Solid-Solid Bonding Characterization by Ultrasonic Reflectivity

The most common approach to model a weakened bond at a solid-solid interface has been to allow for a partial slip of the displacement at the interface. This concept is transformed into a specific set of boundary conditions which are then solved to obtain the plane-wave reflection and transmission coefficients or to determine the dispersion relation of the associated interface wave, if they exist. A key question in this approach is whether one allows for a partial slip in both displacement components or just the tangential. Initially, Murty [1–2] considered only the tangential slip to model the slip interface with the following boundary conditions: Normal stress is continuous; Shear stress is continuous; Normal displacement is continuous; and Shear stress is proportional to a tangential displacement slip

Ultrasonic Guided Waves for Lap Splice Joint Inspection in Aging Aircraft

The integrity and reliability of adhesive joints in structural applications has long been a critical issue. Failure of these bonds during service could be catastrophic. In particular, the aviation industry due to its progressively aging fleet calls for a reliable non-destructive testing technique to characterize the bond quality. Several NDE techniques were developed each with its own advantages and disadvantages. [1–2] Utilization of ultrasonic guided waves offer a reliable and time efficient method. [3] Following several laboratory studies this technique was tested on a service damaged aircraft at Sandia National Laboratories in Albuquerque, NM. A Double Spring Hopping Probe (DSHP) was developed and tested on this test bed. A protocol for the inspection of lap splices and tear strap was established. The concepts of utilization of wave structure in mode selection, angle and frequency tuning for optimal use of the Lamb type guided waves are addressed. Highlights of our recent work on aging aircraft inspection are presented in this paper. The work expands on our earlier presentations. [4

Validity of Different Models of Interfaces in Adhesion and Diffusion Bonded Joints

The need to characterise thin layers between thicker sections of material arises in several current NDE problems, for example the oxide layer between the adhesive and adherend in an adhesively bonded joint, and an interlayer of a different material in a diffusion bonded joint. Many workers have attempted to characterise these layers by ultrasonic reflection coefficient measurements

Lamb Wave Mode Selection for Increased Sensitivity ot Interfacial Weaknesses of Adhesive Bonds

Interface quality between layers in a layered structure is critical in fracture and fatigue analysis. A theoretical and quantitative solution to the problem from a NDE point of view would be desirable in both manufacturing and for in-service investigation of a variety of different structures. For example a great need exists to develop a reliable and efficient inspection program of adhesive bond delamination and interfacial weakness detection in aging aircraft noting that the bond degradation generally preceeds cracking in the aluminum skin, starting at the rivet holes

Adhesive Joint Evaluation Using Lamb Wave Modes with Appropriate Displacement, Stress, and Energy Distribution Profiles

One of the most elusive yet critical problem in adhesive joints characterization is that of ‘kissing bond’ wherein good contact exists among the adherend and the adhesive, however with no acceptable levels of adhesion. To date, the kissing bond is difficult to be detected reliably by any of the methods including conventional ultrasound and thermal waves. Kissing bond which is a manufacturing defect/anomaly will substantially compromise the load bearing capability of the adhesive joint by initiating adhesive failure (in contrast to cohesive failure wherein the failure occurs within the thickness of the adhesive layer instead of a failure at the interface). Attempts to develop methods of detection of kissing bonds have been unsuccessful to date

Columnariose: etiologia, sinais clínicos e envio de amostras para análise laboratorial.

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