Nondestructive Testing Research Of Surface Microcracks Of Medical Titanium And Titanium Alloy Bars And Wires

Titanium and titanium alloys are widely used in medical field because of their good biocompatibility and mechanical properties.Titanium and titanium alloy bars and wires are mainly used for surgical implants.Because of the particularity of the use of surgical implants,the quality of medical titanium rods and wires is highly demanded.Fine cracks in surface defects of medical titanium and titanium alloy bars and wires are harmful in application.In this paper,the effect of visual,ultrasonic,eddy current,X-ray,coloring and fluorescence penetration nondestructive testing on surface microcracks of medical titanium and titanium alloy bars and wires is studied.Through verification,comparison and analysis,it is found that: the detection probability(POD)of visual inspection for open cracks with width of 0.12 mm is 0.83;The detection probability(POD)of ultrasonic shear wave is 0.9 for surface and near surface cracks of 15×0.1×0.1 mm equivalent-6d B;the detection probability(POD)of eddy current for surface and near-surface cracks of 15 × 0.1 × 0.1 mm equivalent-6d B is 0.92;the penetration detection method,the detection probability(POD)of dye penetration inspection is 0.88 for open cracks with width of 0.05 mm,the detection probability(POD)of fluorescence penetration detection is 0.95 for open cracks with width of 0.04 mm.The reliability of the nondestructive testing methods used in the detection of micro-cracks on the surface of medical titanium and titanium alloy rods and wires was analyzed and studied by means of comprehensive evaluation model,detection probability curve and Bayesian criterion.It was found that the reliability of visual,coloring and fluorescence testing was greatly influenced by human factors,and the reliability of ultrasonic transverse wave and eddy current testing was greatly affected by the detection ability of the equipment.The ways and methods to improve the reliability of non-destructive testing for surface micro-cracks of medical titanium and titanium alloy bars and wires are put forward.