Kun Liu

Assessment of material strain rate effects on square steel plates under lateral dynamic impact loads

ABSTRACT The paper summarises experiments and finite element simulations of a square steel plate laterally impacted by a rigid hemispherical indenter. The plastic response until failure is evaluated in a quasi-static and dynamic manner, so that to investigate the importance of the material strain rate for the material characterisation in numerical analyses of similar plate structural components used in the shipbuilding and marine offshore industry. For the purpose, quasi-static and dynamic tensile tests are performed, aiming at defining accurately the material nonlinearities in the simulations of the fully instrumented quasi-static and dynamic impact test. Details of both experiments and simulations are provided, together with a discussion on the Cowper–Symonds material strain rate model, commonly selected for the analysis of ship–ship collisions and/or ship collisions with offshore platforms.

An Analysis of Structural Performances for Bottom Longitudinal Girder and Attached Stiffeners During Shoal Grounding Accident

Simplified analytical methods have been considered fairly efficient for assessing the structural performances during collision and grounding of ships. This paper is centered on modeling of bottom girders and the attached stiffeners during shoal grounding accidents. The published researches on the behavior of bottom girders during shoal groundings were reviewed. Numerical analyses using the code LS_DYNA were conducted for understanding the behavior of bottom girders and the attached stiffeners. A parametric study of the influencing factors was conducted. Simulation included a wide range of sloping angles and indentations. The grounding responses of stiffeners were also presented. The results and conclusions from this paper are preparations for a subsequent establishment of new refined simplified models of bottom longitudinal girders and the attached stiffeners during shoal grounding accidents.Copyright

Research on the Dynamic Response of Stiffened Plates Laterally Impacted by Falling Weight Impact Tester

A proper numerical simulation method is developed to simulate the structure impact problems that consider the effect of strain rate. The high-speed tensile tests are carried out to obtain the strain-stress relations of different strain rates, and used as material inputs to analyze the dynamic response of laterally impacted stiffened plates. The simulation results are compared with falling weight impact experiment, and good agreements are obtained. The strain-stress relations obtained from high-speed tensile tests and Cowper-Symonds constitutive (CS) model are compared. It shows that curves gotten from CS model are higher than those gotten from high-speed tensile test; with the strain rate increasing the distance will became obverse, and the validation of the numerical simulation is verified and can fit the experiment result very well.Copyright