Study On Large Slip Contact Problem Of Projectile And Barrel Using Isogeometric Analysis

During the launching process of artillery,the interaction between projectile and barrel is a large slip frictional contact problem which belongs to one of the most challenging problem in computational mechanics.The traditional modeling method is unable to accurately describe the contact surface between projectile and barrel and the interferential mesh will inevitably lead to a series of unstable numerical calculations in contact analysis.With the increasing requirements of firing range and accuracy for modern artillery weapons,there is a higher precision demand for the modeling and analysis of the launching process of projcetile.The traditional design theories and modeling methods are difficult to meet the requirements of high performance weapons.Therefore,it is imminent to seek the new design theory and numerical methods to improve the precision and efficiency of the launching process.Taking this background into consideration,the Isogeometric analysis(IGA)method was used to study the large slip contact problem of projectile and barrel.At present,there are no available commercial softwares and open source programs for Isogeometric Analysis method,hence,the framework was conducted by using FORTRAN independently.A standard numerical example,stress concentration problem of infinite plate with a hole,was calculated to prove the computational accuracy and efficiency of IGA.The different refinement strategies were investigated based on the example and the convergence speed was discussed.The IGA and traditional FEA were compared comprehensively from the basis function,geometric description,refinement process and calculation process.The advantages of choosing NURBS as the basis function include exact geometry,Cn continuous boundary and the uniform of CAD and CAE,etc.Start with 2D contact problem,the KTS(knot to surface)algorithm in IGA was introduced.The implementation process of two-dimension IGA contact algorithm is derived and embedded in the IGA framework.The interference assemble problem was analyzed by IGA and traditional FEA,respectively.The accuracy and continuity of contact stress were compared and the results show that IGA has obvious advantages.The Mortar algorithm and Augmented algorithm were introduced to improve the penalty contact algorithm.A modified augmented factor algorithm was proposed combing with the Mortar algorithm and Augmented algorithm.By analyzing the model with different penalty factors and mesh density,it was demonstrated that the proposed algorithm can effectively suppress the oscillation of contact force at the edge of contact region and weaken the influence of penalty factor.Because of the highly nonlinear of Kulun friction model,a numerical algorithm which is easier to converge was introduced to the frictional contact framework.The validity of frictional contact algorithm was verified by an example of ring rolling.Further more,the frictional contact problem of two-dimension projectile and barrel was analyzed and the contact force and the motion law were discussed qualitatively.On the basis of 2D Isogeometric contact algorithm,the numerical solution process of 3D Isogeometric contact analysis was deduced and the framework was extended into three dimension which satisfies the patch test.The NURBS model of 3D projectile and barrel were constructed according to the structural and motion characteristics.On this basis,the 3D large slip contact problem of projectile and barrel was studied and the contact force at different positions of the band were analyzed in detail.By comparing with ABAQUS,it was proved that the smooth NURBS geometry can effectively avoid the singularities and cusps in finite element meshes,and it has a higher performance of robustness and accuracy.By comparing the motion process of different projectile width and projectile diameter,the influence of proj ectile structure parameters on the motion parameters of the projectile was obtained.Furthermore,the Isogeometric analysis was applied to the structural optimization of projectile and barrel.To improve the barrel stiffness,four groups of genetic algorithm strategy were calculated using the IGA structural optimization method.All strategies got the same results and the barrel stiffness was effectively improved.The structural parameters of band and barrel were taken as the design variables,and the large slip contact process of projectile and barrel was optimized.The optimized model could effectively reduce the initial projectile disturbance at the muzzle.By comparing the calculation efficiency and the complexity of optimize process,it was proved that the Isogeometric structural optimization is more efficient.