Learning Forum

[20217579]

Hello, I am trying to modal delamination under mode-II in an End Notched Flexural modal using seperation based debonding under Mode II. I have created the model from surface in ACP-Pre and define the inteface during modelling the plies. The problem is that the delamination is not occuring and I am getting a linear load displacement plot. I have given the number of subsets  a value of hundred and defined a frictionless and bonded contact at the precrack and contact debonding interface respectively. I have also set the bonded contact formulation to pure penalty. Meanwhile during and after solution I am getting the following warning messages;

"The fracture parameters computed during solution may be incorrect. Check the Solver Output on the Solution Information object for possible causes".

"Contact status has experienced an abrupt change.  Check results carefully for possible contact separation".

"The reference convergence value may be less than the threshold, you can overwrite the minimum reference value by specifying it under the nonlinear controls of analysis settings".

"There is at least 1 small equation solver pivot term (e.g., at the UY   
 degree of freedom of node 397257) which may indicate a numerically      
 unstable model.  Please check your results carefully". 

[Ashish Khemka]

Hello,

For the messages you encountered:

1. Fracture Parameters Incorrect:

   • This warning often indicates issues with the calculation of fracture mechanics parameters. Ensure that the crack tip nodes are not attached to unsupported element types. You might need to remove contact elements at the crack front if they are present.

2. Contact Status Abrupt Change:

   • This warning suggests that the contact status is rapidly changing between “closed” and “far open” without passing through "near open". You can try reducing the time step size or increasing the pinball radius to stabilize the contact status².

3. Reference Convergence Value Less Than Threshold:

   • This warning indicates that the reference convergence value is very small, which can happen when applied loads are minimal. You can override the minimum reference value by specifying it under the nonlinear controls of the analysis settings.

4. Small Equation Solver Pivot Term:

   • This warning usually points to a numerically unstable model, often due to large deformations or insufficient constraints. Ensure that your model is properly constrained and consider refining your mesh or adjusting the solution method.

Regards,

Ashish Khemka