Crack Arresting Structure

Author:  Richard G Pettit, Hampton, VA
Source:  US Patent 5,842,317
Doc ID:  1998025
Year of Publication:  1998
Abstract:  
In a crack arresting structure the crack arresting feature is located in the transition from one thickness to another, or a region of increased thickness can be intentionally introduced for the purpose of inhibiting crack growth propagation. The crack arresting feature comprises two different structural configurations. These structures include a thickness transition region where a portion of the structure is plastically deformed at or immediately adjacent to the thickness transition region. Alternatively, an overhang is provided where an appendage to the thicker part extends back over the thinner part at a thickness transition region. A high strength fiber or wire, preferably of non-constant cross-section may be inserted into a gap underneath the overhang and held in place by crimping due to plastic deformation. Fiber or wire reinforced interface may be adhesively bonded into place prior to or in lieu of deformation or crimping. The plastic deformation is preferably accomplished by strip or localized coining of the part by feeding the part through rollers or by other means such as localized shot peening, or laser shock peening or other suitable methods which apply high local stresses and result in a local thickness reduction at or adjacent the thickness transition point (or on either or both sides thereof). This results in a local compressive residual stress region, which has been shown to impede or even turn crack growth.