Study On Damage Similarity Of Stiffened Plates Subjected To Underwater Explosion Loads

The research on damage similarity of stiffened plates subjected to underwater explosion loads has important application value in the field of ship structure protection and damage assessment.At present,the effective research method is to carry out the real ship test,but the cost is huge,so it is necessary to carry out similar research to predict the prototype according to the response of small-scale model,put forward the damage similarity standard and obtain the rule experience of response similarity,so as to provide support for the prediction and evaluation of ship structure damage and guide the subsequent model test and ship structure design optimization.In this paper,theoretical analysis and numerical simulation method are used to study the plastic deformation similarity,boundary tear similarity and local damage similarity of stiffened plates subjected to underwater explosion loads from three aspects of plastic displacement,initial velocity and damage phenomenon.The main research contents are as follows:The research background and significance of the damage similarity of stiffened plates subjected to underwater explosion loads are expounded,and the failure mode,dynamic response,dimensional analysis and similarity of stiffened plates subjected to the explosion impact loads are summarized,meanwhile analyze and summarize the research status.Then summarize and compare the damage modes of the real ship plate frame and the small-scale test stiffened plate,and carry out the equivalent analysis;introduce the basis of the similarity theory and the derivation method of the similarity criterion,and use the dimension analysis method of π theorem to deduce the similarity relationship between the physical quantities in the structural impact response problem under the geometric similarity;finally,the effectiveness of the numerical simulation method is verified.A similar study on the plastic displacement response of stiffened plates subjected to uniform impact load is carried out.Firstly,the stiffener is simplified as the thickness of the plate,and the main physical parameters affecting the damage of the rectangular plate in the process of underwater explosion are selected,and the maximum plastic displacement of the center of the rectangular plate is used to express the damage degree;then dimensional analysis is applied based on the energy and impulse of shock wave,combined with Jones damage number and Response number,the classical dimensionless number is deduced,the limitation of the dimensionless number is analyzed and the improvement is put forward.Finally,the application of the improved dimensionless number in the prediction of plastic deformation damage of real ship plate under underwater explosion is given.The similar relationship between the initial velocity of stiffened plates and boundary tensile tear subjected to uniform impact load is studied.Firstly,the relationship between the initial velocity of the fixed rectangular plate and its failure mode is deduced,and the influence of strain rate effect and fracture toughness on the damage similarity of stiffened plates is analyzed by using similarity theory.Then,the semi empirical formula of the dimensionless initial velocity of the plate from plastic deformation to tensile tear is obtained by using the existing test data analysis and fitting.Finally,the theoretical and numerical simulation are used to the important parameters affecting the tensile tear of the plate were studied and determined.Combined with the numerical simulation data,the dimensionless similarity criterion for predicting the critical tensile tear for relationship between initial velocity and structural strength of a clamped rectangular plate is proposed and its application process is given.The damage phenomenon and similar research of stiffened plates subjected to local loads of near-field underwater explosion were carried out.Select typical stiffened plates as the research object,use AUTODYN software to study the effect of charge,detonation distance,material and shrinkage ratio on the damage of stiffened plate;based on qualitative analysis,the conclusion that the damage of stiffened plates is almost impossible to be similar is obtained;finally,it is proposed to study the damage similarity of stiffened plates from two aspects of damage assessment consisting of damage management and ship vitality.