Effect Of Surface Residual Stress On The Fracture Of Nanoscale Materials Containing Mode-I Crack

With the development of science and technology, nanoscience andnanotechnology have experienced a progress, the application of nanomaterials isalso increasing at a rapid pace. Nanomaterials have been widely put in to use inmany aspects like aviation, aerospace, defense, transportation, sports, oil drillingand other fields, as for its excellent overall performance, especially itsdesignable performance in. However, the fracture of nano-materials often cannotignore the surface residual stress effect, due to the size effect, quantum effect andsurface effect, mechanical property of the material will also be changed under themicro-nano-scale mechanical properties and surface forces, etc. With the surfaceresidual stress, the material tends to make deformations, cracks, or even breaks.This paper mainly deals with mode-I crack nanomaterials fracture problem, thestudy of mechanical property which the surface residual stress works on thenanomaterials. To study expansion of the crack tip fields which are near to thecrack propagation; we need the crack propagation displacement, intensity factorand the energy release rate and the graphic distribution of the crack of thesemi-major axis. It will be also shown the proccess given by the theory and theresult as follows, from the further discussion over the probability distribution ofthe crack propagation and the length of the crack presents.(1) The question of two-dimensional stress field where the surface residualstress load affected by infinity isotropic nanomaterials containing mode-I crack.By using the constitutive equation, we can get the solution of crack tip. It alsoshows the crack changes when M1points out the relationship between thedisplacement of crack propagation, the intensity factor, and the energy releaserate and C1and calculates the exact solution.(2) As the M1the exact solution is difficult to calculate, the approximatesolution can only be obtained through an iterative approach; as can be seen fromthe graphical analysis, the increase are in cracks radius a, COD/COD0、K/K0and G/G0approaches1. This means that when the length of the crack radiusincreases to a certain value, surface stress crack deformation and crack tip stressintensity factor and the energy release rate becomes weak or no effect. When thecrack length is reduced to the nanometer level, the effects of surface stress forcrack propagation are more significant. Surface residual stress is particularlyevident for the impact of the crack tip stress field. (3) From the introduction of probabilistic fracture mechanics, with the increasein crack radius changes, crack propagation is presented power-law distribution, inline with the probability distribution derived from the graphical analysis.(4) The deformation is obvious,through the analysis of the residual surfacestress on the entire surface of the surface residual stress at the crack tip stress fieldnear the crack. The results show that: it is not sufficient to express the crackdeformation and crack tip field, in the case of the initial crack, including the effectof the surface in a small area near the crack tip. It has connection between therelease rate surface residual stress and Crack propagation displacement, stressintensity factor.