High Strain Rate Simulation using Abaqus

[MEC_TECH]

Hello Everyone,

I have created a Split Hopkinson Pressure Bar simulation setup in Abaqus to capture the force acting on the bars. However, the results I obtained are all single digit Newton values which is unrealistic for steel bars and an aluminium specimen. The impact velocity is set to 10 m/s. The elastic properties are defined for the bars. As for the specimen the elastic, plastic and damage model are defined.

For the force, I select an element on the bar (incident) and plot the NFORC VS TIME. With that the values displayed are not logical. I tried finding the CPRESS option but I can't seem to find it. In terms of the boundary conditions, all degrees of freedom are constrained except for the degree of freedom associated to the loading axis.

Any ideas to solve this issue?

 

[FEA way]

Check the resultant force in the specimen using the freebody cut tool. Also, make sure that all units are correct. Does the deformed shape look fine ? What about the stresses and strains ?

 

[MEC_TECH]

Looking at the free body cut tool, it shows extremely high peak forces. Units I am using are tons, mm,and N. The specimen doesn't fracture even when Johnson Cook fracture criterion is defined and element deletion is set to yes. However the stresses are very low.

Incident bar > Steel: YM 210e+3 MPa and PR 0.28
Transmiaaion bar > Aluminum: YM 69e+3 MPa and PR 0.3
Specimen > Steel: YM 210e+3 MPa and PR 0.28
Plasticity: Johnson Cook, A 792 MPa, B 510 MPa, n 0.26, m 1.03, c 0.014, ref strain rate 1, Tmelt 1793 K, Ttrans 293.2K
Damage model: Johnson cook, d1 0.05, d2 3.44, d3 2.12, d4 0.002 and d5 0.61

 

[MEC_TECH]

I have tried changing the plastic data from Johnson Cook to isotropic and inserted the plastic region data of the tensile test. This time I have not introduced any damage model as to see if the data was the problem. Sadly there is a problem with the values. I have attached the cae file, if someone can help me understand the problem. Note I am using a not soo fine mesh to get a first approximate. Additionally, the units are N, kg, m, s.