内河运输船舶碰撞与搁浅的数值模拟英文文献和中文翻译
Collision and grounding occur quite often in the inland waterway navigation. They will continue to happen no matter how a barge is designed, constructed and operated. The ongoing re-search in this field aims to assess damages, to minimise the consequences of the accidents and suggest ways of improving damage resistance in design. The analysis of structural damage caused by ship colli-sions is complex. The impact response is highly non-linear, involving continuous changes in the geometry of the ship structures. The observed failure modes from ship accidents reveal that the primary energy absorbing mechanisms are: crushing of decks, tearing of bottom plating, folding of web frames, and stretching of shell plating. Two approaches can be distinguished when describing the methods for the analysis of colliding ships: simpli-fied and numerical analysis. Simplified analytical mod-els have been suggested on the basis of rigid-plastic theory to derivation of crushing models for basic struc-tural units. These methods do not account for coupling effects between local and global failure modes.
These models are more suitable for bow collisions where local failure modes are predominant and this coupling can be neglected. Typical for the analytical approach is the Minorsky method (Minorsky, 1959). It has been demonstrated that non-linear FEM simula-tions are reliable and very detailed (Amdahl et al., 1995). Powerful special-purpose FEM packages e.g. DYNA3D, DATRAN and PAM SYSTEM account for large deformation, contact, non-linearity in material properties, and rupture. Published investigations using FEM simulation techniques include: (i) large scale model tests; (ii) real case collision accidents, and (iii) real case grounding accidents. It has been concluded that FEM simulation requires a massive effort both in terms of modelling and computer power. The cost of this analysis is often prohibitively expensive. Kitamura (2002) thoroughly discussed the problem of the finite element analysis pointing out various aspects of such analysis: coupling with hull girder horizontal bending, stretching span and equivalent failure strain, deformation of supporting structure, forward velocity of struck ship, collision angle and bending of bow, folding of flat plate and stiffened panel and partial crushing of bow structure. According to his opinion FEM approach is a unified way that covers all fields of strength analy-ses. In the long run, only a few matters might be left to the discretion of a designer who intends to perform a standardized FEA. Until early 1990s, the advantage of FEM approach was quite limited compared with the simplified analytical approach. The extent of finite element model and its mesh size were restricted within the unsatisfactory lev-els because of the insufficient capacity of the memory and CPU power in addition to the discouraging compu-tation cost. Following the successful progress of the modelling technique, the simulations of non-linear elasto-plastic response of complicated hull structure is now practica-ble. Geometrical stress concentration and local bending of plates in the multi-axial stress field can be considered more systematically than ever as well as quasi-uniform membrane stress, provided that due consideration is taken on the mesh size and pattern of finite elements. Time-dependent strain hardening and strain rate effects on the material properties are also counted at every step of the progressive deformation. The finite element mod-els can be recycled many times and the results can be reviewed repeatedly from various aspects on demand. Compared with the implicit finite element code, the explicit finite element code is considered to be more suitable for the collision and grounding simulations of large ships at present. The great advantage of the ex-plicit finite element code is that the simulation model of numerous finite elements can be handled, while the disadvantage is the reduced accuracy due to explicit formulation itself. The disadvantage, however, can be resolved practically by the adoption of fine mesh size and proper time increment.
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