Application Research On Failure Criteria Of Impact Damage In Ship Structures

Designers are paying more attention on the dynamic failure of ship structure under impact load than the past. While the rapid development of finite element simulation has become an indispensable research, how to establish a reasonable finite element model and use an appropriate material failure model is a reliable basis to ensure the calculation results. But research of failure criterions application in the ship structure failure under impact loading is lack. In this paper, for several widely used failure criteria, simulations are done for three kinds of typical damage phenomenon of the ship structure respectively. The outline below summarizes the research.1 Under the low velocity impact by a knife edge indenter, the plastic deformation of double shell is simulated. By comparing the test results, two types of dynamic constitutive model were verified and compared and the results show that both of them are available. But the JC constitutive has smaller sensitivity on mesh size. Then, under the same velocity impact by a sharp nosed project, the failure of double hull are simulated using the GL, RTCL and JC failure criteria respectively. The results show that considering the effect of triaxlality is good for the simulation of the true fracture and there is no need to consider the strain rate in this situation.2 For two different forms of stiffened rectangular plate, their deformations and failure are studied. The first plate characterized as a large plastic deformation under a lower shock factor. Comparing with the experiment result, the mesh size, constitution model and boundary setting are confirmed. Lately, for the second type plate, the explosion fracture mode is discussed by different failure model of material. There comes that mesh size have a very influence on the simulation of failure. For reason that tearing is the main failure mechanism, the final deformation of plate by different differ a little.3 Simulation of target plate under high speed impact were done using three-dimensional axisymmetric model. For the Weldox 460 E plate with 10 mm thickness, the ballistic is compared between FEM and test and 0.1mm mesh size is accurate to capture the test. Then using the constant, RTCL, JC, shear and BW five kinds of failure criteria, simulation are done respectively. Results show that considering the stress state and strain rates are more accurate. Shear failure is a main mode in the high velocity impact mostly and the Shear failure criterion can better simulate this phenomenon.