Abstract: The method of caustics employs a laser for illuminating an extended crack in stock sheet metallic material. A shadow area image is generated which has geometrical parameters which may be measured and applied to the calculation of stress intensity factor (K.sub.I). The variation of the shadow shape in response to specimen loading provides signatures corresponding with the degree and direction of residual stresses in the material adjacent a hole formed in the material. By determining stress-intensity factors and stress-intensity distributions, a higher degree of quality control for sheet stock material becomes possible in addition to allowing the assembling of such material in directions that will best counteract anticipated destructive external forces.

Abstract: A method and apparatus therefor using the stress wave phenomenon for sizing and working a hole in a workpiece. A mandrel of the desired size, shape, and finish is "driven" into the hole by a stress wave to work the hole and impart thereto a desired shape, size, and finish. Electromagnetic means are used to generate the stress wave whose characteristics are such that it can be propagated through the mandrel and into the workpiece with a pulse energy level, rise rate, and duration sufficient to put the material in the walls of the hole into a condition of plastic flow so that a permanent deformation thereof conforming to the working area of the mandrel is achieved. A straight or a tapered hole can be worked or a straight hole can be converted into a tapered hole having the desired final shape, size, and finish. In a further embodiment, the mandrel used in the method can be the fastener for which the hole has been drilled.

Abstract: Coil means between an annular casing electrode and a core casing electrode providing contact for high amplitude current conduction and flexibility during magnetic and structural loading in achieving substantially greater operational life in use with stress wave tooling.

Abstract: Method for forming or deforming a metal workpiece by passing a stress wave through the metal workpiece sufficient to render it momentarily plastic. The apparatus is basically comprised of a stress wave focusing device or amplifier. In operation, a workpiece is placed in a die or shaping means. The stress wave amplifier is then arranged to direct or focus the stress wave to the metal workpiece. Next, a stress wave is generated and passed through the stress wave focusing device, imparting a momentary state of plasticity to the metal workpiece.

Abstract: A method and apparatus for monitoring an electrically actuated tool. The current flowing in the tool circuit is sampled and converted to an analog voltage signal that is proportional to the maximum stress level output of the tool. This converted signal may be displayed and recorded as desired. The converted analog voltage signal is compared with signals representing the current flow that will produce the highest and lowest acceptable stress levels delivered by the tool and a logic control signal is produced if the analog voltage signal is outside the acceptable range. The logic control signal is used to prevent recycling of the tool so that subsequent tool operation is not possible until corrective procedures are instituted. Further, the logic control signal may be used to activate audio and visual indicators. Moreover, the logic control signal can be used to introduce a load into the total circuit to modify the current delivered to the tool and therefore change its output.

Abstract: Method and apparatus for driving an interference-fit fastener by electromagnetically generating a stress wave, conditioning the stress wave, and passing the stress wave through the fastener, the stress wave is reflected from the remote free end of the fastener to impart a high velocity to the fastener relative to the surface of its receiving aperture to overcome the frictional forces existing there between and draw the interference fastener into the receiving aperture.