Fracture and Fatigue

In our research on fracture and fatigue our interest is in the development of constitutive equations describing the processes of material separation.  We have investigated in materials ranging from adhesives and composites to structural alloys as well as cortical bone.

Fracture

Creep - Fatigue Crack Growth

Our current research interest is in high temperature failure. In particular, we are interested in the mechanics of crack advance under creep - fatigue conditions. We currently consider such problems in the context of two distinctly different classes of nickel base super alloys. This work employs advanced cohesive zone models for material separation as well as disco-plastic strain gradient plasticity formulations.

Collaborators: Jamie Kruzic (Oregon State University), Vikas Tomar (Purdue University)

Quasi-Brittle Fracture

We have developed cohesive zone model approaches for the characterization of adhesives and composites. These approaches encompass experimental methods for the direct measurement of the traction-separation law of cohesive zone models, models in which the traction-separation law emerges as the outcome of crack bridging models, as well as viscoelastic cohesive zone models and models accounting for environmentally assisted degradation.

Ductile Fracture

In ductile fracture two energy dissipating mechanisms contribute to the crack growth resistance of a metallic structure. In particular we are interested in the experimental determination of the cohesive energy in ductile fracture. We can determine such quantities from the mechanical analysis of void growth processes coupled to stereophotogrammetrically measured data of void size on fracture surfaces.


Collaborator: O. Kolednik

Fatigue Crack Growth

In our research we have developed and employed cohesive zone models for the computational analysis of fatigue crack growth. In particular, we have focused on the development of cohesive zone models with incremental damage accumulation and degradation of the cohesive zone properties. With such models we can obtain detailed insight into transient fatigue crack growth processes as these occur at overloads and underloads, and in the interaction of fatigue cracks with e.g. interfaces.