Underground UXO Detection Simulation Based On Unstructured Edge-based Finite-element Method

Unexploded Ordnance(UXO)is a kind of ammunition that has been armed,fired and not exploded due to malfunction,mainly from historical wars or military activities,including bullets,grenades,artillery shells,explosives,mines and missiles.These unexploded bombs are often buried in shallow locations underground or even exposed above the surface,posing a great threat to the safety of people and property and hindering social and economic development.According to the United Nations,there are more than 100 million unexploded bombs buried worldwide,killing tens of thousands of people every year and contaminating a large amount of land with unexploded bombs.Therefore,the detection and precise exclusion of underground UXO is of great significance.UXO detection technology based on electromagnetic induction has existed for many years and can serve all phases.However,the current electromagnetic induction simulation generally only considers the response of the metal target body,ignoring the influence of the surrounding media,and lacks research and discussion of complex situations,which affects the progress of the technology.Facing the future development trend,various complex situations(UXO shape,burial depth,soil magnetic permeability,etc.)need to be considered to meet various needs and achieve accurate and efficient detection.In this paper,we conduct simulation of underground UXO detection based on the nonstructural vector finite element method,analyze the effects of various simulation parameters on the characteristic curves of UXO response,and find certain laws from them to provide a reference basis for inversion calculation and field detection.The unstructured tetrahedral mesh effectively portrays the complex UXO morphology and different media partition interfaces,and can be flexibly encrypted for the local mesh.The use of vector interpolation basis functions can avoid the appearance of pseudosolutions,and the quadratic field separation method can solve the source singularity problem.In this study,the weak form equations of the finite element method are developed based on Maxwell equations of electromagnetic field.Then Galerkin’s method is utilized to discretize the control equations for finite element analysis and the interpolation basis functions of tetrahedral vector cells are used to obtain the local equations of each cell,followed by fitting the set of local equations into a large sparse global matrix and calculating the forward response of the target using the direct solution method.In this paper,the constrained Delaunay tetrahedron is constructed based on the constrained Delaunay triangular dissection algorithm,which can guarantee the quality of the grid,and the grid is locally encrypted,then the air,underground space,antenna system and eight different forms of UXO models are designed,and we calculate the forward responses of UXO models in different forms and analyzes their characteristics.The results demonstrate that the algorithm exhibits excellent horizontal positioning resolution.Meanwhile,this paper also studies the effects of UXO attitude,transmit signal frequency,soil conductivity,magnetic permeability and coil arrangement,compares the differences of UXO model response under different parameters,and analyzes various influencing factors and their characteristic laws.This paper also carries out the technical flow,structural design and visual interface design of software development based on the App Designer function of MATLAB computing software,using a series of visual interface design tools and components to complete the interface construction of the application,using control callback functions for data input and output,and finally packaging the running error-free code to form a downloadable EXE package.This approach provides a way of thinking for developing GUIs,which can bring some reference significance for other MATLAB-based software development efforts.In this paper,the unstructured grid and vector finite element method are introduced into the UXO detection,and the forward response calculation is successfully realized,and various detection parameters are simulated and studied.The results provide a theoretical basis for field exploration,and also lay the foundation for inversion work.