DIC‐based J‐integral evaluation of laser repaired cracks with micro/nanomaterial addition

Abstract

Cracks generated by a wire electric discharge machining on compact tension specimens are first repaired by high powered laser beam with different weight fractions of nano‐WC added at the crack tip. Digital image correlation method combined with J‐integral theory is used to measure and calculate J‐integrals of the repaired specimens. Fracture properties of the repaired specimens are compared and studied. The residual stress of specimens after being repaired by laser was also studied to analyze the feasibility of J‐integral to evaluate the fracture properties of the repaired parts. It is found that the influence of residual stress can be neglected when calculating J‐integral in a certain region in case of when the residual stress is small. The J‐integral obtained by the digital image correlation measurement is accurate and can effectively evaluate repairing effects. The paper provides guidance for laser repaired cracks with nanomaterial addition and an effective method for the evaluation of repairing effect.

Ductile–Brittle Transition Temperature of Epoxy Asphalt Concrete of Steel Bridge Deck Pavement Based on Impact Toughness

“…Te J integral theory, based on the energy principle, can quantitatively describe the strength of the stress-strain feld generated when a body fractures. J integral theory is not only applicable to elastomers but also to elastoplastic with small deformations [19][20][21]. Te schematic diagram of the J integral is shown in Figure 2 and the J formula is shown in the following equation: where W: the strain energy density of the plate; T → : the vector of external forces acting on the integral loop Γ arc element ds; U → : the displacement vector on the loop Γ. Te relationship between the J integral and the deformation work, the boundary load or stress vector, and the displacement vector can also be expressed as follows [21]:…”