Issue << content << Confirmation of the Stress State of Metal Support Elements with Coercivity Method


DOI:

2015. . No. 2(68) - Jun 2015, pp. 11-15

Confirmation of the Stress State of Metal Support Elements with Coercivity Method

Yu. V. Shevchenko, V. G. Shtengel

Introduction. Among nondestructive inspectors there are issues about the reliability of results obtained by various methods of non-destructive testing and possibility to confirm them with other independent methods. Especially it is true of new methods. One of them is used to evaluate the stress state of steel structures by determining the metal coercivity.
Method. The method is based on correlation between metal magnetic properties (a coercive force) and its strength degradation level (microdamages initiation, progress and accumulation in a metal structure). We have in practice compared supposed quality distributions of local stresses of complex strained structural elements identified visually with the results of instrumental inspection with the coercivity method. At the same time we have inspected metal supports of hydraulic structure spillway chute that are subjected both to comprehensive static stresses from the chute weight and from a discharging water flow, and to dynamic stresses from the impact of this flow, especially during the flood.
Results. When external deformation of a structure is hardly detectable, a coercivity method makes it possible to reveal latent defects (such as overstress state of spillway chute columns elements) that can lead to propagation of destruction.
Valuation of local coercivity has enabled the distribution of the structural elements stress state to be quickly determined in field conditions without use of complex valuation techniques.
Conclusion. The results of instrumental inspection of columns’ metal elements and identification of overstressed metal areas has substantially agreed with the visually determined state of the metal. This confirms the reliability of results obtained by applying the coercivity method for revealing latent defects such as overstressed areas and/or elements of metal structures.
 
References
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