Effect of Porosity Defects on Fatigue Behavior of Q355B Butt Joint
Fatigue test,hardness test and microstructure observation were used to study the fatigue properties of Q355B butt joints with porosity defects under uniaxial stress state with weld width of 20mm,25mm and 30mm.The research results show that as the stress level decreases from 220MPa to 160MPa,the discreteness of the fatigue results of the samples increases,and the microscopic failure mode changes from transgranular failure to intergranular failure.The fatigue fracture of the specimens is affected by multiple fatigue sources,and about 41%of the specimens are fractured in the base metal due to the surface fatigue source.When the position of the pore defect is the same,the smaller the weld width is,the shorter the fatigue life is.When the position of the pore defect is different,the closer the defect is to the bottom,the shorter the fatigue life is.Under similar stress levels and defect sizes,the porosity defects in the center of the weld have a greater impact on the weld,and the porosity defects at the edge have a greater impact on the base metal.
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