Numerical Study Of Ice And Ice-Ship Interaction Based On Ordinary State-Based Peridynamics

Peridynamics(PD)as an integral form of particle method has great advantages in dealing with fracture problems and large deformation problems.At present,the theory of PD applied to the ice-structure coupling interaction mostly adopts the bond-based type,and very few studies use the state-based type,especially in the application calculation close to the engineering practice.However,the bond-type PD has limitations on the Poisson’s ratio of the material(the Poisson’s ratio is limited to 0.25 for the three-dimensional calculation case and 0.33 for the two-dimensional calculation case),which leads to the calculation of the ice-structure coupling interaction.The real Poisson’s ratio of ice is ignored(from the overview in Chapter 1,it can be seen that the Poisson’s ratio of ice is often greater than 0.33),especially in three-dimensional working conditions,the Poisson’s ratio set by the algorithm is quite different from the real situation.In addition,due to the lack of more advanced numerical calculation methods and parallel calculation methods,the current PD calculation of ice-structure coupling effects is mostly limited to simple calculation conditions,simplified ice constitutive models and rough Particle Discrete Domain.In order to study the mechanical properties of ice-structure interaction in a more accurate way with its real Poisson’s ratio and highly efficient computation,the present work employs the OSB-PD method as the govern equation.Corresponding to physical and mechanical properties of ice in different environments,the different constitutive models of ice suitable for different working conditions are established respectively,including the elastic constitutive model(PMB)based on the original OSB-PD and the failure criterion of critical stretch,elastic-plastic constitutive ice model based on OSB-PD and Von Mises plastic model,thermoelastic constitutive model based on OSB-PD and non-local thermodynamic governing equations.Moreover,fast continuous contact detection algorithm and high-performance computing methods are also developed to achieve efficient computing.The basic theory of the OSB-PD method was introduced in detail and systematically.An elastic ice constitutive model(PMB)based on the original OSB-PD and the failure criterion of critical stretch is established.The numerical calculation method of conventional PD is discussed.The benchmark case is verified by comparing with FEM results,and the influence of different Poisson’s ratios is analysed.Then the constitutive model is applied to the calculation of ice collision.The calculation results of OSB-PD and BB-PD(equivalent to the calculation results under Different Poisson’s ratios)are compared and analysed.Finally,the sensitivity analysis of variable parameters is carried out,and the effects of different calculation conditions and numerical calculation parameter settings on the results are discussed.A contact detection algorithm suitable for PD method is then proposed to solve the impact problem in PD framework.By comparing with the commonly used particle discrete contact detection algorithm,the present method shows superior efficiency.The contact detection algorithm for complex structure shapes is proposed to solve real world engineering problems.The basic theory and numerical implementation process of the algorithm are introduced.The accuracy of the proposed algorithm is verified by a benchmark case,and the sensitivity of grid discretization is analysed.Further development to improve the computational efficiency of PD method was carried out.Three aspects to improve the calculation efficiency of PD were proposed.More specifically,the updated linked list search method is used to replace the traditional brute-force search method to maximize the calculation consumed in the process of optimizing neighbourhood particle search;Second,according to the principle characteristics of PD method,the integral of particles is converted into the integral of bonds(that is,the integral of particle pairs),which reduces the repeated recording process of two interacting particles and saves the computational time;Third,the parallel computing technology of PD method based on message passing interface(MPI)is developed to improve the computing efficiency of PD method through hardware equipment.Finally,the efficiency improvement effects of the three methods on the PD calculation process are evaluated.Such improvements significantly enhancing the capacity of PD method in dealing with the computational intensive cases,such as the difficulty of fine solution,complex engineering application and program debugging.The elastic-thermal coupled constitutive model of ice material based on the OSB-PD method is developed.The numerical implementation process of the model is introduced in detail.Taking the plate compression model as the benchmark case,the accuracy of the model is verified by comparing the finite element results.Then the underwater explosion model is established based on the load mentioned above.In this study,the exponential decay constant under loading is regarded as an unknown parameter,so it is numerically discussed by the numerical inverse analysis method for the first time.Considering that fracture toughness is the main threshold of sea ice damage,the influence of fracture toughness is further analysed.The breaking process of ice sheet is simulated by a comprehensive mechanical and thermal coupling model.The corresponding temperature distribution is studied.The damage and crack propagation of ice plate are analysed and compared with the uncoupled case,and the damage in all cases is compared with the existing experimental results.The elastic-plastic constitutive model of ice based on PD theory embedded in the Von-Mise plasticity criterion is established.The deformation force density and tensile relationship in the constitutive model theory,the manifestation of the three elements of plastic deformation(yield condition,flow criterion and hardening law)in PD,and the failure criterion of nonlinear energy release rate based on the elastic-plastic constitutive model are introduced in detail.The numerical implementation program of the constitutive model is constructed,and its MPI parallel computing program framework is compiled.The plate tension is calculated and compared with the finite element results to verify the accuracy of the model and program.The model is applied to the numerical analysis of four-point bending tension ice.The numerical prediction model of ice-ship interaction is established.The continuous icebreaking process of an ice breaker is simulated,and the icebreaking load and icebreaking phenomenon are compared with the experimental results and empirical calculation results.The accuracy of the model is verified.The icebreaking loads of the model icebreaker under different speed conditions are analysed.By taking two typical bow shapes(non-traditional bow and traditional bow)as the calculation object,the icebreaking differences of different bow shapes are compared and analysed,including ice breaking load,icebreaking cycle,icebreaking channel and ice breaking width.