# Finite Element modeling

When to use equation of state models in modeling high velocity impacts?

Equation of state models (Mie-Gruneisen equation of state etc) have been widely used to study hydrodynamic response of material during explosive deformation, ballistic impacts for a long time. As far as I understand, a hydrodynamic response is required to be incorporated in a model if the pressure of impact leads to an increase volumetric strength. That is the stress wave speed in the material exceeds the speed of sound in the material (v = sqrt(elastic modulus/density)).  Ballistic impacts occur at strain rates close to 10^9 to 10^12/s.

Modal analysis performed by NOSA-ITACA code

The following picture shows a screenshot of the NOSA-ITACA desktop enviroment during a modal analysis. In particular the first and the third mode shape of the San Frediano bell Tower in Lucca (Italy) are shown. The structure is discretized into 45641 eight-node brick elements (element no. 8, NOSA-ITACA element library) with 136923 degrees of freedom. For more details sees: R.M. Azzara, G. De Roeck, E. Reynders, M. Girardi, C. Padovani and D.

A phase field formulation for hydrogen assisted cracking [code included]

I hope some of you may find this work interesting, the finite element code developed (Abaqus UEL subroutine) can be downloaded from www.empaneda.com/codes

A phase field formulation for hydrogen assisted cracking

Emilio Martínez-Pañeda, Alireza Golahmar, Christian F. Niordson

Computer Methods in Applied Mechanics and Engineering, 342, pp. 742-761 (2018)

GTN model

I have 2 questions regarding GTN model.

1) What does q1, q2, q3 signify in GTN damage model? What are their physical meanings. I know only their numerical values.
2) How to deal with the problem of GTN in Compression? It is working fine with tension but while in compression it is unable to converge.

Hello everyone,