On fracture resistance parameter from non-standard fracture test specimens of titanium alloy

The current available design rules of submersible structures from ship classification societies are based on the philosophy of strength design. As a supplement, damage tolerant design becomes an important consideration in avoiding the catastrophic failure caused by material defects. Titanium alloys with relatively high ductility are widely used in pressure hull of submersibles nowadays. Much work should be devoted to systematic investigation of the fracture properties evaluation for candidate titanium alloys for submersible structures. Traditional fracture toughness test with normal specimen size may not give reliable fracture resistance value. More applicable non-standard specimens can be designed for engineering purpose. Then the establishment of a reliable fracture resistance parameter from the non-standard fracture test specimen for fracture ductility evaluation is necessary. The present work is to primarily study the potential proper fracture resistance parameters for ductile titanium alloys. Series of non-standard specimens of Ti80 are designed for the test and analysis. Thickness effect is specifically investigated using specimens with similar ligament size. Some fundamental proposals are accordingly brought forward for ductility evaluation of titanium alloys used in submersible structures.)