Non-destructive test

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 non-destructive, as discussed in Section 12.1. Destructive testing generally involves placing samples of the production run in simulated or accelerated service and determining if it has properties similar to a specimen that is known to have a good bond and adequate service performance. The causes and remedies for a number of faults revealed by such mechanical tests are described in Table 12.1. Most of the destructive (mechanical) tests that can be carried out on adhesive bonds are listed in Section 12.2.1.1 (ASTM methods for mechanical properties). Non-destructive tests are far more economical, and every assembly can be tested, if desirable.  

Visual inspection. Visual inspection, with the help of a strong light, can be used to detect gross flaws and defects. Table 12.2 lists the characteristics of faulty joints that can be detected visually. The most difficult to detect by any means are those defects related to improper curing and surface treatments. For this reason, great care and control must be given to surface preparation procedures and shop cleanliness.  

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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. 

The basic condition of the Standard application - the availability of stable coupled probabilistic or the multiple probabilistic relations between then controlled quality indexes and magnetic characteristics of steel. All the probabilistic estimates, used in the Standard, are applied at confidence level not less than 0,95. General requirements to the means of control and procedure of its performance are also stipulated. Engineers of standard development endeavoured take into consideration the existed practice of technical control performance and test at the enterprises that is why the preparation of object control for the performance of nondestructive test can be done during the process of ordinary acceptance test. It is suggested that every enterprise is operated in correspondence with direct and non-destructive tests, obtained exactly at it, for detailed process chart and definite product type, however the tests have long since been performed after development of the Standard displayed that process gives way to unification. 

CEN TC 138 (Non-destructive Testing) WG 7 (Acoustic Emission) Draft for General Principals"... 

F. Cattaneo, C. De Michelis, S. Ghia, G.M.Piana "AEBIL a new acoustic emission system for on-line structural integrity monitoring of critical power plant components" to be presented at the 7th European Conference on Non-Destructive Testing, Copenhagen, 26-29 May 1998. 

Munns, G.A. Georgiou, Non-destructive testing methods for adhesively bonded joint nspection - a review, INSIGHT, Vol 37, No 12, Dec 1995, pp 941-952... 

Andrews, J. Blanchard, T. Stepinski, L. Ericsson, Ultrasonic spectroscopy for NDT, Presented at Int. Symp. Non-Destructive Testing in Civil Engineering (NDT-CE), Berlin, 1995... 

Through this study, we have shown that ultrasonic imagery can be an optimal solution to the different problems in Non Destructive Testing. This method, largely used, would have to be introduced in industry by an investment of the NDT users. This also requires a reorientation and supplementary operators trained in ultrasonic techniques. 

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