matrix coefficient ratio exceeds 1e8

- September 6, 2019 at 3:02 pm
  
  Jirong
  Subscriber
  
  Hi All
  
  I am using transient structural to do the simulation with Mooney-Rivlin material. I got error said "Matrix coefficient ratio exceeds 1.0e8, check results carefully." and then highly distorted element was reported. What should I do to reduce the matrix coefficient ratio and how can I extract it?
  
  In Analysis Settings, I turn on the large deflection, and use Damping for nonlinear control, and set stiffness coefficient to 1e-4 under damping controls.
  
  I have used the same geometry with isotropic elasticity material before, it worked without matrix coefficient warning. Or is this because of my material ?
  
  Thanks,
  
  Jirong
- September 6, 2019 at 4:54 pm
  
  Sandeep Medikonda
  Ansys Employee
  
  This warning message means stiffness matrix of the model is ill-conditioned. Some elements have severe differences in stiffness from other elements.
  
  The ill-conditioned matrix can occur due multiple reasons such rigid body motion, highly distorted elements, high frictional contacts, units that may results in numbers too big/small, or even unstable material models.
  
  Generally speaking about this message, it is just a warning and can typically be ignored.
- November 20, 2023 at 6:19 am
  
  Rukmini Sai Rupa Sri Mada
  Subscriber
  
  This is one of the warnings i am getting during the simulation
  The eigenproblem is ill-conditioned (relative residual from test linear solve: 6.084859E-03). The accuracy of the solution may not be satisfactory. Modifying the initial value of the frequency shift (FREQB in the MODOPT command) or changing the boundary conditions of the model might solve the problem.
  
  How do I address this?