Study On The Interface Morpholgy And Shear Behavior Heterogeneity Of Explosive Welding 304 Stainless Steel/Q245R Carbon Steel Plate

With the high material performance requirements in engineering practice,the metal composites manufactured by explosive welding is favored by engineering application.The phenomenon of interface delamination and cracking in service determines the useful life and reliability of the composites which has been concerned widely and researched systematically.Based on the study of the surface morphology and shear behavior inhomogeneity of explosive welding 304 stainless steel/Q245 R carbon steel plate,the theoretical analysis of the welding interface was studied relayed on the fluid-plastic model and the instability theory.Then,the mechanism of interface heterogeneity detected form transverse section and longitudinal section was analyzed,which is the new perspective to extend the theme of the paper.Besides,In order to reproduce the complex physical and chemical reaction of explosive welding,the instantaneous welding process was simulated with SPH method by AUTODYN software.The variation trend of welding characteristic length with impact velocity and impact angle is compared and analyzed by observing the physical field in the post-processing.Finally,the anisotropy analysis of the bond strength(shear strength)was carried out because of the "rubbing plate" structure of the welding interface resulting in the complicated distribution of the stress.According to shear test results,the relationship between entropy and energy,interface fracture and strength were discussed from the perspective of thermodynamic energy.In this paper,the interface waveform mechanism of explosive welding 304 stainless steel/Q245 R carbon steel plate is discussed.The question of heterogeneity on interface structure and mechanical anisotropy caused by heterogeneity was studied systematically.The simulation of the explosive welding process was carried out successfully with SPH method.The quantitative relationship of interface morphology was calculated precisely.The main conclusions are as follows:(1)The formation of explosive welding interface waveform is the result of the competition between Helmholtz-Taylor integrated instability and fluid viscoelasticity.(2)According to unbalanced equation of motion,the influence of the heat and force effect accompanied by high speed collision between base plate and fly plate was increased with the plate thickness.The interface structure must be uneven along the thickness direction because the detonation process is instantaneous and irreversible.The incompatibility of interaction time and impulse reacting on fly plate is accompanied with the unevenness of the thickness,the density and the boundary condition,which leads to non-equilibrium state of the welding metal micro-elements in all directions and irregular waviness of the welding cross-section.(3)The results of explosion welding numerical analysis show that SPH method is an effective method for simulating high-speed impact welding process.Numerical analysis reveals the distribution of shear stress,equivalent plastic deformation,temperature and velocity,and also draws a conclusion that explosive welding is a combination of plastic deformation,melting and diffusion welding.Based on the comparison experiment of specific strength and impact angle,the results are helpful to guide the practice of engineering practice.(4)The shear test reveals the anisotropy of the interface mechanical behavior,and gives the maximum intensity bearing direction of the interface.According to thermodynamic and physical logic relations,the quantitative relationship among fractal dimension,thermodynamic entropy and interface energy of explosive welding was obtained.A new scientific method for the characterization and prediction of mechanical properties of explosive welding interface was provided by fractal analysis related to information entropy.The fracture entropy analysis shows that the fracture energy depends on the fractal dimension of the rough fracture surface,and the higher the surface roughness,the higher the fractal dimension of the fracture surface and the stronger the interface strength.