×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

FEA on the tension to failure on a single Twaron yarn

FEA on the tension to failure on a single Twaron yarn

FEA on the tension to failure on a single Twaron yarn

(OP)
Hello everyone,

Could you help me out from a finite element simulation problem? I have some questions on finite element simulation of a single Twaron yarn under tensile loading to failure situation using Abaqus. The results are compared to the tension tests on such a yarn:
  • yarn length is 250 mm;
  • pulling speed is 1.66667 mm/s;
  • the failure strength is about 2.6 GPa while load at break is about 170 N;
  • and the elongation at broken is about 4%.
The yarn consists of hundreds of Twaron fibres in a parallel way. The fibre can be treated as isotropic material but the yarn has been assigned mechanical properties according to a transversely isotropic material model in the FEA. Such consideration can be found in the paper of Y Duan's work [Finite element modeling of transverse impact on a ballistic fabric].

I am trying to simulate the behaviour of the yarn under tensile loading along the longitudinal direction to get the stress-strain curve including the segment of failure. If I apply the material properties and failure criteria, which is assuming to be ductile damage, on a single element model, I can get reasonable results. But if I use a realistic model, the results are so different. What I have tried is explained as follows.

In my model,
  • density is 1.44e3 kg/m^3;
  • the yarn is modelled as a homogenised rod with a cross-sectional area of 0.0946 mm^2;
  • the engineering constants are 77e9, 0.77e9, 0.77e9, 0, 0, 0, 0.3869e9, 0.3869e9, 0.3869e9, which are E1, E2, E3, v12, v13, v23, G12, G13, G23 respectively;
  • plasticity is isotropic with 2.6GPa, 0 in the table and only this one line;
  • damage is ductile with 0.00355, 1, 0 as the fracture strain, stress triaxiality and strain rate, and the evolution energy is set to be 600J/m^2.
I just want to know what I am doing wrong about these.

1. FEA on a 1cm long yarn using explicit (dynamic) method.
I tried to keep a same pulling speed as that in the experiments, which is set to be a displacement of 0.5 mm on one end in 0.3s.
But the load at break is about 40 N. (Sorry that I am re-running the simulation and could not get a graph on the load-displacement curve.

2. FEA on a 250mm model which is separated into standard (static) method and explicit method.
The STANDARD (static) part is good, but the explicit (dynamic) part is not.
  • The yarn shows a undulation after switching to Dynamic/Explicit method, attached fig 1

  • The Load - Displacement/Original Length curve is not right compared to the experiment curve, attached fig 2


Any comments are appreciated.

Thanks in advance.

Regards,
cnzhx

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources