For Modified Newton-Raphson method and Full Newton-Raphson method

How does Marc uses these two kind of methods during calculation? Does these two kind of methods have a effect on final result?

In my opinion, these two methods only influence the convergence rate and if the calculation convergenced then the result should be similiar. I do a comparation test by changing this option in Marc, and the result shows big difference.

Thanks.

0 Kiranraj Shetty over 5 years ago

Hi Ddenzel,

In the Full Newton-Raphson method, The tangent stiffness matrix is reformulated for each iteration (recycle).

In the Modified Newton-Raphson method, the tangent stiffness matrix is formulated only once per increment.

If contact or sudden material nonlinearities occur, reassembly cannot be avoided. The modified Newton-Raphson method is effective for large-scale, only mildly nonlinear problems. When the iterative solver is employed, simple back substitution is not possible, making this process ineffective. In such cases, the Newton-Raphson method should be used instead.

If you are expecting contact and material nonlinearities, then use the default N-R method.

Regards,

Kiran
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0 zhong.qin over 5 years ago

Try smaller convergence tolerance and see if the results improve.
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0 denzel.li over 5 years ago

Thanks，I changed convergence tolerence ， used a absolute value of residual and smaller step，the result shows similar with the one used full Newton-Raphson. It need more cycles to get convergence in each increment than full Newton-Raphson mehthod.

By the way，is the tangent stiffness matrix calculated only once or recalculate after serveral cycles in one increment when using Modified Newton-Raphson method？
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