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The mechanics of ductile fracture is receiving increased focus as the importance of integrity ofstructures constructed from ductile materials is increasing. The non-linear, irreversible mechanicalresponse of ductile materials makes generalized models of ductile cracking very difficult to develop. Therefore, research and testing of ductile fracture have taken a path leading to deformation-basedparameters such as crack tip opening displacement (CTOD) and crack tip opening angle (CTOA). Constrained by conventional test techniques and instrumentation, physical values (e.g. crack mouthopening displacement, CMOD, and CTOA angles) are measured on the test specimen exterior and asingle through-thickness "average" interior value is inferred. Because of three-dimensional issuessuch as crack curvature, constraint variation, and material inhomogeneity, inference of averageparameter values may introduce errors. The microtopography methodology described here measuresand maps three-dimensional fracture surfaces. The analyses of these data provide direct extraction ofthe parameters of interest at any location within the specimen interior, and at any desired increment ofcrack opening or extension. A single test specimen can provide all necessary information for theanalysis of a particular material and geometry combination.