Nondestructive bonding mechanisms

Nondestructive testing (qv) can include any test that does not damage the plastic piece beyond its intended use, such as visual and, in some cases, mechanical tests. However, the term is normally used to describe x-ray, nuclear source, ultrasonics, atomic emission, as well as some optical and infrared techniques for polymers. Nondestructive testing is used to determine cracks, voids, inclusions, delamination, contamination, lack of cure, anisotropy, residual stresses, and defective bonds or welds in materials. 

The nondestructive photo-excitation of a molecule by light is controlled by several mechanisms related to the bonding and mass of individual elements of the molecule. These include rotation about a bond, vibrational between two ligands separated by a bond, and the vibration of the entire molecule. 

More recently, Finlayson et al. (66) performed deuterium tracer studies using 2,2,4,4-tetramethylpentane as a model reactant, and proved that the bond-shift isomerization to 2,2,5-trimethylhexane may go via a monoad-sorbed intermediate on Pd (as well as on Pt, Ir, and Rh). The authors show that in the mechanisms of nondestructive reactions such as cyclization and bond-shift isomerization of alkanes, only one metal atom is required as the catalytic center. 

The interfaces in bonded structures influence the mechanical behavior of components significantly. Therefore, an important task in nondestructive testing (NOT) is the investigation of the interaction forces in adhesive joints and the development of techniques to evaluate the bond quality. The load capacity of such joints is often limited by regions of weak bonding. As in all materials, the... 

After the adhesive is cured, the joint area can be inspected to detect gross flaws or defects. This inspection procedure can be either destructive or nondestructive in nature. Destructive testing generally involves placing samples of the production run in simulated or accelerated service and determining if it has similar properties to a specimen that is known to have a good bond and adequate service performance. The causes and remedies for faults revealed by such mechanical tests are described in Table 7.15. 

One problem, always present in the use of structural adhesives, is how to determine the reliability of the bonded structure. This may be at the time of manufacture, to ensure that a good joint has been produced, or during service, to monitor behavior under operating conditions. It is often impractical, or impossible, to use the types of test methods employed to determine mechanical properties and interest has centered on nondestructive test methods."" " ... 

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