腐蚀对钢箱梁多尺度裂纹扩展性能的影响试验研究OA

[Objective]To accurately simulate engineering service conditions and evaluate the impact of corrosive environments on crackpropagation in a steel box girder structure,this study conducted material-and structural-scale corrosion-environment and mechanicalperformance tests.[Methods]Material-level compact tension(CT)specimens and a steel box girder model were fabricated,with initialcracks introduced via artificial defects and fatigue loading.Corrosion tests were then conducted separately:CT specimens were exposed toa coastal field environment for three months to simulate marine atmospheric corrosion,whereas the box girder model underwentaccelerated corrosion in a laboratory chamber for one month.Fracture toughness tests were performed on CT specimens before and aftercorrosion,and crack propagation tests were conducted on the box girder under cyclic fatigue loading.[Results]Key findings include the1following:(1)At the material scale,fracture toughness of the uncorroded welded CT specimens was 237.4 MPa m1/2,which increased to1380.0 MPa m1/2(~60%increase)after three months of coastal exposure.This is attributed to corrosion-induced blunting of the sharp cracktip,which raised the energy required for crack re-initiation.(2)At the structural scale,after accelerated corrosion,only two of threepre-existing cracks on the box girder(at the#4 support point)propagated under cyclic loading,with a significant delay in crack initiationthat further supports the crack-tip-blunting effect.Propagation paths traversed corrosion pits,where the crack rate slowed or briefly halteduntil a new sharp tip formed on the opposite side,rendering the paths more complex and discontinuous.(3)The two propagating cracks atthe#4 support point grew essentially perpendicular to the primary load-bearing direction,predominantly as Mode I(opening mode);thefastest crack(#4-V-b)propagated at 2.06xl0-3 mm/cycle along a largely linear a-N curve,indicating stable fatigue crack growth.[Conclusions]This study reveals dual effects of corrosive enwronments on crack propagation in steel box girder structures.Corrosionenhances fracture toughness by blunting the crack tip,inhibiting crack initiation.However,pre-existing corrosion pits can act aspreferential propagation paths and cause growth fluctuations,increasing the risk of local failure.