Dynamic Fracture Behavior And Consequence Assessment Method Of Gas Pipe Explosion

Gas pipe explosion has continued to draw attention because of its exgineering and scientific importance.The structural dynamics,fluid dynamics,fracture mechanics and chemical reaction dynamics it involves are closely coupled together,which makes it a multi-field and multidisciplinary complicated problem.Furthermore,strong nonlinear fluid-solid coupling exists between the blast wave and pipe.The high pressure due to explosion induces structural deformation and fracture.The opening cracks and deformed structure in turn gorven the gas dynamics.All these make the accurate and reliable prediction of dynamic fracture and consequences of gas pipe explosion as one of the most challenging and difficult task.Under the support of National Key Research and Development Program of China and National Natural Science Foundation of China,the dynamic fracture behavior and consequences of gas pipe explosion were studied.The main content and conclusions are as follows:(1)The fluid-structure interaction between blast wave and pipe was studied based on the Smooth Particle Hydrodynamics-Finite Element Method(SPH-FEM)method and the developed bivariate failure criterion applicable to materials at high strain rates.Results showed that the blast wave will reflect and attack the pipe wall several times,but its intensity reduced dramatically.The crack begins to propagate from the inner wall of pipe along both the pipe axial and wall thickness directions.Once the crak run through the pipe,the blast wave propagates through it and continues to move forward.Furthermore,the deformation and fracture of pipe have a significant weaken effect on the shock wave intensity,which should be considered in the consequences assessment of pipe explosion.(2)According to the CJ detonation theory,an efficient gas detonation modeling approach with simplified chemical reaction rate law was established.A stability based fluid-structure coupling approach was developed based on the penalty contact algorithm.The dynamic fracture behavior of pipe under internal gaseous detonation then was predicted and studied.It was found the simulation well reproduces the dynamic crack propagation and branch behavior in the experiment.In addition,the simulated strain responses,crack propagation speeds and the venting of detonation products all show a good agreement with the experiment.Compared with other studies in open literatures,the approach in this paper can predict the dynamic fracture and the final fracture pattern of pipe under gaseous detonation more accurately.(3)A formula of peak overpressure against the scaled distance was presented to describe the blast wave attenuation out of the pipe.A consequence assessment method based on fluid-structure coupling algorithm was established and then applied to study the consequences of gas pipe explosions.It was found the peak overpressure outside the pipe appears to increase linearly with the initial flaw length.The pipe destruction extent and the corresponding consequeces are more serious when equivalent TNT explodes in the same pipe.The intersection of axial crack and branch crack causes the pipe debris to be formed.Compared with currenttly used empirical methods and traditional CFD methods,the proposed method which fully considers the energy consumption during pipe deformation and fracture can assess the consequences of gas pipe explosion more reliably.