abaqus i can enter directly this data?

    After reading for a while a came to know that stress relaxation data is needed for defining pony series. My second question is can stress relaxation data can be obtained for high strain rates in the order of 100 to 350/s?

Thanks all 

Hi all,

         How to model a pipe which has pores in its internal surface, when the pipe is filled with water and closed at the both ends. Now when the pipe is impacted in the 3 point bending mode water will enter in side the pores and will cause some damping (resist bending).

        Is there a modeling technique in Abaqus to do this type of analysis? We need to have the pores modeled as well as water entering inside the pores, however i want to do the simulation in the macro level (i want to simulate the full pipe). Thanks in advance.   

Hi all ... can somebody suggest me good book(s) on plate/beam theroy? The book should start for a novice and should go till large deformation part. Step by step explanation atleast for first few chapters should be there. Thank you.

Hi all ... i have been doing element deletion extensively in my analysis but was wondering ... wat are the Pros and Cons of using this method. To my knowledge was wondering how the deleted mass and energy are conserved through out the analysis. Thank you all.

Hi all,        I want to capture strain-rate behaviour of materials but unfortunately abaqus does not have Cowper-Symonds which is a widely used (simple) model. However johnson-cook is to complicate for me as not much details are available in literature as i am modeling bio-materials. Is there any good substitute for Cowper-Symonds models in abaqus. Thanks.

Hi all ... Is there a way to find/calibrate material parameters for johnson and cook material model using experimental data in Abaqus? .. As far as i know abaqus has something called as data editor with which Hyperelastic materials models can be calibrated with experimental results. If not is there any other way arround to do calibration of material parameter with abaqus.

Hi ... what is the difference in functionality between charpy (a simply supported specimen(notched/unnotched) is hit by a swinging pendulum)and gardner test (a simply supported specimen(notched/unnotched) is hit by a vertical free falling mass guided by rails) .... 

1.What is the loading pattern in the point of contact between the specimen and the setup?

2.Why fracture pattern varies between the two test setups for similar specimen with same impact velocity, Which parameter is responsible for the variation in fracture type.  

Hi all,

Hi all,

  I have few questions here :  

1.From my reading i  can understand there is a long debate going on stating Hydrostatic Stress (HS) have/have not influence over yielding and failure of materials. Some people say when only HS is applied the material become 'incompressible' and the HS donot influence yielding. Some people say when the material is porous the HS load do have influence in yielding as there is room for deformation when the pores collapses. To add more confusion some say even the material is not porous HS have influence over yielding. Someone please throw some light on these arguments and which one is true?

Hi all,

       Can Hydrostatic stress be used as a fracture criteria? If so can critical hydrostatic stress be found experimentally? Thanks.

Hi all,

Hi all .. What are the advantages of XFEM over std FEM other than remeshing ? 

Because when ever  XFEM is introduced only remeshing alone is highlighted ... Can the experts from this field please list out the other advantages?

 
All above are in context to Fracture.

thanks in advance. 

How to import what i beleive is Ls-Dyna files with an extension (.k) in to Abaqus CAE 6,7 edu version?? . Any free translaters are available or can it be done with Abaqus itself ??

 Thx in advance

mike 

Dear all,

         I am new to X-FEM, started reading papers a couple of weeks before. I understood, functions[heaviside,sign..] are used to enrich the nodes to simulate virtually the discontinuity and asymptotic functions are used to charecterize the crack tip,other than this regular FEM nodes are there. I have few questions. 

1.what is the role of the asymptotic functions and its unknown co-efficient 'b' in charecterizing the crack tip. What are the parameters do these functions exactly charecterize means wat are the details can we extract from these fns n co-effs?

what is the Difference b/w ref pt and datum pt in ABACUS??