Electronic Holographic NDE

The capabilities of holographic NDE to detect unbonded and de-laminated defects within bonded, laminated and composite structures has been previously demonstrated [1]. However, this NDE method has historically not been as readily accepted by industry as other NDE methods. This was primarily due to the relatively long time and high cost required per part inspected and the high level of expertise required of the operator. A holographic NDE method was developed [2,3] that significantly reduces the inspection time and the required level of operator expertise making this method both practical and cost effective for production applications. Recently, an electronic imaging system [4,5] has been incorporated to replace the photographic film process used previously. With this latest improvement, the current holographic NDE system offers several benefits over other NDE methods. Holography provides a large field of view which permits an area up to several square feet to be inspected with one hologram. The inspection rate is also extremely fast. Since the electronic system operates at 30 frames per second, the easily interpreted inspection results are viewed in real time. The method can detect “touching” unbonds and delaminations since, as will be discussed later, the bond line(s) are stressed as part of the inspection procedure. With the electronic imaging, a holographic inspection may be performed with very little involvement of an operator who may possess little actual knowledge of holography