TWO-PARAMETER FRACTURE ASSESSMENT OF THROUGH-THICKNESS CRACKS IN AN ALUMINIUM BRIDGE STRUCTURE

摘要

The bridge is a lightweight utility, fabricated using a weldable aluminium alloy. During laboratory fatigue testing, cracks were detected in the stem of the bridge main tension chord, where damage is most critical. The bridge sustained much longer critical crack lengths before failure than estimated from linear elastic fracture mechanics, using toughness data obtained from highly constrained specimens. To solve this discrepancy, three-dimensional elastic-plastic Finite element analysis of the girder has been carried out. The cracked bridge girder is shown to be a low constraint geometry. Two-parameter theories are used to construct fracture toughness loci to match the toughness of the girder with that of low constraint specimens, leading to far better correlation between the numerical and experimental results.