Non destructive inspection methods

The introduction of tight personal security procedures and visual or X-ray inspection of carry-on luggage at all domestic and international airports in 1972, resulted in almost complete elimination of skyjacking incidents in the USA. This situation has most likely interrupted or delayed the further development of automatic non-destructive inspection methods for expls in baggage at airline terminals... 

The non destructive inspection methods appropriate for detecting defects in bonded joints are briefly summarized below from (references 5.21 and 5.44). 

The use of the electric field has been proposed and demonstrated to perform very well in defining various other properties. For example, electrical measurements have been used to monitor the foaming process and polymerization of polymeric foams [74], while dielectric measurements have been used for measuring the density of polymer foams [75]. Brady et al. [76] developed electrically conductive polypyrrole-coated PUR foam. The conductance of the foam was found to change linearly with the compressive load applied single and repeated. For aluminum foams, Kim et al. [77] developed a set of mathematical relationships based on experimental data to obtain mechanical properties (elastic modulus, compressive strength, and densification strain), using electrical conductivity as a non-destructive inspection method. 

The publication of interstate Standard GOST 30415-96" Steel. Non-destructive inspection of mechanical properties and microstructure of metal products by magnetic method" - is the long-expected event for works laboratories and development engineers of non-destructive test means. 

It has developed a real time method to compare successive non-destructive inspections of the steam generator tubes in nuclear power plants. Each tube provides a safety barrier between the primary and secondary coolant circuits. Each steam generator contains several thousands of tubes whose structural integrity must be ensured through the lifetime of the plant, Therefore, Laborelec performs extensive nondestructive tests after each plant outage. 

A comprehensive program that includes predictive maintenance techniques to monitor and analyze critical machines, equipment, and systems in a typical plant. Techniques include vibration analysis, ultrasonics, thermography, tribology, process monitoring, visual inspection, and other non-destructive analysis methods. 

AS of this writing, 100% inspection by NAA of small arms primers in an actual production loading plant has not been implemented, nor is it contemplated in the near future. Technical problems exist related to coupling the present state-of-the-art nuclear components with the high production rates for the primers, namely, tens of units per sec per automatic loading line. The high intensity of the neutron source and the complexity of the detection system required detracts from the utility of the method in a plant environment where simplicity and safety of operation are of paramount importance. Nevertheless, the technical feasibility of the method has been demonstrated by the AMMRC study and future developments in nuclear activation hardware may ultimately make this non-destructive inspection for production primers more viable... 

Dingwall, P. F., and Mead, D. L. (1976), Non-destructive inspection and volume fraction determination of CFRP using an eddy current method, June 1976, Dept, of Defence, Report RAE-TR-76078. 

Degoeje MP, Wapenaar KED, Non-destructive inspection of carbon fiber reinforced plastics using eddy current methods. Composites, 23(3), 147-157, 1992. 

Application of appropriate non-destructive examination methods during manufacturing, including the use of European Network for Inspection Qualification (ENIQ)-based quahfied manufacturing examination methods to confirm the absence of structurally significant crack-like defects... 

Munns, I.J. and Georgiou, G.A., Non-destructive testing methods for adhesively bonded joint inspection — A review. Insight, 37, 941-952 (1995). 

The most commonly used methods for evaluation of adhesive bonds are mechanical tests such as tensile shear and peel tests that determine the weakest link in a bonded assembly. Although these tests are useful in the development and quality control of adhesives, they are destructive and cannot offer failure prediction for in-service components. Ultrasonic inspection is the most commonly used non-destructive test method and can accurately assess de bonding in single adhesive bonds, providing that the sensor is perpendicular to the defect plane. However, ultrasound has some limitations in... 

Qualification services for in-service inspection systems may be required to verify that a proposed non-destructive testing method, technique or procedure and associated equipment are adequate for their purpose and that the inspection personnel is able to perform the assigned inspection duties. Any organization providing qualification services should be independent from any commercial or operational consideration. If the qualification bodies are part of the operating organization, they should satisfy specific independence criteria equivalent to those laid down in the appropriate international standards (e.g. EN 45004 for a type B inspection body). 

Progress in mean of modelisation and inverse problem solving [1] let us hope to dispose soon of these tools for flaws 3D imaging in Non Destructive Control with eddy current sensors. This will achieve a real improvement of the actual methods, mainly based upon signature analysis. But the actual eddy current probes used for steam generators tubes inspection in nuclear industry do not produce the adequate measurements and/or are not modelisable. 

Like almost any other technique, thermoelectric power, does however also have some of its own limitations. For example, thermoelectric power is a contact method, which means that if hydrogen content needed to be measured on the exterior of a coated pipeline, the coating would need to removed, however in-line pig inspection would allow for in-situ inspection of the pipeline inner wall. In these limited cases, alternative complimentary techniques can be utilized. Low frequency impedance measurements can provide an alternative non-destructive, non-contact method of measuring hydrogen through an entire specimen thickness, dependent upon lift-off. 

To be able to estimate bond strength by a non-destructive method is extremely attractive, especially for quality control purposes. The possibility of using ultrasonics for this application has been recognised for a long time36 and efforts have been made to standardise a procedure for the inspection of such components as engine mountings. 

Therefore we propose here an alternative route to inspect the local dielectric and polarization properties using non-destructive and non-invasive methods based on scanning force microscopy (sfm). Simultaneously, these techniques offer a high resolution in real space being extended down to the atomic scale when inspecting ferroelectric systems under ultra-high... 

NIRS is a non-destructive method, thus, 100% inspection of batches is theoretically possible, allowing better control of product uniformity. NIR is also non-invasive, enabling subsequent evaluation of the same tablets by another method. Samples may be retained for further analysis by NIR or other methods. 

Additional protection will be afforded by improved methods of non-destructive in-service inspection to demonstrate the integrity of sodium vessels and pipework and to detect incipient defects so that they can be repaired before they grow to cause leaks. Ultrasonic methods for inspecting welds in austenitic steels, and transition welds between steels of different composition, have been improved and further improvement can be expected. Components will increasingly be designed to facilitate in-service inspection. 

Conventional structures, such as a bridge or a civil aircraft, are still commonly passive structures. These structures are designed to withstand the maximum expected loads, even in the presence of small cracks that may occur in service, due to corrosion, impacts with external objects or any other reason. The maximum crack size before catastrophic failure can be predicted, and the detectable crack size (of course, much smaller than the critical size), are defined according to the available non-destructive methods also the crack growth by dynamic loads can be predicted. Therefore, the time between inspections can be defined to avoid any incipient but undetected crack to become critical. This is the so called maintenance on schedule , and it has proven to be a very safe method - presently the percentage of aircraft accidents due to structural failure is very low. But the cost of these inspections is high, because they require sophisticated NDl and many labour hours. The cost of maintenance is about a quarter of the total life-cycle costs of an aircraft, similar to the fuel, crew, or acquisition costs. 

In assessing the suitability of the winder s drums for an increased load or for continued use, the type of construction as well as the presence of any stress-induced defects need to be taken into account. To this end, both visual examination and Non Destructive Testing (NDT), employing Magnetic Particle Inspection (MPI) methods are implemented. An experienced winder engineer will have a good idea of what to expect to find in a winder s drums that have seen many years of service and very often, the decision as to whether it will be economically... 

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