Voids inspection

Inspection. After the final adhesive cure cycle, the bonded assembly is removed from the tool and inspected. The first and most cursory inspection is a simple visual check. Major problems such as crushed core and significantly mis-located details can be seen with the unaided eye. A lack of continuous adhesive squeeze-out ( flash or spew ) around the periphery of details can be indicative of insufficient adhesive and subsequent voids. 

The pulse-echo and resonance impedance techniques are capable of determining which layer contains a disbond, given an appropriate standard to compare against. Inspection standards are bond assemblies made to simulate specific areas of a part with disbonds purposefully placed in them. By comparing the signal response of a suspected void to that of a known disbond in the standard, the... 

If an assembly is destructively inspected, the verification film is used to identify potential problem areas for particular attention. These areas and others randomly selected are cross-sectioned to determine bondline thickness (Fig. 22), bond details are peeled apart to inspect for voids and honeycomb core bonds are... 

The nondestructive temperature differential test by infrared is used. In this method, heat is applied to a product and the surface is scanned to determine the amount of infrared radiation is emitted. Heat may be applied continuously from a controlled source, or the product may be heated prior to inspection. The rate at which radiant energy is diffused or transmitted to the surface reveals defects within the product. Delaminations, unbonds, and voids are detected in this manner. This test is particularly useful with RPs. 

This arrangement changes drastically after inspection of the etched sample. The deep large voids designate the areas of isotropic phase (see Fig. 9.1 phase (b)). It further highlights that the anisotropic well-crystallized graphene layers adhere strongly only in a thin rim around the fiber axis. The immediate interface is also quite reactive to... 

After curing, the cast is annealed by a gradual cooling procedure and inspected by x-rays for possible defects(such as voids) and then machined to conform to required dimensions. This type of cast propint is not "case-bonded to the walis of the rocket motor chamber and does not possess the added strength afforded by such bonding (Ref 2,pp 58-oO)(See also Ref l,pp 102-4 and Addnl Refs a,b c) ... 

In its ultimate form, AIDECS is intended to be an inspection device which will provide a high resolution, three-dimensional scan profile of an entire expl charge in an artillery shell. It is designed to perform a differential measurement which, with an appropriately small inspection volume element, will not only identify the presence of discontinuities in the expl (such as voids, cracks, annular rings, base separations and inclusions), but is also to provide data about their size, three-dimensional location and orientation... 

Other NDT Methods. Radiography (x-ray) inspection can be used to detect voids or discontinuities in the adhesive bond. This method is more expensive and requires more skilled experience than ultrasonic methods. The adhesive must contain some metal powder or other suitable filler to create enough contrast to make defects visible. This method is applicable to honeycomb sandwich structures as well as metal and nonmetal joints. 

Thermal transmission methods are relatively new techniques for adhesive inspection. Heat flow is determined by monitoring the surface temperature of a test piece a short time immediately after external heating or cooling has been applied. Subsurface anomalies alter the heat flow pattern and, thereby, affect the surface temperature. The surface temperature difference can be detected by thermometers, thermocouples, or heat-sensitive coatings. Liquid crystals applied to the joint can make voids visible if the substrate is heated. 

The gas leaving the heat recovery equipment contains the soot formed in the reactor and most of any ash present in the feedstock some of the ash is deposited in a void space in the bottom of the reactor from which it is removed during periodic inspection shutdowns. The gas passes to a quench vessel containing nozzles for multiple water-sprays which scrub most of the soot from the gas. Additional heat recovery can be accomplished downstream of the quench vessel by heat exchange of the quenched product gas with cold feed water. Any residual soot in the gas is removed in a scrubber column. The SGP product gas contains less than 5 ppmv soot. 

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