ICME 2017 HW4

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Overview

In this homework, we will bridge information from grains to the continuum point, ie. from the mesoscale to the macroscale. There are two parts:

• Crystal Plasticity (CP) using Abaqus or Calculix and a user developed Crystal Plasticity Finite Element Method (CPFEM)
• MSU Internal State Variable (ISV) Plasticity-Damage Model via DMGfit and Abaqus or Calculix

We will get the polycrystal stress-strain response from the crystal plasticity code, and use that to calibrate the continuum model.

All necessary input files and scripts are provided on the website, except the MSU ISV Plasticity-Damage model which will be provided via email. Move these files to your own directory (and make a backup copy) before trying to perform any simulations.

Use /scratch/"Your Directory" for best results.

Write a full report that follows a journal article manuscript format (include figures and tables in the text). Please double-space your document

Upon completion, submit via email a .pdf and .doc(x) file. Be sure to also include the requested files and plots from each section of the homework.

Part 1 - Crystal Plasticity Virtual Experiment

Objectives

• Run a multigrain crystal plasticity single finite element simulation

Environment Setup

The setup for CPFEM is the same as in the previous homework with one exception. Instead of using a single grain as previously, you will want to use at least 180 grains. You will need to modify the test.xtali and texture.txti input files, as well as the *DEPVAR variable in the single-element input deck appropriately.

Homework Assignment

a. Run a one element finite element simulation in compression, tension, and torsion using crystal plasticity. Use a minimum of 180 grains to plot the stress-strain curves that will be used for calibrating the macroscale model.

b. Plot stress-strain curves for compression, tension, and torsion using an average of the polycrystalline aggregate from the three hardening sets determined in HW3.

c. Report your results.

Part 2 - Internal State Variable Model

Objectives

• Calibrate the macroscale Internal State Variable (ISV) model
• Run a one element finite simulation to verify the calibration

Environment Setup

• You will need the calibration software: DMGfit.
• You will also need the DMG UMAT (similar to the crystal plasticity umat). You should receive this from me by email.

ISV Model Calibration using DMGfit

Calibrate the ISV model to the stress-strain data you obtained from Part 1.

• Use the compression, tension, and torsion curves
• You should only need the parameters for yield, isotropic hardening, and stress state dependence on the hardening.

There is a tutorial video here, and tutorial files File:DMGfit-Tutorial.zip.

Single Element Simulation with the ISV Model

Once you have your model constants, transfer them into your single element Abaqus input file. You can use the same input file as in Part 1, except change the material section to something like the following:

*** Material Definition ***
*Material, Name=DMG_Cu
*Depvar
    25,
**          G,           a,        Bulk,           b,       Tmelt,          C1,          C2,          C3   
**         C4,          C5,          C6,          C7,          C8,          C9,         C10,         C11   
**        C12,         C13,         C14,         C15,         C16,         C17,         C18,         C19   
**        C20,          Ca,          Cb,       Tinit,        heat,          nv,          r0,          an   
**         bn,          cn,       Ccoef,         Kic,          dn,          fn,         cd1,         cd2   
**       dcs0,         dcs,           Z,        volF,         C21,         C22,         C23,         C24   
**        C25,         C26,         NTD,         CTD,       vvfr4,       CAcon,        beta  
*USER MATERIAL, CONSTANTS=55
      40953.1,           0,      116773,           0,        1360,           0,           0,        33.3   
            0,       1e-05,           0,   0.0502077,     809.219,     476.789,    0.582468,       1e-05   
            0,   0.0587402,           0,     1596.01,           0,  4.99468e-05,          0,           0   
            0,           0,           0,      298.15,        0.26,         0.3,           0,           0   
            0,           0,           0,         790,           0,       0.001,           0,           0   
           30,          30,           0,           0,           0,           0,           0,           0   
            0,           0,           0,           0,      0.0001,         0.5,           0   
*Solid Section, Elset=Eall, Material=DMG_Cu

The lines beginning with ** are comments and show you what each constant refers to in the list below.

Run the ISV simulation similarly to the crystal plasticity simulation,

abaqus job=single_element user=umat_dmg_55p_v1p1.f 

Homework Assignment

a. Use DMGfit to calibrate the MSU ISV Plasticity-Damage Model to the mesoscale polycrystalline plasticity stress-strain curve for your material (see Figure 9.17 pg 401 in textbook). Plot all three stress-strain curves comparing the crystal plasticity results to the plasticity-damage ISV calibration results.

b. Run a one element simulation in ABAQUS with the DMG UMAT to verify the results from Part 1.

• Modify the input decks for compression, tension, and shear to reflect the calibrated parameters determined using DMGfit

c. Compare stress-strain results from the plasticity-damage ISV calibration to the verification results from the ABAQUS single finite element simulation.

d. Show the macroscale ISV constants and uncertainty values in the optimization of the calibration.

e. Report your results.

3. Room for Improvement

As with the previous homeworks, improve the tutorial(s) by adding/modifying the ICME website for:

1. Crystal Plasticity

2. MSU ISV Plasticity-Damage Model