Week - 9 Material Modeling from Raw Data

Aim:
For the given true stress and true strain curve extract the data using the data digitizer tool model the MAT_024 linear plastic material and compare the results of extracted true stress and strain values and simulated true stress-strain values.

Procedure:

1.Dogbone specimen consists of nodes and elements .k file is given. And we need to input section and effective plastic stress and strain curve is provided as input to LCID and boundary conditions SPC and prescribed motion to other end is provided. After that to run the simulation as implicit analysis we need to implicit cards from the control cards.  And we request the outputs from the database ASCII,d3plot, and extent binary to record the strain energy. Finally, we control the simulation with help of the termination card.

2. From the challenge either we use 024 or 018 material card so I have used the 024 material card for the material graphite iron as shown below.




in the above card the density,E, and NU value is mentioned and ETAN value is mentioned 0.2% of the E valve. And LCSS carve is provided which is effective strain and stress value, these values are got from true stress and strain values and using effective.

True strain =ln(1+engineering strain)

Effective plastic strain(Input value)=Total true strain-true stree/E (Here true stress/E is used not for the whole term).
Effective stress=true stress.

Engineering strain=e^Truestrain-1
                          =e^0.007-1
                         =7.024E-03

To know the displacement is the change in the length then 
Engineering strain=del l/l

from the above engineering strain =0.007
Length of dogbone specimen=145mm
Displacement is (del l)=0.007*145
                                =1.015

3.once the material is defined and section or property the dogbone specimen is defined:



4.Once material and section is defined need to assign this property to the part and 
5.We need to define the boundary condition:
Here one side of the specimen SPC is applied and other end is prescribed motion is applied and boundary of the curve also specified which is (0,0),(5,145), and (5.1,145) here x-axis is termination time specified and on Y-axis lateral displacement 145 is specified.







In the direction of lateral, we have to free and rest of direction is constrained in the above which is (101111) and (01000) is applied.

6.This is the small deformation problem we can use either by the implicit or explicit analysis ,here I used the implicit card and we need to mention the cards are Control_implicit_general,Control_implicit_auto,Control_implicit_solver cards provided.

Control_implicit_general:

IMFLAG=1 &DT0=0.01

Control_implicit_solver:

Lsolver=2(default) is used.

Control_implicit_Auto:

IAUTO=1(it will adjust the time step automatically).
ITEOPT=11
ITEWIN=5

Control _termination is the Endtime=5.

Post-processing:



                                               Fig: von mises stress contour





The above plots plotted using the in the Database Extent binary card is added in the post-processing, history plot Element >select the X-stress and plot and in the save option to interpolate the values of 50 based on the given stress-strain data suppose the given values are 30 then the simulation we need to interpolate the date of the 30 points stress vs time and likewise lower point strain in the x-direction is selected save the data points of 50 from the curve. From the post-processing, XY option selected the cross-plot option after selecting the strain in x-direction and stress in the Y-direction used as shown below.







Observations:

1. If we observe the extracted curve values and simulated values of true stress and true strain values are almost similar and interpolated values I have used only 50 values of stress and stress because that curve trend showing mid of the original curve.

2. And the curve is working as per the input curve for the MAT_024.